eps training

Course Outline

1. Data preparation workflow

using PanWizard.

2. Data preparation – large file.

3. Analysis methods and workflow.

Quick Match.

4. Faults and boundaries.

5. Dual porosity reservoir.

6. Closed reservoir.

7. Parallel faults.

Phase redistribuion.

8. Horizontal well.

9. Partial completion.

10. Radial composite reservoir.

11. Hydraulically fractured well.

12. Gas welltesting - flow-after-flow test.

13. Gas welltesting – isochronal test.

14. Advanced Simulation.

15. Test design.

16. Interference test design and analysis.

17. Reporting.

18. Slug test analysis

0. Gauge data – reservoir data

Edinburgh Petroleum Services PanSystem User Course

Gauge data Gauge data -- reservoir datareservoir data

2

1 2

1

2

162.6log log 3.2275 0.86859

162.6

log 3.2275 0.86859

1.1513 log 3.2275

i wf

t w

t hr i

t w

t hr i

t w

qB kp p t S

kh c r

qBm kh k

kh

kp p m S

c r

p p kS

m c r

S from intercept

at t =1 hr

kh from slope of line

Pressure Drawdown Theory for an Infinite

Acting Reservoir with an Altered Zone

Radial flow, homogeneous reservoir


To analyse the welltest we need accurate To analyse the welltest we need accurate

measurements of:measurements of:

–– TimeTime

–– FlowrateFlowrate

–– PressurePressure

–– Reservoir and fluid parametersReservoir and fluid parameters

–– (Temperature)(Temperature)

TimeTime

TimeTime

Taken for granted that this is errorTaken for granted that this is error--free (quartz free (quartz

gauge clocks)gauge clocks)

Surface rate changes (from testing report) must be Surface rate changes (from testing report) must be

synchronised with downhole gauge clocksynchronised with downhole gauge clock


FlowrateFlowrate

FlowrateFlowrate

Theory has been developed for Theory has been developed for sandfacesandface flowrateflowrate

We normally measure surface flowrateWe normally measure surface flowrate–– How accurate?How accurate?

–– Must convert to downhole* conditions (volume factors)Must convert to downhole* conditions (volume factors)

** ““DownholeDownhole”” means reservoir (not sandface) P and Tmeans reservoir (not sandface) P and T

Error in flowrate means error in analysisError in flowrate means error in analysis–– sometimes discrepancies between test analyses at different ratessometimes discrepancies between test analyses at different rates

owing to +/owing to +/-- measurement errors measurement errors

PressurePressure

PressurePressureCorrect reading requires accurate temperature and valid Correct reading requires accurate temperature and valid

calibrationcalibration

Theory has been developed for Theory has been developed for sandfacesandface pressurepressure

The gauge is rarely at the sandfaceThe gauge is rarely at the sandface

So we donSo we don’’t measure sandface pressure, we measure t measure sandface pressure, we measure

gauge depth pressuregauge depth pressure

Gauge position is very important Gauge position is very important –– make sure you know make sure you know

where it iswhere it is……....


P1

Gauge depthGauge depth

Gauge reading depends on Gauge reading depends on

pressure difference between pressure difference between

midmid--perfperf and gauge position:and gauge position:

–– Hydrostatic pressure gradientHydrostatic pressure gradient

–– Friction pressure gradient.Friction pressure gradient.

A second gauge can provide a A second gauge can provide a

useful insight.useful insight.

P2

Hydrostatic Hydrostatic pp

HydrostaticHydrostatic

–– need to know fluid density and angle of deviationneed to know fluid density and angle of deviation

–– single phase is relatively easysingle phase is relatively easy

–– multiphase is more difficultmultiphase is more difficult

–– Flowing: Flowing: –– use WellFlo, Prosper, etcuse WellFlo, Prosper, etc

–– ShutShut--in: in: –– problem of phase segregation, liquid fallback, problem of phase segregation, liquid fallback,

difficult to quantifydifficult to quantify

–– pp11 may change with time, even during the test. may change with time, even during the test.

(You might not even know this is happening!)(You might not even know this is happening!)


Hydrostatic Hydrostatic pp

Wellbore cleanWellbore clean--upup

–– pp11 changes during the DST, especially at the beginningchanges during the DST, especially at the beginning

–– important if comparing initial buildup p* with final p* to important if comparing initial buildup p* with final p* to

check for depletion check for depletion –– observed difference could be due observed difference could be due

to hydrostatic changeto hydrostatic change

Gas welltest at different flowratesGas welltest at different flowrates

–– different bhfp for each rate means different gas density different bhfp for each rate means different gas density

–– may or may not be importantmay or may not be important

–– condensate with different condensate with different bhfpbhfp’’ss below dew point will below dew point will

have different liquid fractionshave different liquid fractions

–– less of a problem (ie: ignored) for oil welltestsless of a problem (ie: ignored) for oil welltests

–– a second gauge can give a second gauge can give

useful information about useful information about

changes in fluid density at changes in fluid density at

the gauges:the gauges:

–– but gauge calibration but gauge calibration

errors make errors make PP1212 of semiof semi--

quantitative use only.quantitative use only.

P1

P12

fluid= ( P12 / z12) psi/ft

0.4335


FrictionFriction pp

FrictionFriction

–– will vary with flowratewill vary with flowrate

–– usually negligible unless long distances and usually negligible unless long distances and

high rates are involvedhigh rates are involved

–– check using WellFlo, Prosper, etc to see if it check using WellFlo, Prosper, etc to see if it

might be significantmight be significant

–– if significant and not corrected out, it will if significant and not corrected out, it will

appear in the analysis as an appear in the analysis as an increased skin increased skin

factorfactor (see Slide #2). This may appear as a (see Slide #2). This may appear as a

raterate--dependent skin (D) in a multidependent skin (D) in a multi--rate test.rate test.

IfIf pp11 can be assumed constantcan be assumed constant

–– the only problem is to estimate itthe only problem is to estimate it……..

IfIf pp11 is changing with timeis changing with time

–– the changes may all occur during the early the changes may all occur during the early

part of the test (eg: liquid fallback at the start part of the test (eg: liquid fallback at the start

of a shutof a shut--in) and can be considered as part of in) and can be considered as part of

the wellbore storage period.the wellbore storage period.

–– if they continue throughout the test, you have if they continue throughout the test, you have

a more serious problema more serious problem……....


Slopes and absolutesSlopes and absolutes

Analysis involving Analysis involving slopesslopes and and derivativesderivatives is not is not

affected by affected by pp11 as long as it is a constant shift.as long as it is a constant shift.

Analyses of Analyses of absolutesabsolutes (final shut(final shut--in pressure, in pressure,

extrapolated pressure, bhfp) should all be extrapolated pressure, bhfp) should all be

corrected to midcorrected to mid--perfperf and, eventually, to any and, eventually, to any

other reference datum depthother reference datum depth

If gauge depth is not known, specify in your If gauge depth is not known, specify in your

report that all pressures are at gauge depth.report that all pressures are at gauge depth.

The theoryThe theory

The radial flow equation on Slide #2 was derived from first The radial flow equation on Slide #2 was derived from first

principles by making several simplifying assumptions to arrive aprinciples by making several simplifying assumptions to arrive att

a workable equation with (pa workable equation with (pii--ppwfwf)) log log tt::

–– homogeneous reservoir, uniform thickness, fully homogeneous reservoir, uniform thickness, fully perfperf’’dd

–– tt greater than a certain minimum value for the greater than a certain minimum value for the ““semilogsemilog

approximationapproximation”” to be validto be valid

–– constant fluid properties (FVF, constant fluid properties (FVF, µµ,, ))

–– small, constant compressibility (Csmall, constant compressibility (Ctt))

Last two are satisfied by water, and heavy to medium oils.Last two are satisfied by water, and heavy to medium oils.

But not gas. Constant property approach must be used with a But not gas. Constant property approach must be used with a

pressure function pressure function –– ““real gas pseudoreal gas pseudo--pressurepressure””..

Volatile oils and condensates Volatile oils and condensates –– useuse ““multiphase pseudomultiphase pseudo--

pressurepressure””..


What Permeability?What Permeability?

Slope analysis in radial flow gives usSlope analysis in radial flow gives us

kh/kh/µµ (transmissibility):(transmissibility):

–– value of k derived depends on what you put in value of k derived depends on what you put in

for for µµ and and hh

–– gross hgross h gives gives gross kgross k,, net hnet h gives gives net knet k,, wrongwrong

hh givesgives wrong kwrong k

–– in a multiin a multi--layered reservoir you will usually get layered reservoir you will usually get

thicknessthickness--averagedaveraged

k = kjhj / hj

Stratified Reservoir

q

pepe

q1

q2

q3

pw

k1, h1

k2, h2

k3, h3

No reservoir communication1

n

total j jkh k h

htotal

P


Layered Systemq

pepe

q1

q2

q3

pw

k1, h1

k2, h2

k3, h3

Reservoir communication1

n

total j jkh k h

htotal

…depending on a number of factorsP

ExampleExample


Lower gauge

Upper gauge

Well shut in

1.71 psi 2.42 psi

2.04 psi

1.62 psi

Difference


Upper gauge

Lower gauge

Mid-perf

Diff P

Correction PWater

Oil

Gas

x

~9 psi

~16 psi

xa

Example 1

Page 1


EX 1.1Example 1Example 1-- Part IPart I

Data Preparation

WorkFlow

Using

PanWizardPanWizard

Part IPart I

EX 1.2OverviewOverview

• This example uses various features of the DATAPREP

section in PanSystem and focuses mainly on how to get

the data in an analysable stage

• PanWizard has been designed to simplify the input of

data necessary for analysis of a simple welltest

• This is a gas well example, incorporating an initial flow

initial build-up, a flow-after-flow (FAF) test and a final

build-up

Example 1

Page 2


EX 1.3PanWizard

• Starting a New file

-Click on Next >>

• Loading an available file

-Click on Load PAN file

EX 1.4Data PreparationData Preparation

Example 1

Page 3



Dry gas reservoirs

Use Condensate fluid type for

Wet gas reservoirs (Pres>Pdew)

Select Condensate fluid type

and Tick Multiphase option

for Gas condensate reservoirs

(Pres<Pdew)

Use Multiphase Pseudo-

Pressure Method when more

than one phase are moving

inside the reservoir.


Example 1

Page 4




Example 1

Page 5




Example 1

Page 6




Example 1

Page 7




• Click Calculate all button

• Click OK

• Click Quit in PanWizard Dialog Box

-keep all the entered data

• File - Save As … - Example01

Example 1

Page 1


EX 1.1Example 1Example 1-- Part IIPart II

Data Preparation

WorkFlow

Using

PanWizardPanWizard

Part IIPart II

EX 1.2OverviewOverview• Normally the gauge data are provided as electronic

files.

• There may be more than one gauge.

• Type of the gauge

-Gauge Accuracy

-Gauge Drift

-Gauge Resolution

-Gauge Histerices

Example 1

Page 2


EX 1.3PanWizard

• Load PAN file

-Example01

EX 1.4Data PreparationData Preparation• PanWizard - What next ?

Example 1

Page 3



• Click on Import… button and open Test1.dat file


Example 1

Page 4




Example 1

Page 5




• Click on Example button

Example 1

Page 6




Example 1

Page 7


EX 1.13Data PreparationData PreparationFor this example the test rates are as follows:

Time, hrs Rate, MMscf/d Comment

0.0 0.0 Setting the gauge

5.66 0.0 Start Cleaning-up

8.67 12.25 End Cleaning-up

11.73 0.0 End 1st PBU

18.85 3.95 End 1st Flow Period

26.31 6.60 End 2nd Flow Period

32.34 9.00 End 3rd Flow Period

37.77 12.11 End 4th Flow Period

61.56 0.0 End Final PBU


Example 1

Page 8




Click on the Quit

button and keep

all the data.

Example 1

Page 9



• Import Test2.tpr and

Test3.tpr

• Note that these files include

one gauge data which has

been split into two files.

• So append Test3.tpr to

Test2.tpr by ticking Append

to file option.

EX 1.18Data PreparationData PreparationShifting Gauge Data:

• Plot both pressure records, test1 and test2.

• Click on Shift button

Shifting data horizontally

by constant time value

Shifting data vertically by

constant signal value

Draw a box before using

the Shift button

Example 1

Page 10



The two data sets (Test1 and Test2) are

displaced in time.

• Shift Test2 pressure data

– Use Shift button

– Use Zoom to improve resolution

• When satisfied with shift...

– Make a note of Delta-t (at the bottom of the

screen)

– Click Difference button

• Use Shift and Difference until you get a good

time match

EX 1.20Data PreparationData PreparationRate Change definition buttons when more than one data file is

available:

TEST2 data file is chosen

to plot

TEST1 is the Master data

file

If we click on Plot button, the rate change buttons

are not active any more.

The Rate Change buttons are Active ONLY if the Master file is plotted

Example 1

Page 11


EX 1.21

There are three icons on the Dataprep tool bar

used for copying data:

• Copy & Paste Including Time (patch

section from another data file)

• Copy, Resample & Paste (patch column

from another data file)

• Resample column from one data file to

create a new column in another

• The Master file is always the destination

for copying

Data PreparationData Preparation

EX 1.22Data PreparationData Preparation• Copy & Paste Including Time (patch section from another data

file)

File 1 (Master data file) File 2

Time Pressure Time Pressure

1.0 4000 1.2 3999

1.5 3995 1.3 3997

. . . .

. . . .

. . . .

} {

File 1 (new)

Time Pressure

1.0 4000

1.2 3999

1.3 3997

1.5 3995

. .

. .

Example 1

Page 12


EX 1.23

• Copy, Resample & Paste (patch column from another data file)




1.0 4000 1.2 3999

1.25 4150 1.3 3997

1.5 3995 . .

. . . .

. . . .

} {

File 1 (new)

Time Pressure

1.0 4000

1.25 3998

1.5 3995

. .

. .




1.0 4000 0.9 4000

1.25 3998 1.3 3997

1.5 3995 1.7 3990

. . . .

. . . .

} {

File 1 (new)

Time Pressure 1 Pressure 2

1.0 4000 3999.25

1.25 3998 3996.62

1.5 3995 3993.50

. . .

. . .

