二叠系栖霞组—茅口组是四川盆地天然气勘探的重点层系,为了寻找栖霞组—茅口组未来天然气勘探的重点方向,在大量钻井、野外露头、测井、地震及地球化学数据等资料分析的基础上,针对四川盆地栖霞组—茅口组的沉积储层关键地质问题进行了研究,并对勘探领域进行了梳理分析.结果表明:①四川盆地栖霞—茅口期主要为台地沉积体系,可以划分为3个层序.除川西台缘带之外,盆内川中—川东地区栖霞组—茅口组在三级层序高位域发育多期高能浅滩,总面积超过4×104 km2.②栖霞组—茅口组主要储层为孔隙-孔洞型白云岩、岩溶缝洞型灰岩以及微孔-微缝型泥灰岩.其中,孔隙-孔洞型白云岩是近期勘探的主要储集岩类型,栖霞组白云岩主要分布在川西广元—北川—雅安—峨眉一带,茅口组白云岩主要分布在宣汉—万州、广元—剑阁地区以及剑阁—广安—丰都一带.③四川盆地栖霞组—茅口组天然气勘探可划分为4个现实领域及2个潜在领域.其中,川北—川中—川东茅二段白云石化滩带是目前中二叠统天然气增储上产最重要的现实勘探领域,而川东茅二下亚段孤立白云石化浅滩有望成为未来最重要的勘探领域之一.

The Permian Qixia and Moukou formations in Sichuan Basin have been the key targets for natural gas exploration since 1950s.With the continuous deepening of the exploration and development,it has been different of the exploration ideas and directions.In order to clarify the next direction of natural gas exploration,based on a combination of drilling,outcrop,logging,seismic and geochemical data,this paper systematically analyses the geological questions and explorational domains of Qixia and Moukou formations.The results indicate that:(1)The Qixia Formation-Maokou Formation in the Sichuan Basin is mainly a platform depositional system,which can be divided into three stratigraphic sequences(SQ1,SQ2,and SQ3 from bottom to top).In addition to the western Sichuan platform margin,the Qixia Formation-Maukou Formation in the central and eastern Sichuan Basin developed a number of high-energy shoals in the highstand system,encompassing an area of over 40,000 km2.This has laid a solid foundation for the development of shoal reservoirs.(2)The primary reservoirs of the Qixia Formation-Maukou Formation are pore-cavity dolomite,karst fractured-vuggy limestone,and microporous-microfractured marlite of which,pore-cavity dolomite is the main reservoir of recently explored.The dolomite of the Qixia Formation is primarily developed in the Guanyuan-Beichuan-Ya'an-E'mei area in the west of the Sichuan Basin,while the main deposits of the Maokou Formation are distributed in Xuanhan-Wanzhou,Guanyuan-Jiange,and Jiange-Guangan-Fengdu area.Karst fractured-vuggy limestone reservoirs are mainly developed in the central Sichuan to southern Sichuan region.Microporous-microfractured marlite reservoirs are mainly distributed in local areas of northern and eastern Sichuan,and the research level is relatively low.(3)Four realistic fields and two potential fields can be distinguished in the Qixia-Maokou formations natural gas exploration in the Sichuan Basin.The dolomitized shoal zone of the Maokou Member 2 in the northern-central-eastern Sichuan Basin is the most significant realistic exploration field for the Middle Permian natural gas storage and production.We need to accelerate the comprehensive evaluation of reservoirs and submit or upgrade natural gas reserves.The isolated dolomited shoal in the lower sub-member of the Maokou Member 2 in the eastern Sichuan Basin is anticipated to be one of the most significant potential exploration field in the future.We need to deepen the research and finely characterize the distribution range of reservoirs,striving to achieve a breakthrough in this field as soon as possible and promote it becoming a replacement field for natural gas exploration.