Qinjun Kang

Understanding pore‐scale fluid flow is critical for guiding field‐scale production of unconventional reservoirs. In this chapter, the recent progress on pore‐scale simulations and digital rock physics of fluid flow in unconventional reservoirs is presented. First, the physics of flow in unconventional rocks that deviates from the continuum fluid mechanics theory is discussed. Then recent developments in modifying the lattice Boltzmann methods to account for the nanoscale physics are presented in detail. Finally, various simulation examples using the modified lattice Boltzmann methods are given, including gas slippage, adsorption, surface tension, water flow, two phase flow considering slip effect, and vapor condensation. It is shown that through proper modification of boundary conditions, collision operators, and/or force terms, the lattice Boltzmann method can be an effective tool to simulate physics of flow in unconventional reservoir rocks at the pore scale.

Fractures play an important role in providing preferred flow pathways in low-permeability shale matrix and significantly enhance its permeability. They can improve gas production for shale gas development but can also increase the risks for leaking of CO2 or brine from geological storage sites. In this chapter, a generalized lattice Boltzmann (LB) model for fluid flow through porous media is adopted to simulate fluid flow in matrix-fracture systems and to predict the effective permeability k(eff). Discrete fracture-matrix networks (DFN) are constructed using line fractures and elliptical fractures in 2D and 3D systems, respectively. Power law relationships are observed between k(eff) and fracture density in the DFN. Further, the combined finite discrete element method (FDEM) is adopted to simulate fracture propagation process. Dynamic evolution of k(eff) during the propagation is simulated using the LB model. The results show that power law relationship between k(eff) and fracture density is also obeyed.