You Lijun, Xue Kunlin, Kang Yili, Liao Yi, Kong Lie
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China.
ScientificWorldJournal. 2013 Nov 28;2013:572140. doi: 10.1155/2013/572140. eCollection 2013.
Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment.
气体滑脱效应是多孔介质中气体流动不同于液体流动的一种重要机制。一般认为，多孔介质渗透率越低，气体流动的滑脱效应越严重。基于气体滑脱效应的定义，针对致密砂岩储层不同渗透率级别，设计并开展了随岩心样品出口回压升高的实验。本研究考察了致密砂岩中气体滑脱效应的极限压力，并分析了毛管压力曲线特征参数。实验结果表明，当回压达到极限压力时，气体滑脱效应可消除。当回压超过极限压力时，对于给定岩心样品，实测气体渗透率为相对稳定值，其变化范围小于3%。还发现极限压力随渗透率降低而增大，且与岩心样品孔隙结构密切相关。研究结果对多孔介质中气体渗流相关研究有重要影响，有助于减少室内实验工作量。
