Influence of Grain Size Heterogeneity and In-Situ Stress on the Hydraulic Fracturing Process by PFC<SUP>2D</SUP> Modeling

作     者：Han, Zhenhua Zhou, Jian Zhang, Luqing 

作者机构：Chinese Acad Sci Inst Geol & Geophys Key Lab Shale Gas & Geoengn Beijing 100029 Peoples R China Chinese Acad Sci Inst Earth Sci Beijing 100029 Peoples R China Univ Chinese Acad Sci Coll Earth Sci Beijing 100049 Peoples R China 

出 版 物：《ENERGIES》 (Energies)

年 卷 期：2018年第11卷第6期

页      面：1413页

核心收录：

基　　金：National Natural Science Foundation of China [41572312, 41672321, 41502307] Strategic Priority Research Program of the Chinese Academy of Sciences [XDB10050202] China Postdoctoral Science Foundation [2018M630204] 

主　　题：hydraulic fracturing grain size heterogeneity in-situ stress particle flow code modified fluid-mechanically coupled model 

摘      要：A modified fluid-mechanically coupled algorithm in PFC2D was adopted in this article to study the influence of grain size heterogeneity and in-situ stress on hydraulic fracturing behavior. Simulated results showed that the in-situ stress and grain size heterogeneity significantly affect the initiation, growth, and spatial distribution of the hydraulic fractures: (1) the initiation and breakdown pressure are gradually reduced with the increase of the grain size heterogeneity;(2) with increased in-situ stress, the initiation and breakdown pressure increase, and the reduction effect of grain size heterogeneity on the breakdown pressure becomes more obvious;(3) in grain size homogeneous rock, the initiation pressure decreases with increasing in-situ stress ratio, however, the initiation pressure of grain size heterogeneous rock is almost unaffected by the in-situ stress ratio;(4) The in-situ stress ratio and grain size heterogeneity affect the spatial distribution of hydraulic fractures simultaneously. When the in-situ stress ratio is larger than 1, the hydraulic fractures propagate substantially along the direction of the maximum principal stress. When the in-situ stress ratio is 1, the initiation position and extension direction of hydraulic fractures are random and complex fracture networks can easily develop in a grain size homogeneous model.