南海东部浅水区非烃源岩层系岩性油藏勘探实践与方向

Exploration practice and direction of lithologic reservoirs in non-source rock strata in shallow water areas of the eastern South China Sea

南海东部海域经过30多年的油气勘探,在浅水区非烃源层系取得了岩性油藏的勘探突破。目前已发现的岩性油藏相对集中在惠州凹陷南部珠江组,通过对其岩性油藏的分布特征、类型及主控因素开展详细解剖,划分出上倾尖灭型、背斜-上倾尖灭复合型、断层-上倾尖灭复合型和条带型4类岩性油藏。其有利成藏条件主要受4种因素控制:(1)河流、波浪和潮汐等多水动力交互控制着储层的平面分布特征,不同水动力控制了不同的储层和岩性圈闭类型;(2)海平面的多期升降控制了储-盖组合,在主要成藏期具有6套有利成藏组合;(3)东沙运动控制了岩性圈闭的有效性和运移通道,调整了砂体的尖灭、翘倾状态,有利于岩性圈闭形成和成藏;(4)"烃源-断层-构造脊"的立体耦合影响油气的高效聚集。南海东部浅水区可划分出3类共6个岩性油藏勘探潜力带。

After more than 30 years of oil and gas exploration in the eastern South China Sea,breakthroughs have been made in the lithologic reservoir exploration of non-source strata in shallow water areas.The lithologic reservoirs that have been discovered so far are concentrated in Zhujiang Formation of the southern Huizhou depression.The distribution characteristics,types and main controlling factors of the lithologic reservoirs are analyzed in detail,and the lithologic reservoirs are classified into the updip pinch-out type,the compound type of anticline and updip pinch-out,the compound type of fault and updip pinch-out,and the belt type.For lithologic reservoirs,the favorable accumulation conditions are mainly controlled by four factors.(1)The interaction of multiple hydrodynamic forces such as rivers,waves,and tides controls the planar distribution characteristics of reservoirs,and different hydrodynamic forces control various types of reservoirs and lithologic traps.(2)The multi-stage sea level changes control the reservoir-caprock assemblage,and there were six sets of favorable reservoir-forming assemblages in the main accumulation period.(3)The Dongsha movement controlled the effectiveness of lithologic traps and migration pathways,and adjusted the pinch-out and tilting state of sand bodies,which is conducive to the formation and hydrocarbon accumulation of lithologic traps.(4)The three-dimensional coupling of hydrocarbon source,fault and structure ridge affects the efficient accumulation of oil and gas.The shallow water areas in the eastern South China Sea can be divided into six lithologic exploration potential zones belonging to three types.