Analysis of Production Data - p663 03c Arp Lec 03 Wpa (031127)

(Formation Evaluation and the Analysis of Reservoir Performance)

Module for:Analysis of Reservoir PerformanceAnalysis of Production Data

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

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

(+1) 979.845.2292 [email protected] of Production Data Slide 1(27 November 2003)



Executive Summary




Executive Summary Presentation StructureOverview of Production Data AnalysisEquivalent Constant Rate Case

Material Balance Time (Oil and Gas)Normalized Rate Functions

Assumptions and LimitationsData RequirementsLiquid (Oil) and Gas (Generally Dry Gas)Miscellaneous

Library of Decline Type Curve ModelsVarious well and reservoir models

Example AnalysesComment and Closure

Analysis of Production Data Slide 3(27 November 2003)



Overview of Production Data Analysis




Overview of Production Data AnalysisHistorical Developments

PerspectivesEarly reserves estimation plotsEarly decline curve analysis

Evolution of Decline Type Curve AnalysisArps' exponential and hyperbolic relationsDimensionless rate-time plot (constant pressure)Dimensionless decline type curves (liquid and gas)

Rigorous Analysis of Production DataFull superposition (van Everdingen-Meyer method)Analogy/synthesis with analysis of well test data

Production Data Analysis Future IssuesData, models, integration, simulation, control...


Production Data Analysis: History Lessons (1/4)Origin of technology:

Early 1900's estimate well deliverability and reserves."Reservoir characterization" did not evolve until 1950's.

Relevance:Pressure transient testing is a "high frequency/high resolu-tion" data analysis technique.Production data analysis re-mains a "crude data" technique.Data quantity/quality issues will always be an issue.

From: Dealing with the Idiots in Your Life, J. Benton (1993).


Production Data Analysis: History Lessons (2/4)

From: Estimation of Underground Oil Reserves by Oil-Well Production Curves Cutler (1924).

From: Manual for the Oil and Gas Industry Arnold (1919).

Production decline analysis:Over 80 years old!Objective was economic, not technical production ex-trapolations were even referenced to the tax year!Very humble origins "whatever worked" plots seemed to be popular (e.g., Cartesian, log-log, and semi-log).



a. The "engineer's solu-tion" (i.e., the log-log plot) (did not stand the test of time plot).

b.The "gee it works" plot I wonder if there is some theory ... (yes).

c. The "scratch your head" plot ... interesting, but ... how does it work?

From: Estimation of Underground Oil Reserves by Oil-Well Production Curves Cutler (1924).



Arps' Relations for Decline Curve Analysis: (1944)Empirical, but even in 1944, Arps tried to relate to theory.Many products use these relations, must use regression.


Decline Type Curve Analysis: Evolution (1/5)

From: SPE 04629 Fetkovich (1973).

From: SPE-Transactions Arps (1944).

"Arps" decline analysis:Introduction of exponential and hyperbolic families of "decline curves" (Arps, 1944)Introduction of log-log "type curve" for the "Arps" family of "decline curves" (Fetko-vich, 1973).Empirical ... but seems to work as a general tool. Is this more coincidence or theory?

"Arps" curves should be used as an empirical tool particu-larly for estimating future per-formance and reserves.




"Analytical" rate decline curves:Data from van Everdingen and Hurst (1949), re-plotted as a rate decline plot (Fetko-vich, 1973).This looks promising but this is going to be one really big "type curve."What can we do? Try to col-lapse all of the trends to a single trend during boun-dary-domination flow (Fet-kovich, 1973).

"Analytical" stems are another name for transient flow beha-vior, which can yield estimates of reservoir flow properties.





Composite Transient Type Curve:Collapses the transient flow trends into "stems" related to reservoir size and skin factor (Fetkovich, 1973).

Composite Decline Type Curve:Addition of the "Arps" empirical trends for "boundary-dominated flow behavior (Fetkovich, 1973)."

