东海西湖凹陷油气“蒸发分馏”成藏机制

根据东海西湖凹陷30个原油样品的各种地球化学分析资料及地质资料,综合分析确定了西湖凹陷油气的地球化学特征、成熟度、油源及成藏机制。认为西湖凹陷原油主要源自各地区煤系烃源岩;具有原油近源成藏、短距离运移的特点和先油后气,两期成藏的特征;各气藏均为“蒸发分馏”作用形成的次生凝析气藏。首次提出蒸发分馏效应是该区油气成藏模式的一个重要特点。图7表2参18

Pooling mechanisms of "evaporating fractionation" of oil and gas in the Xihu depression, East China Sea

According to the geochemical data and geological information of 30 samples taken from the Xihu depression, the geochemical characteristics of oil and gas, maturity, oil source and hydrocarbon pooling mechanisms have been synthetically analyzed and interpreted. The results suggest that the crude oil mainly originated from each district coal measure source rock in the Xihu depression because the oil has a character of short distance migration from the source rock. The oil pools were formed before those of gas, and the pools were formed and trapped in two stages. The secondary condensate gas reservoirs were all formed as a result of the "evaporating fractionation effect", which is determined for the first time in this study and may be an important characteristic of the hydrocarbon pooling in this area.