渤海海域渤南地区浅层油气成藏模式与运聚链

Shallow hydrocarbon accumulation model and migration-accumulation chains in Bonan area,Bohai Sea

运移是浅层油气成藏的关键因素。基于钻井、岩心、地震及分析化验资料,结合勘探实践,对渤海海域渤南地区浅层油气成藏特点及分布规律开展系统研究,建立了新近系规模型油气成藏模式。结果表明:①新近系存在4类规模型浅层成藏模式,即深层远源运聚-断裂垂向输导的凸起区成藏模式、深层早期汇聚-强活动断层晚期调整的缓坡带成藏模式、深层多源强驱动-复合断层强输导的陡坡带成藏模式、“二次中转”强驱动-砂体连片侧向输导的洼陷带成藏模式。②从源到藏具有2种油气运聚链:a.缓坡—凸起区阶梯式“Z”型油气运聚链,即洼陷带油气经深层三角洲砂体横向输导,一部分油气在缓坡带深层汇聚,一部分油气通过断层和砂体进行纵向和横向阶梯式运移,最终在凸起区浅层大规模成藏;b.陡坡—洼陷带为反“C”型气运聚链,即洼陷带油气首先在陡坡带深层汇聚,形成“中转站”式油藏,然后通过断裂活动调整到浅层,形成陡坡带浅层油藏,随着运聚量增加,油气继续沿浅层大面积砂体横向运移到洼陷区高部位规模成藏。通过对渤南地区浅层油气运聚链的总结,建立了浅层顺链找油的勘探思路,为渤南地区以及渤海海域其他探区浅层油气勘探提供了有效指导。

Migration is a key factor controlling shallow hydrocarbon accumulation.Based on drilling,core,seismic,laboratory data,and exploration practices,shallow hydrocarbon accumulation characteristics and distribution laws in the Bonan area,Bohai Sea were investigated,and the hydrocarbon accumulation model of Neogene large-scale reservoirs was established.The results show that:Four large-scale shallow hydrocarbon accumulation models exist in the Neogene strata,including uplift accumulation model with deep far-source migration-accumulation and vertical fault transport,gentle slope accumulation model with deep early-convergence and late adjustment of strongly active faults,steep slope accumulation model with deep multi-source strong drive and strong transport of composite faults,and sag zone accumulation model with strongly drive of“secondary transition”and lateral transport in continuous sand body.Two types of hydrocarbon migration-accumulation chains are found from source to reservoirs:a.“Z”-shaped cascade hydrocarbon migration-accumulation chain in the gentle slope-uplift area,or in other words,for the hydrocarbon generated in the sag zone,some hydrocarbon accumulates in the deep strata of the gentle slope zone through lateral transport in deep delta sand bodies,while other hydrocarbon accumulates in shallow uplift on a large scale through vertical and lateral cascade migration through faults and sand bodies,respectively.b.“Inverted C”-shaped gas migration-accumulation chain forms in the steep slope-sag zone,or in other words,the hydrocarbon from the sag zone accumulates in the deep strata of the steep slope zone firstly and forms“transfer station”-type reservoirs,and then it migrates to shallow strata by fault activity adjustment and forms shallow reservoirs in steep slope zone.As migration and accumulation intensify,hydrocarbon continues to migrate laterally along the large area of shallow sand bodies to the high part of the sag zone to form a large-scale reservoir.By summarizing the shallow hydrocarbon migration-accumulation chain in the Bonan area,the hydrocarbon exploration insights along the shallow chains were established,providing effective guidance for shallow hydrocarbon exploration in the Bonan area and other exploration areas in the Bohai Sea。