结合CT技术的火山岩水力裂缝延伸实验  

Experimental study on propagation of hydraulic fracture in volcanic rocks using industrial CT technology

作　　者：贾利春[1] 陈勉[1] 孙良田[2] 孙志宇[2] 张伟[1] 朱千千[1] 孙振[1] 金衍[1] 

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室 [2]中国石化石油勘探开发研究院

出　　处：《石油勘探与开发》2013年第3期377-380,共4页Petroleum Exploration and Development

基　　金：国家重大科技专项(2011ZX05009-005)

摘　　要：为了准确获知火山岩水力压裂过程中裂缝的平面和空间扩展形态,采用真三轴水力压裂模拟系统,对火山岩天然岩样进行了室内压裂模拟实验,在实验前后采用工业CT技术对岩样进行扫描,并对CT图像进行三维重建和可视化处理。对岩样的CT图像进行分析发现:经过压裂的火山岩内部裂缝在延伸过程中会连通部分天然孔隙,但裂缝并未沿着天然孔隙发育密集的区域延伸;裂缝延伸方向整体上与最大水平地应力方向趋于一致。对岩样的裂缝三维图和可视化图进行分析发现:火山岩压裂中的破裂压力梯度高,导致其难于形成裂缝。对岩样的造缝能力进行分析发现:井眼附近的岩石力学特性是影响岩石造缝能力的重要因素,火山岩往往具有较高的杨氏模量和抗压强度,造缝能力低。因此,火山岩现场压裂改造中的关键问题之一是降低破裂压力梯度。To understand the planar and three-dimensional geometry of hydraulic fractures in volcanic rocks, a hydraulic fracturing simulation experiment was conducted using the large-scale triaxial hydraulic fracturing test system in laboratory. The industrial CT technology was employed to scan the volcanic rock sample before and after fracturing experiment to observe hydraulic fractures. The 3D tomograms and visualized images were obtained from the original CT images. The original CT images indicate that the hydraulic fractures in volcanic rock cross natural pores and/or microcracks, but the fractures don＇t propagate in the area where natural pores are abundant. The fractures propagate along the maximum horizontal stress direction. The 3D tomograms and visualized images show that it is difficult to create hydraulic fractures in volcanic rocks due to a high fracture pressure gradient. The ability of fracturing in volcanic rock was analyzed, which indicates that the rock mechanical properties near the borehole are the key factors controlling the initiation and propagation of hydraulic fractures. With relatively high Young＇s modulus and compressive strength, volcanic rocks are generally low in fracturing ability. The key in hydraulic fracturing of volcanic rocks is to bring down the fracture pressure gradient.

关 键 词：火山岩 水力压裂 模拟实验 CT图像 

分 类 号：TE357.1[石油与天然气工程—油气田开发工程]