• Resample column from one data file to create a new column in another

Example 1

Page 13


EX 1.25

END OF EXAMPLE 1


Example 2

Page 1


EX 2.1Example 2Example 2

Data Preparation:

Large Data Files

EX 2.2DataPrep OverviewDataPrep Overview• Import data file

• Delete data at start and end

• Confirm deletions

• Define flow periods

• Reduce number of data points of each test period

• Confirm reductions

• Define Well, Layer and Fluid Parameters

Example 2

Page 2


EX 2.3DataPrepDataPrep--ImportImport

• Start PanSystem: File - New

• Dataprep - Well and Reservoir Description

– Select Oil as reservoir fluid (Default)

• Config - Units

– Select OILFABS in Units System (Default)

• DataPrep - Gauge Data - Import

– Example02.tpr

– Review File format

EX 2.4View Gauge DataView Gauge Data

Example 2

Page 3


EX 2.5View Gauge DataView Gauge Data

PanSystem will specify the

columns automatically

The user should define each column

Should be used to import Date column.(Time column format must be (DATE)hh:mm:ss)

EX 2.6DataPrepDataPrep

• Note data column format /units:

• Column 1: Time in decimal hours

• Column 2: Pressure in psia

• Column 3: Temperature in oF.

• Click Import

• Data import should take a matter of seconds

• To plot the imported data highlight the dataset of interest

from the Data File/Column List

• Click on Add to List icon and then Plot

Example 2

Page 4


EX 2.7Viewing Imported DataViewing Imported Data

EX 2.8DataprepDataprep• Plot the pressure column only

• Delete data at start and end i.e. during running in and

pulling out


– Draw box around data at start and end of the test

and hit Delete toolbar icon

– Confirm deletion to minimise plotting time

– Check with the Number toolbar button.

– There should now be approximately 25,000 data

points remaining

– Save file as Example02.PAN

Example 2

Page 5


EX 2.9DataprepDataprep


• Comments on all flow periods

• Delete all points up to just before the

fourth Buildup

• Delete the data points at the end of the

test


• There will be around 8400 points

Example 2

Page 6




Define the flow periods:

• Zoom-in on the beginning of the last drawdown

• Select the ‘Nearest data point’ option and define the

beginning of the drawdown then Zoom-out

• Zoom-in on the beginning of the Buildup period and

use the ‘Exact point’ option to define the start of the

build-up (very noisy data)

• Enter the rate as 400 bbl/day then zoom-out

• Zoom-in on the end of the buildup period and use

the ‘Nearest data point’ option to define the end of

the buildup then zoom-out

Example 2

Page 7


EX 2.13Data ReductionData Reduction

Select:

– Whole test (no selection)

– Box

– Test period

– Click Data Reduction Button

Methods of Reduction

Signal column which will

be reduced

Name of new Reduced Data file.

PS does keep the original file just in case.

EX 2.14Data SmoothingData Smoothing

Data Smoothing• Select

– Whole test (no selection)

– Box

– Test period

– Click Data Smoothing Button

Determines the number of points

to be used for smoothing

Define how to select the points

Define how to weight each point

Example 2

Page 8


EX 2.15Data SmoothingData Smoothing

Select the data column that you

would like to smooth

Define the name of smoothed

output data column (default is

SM1 Pressure #2 )

PS does keep the original file just in case

EX 2.16Data ReductionData Reduction• Select the drawdown period on the ruler bar

• Click on ‘Data Reduction and Smoothing facility’

button and

– Reduce to 200 points per log cycle

– Smooth with 0.1 window span

– this should leave about 430 data points

• Select the final build-up on the ruler bar

– Reduce the build-up data again using 200 points per log cycle

– Smooth with 0.1 window span

– This should leave approximately 370 data points

• Highlight any extra erroneous points and delete by

clicking the trash icon and Confirm deletions

• Save file

Example 2

Page 9




• Go to Dataprep

- Well and Reservoir Description (Analytical)...

• Enter the following data in well, layer and fluid

parameters screens

– Rw = 0.35 ft.

– h = 87 ft.

– Ø = 0.17

– Bo = 1.12 resbbl/STB

– oil = 0.7 cp

– Ct = 5.2E-5 psi-1

• Click OK

• Save File

Example 2

Page 10


EX 2.19AnalysisAnalysis

• Select Analysis - Plot

• Select Build-up on the ruler bar

• Select Log/Log Plot icon

Note that in the early time region the

pressure and derivative data should

follow unit slope trend and overlay

each other. If not the BU start time

and pressure have not been defined

properly.

• Adjust T0 to find a ‘good’ value

• T0 = 78.186 Hours.

EX 2.20LogLog--Log PlotLog Plot

Example 2

Page 11



END OF EXAMPLE 2


Example 3

Example 3Example 3

Analysis Workflow

Rev 07-Nov-06

2

Analysis workflowAnalysis workflow

Three methods of analysis will be demonstrated

here:

line-fitting using the pressure derivative on the log-log plot

line-fitting to specialised diagnostic plots (Horner, square-

root, etc)

shape-matching using type-curves

All three approaches provide initial estimates of the

parameters

These are then refined using simulation

the theoretical response is matched to the measured data

by trial-and-error adjustment, or by auto-regression


Example 3

3

File: example 3_1.pan

This is a shut-in test in an oil producer

Review well, layer and fluid data

Review pressure data and the rate history

Note that there

were several

flowing periods

and shut-ins

before this test,

but no pressure

data were

measured until

the final shut-in


4

Data qualityData qualityWell shut in

Check that the instant of shut-in (T0, P0) has

been correctly picked

Inspect the data for noise,

shifts, unusual behaviour

Something happened here!

This section of data can be

deleted.

Pressure shift and

change of slope

T0

P0


Example 3

5

Analysis on the logAnalysis on the log--log plotlog plot

Enter Analysis, select the buildup test period in

the ruler bar, and go to the log-log plot

Adjust the derivative smoothing constant L

(under the T button)

PanSys plots P/ Q

on the y-axis, rather

than P, when there

is a multi-rate history

(‘rate normalised

pressure’)

The x-axis is the

Agarwal equivalent

drawdown time ( te), a

superposition function

The derivative is

computed as

P’ = P/ log( te)

6


Identify the probable flow regimes from the derivative

shape

Try PanWizard / Model

Selection

or the Derivative

Diagnostic Library

for guidance….

This looks like a Radial

homogeneous reservoir

with wellbore storage

The slight derivative upturn

at the end of the test suggests a possible remote heterogeneity….

Check Analysis / Model – the default models should be

appropriate

We will deal with the heterogeneity later….


Example 3

7


The wellbore storage period looks fairly well-shaped

Select the unit-slope line and fit the line to the

storage-dominated data on the left

If no unit-slope trend on pressure and derivative at the beginning,

adjust T0 and/or P0

Do this using the T0 button in the menu bar, or return to the Data

Edit Plot in DataPrep and adjust (or re-pick) the shut-in event

Note Cs and Cd appear in the results box

Select the zero-slope line and fit to the zero-slope

portion of the derivative to obtain k from the radial flow

regime.

Fit the radial flow ‘FR’ markers to this portion of the data

to get an estimate of the mechanical skin factor S

8



Example 3

9


Confirm results

Run Quick Match (under the

Simulate menu item)

The initial match should

be quite good, but can

be improved

Adjust Cs, k and S to

improve the match:

Cs shifts the unit-slope

portion of the derivative left

or right and affects the shape of the storage hump

k moves the radial flow portion of the derivative up or down

S moves the pressure up or down and affects the shape of

the storage hump

10


Delete the lines and flow regimes for a cleaner plot

Lines: right-click / {Del} key or

button

Regime: double-click in

coloured bar / Delete

Note how the computed

initial pressure Pi

changes as you adjust the

parameters

This is the theoretical

pressure at the start of the

rate history (first line of the

Rate Changes table)

For an infinite reservoir, this

is also the current reservoir pressure (no depletion)


Example 3

11


An estimate of the distance to the suspected

heterogeneity can be obtained using the radius of

investigation calculation:

Position the mouse pointer where the

derivative starts to deviate from radial

flow

Check the Rinv read-out in the status

bar

Rinv

So there is “something” at about

500 ft (150 m) from the well…..

tC

tk03.0

12

Analysis using specialised plotsAnalysis using specialised plots

Clear Quick Match

Right-click on the trace, and tick ‘Hide match: all plots’

Fit the ‘FR’ markers for radial flow again

Go to the Radial Flow

Plot (‘semi-log’ plot)

This is the Horner super-

position plot

A line is fitted automatic-

ally to the radial flow data

k from slope, S from

intercept

P* (extrapolated to t = )

is equivalent to Pi from

Quick Match

Radial flow

Horner Plot


Example 3

13


Semilog Plot Results Box:

k: Effective permeability

kh: Permeability-thickness product

Rinv: Radius of investigation

FE: Flow Efficiency

dpS: Skin pressure drop/recovery

S: Skin factor (mechanical)

P*: Extrapolated pressure

14


To refit a line:

Right-click on it and move/rotate it using the tabs that appear

Right-click on it, delete it with the button or the {Del} key and

then either:

Click in the flow regime band in the ruler bar and fit a line using

Define a range of data points by clicking once at each end, then fit a line

using

Click on the button and position the line using the tabs

Statistical details about a

selected line can be read

under the LR (Line Results)

button


Example 3

15


Since we have only radial flow, the Radial Flow Plot is the only

specialised plot that provides a

result from a line-fit in this example

Not strictly true! It is possible

to estimate the wellbore storage

coefficient Cs from the Cartesian

Plot (p vs t), since a unit slope

on the log-log plot derivative

implies that p t

A line through the first 3 or 4 data

points gives a value of Cs fairly

close to the one obtained from the

log-log plot

This line-fit is rarely used…..

16


Having obtained results from the specialised plots, or from a

combination of log-log and specialised plots, the procedure would

now be to confirm the results and to refine the match using

Quick Match

This can be done on any plot: the log-log plot with derivative is

the most useful, but the radial flow plot gives better resolution for

the pressure match to get S


Example 3

17

Analysis by typeAnalysis by type--curve matchingcurve matching

Clear Quick Match and go to the Type-Curve section

Click the button and

select the default Td/Cd

type-curves for Radial


with storage and skin

(Gringarten et al)

18


Match overall pressure and derivative shapes

Drag with the mouse, use the arrow keys for fine adjustment

Match vertically on the radial flow portion of the derivative k

Match laterally on the wellbore storage portion

CS

Click and accept (or change) the curve number S

Confirm results

Refine the match using Quick Match and review other plots


Example 3

19

The button allows the pressure or derivative curve-

sets or labels to be hidden


20

The button lets you fix the vertical placement of the

type-curves according to a specified permeability



Example 3

21

Match refinementMatch refinement

Return to the log-log plot and run Quick Match

We can tidy up the match to that derivative upturn at the end of the

test

There are a number of possible explanations. We will assume that

there is a fault there.

Analysis / Model – select single

fault as the boundary model

OK back to the plot

Now rerun Quick Match and

enter the distance estimated

from the radius of investigation

(500 ft / 150 m).

Adjust the distance to perfect the match

22


Final match to this dataset assuming a single fault

Note change in the model

has lead to a change in Pi

This new Pi can be

roughly reconciled

with P* from the

Horner Plot by fitting

a line to the very end

of the buildup

Radial Flow Plot


Example 3

23

Still on the log-log plot, click the time function button

The default Use full history invokes

the superposition time function (based

on the time and rate data in the Rate

Changes table) for:

Derivative computation

X-axis of most plots

It is theoretically rigorous and valid for most situations

Superposition theory is used so that tests which are not constant

rate drawdowns can be plotted in such a way that they look like

constant rate drawdowns. In this way, we can apply the same

line-fitting, derivative shape recognition, etc rules to all tests.

The derivative P’ = P/ log( te) where te is the Agarwal

equivalent time, a form of superposition function

Time function button Time function button TfTf

24

Use constant rate history simplifies

a multi-rate history to a single rate

using the last flowrate and an

effective producing time Tpeff

Tpeff = Total volume produced / last rate before shut-in

This equivalence was useful in the days before computers….

No history ignores the rate history: no superposition is used for

the derivative computation or plots

In all but a few situations, this is not recommended

Use Horner has no effect on the log-log plot



Example 3

25


No history – log-log plot without superposition

Derivative has different shape (compare previous log-log plot)

Model recognition using drawdown rules

is no longer so easy

But, since we have

already done an

analysis, note how the

simulated trace still

matches the data

If the model is correct, the two will always match, no matter how they are plotted…

180 md

26

Alternative Radial Flow Plot presentation – Agarwal Plot

This presentation

uses full history,

but ‘Horner’ is

switched off

The x-axis is ‘Equivalent time’ (Agarwal equivalent drawdown time),

an alternative form of superposition function

Pcalc is equivalent to Pi from the Horner plot

For a buildup, the Horner Plot is more commonly used


Radial flow


Example 3

27

Another Radial Flow Plot presentation – the MDH Plot

This presentation

uses no history,

and ‘Horner’ is

switched off

The x-axis is ‘Elapsed time’, no superposition is used

Note slight downturn from the straight line trend at the end

This is because superposition is not being used

Compare with log-log plot using No history


Radial flow

28

Tiled plotsTiled plots


Example 3

29

Derivative Diagnostic LibraryDerivative Diagnostic Library


Example 3

Example 3Example 3

Analysis Workflow

Rev 07-Nov-06

2


Three methods of analysis will be demonstrated

here:

line-fitting using the pressure derivative on the log-log plot

line-fitting to specialised diagnostic plots (Horner, square-

root, etc)

shape-matching using type-curves

All three approaches provide initial estimates of the

parameters

These are then refined using simulation

the theoretical response is matched to the measured data

by trial-and-error adjustment, or by auto-regression


Example 3

3




Review pressure data and the rate history

Note that there

were several

flowing periods

and shut-ins

before this test,

but no pressure

data were

measured until

the final shut-in


4

Data qualityData qualityWell shut in

Check that the instant of shut-in (T0, P0) has

been correctly picked

Inspect the data for noise,

shifts, unusual behaviour

Something happened here!

This section of data can be

deleted.

