斜坡外带输导体系与优势运移路径标定——以渤东凹陷东斜坡为例

Migration system and preferential migration pathway of outer slope zone:an example in eastern slope zone of Bodong Sag

渤海湾盆地海域的斜坡带勘探主要集中于渤海东部和南部反向断阶斜坡带,东部顺向断阶斜坡研究程度较低,油气成藏机理及富集规律不明确。利用油气运移物理模拟实验、地球化学参数示踪等技术,分析油气横向运移路径,建立顺向断阶和反向断阶斜坡带油气成藏模式。结果表明:研究区馆陶组下段砂体、东上段砂体、潜山不整合面是渤东凹陷围区斜坡带主要的输导层系,顺向断阶比反向断阶输导层保存能力弱,顺向断阶型斜坡外带输导层及之上的浅层是潜在含油层系;当输导层上倾方向断层断面正应力小于45 MPa或断层晚期活动速率大于24 m/Ma时,油气经垂向调整后富集于输导层系之上的浅层。渤东凹陷东部顺向斜坡外带A构造勘探目的层由东营组上移至新近系并钻遇较好油气。该结果对斜坡外带油气勘探具有借鉴意义。

Exploration practices in slope zone were mostly conducted in the backward faulted terrace in eastern and southern parts of Bohai Sea,forward faulted terrace is not well explored or understood,and hydrocarbon accumulation and enrichment pattern is not clear yet.Using hydrocarbon migration physical simulation and geochemical index for migration trace methods,accumulation models were established for backward and forward faulted terrace in outer slope of Bodong Sag.Results showed that sandbody in Guantao Formation,unconformity of buried hill were three main lateral transporting passways,whose preservation ability of transporting sand controlled regional hydrocarbon accumulation in slope zone,forward faulted terrace had poorer preservation capacity so that transporting sand and its above strata in the outer slope zone were the potential reservoir targets.Hydrocarbon can migrate vertically to shallow strata while fault later activity rate is bigger than 25 m/Ma or normal stress on fault plane is smaller than 45 MPa.Targeted layer in A structural area located in the eastern outer slope of Bodong Sag was transferred from Dongying Formation to Neogene sequences,and had good coincidence with drilling results,showing good application prospects in guiding the discovery of the outer slope zone.