基于四参数随机生长模型的页岩储层应力敏感分析

页岩储层的应力敏感性是影响其后期开发效果的关键因素，从微观的角度深入认识其应力敏感机理及其影响因素对页岩气的开发具有重要意义。借助四参数随机生长模型构建了不同孔隙度和不同孔隙大小分布的岩心样本，利用弹性力学理论模拟了不同有效应力作用下各个岩心孔隙半径的分布变化及其对岩心固有渗透率的影响，深入分析了孔隙大小及其形状因子与上述两者之间的关系。结果表明，导致页岩应力敏感的直接原因是有效应力作用下孔隙面积的减小及孔隙位置的迁移。有效应力的增大使得各孔隙半径均有减小，孔隙半径的减小比例分别与孔隙初始面积和孔隙的形状因子呈正相关关系和负相关关系。在相同的孔隙度条件下，孔隙半径越均匀，平均孔隙半径越小，应力敏感性越强。有效应力的增加使得岩心固有渗透率呈指数型下降且孔隙度越小、固有渗透率越低的岩心，其应力敏感性越强，孔隙度对固有渗透率的影响大于孔隙半径均匀性的影响。

Stress sensitivity analysis of the shale reservoir by the quartet structure generation set

The stress sensitivity of permeability in the shale reservoir is the key factor influencing its later development effect. It is of great significance for shale gas development to deeply understand its stress sensitivity mechanism and its influencing factors from the microscopic point of view. In this paper, core samples with different porosity and pore size distribution are constructed by means of the quartet structure generation set. The variation of pore radius distribution and its influence on intrinsic permeability of cores under different effective stress are simulated by using elasticity theory. The relationship between pore size and shape factor and the above two parameters is deeply analyzed. The results show that the direct cause of shale stress sensitivity is the decrease of pore area and the migration of pore position under effective stress. With the increase of effective stress, the pore radius decreases. The proportion of reduction of pore radius is positively and negatively correlated with the initial pore area and the pore shape factor, respectively. Under the same porosity condition, the more uniform the pore radius, the stronger the stress sensitivity. With the increase of effective stress, the intrinsic permeability of core decreases exponentially, and the smaller the porosity and the lower the intrinsic permeability, the stronger the stress sensitivity of core, and the effect of porosity on intrinsic permeability is obviously greater than that of pore radius uniformity.