Numerical Study of Production Mechanism of Unconventional Liquid-Rich Shale Reservoirs with Multi-Fractured Horizontal Wells

Date

2016-08

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Abstract

Liquid-rich shale (LRS) volatile oil plays exhibit several challenges to modeling, and analyzing. Pore networks of shale plays consist primarily of inorganic materials, organic matter, and natural fractures. However, the flow mechanism through these multi-porosity systems is not well understood. In addition, liquid-rich shale (LRS) plays exhibit several other challenges to modeling, and analysis, including abnormally flattened produced gas-oil ratio (GOR), complex phase behavior, and heterogeneous rock properties, etc. In this paper, we report results of our investigations of multiphase flow in LRS plays including the impact of critical parameters related to fluids, rock, pore structure, rock-fluid, and stimulation processes on well performance of these resources, and a new methodology to model well performance.

We have conducted comprehensive reservoir numerical studies using a new procedure to divide porous media into different sub-media (porosity systems) with distinctive characteristics: multiple pore types in the shale matrix along with natural, and hydraulic fractures. New correlations for modifying PVT properties in nano-pores have been used to incorporate the impact of nano-pore confinement on phase behavior in organic nano-pores. In addition, the impact of the stimulation process on the formation, and creation of the stimulated reservoir volume (SRV), and the impact of rock compaction on transfer properties, and are incorporated into the simulation model. Different relative permeabilities for organic matter, and inorganic materials are employed in our model to account for high critical gas saturations.

We concluded that the connectivity between different pore systems, and relative permeability functions are the most important uncertainties that affect fluid flows. Our numerical model reproduced anomalous GOR’s that have been observed in liquid-rich shale oil wells. The study showed that nano-pore confinement delayed development of two-phase flow. It did not have a significant effect on producing GOR behavior of low thermal maturity reservoirs while in high maturity reservoirs it causes the” flat” GOR’s observed in early stages of production. Enhanced critical gas saturation delays mobilization of gas molecules in nano-pores, and could extend non-intuitive GOR behavior further when reservoir pressure drops below the bubble point. We found that permeability reduction due to compaction has a significant impact on the performance of LRS wells.

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Keywords

Liquid-Rich Shale, Unconventional shales, Numerical models, Production Mechanism, Reservoir simulation

Citation

Portions of this document appear in: Khoshghadam, M., A. Khanal, and W. J. Lee. "Numerical Study of Production Mechanisms and Gas-Oil Ratio Behavior of Liquid-Rich Shale Oil Reservoirs." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 2015. And in: Khoshghadam*, Mohammad, Aaditya Khanal, Neda Rabinejadganji, and W. John Lee. "How to Model and Improve Our Understanding of Liquid-Rich Shale Reservoirs with Complex Organic/Inorganic Pore Network." In Unconventional Resources Technology Conference, San Antonio, Texas, 1-3 August 2016, pp. 1739-1759. Society of Exploration Geophysicists, American Association of Petroleum Geologists, Society of Petroleum Engineers, 2016. DOI: 10.15530-urtec-2016-2459272. And in: Khoshghadam, M., A. Khanal, I. Makinde, W. J. Lee, and N. Rabinejadganji. "Numerical study of production mechanisms in unconventional liquid-rich shale volatile oil reservoirs." In SPE/CSUR Unconventional Resources Conference. Society of Petroleum Engineers, 2015. DOI: 10.2118/175994-MS. And in: Khoshghadam, M., A. Khanal, and W. J. Lee. "Numerical Study of Production Mechanisms and Gas-Oil Ratio Behavior of Liquid-Rich Shale Oil Reservoirs." In SPE Annual Technical Conference and Exhibition. Society of Petroleum Engineers, 2015. DOI: 10.2118/175137-MS. And in: Khoshghadam, Mohammad, A. Khanal, and W. J. Lee. "Impact of Fluid, Rock and Hydraulic Fracture Properties on Reservoir Performance in Liquid-Rich Shale Oil Reservoirs." In Unconventional Resources Technology Conference, San Antonio, Texas, 20-22 July 2015, pp. 31-48. Society of Exploration Geophysicists, American Association of Petroleum Geologists, Society of Petroleum Engineers, 2015. DOI: 10.2118/178579-MS. And in: Khoshghadam, Mohammad, A. Khanal, and W. J. Lee. "Numerical study of impact of nano-pores on gas-oil ratio and production mechanisms in liquid-rich shale oil reservoirs." In Unconventional Resources Technology Conference, San Antonio, Texas, 20-22 July 2015, pp. 1799-1817. Society of Exploration Geophysicists, American Association of Petroleum Geologists, Society of Petroleum Engineers, 2015. DOI: 10.2118/178577-MS.