After-Closure Analysis To Identify Naturally Fractured Reservoirs
- Simon T. Chipperfield (Shell Intl. E&P Inc.)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- February 2006
- Document Type
- Journal Paper
- 50 - 60
- 2006. Society of Petroleum Engineers
- 5.8.6 Naturally Fractured Reservoir, 5.6.4 Drillstem/Well Testing, 3 Production and Well Operations, 4.1.2 Separation and Treating, 2 Well Completion, 5.2 Reservoir Fluid Dynamics, 5.5.1 Simulator Development, 3.3.2 Borehole Imaging and Wellbore Seismic, 5.1 Reservoir Characterisation, 2.5.1 Fracture design and containment, 1.8 Formation Damage, 3.2.3 Hydraulic Fracturing Design, Implementation and Optimisation, 4.3.4 Scale, 5.1.1 Exploration, Development, Structural Geology
- 3 in the last 30 days
- 1,018 since 2007
- Show more detail
- View rights & permissions
|SPE Member Price:||USD 10.00|
|SPE Non-Member Price:||USD 30.00|
After-closure analysis (ACA) in homogeneous-matrix reservoirs provides a method for extracting critical reservoir information from pre-frac injection tests. This paper extends the theory and practice of ACA to identify the presence of productive natural fractures.
Natural fractures are important to identify before conducting a stimulation treatment because their presence may require designs that differ from conventional matrix treatments. Literature shows that naturally fractured reservoirs are very susceptible to formation damage and require stimulation treatments to account for this issue. The historical problem, however, has been to confidently characterize the reservoirs pre-frac in terms of both the reservoir quality and the deliverability mechanism (fractures vs. matrix) before committing to these design specifications.
This paper presents the results of a simulator used to analyze the mini-frac after-closure period to identify the presence of natural fractures. The simulation results are distilled into a field implementation methodology for determining the extent of natural fracturing and the formation reservoir quality. This methodology is also applied to a field case study to verify the practicality of the technique. Unlike previous mini-frac-analysis methods, this approach identifies natural fractures that are material to production and allows the engineer to distinguish them from "fissures?? that are open only during injection and are not a production mechanism.
Motivation for Identifying Natural Fractures. Identifying the presence of natural fractures is important for a broad range of reasons. On a field scale, realizing the presence of natural fractures can impact reserves estimation, initial well rates, production declines, and planned well locations. With respect to well completions, fractured reservoirs may necessitate a special stimulation approach. Because fractured reservoirs tend to produce from a relatively small reservoir volume (i.e., the fractures), these formations can be highly susceptible to damage (Cippolla et al. 1988). The literature shows that the use of foamed treatments (Cippolla et al. 1988), 100 mesh, and low gel loadings can be used to stimulate these reservoirs effectively. The literature also shows the disastrous results that can arise when damage-prevention steps are not taken (Cippolla et al. 1988). As a result, there is a definite need to identify natural fractures before a stimulation treatment so that the appropriate design decisions can be made.
In the past, conventional well testing, such as pressure-buildup tests, has been used for determining the reservoir description. However, these techniques often prove costly both in terms of additional equipment requirements and delays in well on-line dates. In addition, conventional well testing may not be successful in low-permeability reservoirs because these wells may not flow at measurable rates before stimulation. These cost and reservoir limitations have forced the engineer to seek other low-cost methods for determining reservoir properties. One such option for acquiring these data is the use of a mini-frac injection test conducted before a stimulation treatment. The mini-frac analysis techniques available to provide estimates of the formation capacity (kh) and indications of the presence of natural fractures include preclosure and post-closure methods.
|File Size||996 KB||Number of Pages||12|
Abousleiman, Y., Cheng, A.H.-D., and Gu, H.: "Formation PermeabilityDetermination by Micro or Mini-Hydraulic Fracturing," J. Ener. Res.Tech. (June 1994) 116, No. 2, 104.
Agarwal, R.G., Carter, R.D., and Pollock, C.B.: "Evaluation and Performance Predictionof Low-Permeability Gas Wells Stimulated by Massive Hydraulic Fracturing,"JPT (March 1979) 31, No. 7, 362; Trans., AIME, 267.
Aguilera, R.: "Well TestAnalysis of Naturally Fractured Reservoirs," SPEFE (September 1987)2, No. 3, 239.
Aguilera, R. and Ng, M.C.: "Decline-Curve Analysis ofHydraulically Fractured Wells in Dual-Porosity Reservoirs," paper SPE 22938presented at the 1991 SPE Annual Technical Conference and Exhibition, Dallas,6-9 October.
Ayoub, J.A., Bourdet, F.P., and Chauvel, Y.L.: "Impulse Testing," SPEFE(September 1988) 3, No. 3, 534; Trans., AIME, 285.
Barree, R.D.: "Applications ofPre-Frac Injection/Falloff Tests in Fissured Reservoirs—Field Examples,"paper SPE 39932 presented at the 1998 SPE Rocky MountainRegional/Low-Permeability Reservoirs Symposium, Denver, 5-8 April.
Barree, R.D. and Mukherjee, H.: "Determination of Pressure DependentLeakoff and its Effect on Fracture Geometry ," paper SPE 36424 presented atthe 1996 SPE Annual Technical Conference and Exhibition, Denver, 6-9October.
