In-situ stress monitoring based on variation in electrical property of rock associated with micro-crack closure

基于与微裂纹闭合相关的岩石电特性变化的地应力监测

基本信息

批准号：
11650076
负责人：
ITO Takatoshi
金额：
$ 1.79万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11650076/
关键词：
Non-destructive test Stress measurement Electrical property Specific resistivity Rock In-situ stress Borehole

项目摘要

It is known that electrical resistivity of rocks are defined as a function of porosity, pore inter-connectivity and resistivity of pore fluid. Resistivity of rocks changes with also stress as has been shown experimentally by Glover et al.(1994). Such dependency of resistivity on stress is likely, since porosity and pore inter-connectivity should change with stress condition. On the other hand, when a borehole is drilled into a formation, a stress disturbance is introduced in the vicinity of the borehole. As inferred from the relationship between resistivity and stress, the stress disturbance possibly induces an additional disturbance in resistivity around the borehole. The resistivity disturbance should be a function of remote stresses as same as the stress disturbance. Therefore, it may be possible to estimate remote stresses from resistivity distribution around the borehole, if we can measure the resistivity distribution somehow. To accomplish this idea, first we conduct laboratory experiments to measure resistivity of rock under uniaxial loading condition by using a cylindrical specimen. Then we examine how the specimen's resistivity in axial and transverse directions of the specimen changes with axial loading. Based on these results, we propose a new method to estimate in-situ stress state from resistivity distribution in the vicinity of borehole.

已知岩石的电阻率被定义为孔隙度、孔隙连通性和孔隙流体电阻率的函数。正如 Glover 等人（1994）通过实验证明的那样，岩石的电阻率也会随着应力的变化而变化。电阻率对应力的这种依赖性是可能的，因为孔隙率和孔隙互连性应随应力条件而变化。另一方面，当在地层中钻孔时，应力扰动被引入到钻孔附近。从电阻率与应力之间的关系推断，应力扰动可能会引起钻孔周围电阻率的附加扰动。电阻率扰动应与应力扰动一样是远程应力的函数。因此，如果我们能够以某种方式测量电阻率分布，则可以根据钻孔周围的电阻率分布来估计远程应力。为了实现这个想法，我们首先进行实验室实验，使用圆柱形样本测量单轴加载条件下岩石的电阻率。然后我们检查试样在轴向和横向上的电阻率如何随轴向载荷变化。基于这些结果，我们提出了一种根据钻孔附近电阻率分布来估计地应力状态的新方法。