研究沉积盆地油气总量及分布规律,有必要首先了解烃源岩的分布。受取心样品数量的限制,一般不可能获得整段连续烃源岩有机碳的实验室测定值,常采用间隔一定距离的有机碳含量测定值的几何平均值,无法反映生油岩的全貌。为获取单井连续有机碳含量,准确确定烃源岩厚度,有必要开展测井烃源岩评价研究。渤海沙河街组地层具有高伽马、高孔隙度、高电阻率等典型烃源岩测井响应特征,可通过测井曲线特征定性识别烃源岩。建立测井信息与烃源岩有机碳含量间的定量关系模型,计算出烃源岩有机碳含量的连续分布。对不同有机碳含量计算方法结果对比表明,用Passey模型计算的有机碳含量与岩心有机地化分析有机碳含量趋势一致、相对误差小,证实该方法基本满足渤海地区烃源岩评价需求。通过对渤海湾研究区20口井测井处理结果的对比,该区沙河街组湖相地层有机碳含量最高,有利烃源岩厚度大,其中沙三中段是最有利烃源岩分布层位。

To study total reservation and distribution of oil and gas in the sedimentary basin, the distribution of source rock should be investigated first. Based on the limited number of core samples, it is impossible to obtain the continuous laboratory measurements of organic carbon of source rock. The full information of organic carbon can not be revealed by laboratory measurements, because it is the geometric mean value of several discrete core samples. Well logging evaluation of source rock is carried out in order to get the information about continuous organic carbon content and thickness of source rock. In Shahejie Formation, source rock is identified by typical well logging characteristics of high gamma, high porosity, and high resistivity. The continuous organic carbon content of source rock is calculated by using a quantitative relationship model, which is established based on multivariate statistical analysis between well logging information and the core carbon content. Comparing with different methods for organic carbon content calculations, the Passey formula method is found to fit well with the core geochemistry method, and with a small relative error. The Passey formula method is basically confirmed that it satisfies the demand for hydrocarbon source rock evaluation in Bohai Bay oilfield. The processing results of 20 wells indicate that there is higher organic carbon content and thicker source rock in Shahejie lacustrine Formation. Especially, the middle of the third zone of Shahejie Formation is the most beneficial layer of source rock.