Stochastic 2D Well-Path Assessments for Naturally Fractured Carbonate Reservoirs
- Dean Wehunt (Chevron Europe, Eurasia, and Middle East Exploration and Production Company) | Marina Borovykh (Chevron Europe, Eurasia, and Middle East Exploration and Production Company) | Wayne Narr (Chevron Energy Technology Company)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- November 2017
- Document Type
- Journal Paper
- 853 - 875
- 2017.Society of Petroleum Engineers
- Stochastic 2D Model, Fracture Stratigraphy, Decision Analysis, Water Mitigation, Fracture Characterization
- 1 in the last 30 days
- 205 since 2007
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Simple but geologically reasonable and calibrated 2D stochastic models are useful to quantify significant risks and uncertainties associated with alternative-development-well trajectories, particularly when statistical relationships can be established to help quantify those risks and uncertainties, and when the geologic features that create the risks and uncertainties are not adequately addressed within reservoir flow models.
Our example stochastic 2D model considered the naturally fractured depositional-slope region of an isolated carbonate buildup, and the model was populated with relevant features including distributions and geometric details of natural fractures, natural-fracture clustering, and intraformational slope clinoforms that define a mechanically layered sequence. The model was calibrated by use of well-production results and production-logging data so that it reproduced observed well results for cases where the lower sequence boundary does not occur above the oil/water contact (OWC), adding confidence that the model could be used to represent the statistical impact of various alternative trajectories for future wells.
Experimental design (ED) was used to determine the significant uncertainties and well-path decisions. Heel and toe elevation and the number of clinoforms encountered by the well were the only significant variables for modeling the frequency of water production. For modeling the frequency of direct well communication to the gas cap, the same variables were significant, in addition to well direction, completion length, and fracture density. The amount of fracture clustering applied in the model was also significant. For our example case, changing the well-elevation profile was effective in managing gas or water risks; however, tradeoffs were evident—and quantified—in attempting to simultaneously address both risks. Minimizing drawdown was not an effective strategy because productivity was low and rarely resulted in economic water-free production if any open fracture connected the well with the aquifer.
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Adeleke, J., Saada, T., Pitoni, E. et al. 2014. A New Era of Effective Reservoir Management: Completion and Stimulation Technology Evolution in the Karachaganak Field. Presented at the SPE Annual Caspian Technical Conference and Exhibition, Astana, Kazakhstan, 12–14 November. SPE-172338-MS. https://doi.org/10.2118/172338-MS.
Albertini, C., Bigoni, A., Cominelli, E. et al. 2014. Karachaganak, Integrated Reservoir Studies on a Giant Field. Presented at the SPE Annual Caspian Technical Conference and Exhibition, Astana, Kazakhstan, 12–14 November. SPE-172274-MS. https://doi.org/10.2118/172274-MS.
AlHanai, W., AlMahdi, A. M., and Deeb, M. A. 1995. Use of Stochastic Characterization to Select Horizontal Well Trajectories in a Heterogeneous Carbonate Reservoir. Presented at the Middle East Oil Show, Bahrain, 11–14 March. SPE-29811-MS. https://doi.org/10.2118/29811-MS.
Anders, M. H., Laubach, S. E., and Scholz, C. H. 2014. Microfractures: A Review. J. Struct. Geol. 69B (December): 377–394. https://doi.org/10.1016/j.jsg.2014.05.011.
B.G. Group. 2010. Karachaganak Pre-Tula Reservoir Characterization and Conceptual Geologic Model Report, Part 1, 25. Bogdonov, A. A. 1947. The Intensity of Cleavage as Related to the Thickness of the Bed. Soviet Geol. 16: 102–104.
Borromeo, O., Luoni, F., Bigoni, F. et al. 2010. Stratigraphic Architecture of the Early Carboniferous Reservoir in Karachaganak Field, Pri-Caspian Basin (Kazakhstan). Presented at the SPE Caspian Carbonates Technology Conference, Atyrau, Kazakhstan, 8–10 November. SPE-139887-MS. https://doi.org/10.2118/139887-MS.
