乌石凹陷东洼“似花状”断裂发育机制及控藏作用  

Developmental mechanism and reservoir-controlling effects of“flower-like”faults in Wushi East subsag

作　　者：向飞 邓勇 胡林 胡德胜 陈丽君 柳智萱 XIANG Fei;DENG Yong;HU Lin;HU Desheng;CHEN Lijun;LIU Zhixuan(CNOOC China Limired,Zhanjiang Branch,Zhanjiang,Guangdong 524057,China;CNOOC China Limited,Hainan Branch,Haikou,Hainan 570000,China)

机构地区：[1]中海石油(中国)有限公司湛江分公司,广东湛江524057 [2]中海石油(中国)有限公司海南分公司,海南海口570000

出　　处：《中国海上油气》2022年第6期44-53,共10页China Offshore Oil and Gas

基　　金：中海石油(中国)有限公司重大科技项目“南海西部油田上产2000万方关键技术研究(编号:CNOOC-KJ 135 ZDXM 38 ZJ)”部分研究成果。

摘　　要：乌石凹陷东洼是已证实富生烃凹陷,但中浅层一直未获规模性发现,主要原因是中浅层“似花状”断裂的发育机制和控藏作用认识不清,油气富集规律不明确。本文通过区域应力背景、先存构造、平衡剖面、断裂特征及活动性等综合分析,研究了该洼陷内“似花状”断裂的发育机制及控藏作用。研究认为,受顺时针旋转伸展应力场和先存七号断裂控制,乌石凹陷东洼具有“早期正向拉伸、后期斜向拉伸”的演化特征,在后期斜向拉伸过程中,断隆构造内部发育的一系列对倾断裂受先存七号断裂派生走滑应力分量作用扭动形成“似花状”断裂。靠近先存七号断裂,“似花状”断裂受扭动作用强,多发育断鼻圈闭,圈闭有效性好;远离先存七号断裂,“似花状”断裂受扭动作用弱,多发育断块圈闭,圈闭有效性较差。花瓣处断裂多切割流二段烃源岩,沟源能力好,利于成藏;花心处断裂多收敛于流二段地层之上,沟源能力较差,不利于成藏。靠近先存七号断裂附近花瓣处的圈闭是乌石凹陷东洼中浅层油气勘探的有利目标。The Wushi East subsag is proved to be rich in hydrocarbon,but its oil and gas have not been discovered on a large scale in medium and shallow formations.The main reasons are that the developmental mechanism and reservoir-controlling effects of“flower-like”faults in the medium and shallow formations are not well understood,and the oil and gas enrichment laws are not clear.Through comprehensive analysis of regional stress background,pre-existing structure,balanced section,fault characteristics and activity,this paper studies the developmental mechanism and reservoir-controlling effects of"flower-like"faults in Wushi East subsag.The research shows that,controlled by the extensional stress field with clockwise rotation and the pre-existing No.7 fault,the Wushi East subsag underwent the evolution process of“early forward extension and late oblique extension”,and during the process of late oblique extension,a series of antithetic faults developed in the fault-uplift structure were wrenched to form“flower-like”faults under the strike-slip stress component derived from the pre-existing No.7 fault.Close to the pre-existing No.7 fault,the“flower-like”faults were strongly affected by wrenching,and fault-nose traps were developed with good trap effectiveness;Away from the pre-existing No.7 fault,the“flower-like”faults were weakly affected by wrenching,and fault-block traps were developed with poor trap effectiveness.The faults at the petal mostly cut the hydrocarbon source rocks of the 2 rd member of Liushagang formation,with good channeling ability,which was conducive to reservoir formation;the faults at the core mostly converged on the the 2 rd member of Liushagang formation,with poor channeling ability,which was not conducive to reservoir formation.The traps of the petal near the pre-existing No.7 fault are favorable targets for medium and shallow oil and gas exploration in Wushi East subsag.

关 键 词：乌石凹陷 “似花状”断裂 斜向拉伸 走滑应力分量 圈闭有效性 

分 类 号：TE122.2[石油与天然气工程—油气勘探]