It is essential to understand methane mass transport through micro/nano pores in shale for the reservoir evaluation and gas production prediction. There distributes large numbers of pores, including micropores, mesopores and macropores. Kerogen, as the organic matter in shale, is rich in micro/meso-pores with width less than 50 nm. Multiple gas transport mechanisms coexist in porous media with complex pore size distribution, including viscous flow and Knudsen diffusion of free gas, and surface diffusion of adsorbed gas. During pressure depletion of a reservoir, the adsorbed gas desorbs into pore space as additional “free gas”, and meanwhile, diffuses along the surface of nanopores in porous media. In this paper, experimental and calculated results for the gas transport in nanopores of shale matrix are presented, accounting for the effect on dynamic transport process of surface diffusion. The main conclusions are: (1) the equilibrium time for gas transport process decreases very quickly with temperature and less gas produced under higher temperature; (2) higher saturation pressure could accelerate the process and increase the amount of produced gas; (3) the mathematical model considers the effect of kerogen on the methane transport. Compared with the models not considering the effect of kerogen, the model presented in this paper fits the experimental results better. This study provides an experimental investigation of the methane mass transport through shale matrix considering the effect of kerogen, which is a relatively simple but information-rich technique for the assessment of shale gas targets.
|Number of pages
|Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences
|Published - Aug 2017
- Dynamic experiment