摘要
水压致裂测试技术起源于石油的增产,现已发展成为测量地壳应力的一种有效方法。近年来,为实现热干岩发电,该技术也用来制造人工热交换面。为研究水压致裂过程中裂缝的扩展机制,在北京市房山区花岗岩体中开展大流量水压致裂试验。试验是在一个深301 m的新鲜完整的岩石压裂孔中进行的。在注水孔周围200 m×200 m的范围内,间距25 m呈网格状共布置49个自然电位测点,压裂过程中,对注水孔周围电位的变化进行测量。在压裂孔中深110～140 m内选取3段没有天然节理的部位进行水压致裂。测量结果表明,在图域内自然电位异常呈现椭圆形分布,随注水流量增大异常值增大。正的椭圆形异常有2条长轴线,一条轴线相对另一条有一定的扭转,它们的方向与裂缝和节理的方位一致,水流入裂缝和天然节理中。通过自然电位确定的裂缝扩展方向与水压致裂应力测量的水平最大主压应力方向一致。
Hydraulic fracturing has originated as a stimulation technique ofoil reservoir, and has been developed as a rock stress measurement technique. Recently, it has also been developed to create artificial heat exchange surfaces for hot dry rock power generation system. To study the mechanism of crack extension by hyduaulic fracturing, the mass hyduaulic fracturing experiments are carded out in granodiorite at Fangshan District, Beijing, China. A FR borehole of 301 m deep in a fresh and intact rock is used for the experiments. During the fracturing process, electrical potential changes around the injection well are measured on the surface. Measurement points, total 49 points, distribute around the injection well on the grid with interval of 25 m in an area of 200 m× 200 m. Hyduaulic fracturing experiments are carded out by selecting 3 spots without natural joints from the section of 110 m to 140 m in the depth of the FR borehole. These spontaneous potential（SP） anomalies show elliptical distribution in the map view. The values of the anomalies increase with the water flow. Most of the measurement results show that the positive elliptical anomalies have two long axes or one long axis with distortion to different directions. Thesedirections coincide with the orientations of fracture and joint. In these cases, water is considered to flow into both the fracture and joint. The directions of crack extension obtained from the SP measurement agree with those evaluated one from the hydraulic fracturing stress measurement.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2006年第7期1425-1429,共5页
Chinese Journal of Rock Mechanics and Engineering
基金
中日合作研究项目"水压致裂裂缝形成与扩展机制研究"
关键词
岩土力学
自然电位
水压致裂
地应力
rock and soil mechanics
spontaneous potential（SP）
hyduaulic fracturing
geostress
