Explicit Determination of Reserves for Variable-Bottomhole-Pressure Conditions in Gas Rate-Transient Analysis
- Yang Wang (State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum) | Luis F. Ayala (Pennsylvania State University)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- February 2020
- Document Type
- Journal Paper
- 369 - 390
- 2020.Society of Petroleum Engineers
- variable bottomhole pressure, boundary-dominated flow period, explicit estimation, gas well decline analysis
- 7 in the last 30 days
- 234 since 2007
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Current rate-transient-analysis tools for gas wells producing under boundary-dominated-flow (BDF) conditions largely rely on the deployment of the Arps empirical decline models (Arps 1945), or liquid-based analytical models rewritten in terms of pseudofunctions. Recently, Stumpf and Ayala (2016) demonstrated that, contrary to common practice, decline exponents (b) used in Arps’ hyperbolic equations when applied to gas-well analysis can be rigorously estimated before any field-production data are collected. This determination is solely dependent on gas pressure/volume/temperature (PVT) properties and prevailing constant-bottomhole-pressure (BHP) specification for volumetric, single-phase gas-flow conditions. In the study, we extend that work to a more-realistic variable-BHP condition, which is the most common production-specification condition, in terms of the ratio of changing BHP to average reservoir pressure. The decline exponent (b) is thus rederived, and it is shown that under such conditions, variable BHP hyperbolic decline coefficients become solely dependent on fluid PVT properties and take their largest possible magnitude compared with constant-BHP production. Step-by-step analysis procedures are presented that enable explicit and straightforward estimation of original gas in place (OGIP) and other reservoir properties by universal-type-curve and straight-line analysis. Finally, several cases using simulated and field data are discussed in detail to validate the capabilities of the proposed approach.
|File Size||2 MB||Number of Pages||22|
Abou-Kassem, J. H., Mattar, L., and Dranchuk, P. M. 1990. Computer Calculations of Compressibility of Natural Gas. J Can Pet Technol 29 (5): 105–108. PETSOC-90-05-10. https://doi.org/10.2118/90-05-10.
Agarwal, R. G. 1979. “Real Gas Pseudo-Time”—A New Function for Pressure Buildup Analysis of MHF Gas Wells. Presented at the SPE Annual Technical Conference and Exhibition, Las Vegas, Nevada, 23–26 September. SPE-8279-MS. https://doi.org/10.2118/8279-MS.
Al-Hussainy, R., Ramey, H. J. Jr., and Crawford, P. B. 1966. The Flow of Real Gases Through Porous Media. J Pet Technol 18 (5): 624–636. SPE-1243-A-PA. https://doi.org/10.2118/1243-A-PA.
Arps, J. J. 1945. Analysis of Decline Curves. Trans. AIME 160 (1): 228–247. SPE-945228-G. https://doi.org/10.2118/945228-G.
Ayala, L. F. and Morgan, E. C. 2016. Natural Gas Production Engineering. In ASTM Handbook MNL73: Exploration and Production of Petroleum and Natural Gas Processing, ed. M. R. Riazi and E. van Oort, Chap. 17. West Conshohocken, Pennsylvania: ASTM.
Ayala, L. and Ye, P. 2013a. Unified Decline Type-Curve Analysis for Natural Gas Wells in Boundary-Dominated Flow. SPE J. 18 (1): 97–113. SPE-161095-PA. https://doi.org/10.2118/161095-PA.
Ayala, L. F. and Ye, P. 2013b. Density-Based Decline Performance Analysis of Natural Gas Reservoirs Using a Universal Type-Curve. J. Energy Resour. Technol 135 (4): 042701. https://doi.org/10.1115/1.4023867.
Ayala, L. F. and Zhang, M. 2013. Rescaled Exponential and Density-Based Decline Models: Extension to Variable-Rate/Pressure-Drawdown Conditions. J Can Pet Technol 52 (6): 433–440. SPE-168223-PA. https://doi.org/10.2118/168223-PA.
Carter, R. D. 1985. Type Curves for Finite Radial and Linear Gas-Flow Systems: Constant-Terminal-Pressure Case. SPE J. 25 (5): 719–728. SPE-12917-PA. https://doi.org/10.2118/12917-PA.
