Compositional Simulation of Hydraulically Fractured Tight Formation Considering the Effect of Capillary Pressure on Phase Behavior
- Nithiwat Siripatrachai (Pennsylvania State University) | Turgay Ertekin (Pennsylvania State University) | Russell T. Johns (Pennsylvania State University)
- Document ID
- Society of Petroleum Engineers
- SPE Journal
- Publication Date
- August 2017
- Document Type
- Journal Paper
- 1,046 - 1,063
- 2017.Society of Petroleum Engineers
- Phase Behavior, Unconventional Reservoir, Reservoir Simulation, Fractured Reservoir, Capillary Pressure
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- 571 since 2007
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Compositional reservoir simulation plays a vital role in the development of conventional and unconventional reservoirs. Two major building blocks of compositional simulation are phase-behavior and fluid-transport computations. The oil and gas reserves and flow of reservoir fluids are strongly dependent on phase behavior. In conventional reservoirs, capillary pressure is relatively small and is typically ignored in phase-behavior calculations. The approach is accepted as the norm to perform phase-equilibria calculation to estimate the oil and gas in place and fluid properties. However, large capillary pressure values are encountered in tight formations, such as shales, and therefore, its effects should not be ignored in phase-equilibria calculations. Many parameters and uncertainties contribute to the accuracy of the estimation and simulation results. In this research, the focus is on the effect of capillary pressure, and neglecting the effects of capillary pressure on phase behavior can lead to an inaccurate estimation of original oil in place (OOIP) and original gas in place (OGIP) as well as recovery performance because of the inherent assumption of equal phase pressures in the phase-equilibria calculation. Understanding of the effect of capillary pressure on phase behavior in tight reservoirs is by no means complete, especially by use of compositional simulation for hydraulically fractured reservoirs.
In this paper, we develop a new compositional reservoir simulator capable of modeling discrete fractures and incorporating the effect of capillary pressure on phase behavior. Large-scale natural and hydraulic fractures in tight rocks and shales are modeled with a technique called the embedded-discrete-fracture model (EDFM), where fractures are modeled explicitly without use of local-grid refinement (LGR) or an unstructured grid. Flow of hydrocarbons occurs simultaneously within similar and different porosity types. Capillary pressure is considered in both flow and flash calculations, where simulations also include variable pore size as a function of gas saturation to accurately reflect temporal changes in each gridblock during the simulation. We examine the effect of capillary pressure on the OOIP and cumulative oil production for different initial reservoir pressures (above and below the bubblepoint pressure) on Bakken and Eagle Ford fluids. The importance of capillary pressure on both flow and flash calculations from hydraulically fractured horizontal wells during primary depletion in fractured tight reservoirs by use of two fluid compositions is demonstrated.
Phase-behavior calculations show that bubblepoint pressure is suppressed, allowing the production to remain in the single-phase region for a longer period of time and also altering phase compositions and fluid properties, such as density and viscosity of equilibrium liquid and vapor. The results show that bubblepoint suppression is larger in the Eagle Ford shale than for Bakken. On the basis of the reservoir fluid and model used for the Bakken and Eagle Ford formations, when capillary pressure is included in the flash, we found an increase in OOIP up to 4.1% for the Bakken crude corresponding to an initial reservoir pressure of 2,000 psia and 46.33% for the Eagle Ford crude corresponding to an initial pressure of 900 psia. Depending on the initial reservoir pressure, cumulative primary oil production after 1 year increases because of the capillary pressure by approximately 9.0 to 38.2% for an initial reservoir-pressure range from 2,000 to 3,500 psia for Bakken oil and 7.2 to 154% for an initial reservoir-pressure range from 1,500 to 3,500 psia for Eagle Ford oil. The recovery increase caused by capillary pressure becomes more significant when reservoir pressure is far less than bubblepoint pressure. The simulation results with hydraulically fractured wells give similar recovery differences. For the two different reservoir settings in this study, at initial reservoir pressure of 5,500 psia, cumulative oil production after 1 year is 3.5 to 5.2% greater when capillary pressure is considered in phase-behavior calculations for Bakken. As initial reservoir pressure is lowered to 2,500 psia, the increase caused by capillary pressure is up to 28.1% for Bakken oil for the case studied. Similarly, at initial reservoir pressure of 2,000 psia, the increase caused by capillary pressure is 21.8% for Eagle Ford oil.
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Agboada, D. K. and Ahmadi, M. 2013. Production Decline and Numerical Simulation Model Analysis of the Eagle Ford Shale Play. Presented at the SPE Western Regional & AAPG Pacific Section Meeting 2013 Joint Technical Conference, Monterey, California, 19–25 April. SPE-165315-MS. https://doi.org/10.2118/165315-MS.
