燃爆压裂是近年提出的一项针对页岩气储层压裂的变革性技术,研究燃爆冲击载荷的改造 作用可为燃爆压裂法的应用提供基础依据。 选取川南泸州区块龙马溪组一段页岩样品,采用自制 的燃爆冲击载荷试验系统开展燃爆冲击实验,用计算机断层扫描仪(μ-CT)扫描燃爆前后样品,通 过数字图像处理技术提取孔隙并重构,统计孔隙数据获取孔径分布,研究燃爆冲击载荷作用前后孔 裂隙系统的变化特征。 结果表明:1 瞬时升温产生的热应力破坏页岩中层理弱介质,使其内部微 裂缝失稳、扩展乃至贯通;受燃爆冲击载荷作用影响,页岩中心位置应力集中,应力波冲击使页岩形 成多条裂缝,产生大量孔隙;2 燃爆冲击载荷作用对页岩储层孔裂隙系统的改造显著受层理和微 裂缝的影响;层理和微裂缝越发育,改造后形成的裂缝网络越复杂;受黏土矿物等塑性矿物的约束 性降低,储层应用范围更广;3 瞬时升温和燃爆冲击载荷作用对页岩复杂缝网的形成和扩展均有 显著促进作用;燃爆冲击载荷作用更加有效地改造页岩储层孔裂隙系统并产生大量连通性孔裂隙, 连通性孔隙增加约 67%。 这一研究从微观层面证实燃爆冲击载荷作用能有效改造页岩储层。

Combustion-explosion fracturing is a revolutionary technology developed in recent years for the fracturing of shale gas reservoirs. The research on the transformation effect of explosive impact load can provide a basis for the ap- plication of explosive fracturing. Shale samples from theLongmaxi Formation in the Luzhou Block,South Sichuan were selected. Specially designed equipment for combustion and explosion impact load was used to carry out blast impact test. A μ-CT scanning on the samples was conducted before and after the explosion. The pore space was ex- tracted and reconstructed by digital image processing technique,and the pore size distribution was obtained by statisti- cal pore data analysis to study the change characteristics of the pore fracture system before and after the impact load of combustion and explosion. The findings demonstrate that:1 The thermal stress generated by instantaneous tempera- ture rise destroys the laminated weak medium in the shale,causing destabilization,expansion and even penetration of the internal micro-fractures. Due to the effect of combustion explosion impact load,the central location of the shale stress concentration,and the impact of stress wave causes shale to form many cracks and a large number of pores. 2 The transformation of pore fracture system of shale reservoir under the action of combustion explosion impact loading is significantly affected by bedding and original micro-fractures. The more developed the bedding and the original micro fractures are,the more complex the fracture network developed after the transformation. With the reduction of plas- tic minerals such as clay minerals,the application range of reservoirs is wider. 3 Both the rise in instantaneous tem- perature and the combustion explosion impact loading significantly contribute to the formation and expansion of com- plex shale pore and fracture networks, where the combustion explosion impact loading is more effective in modifying the pore and fracture system of shale reservoirs,generating a large number of connected pore and fractures, and the connectivity pore increases by approximately 67%. This research demonstrates at the microscopic level that the effect of combustion-explosion impact loading can effectively modify shale reservoirs.