Pressure shift and

change of slope

T0

P0


Example 3

5


Enter Analysis, select the buildup test period in

the ruler bar, and go to the log-log plot

Adjust the derivative smoothing constant L


PanSys plots P/ Q

on the y-axis, rather

than P, when there

is a multi-rate history

(‘rate normalised

pressure’)

The x-axis is the

Agarwal equivalent

drawdown time ( te), a

superposition function

The derivative is

computed as

P’ = P/ log( te)

6



shape

Try PanWizard / Model

Selection

or the Derivative

Diagnostic Library

for guidance….

This looks like a Radial


with wellbore storage

The slight derivative upturn

at the end of the test suggests a possible remote heterogeneity….

Check Analysis / Model – the default models should be

appropriate

We will deal with the heterogeneity later….


Example 3

7


The wellbore storage period looks fairly well-shaped

Select the unit-slope line and fit the line to the

storage-dominated data on the left

If no unit-slope trend on pressure and derivative at the beginning,

adjust T0 and/or P0

Do this using the T0 button in the menu bar, or return to the Data

Edit Plot in DataPrep and adjust (or re-pick) the shut-in event

Note Cs and Cd appear in the results box

Select the zero-slope line and fit to the zero-slope

portion of the derivative to obtain k from the radial flow

regime.

Fit the radial flow ‘FR’ markers to this portion of the data

to get an estimate of the mechanical skin factor S

8



Example 3

9


Confirm results

Run Quick Match (under the

Simulate menu item)

The initial match should

be quite good, but can

be improved

Adjust Cs, k and S to

improve the match:

Cs shifts the unit-slope

portion of the derivative left

or right and affects the shape of the storage hump

k moves the radial flow portion of the derivative up or down

S moves the pressure up or down and affects the shape of

the storage hump

10


Delete the lines and flow regimes for a cleaner plot

Lines: right-click / {Del} key or

button

Regime: double-click in

coloured bar / Delete

Note how the computed

initial pressure Pi

changes as you adjust the

parameters

This is the theoretical

pressure at the start of the

rate history (first line of the

Rate Changes table)

For an infinite reservoir, this

is also the current reservoir pressure (no depletion)


Example 3

11


An estimate of the distance to the suspected

heterogeneity can be obtained using the radius of

investigation calculation:

Position the mouse pointer where the

derivative starts to deviate from radial

flow

Check the Rinv read-out in the status

bar

Rinv

So there is “something” at about

500 ft (150 m) from the well…..

tC

tk03.0

12


Clear Quick Match

Right-click on the trace, and tick ‘Hide match: all plots’

Fit the ‘FR’ markers for radial flow again

Go to the Radial Flow

Plot (‘semi-log’ plot)

This is the Horner super-

position plot

A line is fitted automatic-

ally to the radial flow data

k from slope, S from

intercept

P* (extrapolated to t = )

is equivalent to Pi from

Quick Match

Radial flow

Horner Plot


Example 3

13


Semilog Plot Results Box:

k: Effective permeability

kh: Permeability-thickness product

Rinv: Radius of investigation

FE: Flow Efficiency

dpS: Skin pressure drop/recovery

S: Skin factor (mechanical)

P*: Extrapolated pressure

14


To refit a line:

Right-click on it and move/rotate it using the tabs that appear

Right-click on it, delete it with the button or the {Del} key and

then either:

Click in the flow regime band in the ruler bar and fit a line using

Define a range of data points by clicking once at each end, then fit a line

using

Click on the button and position the line using the tabs

Statistical details about a

selected line can be read

under the LR (Line Results)

button


Example 3

15


Since we have only radial flow, the Radial Flow Plot is the only

specialised plot that provides a

result from a line-fit in this example

Not strictly true! It is possible

to estimate the wellbore storage

coefficient Cs from the Cartesian

Plot (p vs t), since a unit slope

on the log-log plot derivative

implies that p t

A line through the first 3 or 4 data

points gives a value of Cs fairly

close to the one obtained from the

log-log plot

This line-fit is rarely used…..

16


Having obtained results from the specialised plots, or from a

combination of log-log and specialised plots, the procedure would

now be to confirm the results and to refine the match using

Quick Match

This can be done on any plot: the log-log plot with derivative is

the most useful, but the radial flow plot gives better resolution for

the pressure match to get S


Example 3

17



Click the button and

select the default Td/Cd

type-curves for Radial


with storage and skin

(Gringarten et al)

18


Match overall pressure and derivative shapes

Drag with the mouse, use the arrow keys for fine adjustment

Match vertically on the radial flow portion of the derivative k

Match laterally on the wellbore storage portion

CS

Click and accept (or change) the curve number S

Confirm results

Refine the match using Quick Match and review other plots


Example 3

19

The button allows the pressure or derivative curve-

sets or labels to be hidden


20

The button lets you fix the vertical placement of the

type-curves according to a specified permeability



Example 3

21


Return to the log-log plot and run Quick Match

We can tidy up the match to that derivative upturn at the end of the

test

There are a number of possible explanations. We will assume that

there is a fault there.

Analysis / Model – select single

fault as the boundary model

OK back to the plot

Now rerun Quick Match and

enter the distance estimated

from the radius of investigation

(500 ft / 150 m).

Adjust the distance to perfect the match

22


Final match to this dataset assuming a single fault

Note change in the model

has lead to a change in Pi

This new Pi can be

roughly reconciled

with P* from the

Horner Plot by fitting

a line to the very end

of the buildup

Radial Flow Plot


Example 3

23

Still on the log-log plot, click the time function button

The default Use full history invokes

the superposition time function (based

on the time and rate data in the Rate

Changes table) for:

Derivative computation

X-axis of most plots

It is theoretically rigorous and valid for most situations

Superposition theory is used so that tests which are not constant

rate drawdowns can be plotted in such a way that they look like

constant rate drawdowns. In this way, we can apply the same

line-fitting, derivative shape recognition, etc rules to all tests.

The derivative P’ = P/ log( te) where te is the Agarwal

equivalent time, a form of superposition function


24

Use constant rate history simplifies

a multi-rate history to a single rate

using the last flowrate and an

effective producing time Tpeff

Tpeff = Total volume produced / last rate before shut-in

This equivalence was useful in the days before computers….

No history ignores the rate history: no superposition is used for

the derivative computation or plots

In all but a few situations, this is not recommended

Use Horner has no effect on the log-log plot



Example 3

25


No history – log-log plot without superposition

Derivative has different shape (compare previous log-log plot)

Model recognition using drawdown rules

is no longer so easy

But, since we have

already done an

analysis, note how the

simulated trace still

matches the data

If the model is correct, the two will always match, no matter how they are plotted…

180 md

26

Alternative Radial Flow Plot presentation – Agarwal Plot

This presentation

uses full history,

but ‘Horner’ is

switched off

The x-axis is ‘Equivalent time’ (Agarwal equivalent drawdown time),

an alternative form of superposition function

Pcalc is equivalent to Pi from the Horner plot

For a buildup, the Horner Plot is more commonly used


Radial flow


Example 3

27

Another Radial Flow Plot presentation – the MDH Plot

This presentation

uses no history,

and ‘Horner’ is

switched off

The x-axis is ‘Elapsed time’, no superposition is used

Note slight downturn from the straight line trend at the end

This is because superposition is not being used

Compare with log-log plot using No history


Radial flow

28

Tiled plotsTiled plots


Example 3

29


Example 4

Page 1


Example 4Example 4

Faults and Boundaries

Rev 07-Nov-06

2

Single noSingle no--flow boundaryflow boundary

A producing well at a distance L from a sealing fault (‘no-flow

boundary’):

The response is the same as if there were an identical producer a distance 2L away in an infinite reservoir

The mathematics is now straightforward – add the interference from the ‘image well’ (Ei-function) onto the response of the test well (semi-log function)

This results in an eventual doubling of the semi-log slope after the interference signal arrives, as the Ei-function becomes semi-logarithmic when Td/4Ld

2 > 25:2 wells pwf 2 log t

This is still a form of radial flow (“hemi-radial”)

q L

Test well

q qL L

Image wellTest well

Real no-flow boundary Virtual no-flow boundary

Example 4

Page 2


3

Intersecting noIntersecting no--flow boundariesflow boundaries

For 90° intersecting faults we need 3 image wells:

This will produce a quadrupling of slope when the 3 interferencesignals are superposed on the test well response

4 wells pwf 4 log t . This is still radial flow (“hemi-demi-radial”).

The general rule is that n = 360 °

The method of images can be used for some, but not all, integer values of n

Other methods can be used for other angles

L2

Test well

q

L1

q

L1

L2L2

L1

q

qq

4

For parallel faults we need image wells:

Each image has its own image in the other boundary ….ad infinitum

When these image interference signals are superposed on the test well response, the result is….. pwf t

This is linear flow - the derivative has a half-slope

For a closed channel (U-shaped), each of these images will have its own image in the end boundary

This is hemi-linear flow - the derivative still has a half-slope but is displaced upwards

Parallel noParallel no--flow boundariesflow boundaries

q

Test well

L1

L3

q

q

q

q

q

q

q

Example 4

Page 3


5

Dp

2/ DD Lt

.

.

.

.

4x (hemi-demi-radial)

0.1 1 10 100 1000

0.1

0.5

1

10

100

Elementary derivative responsesElementary derivative responses

2x (hemi-radial)

Half-slope (linear)Half-slope (hemi-linear)

Radial

These shapes are for boundaries which are equidistant from the well

For non-equidistant boundaries, the response will develop

one boundary at a time

6

ObjectivesObjectives

Identify model

Reservoir permeability k

True (mechanical) skin factor S

Boundaries present?

Boundary geometry

Boundary distances

Boundary types

Example 4

Page 4


7

Faults and boundariesFaults and boundaries


This is a flowing test in an oil producer


Review pressure data and rate history

Note that this pressure buildup is due to a

reduction in production rate, not a shut-in

8


Identify the probable flow regimes from the

derivative by trying different line slopes

This looks like a Radial homogeneous reservoir

with a boundary or other remote heterogeneity

Wellbore storage looks non-ideal

Check the T0, P0 pick on the Data Edit plot

Obtain k from the late radial flow regime. Confirm .

Fit the radial ‘FR’ markers to get an estimate of the

mechanical skin factor S

Example 4

Page 5


9


What might be causing the upturn in the

derivative?

10


The distance to the

heterogeneity can be

estimated using the radius

of investigation read-out in

the status bar beneath the

plot

Position the mouse pointer

where the derivative starts to

rise from the zero-slope line

This will be refined later by simulation

Select the single fault boundary model in

Analysis / ModelStart with the simplest model….

Example 4

Page 6


11


Run Quick match and

adjust the distance L1

Adjust Cs to match the

latter part of the wbs

Check the final match

on all plots

12


Log-log plot - clear Quick Match. Fit the ‘FR’ markers for

radial flow and single fault (hemi-)radial flow

Go to the Radial Flow Plot

to obtain k, S, PCalc and L1

L1 is computed fromthe time of intersection (Tx) of the two lines

It will not be very goodbecause the second radial flow regime didnot develop fully

PCalc is equivalent to P* on a Horner Plot

Confirm results , refine

match using Quick Match

Check the final match on all plots

Single fault

radial flow

(almost!)

Radial flow

Tx

Example 4

Page 7


13


Clear Quick Match and go to the Type-Curve

section

Select the default Td/Cd (Gringarten et al) type-curves

Match the pressure

and derivative

Use the arrow

keys for fine

adjustment

Matching in the x-

direction is difficult

owing to the shape

of the wbs period…

Click and

Confirm results

14


Click the right arrow button to move to the next

matching stage (a subset of boundaries)

Move the curves sideways – the vertical position is locked to

respect the permeability

X-axis of these curves

is Td/Ld2

Ld = L/rw

So sideways match gives L

Confirm results

Refine the match using

Quick Match

Example 4

Page 8


15



This is a long shut-in test in an oil producer



16


Identify the possible flow regimes from the derivative

Possible radial flow immediately after wellbore storage?

…and possibly not…..

Two other radial flow portions (CHECK NEXT SLIDE…)

Derivative approximately doubles from one regime to the next

Possibly a Radial homogeneous reservoir

with perpendicular boundaries, one closer than the other?

select this model in Analysis / Model

Wellbore storage looks fairly ideal

Storage could be partially masking the initial radial flow regime

If we fit a zero-slope line at the bottom of the derivative trough, we will get a lower limit to k

Fit the radial ‘FR’ marker to get an estimate of the mechanical skin

factor S

Confirm results

Example 4

Page 9


17


If you are plotting Equivalent time on the x-axis, you will

not see a radial flow regime at the end…..

It looks more like

linear flow

This is an artefact

of the compression

that occurs with

Equivalent time

when shut-in time

>> Tp

Try the ‘Plot against

elapsed time’ option


to remove this

compression

18

Radial flow (second fault)

Radial flow (first fault)

Radial flow

(partially obscured)

Wellbore storage


If we assume initially that radial flow is at the derivative minimum,

then k 42 md

There are two other well-developed zero-slope regimes (radial flow)

with approx doubling of values

So we may have:

Radial flow (partiallyobscured by storage)

‘Hemi-radial’ flow from first fault

‘Hemi-demi’-radialflow from second(perpendicular)fault

89

176

57

Example 4

Page 10


19


We can be smarter here:

if the second radial flow is caused by a fault, then the first radial flow

line should be at 89 2 = 44.5

Reposition this line and get

k 52 md

Confirm results

The approximate distance

to each boundary can be

got from the radius of investigation:

Place the mouse pointer where the derivative starts to rise from the radial

flow line….

…approx 55 ft (17 m) and 470 ft (143 m)

89

176

44.5

20


Run Quick Match (select ‘Variable well position’)

Enter the boundary distances

The initial match should be quite close

Adjust the parameters

to perfect the match

This is a good case for

Auto Match…

Example 4

Page 11


21


Set Cs=0 to appreciate how the initial radial flow regime has been

obscured:

For radial flow to develop clearly, the first boundarywould have to be more than about 50 ft (50 m) away

Downhole shut-ins reduceCs to a minimum and maximise the chances ofseeing the radial flowregime. But if the fault is still too close…..

Set Cs=0.023 bbls/psi (10 times as big) to see the effect

of a surface shut-in…..

22


Log-log plot - clear Quick Match. Fit the ‘FR’ markers for Radial

flow and Intersecting fault radial flow

Go to the Radial Flow (Horner) plot

First radial flow line gives k and S

Second radial flow line gives distance L to the two faults, assuming them to be equidistant (not very useful!)

