[CCoE Notice] PhD Dissertation: Numerical Modeling and Simulation of Natural Gas Transport in Heterogeneous Shale Rocks using the Lattice Boltzmann Method

[Grayson, Audrey A]

PhD DEFENSE STUDENT: Yang Ning
DATE: Tuesday, April 25, 2017
TIME: 9:00 AM
PLACE:  Energy Research Park (ERP); Building 9, Room 123
DISSERTATION CHAIR: Dr. Guan Qin
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TITLE:
Numerical Modeling and Simulation of Natural Gas Transport in Heterogeneous Shale Rocks using the Lattice Boltzmann Method

Shale gas has become a significant type of unconventional resources due to its remarkable success of commercial production in North America and China. Shale gas reservoirs are characterized by ultra-low porosity and permeability, and the production mainly depends on rock characteristics including pore size distribution, organic richness, natural/factitious fracture network, etc. A significant portion of shale gas is adsorbed in nanopores within kerogen pockets that are 200nm to 500nm in size. Gas flow in nanopores under typical formation pressure/temperature falls into the slip flow or the transitional flow regime. The extreme confinement and adsorption/desorption effects make the flow mechanism in organic nano-pores very complex, and Darcy's law cannot effectively describe this transport phenomena due to its continuum assumption. Understanding the flow mechanisms of natural gas in organic nano-pores is essential for correct prediction of long-term production. In addition, gas shale is composed of many mineral components, such as organic matter, clay components, carbonate, quartz, pyrite, etc. Moreover, pre-existing natural fractures significantly influence the transport properties in shale. Due to the strong heterogeneity of shale rocks, transport properties at nano/micro-scale are not representative to macroscopic-scale rock samples, so there is a need to develop an integrated upscaling procedure to obtain macroscopic-scale transport properties as well as maintain nano/micro-scale information.

In this dissertation, we first developed a pore-scale numerical model by incorporating inter-molecular and adsorptive forces into the MRT lattice Boltzmann method (LBM) to capture gas adsorption in organic nanopores. This model is able to simulate gas flow with the adsorption effect and has been applied to natural gas flow in 2D and 3D complex kerogen pore structures. Second, we developed a novel upscaling workflow to predict the macro-scale transport properties of gas shales by coupling the LBM with the molecular dynamics simulations based on three-level imaging techniques, i.e., FIB-SEM, Nano-CT, and Micro-CT. The proposed workflow integrates nanometer-scale, micrometer-scale, and centimeter-scale simulations, and calculates macro-scale transport properties while significantly reducing the loss of fine-scale information. Finally, we developed a unified grayscale LBM model to simulate multiphase flow at core-scale for highly fractured and vuggy formations. For porous media consisting both matrix and large void spaces, this model recovers to hydrodynamic equations that can freely switch to the multiphase Darcy equation, multiphase Forchheimer equation, or the standard multiphase Navier-Stokes equations based on the porosity and effective transport properties.
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