Rate Dependence of Bilinear Flow in Unconventional Gas Reservoirs
- Mohammed S. Kanfar (University of Calgary) | Christopher R. Clarkson (University of Calgary)
- Document ID
- Society of Petroleum Engineers
- SPE Reservoir Evaluation & Engineering
- Publication Date
- February 2018
- Document Type
- Journal Paper
- 17 - 30
- 2018.Society of Petroleum Engineers
- Rate Transient Analysis, Correction Factor, Unconventional Gas, Bilinear Flow
- 4 in the last 30 days
- 464 since 2007
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Unconventional fractured gas wells occasionally exhibit bilinear flow during early production. When this flow regime is observed, important fracture properties can be estimated such as conductivity and/or spacing. However, the application of present-day rate-transientanalysis (RTA) methods to bilinear flow results in up to 18% error. This error is rate-dependent, and occurs because of nonlinearities in the gas-diffusivity equation. This paper presents a new correction factor that handles the rate dependency of bilinear flow, and enables more-accurate reservoir characterization.
The diffusivity equation of gas in porous media has some nonlinearities that cannot be addressed by only using the real-gas pseudopressure. Even though neglecting these nonlinearities results in a model that is sufficiently accurate for the radial-flow case, errors arise in the boundary-dominated-flow (BDF) (Fraim and Wattenbarger 1987), the linear-flow (Ibrahim and Wattenbarger 2006; Nobakht and Clarkson 2012), and, as shown in this article, the bilinear-flow cases. Currently, no research studies provide an accurate bilinear-flow analytical model for gas reservoirs. To bridge this gap and to provide rate-transient analysts with a practical tool, this work presents a correction factor that can be incorporated into the existing bilinear-flow models. The correction factor was developed following an approach similar to that of Ibrahim and Wattenbarger (2006). The first step was to simulate a number of reservoir and well conditions. Second, fracture properties were back calculated with the current bilinear-flow models. Finally, errors between the back calculated and the simulated properties were correlated to dimensionless drawdown. After these steps, a correction factor was obtained that applied to various bilinear-flow cases.
The obtained numerical results indicate that errors in bilinear-flow models are correlated with rate, or more precisely, dimensionless drawdown [a similar behavior is observed in the analytical model of linear flow, as demonstrated by Ibrahim and Wattenbarger (2006)]. This correlation can be used to reduce error to less than ±3%. Because the simulated cases cover an extensive range of unconventional reservoir conditions, the empirical correction is robust and applicable to a wide variety of reservoir conditions. Most importantly, the correction is practical and can be readily incorporated into existing bilinear-flow models. The application of the new correction is demonstrated in this article with synthetic and field examples.
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Aguilera, R. and Ng, M. 1991. Transient-Pressure Analysis of Horizontal Wells in Anisotropic Naturally Fractured Reservoirs. SPE Form Eval 6 (1): 95–100. SPE-19002-PA. https://doi.org/10.2118/19002-PA.
Al-Ahmadi, H. and Wattenbarger, R. 2011. Triple-Porosity Models: One Further Step Towards Capturing Fractured Reservoirs Heterogeneity. Presented at the SPE/DGS Saudi Arabia Section Technical Symposium and Exhibition, Al-Khobar, Saudi Arabia, 15–18 May. SPE-149054-MS. https://doi.org/10.2118/149054-MS.
Al-Hussainy, R., Ramey Jr., H. J., 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.
Bello, R. and Wattenbarger, R. 2010. Modelling and Analysis of Shale Gas Production With a Skin Effect. J Can Pet Technol 49 (12): 37–48. SPE-143229-PA. https://doi.org/10.2118/143229-PA.
Carlson, E. and Mercer, J. 1991. Devonian Shale Gas Production: Mechanisms and Simple Models. J Pet Technol 43 (4): 476–482. SPE-19311-PA. https://doi.org/10.2118/19311-PA.
