Bongor盆地Baobab地区潜山油气成藏期次

Baobab潜山油藏是乍得Bongor盆地北部斜坡的主力油藏。以Baobab C-2井潜山油藏为例，从烃源岩生排烃史、构造热演化史、流体包裹体中含油包裹体颗粒指数特征、显微荧光与测温技术等方面分析其油气成藏史。埋藏史的分析结果表明，Baobab地区Mimosa组+Prosopis组主力烃源岩在约90 Ma开始生烃，并于约80 Ma开始排烃，晚白垩世末约66 Ma达到生排烃高峰期，之后由于构造抬升作用，生烃作用停止。Baobab C-2井潜山油藏经历了晚白垩世80~55 Ma的原生油气充注阶段和古近纪约30 Ma的次生油气成藏事件。在晚白垩世期间石油的充注表现为充注强度程度不同的连续过程，开始于晚白垩世80 Ma的石油充注事件以较低成熟度原油为主，而发生于约70 Ma的第二期石油充注事件则以成熟油气为主，该期充注事件是形成现今油气分布格局的主要贡献者。古近纪发生的次生成藏事件代表因构造作用而引起油气调整。

Buried-hill hydrocarbon accumulation stage of Baobab area in Bongor Basin

Baobab buried-hill reservoir is the major oil reservoir in the north slope of Bongor Basin. Taking Baobab C-2 buried-hill reservoir as an example, its hydrocarbon accumulation history is analyzed and studied in terms of the hydrocarbon generation and expulsion history of source rocks, tectonic thermal evolution history, the GOI characteristics of fluid inclusion, micro-photoluminescence, thermometric techniques and etc. Through studying burial history, it is found that the major source rocks in Mimosa Formation and Prosopis Formation of Baobab area began to generate hydrocarbon at about 90 Ma, and started to expel hydrocarbon at about 80 Ma. At about 66 Ma in the Late Cretaceous, hydrocarbon generation and expulsion reached the peak; afterwards, hydrocarbon generation ceased due to tectonic uplift. Baobab C-2 buried-hill reservoir experienced the primary oil-gas charging stage at about 80-55 Ma in the Late Cretaceous and the secondary hydrocarbon accumulation event at about 30 Ma in Paleocene. In the late Cretaceous period, the oil charging was a continuous process with different degrees of charging intensity. The oil charging event beginning at 80 Ma was dominated by low-maturity crude oil; the second stage of oil charging event happening at 70 Ma was dominated by mature oil and gas, and made a major contribution to the formation of current oil-gas distribution pattern. The occurrence of secondary accumulation event in Paleocene represents the oil-gas adjustment event resulted from tectonism.