Mohr space and its application to the activation prediction of pre-existing weakness  

作　　者：TONG HengMao WANG JianJun ZHAO HaiTao LI Bo HAO HuaWu WANG MingYang 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum [2]Department of Overseas New Ventures Assessment, Research Institute of Exploration & Development Beijing [3]School of Geology and Geomatics, Tianjin Chengjian University

出　　处：《Science China Earth Sciences》2014年第7期1595-1604,共10页中国科学（地球科学英文版）

基　　金：supported by the China Major National Science & Technology Program of Oil and Gas (Grant Nos. 2011ZX05023-004-012, 2011ZX05006-006-02-01);the National Natural Science Foundation of China (Grant Nos. 41272160, 40772086)

摘　　要：The activation coefficient equations in the"activation criterion of pre-existing weakness"are relatively complex and not easy to apply to specific applications.The relative activity of pre-existing weaknesses is often critical in geological analysis.The Mohr circle can be used only in two-dimensional stress analysis.By applying the"activation criterion of pre-existing weakness"and combining it with numerical analysis,we establish the correspondence between the pole(n,n)of a pre-existing weakness plane and its orientation in"Mohr space".As a result,the normal stress(n)and shear stress(n)of a pre-existing weakness plane can be readily expressed in Mohr space.Furthermore,we introduce the method and procedures for predicting the activation and relative activation of pre-existing weaknesses in Mohr space.Finally,we apply the Mohr space method and compare the predictions to sandbox modeling results and 3D seismic data.The results show that Mohr space can be used in stress analysis to estimate the activation of a pre-existing weakness in any triaxial stress state.The activation coefficient equations in the ＂activation criterion of pre-existing weakness＂ are relatively complex and not easy to apply to specific applications. The relative activity of pre-existing weaknesses is often critical in geological analysis. The Mohr circle can be used only in two-dimensional stress analysis. By applying the ＂activation criterion of pre-existing weakness＂ and combining it with numerical analysis, we establish the correspondence between the pole （σn, τn） of a pre-existing weakness plane and its orientation in ＂Mohr space＂. As a result, the normal stress （σn） and shear stress （τn） of a pre-existing weakness plane can be readily expressed in Mohr space. Furthermore, we introduce the method and procedures for predicting the activation and relative activation of pre-existing weaknesses in Mohr space. Finally, we apply the Mohr space method and compare the predictions to sandbox modeling results and 3D seismic data. The results show that Mohr space can be used in stress analysis to estimate the activation of a pre-existing weakness in any triaxial stress state.

关 键 词：Mohr space pre-existing weakness activation coefficient relative activity triaxial stress state 

分 类 号：P631.4[天文地球—地质矿产勘探]