海拉尔盆地乌尔逊—贝尔凹陷白垩系原油地球化学特征及油源对比

GEOCHEMICAL CHARACTERISTICS OF THE CRETACEOUS OIL AND CORRELATION OF OIL TO SOURCE ROCK IN WUERXUN AND BEIER DEPRESSIONS,THE HAILAER BASIN

对海拉尔盆地乌尔逊凹陷和贝尔凹陷共21个原油和油砂样品进行GC、GC-MS和非烃含氮化合物测试分析，根据饱和烃、轻烃和甾萜类生物标志化合物的分析资料，全面剖析了海拉尔盆地乌尔逊-贝尔凹陷白垩系原油的地球化学特征，并通过油源对比确定了其主力烃源层。研究结果表明，海拉尔盆地贝尔凹陷和乌尔逊凹陷原油存在2种成因类型：第一类油饱和烃C17-C23具正构烷烃优势，呈单峰型分布，Pr／Ph〉1（1～2．88），C27-C29甾烷呈“V”型分布，伽马蜡烷含量较低，表征淡水湖相沉积环境；第二类油具有饱和烃低碳正构烷烃优势，Pr／Ph〈1，孕甾烷、C27重排甾烷含量较低，伽马蜡烷不发育，表征煤系地层原油。油源对比揭示，原油来自2套不同沉积环境的源岩，展示了海拉尔盆地良好的烃源条件。

Based on the GC,GC-MS and nonhydrocarbon nitric chemical compound analytical data of 21 samples of crude oil and hydrocarbon-bearing rocks, the geochemical characteristics of the Cretaceous oil in Wuerxun and Beier depressions in Hailaer Basin were studied, and the main source rock for the oil was determined by oil-source rock correlation. The studied results reveal that there are two kinds of crude oil in Wuerxun and Beier depressions. One kind shows a dominance of n-alkanes in C17- C23 and distribution in unimodality. Its Pr/Ph is higher than 1 （1-2.88）. The＂V＂shaped distribution of C27 - C29 steranes and low gammacerane indicate a fresh water lacustrine source rock. The other one shows a dominance of n-alkanes in light hydrocarbons and low C27 sterane. Its Pr/Ph is less than 1 and it lacks gammacerane. This kind of oil mostly stemmed from the coal measure strata. According to the results of oil-source rock correlation, the crude oils in Wuerxun and Beier depressions stemmed from two kinds of depositional setting. It indicates that there are good conditions of source rock in Hailaer Basin.