Author: SUN Xun ZHANG Shicheng MA Xinfang ZOU Yushi | Time: 2020-01-10 | Counts: |
doi:10.16186/j.cnki.1673-9787.2020.1.3
Received:2019/04/09
Revised:2019/05/20
Published: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