Chu, W., Fleming, C. H., and Carrol, K. M. 2001. Determination of Original Gas in Place in Ballycotton, Offshore Ireland. SPE Res Eval & Eng 4 (1): 11–15. SPE-69735-PA. https://doi.org/10.2118/69735-PA.
Dranchuk, P. M. and Abou-Kassem, J. H. 1975. Calculation of Z Factors for Natural Gases Using Equations of State. J Can Pet Technol 14 (3). PETSOC-75-03-03. https://doi.org/10.2118/75-03-03.
Ertekin, T. and Ayala, L. F. 2018. Reservoir Engineering Models: Analytical and Numerical Approaches. New York City: McGraw Hill.
Fetkovich, M. J. 1980. Decline Curve Analysis Using Type Curves. J Pet Technol 32 (6): 1065–1077. SPE-4629-PA. https://doi.org/10.2118/4629-PA.
Fetkovich, M. J., Fetkovich, E. J., and Fetkovich, M. D. 1996. Useful Concepts for Decline Curve Forecasting, Reserve Estimation, and Analysis. SPE Res Eng 11 (1): 13–22. SPE-28628-PA. https://doi.org/10.2118/28628-PA.
Fraim, M. L. and Wattenbarger, R. A. 1987. Gas Reservoir Decline-Curve Analysis Using Type Curves With Real Gas Pseudopressure and Normalized Time. SPE Form Eval 2 (4): 671–682. SPE-14238-PA. https://doi.org/10.2118/14238-PA.
Ibrahim, M., Watterbarger, R. A., and Helmy, W. 2003. Determination of OGIP for Wells in Pseudosteady-State—Old Techniques, New Approaches. Presented at the SPE Annual Technical Conference and Exhibition, Denver, 5–8 October. SPE-84286-MS. https://doi.org/10.2118/84286-MS.
Lee, A. L., Gonzalez, M. H., and Eakin, B. E. 1966. The Viscosity of Natural Gases. J Pet Technol 18 (8): 997–1000. SPE-1340-PA. https://doi.org/10.2118/1340-PA.
Palacio, J. C. and Blasingame, T. A. 1993. Decline-Curve Analysis With Type Curves—Analysis of Gas Well Production Data. Presented at the Low Permeability Reservoirs Symposium, Denver, Colorado, 26–28 April. SPE-25909-MS. https://doi.org/10.2118/25909-MS.
Stumpf, T. N. and Ayala, L. F. 2016. Rigorous and Explicit Determination of Reserves and Hyperbolic Exponents in Gas-Well Decline Analysis. SPE J. 21 (5): 1843–1857. SPE-180909-PA. https://doi.org/10.2118/180909-PA.
Sutton, R. P. 1985. Compressibility Factors for High-Molecular-Weight Reservoir Gases. Presented at the SPE Annual Technical Conference and Exhibition, Las Vegas, Nevada, 22–26 September. SPE-14265-MS. https://doi.org/10.2118/14265-MS.
Ye, P. and Ayala, L. F. 2012. A Density-Diffusivity Approach for the Unsteady State Analysis of Natural Gas Reservoirs. J Nat Gas Sci Eng 7 (July): 22–34. https://doi.org/10.1016/j.jngse.2012.03.004.
Ye, P. and Ayala, L. F. 2013. Straight-Line Analysis of Flow Rate vs. Cumulative Production Data for the Explicit Determination of Gas Reserves. J Can Pet Technol 52 (4): 296–305. SPE-165583-PA. https://doi.org/10.2118/165583-PA.
Zhang, M. and Ayala, L. 2014a. Gas-Rate Forecasting in Boundary-Dominated Flow: Constant-Bottomhole-Pressure Decline Analysis by Use of Rescaled Exponential Models. SPE J. 19 (3): 410–417. SPE-168217-PA. https://doi.org/10.2118/168217-PA.
Zhang, M. and Ayala, L. F. 2014b. Gas-Production-Data Analysis of Variable-Pressure-Drawdown/Variable-Rate Systems: A Density-Based Approach. SPE Res Eval & Eng 17 (4) 520–529. SPE-172503-PA. https://doi.org/10.2118/172503-PA.