孙逊, 张士诚, 马新仿,等.基于高能CT扫描的煤岩水力压裂裂缝扩展研究[J].河南理工大学学报（自然科学版）,2020,39(1):18-25.

SUN X, ZHANG S C, MA X F ,et al.Study on fractures propagation mechanism in coal hydraulic fracturing based onhigh-energy CT scanning technique[J].Journal of Henan Polytechnic University(Natural Science) ,2020,39(1):18-25.

基于高能CT扫描的煤岩水力压裂裂缝扩展研究

孙逊, 张士诚, 马新仿, 邹雨时

中国石油大学（北京）石油工程学院，北京102249

摘要:水力压裂是提高煤层气产量的关键技术，但由于煤岩力学性质的特殊性，使其裂缝扩展规律十分复杂，掌握水力压裂裂缝的形成机制对煤层气开发有着重要的意义。在开采沁水盆地南部区域的大型天然煤岩时，将真三轴水力压裂装置和高能工业CT扫描成像技术相结合，研究了天然裂缝、割理发育情况和地应力对水力压裂裂缝起裂和扩展特征的影响。结果表明：天然裂缝和割理在井筒周围的发育程度决定了水力压裂裂缝的起裂位置和破裂压力，裂缝在基质处起裂的破裂压力显著高于在天然裂缝和割理处起裂的破裂压力；在低水平应力差条件下水力压裂裂缝易沿着天然裂缝和割理随机扩展，随着水平应力差增大，地应力对水力压裂裂缝扩展的控制作用增强，合理的水平应力差范围为2 ~6 MPa，在此条件下易形成一条水力压裂裂缝为主、连通多条天然裂缝为辅的复杂裂缝系统。研究结果可为国内煤储层的水力压裂裂缝预测和压裂设计提供一定的理论参考和设计指导。

关键词:煤岩;水力压裂裂缝;割理;地应力;高能CT扫描技术

doi:10.16186/j.cnki.1673-9787.2020.1.3

基金项目:国家科技重大专项项目（2017ZX05064001 ）

收稿日期:2019/04/09

修回日期:2019/05/20

出版日期:2020/01/15

Study on fractures propagation mechanism in coal hydraulic fracturing based onhigh-energy CT scanning technique

SUN Xun, ZHANG Shicheng, MA Xinfang, ZOU Yushi

College of Petroleum Engineering， China University of Petroleum （ Beijing） ， Beijing 102249 ， China

Abstract:Hydraulic fracturing is a key technology to improve coalbed methane （ CBM） production. However， due to the particular mechanical properties of coal， the rule of hydraulic fracture propagation is very complicated. A well understanding of the hydraulic fracture propagation is of great significance to the development of coalbed methane. In this study， large scale natural coal samples， taken from the south of Qinshui Basin， were conducted on the true triaxial hydraulic fracturing equipment， and the fracture morphologies were described by high-energy CT scanning technique. The test results showed that the development of natural fractures and cleats around well determined the location of fracture initiation and breakdown pressure. The breakdown pressure of fracture initiated in matrix was significantly higher than that in natural fractures and cleats. Meanwhile， hydraulic fractures propagated randomly along natural fractures and cleats under low horizontal stress difference. With the increase of horizontal stress difference， the control ability of in-situ stress on the propagation of hydraulic fractures was enhanced. The reasonable range of horizontal stress difference was 2 ~6 MPa. Under this condition ，it was easy to form a complex fracture system which was composed of a main hydraulic fracture and several secondary fractures. The test results could provide some reference and theoretical guidance for hydraulic fracture prediction and fracturing design parameters optimization in coalbed methane in China.

Key words:coal;hydraulic fracturing fracture;cleat;in-situ stress;high-energy CT scanning technique

基于高能CT扫描的煤岩水力压裂裂缝扩展研究_孙逊.pdf