南盘江盆地板街古油藏流体包裹体特征及其成藏成矿关系研究

Fluid Inclusion Characteristics of Banjie Paleo-oil Reservoir in Nanpanjiang Basin and Its Relationship to Accumulation and Mineralization

在南盘江盆地发现了过演化程度(高成熟—过成熟)的烃类包裹体,其主要赋存于与板街古油藏储层沥青共生的方解石脉中。通过镜下鉴定、激光拉曼测试、显微测温等手段,对烃类包裹体和与其同期的盐水包裹体进行岩相学和地球化学研究。结果表明,储层中包裹体分为盐水包裹体和有机包裹体两大类,有机包裹体又进一步划分为气液两相包裹体、气相包裹体和固相沥青包裹体,气相组分主要为甲烷和乙烷,固相组分主要为碳质沥青。盐水包裹体的均一温度为119~150℃,代表了包裹体的捕获温度;而有机包裹体的均一温度有127~161℃和165~184.3℃两个区间,则代表了原先捕获的烃类包裹体在未被破坏的情况下经历热演化的温度区间。该古油藏中包裹体为泥盆系烃源岩在热裂解生湿气和生干气时期原油裂解生成的气烃进入二叠系储层,被早期生成的方解石捕获。保存在包裹体内的烃类经历了热演化,最终形成干气和沥青包裹体,这些包裹体记录了板街古油藏自油气藏演化至干气藏的油气活动事件。下一步应在储层或矿床不同层位进行采样,并进行地球化学分析,对成藏成矿关系进一步研究。

Hydrocarbon inclusions with over-evolution degree(high maturity to over-maturity)were found in Nanpanjiang Basin,which mainly existed in calcite veins associated with the bitumen of Banjie paleo-oil reservoir.The petrographic and geochemical studies of hydrocarbon inclusions and contemporaneous saline in-clusions have been carried out by means of microscopic identification,laser Raman test and microthermometry.The results show that the inclusions in Banjie paleo-oil reservoir are divided into brine inclusions and organ-ic inclusions,and the organic inclusions are further divided into gas-liquid two-phase inclusions,gas inclusions and solid bitumen inclusions.The gas component mainly consists of methane and ethane,and the solid component is mainly carbonaceous asphalt.The homogenization temperatures of brine inclusions are 119-150℃,which represents the capture temperature of the inclusions;while the homogenization temperatures of organic inclusions are 127-161℃and 165-184.3℃,which represent the temperature range of undergoing thermal evolution without being destroyed of the originally captured hydrocarbon inclusions.During wet gas generation and dry gas generation of Devonian source rocks through thermal pyrolysis,the gas hydrocarbon generated by crude oil pyrolysis entered the Permian reservoirs and were captured by early calcite,and then the inclusions in this reservoir are formed.The hydrocarbon preserved in the inclusions experienced thermal evolution,and eventually evolved into dry gas and asphalt inclusions,which recorded the oil and gas activity events of Banjie paleo-oil reservoir evolved from oil and gas reservoir to dry gas reservoir.Sampling should be done at various horizons in the reservoirs and mineral deposits,and geochemical analysis should be done next for further research on relationship to accumulation and mineralization.