There is no estimate of distance to the first fault

P* is good (well-developedradial flow regime)

Refine the match with Quick Match or Auto Match

Radial flow

Intersecting fault

radial flow

Example 4

Page 12


23



Select the default Td/Cd (Gringarten et al) type-curves

Match the pressure

and derivative

Use the arrow keys for fine

adjustment

Curve 5 is a good match to

the wbs-dominated data, if

we assume radial flow

at the bottom of the

derivative trough

Click the M button again

Confirm results

24


Click the right-arrow button to move to the next

matching stage (a subset of boundary type-curves)

Move the curves sideways – the vertical position is locked to

respect the permeability

X-axis of these curves

is Td/Ld2

Ld = L/rw

So sideways match gives L

Match to the first fault

Radial flow portion of type-

curve lies above the data

Wrong k !

Click to close the

match

Example 4

Page 13


25


Click the left-arrow button twice to return to the start,

click and select the Td/Cd type-curves again

Rematch the pressure

and derivative

Curve # 6 is a good

match if we do not

assume radial flow

at the bottom of the

trough

Click and confirm

results

26


Click the right arrow button to move to the boundary

matching stage:

Move the curves sideways

Match to the first fault

Hemi-radial flow portion

of the type-curve now fits

the data more closely

L 42 ft (13 m)

Example 4

Page 14


27


Move the curves sideways

and match to the second

fault

Click the button again

L 395 ft (120 m)

Run Quick Match and

input the values for L1

and L2

Refine the match manually

or using Auto Match

28

Fang

Wang

(fraction

of Fang)

Lint

IBDY2=1 (no-flow)

IBDY1=1 (no-flow)

Alternative Alternative ‘‘General intersecting faultsGeneral intersecting faults’’

modelmodel

Enter Analysis / Model and open a new interpretation

Select the General intersecting fault flow model

Set the Boundary model to Infinite acting

Run Quick Match, and adjust the parameters

to obtain a match

Example 4

Page 15


29






30



Note well-developed half-slope linear flow?

Possibly a Radial homogeneous reservoir

with parallel boundaries? select this model in Analysis /

Model

Wellbore storage looks non-ideal

Check the T0, P0 pick on the Data Edit plot…

If we fit a zero-slope line at the bottom of the derivative trough, we

will get a lower limit to k

Fit the radial ‘FR’ marker to get an estimate of the mechanical skin

factor S

Fit a half-slope line to get the channel width W

Confirm results

Example 4

Page 16


31


Assume radial flow is at the derivative minimum

There is a well-developed half-slope linear flow

32


Run Quick Match, select ‘Central well position’

and adjust the distance L

Reduce Cs to keep it out of the way for the time-

being

Even with L1 L3,

the match to the

linear flow portion

is not quite right

Select the ‘U-shaped’

boundary model and

try again…..

Example 4

Page 17


33


Adjust the distances L1, L2 and L3 to obtain a

match

Adjust by trial and error

Try Auto Match

Fix k

Fix Cs=0 and do not include anywellbore storagepoints

This model does

a slightly better

job…

34


For the wellbore storage either:

Leave Cs = 0

Bring in a small Cs to match just the end of the wbs-dominated

derivative

Select the a Varying

wellbore storage

model and attempt

a match

This match was obtained with the Hegeman model

Example 4

Page 18


35

Check the match on

other plots….

Approx radial flow

Linear flow

Linear flow plot

Radial flow plot

36


Log-log plot - clear Quick Match. Fit the ‘FR’ markers

for radial and hemi-linear flow

Go to the Radial

Flow Plot to obtain k

and S

Note P* is much too low

This is because the last

observed flow regime was

linear, not radial, so the

semi-log plot is the wrong

one to use for P*

Confirm resultsRadial flow plot

Example 4

Page 19


37


Go to the Radial Flow Plot to obtain channel width W

from the slope of the line

Note P* is close to Pi

from Quick Match

The last observed flow

regime was linear,

so the square-root plot

is the one to use for P*

For the ‘parallel fault’

model, this line-fit also

gives the convergence

skin Sconv

Confirm results

Run Quick Match to

refine the results manually, or use Auto Match

Linear flow plot

38

Two special casesTwo special cases

Non-sealing faultFault of finite extent

Example 4

Page 20


39

Non-sealing fault‘Partially sealing fault’ model

Fault of finite extentNumerical modelling

SealingInfinite length

Finite length

Highly conductive

Conductive

See file Example 4_Odd faults.pan

Two special casesTwo special cases

40

Partially sealing fault modelPartially sealing fault model

h2: The layer thickness on the far side of the fault

The layer thickness (h) specified in the Layer Parameters dialog is on the well side of the fault.

L1: The distance from the well to the fault.

Fc: The conductivity of the partially sealing fault:

Fc = Permeability of fault zone ÷ width of fault zone.

Plan viewh2

h

Side view

L1

Example 4

Page 21


41

Fault of finite lengthFault of finite length

Advance of pressure disturbance around the fault – numerical

modelling with PanMesh

42


Example 4

Page 22


43


44


Example 4

Page 23


45



Example 5


Dual Porosity Reservoir

EX 5.2DATAPREPDATAPREP

• Load file Example05.PAN

• This is a Pre-prepared pan file

• Before going on to Analysis

• Review Dataprep sections

– Make sure all the required information (Well, Layer

and Fluid parameters) has been defined properly.


Example 5

EX 5.3DATAPREPDATAPREPThis is an actual constant rate drawdown (CRD) test

for a vertical oil well.

EX 5.4ANALYSISANALYSISANALYSIS-PLOT

– Select the drawdown test period and go to Log-Log plot:

• Do you recognise the character of the Log-Log

derivative diagnostic plot ?

• Note: only allowed deltaT (elapsed time) as time

function on the x-axis

• Select the appropriate analysis model (Dual-Porosity

(Pseudo Steady State))

• Define the following flow regimes:

– Wellbore storage

– Transition to system radial flow

– System radial flow

• Confirm results


Example 5

EX 5.5ANALYSISANALYSIS

Dual Porosity Behaviour

(Transition to system radial flow)

Total System

Radial Flow

Wellbore Storage effect

EX 5.6Semi-Log Plot:

• Does it look just what you expect from having seen on the

Log-Log derivative ?

• If there is any fracture radial flow, the trend should be

parallel to system radial flow so use parallel line button and

add a parallel line.

• A value for should be calculated as is a function of the

vertical distance between these two parallel lines.

• Select the “Transition to system radial flow” flow regime

and add the best fit line.

• A value for should be calculated as it is a function of the

trend of the transition zone.

• Confirm Results

ANALYSISANALYSIS


Example 5

EX 5.7ANALYSISANALYSIS

EX 5.8ANALYSISANALYSISDual Porosity Parameters:

: Fracture Storativity, it represents the fracture

volume compared with total volume. Smaller

means smaller fracture volume or more matrix

volume so deeper V shape behaviour on the log-

log plot.

: Interporosity flow coefficient, it represents the

flow between the matrix and fracture. Higher

means sooner and better matrix support

therefore on the log-log plot it does move the V

shape to the left hand side.


Example 5

EX 5.9ANALYSISANALYSISOnce you have got all parameters…

• Select Log-Log plot

• SIMULATE-QUICK MATCH

• Fine tune the analysis parameters to get the final match

• Check Semi-log, Cartesian, and test overview match

• We are getting the fracture’s permeability-thickness product not the fracture permeability as it is not relevant.

• The skin factor represents the intersection of the fracture network and the wellbore.

EX 5.10ANALYSISANALYSISFinal results and match:


Example 5

EX 5.11TYPE CURVESTYPE CURVES• Use TC button to start type curve analysis

• Use Type curve match button

• 1st Stage

– Chose Derivative Match/Dual Porosity (PSS flow)

– Get k, ,

EX 5.12TYPE CURVESTYPE CURVES

Red parameters

are not calculated

by TC matching.


Example 5

EX 5.13

2nd Stage :

Use Next stage of type curve matching button to

calculate Cs and S

• Confirm results

• SIMULATE-QUICK MATCH to combine the type curves and

fine tune the parameters

TYPE CURVESTYPE CURVES


END OF EXAMPLE 5

Example 6

Page 1



Closed Reservoirs

EX 6.2

• Load file Example06.PAN

• This is a Pre-prepared pan file

• Before going on to Analysis

• Review Dataprep sections

– Make sure all the required information (Well, Layer

and Fluid parameters) has been defined properly.

DATAPREPDATAPREP

Example 6

Page 2


EX 6.3DATAPREPDATAPREP• This is an actual Extended (Reservoir Limit) test for

a vertical oil well.

• The main objective of an extended test is to get the

distances to all boundaries and calculate the amount

of hydrocarbon connected to a particular well.

• The main criteria of this type of tests is to reach

Semi-Steady-State behaviour during which the

flowing pressure is a linear function of time.


Semi-Steady-State behaviour

Example 6

Page 3



• On the log-log diagnostic plot, the late time

characteristics of SSS is Unit Slope trend on the

derivative.

• Set the model to Closed System

• Analysis Model Boundary Model

• Define all appropriate flow regimes

• Wellbore storage (not enough points)

• Radial Flow

• Closed System PSS flow

• Confirm results


Radial Flow

(Middle Time Region)

PSS Unit Slope Trend

(Late Time Region)

Example 6

Page 4



• As usual go to Semi-log plot and confirm the

results (K, S, etc...)

• On the Cartesian plot, the best fit line through

the late time region will provide the Area,

Volume, and Dietz shape factor.

• The area/volume is a function of the line slope

and Dietz shape factor is a function of area and

the line’s intercept.

• Confirm results


Best fit line through

PSS flow regime

Example 6

Page 5


EX 6.9Closed ReservoirClosed Reservoir

• Use SIMULATE-QUICK MATCH to fine tune

the analysis parameters.

– Wellbore Storage, Cs = 0.009 bbl/psi

– Permeability, k = 7.6 mD

– Skin, S = 6.25

– Distance to Boundary, L = 1300 ft

– Initial Pressure, Pi = 4412 psia

– Dietz shape factor, Ca = 31.6

– Drainage area = 153 acres

• Save the file


END OF EXAMPLE 6

Example 7

Page 1


EX 7.1

Parallel Faults

and

Phase Redistribution Effect

Example 7


• Load file Example07.pan

• Review Well, Layer, and Fluid

parameters

• Review the gauge data in Dataprep

• Check the Rate changes table

• This is a constant rate PBU test for a

vertical oil well.

Example 7

Page 2


EX 7.3AnalysisAnalysis• Select the BU test period and start with the

log-log plot.

• Examine the shape of the derivative

• Select T’ button

– plot linear derivative with smoothing factor of 0.2(smoothing factor determines the window in which the data points will be used for derivative calculation.)

• Note late time linear flow:

–Radial derivative is following half slope trend

–Linear derivative is following zero slope line trend

• Remove Linear derivative


Half slope trend on radial

derivative, an indication of

parallel faults or channel

Zero slope trend on linear

derivative, confirming linear

flow in a channel

Example 7

Page 3


EX 7.5

There are three possible reservoir / boundary models

to analyse this test:

• Variable wellbore storage effect (phase redistribution),

radial homogeneous with parallel faults equidistant

• Dual porosity with parallel faults equidistant, follow the

same procedure as in Example05.

• A no-flow boundary very close to the wellbore followed by

single fault radial flow and finally another no-flow

boundary parallel to the first one, follow the same

procedure as in Example04.

AnalysisAnalysis


• Select Analysis / Model

– Select Fair wellbore storage

– Change the reservoir model to Radial

homogeneous

– Change the boundary model to Parallel faults

• Select FR on the toolbar and mark the different

flow regimes

• Wellbore storage is not clearly seen on this test, so

the first point will give the maximum Cs value.

Example 7

Page 4


EX 7.7LogLog--Log PlotLog Plot

Variable wellbore

storage effcet

Middle time region,

infinite acting

radial flow

Late time region,

linear flow in a

channel

EX 7.8• Select Semi-log plot, confirm the permeability, skin

factor, etc...

• Make note of the extrapolated pressure value

• Select the Linear flow plot (square root of time)

• Confirm all results on this analysis plot

• Make note of the extrapolated pressure

– How do you compare this pressure value with the one

from semi-log plot ?

– Which one is more reliable ? Why ?

• Confirm Results

AnalysisAnalysis

Example 7

Page 5


EX 7.9Linear Flow PlotLinear Flow Plot

EX 7.10Linear Flow PlotLinear Flow PlotLinear Flow Plot Results:

W: Channel width, ft

L1: Distance to the first no-flow boundary, ft

Sconv: Convergence skin

P*: Extrap. Press. from linear flow plot, psia

A

B

C

In order to produce oil particles A and C compared with oil particle B more

pressure drop is required. This extra pressure drop is called convergence skin.

Example 7

Page 6


EX 7.11Variable WBSVariable WBSThe variable wellbore storage parameters are as follows:

• Wellbore Storage coefficient (Cs) is the final value when phase redistribution effects

have dissipated.

• Storage Amplitude (Cphi) is the maximum phase redistribution pressure change. It

can be positive (= increasing wellbore storage - e.g. "humping" caused by rising gas

in an oil well when it is shut-in.) or negative (decreasing wellbore storage - e.g.

compression of wellbore fluids).

• Storage Time Constant (Tau) is the time required for 63% of the total change to

occur.

• The easiest way of getting these parameters is by doing Quick Match (refer to Fair’s

paper)


• Return to Log-Log plot

• Perform Simulate / Quick Match, Use:

– Central well position (L:L) option

– Cphi = 300 psi

– Tau = 0.06 hr

• Adjust values to obtain best match

• Review Semi-log and Cartesian plots

Example 7

Page 7




END OF EXAMPLE 7

Example 8

Page 1



Horizontal Well

Oil Reservoir


• Select File Open - Example08.pan

• Select Dataprep - Gauge data & plot rate and

pressure

• Review Well, Layer and Fluid parameters

• This is a constant rate drawdown test of a

horizontal well in an oil reservoir.

