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弹性参数在甜点区预测和页岩气的开发过程中扮演着重要的角色,因此研究等效弹性参数随页岩气储层属性的变化是一项很有意义的工作。研究中我们用X射线CT扫描技术获得了较为精确的页岩样品微观结构图像。从这些图像中,我们可以获得孔隙度和矿物的详细情况,据此,我们构建了三维数字岩心,并应用有限元法对弹性参数进行了数值模拟,其间深入考察了子样选取、网格划分、求解器类型以及边界条件等,该方法易于区别不同的矿物及其百分含量。本文重点研究孔隙度和干酪根含量对弹性参数的影响,计算结果表明,孔隙度和干酪根含量对弹性性质有较大的影响,当孔隙度和干酪根含量增加时,弹性模量降低,且当孔隙度小于0.75%左右、干酪根含量大于3%左右时弹性参数减小速率较缓。因为孔隙度仅仅为4.5%,孔隙中填充油或气对弹性参数的影响甚微。不同岩心样本具有不同的孔隙度和干酪根含量,传统岩石物理实验不仅昂贵而且费时,而数值模拟是基于数字岩心来计算弹性参数,更加经济、方便。本研究证实了将页岩样品的微观结构图像与弹性模量的计算相结合来预测页岩弹性参数的可行性。
The elastic parameters play an important role in the prediction of sweet spot and the development of shale gas. Therefore, it is very significant to study the change of equivalent elastic parameters with the properties of shale gas reservoirs. In the study, we obtained more accurate shale sample microstructure images by X-ray CT scanning. From these images, we can get the porosity and the details of the minerals. Based on this, we constructed a 3D digital core and applied the finite element method to numerical simulation of the elastic parameters. In the meantime, the sub-sample selection, meshing , Solver type and boundary conditions, etc. This method makes it easy to distinguish between different minerals and their percentages. This paper focuses on the influence of porosity and kerogen on the elastic parameters. The calculated results show that the porosity and kerogen have a great influence on the elastic properties. When the porosity and kerogen content increase, the elastic modulus decreases When the porosity is less than 0.75% and the kerogen content is more than 3%, the elastic modulus decreases slowly. Because porosity is only 4.5%, the effect of oil or gas in the pores on the elastic parameters is negligible. Different core samples have different porosity and kerogen content. Traditional rock physics experiments are not only expensive and time-consuming, but numerical simulation is based on numerical core to calculate elastic parameters, which is more economical and convenient. This study confirms the feasibility of predicting shale elastic parameters by combining the microstructure image of shale samples with the calculation of elastic modulus.