青西地区沙三段断层封闭性综合研究

Sealing capacity of faults in Tertiary Shahejie 3 Member, Qingxi area

山东东营凹陷北部青西地区断裂复杂,构造圈闭发育。开展断层封闭性研究是该区效益勘探的关键。采用定性和定量相结合的方法对断层封闭性进行综合分析。通过明确断层活动演化期次,分析其与烃源岩生、排烃期的对应关系及与油气运聚的时空耦合关系,在地质上定性描述断层开启和封闭过程;再利用现有钻井、测井、录井资料,进行断层两盘泥岩涂抹(SGR)和压力特征定量分析;最后,对研究区断层封闭性进行综合评价。研究结果表明:该区渐新统沙三段南北向断裂断裂规模小,断层活动期结束早,具备有利的封闭条件;东西向断裂规模大,断裂长期活动,趋向于开启,具有分段特征,介于开启或封闭状态。

Qingxi area,northern Dongying sag,Shandong Province,is characterized by complex faults and existence of structural traps.And sealing capacity of faults is critical for beneficial exploration.In this study,the sealing was investigated by both qualitative and quantitative methods.After the faulting phases were defined,their relationship with hydrocarbon generation and expulsion of source rock and their time-space coupling correlation to hydrocarbon migration and accumulation were analyzed,and the opening and closing processes of faults were qualitatively described.Then,shale gouge ratio(SGR)and pressure characteristics of two fault sides were analyzed quantitatively based on some drilling,well-logging and mud-logging data.Finally,the sealing capacity in Qingxi area was evaluated comprehensively.It is indicated that the NS-trending faults in Oligocene Tertiary Shahejie 3 Member are smaller in scale and their activity ended early,being favorable for the sealing performance whereas the EW-trending ones are larger and active for a long time,making them have the characteristic of fragmentation and presenting in open or closed states.