Benelkaldi, S.: "Reservoir Permeability Determination Using After-ClosureRadial Flow Analysis of Calibration Tests," MS thesis, U. of Oklahoma, Norman,Oklahoma (2001).
Bourdet, D., Ayoub, J., Whittle, T.M., Pirard, Y-M., and Kniazeff, V.:"Interpreting Well Tests in Fractured Reservoirs," World Oil (October1983) 72.
Carter, R.D.: Appendix of"Optimum Fluid Characteristics for FractureExtension," API Drilling and Prod. Prac. (1957).
Chipperfield, S.T. and Britt, L.K.: "Application of After-Closure Analysisfor Improved Fracture Treatment Optimisation: A Cooper Basin Case Study,"paper SPE 60316 presented at the 2000 SPE Rocky MountainRegional/Low-Permeability Reservoirs Symposium and Exhibition, Denver, 12-15March.
Cippolla, C., Branagan, P.T., and Lee, S.J.: "Fracture Design Considerations inNaturally Fractured Reservoirs," paper SPE 17607 presented at the 1988 SPEInternational Meeting on Petroleum Engineering, Tianjin, China, 1-4November.
Craig, D.P., Eberhard, M.J., and Barree, R.D.: "Adapting High Permeability LeakoffAnalysis to Low Permeability Sands for Estimating Reservoir EngineeringParameters," paper SPE 60291 presented at the 2000 SPE Rocky MountainRegional/Low-Permeability Reservoirs Symposium and Exhibition, Denver, 12-15March.
Dake, L.P.: Fundamentals of Reservoir Engineering, Elsevier Science,Amsterdam (1991).
Gringarten, A.C., Ramey, H.J. Jr., and Raghavan, R.: "Unsteady-State Pressure DistributionsCreated by a Well With a Single Infinite-Conductivity Vertical Fracture,"SPEJ (August 1974) 14, No. 4, 347; Trans., AIME,257.
Gu, H., Elbel, J.L, Nolte K.G, Cheng A.H.-D., and Abousleiman, Y.: "Formation Permeability DeterminationUsing Impulse-Fracture Injection," paper SPE 25425 presented at the 1993SPE Production Operations Symposium, Oklahoma City, Oklahoma, 21-23 March.
Gulrajani, S.N. and Nolte, K.G.: "Appendix: Background for HydraulicFracturing Pressure Analysis Techniques," Reservoir Stimulation, JohnWiley and Sons, New York City (2000).
Gulrajani, S.N., Vasudevan, S., and Ganguly, U.: "Enhanced Calibration TreatmentAnalysis for Optimizing Fracture Performance: Validation and FieldExamples," paper SPE 50611 presented at the 1998 SPE European PetroleumConference, The Hague, 20-22 October.
Houze, O.P., Horne, R.N., and Ramey, H.J. Jr.: "Pressure-Transient Response of anInfinite-Conductivity Vertical Fracture in a Reservoir With Double-PorosityBehavior," SPEFE (September 1988) 3, No. 3, 510;Trans., AIME, 285.
Ispas, I.N., Britt, L.K, Tiab, D., Valko, P., and Economides, M.J.: "Methodology of Fluid Leakoff Analysisin High-Permeability Fracturing," paper SPE 39476 presented at the SPEFormation Damage Control Conference, Lafayette, Louisiana, 18-19 February.
Mayerhofer, M.J., Ehlig-Economides, C.A., and Economides, M.J.: "Pressure-Transient Analysis ofFracture Calibration Treatments," JPT (March 1995) 47, No. 3,229; Trans., AIME, 299.
Najurieta, H.L.: "A Theory forPressure Transient Analysis in Naturally Fractured Reservoirs ," JPT(July 1980) 32, No. 7, 1241.
Nolte, K.G: "Background forAfter-Closure Analysis of Fracture Calibration Tests," paper SPE 39407available from SPE, Richardson, Texas (1997).
Nolte, K.G., Maniere, J.L., and Owens, K.A.: "After-Closure Analysis of FractureCalibration Tests," paper SPE 38676 presented at the 1997 SPE AnnualTechnical Conference and Exhibition, San Antonio, Texas, 5-8 October.
Nordgren, R.P.: "Propagation ofa Vertical Hydraulic Fracture," SPEJ (August 1972) 12, No. 4,306; Trans., AIME, 253.
Ramurthy, M., Marjerisson, D.M., and Daves, S.B.: "Diagnostic Fracture Injection Test inCoals to Determine Pore Pressure and Permeability," paper SPE 75701presented at the 2002 SPE Gas Technology Symposium, Calgary, 30 April-2May.
Reservoir Stimulation, K.G. Nolte and M. Economides (eds.), JohnWiley and Sons, New York City (2000) Chap. 9.
Stewart, G. and Asharsobbi, F.: "Well Test Interpretation forNaturally Fractured Reservoirs," paper SPE 18173 presented at the 1988 SPEAnnual Technical Conference and Exhibition, Houston, 2-5 October.
Talley, G.R., Swindell, T.M., Waters, G.A., and Nolte, K.G.: "Field Application of After-ClosureAnalysis of Fracture Calibration Tests ," paper SPE 52220 presented at the1999 SPE Mid-Continent Operations Symposium, Oklahoma City, Oklahoma, 28-31March.
Warren, J.E. and Root, P.J.: "TheBehaviour of Naturally Fractured Reservoirs," SPEJ (September 1963)3, No. 3, 245; Trans., AIME, 228.