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对于低渗透储层岩石而言,基于岩石受力变化后发生线弹性变形的假设与实验结果并不相符。为此,采用CMS300覆压测试、岩石力学性质测试、压汞以及铸体薄片观察等实验手段对低渗透储层岩石覆压变形特征进行分析,结果发现实验岩样在应力增大的整个过程中发生的是软塑性变形→弹性变形→塑性变形过程。低渗透岩石在覆压实验中表现出的强应力敏感性是由其变形特征决定的,岩石在覆压增大的初始阶段发生微量软塑性变形是造成渗透率大幅下降的主要原因,其与低渗透岩石的泥质及胶结物含量较高、孔喉通道狭窄有关。基于实验研究结果,定义了新的岩石应力敏感系数来表达渗透率与有效覆压的关系,与实验数据有更好的相关性,并且能够方便地将任意常规岩样渗透率转换成储层条件下的渗透率,具有实际的工程应用价值。
For low-permeability reservoir rock, the assumption of linear elastic deformation based on the change of rock stress is not consistent with the experimental results. Therefore, the deformation characteristics of rock cover in low-permeability reservoirs are analyzed by the means of overburden test of CMS300, rock mechanics test, mercury intrusion and observation of cast thin sheet. The results show that during the whole process of stress increase What happens is soft plastic deformation → elastic deformation → plastic deformation process. The low-permeability rock shows strong stress sensitivity in the overburden test, which is determined by its deformation characteristics. The small amount of soft plastic deformation of the rock during the initial stage of overburden pressure is the main reason for the significant decrease of permeability. Penetration of rock mud and cement content is higher, throat pore throat narrow. Based on the experimental results, a new rock stress-sensitivity coefficient is defined to express the relationship between permeability and effective overburden and has better correlation with the experimental data, and the permeability of any conventional rock sample can be easily converted into reservoir conditions Under the permeability, with practical engineering value.