Catuneanu O., Abreu, V., Bhattacharya, J. P. et al. 2009. Towards the Standardization of Sequence Stratigraphy. Earth-Sci. Rev. 92 (1–2): 1–33. https://doi.org/10.1016/j.earscirev.2008.10.003.
Collins, J., Narr, W., Harris, P. M. et al. 2013. Lithofacies, Depositional Environments, Burial Diagenesis, and Dynamic Field Behavior in a Carboniferous Slope Reservoir, Tengiz Field (Republic of Kazakhstan), and Comparison with Outcrop Analogs. In Deposits, Architecture, and Controls on Carbonate Margin, Slope and Basinal Settings, ed. K. Verwer, T. E. Playton, and P. M. Harris, Vol. 105, 50–83. Tulsa: Society for Sedimentary Geology, Special Publications.
Flodin, E. A. 2009. Well Log and Production Based Analysis of Fractures in Karachaganak Field, Northwestern Kazakhstan. Chevron Energy Technology Company Internal Report No. TR20090033, San Ramon, California.
Frost, E. L. and Kerans, C. 2009. Restricted access Platform-Margin Trajectory as a Control on Syndepositional Fracture Patterns, Canning Basin, Western Australia. J. Sediment. Res. 79 (2): 44–55. https://doi.org/10.2110/jsr.2009.014.
Gale, J. F. W. 2002. Specifying Lengths of Horizontal Wells in Fractured Reservoirs. SPE Res Eval & Eng 5 (3): 266–272. SPE-78600-PA. https://doi.org/10.2118/78600-PA.
Gale, J. F. W., Laubach, S. E., Olson, J. E. et al. 2014. Natural Fractures in Shale: A Review and New Observations. AAPG Bull. 98 (11): 2165–2216. https://doi.org/10.1306/08121413151.
Goovaerts, P. 1997. Geostatistics for Natural Resources Evaluation. New York City: Oxford University Press.
Gross, M. R., Fischer, M. P., Engelder, T. et al. 1995. Factors Controlling Joint Spacing in Interbedded Sedimentary Rocks: Integrating Numerical Models with Field Observations from the Monterey Formation, USA. Geol. Soc. London Spec. Pub. 92 (1): 215–233. https://doi.org/10.1144/GSL.SP.1995.092.01.12.
Guo, G. and Evans, R. D. 1994. Geologic and Stochastic Characterization of Naturally Fractured Reservoirs. Presented at the SPE Latin America/Caribbean Petroleum Engineering Conference, Buenos Aires, 27–29 April. SPE-27025-MS. https://doi.org/10.2118/27025-MS.
Hooker, J. N., Laubach, S. E., and Marrett, R. 2013. Fracture-Aperture Size—Frequency, Spatial Distribution, and Growth Processes in Strata-Bounded and Non-Strata-Bounded Fractures, Cambrian Meso´n Group, NW Argentina. J. Struct. Geol. 54 (September): 54–71. https://doi.org/10.1016/j.jsg.2013.06.011.
Jenni, S., Hu, L. Y., and Basquet, R. 2004. History Matching of Stochastic Models of Field-Scale Fractures: Methodology and Case Study. Presented at the SPE Annual Technical Conference and Exhibition, Houston, 26–29 September. SPE-90020-MS. https://doi.org/10.2118/90020-MS.
Jensen, J. L., Lake, L. W., Corbett, P. W. M. et al. 2000. Statistics for Petroleum Engineers and Geoscientists, second edition. Amsterdam: Elsevier Science.
Katz, D., Playton, T., Bellian, J. et al. 2010. Slope Heterogeneity in a Steep-Sided Upper Paleozoic Isolated Carbonate Platform Reservoir, Karachaganak Field, Kazakhstan. Presented at the SPE Caspian Carbonates Technology Conference, Atyrau, Kazakhstan, 8–10 November. SPE-139960-MS. https://doi.org/10.2118/139960-MS.
