1_4_calculation of acoustic bhp.ppt
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Echometer 3TRANSCRIPT
Acoustic Determination of Producing and Static
Bottomhole Pressures
Acoustic Determination of Producing and Static
Bottomhole Pressures
TWM Well Analyzer SeminarTWM Well Analyzer Seminar
Reference Papers: SPE 14254 and SPE 13810
Purpose of Performing anPurpose of Performing anAcoustic Fluid Level SurveysAcoustic Fluid Level SurveysPurpose of Performing anPurpose of Performing anAcoustic Fluid Level SurveysAcoustic Fluid Level Surveys
Well Performance and Potential AnalysisWell Performance and Potential Analysis
based on calculated bottom hole pressures.
Pump SubmergencePump Submergence Some operators shoot the well only to determine the amount of liquid above the pump. This is inefficient use of the fluid level information.
TWM Computes TWM Computes Wellbore Wellbore
Pressures from Pressures from liquid level surveyliquid level survey
Right HalfRight Half of BHP Tab ANSWERS THE of BHP Tab ANSWERS THE FOLLOWING QUESTIONS:FOLLOWING QUESTIONS:
Right HalfRight Half of BHP Tab ANSWERS THE of BHP Tab ANSWERS THE FOLLOWING QUESTIONS:FOLLOWING QUESTIONS:
1.1. What is the depth to the top of the liquid?What is the depth to the top of the liquid?
2.2. Does liquid exist above the pump?Does liquid exist above the pump?
3.3. What is the percentage of liquid in the annular fluid What is the percentage of liquid in the annular fluid
column?column?
4.4. Is gas flowing up the annulus? At what rate?Is gas flowing up the annulus? At what rate?
5.5. What are the pressures at the casing head, fluid level, What are the pressures at the casing head, fluid level,
pump intake and opposite formation ?pump intake and opposite formation ?
6.6. What is the pump submergence ?What is the pump submergence ?
BHP tab, page 111BHP tab, page 111
Bottom Hole PressuresBottom Hole PressuresBottom Hole PressuresBottom Hole Pressures
Annulus Fluid Distribution is a Function Annulus Fluid Distribution is a Function of Well’s Producing Conditionsof Well’s Producing Conditions
BHP is computed from fluid level BHP is computed from fluid level surveys taken with acoustic fluid level surveys taken with acoustic fluid level instruments.instruments.
BHP = BHP = Surface CasingSurface Casing Pressure + Pressure + Pressure due to the Pressure due to the columns of fluidscolumns of fluids in in the annulus.the annulus.
““The well is like a pressure gage with The well is like a pressure gage with a long stem”.a long stem”.
PBHPPBHP
PcasingPcasing
P g/lP g/l
Pressure Gradients for Common LiquidsPressure Gradients for Common Liquids
Fresh Water = 0.433 psi/ftFresh Water = 0.433 psi/ft
Field brine = 0.5 psi /ftField brine = 0.5 psi /ft
30API Oil = 0.38 psi/ft30API Oil = 0.38 psi/ft
10API Oil = 0.433 psi/ft10API Oil = 0.433 psi/ft
GeneralizationsGeneralizations
3 ft of oil column = 1 psi3 ft of oil column = 1 psi
2 ft of brine column = 1 psi2 ft of brine column = 1 psi
Column Pressure CalculationsColumn Pressure Calculations
Pgc = gas column pressure, psiPgc = gas column pressure, psi
Pc = casinghead pressure, psiPc = casinghead pressure, psi
L = height of gas or liquid column, feetL = height of gas or liquid column, feet
Accurate BHP Calculation Requires:Accurate BHP Calculation Requires:Accurate BHP Calculation Requires:Accurate BHP Calculation Requires:
StabilizedStabilized flow conditions flow conditions Determination of Liquid LevelDetermination of Liquid Level Measurement of casing pressureMeasurement of casing pressure Measurement of casing pressure buildup rate Measurement of casing pressure buildup rate
(at Producing and Static Conditions)(at Producing and Static Conditions) Oil, water and annular gas densitiesOil, water and annular gas densities Wellbore descriptionWellbore description
