乍得Bongor盆地南部坳陷油气特征与成因

Hydrocarbon characteristics and genesis in the southern depression of Bongor Basin,Chad

乍得Bongor盆地新发现了一系列的天然气,开创了油气并举的新局面。在南部凹陷D区存在明显的油气并存现象,研究D区油气分布特征及成因对Bongor盆地天然气前景具有重大意义,同时有利于深化认识Bongor盆地烃源岩的潜力。以D-1井为例,利用天然气组分、同位素、轻烃等参数以及原油色谱、色质等参数,分析天然气对原油成藏的作用。结果表明:D-1井不同深度原油属于同一母源在相同演化阶段形成的产物,后期主要受气洗和运移分馏作用影响,天然气将深部油藏轻质组分带入浅部油藏,使得浅部油藏轻组分富集,色谱图上表现为双峰特征,前峰主峰低碳化明显,同时天然气也主要赋存于浅部油藏中,形成了油气并存的局面。

The discovery of a series of natural gas in the Bongor Basin,Chad has opened up a new situation of simultaneous oil and gas development.There are obvious phenomena of oil and gas co-existence in D area of the southern depression.The study on the distribution characteristics and genesis of oil and gas in D area is of great significance to the natural gas prospect of Bongor Basin,and is conducive to the further understanding of the source rock potential of Bongor Basin.Taking Well D-1 as an example,the effect of natural gas on the accumulation of crude oil is analyzed by using the parameters such as natural gas composition,isotopes,light hydrocarbons,as well as the parameters such as crude oil chromatography and chromatism.Results show that crude oil at different depths of Well D-1 is the product of the same source in the same evolutionary stage.It was mainly affected by gas washing and migration fractionation in the later period.Natural gas brings the light components from deep reservoirs to shallow reservoirs,which enriches the light components in shallow reservoirs.The chromatogram shows the double peak feature,and the main peak of the front peak has obvious low carbonization.At the same time,natural gas mainly exists in shallow reservoirs,forming the coexistence of oil and gas.