Assumptions:Constant bottomhole pressure."Liquid" flow (not gas).

Comments on gas flow behavior:Fetkovich (and others) have noted that most gas cases lie on or near the stems for 0.4


Fetkovich "Composite" Decline Type Curve:Assumes constant bottomhole pressure production.Radial flow in a finite radial reservoir system (single well).


From: SPE 25909 Palacio, et al (1993).

From: SPE 12917 Carter (1985).

Gas Carter Type Curve:Correlation of gas well performance for varying levels of pressure drawdown (Carter, 1985).

Gas Fetkovich-McCray-Carter Type Curve:

Addition of new the "McCray" plotting functions (Palacio, et al, 1993).

Assumptions:Production at constant bot-tomhole pressure.



Production Analysis: Rigorous Approaches (1/3)

From: SPE 15482 Whitson and Sognesand (1988).

"Van Everdingen-Meyer Method:"Analysis by simulation" (use analytical solution to define x-axis plotting function.Considers all of the data, needs a complete model to generate an appropriate analysis/interpretation.Theoretically simple, practical.

Pro: Theoretically simple and practical (can use field data).Con: Limited by solution model as well as data quality.


From: SPE 56419 Athichana-gorn, Horne, and Kikani (1999).

Practically speaking..."Data on demand" will arrive.We may even have pressure.Today's tools can not handle the task of analysis and inter-pretation.

"Drowning in Data"Consider the case of pres-sure transient testing 10,000-100,000 data are now common.Production databases will be enormous...

Production Analysis: Rigorous Approaches (2/3)


Production Analysis: Rigorous Approaches (3/3) Consider a well test example:

Impossible to analyze all of the data...Use "windows" to analyze segments of the data.Surprise! The results are not the same from window to window but they are related (see histograms).

Good news: The statistics are relevant...Bad news: This is not as con-sistent as we would like...

From: SPE 56419 Athichana-gorn, Horne, and Kikani (1999).


From: School is Hell, M. Groen-ing, (1987).

Data analysis/interpretation:Improved acquisition.Integration of analytical and numerical tools."Event" analysis"Continuous" data analysis.

Good news: The tools (analyti-cal and numerical) will evolve.Bad news: The data burden will be tremendous, perhaps even overwhelming. Data quality may still be an issue.The purpose of analysis is to provide a basis for modelling and, in turn, modelling provides a basis for optimization and flow control.

Production Analysis: Future Issues




Equivalent Constant Rate CaseT.A. Blasingame, Texas A&M U.

Department of Petroleum EngineeringTexas A&M University

College Station, TX 77843-3116 (USA)(+1) 979.845.2292 [email protected]


Equivalent Constant Rate CaseMaterial Balance Time

"Converts" variable-rate/variable pressure drop data into "equivalent" constant rate case using a super-position formula based on boundary-dominated flow behavior.Liquid (oil) systems have a simple formulation based of the flowrate and cumulative production.Gas systems require a pseudotime function for the pressure-dependent gas properties.

Normalized Rate Functions(qo/p) (or (qg/pp) for gas)(qo/p)i (or (qg/pp)i for gas)(qo/p)id (or (qg/pp)id for gas)


Eq. Constant Rate Case: Material Balance TimeIntroduce the rigorous application of product-ion decline analysis using type curves: (vari-able-rate/variable pressure drop data)

Use time, pressure, flowrate (TPR) data .Analysis approach uses "material balance time" (forces late-time data onto the Arps b=1 stem).

o

pqN

t =

Oil Material Balance Time:

Gas M.B. Pseudotime: Gas Pseudopressure:

=

tdtpcp

tqq

ct

tgg

g

tigia

0 )()(

)(

=

p

pdp

zp

pz

pbase gi

igip


Eq. Constant Rate Case: Rate FunctionsThe normalized rate function (qo/p) (or (qg/pp) for gas) results from the superposition formula. The auxiliary functions ((qo/p)i (or (qg/pp)i) and (qo/p)id (or (qg/pp)id)) are used to provide "smoothness" and "character" to the data.Rate Function:(qo/p) (or (qg/pp) for gas)