StabilizedStabilized flow conditions flow conditions Determination of Liquid LevelDetermination of Liquid Level Measurement of casing pressureMeasurement of casing pressure Measurement of casing pressure buildup rate Measurement of casing pressure buildup rate
(at Producing and Static Conditions)(at Producing and Static Conditions) Oil, water and annular gas densitiesOil, water and annular gas densities Wellbore descriptionWellbore description
Stabilized PBHPStabilized PBHPStabilized PBHPStabilized PBHP
Requires a Requires a Constant Constant Production Rate and WORProduction Rate and WOR
Requires a Requires a StableStable Casing Casing PressurePressure
Requires a Requires a StableStable Fluid Fluid Level Level
Gas
BrineGradient
Oil + Gas
Pump
Pc
Pt
PBHP
FL
Gas
BrineGradient
Oil + Gas
Pump
Pc
Pt
PBHP
FL
Separation of Fluids Separation of Fluids in a Stabilized Wellin a Stabilized Well Separation of Fluids Separation of Fluids in a Stabilized Wellin a Stabilized Well
TheThe Liquid above the pump Liquid above the pump intake is 100% OIL regardless of intake is 100% OIL regardless of well test water-oil-ratio .well test water-oil-ratio .Oil gradient: 3ft = 1 psiOil gradient: 3ft = 1 psi
Liquid below pump intake contains Liquid below pump intake contains more water than well test water-oil-more water than well test water-oil-ratio.ratio.
LiquidLiquid below pump intake exhibits below pump intake exhibits BRINE gradient.BRINE gradient.
Brine gradient: 2 ft = 1 psiBrine gradient: 2 ft = 1 psi
Downhole Video Shows:Downhole Video Shows:
Effect of oil slip velocity on water Effect of oil slip velocity on water holdup causes water to holdup causes water to accumulate below pump intake.accumulate below pump intake.
Effect of wellbore inclination on Effect of wellbore inclination on oil/water and gas/liquid oil/water and gas/liquid distribution.distribution.
Flow from perforations is not Flow from perforations is not uniform.uniform.
Fluid Distribution in Annulus of Pumping WellsFluid Distribution in Annulus of Pumping Wells
Gas Gradient
Liquid Gradients
Gas & Liquid Mixture Gradients
Liquid Level at FormationLiquid Level at Formation
1. Casing Head Pressure is the 1. Casing Head Pressure is the Major PortionMajor Portion of of PBHPPBHP..
2. Pressure due to Gas Column is 2. Pressure due to Gas Column is Generally SmallGenerally Small
3. Pump intake and liquid level 3. Pump intake and liquid level are near perforations.are near perforations.
Liquid Level Above Formation with Liquid Level Above Formation with NO Free Gas Inflow from the ReservoirNO Free Gas Inflow from the Reservoir
1. Liquid above tubing intake is1. Liquid above tubing intake is 100% oil..
2. Producing BHP = 2. Producing BHP =
Casing Pressure +Casing Pressure +
Gas Columm Pressure+Gas Columm Pressure+
Oil Gradient to Pump +Oil Gradient to Pump +
Primarily Primarily Water gradientgradient below pump intake.below pump intake.
No Free Gas in Annulus LiquidNo Free Gas in Annulus LiquidNo Free Gas in Annulus LiquidNo Free Gas in Annulus Liquid
The Operator Closes the The Operator Closes the Casing Valve and the Casing Valve and the Casing Pressure Casing Pressure does not does not increase.increase.
Or the Casing Pressure is Or the Casing Pressure is less less than the Flowline than the Flowline Pressure.Pressure.
Gas
BrineGradient
Oil
Pump
Pc
Pt
PBHP
FL
Oil,Water,Gas
Gas
BrineGradient
Oil
Pump
Pc
Pt
PBHP
FL
Oil,Water,Gas
When:When:When:When:
100 % Liquid below Fluid Level
Liquid Level Above Formation Liquid Level Above Formation with Free Gas Flow from Perforationswith Free Gas Flow from Perforations
1.1. GaseousGaseous Liquid Column exists Liquid Column exists above the Perforations.above the Perforations.
2. Producing BHP = 2. Producing BHP =
Casing Pressure +Casing Pressure +
Gas Column Pressure +Gas Column Pressure +
Gaseous Oil Gaseous Oil Pressure to Pump +Pressure to Pump +
Gaseous WaterGaseous Water Pressure to bottom. Pressure to bottom.
