碎软低渗煤储层强化与煤层气地面开发技术进展

Technology processes of enhancement of broken soft and low permeability coal reservoir and surface development of coalbed methane

我国碎软低渗煤储层分布广泛,然而由于其煤体松软、破碎、渗透性差,常规的直井/水平井煤储层直接压裂技术应用于碎软低渗煤储层强化及其煤层气地面开发的效果并不理想,碎软低渗煤储层煤层气的高效开发是制约我国煤层气产业大规模发展以及煤矿瓦斯高效治理的重要技术瓶颈。在系统分析我国碎软低渗煤储层特征及煤层气地面开发中存在的问题基础上,以水平井为基础井型,围绕间接压裂、应力释放和先固结后压裂3种不同的技术方向,梳理了目前碎软低渗煤储层强化与煤层气地面开发技术进展。归纳评述了以顶板间接压裂、夹矸层间接压裂以及硬煤分层间接压裂为内涵的间接压裂煤层气开发技术,以水力喷射造穴、气体动力造穴、扩孔+水力喷射+流体加卸载诱导失稳造穴、水力割缝为不同应力释放方式的应力释放煤层气开发技术,以及先微生物诱导碳酸钙固结碎软煤储层再进行水力压裂的先固结后压裂煤层气开发技术。间接压裂技术的工程实践探索已有较多积累,在地质条件适宜地区对碎软低渗煤储层强化取得了较好效果,而以应力释放为代表的碎软低渗煤储层强化新技术探索已取得重大进展,并进入工程试验和验证阶段。水平井应力释放技术针对碎软低渗煤储层特性和新的开发原理,其对储层改造潜力更大、煤层气开发效果会更好。基于水平井应力释放技术,围绕扩大应力释放范围、提高煤层气开发效果以及实现煤与煤层气共采3个方面,对碎软低渗煤储层强化及煤层气地面开发技术的发展趋势进行了展望,以期为改善我国碎软低渗煤储层增产改造效果以及提高煤层气单井产量提供参考。

Broken soft and low permeability(BSLP)coal reservoirs are widely distributed in China.However,due to its soft and broken structure and low permeability,the conventional vertical/horizontal well direct fracturing technology is not ideal for the enhancement of BSLP coal seams and the surface development of coalbed methane(CBM).The efficient development of CBM in BSLP coal reservoirs has been an important technical bottleneck restricting the large-scale development of CBM industry and the efficient treatment of coal mine gas control in China.Based on the systematic analysis of the characteristics of BSLP coal reservoirs and the problems existing in the surface development of CBM,the current technological progress in the enhancement of BSLP coal reservoirs and surface development of CBM were reviewed by taking horizontal well as the base well type and focusing on three different technical directions:indirect fracturing,stress relief and consolidation before fracturing.The CBM development technologies of indirect fracturing,including roof indirect fractur-ing,gangue indirect fracturing and hard coal stratification indirect fracturing were summarized.The stress release CBM development tech-nologies using different stress release methods,such as hydraulic jet cavitation,gas dynamic cavitation,mechanical+hydraulic+induced instability coupling cavitation and hydraulic slit,were reviewed.Furthermore,the CBM development technology of first consolidation and then fracturing of BSLP coal reservoirs induced by microorganisms was also summarized.The exploration of indirect fracturing techno-logy has accumulated a lot of engineering practice,and has achieved a good effect on enhancing the BSLP coal reservoirs in areas with suitable geological conditions.The exploration of new technology for enhancing BSLP coal reservoir represented by stress release has also made great progress,and has entered the stage of engineering tests and verification.According to the characteristics of BSLP coal reser-voir and the new development principle,the horizontal well stress release technology has greater potential for reservoir reconstruction and better effect for CBM development.Based on the horizontal well stress release method,the development trend of BSLP coal reservoir en-hancement and surface CBM development technology was forecasted in three aspects:expanding the stress release range,improving the development effect of CBM and achieving the co-production of coal and CBM.It is expected to provide reference for improving the stimu-lation effect of BSLP coal reservoir and increasing the production of CBM well in China.