production data analysis in tight gas sandsblasingame)_pres_apc_tight_gas_conf.pdfproduction data...

Slid

e —

1/79

2007 Anadarko Tight Gas Workshop05 December 2007 — The Woodlands, TX

Production Data Analysis in Tight Gas SandsT.A. Blasingame — Texas A&M U. (05 December 2007)

2007 Anadarko Tight Gas WorkshopReservoir Description/Characterization

04 December 2007 — The Woodlands, TX

Tom BlasingameDepartment of Petroleum Engineering

Texas A&M UniversityCollege Station, TX 77843-3116 (USA)

+1.979.845.2292 — [email protected]

Production Data Analysisin Tight Gas Sands

Slid

e —

2/79









Before We Start …

Slid

e —

3/79



Model-Based Production Analysis:Use of an analytical or numerical model in the analysis. Use all components: Model, MB, History Match, Arps.

Empirical Production Analysis:Arps or other "approximate" rate equations. Need better "diagnostics" for application.

Gotchas:Can not estimate reserves without pss flow behavior. Be (very) careful with application of Arps equations.

Before We Start: Prod. Analysis in Tight Gas Sands

Slid

e —

4/79









Orientation

Slid

e —

5/79



Facts for TG/SG Resources: (North America)Reserves are in the 1000's of TCFs.Development is the fastest growing segment.Have production potential for BCFs/D.

Fiction for TG/SG Resources:Can be developed on the cheap.Well completions/well stimulations will save the day.Reservoir Engineering (and Geology) does not matter.

Orientation: Tight Gas/Shale Gas (TG/SG) Systems

Slid

e —

6/79



Geology/Petrophysics: IssuesReservoirs are below water zone(s).Reservoirs are typically over-pressured.Reservoirs have extreme vertical heterogeneity (layers). Reservoirs have significant lateral heterogeneity.Reservoir quality is controlled by deposition.

Orientation: TG/SG Geology/Petrophysics

Slid

e —

7/79



Reservoir Engineering: IssuesTypically over-pressure/over-temperature (HP/HT).Water saturation can be very high (30-70 percent). Pressure transient testing is a waste of time.Production data analysis is too "simple."We tend to assume wells do not interfere.Multilayer effects can dominate performance.

Orientation: TG/SG Reservoir Engineering

Slid

e —

8/79



SPE 71351 and 71352An Integrated Work-Flow Model to Characterize Unconventional Gas Resources: Part I—Geological Assessment and Petrophysical EvaluationAn Integrated Work-Flow Model to Characterize Unconventional Gas Resources: Part II—Formation Evaluation and Reservoir ModelingK.E. Newsham, SPE, Anadarko Petroleum Corp. and J.A. Rushing, SPE, Anadarko Petroleum Corp.

Q. Is there a comprehensive data integration model?

A. The Petrophysical Integration Process Model (PIPM) —papers SPE 71351 and 71352 are a good start.

Strengths of this approach: All pertinent data are used. The integration process con-

firms/disputes data correlations. Weaknesses of this approach: Data. Data. Data. Expertise/experience.

Orientation: Data Integration

Slid

e —

9/79









History — Evaluationof Reservoir Performance

for Tight Gas Sands

Slid

e —

10/7

9



Pressure Transient Analysis: Fractured WellsQ. Is a finite-conductivity vertical

fracture model relevant?A. Yes (of course).

SPE 6014Transient Pressure Behavior for a Wen With a Finite-Conductivity Vertical FractureH. Cinco-Ley,· Instituto Mexicano del PetroleoF. Samaniego-V.,· Instituto Mexicano del PetroleoN. Dominguez,· Instituto Mexicano del Petroleo

Finite-Conductivity Fracture (SPE 6014) Most popular model for PTA. Virtually all fractured well analyses.

Slid

e —

11/7

9



Q. Is a choked or damaged fracture the same as a finite-conductivity vertical fracture?

A. No — not even in a "practical sense." Fracture damage is difficult to assess and a "frac-ture face skin" model should be used to represent damage.

SPE 10179Transient Pressure Analysis: Finite Conductivity Fracture Case Versus Damaged Fracture CaseHeber Cinco-Ley,· PEMEX and UNAMFernando Samaniego-V.,· PEMEX and UNAM

Pressure Transient Analysis: Fractured Wells

Slid

e —

12/7

9



Q. How do we characterize, model, validate the multiple fracture concept?

A. Very complex models have been developed for multiple, arbi-trary-oriented vertical fractures.

SPE 100586Constant-Rate Drawdown Solutions Derived for Multiple Arbitrarily-Oriented Uniform-Flux, Infinite-Conductivity, or Finite-Conductivity Fractures in an Infinite-Slab ReservoirD.P. Craig, Halliburton and T.A. Blasingame, Texas A&M U.

