Experimental and modeling study of the stress-dependent permeability of a single fracture in shale under high effective stress
Experimental and modeling study of the stress-dependent permeability of a single fracture in shale under high effective stress
复制标题
高有效应力下页岩单裂缝应力相关渗透率实验与模型研究
DOI：
10.1016/j.fuel.2019.116078
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发表时间：
2019
期刊：
影响因子：
7.4
通讯作者：
Pan Zhejun
中科院分区：
文献类型：
--
作者：
Zhou Jian;Zhang Luqing;Li Xiao;Pan Zhejun
由于中国页岩气藏生产深度已逐渐超过3500 m，研究高有效应力作用下改造后的页岩气藏渗透率变化具有重要意义。在5 ~ 80 MPa围压条件下，对2个龙马溪页岩压裂样品进行了一系列渗透率测量。实验结果表明，随着有效应力的增加，裂缝试样的表观渗透率急剧下降。裂缝性页岩的固有渗透率随有效应力的增大而减小，Klinkenberg常数基本不变。然后，在裂缝压缩性模型的基础上，建立了应力相关的裂缝渗透率模型。建模结果表明，本文建立的渗透率模型能较好地描述实验数据，样品I和样品II的渗透率模型误差分别为5.63%和2.24%。将该模型与现有渗透率模型的模拟结果进行了比较，结果表明，该模型在较宽的有效应力范围内具有较好的适用性。龙马溪页岩压裂后的平均可压缩性从0.077降低到0.014 MPa−1，有效应力从4.13增加到79.65 MPa，表明裂缝可压缩性具有较强的应力依赖性。研究结果对深部页岩气开发的渗透率变化及产气动态预测具有重要意义。
It is of great importance to investigate the change in the permeability of stimulated shale gas reservoirs under high effective stress because the depths of producing shale gas reservoirs in China have gradually exceeded 3500 m. In this study, a series of permeability measurements were performed on two fractured Longmaxi shale samples under confining pressures from 5 to 80 MPa. Experimental results show that the measured apparent permeability of the fractured samples sharply decreases with effective stress. The intrinsic permeability of fractured shale decreases with increasing effective stress, and the Klinkenberg constant is almost invariable. Then, a stress-dependent fracture permeability model was derived based on the fracture compressibility models. The modeling results indicate that the permeability model derived in this study can accurately describe the experimental data, with errors of 5.63% and 2.24% for samples I and II, respectively. A comparison of the modeling results using this model to those using permeability models available in the literature indicates that the model derived in this study is preferable, especially for a broad effective stress range. Moreover, the average compressibility of fractured Longmaxi shale decreases from 0.077 to 0.014 MPa−1with effective stress increasing from 4.13 to 79.65 MPa, showing that fracture compressibility is strongly stress-dependent. The results in this paper will be important for the prediction of permeability change and gas production behavior for the development of deep shale gas.