Laboratory investigation on fracture initiation and propagation behaviors of hot dry rock by radial borehole fracturing  

作　　者：Wenchao Zou Zhongwei Huang Zhaowei Sun Xiaoguang Wu Xu Zhang Zixiao Xie Yaoyao Sun Tengda Long Han Chen Zikang Wang Ruimin Gao Xinyu Qin 

机构地区：[1]National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum,Beijing,102249,China [2]Geothermal Energy Science and Technology Research Institute,Dali,671000,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2025年第2期775-794,共20页岩石力学与岩土工程学报(英文)

基　　金：supported by the National Science Fund of China for Major International(Regional)Joint Research Project(Grant No.52020105001);the National Natural Science Foundation of China(Grant Nos.52304053 and 52204019).

摘　　要：Creating complex and interconnected fracture networks between injection and production wells is crucial for exploiting hot dry rock(HDR)geothermal energy.However,the simple planar fractures created by conventional hydraulic fracturing,primarily controlled by in situ stress,fail to connect directionally with the target well.This study proposes a novel stimulation method,i.e.radial borehole fracturing,which shows great potential for guiding the directional propagation of fractures.The fracture initiation and propagation behaviors of high-temperature granite under radial borehole fracturing are investigated and compared with those of conventional fracturing.Three-dimensional morphological scanning and reinjection tests are used to quantitatively evaluate fracturing performance.Additionally,the influences of key parameters,including rock temperature,in situ stress,injection rate,fluid viscosity,azimuth of the radial borehole,and the number of radial boreholes on the fracture morphology and breakdown pressure are investigated.The results show that radial borehole fracturing can effectively guide the initiation and propagation of fractures along the radial borehole.The breakdown pressure of radial borehole fracturing can be reduced by 14.1%–43.7%compared to conventional fracturing.A higher fluid-rock temperature difference reduces the directional propagation range of fractures guided by the radial borehole.Increases in the vertical density of radial boreholes,injection rate,and fluid viscosity enhance the guiding ability of radial boreholes.Furthermore,there is a competitive relationship between in situ stress and the azimuth of radial boreholes in controlling fracture propagation.This research provides a viable alternative for the directional connection of injection-production wells in HDR reservoirs.

关 键 词：Hot dry rock(HDR) Enhanced geothermal system(EGS) Radial borehole Hydraulic fracturing Fracture propagation 

分 类 号：TE3[石油与天然气工程—油气田开发工程]