四川盆地寒武系盐相关构造及其控油气作用  

Salt-related structure and its control on hydrocarbon of the Cambrian in Sichuan Basin

作　　者：李双建[1,2] 孙冬胜[1] 郑孟林[1] 孟宪武[3] 

机构地区：[1]中国石化石油勘探开发研究院,北京100083 [2]中国石化构造与储层实验室,北京100083 [3]中国石化西南油气分公司,贵州贵阳550001

出　　处：《石油与天然气地质》2014年第5期622-631,638,共11页Oil & Gas Geology

基　　金：国家科技重大专项(2011ZX05005-001);国家重点基础研究发展计划(973计划)项目(2012CB412800);国家自然科学基金项目(40739904)

摘　　要：四川盆地东部和南部中、下寒武统广泛发育膏盐岩层系,形成了多种样式的盐相关构造。依据露头、钻井和地震资料分析,认为四川盆地寒武系膏盐岩形成于克拉通内局限台地环境,具有时代老、埋藏深、厚度分布不均、膏多盐少及伴生岩石类型多样等特点。受膏岩和盐岩流动性差异、构造挤压、基底断裂和滑脱作用等多种因素影响,膏盐岩层系相关构造分层性明显。盐上层表现为背斜、推覆体和断块背斜构造;盐层表现为盐枕构造、盐缩颈形成的鱼尾构造和岩盐塑性流动构造;盐下层则表现为受复杂基底断裂控制的叠瓦冲断和背冲断块构造。寒武系膏盐岩为震旦系-下寒武统目的层系的油气聚集提供了优质的封盖条件;同时,膏盐岩自身参与的TSR反应(硫酸盐热化学还原反应)和表生溶蚀也可以有效地改善储层的储集物性。更重要是,寒武系膏盐岩作为区域滑脱层对盐上和盐下震旦系-下古生界构造变形起着重要控制作用,形成一系列含油气构造圈闭。从盐相关构造的发育特点来看,鄂西-渝东区的盐下断背斜和川东南地区的盐上断背斜是有利的勘探目标。Gypsolyte-salt layers of the Middle-Lower Cambrian are widely developed in the southern and eastern Sichuan Basin,resulting in a variety of salt-related structures. Analyses of outcrop,drilling and seismic data reveal that the gypsolyte-salt layers of the Cambrian in Sichuan Basin formed on restricted intra-craton platform and has the characteristics of old age,deep burial depth,uneven thickness,more gypsolyte and less salt,and various associated rock types. The gypsolyte-salt related structures show obvious layering due to the differential gypsolyte and salt mobility,tectonic compression,basement faults,and detachment,. The post-salt structures are mainly anticlines,thrust nappes and faulted-anticlines. The structures within the salt layers are mainly salt pillows,tail structures and plastic flow structures. The presalt structures mainly include imbricate thrusts and pop-up structures controlled by the complex basement faults. The gypsolyte-salt layers of the Cambrian provide good sealing conditions for hydrocarbon accumulation in the Lower Sinian-Lower Cambrian. Meanwhile,they also can improve reservoir quality through TSR and supergene dissolution that they are involved. Even more important,as a region detachment layer,the gypsolyte-salt rock plays an important role in the structural deformation of the post-salt and pre-salt Sinian-Lower Paleozoic,resulting in a series of hydrocarbon traps. According to the characteristics of gypsolyte-salt related structures,the pre-salt faulted anticlines in western Hubei-eastern Chongqing and post-salt faulted anticlines in southeast Sichuan are the favorable exploration targets.

关 键 词：盐相关构造 膏盐岩 控油气作用 勘探目标 寒武系 四川盆地 

分 类 号：TE121.2[石油与天然气工程—油气勘探]