Cinco-Ley, H. and Samaniego-V., F. 1981. Transient Pressure Analysis for Fractured Wells. J Pet Technol 33 (9): 1749–1766. SPE-7490-PA. https://doi.org/10.2118/7490-PA.
El-Banbi, A. 1998. Analysis of Tight Gas Wells. PhD dissertation, Texas A &M University, College Station, Texas.
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.
Gatens, M., Lee, W., Lane, H. et al. 1989. Analysis of Eastern Devonian Gas Shales Production Data. J Pet Technol 41 (5): 519–525. SPE-17059-PA. https://doi.org/10.2118/17059-PA.
Ibrahim, M. and Wattenbarger, R. A. 2006. Rate Dependence of Transient Linear Flow in Tight Gas Wells. J Can Pet Technol 45 (10). SPE-06-10-TN2. https://doi.org/10.2118/06-10-TN2.
Kanfar, M., Alkouh, A., and Wattenbarger, R. 2014. Bilinear Flow in Shale Gas Wells: Fact or Fiction? Presented at the SPE/C SUR Unconventional Resources Conference–Canada, Calgary, 30 September–2 October. SPE-171669-MS. https://doi.org/10.2118/171669-MS.
Kucuk, F. and Sawyer, W. 1979. Modeling of Devonian Shale Gas Reservoir Performance. In Proc., Third Eastern Gas Shales Symposium, Morgantown, West Virginia, USA, 1–3 October.
Levine, D. M., Ramsey, P. P., and Smidt, R. K. 2001. Applied Statistics for Engineers and Scientists: Using Microsoft Excel and Minitab. New Jersey: Prentice Hall.
Nobakht, M. and Clarkson, C. R. 2012. A New Analytical Method for Analyzing Linear Flow in Tight/Shale Gas Reservoirs: Constant-Flowing-Pressure Boundary Condition. SPE Res Eval & Eng 15 (3): 370–384. SPE-143989-PA. https://doi.org/10.2118/143989-PA.
Ozkan, K., Ohaeri, U., and Raghavan, R. 1987. Unsteady Flow to a Well Produced at a Constant Pressure in a Fractured Reservoir. SPE Form Eval 2 (2): 186–200. SPE-9902-PA. https://doi.org/10.2118/9902-PA.
Ozkan, E. 1988. Performance of Horizontal Wells. PhD dissertation, University of Tulsa, Tulsa, Oklahoma (January 1988).
Serra, K., Reynolds, A., and Raghavan, R. 1983. New Pressure Transient Analysis Methods for Naturally Fractured Reservoirs. J Pet Technol 35 (12): 2271–2283. SPE-10780-PA. https://doi.org/10.2118/10780-PA.
Spivey, J. and Semmelbeck, M. 1995. Forecasting Long-Term Gas Production of Dewatered Coal Seams and Fractured Gas Shales. Presented at the SPE Symposium on Low Permeability Reservoirs, Denver, 19–22 March. SPE-29580-MS. https://doi.org/10.2118/29580-MS.
Tivayanonda, V. 2012. Comparison of Single, Double, and Triple Linear Flow Models for Shale Gas/Oil Reservoirs. MS thesis, Texas A&M University, College Station, Texas, USA (August 2012).
Tivayanonda, V., Apiwathanasorn, S., Economides, C. et al. 2012. Alternative Interpretations of Shale Gas/Oil Rate Behavior Using a Triple Porosity Model. Presented at the SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8–10 October. SPE-159703-MS. https://doi.org/10.2118/159703-MS.
Wattenbarger, R. A., El-Banbi, A. H., Villegas, M. E. et al. 1998. Production Analysis of Linear Flow into Fractured Tight Gas Wells. Presented at the SPE Rocky Mountain Regional/Low-Permeability Reservoirs Symposium, Denver, Colorado, 5–8 April. https://doi.org/10.2118/39931-MS.