A novel numerical model of gas transport in multiscale shale gas reservoirs with considering surface diffusion and Langmuir slip conditions. Issue 4 (29th May 2019)

• Record Type: Journal Article
• Authors: Huang, Ting; Cao, Lina; Yuan, Chengdong; Chen, Peng
• Is Part Of: Energy science & engineering. Volume 7:Issue 4(2019)
• Page Start: 1315
• Page End: 1332
• Publication Date: 2019-05-29
• Subjects: Knudsen diffusion -- Langmuir slip condition -- multistage fractured horizontal well -- shale gas -- surface diffusion; Energy industries -- Periodicals; Energy development -- Periodicals; Power resources -- Periodicals; 621.042
• DOI: 10.1002/ese3.351
• Languages: English
• ISSNs: 2050-0505

Abstract

Abstract: Multiflow mechanisms coexist in shale gas reservoirs (SGRs) due to the abundant nanopores and the organic matter as a medium of gas souring and storage. The gas transport mechanisms in nanopores including bulk gas transfer and adsorption‐gas surface diffusion were already investigated in pore‐scale models, but their effects on actual gas production of multistage fractured horizontal wells in SGRs are not clearly understood, which are crucial for the economic development of unconventional resources. Therefore, a comprehensive apparent permeability (AP) model which couples the surface diffusion of adsorbed gas, slippage flow considering the additional flux generated by surface diffusion based on Langmuir's theory, and Knudsen diffusion is established. The presented model is validated with the experimental data and lattice Boltzmann method (LBM) simulation results. Then, we propose a numerical model which combines multiflow mechanisms in microscale pores and a multistage fractured horizontal well (MSFHW) in macroscale shale gas reservoirs together. The effects of different transport mechanisms on both AP of nanopores and gas production are analyzed thoroughly. The results show that the effect of surface diffusion on the apparent permeability of nanopores is much greater than that on the actual gas production of MSFHW, and the influence of high‐pressure condition must be considered when calculating the surface diffusion coefficient. The presented numerical model has important implications for accurate numerical simulation and efficient development of shale gas reservoirs. Abstract : A comprehensive apparent permeability (AP) model which couples the surface diffusion of adsorbed gas, slippage flow considering Langmuir slip condition, and Knudsen diffusion is established, which is combined with the multistage fractured horizontal well in a macroscale shale gas reservoir simulator.