Effects of Cracks and Geometric Parameters on the Flow in Shale

[Image: see text] In recent years, shale oil/gas has become increasingly important in global energy. The natural pores of shale are mainly of micro–nano sizes and have the cross-scale characteristics, which makes the traditional method difficult and impractical in studying the seepage of shale. In order to obtain the characteristics of seepage of the crack-pore-throat system, the lattice Boltzmann method and dimensional analysis were used to study the seepage in an idealized crack-pore network. The influences of the geometric factors, including crack location, crack opening, and interval between two vertical neighbor throats and boundary conditions on the seepage were studied. The results show that the slip boundary conditions enhance the seepage rate. The enhancement with slip coefficients is nonuniform. The total flux is nearly equal when the crack is near either the inlet or outlet, but larger than that when the crack is located in the middle of the model. The flux ratio between the main throats when the crack is located near the outlet is the greatest. When the crack is near the outlet, the water channel is the largest possible while it is not easy to form when the crack is in the middle. With increase in the opening ratio of the crack-to-throat, the total flow of the system increases. The increase degree decreases with the increasing opening ratio. When the opening ratio is greater than 9, the increase in flux becomes very small. If the crack-pore-throat system is very uniform or even symmetric, the flow rate in the vertical throat/crack is very small. Hence, it is not beneficial to the gas/oil production and gas/oil displacement.