Stress sensitivity of tight reservoirs during pressure loading and unloading process
Stress sensitivity of tight reservoirs during pressure loading and unloading process
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DOI：
10.1016/s1876-3804(19)30013-8
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发表时间：
2019-02-01
影响因子：
7.5
通讯作者：
Lei Gang
中科院分区：
文献类型：
--
作者：
Cao Nai;Lei Gang
通过室内致密岩心实验，研究了致密储层在加卸载过程中渗透率随应力变化的滞后现象。基于实验结果，根据赫兹接触变形原理，考虑岩石颗粒的排列和变形，建立了致密储层渗透率滞后与应力相关的定量理论模型，为渗透率损失定量分析提供了依据。将模型计算结果与实验结果进行对比，验证了模型的正确性.研究结果表明，在承压初期，构造变形和原生变形共同作用，岩石渗透率随有效应力的增大而显著降低。当有效应力达到一定值后，构造变形趋于稳定，而原生变形继续，渗透率变化趋于平稳。卸压过程中，随着有效应力的降低，初始变形恢复，而构造变形则不能恢复。因此，渗透率不能完全恢复，应力依赖性滞后是明显的。
Laboratory experiments were conducted on laboratory-made tight cores to investigate the stress-dependent permeability hysteresis of tight reservoirs during pressure loading and unloading process. Based on experiment results, and Hertz contact deformation principle, considering arrangement and deformation of rock particles, a quantitative stress dependent permeability hysteresis theoretical model for tight reservoirs was established to provide quantitative analysis for permeability loss. The model was validated by comparing model calculated results and experimental results. The research results show that during the early pressure-loading period, structural deformation and primary deformation worked together, rock permeability reduced dramatically with increasing effective stress. When the effective stress reached a certain value, the structural deformation became stable while the primary deformation continued; the permeability variation tended to be smooth and steady. In the pressure unloading process, the primary deformation recovered with the decreasing effective stress, while the structural deformation could not. The permeability thus could not fully recover, and the stress-dependent hysteresis was obvious.