Tri-Fracture Solution (SPE 100586) Restimulation case. Pressure transient test is

matched by tri-fracture solution. Must re-think well stimulation/

evaluation practices.

Pressure Transient Analysis: Fractured Wells

Slid

e —

13/7

9



Q. Better flow regime identification for pressure transient data?

A. -Derivative Function (power law formulation).

SPE 103204The Pressure Derivative Revisited —Improved Formulations and ApplicationsN. Hosseinpour-Zonoozi, D. Ilk,and T.A. Blasingame,SPE, Texas A&M University

●-derivative — fractured well (inf-cond) (No WBS).

●-derivative — horizontal well (inf-cond) (No WBS).

●-derivative — radial flow, dual-porosity (no WBS).

●-derivative — general schematic plot (No WBS).

●-derivative — Infinite-acting radial flow, with WBS.

●-derivative — Match for Well 12 (SPE 9975).

Pressure Transient Analysis: New Diagnostics

Slid

e —

14/7

9



Q. Do fracture flow regimes really matter?

A. Depends on your perspective —transient flow helps to quantify reservoir/fracture properties, BUT fracture extension deter-mines reserves in low perme-ability reservoirs.

SPE/DOE 9839Use of Constant Pressure, Finite Capacity Type Curves for Performance Prediction of Fractured Wells in Low-Permeability ReservoirsJ.K. Thompson, ARCO Oil and Gas Company

Production Analysis: Fractured Wells

Slid

e —

15/7

9



Q. Fracture orientation, elliptical flow geometry, and reservoir properties — inter-relations, significance, practical issues?

A. Virtually all fractured wells in very low permeability reservoirs are presumed to have an elliptical drainage area for contacted fluids in-place.

SPE/DOE 9851Fracture Optimization in a Tight Gas Play: Muddy "J" Formation, Wattenbarg Field, ColoradoC.N. Roberts, Amoco Production Co.


Slid

e —

16/7

9



Q. Elliptical flow for analysis of production data?

A. Probably the "best" answer —particularly for "transition flow from transient to boundary-dominated flow.

SPE 106308Evaluation of the Elliptical Flow Period forHydraulically-Fractured Wells in Tight GasSands — Theoretical Aspects and PracticalConsiderationsS. Amini, D. Ilk, and T. A. Blasingame,SPE, Texas A&M University


Slid

e —

17/7

9



Q. Better flow regime identification for production data analysis?

A. -Derivative Function (power law formulation).

SPE 107967Application of the -Integral Derivative Function to Production Analysis

D. Ilk, N. Hosseinpour-Zonoozi, S. Amini,and T.A. Blasingame,SPE, Texas A&M University

●dpD/dln(tD) vs. tD [Semilog] ●dln(pD)/dln(tD) vs. tD [-deriv.] ●pD-functions (Radial Flow). ●qD-functions (Radial Flow).

●qD-functions (EllipticalFlow — FE =1).

●qD-functions (EllipticalFlow — FE =1000).

●|dqD/dln(tD)| vs. tD [Semilog] ●|dln(dD)/dln(tD)| vs. tD [-deriv.]

Production Analysis: Diagnostics

Slid

e —

18/7

9



Q. What are the pitfalls in product-ion data analysis?

A. What is not a pitfall? Poor data, poor records, etc. …

SPE 102048Production Data Analysis — Challenges, Pitfalls, DiagnosticsD. M. Anderson, G.W.J. Stotts, L. Mattar, Fekete Associates Inc., D. Ilk, and T. A. Blasingame, Texas A&M U.

●log(qg) and pwf vs. t — good synchronization of data.

●pwf vs. qg — "crude" cor-relation plot.

●Rate functions vs. Gp/qg —diagnostic plot.

●Deconvolved pressures vs. t — (ultimate test of data).

Production Analysis: Pitfalls

Slid

e —

19/7

9









Recent Workby Blasingame et al.