Ladeira, F. L. and Price, N. J. 1981. Relationship Between Fracture Spacing and Bed Thickness. J. Struct. Geol. 3 (2): 179–183. https://doi.org/10.1016/0191-8141(81)90013-4.
Laubach, S. E., Olson, J. E., and Gross, M. R. 2009. Mechanical and Fracture Stratigraphy. AAPG Bull. 93 (11): 1413–1426. https://doi.org/10.1306/07270909094.
Liu, X. and Srinivasan, S. 2004. Merging Outcrop Data and Geomechanical Information in Stochastic Models of Fractured Reservoirs. Presented at the SPE Annual Technical Conference and Exhibition, Houston, 26–29 September. SPE-90643-MS. https://doi.org/10.2118/90643-MS.
McQuillan, H. 1973. Small-Scale Fracture Density in Asmari Formation of Southwest Iran and its Relation to Bed Thickness and Structural Setting. AAPG Bull. 57 (12): 2367–2385.
Narr, W. 1991. Fracture Density in the Deep Subsurface: Techniques with Application to Point Arguello Oil Field. AAPG Bull. 75 (8):1300–1323.
Narr, W. 1996. Estimating Average Fracture Spacing in Subsurface Rock. AAPG Bull. 80 (10): 1565–1586.
Narr, W. and Lerche, I. 1984. A Method for Estimating Subsurface Fracture Density in Core. AAPG Bull. 68 (5): 637–648.
Narr, W. and Suppe, J. 1991. Joint Spacing in Sedimentary Rocks. J. Struct. Geol. 13 (9): 1037–1048. https://doi.org/10.1016/0191-8141(91)90055-N.
Nelson, R. A. 2001. Geological Analysis of Naturally Fractured Reservoirs, second edition. Houston: Gulf Publishing Company.
Olson, J. E. 2004. Predicting Fracture Swarms—The Influence of Subcritical Crack Growth and the Crack-Tip Process Zone on Joint Spacing in Rock. Geol. Soc. London Spec. Pub. 231 (1): 73–88. https://doi.org/10.1144/GSL.SP.2004.231.01.05.
Plackett, R. L. and Burman, J. P. 1946. The Design of Optimum Multifactorial Experiments. Biometrika 33 (4), pp. 305–25, June. https://doi.org/10.1093/biomet/33.4.305.
Rich, J. L. 1951. Three Critical Environments of Deposition, and Criteria for Recognition of Rocks Deposited in Each of Them. Geol. Soc. Am. Bull. 62 (1): 1–20. https://doi.org/10.1130/0016-7606(1951)62[1:TCEODA]2.0.CO;2.
Saduassakov, B., Yakhiyayev, N., Uxukbayev, G. et al. 2014. Integrated Carbonate Clinoform Characterization through Assisted History Matching of Wireline Formation Pressure Data, Karachaganak Field, Kazakhstan. Presented at the SPE Annual Caspian Technical Conference and Exhibition, Astana, Kazakhstan, 12–14 November. SPE-172327-MS. https://doi.org/10.2118/172327-MS.
Tavakkoli, M., Mohammadsadeghi, M., Shahrabadi, A. et al. 2009. Deterministic versus Stochastic Discrete Fracture Network (DFN) Modeling, Application in a Heterogeneous Naturally Fractured Reservoir. Presented at the Kuwait International Petroleum Conference and Exhibition, Kuwait City, Kuwait, 14–16 December. SPE-127086-MS. https://doi.org/10.2118/127086-MS.
Terzaghi, R. D. 1965. Sources of Errors in Joint Surveys. Geotechnique 15 (3): 287–304. https://doi.org/10.1680/geot.19188.8.131.527.
Vasco, D. W. and Datta-Gupta, A. 1997. Integrating Field Production History in Stochastic Reservoir Characterization. SPE Form Eval 12 (3): 149–156. SPE-36567-PA. https://doi.org/10.2118/36567-PA.