Rate Integral Function:apg

t

aipgo

tio tdpqtpqtdpqt

pq a )/(1)/( or)/(1)/(00

== Rate Integral-Derivative Function:

|)/(| )/( or |)/(| )/( ipga

aidpgioido pqtddtpqpq

tddtpq ==


The well performance equations for the oil case are obtained by combining the material balance equation for a slightly compressible liquid and the pseudosteady-state flow equation. The pressure drop and flowrate results are:

Pressure Drop Form:tmb

qp

pssopssoo

,, +=

Well Performance Relations: Oil Case

Flowrate Form:

tmbpq

pssopssoo

,,

1 +

=

Where:

oio

tpsso B

BNc

m 1 , =

+

= s

rA

CekhBb

wAoo

psso 2,14ln

21 141.2


The gas well performance equations are ob-tained by combining the gas material balance equation and the pseudosteady-state flow equa-tion for gas. These results are given as:

Pressure Drop Form:

apssgpssgg

p tmbqp

,, +=

Well Performance Relations: Gas Case

Flowrate Form:

apssgpssgp

gtmbp

q

,,

1 +

=

Where:

=

tdtpcp

tqq

ct

tgg

g

tigia

0 )()(

)(

=

p

pdp

zp

pz

pbase gi

igip

tpssg Gc

m 1 , =

+

= s

rA

CekhB

bwA

gigipssg 2,

14ln 21 141.2




Assumptions and LimitationsT.A. Blasingame, Texas A&M U.




Assumptions and Limitations (1/4)Data Requirements

Good estimates of base PVT properties (black oil: T, sep, pb, STO and for dry gas: T, sep). OR, a fluid sample/report would be preferred (with the fluid sample taken early in the life of the reservoir.Accurate measurements/estimates of rate and pres-sure data. This is the key to the methodology random errors are "tolerable" gaps or other sys-tematic errors in the rate history are generally NOT acceptable.Estimates of porosity, net pay, wellbore radius, are necessary.A detailed documentation of the well completion history is very useful particularly when attempt-ing to resolve production anomalies.


Assumptions and Limitations (2/4)Liquid (Oil) Case

Only major issue/limitation is that of the appropriate value of total compressibility (ct). This value is used to estimate original oil-in-place (N), and we must recognize that ct changes as the reservoir depletes. In particular, the effect of reservoir pressure trend-ing below the bubblepoint pressure is a major issue.

Gas (i.e., Dry Gas) CaseRequires an estimate of initial gas-in-place, G.Generally yields good estimates of volumetric and flow properties.No major issues water/liquid loading has been seen to cause problems in the pressure data. Well cleanup also occasionally an issue (low permea-bility reservoir systems).


Assumptions and Limitations (3/4)Miscellaneous

This is data analysis methodology designed to be a single well analysis technique, it can be extended to the multiwell case, but this is not trivial and re-quires the production history for the entire field.


Assumptions and Limitations (4/4)

Compressibility/Mobility Plot: (pwf = constant)From Camacho-V., R.G. and Raghavan, R.: "Boundary-Domi-nated Flow in Solution-Gas-Drive Reservoirs," SPERE (No-vember 1989) 503-512.




Library of Decline Type CurvesT.A. Blasingame, Texas A&M U.




