松辽盆地北部源下致密油成藏源岩下限与分类标准

Source rock lower limit and classification standard of tight oil reservoir under source in northern Songliao Basin

松辽盆地北部扶余油层是源下致密油的典型代表。为了能够有效识别和预测致密油有利富集部位,明确勘探方向,对致密油源岩下限和分类标准开展研究。通过对青山口组烃源岩的排烃强度进行定量计算,结合TemisFlow盆地模拟软件进行了过剩压力的恢复。通过模拟烃源岩的排烃强度与现存泥质源岩中的残留有机碳含量和过剩压力的关系,最终确定青山口组泥岩以过剩压力1.0 MPa、排烃强度1.5×10^(6)t/km^(2)、残留有机碳1.0%为致密油有效源岩下限。根据这个下限标准,将青山口组泥岩划分为优质源岩、有效源岩和无效源岩三种类型。进一步明确了致密油的发育同样受到源控作用影响,有效烃源岩及以上类别源岩发育区是致密油的主要富集场所。

Fuyu reservoir in northern Songliao Basin is a typical representative of tight oil under source.In order to effectively identify and predict the favorable enrichment sites of tight oil and clarify the exploration direction,the lower limit and classification standard of tight oil source rocks are studied.Through the quantitative calculation of hydrocarbon expulsion intensity of Qingshankou Formation source rocks,combined with TemisFlow Basin simulation software,the excess pressure is restored.By simulating the relationship between the hydrocarbon expulsion intensity of the source rock and the residual organic carbon content and excess pressure in the existing argillaceous source rock,it is finally determined that the mudstone of Qingshankou Formation has an excess pressure of 1.0 MPa and a hydrocarbon expulsion intensity of 1.5×10^(6) t/km^(2) and 1.0%residual organic carbon are the lower limit of effective source rock for tight oil.According to this lower limit standard,the mudstone of Qingshankou Formation is divided into three types:high-quality source rock,effective source rock and ineffective source rock.It is further clarified that the development of tight oil is also affected by source control,and the development areas of effective source rocks and above source rocks are the main enrichment sites of tight oil.