Slid

e —

20/7

9



Excerpts from:

SPE 106308Evaluation of the Elliptical Flow Period for Hydraulically-Fractured Wells in Tight Gas

Sands — Theoretical Aspects and Practical Considerations

S. Amini, D. Ilk, and T.A. BlasingameDepartment of Petroleum Engineering

Texas A&M UniversityCollege Station, TX 77843-3116

(979) 458-1499 — [email protected] SPE Hydraulic Fracturing Technology Conference — College Station, Texas — 29–31 January 2007

SPE 106308 — Evaluation of the Elliptical Flow Period for Hydraulically-Fractured Wells in Tight Gas Sands —Theoretical Aspects and Practical Considerations (Amini/Ilk//Blasingame)

T. Blasingame — Texas A&M U. (29 January 2007)

Slid

e —

21/7

9



Executive Summary: Elliptical Flow System●Description:

This work provides a new set of decline type-curves for a fractured well in an elliptical flow system:■Finite-conductivity hydraulic fracture of half-length, xf.■Closed elliptical-shaped boundary.■Canonical distance is equal to the fracture length.

●Schematic of the elliptical reservoir model.

2007 SPE Hydraulic Fracturing Technology Conference — College Station, Texas — 29–31 January 2007SPE 106308 — Evaluation of the Elliptical Flow Period for Hydraulically-Fractured Wells in Tight Gas Sands —

Theoretical Aspects and Practical Considerations (Amini/Ilk//Blasingame)T. Blasingame — Texas A&M U. (29 January 2007)

Slid

e —

22/7

9



●Deliverables:■ Series of decline type-curves

for a well with finite conductiv-ity vertical fracture centered in a bounded, elliptical reservoir.

■ Field case applications of the new set of type curves on the analysis of production data from tight gas reservoirs.— E. Tx tight gas (0.006 md)— N. Tx very tight gas (0.0007 md)— N. Tx tight gas (0.003 md)— Mexico very tight gas (0.001 md)

■ Very powerful diagnostic tool for evaluating fractured wells in low to ultra-low permeability gas reservoirs.

Executive Summary: Elliptical Flow System



Slid

e —

23/7

9



Development of the Solution: Type Curves

●Discussion:■ The equivalent constant rate format type curves for this work are

shown in qD versus tDA format (this simplified the transient regime).■ Various elliptical fracture conductivities: FE = 1,10,100, and 1000.

■ Type curve for a fractured well centered in a closed (homogeneous) elliptical reservoir — FE=10, various ξ0-values; qD functions versus tDA format.




Slid

e —

24/7

9





Development of the Solution: Type Curves

●Discussion:■ Objective: To demonstrate the elliptical boundary model as a diag-

nostic to establish the elliptical flow regime using production data.■We utilize type curve solutions in terms of the equivalent constant rate

case presented in "decline" form (qD and tDA). 2007 SPE Hydraulic Fracturing Technology Conference — College Station, Texas — 29–31 January 2007



Slid

e —

25/7

9



Validation and Application: East TX Tight Gas

●Discussion:■ Daily rate and pressure data show good correlation.■ "Better-than-average" data acquisition practices yield high-quality

production data for the analysis/interpretation for this case (SPE 84287).2007 SPE Hydraulic Fracturing Technology Conference — College Station, Texas — 29–31 January 2007



Slid

e —

26/7

9



●Discussion:■ Diagnostic plot confirms the very good correlation of data for this case.■ Strong indication of fractured well regimes tending to boundary flow.




Slid

e —

27/7

9



●Discussion:■ Excellent data match — confirms the validity of the "elliptical" model. ■Model parameters: FE = 1, ξ0 = 0.50.■ "Average" analysis results: k ≈ 0.006 md, xf ≈ 300 ft, Gp ≈ 1.6 BSCF.




Slid

e —

28/7

9



Validation and Application: Mexico Very Tight Gas

●Discussion:■ Good data acquisition (monthly data > 40 years) — rate data is consistent,

and constant ptf → pwf is reasonable considering production/location.■ The reservoir permeability < 0.001 md (all analyses).■ This is the only well in the field (no possibility of well interference).



Slid

e —

29/7

9



●Discussion:■ Diagnostic plot indicates extraordinary character in data (1/2 slope trend → high fracture conductivity), very good diagnostic trends.

■ Very low permeability estimate is expected.




Slid

e —

30/7

9



●Discussion:■ Outstanding data match — confirmation of the elliptical boundary model.■Model parameters: FE = 100, ξ0 = 0.25.■ "Average" analysis results: k ≈ 0.001 md, xf ≈ 825 ft, Gp ≈ 23.0 BSCF.