Decline Type Curve Analysis: Property EstimatesDecline type curve models are available for:

Unfractured vertical wells Vertical well (radial flow) case Waterflood" case

Fractured vertical wells Infinite Conductivity Vertical Fracture Finite Conductivity Vertical Fracture

Horizontal wellsThe proposed analysis and interpretation methods for decline type curve analysis provide estimates of:

Original Oil-in-Place/Drainage AreaReservoir Flow Characteristics: Formation Permeability Initial Skin Factor Fracture Half-Length Effective Horizontal Well Length Boundary Flux Parameters (possibly)


Library of Decline Type Curves: OrientationFetkovich Type Curves Radial Flow:

Original Fetkovich Decline Type Curve"Rate Derivative" Decline Type Curve

Fetkovich-McCray Type Curves Radial Flow:Fetkovich-McCray Type CurveFetkovich-Carter-McCray Type Curve (Gas) "Waterflood" Type Curves (Boundary Flux)"Well Interference" Type Curve (Boundary Flux)

Fetkovich-McCray Curves Fractured Wells:Infinite Conductivity Vertical FractureFinite Conductivity Vertical Fracture

Fetkovich-McCray Curves Horizontal WellsAgarwal, et al Methodology:

Radial Flow CaseVertically Fractured Well Cases


Library of Decline Type Curves: Fetkovich (1/3)

a. Palacio, et al (1993): "Fetkovich-McCray Original" (radial flow) includes auxiliary functions. (tDd format)

b. Doublet, et al (1994): "Fetkovich Derivative" (radial flow) not practical for analysis. (tDd format)

c. Doublet, et al (1994): "Fetkovich-McCray M.B. Time" (radial flow) includes auxiliary functions. (tDd,bar)

Decline Type Curves: Radial Flow"Fetkovich-McCray Original""Fetkovich Derivative""Fetkovich-McCray Material Balance" Uses material balance to rigorously incorporate varia-tions in rate and pressure over time. This technique substan-tially improves the analysis of variable-rate production data.



"Fetkovich-McCray" Type Curve for an Unfractured Well Production Time Format.


"Fetkovich-McCray" Type Curve for an Unfractured Well Material Balance Time Format.



c. Pratikno (2002): "Fetkovich-McCray" format FINITE conductivity vertical fracture (FcD=0.5).

a. Doublet, et al (1996): "Fetkovich-McCray" format INFINITE conductivity vertical fracture (FcD=).

b. Pratikno (2002): "Fetkovich-McCray" format FINITE conductivity vertical fracture (FcD=10).

Decline Type Curves: Fractured WellsInfinite fracture conductivity: Less complex solution, but

somewhat ideal for use in practice.

Finite fracture conductivity: FcD=10: Moderate to high fracture

conductivity case. FcD=0.5: Low fracture conducti-

vity case.

Library of Decline Type Curves: Doublet/Pratikno (1/4)



"Fetkovich-McCray" Type Curve for a Fractured Well (Infinite Conductivity) Material Balance Time Format.



"Fetkovich-McCray" Type Curve for a Fractured Well (FcD=10) Material Balance Time Format.



"Fetkovich-McCray" Type Curve for a Fractured Well (FcD=0.5) Material Balance Time Format.


Library of Decline Type Curves: Shih

From: SPE 29572 Shih, et al. (1995).


Horizontal Well Cases "Infinite-conductivity" horizontal well case(s).



Library of Decline Type Curves: Boundary

From: SPE 30774 Doublet, et al. (1995).

From: SPE 30774 Doublet, et al. (1995).

Decline Type Curve Analysis: "Break-glass-in-case-of-fire" cases

From: Unpublished Marhaendrajana (2000) (multiwell analysis do not use).


From: SPE 71517 Marhaendrajana (2001).


Multiwell AnalysisMultiwell case can be "recast" into single well case using cumulative production for entire field.Homogeneous reservoir example shows that all cases (9 wells) align same behavior observed for heterogeneous reservoir cases.


Library of Decline Type Curves: Multiwell


Library of Decline Type Curves: Agarwal, et al

From: SPE 57916 Agarwal, et al. (1998).


Agarwal, et al Methodology:Basically the same as Blasingame, et alwork.More like pressure transient test analy-sis/interpretation.



