A New Strategy and Its Verification for In-situ Measurements of the Maximum and Minimum Stresses at Deep Depths by Hydraulic Fracturing

水力压裂原位测量深部最大最小应力新策略及其验证

基本信息

批准号：
18360429
负责人：
ITO Takatoshi
金额：
$ 11.4万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18360429/
关键词：
Hydraulic fracturing In-situ stress In-situ measurement Reopening pressure High stiffness Deep depth Over coring BABHY BABHT

项目摘要

Hydraulic fracturing is suitable in principle for in-situ stress measurements at deep depths. However, as has been pointed out recently, its current testing systems and procedure involve essential problems which have to be solved before putting the principle into practice. The most serious problem is associated with the hydraulic compliance of fracturing systems. For measuring the reopening pressure, it is necessary to use the fracturing system with sufficiently small compliance. If not, there is no way to estimate the maximum horizontal stress from the reopening pressure assuming a vertical borehole, even though the maximum horizontal stress is the greatest concern in the stress measurement. This limitation makes it difficult to apply hydraulic fracturing for the stress measurement, because the compliance of the conventional system is so large. Taking into account of these facts, we have proposed recently a new method which will allow us to measure both of the maximum and minimum stresses by in-situ tests of hydraulic fracturing at a depth greater than a few km. We have proceeded to test and verify the method step by step so far through laboratory and field experiments using a borehole of 80 m in depth drilled from the ground surface at Matsushiro. Finally, we succeeded to apply the method to an in-situ test of hydraulic fracturing at a depth of 811 m in a vertical borehole drilled from the ground surface at Tazawako.

水力压裂原则上适用于深部地应力测量。然而，正如最近所指出的，其现有的测试系统和程序涉及一些基本问题，在将这一原则付诸实践之前必须解决这些问题。最严重的问题与压裂系统的水力顺应性有关。为了测量重新开启压力，需要使用柔度足够小的压裂系统。如果不是，则无法根据假设垂直钻孔的重新打开压力来估计最大水平应力，即使最大水平应力是应力测量中最关心的问题。这种限制使得水力压裂难以应用于应力测量，因为传统系统的柔量太大。考虑到这些事实，我们最近提出了一种新方法，该方法使我们能够通过几公里以上深度的水力压裂现场试验来测量最大和最小应力。到目前为止，我们已经通过实验室和现场实验，使用从松代地表钻出的 80 m 深的钻孔，逐步对该方法进行了测试和验证。最终，我们成功将该方法应用于田泽湖地面垂直钻孔深度811 m的水力压裂现场试验。