Slid

e —

31/7

9



Application of the -Integral Derivative Function to Production Analysis

D. Ilk, N. Hosseinpour-Zonoozi, S. Amini,and T.A. Blasingame

Department of Petroleum EngineeringTexas A&M University

College Station, TX 77843-3116(979) 458-1499 — [email protected]

Excerpts from:

SPE 107967

(16 April 2007) Rocky Mountain Oil & Gas Technology Symposium

Application of the -Integral Derivative Function to Production AnalysisIlk/Hosseinpour-Zoonozi/Amini/Blasingame

Slid

e —

32/7

9



Rationale For This Work●The primary purpose of this work is to intro-

duce and demonstrate the application of the -integral-derivative function for production analysis (PA).

●Our mechanism to promote this work is to provide an inventory of "type-curve" solu-tions for various bounded reservoir models to increase the resolution for the diagnostics of production data.

●The -derivative function for PA is defined in terms of the rate and pressure integral and integral-derivative functions for smoothnessand clarity.



Slid

e —

33/7

9



Orientation: Pressure/Rate Integral Functions

dqt

ttq Dd

Dd

DdDdDdi )(

0 1)(

)( )( DdDdiDd

DdDdDdid tqdt

dttq

dpt

ttp Dd

Dd

DdDdDdi )(

0 1)(

)( )( DdDdiDd

DdDdDdid tpdt

dttp

Dimensionless pressure/rate integral decline functions:

Dimensionless pressure/rate integral derivative decline functions (analog to well testing derivative function):



Slid

e —

34/7

9



Orientation: -Integral-Derivative (Derivation)

)()( )]([

DdDdiDdDdid

DdDdi tqtqtq

)( )( 1

)(1 )( 0

)(

1

)(

2

DdDdiDdDdDd

DdDdDd

DdDd

Dd

DdDdiDd

tqtqt

tqt

dqt

t

tqdt

d

)( )(

1

]ln[

)](ln[

)]([

DdDdiDd

DdDdDdi

DdDdDdi

DdDdi

tqdt

dttq

tdtqd

tq

Steps:1. Derivative of rate

integral function with respect to time function.

2. Use the power-law formulation for the derivative.

3. Obtain the -deriva-tive using rate and rate integral func-tions.

4. Or obtain the -derivative using rate integral and rate integral derivative (well test analog) functions.

)()(1)]([

DdDdiDdDd

DdDdi tqtqtq or

-integral derivative representation

"Well testing derivative"

Derivative of data w.r.t. time



Slid

e —

35/7

9



●Rate -Integral-Derivative "Diagnostic Plot": Unfractured and fractured well configurations — note the distinction of "transition" flow regimes that the [qDdi(tDd)] function provides. Analog of decline type curve analysis.

Orientation: "Type Curve" Representations

10-3

10-2

10-1

100

101

102

103

10-5 10-4 10-3 10-2 10-1 100 101 102 103

Dimensionless Material Balance Decline Time, tDd,bar=NpDd/qDd

Legend: (qDdid ) ([qDdi] ) Unfractured Well (Radial Flow) Fractured Well (Finite Fracture Conductivity) Fractured Well (Elliptical Reservoir)

Transient Flow Region

Schematic of Dimensionless Rate Integral Derivative FunctionsVarious Reservoir Models and Well Configurations (as noted)

DIAGNOSTIC plot for Production Data (qDdid and [qDdi] )

Dim

ensi

onle

ss R

ate

Inte

gral

Der

ivat

ive

Func

tion,

qD

did

"Pow

er L

aw —

"

Dim

ensi

onle

ss R

ate

Inte

gral

Der

ivat

ive

Func

tion,

[q

Ddi

]

Boundary-Dominated

Flow Region

[qDdi] ~ 1.0(boundary

dominated flow)

1

1

1

2

Unfractured Well ina Bounded Circular

Reservoir

Fractured Well ina Bounded Elliptical

Reservoir(Finite ConductivityVertical Fracture)

Fractured Well ina Bounded Circular

Reservoir(Finite ConductivityVertical Fracture)

( )( )

( )( )

( )( )

NO Wellbore Storage or Skin Effects

[qDdi] = 0.5(linear flow)

Plotting Functions:[(qDdi(tDd)] versus Np/qo:(Rate -Integral-Derivative)

[(qDdi(tDd)] =(?) IARF → k+s(1/4) Fin. Con. → FcD(1/2) Inf. Con. → xf(?) Horizontal → ?(1) BDF → N

The primary utility of the -integral-derivative is the resolution that this function provides for cases where the pressure drop/rate can be represented by a power-law function.



Slid

e —

36/7

9



●SPE 84287 "History Plot": Daily production rate and pressure data used for production and well test analysis. Excellent quality data. Note the effect of shut-ins and daily fluctuations.