Example 8

Page 2


EX 8.3AnalysisAnalysis• Select Analysis - Plot

– Test Overview

– Select the darwdown test period for analysis

– Log - Log plot

• Select model: Two no flow boundaries-homogeneous

• Select FR and identify flow regimes

– Wellbore storage

– Vertical Radial Flow

– Linear Flow through Reservoir

– Late Time Radial Flow

• Confirm results


Vertical

Radial flow

Linear flow

through

reservoir

Late time

Radial flow

Example 8

Page 3



Vetical Radial flow

• Is a function of:

Horizontal permeability

Vertical permeability

Provides the average permeability, kbar

Top boundary

Bottom boundary

EX 8.6

Linear flow through reservoir



Effective horizontal length

Provides the effective horizontal length if the

horizontal permeability is know.

AnalysisAnalysis

Example 8

Page 4


EX 8.7

Late time Radial flow/Pseudo-Radial flow



Effective net thickness

Provides the thickness-permeability product and

therefore the horizontal permeability.

AnalysisAnalysis


Semi log plot:

• Examine 1st (vertical) radial flow

• Examine 2nd (horizontal) radial flow

• Note:

– 1st line gives average permeability

– 2nd line gives horizontal permeability,

& by inference vertical permeability.

• Select each line and use LR button to view

further line results

• Confirm Results

Example 8

Page 5



Vertical radial

flow best fit line

Pseudo-Radial

flow best fit line

EX 8.10AnalysisAnalysisLinear plot:

• Examine linear flow period line

• Confirm Results

Log-Log plot:

• Select Simulate - Quick Match

– Fine tune the parameters to get the best match

– Review Cartesian, Semilog , Linear flow plots

– Tile

Example 8

Page 6




Type Curve Matching:

• Click on “TC”

• Click on “M”

Fixed Well Length:

The user should

define the well length

and use type curve to

get the well position

with respect to the top

boundary.

Unknown Well Length:

The user should define the

well position and use type

curve to get the well length.

Use unknown well length for this example, well position is 0.5

Example 8

Page 7



• Choose curve no. 8

• Go to the next stage of TC to get WBS and S

• Confirm results

• Do QM to fine tune the parameters

EX 8.14ResultsResults

• Cs = 0.0015 bbl/psi

• K = 1.08 md

• Kz = 0.95 md

• S = 0

• Zwd = 0.5

• Lw = 1000 ft

• Pi = 5000 psia

Final Analysis Parameters:

Example 8

Page 8



END OF EXAMPLE 8

Example 9

Edinburgh Petroleum Services PanSystem User

Course

Page 1

Example 9Example 9

Partial Penetration

Rev 0 1-Nov-06

2

Partial penetration modelPartial penetration model

hp

htop

h

Example 9


Course

Page 2

3

Radial flow in full thickness

khp

S = true skin factor

kh

Spr= pseudo-radial

skin factor

Radial flow at perforations

Partial penetration modelPartial penetration model

4


Identify model

Reservoir permeability k

True (mechanical) skin factor S

Effective open interval hp

Position of open interval htop

Vertical permeability kz

Effective skin factor Spr

Well productivity

Example 9


Course

Page 3

5

Partial PenetrationPartial Penetration


This is buildup test in an oil producer



The well was perforated over 200 ft of the 382 ft

formation thickness

Top of perfs was 80 ft from the formation top

6



derivative

Select the Partial penetration model

Obtain k from the late radial flow regime. Confirm.


pseudo-radial skin factor Spr

Fit a line to the (approx) ‘radial flow at perforations’ portion

(enter nominal hp at the prompt). Note ‘kp’.

Fit the ‘FR’ markers this regime to get an estimate

of the true skin factor S. Confirm.

Note S << Spr

Example 9


Course

Page 4

7

W ellbore storage looks very non-ideal… .

Spherical flow did not develop fully

A very rough estimate of kz can be obtained by marking the transition period with the ‘Spherical flow’ FR marker and going to the spherical flow plot.

Alternatively, get it by trial and error with Quick Match


8

Run Quick Match

Clear the lines and ‘FR’ markers (optional)

Refine the match (manually or with Auto Match)

The wellbore storage cannot be matched, even with a varying wbs

model –best to ignore

it !

Note hp is close

to the design

perforated

interval length

Check the

match on all

plots


Example 9


Course

Page 5

9

DeliverabiltyDeliverabilty

Select ‘Deliver’ –‘IPR’

Your k and a

computed value

of Spr will be displayed

Enter the estimated

layer pressure and a

bubble point pressure

Use default A and CA

Calculate

Compare with the

productivity index

calculated from the

production rate and final

measured flowing pressure

10


Clear Quick Match. Refit the ‘FR’ markers

Go to the Semi-log (Horner) Plot to obtain k, S, kp, Spr

and p*

ConfirmRadial flow at

perforations

Radial flow in

full thickness

Example 9


Course

Page 6

11

Fit a line to the (quasi-)spherical flow portion on the

reciprocal square-root plot to obtain kz from the slope

Confirm


12

Run Quick Match to refine the results manually, or use

Auto Match



Example 9


Course

Page 7

13



Select the default Partial Penetration type-curves

Match the

derivative

Use the arrowkeys for fineadjustment

Confirm results

14


matching stage (optional)

Match the storage-dominated portion of the pressure and

derivative to

obtain Cs and S

The match is poor

owing to the non-

ideal nature of the

wellbore storage

Confirm results

Refine match using

Quick Match or Auto

Match


Example 9


Course

Page 8

15

GasGas--cap modelcap model

Change the model to Gas-cap/Aquifer support

The input parameters are the same, but the top of the reservoir is

now a

constant pressure

boundary

Run Quick Match

Note how we no

longer see any

late radial flow

regime

W ith stronger well-

bore storage, the

test might yield no

useful information…

16

Alternative slant well modelAlternative slant well model

Return to the log-log plot

Select the Slanted well model

This is a partial penetration model that allows for well

deviation

The input parameters are defined differently (see Help)

Run Quick Match with the same parameters (redefined) as your

previous analysis:

ANG=0°

ZWDT = htop/h

ZWDB=(htop+hp)/h

RKZR=kz/k

IBDY=1 (no-flow boundary above and below)

Example 9


Course

Page 9

17

These parameters are equivalent to those derived in the

Log-log plot section


18

This model is stable with the varying wbs models, but it

is still not possible to match the derivative… .


Example 9


Course

Page 10

19



Page 1

Example 10

EX 10.1Example 10

Radial Composite

Reservoir

EX 10.2DataPrep• Start PanSystem

• Open file Exampl10.pan

• In DATAPREP

– Review Well, Layer and Fluid data

– Review Gauge data and Production

History (Rate changes)

• Plot pressure data including rate

changes


Page 2

Example 10

EX 10.3• This is a Fall-Off test for a Water Injection

well in an oil reservoir

• The Inner zone fluid properties should be used for the analysis

• The injection rate is defined by a negative number

• In this type of tests there are at least two radial regions:

– Inner zone - Water bank

– Outer zone - Oil bank

DataPrep

EX 10.4• ANALYSIS-PLOT

– Test Overview

– Select Fall-Off Test Period

– Log-Log plot

• Radial Composite behaviour on the derivative

• The mobility in the inner zone is higher than the mobility in the outer zone

• Select Analysis-Model and choose RadialComposite flow model

• Review the model parameters

Analysis


Page 3

Example 10

EX 10.5Analysis

Lrad is the outer radius

of the inner zone or inner

radius of the outer zone

(Distance to a radial

discontinuity).

M is the outer/inner

Mobility ratio

(k/ )outer/ (k/ )inner

w is the outer/inner

Stortivity ratio

( Ct)outer/( Ct)inner

EX 10.6Analysis• On the Log-Log plot define all the relevant flow

regimes:

Wellbore

Storage effect

Inner zone

radial flow

Outer zone

radial flow


Page 4

Example 10

EX 10.7Analysis• Confirm the results on the Log-Log plot and go to

Semi-Log plot

• Select each line and check the line results

• Confirm results

There is no analysis

procedure to get an

initial estimate for w. the

best way is to start with

w=1.0 and then use

QM/AM to find the final

value. So it is a matching

parameter.

Lrad is a function of the

intersection time of

these two straight lines.

EX 10.8Analysis• Go back to Log-Log plot

• Use Quick Match (QM) or Auto Match (AM)

• Fine tune the analysis parameters


Page 5

Example 10


END OF EXAMPLE 10

Example 11


Page 1

Example 11Example 11

Vertically fractured

well

Rev 0 1-Nov-06

2

wellfracture

k

kfbf

xf

“Infinite Conductivity”is a valid assumption if

the quantity 300f

ffCD

xk

bkF

Vertical fracture modelsVertical fracture models

h

Full-height

fracture

xf

Example 11


Page 2

3

Fracture face skin Fracture face skin SfSf

Sfrepresents an altered region of reduced

permeability ka and thickness ba, caused by frac

fluid invasion

It introduces an additional pressure drop between

reservoir and wellbore

Sfis usually a small number (< 1), but it acts over

a very large surface area (4xhxXf).

Fracture

ba

ka

4


Determine type of fracture model

Reservoir permeability (if possible)

Fracture half-length Xf

Fracture quality:

conductivity kfw

fracture face skin factor Sf

Effective skin factor Spr

W ell productivity/injectivity

Example 11


Page 3

5

Infinite Conductivity FractureInfinite Conductivity Fracture


This is a simulated water injection fall-off test



W ater is being injected from surface:

Note PVT calculated at injection temperature, not at

reservoir temperature

Note Sw=1, not default zero

The well was not hydraulically fractured

6

Analysis from logAnalysis from log--log plotlog plot


derivative

Select the Infinite conductivity fracture model

Obtain k (approximate) from the late radial (almost!) flow

regime. Confirm.

This can be refined later by simulation



Obtain fracture half-length Xf.

Example 11


Page 4

7

There is no unit slope so Cs cannot be derived from a line-fit

Check the relationship between Spr and Xf:

rweff = ½Xf = rw.e–Spr


8

Run Quick Match

Clear the lines and ‘FR’ markers

Refine the match (manually or with Auto Match)


Example 11


Page 5

9

Analysis from specialised plotsAnalysis from specialised plots

Clear Quick Match

Fit a line to the radial flow portion on the Semi-log

(Horner) Plot to

obtain k, Spr and p*

Confirm

Since radial flow

did not develop

fully, these results

will be approximate.

10

Fit a line to the linear flow portion on the square-root plot

to obtain Xf (slope) and Sf (intercept)

Confirm


Example 11


Page 6

11

Run Quick Match to refine to results manually, or use

Auto Match

Negative Sf is not allowed in Quick match



12



Match pressure and derivative

Confirm results

Refine match

using Quick Match

or Auto Match

Example 11


Page 7

13

Note that a good estimate of k can be obtained by

matching to the derivative shape even if radial flow has

not fully developed

In the absence of any transition from linear to radial flow

(test too short), an independent estimate of k (pre-frac

test, core data, other welltests) will be needed

Uniform Flux Fracture model

Go to the log-log plot, switch model to ‘Uniform flux

fracture’

Run Quick Match to compare the two models.


14

Class exampleClass example


This is a real water injection fall-off test



W ater is being injected from surface

The well was not hydraulically fractured

Example 11


Page 8

15

Data Edit PlotData Edit Plot

This file was set up with a rate change marker

positioned at the time when

the gauge was put on-depth

There is no need to

mark this point, but it does

no harm… ..

The important thing is to

specify the injection

history correctly

Gauge on-depth

Gauge

RIH

16

AnalysisAnalysis

Analyse the data in the same way as the previous

example (choose your favourite method… )

Use Quick Match to refine the parameters

Try a varying

wellbore storage

model to improve

the early match…

Example 11


Page 9

17

AnalysisAnalysis

There are two unexplained glitches in the derivative

One of them might be

explained by the well

“going on vacuum”

W ellhead pressure falls

below atmospheric, causing

water to vaporise

Can be matched (approx)

using ‘Time-stepped wbs’

model

18

Deliverabilty/InjectivityDeliverabilty/Injectivity

Select ‘Deliver’ –‘IPR’

Switch on the ‘Injection well’ box

Your k and a

computed value

of Spr will be displayed

Enter the estimated

layer pressure

Use default A and CA

Calculate

Compare with

injectivity index from

Injection Test Data (injection rate and final measured

injection pressure)

Example 11


Page 10

19

Finite Conductivity FractureFinite Conductivity Fracture


This is another water injection fall-off test



W ater is being injected from surface

The well has been hydraulically fractured

20


Fit lines –possible model?

Zero-slope (radial flow) not developed

1-slope

½-slope

0-slope?

¼-slope

?

Example 11


Page 11

21



derivative

Select the Finite conductivity fracture model

Obtain k (an upper limit) from the trend towards late

radial flow regime. Confirm.

o This can be refined later by simulation



No other line calculations are made (yet) on the log-log

plot for this model, so we will use the diagnostic plots… .

22

Linear flow plotLinear flow plot

Line-fit to linear flow regime gives Xf and, for the

finite conductivity model, FCD (instead of Sf)

Confirm in order initialise Spr

Example 11


Page 12

23

BiBi--linear flow plotlinear flow plot

Line-fit to bi-linear flow regime gives FCD from

slope

24

Run Quick Match to refine the results manually, or use

Auto Match


W hat is the significance of the negative Pi ?

Negative Pi!

Example 11


Page 13

25

Pseudo-radial flow did not have time to develop

W e have just the beginning of the transition from linear flow towards

radial (and the data are noisy!)

This is enough to give us a rough fix on permeability, but

there will be a range of uncertainty:

Experiment with Auto Match by trying fixed k values between, say,

0.1 md and 1.4 md, to see what range it could take

Use the ‘goodness of match’, and your eye, to judge what is an

acceptable match

Note the corresponding uncertainty in FCD and Xf

26


Clear Quick Match and go to the Type-Curve

section

Select the default finite conductivity type-curve set

Match pressure

and derivative to

obtain k, Xf and FCD

The picture shows

a reduced TC set

with FCD from 5 to 30

Confirm results

Use the TC filter to eliminate

unwanted curves

Example 11


Page 14

27



matching stage

Match the storage-dominated portion of the pressure and

derivative to

obtain Cs and Sf

Confirm results

Refine match using

Quick Match or Auto

Match

28

Class exampleClass example


This is buildup test in an oil producer

The well has been hydraulically fractured



Example 11


Page 15

29

AnalysisAnalysis

Analyse the data in the same way as the previous

example

Use Quick Match to refine the parameters

30


Example 11


Page 16

31

Example 12

Page 1



Gas Well Testing


• This example explains the Gas welltest analysis

workflow

• It is a DST test in a gas well

– Analyse Initial BU - reservoir pressure

– Analyse Final BU - reservoir parameters

– Analyse Flow-After-Flow for Darcy and Non-

Darcy skin factors

• Verify / Refine complete test sequence

• Calculate Deliverability

• Perform LIT and C&n analysis

Example 12

Page 2


EX 12.3DataprepDataprep• Run PanSystem

• FILE - OPEN Example12.pan

• DATAPREP-GAUGE DATA Plot pressure data

• Note the sequence of flowrates which represents a complete

DST in a gas well.

