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Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs

Hatami, Mohammad
http://orcid.org/0000-0002-3961-4216
http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796

Abstract Details

2021, Doctor of Philosophy (PhD), Ohio University, Mechanical Engineering (Engineering and Technology).
This dissertation focuses on multiscale analysis in shale to improve understanding of mechanical and transport properties in shale gas reservoirs. Laboratory measurements of the effects of constant confining pressure (CCP), and constant effective stress (CES) on permeability were coupled with multiscale finite element simulations and the development of a comprehensive apparent permeability model to study the mechanical behavior of shale and transport mechanisms in shale. Predicting long-term production from gas shale reservoirs is a challenging task due to changes in effective stress and permeability during gas production. Unlike coal, the variation of sorbing gas permeability with pore pressure in shale does not always feature a biphasic trend under a constant confining pressure. The present contribution demonstrates that the biphasic dependence of permeability on pore pressure depends on a number of physical and geometrical factors, each with a distinct impact on gas permeability. This includes pore size, adsorption isotherm, and the variation of gas viscosity with pore pressure. In the first part, a single-capillary model was proposed for the apparent permeability of real gas in shale. Results indicated that the biphasic relation between apparent permeability and pore pressure is prevalent when the sorbing gas flows in sufficiently small pores. In addition, the effects of sorption isotherm and internal resistance of non-ideal gas to flow were shown to be non-trivial and could not be ignored. In the second part, experimental measurements were conducted on an intact Utica shale sample under constant confining pressure (CCP) and constant effective stress (CES) conditions to better understand how apparent permeability evolves over time. The average pore diameter of the sample is determined using nitrogen adsorption analysis. In low-permeability porous media, such as shale, gas slippage is more significant at low pore pressure, and using the Klinkenberg’s theoretical model overestimates the apparent permeability. Therefore, a conceptual model based on the second-order slip boundary condition was developed to study the apparent permeability behavior with pore pressure. Results from the apparent permeability predicted by the proposed model reasonably matched against the experimental data, but deviated from the model using Klinkenberg’s assumption at low pore pressures. These findings indicated that permeability under the CCP and CES conditions are dominated by gas slippage at low pore pressures, but as pore pressure increases, poroelastic effects become more significant. Moreover, it was found that the nonlinearity between the apparent permeability and pore pressure was more pronounced at small pores sizes and could be explained through more pronounced gas slippage in viscous flow. Finally, the thermomechanical behaviors of a solid-gas mixture were studied using the asymptotic expansion homogenization (AEH) method coupled with the finite element method to understand how porosity and pore density have effects on thermo-hydro-mechanical behaviors and transport properties of shale and how solid and gas interaction effect on permeability. It was found that increasing porosity results in a reduction of homogenized properties such as elastic stiffnesses, thermal expansion coefficients, and thermal conductivity, while the apparent permeability increases. In addition, under applied loading, micro stress distribution strongly influenced by pore clusters and pores sizes. It was shown that the apparent permeability at the microscale is two orders of magnitude smaller than the apparent permeability at the macroscale.
David Bayless (Advisor)
Alireza Sarvestani (Committee Member)
John Cotton (Committee Member)
Singer Marc (Committee Member)
David Drabold (Committee Member)
127 p.
Chemical Engineering; Energy; Geophysics; Mechanical Engineering; Petroleum Engineering
Apparent permeability; Gas slip; Mechanical properties; Multiscale analysis; Shale; Transport properties

Recommended Citations

Citations

  • Hatami, M. (2021). Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796

    APA Style (7th edition)

  • Hatami, Mohammad. Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs. 2021. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796.

    MLA Style (8th edition)

  • Hatami, Mohammad. "Multiscale Analysis of Mechanical and Transport Properties in Shale Gas Reservoirs." Doctoral dissertation, Ohio University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1614950615095796

    Chicago Manual of Style (17th edition)

ohiou1614950615095796
173
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This open access ETD is published by Ohio University and OhioLINK.