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.

众所周知，岩石的电阻率被定义为孔隙率，孔隙率间和孔隙流体的电阻率的函数。 Glover等人（1994）在实验中表明，岩石的电阻率也随应力而变化。电阻率对应力的这种依赖性可能是因为孔隙度和孔间连通性应随应力条件而变化。另一方面，当钻孔钻成一个地层时，在钻孔附近引入了应力障碍。从电阻率和应力之间的关系推断出来，应力干扰可能会引起井眼周围电阻率的额外干扰。电阻率干扰应是远程应力的函数，与应力干扰一样。因此，如果我们可以以某种方式测量电阻率分布，则可能有可能估算井眼周围电阻率分布的远程应力。为了实现这一想法，首先，我们通过使用圆柱标本进行实验室实验以在单轴载荷条件下测量岩石的电阻率。然后，我们检查样品在样品的轴向和横向方向上的电阻率如何随轴向载荷而变化。基于这些结果，我们提出了一种新方法，以估算井眼附近电阻率分布的原位应力状态。