Field Examples: East Tx Gas Well (SPE 84287)



Slid

e —

37/7

9



●Discussion (Diagnostic Plot):■ Excellent performance of [qDd(tDd)] data function (fractured well model). ■ Very-low k, very long transition to boundary-dominated flow.■ "Average" analysis results: k ≈ 0.00554 md, xf ≈ 290 ft, Gp ≈ 1.586 BSCF.




Slid

e —

38/7

9



●Discussion (Analysis by Modeling):■ Very good overall history match of the generated responses and raw data.■ Analysis results are very close to original results [Pratikno, et al 2003].




Slid

e —

39/7

9



Excerpts from:

CIPC 2007-174Production Data Analysis — Future

Practices for Analysis and Interpretation

D. Ilk, Texas A&M U.L. Mattar, Fekete Associates, Inc.

and T.A. Blasingame,* Texas A&M U.*Department of Petroleum Engineering


+1.979.845.2292 — [email protected](12 June 2007)

Canadian International Petroleum Conference Production Data Analysis — Future Practices for Analysis and Interpretation

Ilk/Mattar/Blasingame

Slid

e —

40/7

9



Meet the Family… (CIPC 2007-174)ILK, Dilhan MATTAR, Louis BLASINGAME, Tom

(aka: "The Kid") (aka: "The Wizard") (aka: "El Guerrero")

"Only the wisest and stupidest of men never change."

Confucius

"The straight line leads to the downfall of humanity."

F. Hundertwasser

"Happiness... it lies in the joy of achievement, in the thrill of creative effort."

Vincent van Gogh

(12 June 2007) Canadian International Petroleum Conference

Production Data Analysis — Future Practices for Analysis and InterpretationIlk/Mattar/Blasingame

Slid

e —

41/7

9



Rationale For This Work●Current methods are SUFFICIENT for:— Diagnostics (identification of reservoir model)— Analysis (variety of models, well conditions, etc.)— Modeling (very good to outstanding options)

●Tools we will need shortly (or even NOW).— Data handling (very large data sets, poor data)— Better diagnostics (more information from data)— Analysis (self-checking/correlation of q and pwf)— Modeling (merger of analytical/numerical models)

"Tell us what you want, and we will paint it … the way we see it"

Anonymous



Slid

e —

42/7

9



Modern PA: Generic PA Analysis Procedure●Procedure:

Step 1: Data Review → Review "Production History Plot" for data quality/correlation.

Step 2: Data Review → Data correlation check (pwf (or ptf) vs. rate plot). Crude comparison, only for general trends.

Step 3: Clean/Edit Data for Clarity → Remove spurious data from log-log data plots used for diagnosis.

Step 4: Identify Flow Regimes (Diagnostics) → Identify character-istic flow regimes using normalized PI/Blasingame plots.

Step 5: Compare Data to Reservoir Model → Use "Type Curves" to compare/match the data with a reservoir model.

Step 6: Refine Model Parameters → Improve match of model parameters (k, s, xf, FcD, ...) using individual type curves, simulation models, and/or regression methods.

Step 7: Summary History Match → Final "history match" of model and raw well performance data (pwf and q).



Slid

e —

43/7

9



Field Examples: Mid-Continent Gas WellStep 1 Step 2

Step 3●Diagnostic Data Analysis Plots:

■ Good quality data, unusual in that the production is limited (Step 1).

■ pwf and qg data appear to be only correlated at early times (Step 2).

■ The (qg/pp) trend is corrupted due to the cyclical series of production/ shut-in sequences (these data must be edited for diagnostic purposes) (Step 3).



Slid

e —

44/7

9



Field Examples: Mid-Continent (US) Gas WellStep 4a Step 5a

Step 6a●Log-Log Analysis: (fractured well)

■ Two possible scenarios for the reservoir model (radial flow or damaged fractured well) (Step 4a).

■ Type curve match using high conductivity elliptical flow solution (poor early time match) (Step 5a).

■ -integral-derivative does not match at early times, depletion flow is confirmed (Step 6a).



Slid

e —

45/7

9



Field Examples: Mid-Continent (US) Gas WellStep 4b Step 5b

Step 6b

●Log-Log Analysis: (unfractured well)■ Two possible scenarios for the

reservoir model (radial flow or damaged fractured well) (Step 4b).

■ Very good match with the unfrac-tured well model (well behaves as if it were not stimulated) (Step 5b).

■ -integral-derivative confirms that formation damage/poor stimulation is likely (Step 6b).



Slid

e —

46/7

9



Field Examples: Mid-Continent (US) Gas Well

●Summary History Match: (unfractured well)■ An extraordinary "history match" of the rate and pressure is obtained

using the unfractured well in bounded circular reservoir (Step 7).■ Rate and pressure measurements are considered precise.

