长岭断陷龙凤山次凹下白垩统油气成藏期

针对龙凤山次凹下白垩统含油气层系,采用烃源岩生烃史、储层流体包裹体等综合方法,系统研究了油气成藏期次。结果表明沙河子组烃源岩在泉头组沉积中期至嫩江组沉积初期达到高成熟阶段,为主生烃期。烃类包裹体可划分为两期,Ⅰ期烃类包裹体形状不规则,孤立分布,显示黄色—黄绿色荧光,对应均一温度为90～100℃,盐度质量分数为1%～2%,与早期油气充注相对应;Ⅱ期烃类包裹体多为较规则的椭圆形,呈串珠状或群体分布,显示黄绿色—蓝绿色荧光,对应均一温度为125～135℃,盐度质量分数为4%～6%,与晚期油气充注相对应。综合烃源岩生烃史、埋藏史及包裹体均一化温度分析认为,第1油气成藏期为登娄库组中期至末期,第2油气成藏期为泉头组末期至嫩江组初期。

ACCUMULATION STAGES OF LOWER CRETACEOUS HYDROCARBON IN LONGFENGSHAN SUBSAG OF CHANGLING FAULT DEPRESSION

In the light of Lower Cretaceous hydrocarbon series of the strata in Longfengshan Subsag,by means of the comprehensive method between the major hydrocarbon source rocks and reservoir fluid inclusions and so on,the period and time of the hydrocarbon accumulation were researched.The achievements show that Shahezi Formation source rocks reached the high-maturity stage and became the key generating period of the petroleum from Middle Quantou Formation to Early Nenjiang Formation depositional periods.The hydrocarbon inclusions can be divided into two periods:Period Ⅰ inclusions are characterized by irregular shapes and separated distribution with yellowyellow green fluorescences,the corresponding homogenized temperature is 90-100 ℃,the mass fraction of the salinity is 1％-2 ％,corresponding with the early stage of the hydrocarbon enrichment;Period Ⅱ inclusions are featured by pretty regular oval shapes and beaded or cluster distributions,showing yellow green-blue green fluorescences,the corresponding homogenized temperature is 125-135 ℃,the mass fraction of the salinity is 4％-6％,corresponding with the late stage of the hydrocarbon enrichment.The combined analysis among the hydrocarbon generating history of the source rocks,burial history and the homogenized temperature of the inclusions shows that the first period of the hydrocarbon accumulation was from Middle Denglouku to Late Denglouku Formation,and the second is from Late Quantou to Early Nenjiang Formation.