摘要
近年来,水力压裂技术逐渐被应用到煤层气井的压裂施工中.为了深入研究水力压裂时裂缝在煤层中的扩展情况,本文从理论上分析了裂缝壁面的受力状态,根据最大拉应力准则,给出了原级裂隙扩展的力学条件,进而分析了空间壁面裂隙扩展的力学条件.在此基础上,利用RF-PA2D-Flow有限元数值软件模拟了高压水作用下煤层裂缝的扩展延伸过程.结果表明:当水压达到理论临界值时,模型中裂缝便向前扩展;当模型中的裂缝转向延伸时,缝端压力完全满足理论分析的空间壁面裂隙延伸条件;通过对裂缝的扩展模拟,再现了裂缝延伸、转向等过程;此法可有效地预测裂缝的长度,为现场煤层压裂提供参考.
The hydraulic fracture technology has been gradually applied to methane wells m recent years. In order to descrihe the fracture propagation in coal seams, the load-bearing condition of fracture surface in coal seams was theoretically analyzed and the propagation condition of pre-existing fractures and cracks in space fracture surface under high pressure water were achieved with the maximum tensile strain criterion. Based on this, the propagation of hydraulic fracture in coal seams was simulated by RFPA2D-Flow. The results show that 1） the fractures in simulation model propagate forward when the water pressure reaches the theoretical critical value, and 2） when the direction of fracture turns around, the water pressure at the fracture end meets the condition of the propagation of wall fractures. By the simulation, the process of propagation and turnaround of fractures are reconstructed. So the method can effectively predict the length of hydraulic fractures.
出处
《采矿与安全工程学报》
EI
北大核心
2008年第2期231-234,238,共5页
Journal of Mining & Safety Engineering
基金
国家重点基础研究发展计划(973)项目(2005CB221502)
江苏省自然科学基金项目(BK2004033)
