塔西南拗陷早加里东期正断层活动及油气意义

塔西南拗陷早加里东期正断层活动与寒武-奥陶系油气运聚成藏关系密切。覆盖面积近15×10⁴km²的二维地震资料构造解析表明,塔西南拗陷发育早加里东期正断层,在拗陷北缘断层后期反转形成逆冲推覆构造带,拗陷内仍有该期正断层保留,其活动特征一直以来少有关注。早加里东期正断层向上没有断穿中寒武统,断距普遍较小,呈北东向展布,个别正断层具有同沉积特征。研究认为,塔西南拗陷早加里东期正断层形成与基底断层有关,形成一系列北东向展布的洼槽,其中拗陷中部规模最大,发育震旦纪裂陷槽;正断层活动形成的洼槽或裂陷槽内有寒武系玉尔吐斯组烃源岩沉积;正断层活动有助于寒武系盐下白云岩储层改造,同时也是油气垂向运移的通道。

Early Caledonian normal faults in the southwest depression of Tarim Basin and its hydrocarbon significance

The early Caledonian normal faults have a close relationship with oil-gas migration and accumulation of Cambrian and Ordovician in the southwest depression of Tarim Basin. Fault analysis on 2D seismic data which covers an area about 15×10⁴km² indicates that normal faults developed during the early Caledonian in the depression. Some of them located in the north boundary of the depression moved inversely and a thrust-faulted zone was formed in later fault evolution stage. And the others remained in the inner depression where tectonic activity was not strong. The activity characteristics of those normal faults in the inner depression are less widely noticed until now. The early Caledonian normal faults do not cut across the middle Cambrian with small fault throw in the east-north direction, but some of them possess characteristics of syn-sedimentary fault. Our research results obtained suggest:A. The early Caledonian normal faults was developed along the basement faults and a series of troughs extending in the same direction with normal faults were formed; B. The troughs located in the middle of depression have the biggest scale and developed the Sinian rift trough, and always control the distribution of Cambrian Yuertusi formation source rocks; C. Again, the normal faults contribute to under-salt dolomite reservoir of lower Cambrian, and they also are the vertical migration paths of hydrocarbon.