坚硬顶板岩层水力压裂主裂缝中高速压裂液的湍流效应
Turbulence effect of high-speed fracturing fluid in hydraulic fracturing main fracture of hard roof rock
-
摘要:
本文以内蒙古巴彦高勒煤矿31103工作面为研究背景,采用断裂力学、材料力学结合岩石力学的理论分析方法,以及数值模拟软件进行实验方案设计,对31103工作面上覆10 m厚硬顶板水力压裂卸压防冲合理施工工艺参数开展研究。首先,建立高压水流驱动下压裂岩层中主裂缝起裂扩展力学模型,得到实际条件下水力压裂裂缝起裂的临界水压与扩展裂缝几何尺寸的关系式。其次,根据Comsol流固耦合模拟实验软件对高压水流在钻孔及裂缝中流动造成的孔壁表面压力与裂缝扩展边界条件的计算收敛结果可知,在封孔、注水、憋压直至裂缝贯通水压骤降的施工过程中,压裂液的流动状态与岩石钻孔和裂缝表面张力之间存在相互作用关系。最后,考虑现场施工反馈的数据信息,确定适合巴彦高勒煤矿31103工作面厚硬顶板的合理水力压裂施工工艺参数。
Abstract:Taking 31103 working face of Bayan Gaole Coal Mine in Inner Mongolia as the research background, the theoretical analysis methods of fracture mechanics, material mechanics and rock mechanics are adopted, and the experimental scheme is designed with numerical simulation software.The reasonable construction process parameters of hydraulic fracturing, pressure relief and impact prevention covered with 10 m thick hard roof plate on 31103 working face are studied based on the field measured fracturing effect.Firstly, the mechanical model of main fracture initiation and propagation in fractured rock stratum driven by high-pressure water flow is established, and the relationship between the critical water pressure of hydraulic fracturing fracture initiation and the geometric size of extended fracture under actual conditions is obtained.Secondly, according to the calculation convergence results of Comsol fluid solid coupling simulation experimental software on the hole wall surface pressure and fracture propagation boundary conditions caused by the flow of high-pressure water in the borehole and fracture, it can be seen that the interaction between the flow state of fracturing fluid and the surface tension of rock borehole and fracture in the construction process of hole sealing, water injection, pressure holding until the sudden drop of fracture penetration water pressure.Finally, considering the data information fed back from the on-site construction, the reasonable hydraulic fracturing construction process parameters suitable for the thick and hard roof of 31103 working face of Bayan Gaole Coal Mine are finally determined.