采矿与岩层控制工程学报2025，Vol.7Issue(4)：28-53,26.DOI:10.13532/j.jmsce.cn10-1638/td.2024-1472
煤系岩层真三轴水力压裂裂缝扩展规律研究
The study on the propagation laws of hydraulic fractures in coal measure strata under true triaxial conditions
摘要
Abstract
To obtain the variation patterns of hydraulic fracture propagation trajectories caused by abrupt lithological changes of formation interfaces,the propagation behavior of hydraulic fractures in coal measure strata under different combined lithological modes was investigated through true triaxial hydraulic fracturing experiments and inversion of direct current resistivity method.The influence mechanisms of in-situ stress,lithological strength difference,and formation interface strength on the propagation trajectories of hydraulic fractures were analyzed.The results show that the morphology of hydraulic fractures in coal measure strata exhibits significant asymmetric characteristics,and the following seven modes are identified:single,cross,"T"-shaped,"+"-shaped,"I"-shaped,"干"-shaped,and complex fractures.The hydraulic fracturing pressure curve can be divided into four stages:rapid increase to fracture initiation pressure,sudden pressure drops,stable fluctuation,and pressure decrease after pump shutdown.When hydraulic fracture propogation encounters natural fractures or formation interfaces,the pressure curve shows obvious fluctuations,and the sudden pressure drop value is negatively correlated with the complexity of the hydraulic fracture.The influence of in-situ stress on hydraulic fractures is related to the direction of the maximum principal stress and the vertical stress difference coefficient.When the maximum principal stress is vertical,the larger the vertical stress difference coefficient,the easier it is for the hydraulic fracture to penetrate the interface and continue to propagate vertically.The lithological strength difference influences the propagation trajectory of hydraulic fractures as well.When a hydraulic fracture initiates and propagates from soft rock to a formation interface,its propagation trajectory mostly stops and extends along the formation interface;whereas when a hydraulic fracture initiates in hard rock,the larger the lithological strength difference ΔS,the easier it is for the fracture to penetrate the formation interface and to continue to propagate vertically.Otherwise,it tends to extend along the formation interface.关键词
煤系岩层/水力压裂/岩性组合模式/岩层界面/裂缝扩展Key words
coal-measure strata/hydraulic fracturing/combined lithological model/rock strata interface/fracture propagation分类
矿业与冶金引用本文复制引用
马军强,李学华,张佳琦,姚强岭,种照辉,杨森,袁钰鑫..煤系岩层真三轴水力压裂裂缝扩展规律研究[J].采矿与岩层控制工程学报,2025,7(4):28-53,26.基金项目
国家自然科学基金资助项目(51874285,52474180) （51874285,52474180）