EX 12.4DataprepDataprep• Dataprep - Well and Reservoir Parameters

(Analytical…)

• Note that the fluid type is gas and the well is vertical

• Select the layer parameters

Note that the Layer Pressure and

Layer Temperature are required

as the reference gas properties

have been computed at this

condition. It is mandatory for

analysis of gas wells.

Example 12

Page 3


EX 12.5• Set model to Radial Homogeneous and Infinite Acting

and check the model parameters

• Note that there is a non-Darcy skin parameter for gas

wells which should be determined from the analysis.

DataprepDataprep

Non-Darcy skin is the pressure drop due to turbulence effect. Near

the wellbore the gas velocity is quite high therefore the flow behaviour

is turbulent flow which causes more pressure drop compared with

Darcy flow. It is a function of rock and fluid properties.

EX 12.6• Select the fluid parameters button

– The gas specific gravity is the main parameter required:

–Input this parameter directly or

–Use Gas composition and EOS to calculate it

– Use Gas Composition... button and input the following composition:

– Use Calculate button to calculate gas SG

DataprepDataprep

N2 H2S CO2 C1 C2 C3 iC4 nC4 iC5 C6 C7+ MwC7+

1.17 0.0 1.54 76.8 8.82 3.2 0.49 1.14 0.42 0.57 5.11 100.2

Example 12

Page 4



Normalising the

composition if the sum

is not 100%

Note that Schmidt-Wenzel

EOS is implemented in PS to

calculate the gas SG.

EX 12.8

• Tick the EOS option and use the appropriate gas viscosity correlation

• Review pseudo-pressure table

• Check Analysis-Pressure Transformation...

DataprepDataprep

This button

calculates

individual

selected table

This button

calculates all table

Example 12

Page 5


EX 12.9AnalysisAnalysis• ANALYSIS-PLOT

– Test Overview

– Select the first Build-up Test Period

– Semi-Log plot:

• Select TWO points on the radial flow regime, note that the radial flow is not fully developed.

• Use best fit line - Radial Flow

• Make note of the Extrapolated Pressure, P*


Example 12

Page 6


EX 12.11AnalysisAnalysis• Go back to Test Overview

• Select the Final BU and go to Log-Log plot

• Not considerable WBS effect

• Define Radial Flow regime and go to Semi-Log plot

• Confirm results

EX 12.12AnalysisAnalysisNon-Darcy Skin Calculation

• Return to Test Overview and click on the ruler bar to

select the first of the drawdowns following the first BU

• Hold down the Ctrl key and click on the other three

drawdowns to select all the periods in the flow-after-

flow test

• Perform Semi-Log plot

• There should be a line automatically on this plot

• Use the mouse right click to activate this line

• Adjust the slope to get the same permeability as the one

from final BU analysis (3.3 mD)

Example 12

Page 7



Non-Darcy Skin Calculation

• Move this line to fit the radial flow of Test Period 1

(TP1)

• Use Parallel line button to fit parallel lines through

other test periods

• Perform Analysis Non-Darcy Skin Analysis

• Re-assign the type of each lines to its appropriate test

period


Example 12

Page 8


EX 12.15AnalysisAnalysis• The Skin vs Rate button is active now

• Use this button to get S vs Q plot

• Select first and last points

• Use best fit line button to get the damage skin and Non-Darcy

skin coefficient

• Confirm results

F is Non-Darcy

flow coefficient

EX 12.16AnalysisAnalysis• Full Test Match and Verification:

– Perform Test Overview

– Select Analysis, Model, Model Parameters and change the

initial wellbore pressure to the extrapolated pressure from

the initial buildup.

– Simulate Quick Match note the poor quality of the match

at the initial buildup and at late time data.

– Change the initial wellbore pressure as above to 7150 psi

and repeat the simulation

– The data still does not match

– The simulated pressure is much higher than the observed

data - we must have some material balance / boundary

effect causing this

– Add boundaries - Single fault and simulate again

Example 12

Page 9


EX 12.17Final ResultsFinal Results

EX 12.18LIT AnalysisLIT Analysis

• Relationship between flowing pressure and

flow rate:

kh

TDF

SrC

A

kh

TB

where

FQBQpmpmie

DQSrC

A

kh

QTpmpm

wA

wf

wA

wf

1422

4ln

2

11422

)()()(

4ln

2

11422)()(

2

2

2

Example 12

Page 10


EX 12.19LIT AnalysisLIT Analysis• Click on the ruler bar to select the first drawdown of

the FAF test.

• Hold down Ctrl and click on the other flow periods

to select all of the other drawdown periods.

• Click on the LIT toolbar icon, select Flow-After-

Flow and review the tabular data

EX 12.20

• Click on OK and draw a line on the plot, ‘best fit’

through the points

• Confirm the results

LIT AnalysisLIT Analysis

Example 12

Page 11


EX 12.21DeliverabilityDeliverability

• Select Deliver - IPR

• Click on calculate

• Click on OK

• Click on T/L Lin

button to see the

Transient and LIT

results on the same

plot

• Repeat the above

exercise for the C&n

Analysis

You can generate up to 5

IPR curves for different

cases.

EX 12.22DeliverabilityDeliverability

Example 12

Page 12



END OF EXAMPLE 12

Example 13

Page 1



Gas Well Testing:

Isochronal Test


• Use Transient analysis to give Damage and

Rate Dependent Skin factors

• Generate Deliverability from transient results

• Use LIT or C&n analysis for Deliverability

alone

• Compare different deliverabilities

Example 13

Page 2



• Load EXAMPLE13.PAN

• Review input data in Dataprep

• Plot pressure and rate

• This is an Isochronal test in a dry gas reservoir.

EX 13.4Transient AnalysisTransient Analysis


• Select all the drawdowns (excluding the

extended drawdown at the end)

• Perform Semilog plot

• Draw parallel lines through the different

flow periods (Try K = 1.28 md)

Example 13

Page 3


EX 13.5Transient AnalysisTransient Analysis

EX 13.6• Select Analysis - Non Darcy Skin Analysis

• Confirm each line as Radial flow line for each test period

• Perform S vs. Q plot

• Draw line and confirm results

Transient AnalysisTransient Analysis

D = Slope

S = Intercept

Note that F is

non-Darcy flow

coefficient.

Example 13

Page 4


EX 13.7

• Return to Semilog plot

• Select Analysis - Correct for Rate Dependency

• Return to Test Overview and select the buildups

• Repeat the above exercise

Transient AnalysisTransient Analysis

EX 13.8

TransientTransient

DeliverabilityDeliverability

• Select Deliver - IPR

• Review data and

calculate transient

deliverability

• Click OK to get the

IPR plot

Use these arrows to compare up to

5 IPR curves.

Example 13

Page 5



FQBQ

pmpm

FQBQpmpm

wf

wf

)()(

)()()( 2

kh

TDF

SrC

A

kh

TB

wA

1422

4ln

2

114222

F is independent of reservoir volume and shape



• Select all the drawdowns (including the

extended drawdown at the end)

• Use LIT button, choose Isochronal and review

input data

Example 13

Page 6


EX 13.11LIT AnalysisLIT Analysis• Plot data, and fit free model line through short

drawdown points

• Fit a parallel line through extended flow point

• Confirm results

F = Slope

B = Intercept


• Select Deliver - IPR again

• Plot IPR and compare with transient IPR

Transient IPR

LIT IPR

Example 13

Page 7


EX 13.13C & n AnalysisC & n Analysis

Repeat the LIT exercise for C&n analysis.

intercept theislog1

andslope theis1

log vs)log(

log1

log1

)log(

)log(loglog

)C(Q

22

res

22

res

22

res

22

res

Cnn

Qppplot

Cn

Qn

pp

ppnCQ

pp

j

j

j

n

j


END OF EXAMPLE 13

Example 14

Page 1



Advanced Simulation


• Analyse Exampl14.PAN (already

prepared) to obtain estimate of reservoir

parameters

• Set up Start Pressures for simulation

• Perform simulation

• Compare with test data

• Correct reservoir parameters and

simulate again...

Example 14

Page 2



Analyse final build-up:

• Define wellbore storage flow regime and

confirm Cs

• Define flow regime for radial flow on log-log

plot

• Examine Semilog plot, skin estimation

• Confirm the permeability and skin factor

• Note the Extrapolated pressure

EX 14.4

AdvancedAdvanced

SimulationSimulationQuick Match starts the pressure calculation

at the start of the test period being analysed.

Example 14

Page 3


EX 14.5

AdvancedAdvanced

SimulationSimulationAdvanced Simulation always starts the pressure

calculation at the start of the first test period

The user can Save, Analyse, Report, etc… theAdvanced Simulation results but not the Quick Match results.

EX 14.6

AdvancedAdvanced

SimulationSimulation• Advanced Simulation allows the user to model

a start pressure in the wellbore and a start

pressure in the layer

• The layer pressure is entered in the layer

parameters screen

• The wellbore pressure is the pressure associated

with the first rate change

• Go back to dataprep and check this values.

• If you do not have a good value then enter the

extrapolated pressure from the semilog plot.

Example 14

Page 4


EX 14.7

AdvancedAdvanced

SimulationSimulationSelect Simulate - Advanced Simulation option:

Select input

Rate Channel

Enter individual

column names in

output data file

Select Solution

Model, TCX file,

for look-up Pd

calculations

Select speed option

EX 14.8

AdvancedAdvanced

SimulationSimulationDataprep - Gauge Data:

The output data file will now have three extra

columns:

–simulated pressure

–calculated total down hole rate

–calculated layer rate

Example 14

Page 5


EX 14.9

AdvancedAdvanced

SimulationSimulation

Compare the test data with the simulated data:

• Plot them together in Dataprep - Gauge Data

or

• Go to Analysis - Plot

• Use the Edit-Overlay Pressure... option to

display calculated pressure on the same plot.

(This can be done on Cartesian, Semilog, Log-

Log etc... plots as well)

EX 14.10

AdvancedAdvanced

SimulationSimulation

Example 14

Page 6


EX 14.11

Summary of Summary of

ResultsResults

A good match can be obtained with:

Cs = 0.023 bbl/psia

K = 80 md

S = - 0.35


END OF EXAMPLE 14

Example 15

Page 1



Test Design

EX 15.2OverviewOverview• Set up reservoir data for the test design

• Set up initial test design

• Calculate pressure based on initial test

design

• Analyse calculated pressure and check if

pressure behaviour meets test objectives

• Investigate if the fault seen on the seismic

map is sealing

Example 15

Page 2


EX 15.3Model PreparationModel Preparation

Build the simulation model:

• Initialise the system with File-New

• Ensure the fluid type is Oil (Single Phase)

• Ensure the well orientation is vertical

• Ensure there is only one well and one layer

EX 15.4Model PreparationModel Preparation

• Enter the well data

– Rw = 0.35 ft

– Cs = 0.01 bbl/psi

• Enter the layer data

– h = 100 ft

– = 0.2

– Po= 5000.0

• Flow model should be Radial Homogeneous

• Enter the model parameters

– k = 91mD

– S = 2.3

Example 15

Page 3


EX 15.5Test DesignTest Design

• Enter the fluid parameter data

– Bo = 1.1

– Uo = 0.7

– Ct = 1.0e-5

• Set up boundary data

– Set boundary model to single fault, seen on the

seismic map

– L = 250.0 ft

– Calculate image wells


Set up the test design:

• Select Dataprep - Gauge Data

• Test Design

• Enter the following test periods

– t = 10.0, q = 200.0, steps = 50, format = 2

– t = 20.0, q = 0.0, steps = 50, format = 2

• Enter a wellbore pressure = 5000.0 psia

Example 15

Page 4



• Perform advanced simulation

• Analyse the results:

– Check the build-up on the log-log plot to see if we

have met the test design objective(s)

• Results:

– Wellbore storage slightly obscures radial flow

– We can only see the start of the doubling of the

semilog slope due to the single fault

EX 15.8

Start of

Boundary effect

Test DesignTest Design

Example 15

Page 5



Let’s try again...

• Delete the previous test design data “file”

• Set up another test design extending the length of the

build-up

– t = 10.0, q = 200.0, steps = 50, format = 2

– t = 110.0, q = 0.0, steps = 50, format = 2

• Proceed as before

• Check the log-log plot of the build-up

• No change - it is the time of the draw-down that dictates

how far we see into the reservoir

EX 15.10Test DesignTest DesignLet’s try again...

• Delete the previous test design data “file”

• Set up another test design extending the length of

the drawdown as well

– t = 100.0, q = 200.0, steps = 50, format = 2

– t = 200.0, q = 0.0, steps = 50, format = 2

• Proceed as before


• Better - now we can see the beginning of the

second radial flow regime

• Complete the analysis to obtain k, S, & L

Example 15

Page 6




Let’s repeat the test with downhole shut-in.

• Do NOT delete the previous test data “file”

• Change wellbore storage to 0.001 bbl/psi

• Simulate as before, but give new names to the

simulation results channels (“pressure1”, etc)


• Do the analysis again to obtain k, S, & L

• Use Edit-Overlay Pressure to compare with high

storage case

Example 15

Page 7



Conclusions

• A 100 hour drawdown followed by a 100

hour buildup will define system (with a

little error).

• Wellbore storage needs to be reduced as

possible (downhole shut-in?), for more

accurate results.


END OF EXAMPLE 15

Example 16

Page 1



Interference Test

Design

EX 16.2

To design a pressure interference test using

PanSystem, it is necessary to define:

– Wells

– Layer and Fluids description

– Flow Rates

– Advanced Simulation Parameters

In designing, it is necessary to have the reservoir

parameters and a specific sequence of flowrates to

generate the pressure response.

