基于各向异性双孔等效模型的页岩气地层地应力预测方法  

Prediction method of in-situ stress in shale gas formation based on anisotropic dual pore equivalent model

作　　者：卿鹏程 漆乔木 汤鑫宇 QING Pengcheng;QI Qiaomu;Tang Xinyu(School of Geophysics,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]成都理工大学地球物理学院,成都610059

出　　处：《物探化探计算技术》2024年第6期647-655,共9页Computing Techniques For Geophysical and Geochemical Exploration

基　　金：国家自然科学基金项目(NSFC42274178)。

摘　　要：根据富有机质页岩的岩石物理特征,提出了一种新的各向异性双孔等效模型的建立流程,并以此为基础实现了页岩地应力的有效预测。新模型考虑了页岩气地层中包括矿物成分(有机质、粘土、石英等),含气饱和度以及发育的微裂缝等因素的综合影响。首先视页岩地层为具有垂直对称轴的横向各向同性介质,针对页岩较为复杂的微观孔隙结构进行简化处理,将孔隙空间分为硬孔隙空间和软孔隙空间(裂缝孔隙)两部分。通过构建等效矿物背景基质,孔隙添加及流体替换三个步骤实现了富有机质页岩模型的建立。基于模型对横向各向同性页岩的五个独立弹性模量进行计算,并通过伊顿公式对孔隙压力进行估计,最终利用各向异性地应力模型实现对页岩地层水平地应力的预测。将该方法应用于四川盆地永川页岩区块的井资料,对比凯赛尔声发射实验和模型预测结果,两者具有较好的一致性,验证了双孔模型假设以及基于岩石物理的页岩地应力计算方法的适用性。Based on the petrophysical characteristics of organic-rich shale,establishing an anisotropic dual-porosity model for shale in the Yongchuan area is proposed.On this basis,the effective prediction of in-situ stress is realized.The new model comprehensively considers the influence of organic matter,clay,quartz,and other minerals,pore gas saturation,and micro-crack development in Yongchuan shale gas formation.Firstly,shale’s complex microscopic pore structure is simplified and divided into hard pore space and soft pore space(crack pore).The shale formation is regarded as a transversely isotropic medium with a vertical axis of symmetry.The equivalent model is established by building an anisotropic mineral matrix,a dual-pore skeleton,and fluid replacement.Based on the rock physics model,the five independent elastic moduli of transversely isotropic shale are predicted,the Eaton formula calculates the pore pressure,and the horizontal in-situ stress of shale formation is estimated by using the anisotropic in-situ stress model.Comparing the results of the Kaiser acoustic emission experiment and model prediction,there is a good consistency,which verifies the validity of the dual-porosity model and the applicability of the in-situ stress prediction workflow.

关 键 词：页岩 岩石物理 各向异性 地应力 孔隙压力 

分 类 号：P618.13[天文地球—矿床学]