Ayirala, S. C. and Rao, D. N. 2006. A New Mechanistic Parachor Model to Predict Dynamic Interfacial Tension and Miscibility in Multicomponent Hydrocarbon Systems. J. Colloid Interf. Sci. 299 (1): 321–331. https://doi.org/10.1016/j.jcis.2006.01.068.
Brusilovsky, A. I. 1992. Mathematical Simulation of Phase Behavior of Natural Multicomponent Systems at High Pressures With an Equation of State. SPE Res Eng 7 (1): 117–122. SPE-20180-PA. https://doi.org/10.2118/20180-PA.
Clark, A. J. 2009. Determination of Recovery Factor in the Bakken Formation, Mountrail County, ND. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 4–7 October. SPE-133719-STU. https://doi.org/10.2118/133719-STU.
Computer Modelling Group (CMG). 2014. User’s Guide, GEM: Advanced Compositional Reservoir Simulator, Version 2014. Calgary: CMG.
Coats, K. H. 1980. An Equation of State Compositional Model. SPE J. 20 (5): 363–376. SPE-8284-PA. https://doi.org/10.2118/8284-PA.
Fanchi, J. R. 1985. Calculation of Parachors for Compositional Simulation. J Pet Technol 37 (11): 2049–2050. SPE-13402-PA. https://doi.org/10.2118/13402-PA.
Fanchi, J. R. 1990. Calculation of Parachors for Compositional Simulation: An Update. SPE Res Eval & Eng 5 (3): 433–436. SPE-19453-PA. https://doi.org/10.2118/19453-PA.
Hart, N. 2011. How Long Will Eagle Ford Shale Wells Produce? Eagle Ford Shale Blog, http://eaglefordshaleblog.com/2011/09/30/how-longwill-eagleford-shale-wells-produce (accessed 19 January 2016).
Javadpour, F. 2009. Nanopores and Apparent Permeability of Gas Flow in Mudrocks (Shales and Siltstone). J Can Pet Technol 48 (8): 16–21. PETSOC-09-08-16-DA. https://doi.org/10.2118/09-08-16-DA.
Javadpour, F., Fisher, D., and Unsworth, M. 2007. Nanoscale Gas Flow in Shale Gas Sediments. J Can Pet Technol 46 (10): 55–61. PETSOC-07-10-06. https://doi.org/10.2118/07-10-06.
Jin, L., Ma, Y., and Jamili, A. 2013. Investigating the Effect of Pore Proximity on Phase Behavior and Fluid Properties in Shale Formations. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 30 September–2 October. SPE-166192-MS. https://doi.org/10.2118/166192-MS.
Ju, L. and Burkardt, J. 2011. MGMRES: Restarted GMRES Solver for Sparse Linear Systems, http://people.sc.fsu.edu/~jburkardt/cpp_src/mgmres/mgmres.html (accessed 20 November 2014).
Katsube, T. J. 2000. Shale Permeability and Pore-Structure Evolution Characteristics. Geol. Surv. Can. 2000-E15: 9 pages. https://doi.org/10.4095/211622.
Kuila, U. and Prasad, M. 2013. Specific Surface Area and Pore-Size Distribution in Clays and Shales. Geophys. Prospect. 61 (2): 341–362. https://doi.org/10.1111/1365-2478.12028.
Lee, S. H., Lough, M. F., and Jensen, C. L. 2001. Hierarchical Modeling of Flow in Naturally Fractured Formations with Multiple Length Scales. Water Resour. Res. 37 (3): 443–455. https://doi.org/10.1029/2000WR900340.
LeFever, J. and Helms, L. 2006. Bakken Formation Reserve Estimates. Report, Department of Mineral Resources, North Dakota.
Li, L. and Lee, S. H. 2008. Efficient Field-Scale Simulation of Black Oil in a Naturally Fractured Reservoir Through Discrete Fracture Networks and Homogenized Media. SPE Res Eval & Eng 11 (4): 750–758. SPE-103901-PA. https://doi.org/10.2118/103901-PA.
Lough, M. F., Lee, S. H., and Kamath, J. 1998. An Efficient Boundary Integral Formulation for Flow Through Fractured Porous Media. J. Comput. Phys. 143 (2): 462–483. https://doi.org/10.1006/jcph.1998.5858.
Macleod, D. B. 1923. On a Relation Between Surface Tension and Density. Trans. Faraday Soc. 19 (July): 38–41. https://doi.org/10.1039/TF9231900038.
