乌尔逊凹陷南二段油气成藏与分布主控因素

受断陷盆地地质条件复杂性和认识水平的制约，使得人们至今对乌尔逊凹陷南二段油气成藏主控因素的认识尚不清楚，从而妨碍了对该凹陷油气勘探的深入进行。为此，在区域石油地质特征分析的基础上，通过平衡剖面技术、源岩排烃史模拟、自生伊利石K-Ar同位素测年技术、含氮化合物等地化指标的测试分析和油气运聚的三维模拟等方法，对乌尔逊凹陷南二段油气成藏机制进行了研究。结果发现，构造传递带、源盖时空匹配、断裂和油气运聚特征是乌尔逊凹陷南二段油气成藏的主控因素；盖源质量空间匹配、断源匹配、断层封闭性、源岩条件和油气运聚形式的不同则是造成该凹陷南北油气分布差异性的主要原因。

MAIN FACTORS CONTROLLING HYDROCARBON ACCUMULATION AND DISTRIBUTION IN THE SECOND MEMBER OF NANTUN FORMATION, WU'ERXUN DEPRESSION

Main factors which control the hydrocarbon accumulation and distribution in the second member of Nantun Formation in Wu'erxun depression are unclear due to the complex geologic conditions in the faulted basin and the limited knowledge, constraining the deepening of exploration in the study area. Based on the characteristic analysis of regional petroleum geologic conditions, the mechanisms of hydrocarbon reservoiring in the second member of Nantun Formation in Wu'erxun depression are studied by using various techniques, such as balanced cross section, hydrocarbon expulsion history modeling of the source rocks, authigenic illite K-Ar isotopic dating, geochemical analysis and 3D modeling of hydrocarbon migration and accumulation. The results show that structural transitional zone, temporal and spatial combination of source cap rocks, features of faults and hydrocarbon migration and accumulation are the main control factors of hydrocarbon reservoiring in the study area. They also indicate that differences in the spatial combination of the quality of source cap rocks, combination of fault and source rocks, fault sealing ability, source rock conditions and the forms of hydrocarbon migration and accumulation are the main causes of the differential hydrocarbon distributions in the southern and northern parts of Wu'erxun depression.