珠江口盆地恩平凹陷烃源岩评价及油气成藏特征分析

应用地球化学、盆地模拟和储层流体包裹体技术对恩平凹陷烃源岩及油气成藏特征进行了评价与分析。恩平凹陷主要存在2套成熟烃源岩,文昌组烃源岩成熟时间早,生烃规模大,是主力烃源岩;恩平组烃源岩总体成熟度不高,生烃量有限,是次要烃源岩;EP17洼和EP18洼是潜在的富生烃洼陷。恩平凹陷主要有2期油气充注,第1期充注时间较早(20Ma以前),以油为主,油主要来自深部文昌组中深湖相烃源岩,该期油气大量发现于浅层储层;第2期充注时间较晚(5Ma以后),以天然气为主,天然气主要源自文昌组烃源岩,该期油气主要发现于深层储层。恩平凹陷油气勘探方向应以深层(文昌组)为主,寻找深层早期形成的构造是该区下一步勘探的重要目标。

Source rocks evaluation and reservoir characteristics analysis in Enping sag, Pearl River Mouth basin

Source rocks and reservoir characteristics are evaluated and analyzed by the techniques of geochemistry,basin modeling and fluid inclusion in Enping sag.There are two main sets of mature source rock in the sag,with Wenchang Formation as the leading source rock due to its earlier maturation and sizable hydrocarbon generation,and Enping Formation as the secondary source rock due to its lower maturity and limited hydrocarbon generation.Subsag EP17 and EP18 are potential hydrocarbon kitchens.It is believed that there are two stages of hydrocarbon charge in Enping sag.The earlier first stage(before 20 Ma) is dominated by oil mainly derived from Wenchang deep lacustrine source rock, with its oil charge greatly discovered in shallow reservoirs.The later second stage(after 5 Ma) is dominated by gas mainly deprived from Wenchang source rock,with its gas charge largely discovered in deep reservoirs.The hydrocarbon exploration direction in the sag should focus on deep intervals(Wenchang Formation),and the next important targets should be deep structures formed earlier.