Example 16

Example 16

Page 2


EX 16.3Interference TestInterference Test

The objectives of this example are:

• To build a model to handle the interference

between two wells, a Producer and an

Observation.

• Investigate the pressure behaviour in the

producer well.

• Analysing observed pressure using available

type curve.

EX 16.4Well DefinitionWell Definition• Initialize the system with File-New

• Select DataPrep and Reservoir Description

• Select type of fluid Oil and well Vertical

• Use the option Add well... and change the name

to Observer.

• Select Well-1 and change the name to :

Producer.

• The producing well is preceded by the letter P-

that means it is the principal well and is always

located at the coordinates (0,0).

Example 16

Page 3


EX 16.5Well ParametersWell ParametersFor the producing and

observation wells use:

• Well radius 0.3 ft.

• Storage 0.01 bbl/psi

The coordinates of the

observation well are (0,

2500), this means that it is

on the y-axis.

EX 16.6Layer DescriptionLayer Description

• Select Layer Parameters and input:

• Layer thickness 25 ft.

• Porosity 0.20

• Layer pressure 4000 psia

• Temperature 200 F.

• Choose Radial Homogeneous model and use the

following values

• Permeability: 250 mD

• Skin Factor : Producing well: 5

Observation well : 0

Example 16

Page 4


EX 16.7Fluids DescriptionFluids Description

• Select Fluid Parameters and input the

values:

• Oil Formation Volume Factor, Bo : 1.3

• Oil Viscosity, uo : 2.5 cp

• Total Compressibility : 1e-5 (1/psi)

EX 16.8TestTest flowratesflowratesSelect DataPrep and Gauge Data

• Flow rates are defined for the Principal well (i.e.

producing well in this case)

• Make sure to select the Producing well in the Well to

Edit dialog box

• Select the option Test Design and input the following

two flow periods as shown in the graph below:

Example 16

Page 5


EX 16.9• Select the Observation well in the Well to Edit

dialog box

• Select the option Test Design

• Reply No. to use the principal well times for the

Observation well

• Input the following two flow periods as shown in

the graph below:

TestTest flowratesflowrates

EX 16.10

AdvancedAdvanced

SimulationSimulation• Select Simulate - Advance Simulation...

• Everything is ready to run Advanced Simulation.

Do Not change controls such as:

– flow rates

– name of the generated columns

– observation points

– speed

• Select Ok to run the simulation

• Select DataPrep - Gauge Data

Example 16

Page 6



• For the producing well (Well to edit : Producer)

define the following flow periods

– Start and final points for each period.

– make sure that the pressure, the rate and the

time correspond with the graph

• Proceed to Analysis - Plot of the build up

section.

EX 16.12

Build up Analysis Build up Analysis

Flowing WellFlowing Well

Example 16

Page 7


EX 16.13

Observation Well Observation Well

AnalysisAnalysis

• Go back to DataPrep- Gauge Data

• In Well to edit dialog box select the Observer well

• Delete SIMULATED Sim Q Total and Sim Q#1

using Delete button

• Select Sim P and Plot

• Define flow periods for this well

EX 16.14


AnalysisAnalysis

Example 16

Page 8


EX 16.15

• Proceed to Analysis - Plot

• Select Observer well for

analysis

• Select the Drawdown test

period and proceed to Type

Curve analysis.


AnalysisAnalysis

EX 16.16


AnalysisAnalysis

Example 16

Page 9



END OF EXAMPLE 16

Example 17

Page 1



Reporting

EX 17.2Example 17Example 17• Load Example07.pan

• Select Report - Configure Report

• Click on Format

• Note the number of pages in each

section



• Click on Format

Note that the report is built up as you create plots and an analysis plot will not

be included unless plotted (it may be omitted by specific de-selection)

Example 17

Page 2


EX 17.3AnalysisAnalysis• Perform Log-Log plot

• Select Analysis- Model and select

Dual porosity with parallel faults

• Add flow regime markers to the plot

• Select Edit -Description

• Type some text - this ‘Description’ text box

will remain attached to the log-log plot and

will be displayed on the printed report. (it

will also be saved in the .PAN file)

EX 17.4ReportReport

• Select Report / Cover Page

• Type data in some of the requested fields

• Click on Edit - Remarks and type some text

• Return to the log-log plot

• File - Save as - EXAMP17.PAN

• Now exit PanSystem

• Restart Pansystem and load EXAMP17.PAN

• Check the remarks box and note that all of the

report related data has been included in the .PAN

file.

Example 17

Page 3


EX 17.5ReportReport


• Click on Edit beside the Input

Data line

• Note the various fields which

can be included or not as

required in the report

• Click on other Edit buttons -

review options

• Click on Edit Layout button to

review those settings

EX 17.6ReportReport

• Select Report - Select Report Template

• Note the ability to create, load, edit and save

templates

• Note that the logo used in the reports can be

included or not

• Entering a LOGO.BMP file in the reports

subdirectory will allow the user to include his own

logo.

• A second logo may be used in the report at the

other end of the page header by including a

CLIENT.BMP file in the reports directory

Example 17

Page 4



END OF EXAMPLE 17

HorizontalWelltest Analysis

Horizontal Welltest Analysis

This example covers the analysis of a horizontal well test. Recorded data comprises only the draw-down period of a well test performed in a low permeability sandstone reservoir producing oil. The method we will follow is:

Shape recognition for horizontal well tests.

Flow regimes selection - Wellbore storage - Vertical radial flow - Linear flow through reservoir - Late time radial flow

Line-fitting

Type curve analysis

Simulation / Auto-regression

2.1 Overview of Horizontal Well Test Response

zw

z w

h

h

x

x

y

y

z

z

Formation Bottom

Formation Top

Fig 13.1.1

Horizontal Well Geometry

In the analytical model we assume that kx=ky

Kbar ( k ) is the average vertical radial permeability ( kzkk . )

Lw is the effective well length (ie: the producing interval)

Zw defines the (average) well position, and ZWD = Zw / h

S is the mechanical or “true” skin factor

Lw

Side View

End View

Pseudoradial

Flow

Linear

FlowRadial Vertical

Flow

FLOW REGIMES

linear

flow

pseudo

radial

flow

plateau

plateau

half slope

no wellbore storage

Fig 13.2.2

Horizontal Well Log-Log Derivative Diagnostic

log p

log t

1

2

3

Well in middle (ZWD=0.5)

RVF

hemi

radial

flow

no wellbore storage

half

slopesecondplateau

firstplateau

Fig 13.2.3

log t

log p

Hemiradial and Linear Flow Diagnostics

log p

Spherical Flow in a Horizontal Wellof Short Length

pseudoradial

flowspherical

flow

negativehalf

slope

RVF

L < h

Fig 13.2.4

2.2 Horizontal Well Test Analysis Workflow

The data file is called HORIZON.PAN. The original gauge data have already been imported, edited, and the rate change events picked graphically (as explained in Example 1 of the on-line Help). All well and reservoir data have been entered and the file saved as a .PAN system file, ready for analysis. This example will review only the horizontal well part of the Well and Reservoir Parameter input. The rest of this type of input is covered (for an oil well) in Example 2 of the on-line Help.

Well offset from middle (ZWD 0.5)

The whole test is shown in Figure 1, (Dataprep, Gauge Data option, Plot button).

Figure 1 - Data Edit Plot The surface flowrate schedule for the test is listed in the Rate Change table (Dataprep, Gauge Data option, Rate changes button).

Figure 2 - Rate allocation

2.2.1 Principal Well Orientation

Select the Dataprep menu, Well and Reservoir Description (Analytical) option and this brings up the Reservoir Description dialog box. Make sure the Principal Well Orientation is checked as Horizontal and the Fluid Type is checked as oil. Click the Layer Parameters button and note that estimates of Formation thickness, Porosity and Total Compressibility have been entered. Note that the ‘Two no-flow boundaries – homogeneous’ model has been selected as Model in the Flow model (horizontal well) section since this is sandstone reservoir with no gas cap. The dialog box appears as shown in Figure 3.

Figure 3 - Layer Parameters Dialog Box

2.2.2 Analysis

The purpose of analysing this draw-down is to get an estimate of the reservoir parameters and the producing (effective) open interval length. You can do your own analysis of the plots for this draw-down. Our interpretations and actions were as follows:

Select Analysis menu option Plot. This displays the Test Overview.

Log-log plot (Fig 4):

- Unit slope line through the wellbore storage regime (optional - mark the regime). Cs = 0.02 bbl/psi.

- Zero slope line through the vertical radial flow regime (enter the design open well length of

1000 ft at the prompt). kbar 1 md. Fit the flow regime markers to compute the skin factor S. (S is the “true” or mechanical skin factor.)

- Half-slope line in the ‘Linear flow through layer’ portion. Model Results display Lw = 960-990 ft.

- Zero slope in the (almost!) late radial flow regime. Model results display k = 1 - 1.1 md. PanSystem can now calculate kz = 0.88 - 1 md from kbar and k. Spr = –6.

Note the large negative pseudo-radial skin factor Spr, typical of a horizontal well. Note also the long time required for the reservoir to approach the late radial flow regime in the test.

Figure 4 - Log-log plot of the draw-down

Radial Flow Plot (Figure 5): Fitting lines through the radial flow portions give: Kbar 1 md., S 0,

K 1.1 md, Spr –6, Kz 0.9 md. Marking the radial flow regimes while on the log-log plot makes the radial flow plot line-fitting a lot easier and less prone to error.

You can move any line by selecting it (click the right mouse button, or press the Ctrl key and click on the line) and dragging a central or end grab-handle (small black square).

Figure 5 - Radial Flow plot

Linear Flow Plot (Figure 6): fitting a line through the linear flow portion gives: Lw 985 ft,

Sconv 3.9. Again, marking the linear (or quasi-linear) flow regime while on the log-log plot makes the line-fitting easier.

Figure 6 - Linear Flow Plot Where:

Kbar, is the average vertical radial permeability ( kzkk . )

Lw is the effective well length (ie: the producing interval) S is the mechanical skin factor

Spr is the pseudo-radial skin factor (or effective, or total skin factor) Sconv is the convergence skin – a component of the pseudo-radial skin factor.

Type curve plot: Select Log-log plot. Click the TC toolbar icon to perform Type Curve analysis. Select the M (Match) toolbar icon. In the Select Type Curve dialog box, select unknown well length for the Type Curve Method, with Default Type Curves clicked. Click OK. The Choose Zwd for these curves dialog box will appear as shown in Figure 7.

Figure 7 - Choosing Zwd

Select 0.5 as Zwd since the derivative does not show evidence that the well is excentered in the formation (no hemi-radial flow regime – step-like behaviour) and click OK. The plot will be presented with draw-down type curves for horizontal wells displayed.

Figure 8 - Horizontal Well Type Curve Match

The curves can be moved over the data by dragging them with the mouse until a match in found. When close to matching, you can use the arrow keys to move the curves if you prefer – coarse steps when pressed alone, fine steps when you hold down Ctrl and press the arrow key.

A better look into the type curve match can be obtained by zooming the data together with the type curves.

Once finished, you can display the final type curve by clicking M again

Once the type curves are matched, select M again to terminate matching mode. The nearest matching curve (counting bottom up) is displayed along with the corresponding value (curve #8, curve value = 12.00). Change the number displayed if you disagree with it. Select OK. The model parameters are computed from the match: Kz = 1.2 md, K = 0.9 md, Lw = 1045 ft., Zwd = 0.5.

Select the right arrow icon in the type curve matching toolbar to move to the next stage of type curve matching. Match the type curve that best fits the wellbore storage period (curve # 4, Cde

2S =

10). No vertical movement is permitted, since the vertical radial flow position of the derivative has already been fixed in the preceding stage. The model parameters are then computed from the

time and curve match: Cs 0.016 bbls/psi, S 0.2.

The screen should now be as shown in Figure 9.

Figure 9 - Wellbore Storage and Skin Type Curve Match Do not forget to confirm the results (Cnf icon) if you want to store them as the latest model parameters. Fine-tuning of the match can be performed in the Simulate menu using the option Quick Match, or using the Auto Match option (non- linear regression) after selecting some representative points in the derivative. Finally, check the quality of the analysis by inspecting the matching of the measured with the generated data on the various plots - log-log plot (Fig.10), radial flow plot (Fig.11), specialized (linear) flow plot, and test overview.

Figure 10 - Final Match: log-log plot

Figure 11 - Final Match: semi-log plot

2.2.3 Pseudo-radial flow

Once the pseudo-radial flow regime has been attained, the horizontal well behaves just like a vertical well with a skin factor equal to Spr in a reservoir of permeability k. The combined effects of all of the flow patterns particular to the horizontal geometry are lumped into Spr, which is usually strongly negative owing to the beneficial effect of the long drainhole Lw.

5.0)()4817.4ln(

AL

hSS

L

rS

w

conv

w

wpr

The term lnr

L

w

w

( . )4 4817 is a pseudo-radial areal flow convergence skin (into an equivalent vertical

well of radius Lw

4 4817. ). (Ref: Goode and Wilkinson (JPT Aug 91, and SPE 19341, (Morgantown, Oct

89) and supplement 23546).) The horizontal well can, therefore, be modeled as a vertical well, which is mathematically much simpler, once late radial flow has been attained, and onwards into semi-steady state. This is useful for IPR calculations. (The presence of boundaries which are close enough to be seen on the transient response before pseudo-radial flow is reached will complicate matters.)

Returning to Fig.8 (repeated below), take a look at the derivative shapes for the range of parameters covered.

Figure 12 - Horizontal Well Type Curves

Each curve represents a value of dimensionless well length k

k

h

LL zwWD , starting at 0.2 at the

bottom, and increasing to 200. Note that the classical horizontal welltest response, with the derivative starting in vertical radial flow, then rising through linear flow and ending in late radial flow, need not always be the case.

True linear flow (half-slope) will only develop if LWD is large enough. This implies a Lw >> h, and anisotropy will exert an influence too. LWD > 20 (curve #9) is a reasonable threshold.

Large LWD means a long test duration to reach pseudo-radial flow. A long drainhole in an isotropic formation will not reach pseudo-radial flow within a reasonable testing time, which means that horizontal permeability k will not be accessible from the test. However, with good quality data, it may be enough to have some curvature away from the linear flow portion (as in the example) to give a fairly good indication of which trend line we are on.