Step 7b



Slid

e —

47/7

9



Excerpts from:

SPE 110187Evaluating the Impact of Waterfrac

Technologies on Gas Recovery Efficiency: Case Studies Using Elliptical

Flow Production Data AnalysisD. Ilk,* Texas A&M U.

J.A. Rushing, Anadarko Petroleum Corp.R.B. Sullivan, Anadarko Petroleum Corp.

and T.A. Blasingame, Texas A&M U.*Department of Petroleum Engineering


+1.979.458.1499 — [email protected] Annual Technical Conference and Exhibition — Anaheim, CA — 11-14 November 2007

SPE 110187 — Evaluating the Impact of Waterfrac Technologies on Gas Recovery Efficiency: Case StudiesUsing Elliptical Flow Production Data Analysis (Ilk/Rushing/Sullivan/Blasingame)

D. Ilk — Texas A&M U. (12 November 2007)

Slid

e —

48/7

9



Rationale For This WorkThe primary objectives of this study are:–To assess the stimulation effectiveness, and–To compare recovery efficiencies

… of the various "waterfrac" technologies used in the Bossier tight gas sand play (East Texas Basin, US).

Utilized a set of decline type curves developed for the

analysis of production data acquired from the elliptical flow

period commonly observed in hydraulically-fractured wells

completed in tight gas sands.[SPE 106308 (2007)]

SPE Annual Technical Conference and Exhibition — Anaheim, CA — 11-14 November 2007SPE 110187 — Evaluating the Impact of Waterfrac Technologies on Gas Recovery Efficiency: Case Studies

Using Elliptical Flow Production Data Analysis (Ilk/Rushing/Sullivan/Blasingame)D. Ilk — Texas A&M U. (12 November 2007)

Slid

e —

49/7

9



Rationale For This WorkTo find the proper balance between:–Well spacing,–Selection of stimulation treatment, and –Gas recovery efficiency.

We have evaluated the production performance for 12 wells where different types of stimulations were used.Our overall goal is to improve the correlation between

the well spacing and the creation of optimal hydraulic fractures (fracture length and conductivity).



Slid

e —

50/7

9



Case Studies: Small Waterfrac — 20/40 Proppant

●Discussion: Diagnosis of the Well Performance Data■ A consistent character in the rate and pressure functions is observed

— qg and pwf data correlation appears to be good to very good.■ qg/pp diagnostic functions appear to be relevant — earliest third of

data appear off-trend (weak qg and pwf correlation at early time?).■ Treatment — 7745 bbls of slick water; 63,000 lbs 20/40 proppant.

■ Diagnostic log-log plot (dimensionless rate decline and rate decline integral functions).

■ Production history plot (daily flowrate and pressure measurements).



Slid

e —

51/7

9



Case Studies: Small Waterfrac — 20/40 Proppant

●Discussion: Analysis Results■ Discrepancy at early times is observed — probably an early-time artifact

(shape of integral-derivative), possibly some modest fracture damage.■ Excellent match of the model and the rate history, good match of the

pressure history — "balance" of analysis between the diagnostic functions and the production history.

■ k=0.0097 md, xf=129 ft, FE=10, o=2.0 (near-circular), G=1.28 BSCF.

■ Production history plot with model match (excellent flowrate match, good pressure match).

■ Elliptical boundary decline type curve match (moderate conductivity, near-circular drainage geometry).



Slid

e —

52/7

9



Case Studies: Large Waterfrac — 40/70 Proppant

●Discussion: Diagnosis of the Well Performance Data■ Very good rate and pressure correlation (perhaps excellent!), with little

(apparent) mismatch is observed (all major features observed in the flowrates are observed in the pressures, and vice-versa).

■ Very strong data trends — transient signature suggests (very) low fracture conductivity (1/4 slope). Boundary-dominated flow is evident.

■ Treatment — 12,545 bbls of slick water; 254,600 lbs 40/70 proppant.





Slid

e —

53/7

9



Case Studies: Large Waterfrac — 40/70 Proppant

●Discussion: Analysis Results■ Excellent match of the qg/pp functions with a vertical fracture of (very)

low conductivity in an elliptically bounded reservoir system.■ (Very) poor pressure match at early times, under prediction of the

flowrate during this time — can attempt an improved match by a slight increase in fracture conductivity. Fair match of pwf data and model.

■ k=0.0118 md, xf=212 ft, FE=1, o=1.50 ("fat" ellipse), G=2.97 BSCF.

