白云凹陷东部深水区混源油定量解析

Quantitative study on mixed source oil in deep water area of eastern Baiyun sag

白云凹陷东部为珠江口盆地深水油气勘探的热点地区,该区存在多源多洼的供烃格局,原油、凝析油及天然气共存,且油气空间分布极其不均一,为揭示该区油气来源并确定文昌组、恩平组两套主力烃源岩成藏贡献,对该区原油(凝析油)的正构烷烃单体碳同位素特征与气相色谱指纹特征进行精细分析。结果表明,研究区原油(凝析油)为文昌组与恩平组烃源岩共同贡献的混源油,不同构造带原油(凝析油)中文昌组与恩平组烃源岩的贡献率均存在差异,其中凝析油及H34油藏原油主体由恩平组烃源岩贡献,贡献率为66%~78%,文昌组贡献率较低,仅为21%~32%;H16及H29油藏原油由文昌组及恩平组烃源岩贡献,恩平组烃源岩贡献率为53%~58%,文昌组烃源岩的贡献率为42%~47%,两者贡献率相当。

The deep water area of eastern Baiyun sag is a hot spot for deep-water oil and gas exploration in the Pearl River Mouth Basin, where there is a multi-source and multi-depression hydrocarbon supply pattern with the coexistence of crude oil, condensate oil and natural gas, and the uneven spatial distribution of oil and gas. To reveal the source of oil and gas and determine the contribution of Wenchang formation and Enping formation to hydrocarbon accumulation in this area, this paper analyzes the monomer carbon isotopic characteristics of n-alkanes and the chromatographic fingerprint characteristics of crude oil(condensate) in the study area. The results show that the crude oil(condensate) in the study area is the mixed source oil jointly contributed by Wenchang formation and Enping formation source rocks, and the contribution rates of both Wenchang formation and Enping formation source rock to crude oil(condensate) in different tectonic belts are different. Enping formation source rock contributes more to the condensate and H34 crude oil reservoir in this area while Wenchang formation source rock contributes less. The contribution rates are 66%~78% and 21%~32% respectively. Enping formation source rock and Wenchang formation source rock have similar contribution rates to crude oil of H16 and H29 reservoir, being 53%~58% and 42%~47% respectively.