A calculation model for shale reservoir matrix apparent permeability considering different shale lithofacies through 2D digital core

Abstract

Permeability is an important parameter affecting shale gas development. Shale has strong heterogeneity, and the permeabilities of the shale matrices in different lithofacies vary significantly. To study the seepage ability of shale matrices, the seepage of gas in the shale matrices of different lithofacies was simulated, the permeabilities of the shale matrices of different lithofacies were calculated, and the results were corrected according to the slippage and diffusion effect of shale gas. The calculation results show that the seepage capacities of clay shale with high total organic content and siliceous shale with high total organic content are stronger than those of other shale lithofacies. Finally, based on the permeability and proportion of different lithofacies, a calculation model of the apparent permeability of a shale reservoir considering different shale lithofacies was established. The calculation model of the apparent permeability of the shale reservoir matrix overcomes the spatial limitation of conventional methods. The calculation model can not only intuitively show the control effects of different shale lithofacies on reservoir permeability, but also master the seepage capacity of shale reservoirs in the research block as a whole. The model provides a theoretical basis for the design of shale gas development programmes.

Keywords:

• apparent permeability
• digital core
• shale gas
• shale lithofacies
• shale matrix