■ Production history plot with model match (very good flowrate match, acceptable/poor pressure match).

■ Elliptical boundary decline type curve match (very high conductivity, "fat" elliptical drainage geometry).



Slid

e —

54/7

9



Case Studies: Hybrid Waterfracs

●Discussion: Diagnosis of the Well Performance Data■ Erratic nature of the flowrate profile is seen (liquid loading). Major

features of the liquid loading observed for the flowrate data are reasonably well-correlated with the calculated bottomhole pressures.

■ Very clear diagnostic trends are obtained after judicious editing of the qg/pp function (1/2 slope during transient flow, 1/1 slope for BDF).

■ Treatment — 2082 bbls of slick water + 4827 bbls of cross-link gel; 510,140 lbs 20/40 proppant.





Slid

e —

55/7

9



●Discussion: Analysis Results■ Extraordinary "type curve match" is observed for this case — the well

is effectively stimulated and a low reservoir permeability is expected.■Model flowrate response corresponds well with the observed flowrate

data. The pressure match is not as poor as it might seem given the very erratic nature of the flowrate function.

■ k=0.0030 md, xf=200 ft, FE=1000, o=1.00 ("thin" ellipse), G=1.60 BSCF.

■ Production history plot with model match (very good flowrate match, acceptable pressure match).

■ Elliptical boundary decline type curve match (very high conductivity, "thin" elliptical drainage geometry).

Case Studies: Hybrid Waterfracs



Slid

e —

56/7

9



Case Studies: Discussion of Results

●Discussion: Effect of the Contacted Gas-In-Place■ Expectation — higher reservoir permeabilities, higher contacted gas-

in-place estimates.■Most small waterfrac cases are off-trend (a single on-trend point with

high permeability and high contacted gas-in-place estimate is noted).■ Excellent correlation of contacted gas-in-place with fracture half-

length — confirming that "the fracture defines the reserves."

■ Results correlation plot — G versus xf.■ Results correlation plot — G versus k.



Slid

e —

57/7

9



Society of Petroleum Engineers — Applied Technology WorkshopAnalysis of Reservoir Performance — Future View

07-09 February 2007 — Pier House Resort — Key West, Florida (USA)

Thomas A. Blasingame, Texas A&M U.Department of Petroleum Engineering



Excerpts from:Production Analysis —

What Will it Taketo Become Common Practice?

Analysis of Reservoir Performance — Future ViewSociety of Petroleum Engineers — Applied Technology Workshop

Production Analysis — What Will it Take to Become Common Practice?T.A. Blasingame — Texas A&M U. (09 February 2007)

Slid

e —

58/7

9



Engineering Assessment of ReservesTheoretical/Empirical Methods








Slid

e —

59/7

9



SPE 84287 — East TX Gas Well 1 (Low Permeability Gas)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0

100,

000

200,

000

300,

000

400,

000

500,

000

600,

000

700,

000

800,

000

900,

000

1,00

0,00

0

1,10

0,00

0

1,20

0,00

0

1,30

0,00

0

Cumulative Gas Production, MSCF

Gas

Pro

duct

ion

Rat

e, M

SCFD Cumulative Gas Production

Exponential ModelHyperbolic Model

SPE 84287 — East TX Gas Well 1 (Low Permeability Gas)

1.E+02

1.E+03

1.E+04

1.E+05

0 25 50 75 100

125

150

175

200

225

250

275

300

325

350

Producing Time, days

Gas

Pro

duct

ion

Rat

e, M

SCFD

0250500750100012501500175020002250250027503000

Flow

ing

Tubi

ng P

ress

ure,

psi

gGas FlowrateExponential Rate ModelHyperbolic Rate ModelWellbore Pressure

Q. What are the "Arps" rate-time/cumulative-time relations?A. Sequence of relations for production extrapolation (with time).

Reserves Estimation: Arps Rate-Time Relations

(oil: p>pb)

(gas: ≈ )



Slid

e —

60/7

9



Q. What is the "Carter" Decline Type Curve, and how is it used?A. A numerically-generated gas rate solution (pwf=con) — used as a "type

curve" (data overlay) to estimate reservoir properties.

Reserves Estimation: Fetkovich-Carter TC—

From

: Car

ter,

R.D

.: "T

ype

Cur

ves

for F

inite

Rad

ial a

nd

linea

r Gas

Flo

w S

yste

ms:

Con

stan

t Ter

min

al P

ress

ure

Cas

e,"

SPE

J(O

ctob

er 1

985)

719

-728

.

