Pore-scale simulation of gas-water flow in low permeability gas reservoirs
来源期刊：中南大学学报(英文版)2014年第7期
论文作者：CAO Ting-kuan(曹廷宽) DUAN Yong-gang(段永刚) YU Bo-ming(郁伯铭) FANG Quan-tang(方全堂) WANG Rong(王容)
文章页码：2793 - 2800
Key words：low permeability sandstone; X-ray computed tomography; pore-scale modeling; pore structure; gas-water flow
Abstract: A novel method was developed to establish a realistic three dimensional (3D) network model representing pore space in low permeability sandstone. Digital core of rock sample was established by the combination of micro-CT scanning and image processing, then 3D pore-throat network model was extracted from the digital core through analyzing pore space topology, calculating pore-throat parameters and simplifying the shapes of pores and throats. The good agreements between predicted and measured porosity and absolute permeability verified the validity of this new network model. Gas-water flow mechanism was studied by using pore-scale simulations, and the influence of pore structure parameters, including coordination number, aspect ratio and shape factor, on gas-water flow, was investigated. The present simulation results show that with the increment of coordination number, gas flow ability in network improves and the effect of invading water on blocking gas flow weakens. The smaller the aspect ratio is, the stronger the anisotropy of the network is, resulting in the increase of seepage resistance. It is found that the shape factor mainly affects the end points in relative permeability curves, and for a highly irregular pore or throat with a small shape factor, the irreducible water saturation (Swi) and residual gas saturation (Sgr) are relatively high.
CAO Ting-kuan(曹廷宽)1, DUAN Yong-gang(段永刚)1, YU Bo-ming(郁伯铭)2, FANG Quan-tang(方全堂)1, WANG Rong(王容)3
(1. State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation
(Southwest Petroleum University), Chengdu 610500, China;
2. School of Physics, Huazhong University of Science and Technology, Wuhan 430074, China;
3. Exploration and Development Research Institute,
PetroChina Southwest Oil and Gasfield Company, Chengdu 610041, China)
Abstract:A novel method was developed to establish a realistic three dimensional (3D) network model representing pore space in low permeability sandstone. Digital core of rock sample was established by the combination of micro-CT scanning and image processing, then 3D pore-throat network model was extracted from the digital core through analyzing pore space topology, calculating pore-throat parameters and simplifying the shapes of pores and throats. The good agreements between predicted and measured porosity and absolute permeability verified the validity of this new network model. Gas-water flow mechanism was studied by using pore-scale simulations, and the influence of pore structure parameters, including coordination number, aspect ratio and shape factor, on gas-water flow, was investigated. The present simulation results show that with the increment of coordination number, gas flow ability in network improves and the effect of invading water on blocking gas flow weakens. The smaller the aspect ratio is, the stronger the anisotropy of the network is, resulting in the increase of seepage resistance. It is found that the shape factor mainly affects the end points in relative permeability curves, and for a highly irregular pore or throat with a small shape factor, the irreducible water saturation (Swi) and residual gas saturation (Sgr) are relatively high.
Key words:low permeability sandstone; X-ray computed tomography; pore-scale modeling; pore structure; gas-water flow