Library of Decline Type Curves: Crafton, et alCrafton, et al Methodology:

Rate normalized pressure drop versus production time (p/q versus t).Also analogous to pressure transient test analysis/interpretation.Very serious limitations production time is not sufficient for general case of rate variation.

From: SPE 37409 Crafton, et al. (1997) (Fig. 2).

From: SPE 37409 Crafton, et al. (1997) (Fig. 5). From: SPE 37409 Crafton, et al. (1997) (Fig. 10).




Examples




Example 1: Fetkovich Rate-Time Analyses

qg vs. t and Gp vs. t: Good data matches (a. and c.) data quality provides clear trends. "High" and "low" qi cases are +/-10 percent assist in orienting analysis in the spreadsheet.Note that production performance (i.e., rate data) is very consistent (semilog rate-time plot).

b. West Virginia Well A: log(qg) versus t (pi= 4175 psia, pwf=710 psia, Gquad=3.29 BSCF).

a. West Virginia Well A: log(qg) versus log(t) (pi= 4175 psia, pwf=710 psia, Gquad=3.29 BSCF).

c. West Virginia Well A: log(Gp) versus log(t) (pi= 4175 psia, pwf=710 psia, Gquad=3.29 BSCF).


Example 1: Fetkovich Decline Type Curve Analysis

Rate-Time Decline Type Curve: (Rigorous Analysis)West Virginia Well A (pi= 4175 psia, pwf=710 psia, Gquad=3.29 BSCF).Very clear trends all data functions.The estimate of gas reserves using rate-time decline type curve analysis is conservative, possibly/probably a result of the lack of pressure data.


Example 2: Horizontal Well Rate-Time Analyses

qg vs. t and Gp vs. t: Log(qg) vs. log(t) and log(qg) vs. tplots exhibit rate noise only during the 100-day "erratic rate" period.Log(Gp) vs. log(t) trend is very smooth and continuous through-out the entire production history.b. Well Heckmann 1: log(qg) versus t (pi 9000

psia, pwf=variable, Gquad=5.69 BSCF).

a. Well Heckmann 1: log(qg) versus log(t) (pi 9000 psia, pwf=variable, Gquad=5.69 BSCF).

c. Well Heckmann 1: log(Gp) versus log(t) (pi 9000 psia, pwf=variable, Gquad=5.69 BSCF).


Example 2: Horizontal Well Decline T.C. Analysis

Rate-Time Decline Type Curve: (Rigorous Analysis)Well Heckmann 1 (pi 9000 psia, pwf=variable, Gquad=5.69 BSCF).This is a horizontal well sparse early data does match type curve trends reasonably well.Good overall data match comparable estimate of gas-in-place (G).


Example 3: Womack Hill Field Well 1655

a. Production Data Plot for Well 1655 Womack Hill Field (Alabama).

c. EUR Plot for Well 1655 Womack Hill Field (Alabama).

b. Watercut Plot for Well 1655 Womack Hill Field (Alabama).

d. Decline Type Curve Match of Oil Rate Data for Well 1655 Womack Hill Field (Alabama).




Comment and ClosureT.A. Blasingame, Texas A&M U.




Reservoir Performance Analysis: Tools

From: Love is Hell, M. Groen-ing, (1984).

Production Analysis Tools:"Old" decline curve analysis.Decline type curve analysis.EUR analysisNumerical simulation.

On the horizon integrated data acquisition, analysis, and control.Issues:

What tools do we really want?What tools do we really need?Numerical modelling savior or villain?Data acquisition is the key.


Reservoir Performance Analysis: Reality CheckProduction data analyses and pressure transient analyses "see" the reservoir as a volume-averaged set of properties.New solutions/models will also have this view of the reservoir.It's only time-pressure-rate data, don't expect a miracle...The challenge of future work is to represent the behavior of the reservoir while also providing an understanding of the scale of reservoir features.

