页岩气储层岩石三维数字岩心建模--以导电性模型为例

3Ddigital core modeling of shale gas reservoir rocks:A case study of conductivity model

由于页岩气储层具有低孔低渗、各向异性突出、矿物组分复杂等特点,作为基础研究的岩石物理实验开展非常困难,三维数字岩心模型的建立可为其物理特性的数值模拟奠定基础,但常规的建模方法并不适用于复杂的页岩气储层。利用页岩气储层的二维SEM—EDS图像获得其各组分的分布特征,选取导电性模拟需要的组分(孔隙、黏土矿物、黄铁矿、有机质等)以及可以体现岩石宏观特性的尺度(40μm^3),选用马尔可夫链—蒙特卡罗(MCMC)法并加以改进,分别构建各微观组分的三维模型,并将这些模型嵌套组合,最终获得包含导电性相关的矿物组分以及原始结构特征的页岩气储层微米级三维数字岩心。对建模方法和建模的结果进行了评价,结果表明建立的数字岩心模型可以进行页岩气储层导电性的数值模拟研究,也为页岩气储层其他物理性质的三维数字岩心建模提供了思路;提出了建模方法中存在的问题和不足,对以后的页岩气储层数字岩心建模方面的研究提出了建议。

Due to the properties of low porosity,low permeability,prominent anisotropy and complex mineral composition,the basic research of shale reservoir rock,and the physical experiments cannot be carried out smoothly.The 3Ddigital core modeling is the foundation for the numerical simulation which could be the replacement of the experimental methods to study the rock＇s physical properties.However,the conventional modeling methods are not applicable to help rebuilding the digital core model of complex rock of shale gas reservoirs.In this paper,the 2DSEM and EDS images of shale gas reservoir rock were used to obtain the distribution characteristics of each composition.The components such as pore,clay,pyrite and organic matters which are needed in electrical conductivity simulation were selected.After choosing the appropriate scale（40μm3）which can reveal the macroscopic features of rocks,the Markov Chain-Monte Carlo（MCMC）method was chosen and improved to build the original 3D model of each micro components respectively.Then the models were nested into each other to form the final micron grade 3D model which contains several components and the characteristics of the original structure.The final model was evaluated and the results showed that the digital core model could be used for conductivity numerical simulation of shale gas reservoir.Using this method,models for the simulation of other physical properties could also be built.The disadvantages of this method were discussed and the suggestions to improve the modeling were given.