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Studies on Hydraulic Fracturing Stress Measurement Assisted by Water Jet Boreholes Slotting

喷水钻孔开槽辅助水力压裂应力测量研究

基本信息

批准号：
04555150
负责人：
MIZUTA Yoshiaki
金额：
$ 6.4万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

项目摘要

Both laboratory tests and in-situ tests for hydraulic fracturing stress measurement assisted by water jet borehole slotting were carried out.In the laboratory tests, Pairs of deep longitudinal slots were made by abrasive water jet from the inside of boreholes which were drilled in large scale mortar specimens.Confining pressures were applied to the specimens by flatjacks and a loading frame. Hydraulic fracturing tests were carried out in the sections including the slots and the fractures on the plane of prolongation of the slots were produced. Shut-in pressures of the fractures were then measured.It was shown in the tests that the stresses detected were slightly greater than the stress applied.In the in-situ tests, both the longitudinal slots and the circular slots perpendicular to the boreholes were made in the hard rock at the site which is about 700 meters below the surface. Hydraulic fracturing tests were carried out and it was confirmed that the longitudinal and transverse fractures on the plane of prolongation of the longitudinal slots and the circular slots, were produced, respectively. Re-opening pressures were then measured. The test results show that the maximum and the minimum principal stresses detected were nearly equal to the stresses which were measured using the same borehole by the double fracture method.Numerical simulation based on the boundary element method of fracture extension by internal pressurization at the borehole section in an infinite solid was also carried out. The computed results shows that the turning point of fracture propagation curve movesfarther away from the slit tip with an increase of principal stress ratio and decrease of fluid pressure drop rate induced by the crack increment.

采用磨料水射流在大尺寸砂浆试件上钻孔，在试件上形成一对纵向深槽，通过平板千斤顶和加载架对试件施加围压，进行了水力劈裂应力测量的室内试验和现场试验。在包括槽的部分中进行水力压裂试验，并且在槽的延伸平面上产生裂缝。在现场试验中，在地下700 m处的硬岩中分别开纵向缝和垂直于钻孔方向的圆形缝。进行了水力劈裂试验，证实了在纵向槽和圆形槽的延伸平面上分别产生了纵向和横向裂缝。然后测量重新打开压力。试验结果表明，在同一钻孔中，用双裂缝法测得的最大和最小主应力值与实测应力值接近，并对无限大固体中钻孔段内压裂缝扩展进行了边界元数值模拟。计算结果表明，随着主应力比的增大和裂缝增量引起的流体压降速率的减小，裂缝扩展曲线的转折点向远离裂缝尖端的方向移动。