From: Simulator Parameter Assignment and the Problem of Scaling in Reservoir Engineering Halderson (1986).




End of PresentationT.A. Blasingame, Texas A&M U.




References: Reservoir Performance AnalysisHistorical Methods Production Data Analysis:

1. Arps, J.J: "Analysis of Decline Curves," Trans., AIME (1945) 160, 228-247.2. Fetkovich, M.J.: "Decline Curve Analysis Using Type Curves," JPT (June 1980) 1065-1077.3. Gringarten, A.C.: "Reservoir Limits Testing for Fractured Wells," paper SPE 7452 presented at the 1978 SPE Annual Technical

Conference and Exhibition, Houston, TX., 1-3 October.4. Carter, R.D.: "Type Curves for Finite Radial and linear Gas Flow Systems: Constant Terminal Pressure Case," SPEJ (October 1985)

719-728.Decline Type Curve Analysis:

1. Fraim, M.L., Lee, W.J., and Gatens, J.M., III: "Advanced Decline Curve Analysis Using Normalized-Time and Type Curves for Vertically Fractured Wells," paper SPE 15524 presented at the 1986 SPE Annual Technical Conference and Exhibition, New Orleans, LA, 5-8 October.

2. McCray, T.L.: Reservoir Analysis Using Production Decline Data and Adjusted Time, M.S. Thesis, Texas A&M U., College Station, TX (1990).

3. Palacio, J.C. and Blasingame, T.A.: "Decline Curve Analysis Using Type Curves Analysis of Gas Well Production Data," paper SPE 25909 presented at the 1993 Joint Rocky Mountain Regional/Low Permeability Reservoirs Symposium, Denver, CO, 26-28 April 1993.

4. Doublet, L.E., Pande, P.K., McCollum, T.J., and Blasingame, T.A.: "Decline Curve Analysis Using Type Curves Analysis of Oil Well Production Data Using Material Balance Time: Application to Field Cases," paper SPE 28688 presented at the 1994 Petroleum Conference and Exhibition of Mexico held in Veracruz, Mexico, 10-13 October 1994.

5. Shih, M.-Y. and Blasingame, T.A.: "Decline Curve Analysis Using Type Curves: Horizontal Wells," paper SPE 29572 presented at the 1995 Joint Rocky Mountain Regional/Low Permeability Reservoirs Symposium, Denver, CO, 20-22 March, 1995.

6. Doublet, L.E. and Blasingame, T.A.: "Evaluation of Injection Well Performance Using Decline Type Curves," paper SPE 35205 presented at the 1996 SPE Permian Basin Oil and Gas Recovery Conference, Midland, TX, 27-29 March 1996.

7. Crafton, J. W.: "Oil and Gas Well Evaluation Using the Reciprocal Productivity Index Method," paper SPE 37409 presented at the 1997 SPE Production Operations Symposium, held in Oklahoma City, Oklahoma, 9-11 March 1997.

8. Agarwal, R.G., Gardner, D.C., Kleinsteiber, S.W., and Fussell, D.D.: "Analyzing Well Production Data Using Combined Type Curve and Decline Curve Analysis Concepts," paper SPE 49222 prepared for presentation at the 1998 SPE ATCE, New Orleans, LA, 27-30 September 1998.

9. Marhaendrajana, T. and Blasingame, T.A.: "Decline Curve Analysis Using Type Curves Evaluation of Well Performance Behavior in a Multiwell Reservoir System," paper SPE 71514 presented at the 2001 Annual SPE Technical Conference and Exhibition, New Orleans, 30 September-03 October 2001.

10. Pratikno, H., Rushing, J.A., and Blasingame, T.A.: "Decline Curve Analysis Using Type Curves: Fractured Wells," paper SPE 84287 presented at the 2003 Annual SPE Technical Conference and Exhibition, Denver, CO., 05-08 October 2003.


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Analysis of Production Data - p663 03c Arp Lec 03 Wpa (031127)

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