Annular Gaseous Liquid Column ExistsAnnular Gaseous Liquid Column ExistsAnnular Gaseous Liquid Column ExistsAnnular Gaseous Liquid Column Exists
Gas is Gas is flowingflowing out from the out from the casing annulus.casing annulus.
The Casing pressure The Casing pressure builds builds upup when the casing valve is when the casing valve is closed.closed.
Gas
Liquid + GasPerfs
Pump
Flowline
Pc
Pt
Gaseous LiquidColumn
Dip Tube
When:When:When:When:
Gas enters through perforations and is Gas enters through perforations and is bubbling through annular liquid from bubbling through annular liquid from perforations to gas/liquid interface.perforations to gas/liquid interface.
Producing BHP CalculationProducing BHP Calculation
Requires measuring the fluid level and casing pressure
Requires determining pressure gradient of gaseous liquid column. ( density of gas-liquid mixture in wellbore)
Pressure gradient of gaseous liquid column depends mainly on % liquid
Determination of Gaseous Liquid Column GradientDetermination of Gaseous Liquid Column Gradient
Determined experimentally on a given well by Determined experimentally on a given well by running liquid level depression test.running liquid level depression test.
Develop experimental correlation from large Develop experimental correlation from large number of tests and apply to measured number of tests and apply to measured pressure and gas flow rate.pressure and gas flow rate.Reference: “Acoustic Producing BHP”Reference: “Acoustic Producing BHP”
Computed from mechanistic modelComputed from mechanistic model(not practical in most cases)(not practical in most cases)
Liquid % from Liquid Level Depression TestLiquid % from Liquid Level Depression Test
Given:Given: Constant ProductionConstant Production Annular Gas RateAnnular Gas Rate Annular AreaAnnular Area Fluid PropertiesFluid Properties
Determine Liquid Determine Liquid Percent in Gaseous Percent in Gaseous Liquid ColumnLiquid Column
Gas
Low PBHPPerfs
Pump
Flowline
Pc
Pt
Gaseous LiquidColumn with 10 - 15%Liquid
HighFL
Back Pressure Valve
Back Pressure Test SetupBack Pressure Test Setup
Basis for Experiment: Increase Pressure => Depress Liquid Level
Basis for Experiment: Increase Pressure => Depress Liquid Level
2300 ft2300 ft
Pressure increase = 220 psiPressure increase = 220 psi
Fluid Level Fluid Level Drop 2300 ftDrop 2300 ft
Gradient= 220/ 2300 = Gradient= 220/ 2300 = 0.095 psi/ft0.095 psi/ft
Pressure versus Depth Traverse in the AnnulusPressure versus Depth Traverse in the Annulus
0
2000
4000
6000
8000
10000
12000
14000
0 100 200 300 400
Pressure, psiD
epth
, fe
et
Pc=30 Pc=250
Gradient is computed from measured pressures and levels
Gradient is computed from measured pressures and levels
PPLL1LL1
PPLL2LL2
Back Pressure Test SetupBack Pressure Test Setup
Back Pressure Regulator LoopBack Pressure Regulator Loop
Back Back Pressure Pressure RegulatorRegulator
Automatic Annular Liquid Level and Casing Pressure MonitoringAutomatic Annular Liquid Level and Casing Pressure Monitoring
Remote Remote Fired Gas Fired Gas Gun and Gun and Pressure Pressure TransducerTransducer
Procedure for Liquid % TestProcedure for Liquid % TestProcedure for Liquid % TestProcedure for Liquid % Test
1.1. Maintain Well at Normal Maintain Well at Normal Pumping Conditions.Pumping Conditions.
2.2. Obtain Liquid Level Depth Obtain Liquid Level Depth and the Casing Pressure.and the Casing Pressure.
3.3. Increase casing pressure Increase casing pressure with back pressure regulator with back pressure regulator and allow well to stabilize.and allow well to stabilize.
