白云凹陷原油金刚烷化合物研究

The study of diamondoids in petroleum from the Baiyun Sag

针对白云凹陷油气共存的分布格局,轻质油藏、挥发性油藏及凝析油气藏中原油或凝析油因常规的甾萜类异构化参数等均已接近或达到其平衡值,难以有效判断其成熟度,导致无法准确界定该区挥发性油藏及凝析油为原生热成因抑或油藏受晚期天然气改造而成的次生成因的问题。本次研究采用气相色谱-质谱-质谱(GC-MS-MS)方法对白云凹陷原油及凝析油中金刚烷类化合物进行分析及绝对浓度测定,通过金刚烷参数指标对已发现原油及凝析油成熟度进行了界定,并探讨凝析油成因。研究表明,白云凹陷不同构造原油及凝析油成熟度差异大,白云主洼北部番禺低隆起和白云东洼凝析油金刚烷浓度在5000~10000μg/g之间,为高成熟阶段与天然气伴生的原生性凝析油,根据金刚烷指标参数推算的等效镜质组反射率(R_(c))为1.3%~1.6%;白云东洼原油、白云主洼东部凝析油与挥发性油藏、油藏轻质油以及白云西洼挥发油、轻质油金刚烷浓度多在4000μg/g以下,为生油高峰后期产物,根据金刚烷指标参数推算的R_(c)为1.1%~1.3%,且白云主洼东部、白云西洼凝析油及挥发油可能为成熟阶段的原油遭受天然气改造而成的次生凝析油或挥发油。

Considering the distribution pattern of oil and gas in the Baiyun Sag,sterane and terpane biomarker parameters of the crude oils or condensates in light oil and volatile oil reservoir,and that condensate oil and gas reservoirs approximate or reach their equilibrium values,it is difficult to accurately determine the maturity of crude oils or condensates using conventional indices.This has led to the origin identification failure of the volatile oils and condensates in this area.The absolute concentrations of diamondoids in crude oil and condensate from the Baiyun Sag were analyzed using the GC-MS-MS method.Diamondoid-based parameters were used to determine the maturity of discovered crude oils and condensates and further discuss the origin of condensates.The results indicate that the oil maturity is distinct for crude oils and condensates in different structures of the Baiyun Sag.For the diamondoid concentration in condensate oils from the northern Baiyun Main Depression,the Panyu Low Uplift and the Baiyun East Depression reach 5000–10000μg/g,and the calculated R_(c) falls within 1.3%–1.6%according to the diamondoid maturity indices,indicating that they are likely primary condensates associated with natural gas at highly mature stages.While for the diamondoid concentration in the crude oils of Baiyun East Depression,the condensates and the volatile oils of the eastern Baiyun Main Depression and the volatile oils and the light oils of the Baiyun West Depression are mostly less than 4000μg/g;the calculated R_(c) is in the maturity range of 1.1%–1.3%according to the diamondoid maturity indices.This suggests that these oils are mainly generated in the later oil generation stage.The condensates and volatile oils in the eastern Baiyun Main Depression and Baiyun West Depression may be the secondary alteration products of crude oils suffered from the invasion of highly mature natural gases.