关键词: 岩石断裂力学, 水力压裂, 裂缝扩展, 临界长度, 地层界面, 隔层, 裂缝扩展模型

Abstract:

There are three types of possible behavior of hydraulic fractures during extending along the height,including the stopping extension,extending along formation interface and directly penetrating into separating formation,when the hydraulic fractures meet the formation interface.The three types of extending behavior of hydraulic fractures were analyzed by using rock fracture mechanics.The judging criterion for the extending behavior was presented.The layered earth stress,layered rock mechanics parameters,formation interface effect,reservoir thickness and operating parameters were taken into consideration in the model.The research results indicated that there existed a critical fracture length for the case of stopping extension.The hydraulic fractures will extend along the formation interface or penetrate into the separating formation when the length of fracture is longer than the critical length.The method was introduced to calculate the critical fracture length.For the case of directly penetrating into the separating formation,the vertical growth dimension of fracture was estimated by the sectional calculation of stress intensity factors and their superposition.An application was given for validating the research results.

Key words: rock fracture mechanics, hydraulic fracturing, fracture extending, critical length, formation interface, separating formation, fracture extending model