塔里木盆地库车坳陷克拉苏盐下深层大气田形成机制与富集规律  

Formation Mechanism and Enrichment Regularities of Kelasu Subsalt Deep Large Gas Field in Kuqa Depression,Tarim Basin

作　　者：王招明[1] 

机构地区：[1]中国石油塔里木油田公司,新疆库尔勒841000

出　　处：《天然气地球科学》2014年第2期153-166,共14页Natural Gas Geoscience

基　　金：国家科技重大专项"塔里木盆地库车前陆冲断带油气勘探开发示范工程"(编号:2008ZX05046)资助

摘　　要：库车坳陷具有丰富的天然气资源，继克拉2大气田发现后，近年来在克拉苏断裂下盘克深区带发现了大北、克深等大型气田。以克深、大北大气田为例，详细论述了克拉苏盐下深层大气田的形成机制与富集规律，认为侏罗系三叠系煤系烃源岩5Ma以来生气强度和生气速率达到极大值[高达（160～320）×10^8m^3／km^2和15～20mg／（gTOC·Ma）]，为高效气源灶。克拉苏冲断带叠置在供烃中心之上，充足的气源是大北一克深气田天然气富集的物质基础。区域性巨厚膏盐岩盖层限制构造冲断突破、有效保护储层、高效保存油气，是盐下油气富集的重要保证。克深一大北分层滑脱收缩变形，盐下冲断叠瓦构造成排成带，广泛分布的低孔砂岩储层，为天然气富集提供了有利空间。克深一大北地区盐下深层构造的形成与区域构造挤压关系密切，主要是晚喜马拉雅期强烈冲断挤压形成，上新世第四纪是克拉苏构造带形成的主要时期，主体构造基本都是在库车组中晚期定型；而生烃史研究也表明烃源岩主要生气期在库车组沉积以来，主生气期与构造定型期的良好匹配决定了克拉苏冲断带盐下晚期高效成藏，是该区深层形成大气田的重要原因。It is well known that there were rich gas resources in Kuqa Depression. Since the discovery of Ke la-2 large gas field,Dabei gas field and Keshen gas field have been discovered in the down block of Kelasu fault in Keshen structural zone. Taking Keshen and Dabei gas fields as an example, formation mechanism and enrichment regularities of Kelasu subsah deep large gas field were discussed in detail in this paper. It was considered that the Jurassic-Triassic coal-measure source rocks were a high effective gas kitchen, gas generation intensity and rate reached the maximum （corresponding to （160～320）×10^8m^3/km^2 and 15- 20mg/gToc ·Ma,respectively） in recent 5Ma. Kelasu structural zone overlapped the hydrocarbon supplying centers,and sufficient gas source supplied a material basis for gas accumulation of Dabei-Keshen gas field. Regionally distributed thick gypsum rock restricted structure thrust breakthrough, protected reservoirs ef- fectively and preserved oil and gas with high-efficiency, which provided an important assurance. Bedding- delamination contractional deformation, subsalt imbricated thrust structures and widely distributed low po- rosity sandstone reservoir provided a favorable storage space for oil and gas accumulation in Dabei-Keshen area. The formation of subsah deep structure is related to compressional deformation as a result of later Hi- malayan episodic strong thrust compression. Pliocene-Quaternary is the main stage for the formation of Kelasu structural zone and the main structure finalized in Middle-Later Kuqa Formation. Gas generation history research showed the main gas generation stage began in sedimentary period of Kuqa Formation. Later high-efficiency oil and gas accumulation of Kelasu subsalt structural zone was determined by a better match of main gas generation stage and structure forming stage, which is an important reason for the for- mation of deep large gas field in Kelasu play zone.

关 键 词：深层天然气 克深气田 煤成气 成藏机制 克拉苏构造带 库车坳陷 

分 类 号：TE121.11[石油与天然气工程—油气勘探]