4.4. Obtain Obtain NEWNEW Liquid Level Liquid Level Depth at NEW Casing Depth at NEW Casing Pressure.Pressure.
5.5. Repeat Steps 3 & 4, until Repeat Steps 3 & 4, until Liquid Level is Near Pump.Liquid Level is Near Pump.
Casing Pressure Casing Pressure and Liquid Level and Liquid Level During Liquid During Liquid Level Depression Level Depression Test.Test.
Pumping rate is Pumping rate is kept constant kept constant during test.during test.
Casing Pressure Casing Pressure and Liquid Level and Liquid Level During Liquid During Liquid Level Depression Level Depression Test.Test.
Pumping rate is Pumping rate is kept constant kept constant during test.during test.
Gaseous Column Height vs. Casing Pressure for 150 MCF/D in 5” & 2-7/8”Gaseous Column Height vs. Casing Pressure for 150 MCF/D in 5” & 2-7/8”
Annular Annular Gaseous Gaseous
Liquid Column Liquid Column Effective Effective Liquid Liquid
FractionFraction vs. vs.
Q/A or Q/A or (dp/dt)*D(dp/dt)*DLLLL
Annular Annular Gaseous Gaseous
Liquid Column Liquid Column Effective Effective Liquid Liquid
FractionFraction vs. vs.
Q/A or Q/A or (dp/dt)*D(dp/dt)*DLLLL
Actual Field Collected Data Point
Preliminary heavy oil data
Annular Gas Flow – dP/dT MeasuredAnnular Gas Flow – dP/dT Measured
Close Casing Valve
Close Casing Valve
Casing Pressure increase as a function of time is a measure of casinghead gas flow rate
Casing Pressure increase as a function of time is a measure of casinghead gas flow rate
dPdP
dtdt
Gas flow into well = 45 MCF/D
Gas flow out= 45 MCF/D
Time = 0 Time = 4 min.
46.2 psi
49.4 psi
PBHP = 572.8 psi
Casing Valve Closed During Test
Calculation of annular gas flow rate is based on the increase in casing pressure per unit time during the casing pressure buildup test. Using the real gas law:
P1*V1 = Z1n1RT1 at time t1 and
P2*V2 = Z2n2RT2 at time t2 where in the well:
V1 = V2 = volume of annulus minus volume of liquid
T1 = T2 = average temperature
R = gas constant
P1 =initial casing pressure
P2 = pressure at end of casing buildup test
n2,n1 = number of moles of gas in annulus
Then solve for (n2-n1) which is the increase in gas mass during the time (t2-t1) and convert to standard cubic feet per day.
Gas Flow CalculationGas Flow Calculation
Requirements for Accuracy of dp/dt TestRequirements for Accuracy of dp/dt Test
Test should be short (2 to 10 minutes) so that inflow of gas and producing bottom hole pressure remain almost constant.
Measured casing pressure buildup vs. time should be linear indicating a constant gas rate.
ID of casing, OD of tubing and well depth data are correctly entered in well database.
Producing BHP and PIP - TWM ProgramProducing BHP and PIP - TWM Program
Equivalent Gas-Free Liquid HeightEquivalent Gas-Free Liquid HeightEquivalent Gas-Free Liquid HeightEquivalent Gas-Free Liquid Height
Gas
Low PBHPPerfs
Pump
Flowline
Pc
Pt
Gaseous LiquidColumn with 10 - 15%Liquid
HighFL
Gas
Low PBHPPerfs
Flowline
Pc
Pt
Gas-FreeLiquid
Gas FreeFL
“Remove” gas from annular fluid column
Gas Free Liquid - TWM ProgramGas Free Liquid - TWM Program
Static Bottom Hole Pressure, Static Bottom Hole Pressure, SBHP SBHP (Reference: “Acoustic Static BHP)(Reference: “Acoustic Static BHP)
Static Bottom Hole Pressure, Static Bottom Hole Pressure, SBHP SBHP (Reference: “Acoustic Static BHP)(Reference: “Acoustic Static BHP)
Driving Pressure available to Driving Pressure available to push the fluids to the wellborepush the fluids to the wellbore
Generally GUESSEDGenerally GUESSED
Need within +/- 15%Need within +/- 15%
Operator Should MeasureOperator Should Measure StaticStatic Fluid LevelFluid Level and Casing Pressure and Casing Pressure in wells shut-in for any reason.in wells shut-in for any reason.