Transient Stems: (left)Numerical flow model

(pwf = con).q(t) is concave up.Depletion Stems: (right)q(t) is concave down.b=0: pwf = con.b=1: qo = con. (qo/p).b>1: transient flow or

external drive energy.: numerical gas flow

cases ( =f(pwf/(pi)).Reservoir Properties:k — y-axis match.G — x&y-axis matches.s — reD match.

swwa

wae

gigi

wfiDd

wae

wewtigi

Dd

err

rrB.

ppkhtqq

rr

rrrc

kt.t

21ln 2141

)( )(

21ln 1

21

1 006330 22

Variables for the Carter Decline Type Curve

—Fr

om: F

etko

vich

, M.J

.: "D

eclin

e C

urve

Ana

lysi

s U

sing

Typ

e C

urve

s,"

JPT

(Jun

e 19

80) 1

065-

1077

.



Slid

e —

61/7

9



Q. What are the rate-cumulative relations?A. Relations for reserves extrapolation.

Reserves Estimation: Rate-Cumulative Relations



Slid

e —

62/7

9



Reserves Estimation: "Hyperbolic Plot"

Discussion: Hyperbolic PlotsConcept? (verify the "hyperbolic" nature of the production data)Application? (interactive plots used in conjunction with other methods)



Slid

e —

63/7

9



1. Loss Ratio: (empirical — Arps (1942)) After Integration:

2: Camacho and Raghavan: (p<pb) (SPE 19009)

Q. Can the "hyperbolic" rate-time relation be derived?A. Sort of....

Reserves Estimation: q(t)=qi 1/[(1+Dit)^(1/b)]

dtdqq

dtd

Ddtda

dtdb

/1

)1()(1 b/i

itbD

qq



Slid

e —

64/7

9



Modern Production Data AnalysisA Complete Example








Slid

e —

65/7

9



PA Example: log(qg) and pwf vs. Time



Slid

e —

66/7

9



PA Example: log(qg) vs. Time (with rate extrapolations)



Slid

e —

67/7

9



PA Example: qg vs. Gp (with rate extrapolations)



Slid

e —

68/7

9



PA Example: Arps Hyperbolic Type Curves



Slid

e —

69/7

9



PA Example: pwf vs. qg Crossplot (quality check)



Slid

e —

70/7

9



PA Example: Normalized Log-Log Plot (model match)



Slid

e —

71/7

9



PA Example: "Blasingame" Log-Log Plot (model match)



Slid

e —

72/7

9



PA Example: PTA (match/comparison)



Slid

e —

73/7

9



PA Example: Summary Plot



Slid

e —

74/7

9



Production Data AnalysisWhat remains…








Slid

e —

75/7

9



Discussion: Future Work in PTA/PAAdditional reservoir/well models. (elliptical flow, moving boundary, ...)Full incorporation of PVT character. (volatile oil, gas condensate, ...)Reservoir scaling for PTA/PA. (scaling of petrophysical data?)Handling poor quality rate/pressure data. (major issue present/future)Continuously measured pwf and q data. (high frequency rates?)Multiple well analysis (integration). (analytical (mat. bal.) or numerical)Coupling of analysis/interpretation (3D/3P models). (over-determined?)Evaluation of multilayer systems. (I thought we already did this?)PA is the tool for tight gas, but must have data. (management?)

What Remains: Future Work in PTA/PA

"Technology ... is a queer thing. It brings yougreat gifts in one hand, and it stabs you in theback with the other."

C.P. Snow (1905-1980)



Slid

e —

76/7

9









Take Away

Slid

e —

77/7

9



Take Away: Production Analysis GuidelinesGuidelines: Performance-Based Reservoir CharacterizationsREVIEW production data for consistency (allocations, accuracy, etc.).REVIEW well history, particularly recompletions/stimulations.PERFORM simplified analysis of production data (Arps, EUR, etc.).

REVIEW measured rate/pressures (quality check).PERFORM model-based analysis of production (and well test) data.

Slid

e —

78/7

9



Model-Based Production Analysis:Contacted gas-in-place increases with time. Helps to tie reservoir properties with performance.

Empirical Production Analysis:Reserves extrapolations wrong (except at late times). Suitable for a 1-2 year projection (not much more).

Gotchas:Data quantity and quality (frequency and accuracy). Failure to reference analysis to a reservoir model.

Take Away: Production Analysis in Tight Gas Sands

Slid

e —

79/7

9









End of Presentation

production data analysis in tight gas sandsblasingame)_pres_apc_tight_gas_conf.pdfproduction data...

Documents