川西地区天然气勘探新思路

New ideas of gas exploration in western Sichuan basin

为寻找四川盆地川西地区天然气勘探新区块、新领域,通过分析区内10余条地质露头剖面、40多口井的钻井资料及大联片地震资料,建立了地质露头、钻井和地震3套构造层序、6套沉积层序。提出区内经历了陆缘海湾型沉积、海陆过渡型沉积和封闭—半封闭的前陆盆地型沉积,在上述盆地中分别发育了不同的沉积体系和砂体,构成不同的含油气组合与油气藏类型。进而建议:①勘探重点应从目前的主攻上三叠统须家河组二段转移到须家河组四、六段;②从主攻须家河组转移到海陆并举,兼顾陆相(侏罗系红层);③从背斜圈闭转移到探索非背斜圈闭与页岩气藏。勘探区块也相应从邛西、平落坝、白马、松华区块转移到雾中山、莲花山区块,以及大邑、灌口、苏码头、盐井沟、眉山、汉王区块。勘探方法、研究思路、工程及工艺措施也相应需要更新。

In order to find new blocks and plays for gas exploration in the western Sichuan basin,three structural sequences and six sedimentary sequences are recognized based on over 10 outcrop sections,drilling data of over 40 wells and seismic data in the study area. Epicontinental estuarine facies,continental-oceanic transitional facies,and enclosed to semi-enclosed foreland basin facies are recognized in the study area. Different sedimentary systems and sandbodies are developed in these basins and they form different plays and reservoir types. The following proposals are presented. The focus of exploration should be shifted from the second member of the Triassic Xujiahe formation at present to its fourth and sixth members,from the Xujiahe formation to both the marine and continental facies (the Jurassic red bed),and from anticlinal traps to non-anticlinal traps and shale gas reservoirs. The exploration areas also should be shifted correspondingly from Qiongxi,Pingluoba,Baima and Songhua blocks to Wuzhongshan and Lianhuashan blocks,as well as Dayi,Guankou,Sumatou,Yanjinggou,Meishan and Hanwang blocks. The exploration methods,ideas,engineering and technologes should also be upgraded.