歧口凹陷断裂密集带形成演化特征及油气富集差异研究

断裂密集带作为斜向伸展作用的标志性产物,是断块油气藏形成与聚集的主要场所。针对歧口凹陷不同走向断裂密集带油气富集差异较大的问题,通过统计密集带几何学特征及构造组合样式,结合断裂带形成演化规律,分析不同走向断裂带油气富集差异。结果表明:歧口凹陷主要发育NEE、EW向及NNE向3种断裂带。其中,NNE向断裂带形成时期最早,断裂的垂向输导能力最弱,油气在深部富集;NEE向断裂带随后形成,断裂对盖层的破坏作用最强,油气在深、浅层均有分布;EW向断裂带形成时期最晚,断裂的垂向输导能力介于前两者之间。研究成果可为歧口凹陷及相似的多期裂陷盆地断裂密集带的油气勘探工作提供理论支撑。

Study on the Formation and Evolution Characteristics and Hydrocarbon Enrichment Difference of Fault Concentrated Zones in Qikou Sag

As a landmark product of oblique extension, a fault concentrated zone is the main place for the formation and accumulation of fault block reservoirs. The hydrocarbon enrichment difference in fault concentrated zones with different strike directions in the Qikou Sag was analyzed by statistical analysis of geometric characteristics and structural combination styles of fault concentrated zones in this sag, combined with the formation and evolution law of fault zones. The results show that there are mainly three kinds of fault zones in the Qikou sag: NEE-trending, EW-trending and NNE-trending. Hereinto, the NNE-trending fault zones were formed at the earliest time, the vertical transport ability of the faults are the weakest, and hydrocarbons are enriched in the deep layers; the NEE-trending fault zones were formed later, and the faults have the strongest destructive effect on cap rocks, and hydrocarbons are distributed in both deep and shallow layers; the EW-trending fault zones were formed at the latest, and the vertical transport ability of the faults is between the former and the latter. The research results can provide theoretical support for oil and gas exploration in the Qikou Sag and similar multi-stage rift basins with concentrated fault zones.