四川盆地三叠系气田型深层富钾锂卤水勘探历程、进展与展望

Exploration Process,Progress,and the Prospect of Deep Potassium-rich Lithium-rich Brine in Triassic Gas Field of Sichuan Basin

四川盆地三叠系嘉陵江组和雷口坡组不仅是常规天然气的主要赋存层位,同时也形成和储存了富含钾锂等关键元素的卤水资源。本文梳理总结了四川盆地三叠系气田型深层卤水勘探进程、成因机理、富集规律方面的进展和认识,并对潜在的研究重点进行了展望。四川盆地三叠系气田型深层卤水中钾、锂等关键金属元素均达到了工业品位,随着全球对锂资源需求的增大,由起初的“气钾兼探”逐渐向“气钾锂综合勘探”过渡。四川盆地三叠系深层富钾锂卤水的成因机制大体上相同,其中干旱气候条件下古海水的蒸发浓缩致使卤水中的钾锂富集;高温高压下含钾/锂元素的杂卤石/绿豆岩与埋藏卤水发生水岩反应,进一步促进了钾锂的富集;淋滤作用也是卤水中钾元素富集的重要成因。深层卤水主要储集于各类白云岩中,其富集主要受断裂、裂缝发育带和背斜等构造控制,富集规律可归纳为“孔隙裂缝储卤、断裂运卤、背斜核部富卤”。基于目前四川盆地气田型深层卤水的勘探现状和不足,未来应该加强地球物理勘探集成新技术的研发、资源评价方法与体系的优化、含高品位伴生元素新层系的勘探以及气田型卤水有效开发利用技术的研究。未来有望在四川盆地气田型深层卤水继续取得新的找矿突破。

The Triassic Jialingjiang and Leikoupo Formations in the Sichuan Basin are the key reservoirs of conventional natural gas.They also host brine resources rich in critical elements such as potassium and lithium.In this study,we reviewed and summarized the progress and current understanding of the exploration processes,genetic mechanisms,and enrichment patterns of deep brine in the Triassic gas fields of the Sichuan Basin while also identifying areas for future research.The concentrations of key metal elements,such as potassium and lithium,in the deep brine of the Triassic gas fields have reached industrial grade levels.With the increasing global demand for lithium resources,the initial focus on“gas potassium and exploration”gradually transitioned to a more comprehensive approach that includes“gas,potassium,and lithium comprehensive exploration”.The formation mechanisms of the Triassic deep potassium-and lithium-rich brines in the Sichuan Basin are largely similar.The evaporation and concentration of paleo-seawater under arid climatic conditions facilitated the enrichment of potassium and lithium in the brine.Subsequently,under conditions of high temperature and pressure,polyhalite/green bean rock containing potassium/lithium reacts with the buried brine,which further promotes the enrichment of potassium and lithium.Leaching is an important cause of K enrichment in brines.Deep brine is mainly stored in various dolomites and its enrichment is primarily controlled by faults,fracture development zones,and anticlines.The enrichment patterns can be summarized as“pore-fracture brine storage,fracture brine transport,and anticline brine enrichment”.Given the current status and challenges of exploring gas-field-type deep brines in the Sichuan Basin,future research should focus on the development of new integrated technologies for geophysical exploration,the optimization of resource evaluation methods and systems,exploration of new strata with high concentrations of associated elements,and the effective development and utilization of gas-field-type brines.These advancements are expected to lead to significant breakthroughs in the exploration of deep brine resources in the Sichuan Basin.