江苏地区句容凹陷油气充注史研究

STUDY OF CHARGE HISTORY IN THE JURONG SAG,JIANGSU REGION

江苏地区句容凹陷是中国南方海相中、古生界勘探较早的地区,油气显示丰富。根据有机包裹体的荧光颜色将容2井储层方解石脉中的有机包裹体分为不同的期次;用离线压碎的方法对容2和容3井储层方解石脉中有机包裹体的烃类组成进行了分析,并与储层中的轻质油进行了对比;结合句容地区的埋藏史对该区油气来源及充注史进行了探讨。结果表明:容2井和容3井油藏存在多期油气的充注;包裹体油代表了早期充注的油气,而不同的正构烷烃分布特征证明容2井早期充注的烃类经历了生物降解过程;早期充注的烃类主要来源于二叠系源岩,而现今三叠系储层中的轻质油为后期充注的,其主要来源于晚白垩世末二叠系及部分三叠系烃源岩的急剧沉降而生成的大量油气。

Regarding exploration of marine Palaeozoic and Mesozoic strata in South of China,the Jurong Sag in the Jiangsu region belongs to the area where was explored in the early stage.Oil and gas show were discovered in many levels in the Jurong Sag.Organic inclusions hosted in calcite vein in reservoir rock from Well Rong2 in the Jurong Sag were divided into different groups according to fluorescence co-lor.Off-line crushing was used to analyze the hydrocarbon released by organic inclusions hosted in calcite vein from reservoir rock in Well Rong2 and Rong3.Through comparing organic inclusion oils with light oil in reservoir,source of hydrocarbon and charge history in the Jurong Sag were discussed combining burial history in Jurong Sag.The results show that multiple charging episodes took place in Well Rong2 and Rong3;Fluid inclusion oils represent the earlier charge while different n-alkanes distribution in different groups fluid inclusions in Well Rong2 shows that hydrocarbons charged in the earlier stage underwent biodegradation;Hydrocarbons charged in the earlier charging episode were derived from Permian source rock,however present light oils in Triassic reservoir rock charged in the later charging episode were derived from Permian and part Triassic source rocks due to its quick subsiding during the Late Cretaceous.