Moinfar, A., Varavei, A., Sepehrnoori, K. et al. 2012. Development of a Novel and Computationally-Efficient Discrete-Fracture Model to Study IOR Processes in Naturally Fractured Reservoirs. Presented at the SPE Improved Oil Recovery Symposium, Tulsa, 14–18 April. SPE-154246-MS. https://doi.org/10.2118/154246-MS.
Nojabaei, B. 2015. Phase Behavior and Flow Analysis of Shale Reservoirs Using a Compositionally-Extended Black-Oil Approach. PhD dissertation, Pennsylvania State University, University Park, Pennsylvania (July 2015).
Nojabaei, B., Johns, R. T., and Chu, L. 2013. Effect of Capillary Pressure on Phase Behavior in Tight Rocks and Shales. SPE Res Eval & Eng 16 (3): 281–289. SPE-159258-PA. https://doi.org/10.2118/159258-PA.
Nojabaei, B., Siripatrachai, N., Johns, R. T. et al. 2014. Effect of Saturation Dependent Capillary Pressure on Production in Tight Rocks and Shales: A Compositionally-Extended Black Oil Formulation. Presented at the SPE Eastern Regional Meeting, Charleston, West Virginia, 21–23 October. SPE-171028-MS. https://doi.org/10.2118/171028-MS.
Nojabaei, B., Siripatrachai, N., Johns, R. T. et al. 2016. Effect of Large Gas-Oil Capillary Pressure on Production: A Compositionally-Extended Black Oil Formulation. J. Pet. Sci. Eng. 147 (November): 317–329. https://doi.org/10.1016/j.petrol.2016.05.048.
Orangi, A., Nagarajan, N. R., Honarpour, M. M. et al. 2011. Unconventional Shale Oil and Gas-Condensate Reservoir Production, Impact of Rock, Fluid, and Hydraulic Fractures. Presented at the SPE Hydraulic Fracturing Technology Conference, The Woodlands, Texas, 24–26 January. SPE-140536-MS. https://doi.org/10.2118/140536-MS.
Peaceman, D. W. 1983. Interpretation of Well-Block Pressures in Numerical Reservoir Simulation With Nonsquare Grid Blocks and Anisotropic Permeability. SPE J. 23 (3): 531–543. SPE-10528-PA. https://doi.org/10.2118/10528-PA.
Pedersen, K. S., Christensen, P. L., and Shaikh, J. A. 2014. Phase Behavior of Petroleum Reservoir Fluids. Boca Raton, Florida: CRC Press.
Peng, D. Y. and Robinson, D. B. 1976. A New Two-Constant Equation of State. Ind. Eng. Chem. Fundamen. 15 (1): 59–64. https://doi.org/10.1021/i160057a011.
Ramirez, J. and Aguilera, R. 2014. Factors Controlling Fluid Migration and Distribution in the Eagle Ford Shale. Presented at the SPE/CSUR Unconventional Resources Conference–Canada, Calgary, 30 September–2 October. SPE-171626-MS. https://doi.org/10.2118/171626-MS.
Rezaveisi, M., Sepehrnoori, K., Pope, G. A. et al. 2015. Compositional Simulation Including Effect of Capillary Pressure on Phase Behavior. Presented at the SPE Annual Technical Conference and Exhibition, Houston, 28–30 September. SPE-175135-MS. https://doi.org/10.2118/175135-MS.
Shapiro, A. A. and Stenby, E. H. 2001. Thermodynamics of the Multicomponent Vapor–Liquid Equilibrium Under Capillary Pressure Difference. Fluid Phase Equilibr. 178 (1–2): 17–32. https://doi.org/10.1016/S0378-3812(00)00403-9.
Sigmund, P. M., Dranchuk, P. M., Morrow, N. R. et al. 1973. Retrograde Condensation in Porous Media. SPE J. 13 (2): 93–104. SPE-3476-PA. https://doi.org/10.2118/3476-PA.
Sugden, S. 1924. VI.—The Variation of Surface Tension with Temperature and Some Related Functions. J. Chem. Soc. Trans. 125: 32–41. https://doi.org/10.1039/CT9242500032.
Walls, J. D. and Sinclair, S. W. 2011. Eagle Ford Shale Reservoir Properties from Digital Rock Physics. First Break 29 (6): 97–101.
Wang, Y., Yan, B., and Killough, J. 2013. Compositional Modeling of Tight Oil Using Dynamic Nanopore Properties. Presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 30 September–2 October. SPE-166267-MS. https://doi.org/10.2118/166267-MS.