页岩储层甲烷原位燃爆压裂理论与技术研究进展

Strategic conception and research progress of methane in-situ deflagration fracturing technology in shale reservoirs

页岩气通常以吸附和游离状态赋存于暗色泥页岩、高碳泥页岩等产气岩中,是一种清洁、高效的能源资源.相比于常规天然气藏,页岩气储层普遍具有低孔隙度、低渗透率的特点,压裂改造提高页岩气采收率是“十四五”期间我国能源开发的重点攻关方向.本文创新性提出了一种页岩储层甲烷原位燃爆压裂的技术构想,该技术利用页岩气储层原位解吸产生的甲烷气体与注入的助燃剂协同燃爆,产生高温高压气体冲击压裂页岩储层,创造立体裂缝网络,为页岩气提供高效运移通道.论文全面分析了甲烷原位燃爆压裂的技术构想、可行性以及关键科学问题,包括甲烷-助燃剂协同起爆机制及燃爆压力波传播特性、甲烷燃爆对井筒介质的瞬态冲击动力学响应特征与控制机制、多级燃爆压裂立体缝网逐级构建及效果评价技术等3个关键研究内容,基本涵盖了当前甲烷原位燃爆压裂理论与技术研究的最新进展.研究认为,燃爆冲击载荷作用对页岩复杂缝网的形成和扩展具有显著促进作用,甲烷燃爆压裂不需要消耗大量的压裂液,也不涉及火工品的地上运输和混合等过程,安全、经济和环保优势非常明显,是一项前瞻性、变革性技术,有助于实现我国页岩气开采技术的创新突破.

ZHAI Cheng;QU Zhanqing;DENG Shouchun;SUN Weifu;LUO Ning;WANG Yu;LIU Ting;GUO Tiankui;WU Feipeng;LIU Jing;SONG Zhengchang;CHEN Shangbin;YANG Wei;CAI Chengzheng;School of Safety Engineering,China University of Mining and Technology;National Engineering Research Center for Coal Gas Control,China University of Mining and Technology;School of Petroleum Engineering,China University of Petroleum (East China);Institute of Rock and Soil Mechanics,China Academy of Sciences;State Key Laboratory of Explosion Science and Technology,Beijing Institute of Technology;School of Mechanics and Civil Engineering,China University of Mining and Technology;School of Low-Carbon Energy and Power Engineering,China University of Mining and Technology;School of Resources and Geosciences,China University of Mining and Technology;State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology;Shale gas is generally stored in dark mudstone, high-carbon mudstone and other gas-producing rocks in adsorbed and free states. It is a clean and efficient energy resource. Compared with conventional natural gas reservoirs, shale gas reservoirs generally have low porosity and low permeability. Using fracturing technology to improve shale gas recovery rate is a key research direction for China's energy development during the 14th Five-Year Plan period. This paper proposes an innovative in-situ methane deflagration fracturing technology for shale reservoirs. This technology utilizes the in-situ desorbed methane gas and injected combustion-assisting agents to cooperatively deflagrate and generate high-temperature and high-pressure gas to impact and fracture the shale reservoir, creating 3D fracture networks to provide efficient migration pathways for shale gas. The paper comprehensively analyzes the conception and feasibility, key scientific issues, and main research directions of the in-situ methane deflagration fracturing technology. It includes three key research contents: the in-situ synergistic ignition mechanism and pressure wave propagation characteristics of methane-combustion assisting agent, the transient impact dynamics response and control mechanism of methane deflagration on wellbore media, and the multi-stage pulsed deflagration fracturing for hierarchical 3D fracture network construction and evaluation technologies. These basically cover the latest progress in the current theoretical and technical research on methane in-situ deflagration fracturing. The study believes that the methane in-situ deflagration fracturing method does not require a lot of water and fracturing fluids, nor does it involve the ground transportation and underground placement and mixing of explosives. Its safety, economic and environmental advantages are very significant. It is a forward-looking and revolutionary technology that will help achieve innovative breakthroughs in China's shale gas development technologies.