The “anti-classical” response, where the derivative goes down, or dips and barely rises, simply requires that LWD < 1 (curve #4 is LWD=1.2).

Another way of looking at this is to consider that the early vertical radial flow regime represents

the product zw kkL . , while the late radial flow regime represents kh. For the derivative to go

down into late radial flow, we require that zw kkLkh . , which, rearranging the terms,

means that 1 > LWD, ie: LWD < 1.

LWD=0.2

LWD=1.2

LWD=200

LWD=20

2.2.4 An Alternative Analysis

Figure 13 - An alternative interpretation – short well length, intersecting faults, but a rather high kz!

It is in fact possible to fit quite a range of parameter sets to this data, though the matches tend to be of poorer quality that the one just demonstrated. Reasonable matches can obtained with a short well length, high vertical permeability, and the addition of boundaries (something between 30° and 45° intersecting faults). Local knowledge (and common sense!) will be required to determine what might be acceptable in geological terms.

Example 1

Page 1


1

The Pressure Derivative

2

Pressure Drawdown Theory for an Infinite

Acting Reservoir with an Altered Zone

2

1ln 0.80908 2

2

141.2 1 0.000264ln 0.80908 2

2

D D

i wf

t w

p t S

qB ktp p S

kh c r

Hence plot pwf vs. ln t is a straight line

giving: pwf = m* lnt + pt=1

70.6qBm kh k

kh

1 2

1

2

0.000264ln 0.80908 2

1. . ln 7.43173

2

t i

t w

t i

t w

kp p m S

c r

p p ki e S

m c r


S from intercept

at t=1hr

Example 1

Page 2


3

Oilfield Units with Log10

2

1 2

1

2

162.6log log 3.2275 0.86859

162.6

log 3.2275 0.86859

1.1513 log 3.2275

i wf

t w

t hr i

t w

t hr i

t w

qB kp p t S

kh c r

qBm kh k

kh

kp p m S

c r

p p kS

m c r


S from intercept at t=1 hr

4

Pressure DerivativePressure Derivative

The pressure derivative in its simplest form - for a

drawdown with no previous history - is:

p = dpd(log t)

When rate history is involved (buildup test, any welltest

where there have been flowrate changes in the recent

past), the log ( t) is replaced by a more complex

logarithmic function based on superposition theory.

But the principles of interpretation are the same.

Example 1

Page 3


5


The pressure derivative:

• Magnifies changes in pressure trends

• Has slope values that identify flow regimes

• zero slope = radial flow

• ½-slope = linear flow

• and many others ….

• Has characteristic shapes that help identify the

reservoir and boundary models

• the most important ones should be memorised

6


For a constant rate drawdown in a radial homogeneous

reservoir, welltest theory says that:

p log( t)

P

log t

which means that dp = constantd(log t)

In radial flow,

pressure has constant slope

when plotted against log t

Derivative has constant valueP

Example 1

Page 4


7


A change of slope in the pressure is a change of

value in the derivative:

P

log t

For example, if a boundary (fault) is

detected, the pressure trend goes to

double slope

Derivative goes to new constant

value (two times old value)

P

8


The derivative is usually plotted on a log-log plot:

Log p

Log t

Radial flow

Boundary

??

Delta t

Example 1

Page 5


9


p = P0 - P

t = t -T0

(T0, P0)

Definition of Delta t and Delta P for a drawdown test

Data point at

(time = t, pressure = P)

Gauge clock time

10

•The way that delta P is defined for a

drawdown means that the pressure data

appears upside down on the log-log

plot:


Example 1

Page 6


11


p = P - P0

t = t -T0

(T0, P0)

Definition of Delta t and Delta P for a buildup test

Data point at

(time = t, pressure = P)

12


• Delta t (or t) is also referred to as Elapsed time - it

is the time that has elapsed from the start of the test

period (T0).

• Delta P (or P) is defined in such a way that it is

positive for a drawdown or a buildup.

• This means that the log-log plot for a drawdown

looks very much like the log-log plot for a buildup.

Example 1

Page 7


13


Drawdown

Buildup

p = P - P0

p = P0 - P

Equivalent time (hours) – Tp=100.0

EPS Derivative Diagnostic Library

p’t

∆t

∆te

Logarithmic derivative Elapsed time in a drawdown

Elapsed (shut-in) time in a buildup

Agarwal equivalent drawdown time

for a buildupETR Early time regionMTR Middle time regionLTR Late time region0s Derivative plateau1/2s Half slope1/4s Quarter slope1s Unit slope-1/2s Negative half slope-1s Negative unit slopeCRD Constant rate drawdownInfCon Infinite conductivityFinCon Finite conductivityW Channel widthL Distance to nearest boundaryLw horizontal well length

e-petroleumservices.comTelephone +44 (0)131 449 4536 Fax +44 (0)131 449 5123

Nomenclature

Vertical Fractured Well

Diagnostic Diagnostic

Diagnostic

DiagnosticDiagnostic

Diagnostic

Model Model

Model

ModelModel

Model

p p

p

pp

p

t t

t

tt

t

Fractured Well (InfCon) Fractured Well (FinCon)MTR

MTR

MTRMTR

ETR ETR

ETRETR

ETR

ETR

ETR

0s0s

0s

0s

0s0s

0s

1/2s

1/2s

1/4s

1/4s

1s

Horizontal Fracture

Horizontal FractureHorizontal Fracture

CRD

CRD

CRD

CRDCRD

CRD

CRDCRD

Thin Reservoir

MTR

MTR

F > 10CD

F < 10CD

Conductive Lens

"Geoskin"

B1

B2

B3

B4

B5

B6

Diagnostic DiagnosticModel Model

p p

t t

MTR

0s

ETR

1/2s

1/4s

Apparent Quarter Slope

CRD CRDB7 B8

with Storage and Skin

0s

0s1s

1/4s

MTR

ETRFractured Well (InfCon) Fractured Well (InfCon)

1/2s1/2s

1/2s

Fractured Well (FinCon)

Diagnostic Model

p

t CRD

Limited Height Fracture

hf

xf

MTRETR

HS

DP

IC

B9

Diagnostic Model

p

∆te BUFB10

Fractured Well (IC)

Agarwal Overcorrection

ETR

HS

US

Horizontal Wells


Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p p

p

pp

p

t t

t

tt

t

H1

Lw

Lw

Lw

Lw

Horizontal Well

Horizontal Well

Horizontal Well

Horizontal Well

Horizontal WellHorizontal Well

Horizontal WellHorizontal Well

No Flow Upper and LowerBoundaries

No Flow Upper and LowerBoundaries

CRD

CRD CRD

CRD

MTR MTRMTRLTR LTRLTR

LTR

LTRLTR

0s 0s

0s0s

0s

0s

0s0s0s

0sP

1/2s

1/2s-1/2s

1/2s

0s1/2s

1/4s

H2

L > 10D

L > 10D

Acid Stimulation

PRFNatural Fracturesplus Face Skin

ETR

Offset Position

Tight Matrix

H3 H4

H5 H6

MTR

MTR

m2m

L < 0.2D

DrainHole


p p

t tH7

Gas CapSupport (CPUB)

Horizontal Well Horizontal WellLTR LTR

0s 0s

MTR

MTR

m m

2m 2m

Strong BottomWater (CPLB)

H8CRD or BU-MDH

Diagnostic Model

p

t

Horizontal Well

Dual Porosity Strata

Low Perm. Layer0s

1/4s

ETR

H9 CRD

CRD or BU-MDH

0s

0s

0s

Diagnostic Model

p

tH10

Horizontal

Well

Matrix

Damage

ConductiveFault

1/2s-1/2s

1/4s

Wellbore Storage Overlay


Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p p

p

pp

p

t t

t

tt

t

Ideal Wellbore StorageHomogeneous Reservoir

Nonideal Wellbore StorageHomogeneous Reservoir

Phase Redistribution- the "famous spike"

MTR

MTR

MTRETR

ETR

ETR

11/2 LogCycle

1s

1s

1s

0s

0s

0s

I1 I2

NWS

NWS

NWS

NWS

HR

HR

IWS HR

Near Single Fault

Far Single Fault

m

2m0s

1s

ETR

ETR

LTR

LTR

1s

MTR

0s0s

I3 I4

I5 I6

m2m


Tight Zonem

m/20s

MTR

0s

ETR NWS

CRD

CRD

CRDCRDCRDCRD

CRDCRD

CRD


p p

t t

IWS IWS

Fractured Well (InfCon) Fractured Well (FinCon)

No Skin No SkinETR MTR

0s

1/2s

1s

1/4s

1s

ETR

Small FCD

I7 I8

Diagnostic Model

p

t

NWS HR

I9

Phase Redistribution"Humping"

ETR MTR

0s

1s

m

0s

Diagnostic Model

p

tI10

ETR MTR

0s

1s0s

Dual Porosity

Semi-infinite Sealing Fault Systems Diagnostic Diagnostic

Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p

p

p

pp

p

t t

t

tt

t

L

Single Fault

CRD CRD

CRDCRD CRDCRD

CRDCRD

MTR

MTRMTR

MTR

MTR

MTR

MTR

LTR

LTR

LTR

LTR

LTRLTR

0s

1/2s

1/2s

1/2s

0s

0s

0s

0s0s

0s

0s0s

m

2m

L

Right Angle Faults

m

4m

Limited Extent (Baffle)

Lm

2m

Parallel Faults

Parallel Faults

W

WW

L

LL

U-Shaped Faults

Well Offsetm

2m

D1 D2

D3 D4

D5 D6

DiagnosticDiagnostic ModelModel

pp

∆t∆teBUF BUF

W WL L

MTR MTRLTR LTR

0s 0s1/2s1/2s

1s

Channel Reservoir Channel Reservoir

Agarwal Overcorrection Yeh Empirical Mod.

D7 D8

Single Fault

Diagnostic Model

p

t CRD

MTR LTR

D10

L

o120 Intersecting Faults

m

3m

o120

Diagnostic Model

p

t CRDD9

o45

L

o45 Intersecting Faults

m

8m MTR

LTR

1/2s

0s

0s0s

0s

Diagnostic Model

p

t CRD

LTR Open-ended U ShapeMTR

m2m

D11

0s

1/2s

0s

Diagnostic Model

p

t CRD

DP

LTRMTR

m2m

D12

Major and Minor Fault

0s

0s

1/2s

Double Porosity and Dual Permeability Systems


Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p

p

p

p

p

p

t t

t

tt

t

Diagnostic Model

p

t CRD CRD

CRD

CRDCRD

CRD

CRD

MTR

MTR

MTR

MTR

ETR

ETR

ETRETR

ETR

LTR

ETR

0s

0s

0s

1s

0s

0s

0s

0s

0s

0s0s0s

0s0s

0s

1/2s

1s

Inf. Conductive Inner

Finite Wellbore Radius

Dual-porosity (transient)

Dual-Porosity (sss)

Interporosity Skin

No Interporosity Skin

m

m

m/2

m/2


Tight Zone

High Perm. Zone

Reservoir Storage

High Perm Closed Layer

Infinite Low Perm. Layer

MTR

MTR

Dual Permeability

Semipermeable Barrier

C1

C2

C3

C4

C5

C6

Partially Communicating Faults and Linear Composite Systems Diagnostic Diagnostic

Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p

p

p

pp

p

t t

t

tt

t

Partially CommunicatingFault

Inf.-Acting

CRD

CRD CRDCRD

BUF

CRDCRD

CRD or BUD

LTR LTR

LTRLTRLTR

LTR LTRLTR

MTR MTR

MTR

MTR MTR

m

2m

0s

0s

0s 0s0s 0s

1s

1s 1s

0s 0s

0s0s

0s

G1 G2

LinearComposite

Linear Compositeplus Barrier

LinearComposite

G4G3

G5 G6

Two Cell Compartmentalised

Two Cell Compartmentalised

Closed Reservoir Compartments


Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p p

p

pp

p

t t

t

tt

t

Closed Square Closed Square

CRD or BUD

CRD or BUD

CRD or BUD

BUF

BUF

BUFBUF

MTR

MTR MTR

MTRMTRLTR

LTR

LTR LTR

LTRLTR

LTR

0s

0s 0s

0s1s

1s

1s

1/2s

1/2s 1/2s

Rectangular Reservoir Rectangular Reservoir

Rectangular Reservoir Rectangular ReservoirRectangular Reservoir

1/2s

Offset Well Offset WellOffset Well

MTR

MTR

E1 E2

E3 E4

E5 E6

0s 0s

Constant Pressure Boundaries


Diagnostic


Diagnostic

Model Model

Model

ModelModel

Model

p p

p

pp

p

t t

t

tt

t

DistantGas Cap

0s

0s

0s-1s

-1s

-1s

MTR

MTR

MTRLTR

LTR

LTR

DistantStrong Aquifer

CRD or BU-MDH

CRD or BU-MDH

CRD or BU-MDH

CRD or BU-MDHCRD or BU-MDH

CRD or BU-MDH

CRD or BU-MDH

Gas CapSupport (CPUB)

LTR LTR

LTR

ETR ETR

0s 0s

Strong BottomWater (CPLB)

NonintersectingFracture

1/4s

Channel Reservoirwith Edge Water

CPB

MTR

1/2s

0s

F1 F2

F3 F4

F5 F6

Limited Entry and Radial Composite SystemsDiagnostic Model

p

t CRD

0s

MTR Homogeneous Reservoir

Infinite-Acting

A1

Diagnostic Model

p

t CRDCRD

MTRETR

0s

0s

Radial Composite

Tight Inner

A4

Diagnostic Model

p

t CRD

MTRETR

0s

Limited Entry

A2

Diagnostic Model

p

t CRD

MTRETR

0s

0s

Radial Composite

Conductive Inner

A5

Diagnostic Model

p

t CRD

MTRETR

0s

0s

Shale Lens

A6

Diagnostic Model

p

t CRD

MTRETR

0s

Extreme Limited Entry

A3

-1/2s

Diagnostic Model

p

t CRDA8

Well Offset in a ChannelMTR ETR

1/2s0s

Diagnostic Model

p

t

Top

Bottom

Pinch-Out

h

CRD

MTR LTR

m

A7

0s

-1/2s

eps training

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