渤中坳陷油气成藏规律

摘要

渤海坳陷下第三系砂岩普遍含有两类油气包裹体，即原生油气包裹体和次生油气包裹体，它们分别记录了本区两次油气运移、聚集成藏过程。次生油气包裹体个体大、分布广、含量明显高于原生油气包裹体，其主要充填分布在次生溶蚀孔隙和裂隙中。均一温度测量、包裹体成分和生物标志化合物分析结果综合表明，次生油气包裹体记录的第二次油气运移是区内最主要的一次油气聚集成藏过程，其油气来源于下第三系湖相泥质烃源岩。本区次生溶蚀孔隙是在早第三纪晚期构造抬升过程中，由大气淡水淋滤作用形成的。结合地质演化特征分析认为，渤中坳陷目前油气勘探的重点应是浅部下第三系地层，而不是深部其他地层。早第三纪晚期构造运动、沉积%Two types of oil-gas inclusions, the primary and the secondary, were recognized in the Tertiary clastic rocks in Bozhong Depression of the Bohaiwan Basin in Northeastern coastal area of China. These oil-gas inclusions recorded two stages of oil migration and accumulation in the region. It is found that the secondarysolution pores and fractures, filled with abundant secondary oil-gas inclusions,are dissolution pores formed by the eluviation due to the uplift of the region at the end of the early Tertiary. Data from temperature measurements and analysis to compositions together with biomarks of the oil-gas inclusions indicate that the oil trapped in secondary porosity and fractures originated from the lower Tertiary lacustrine source rocks and the oil accumulations were controlled by the Tertiary tectonics and diagenesis. It is proposed that targets for oil exploration in the region should focus on the Tertiary sediments rather than the Pre-Teriary depositions. Tectonics, sedimentary discontinuity between lower and upper Tertiary and reservoir prediction are the key subjects for oil prospecting in the region.