TWMTWM or or AWP2000AWP2000 compute the compute the SBHPSBHP
Calculation of SBHPCalculation of SBHPCalculation of SBHPCalculation of SBHP
Gas
Brine
Oil
Pc
Pt
Static FL
Well Shut-in
SBHP
Static BHP = Static BHP =
Casing Pressure +Casing Pressure +
Gas Column Pressure +Gas Column Pressure +
Oil Column Pressure +Oil Column Pressure +
Water Column Pressure.Water Column Pressure.
Note: Fluids Segregated by GravityNote: Fluids Segregated by Gravity
WOR produced after shut-inWOR produced after shut-inWOR produced after shut-inWOR produced after shut-in
Cannot Accurately Predict Cannot Accurately Predict WOR during after-flow. WOR during after-flow.
Assume that during after flow the Assume that during after flow the WOR remains same as WOR remains same as measured by well test.measured by well test.
Gas
Brine
Oil
Pc
Pt
Static FL
Well Shut-in
SBHP
Program computes location of Program computes location of water/oil interface from wellbore water/oil interface from wellbore geometry and geometry and last measuredlast measured producing fluid levelproducing fluid level
Static Bottom Hole Pressure, Pump Intake near PerforationsStatic Bottom Hole Pressure, Pump Intake near Perforations
Liquid Level @ Pump Liquid Level Above Pump
For Improved Accuracy Static Bottom Hole Pressure: Push Liquid Level near PumpFor Improved Accuracy Static Bottom Hole Pressure: Push Liquid Level near Pump
1.1. Increase Casing Pressure Increase Casing Pressure while pumping.while pumping.
2.2. Push the Liquid Level to Push the Liquid Level to
the Pump Intake the Pump Intake before before shutting-inshutting-in the well. the well.
3.3. Shut-in well and monitor Shut-in well and monitor liquid level and casing liquid level and casing pressure.pressure.
Minimizes error due to uncertainty Minimizes error due to uncertainty of fluid gradient and WOR of fluid gradient and WOR
during afterflowduring afterflow..
Minimizes error due to uncertainty Minimizes error due to uncertainty of fluid gradient and WOR of fluid gradient and WOR
during afterflowduring afterflow..
Static Bottom Hole Pressure, Determination w/ High PumpStatic Bottom Hole Pressure, Determination w/ High Pump
Liquid Level @ Pump Liquid Level Above Pump
Determination of Accurate SBHPDetermination of Accurate SBHPDetermination of Accurate SBHPDetermination of Accurate SBHP
Well should be shut-in for a time sufficient to Well should be shut-in for a time sufficient to stabilize casing pressure and fluid level. stabilize casing pressure and fluid level.
Periodic fluid level measurements identify Periodic fluid level measurements identify stabilized conditions.stabilized conditions.
More accurate calculation of More accurate calculation of StaticStatic BHP BHP entering the entering the ProducingProducing Fluid Level, Casing Fluid Level, Casing Pressure, and Casing Pressure Buildup Rate Pressure, and Casing Pressure Buildup Rate before well is shut-inbefore well is shut-in into the SBHP into the SBHP worksheet.worksheet.
SBHP worksheet in TWM programSBHP worksheet in TWM program
% Liquid
Pressure Transient Test Best method for SBHP
Pressure Transient Test Best method for SBHP
Computed from CasingheadPressure, Annular Fluid Level andDensity of Gas and Fluid Columns
Computed from CasingheadPressure, Annular Fluid Level andDensity of Gas and Fluid Columns
Summary of Determining BHPsSummary of Determining BHPsSummary of Determining BHPsSummary of Determining BHPs StaticStatic and and ProducingProducing BHP can be determined BHP can be determined
from acoustic liquid level surveys.from acoustic liquid level surveys.
Accurate casing pressure and Accurate casing pressure and casing pressure casing pressure buildupbuildup rate determines % Liquid.rate determines % Liquid.
BHP = Surface Casing Pressure + Pressure from BHP = Surface Casing Pressure + Pressure from the column of fluids in the annulus.the column of fluids in the annulus.
Fluid Distribution is a Function of Well’s Fluid Distribution is a Function of Well’s Producing ConditionsProducing Conditions
Questions ?Questions ?Questions ?Questions ?