松辽盆地北部青山口组一段有效烃源岩评价-图版的建立及意义

有效烃源岩是指已经生烃且排烃的沉积岩，排烃的临界值是指烃源岩的生烃量刚好达到烃源岩的最大残留烃量。根据质量守恒原理建立了松辽盆地北部青山口组一段（简称青一段）有效烃源岩的识别图版，有效烃源岩识别图版综合考虑了烃源岩有机质丰度、类型和成熟度的影响，从而避免了传统烃源岩评价中将上述3种参数分别评价的不足，可以快速直观地评价烃源岩的有效性及排烃潜力。高有机碳含量的烃源岩易于排烃，且所需的热演化程度相对较低，而当有机碳含量低于0.4%时，烃源岩不能排烃，为烃源岩的有机碳含量下限。利用该图版对松辽盆地中央坳陷区不同凹陷的青一段烃源岩进行的评价结果表明，齐家-古龙凹陷、长垣南、三肇凹陷、王府凹陷源岩均可大量排烃，而黑鱼泡凹陷烃源岩位于排烃临界线之下或附近，排烃潜力有限。这与目前勘探结果相吻合，表明该图版的有效性，可用于优选勘探区带，降低勘探风险。

An evaluation diagram of effective source rocks in the first member of Qingshankou Formation in northern Songliao Basin and its implication

An effective source rock is defined as sedimentary rocks that have generated and expulsed petroleum.An expulsion critical value is reached when the petroleum generation mass equals the remained mass in a source rock.An identification diagram for effective source rocks in the first member of the Qingshankou Formation(K2qn1) in the northern Songliao Basin was established based on the mass conservation principle.This diagram integrates an organic carbon content,organic type and maturity of source rocks,while these parameters in the conventional source rock assessment are considered somewhat separately.Thus,the diagram can be used to quickly and directly assess the effectiveness and expulsion potential of a source rock.The diagram shows that a source rock with high content of organic matter is more ready to expulse petroleum than that with low content of organic matter,moreover,the former requires a comparatively low maturity to generate petroleum.When TOC is lower than 0.4%(i.e.the lower limit of TOC needed for a source rock),petroleum expulsion cannot occur in source rocks.The diagram was then applied to the assessment of the K2qn1 source rock in the central depression of Songliao Basin,which indicates that the Qijia-Gulong Depression,the south of the Changyuan,and the Sanzhao and Wangfu Depressions all have experienced mass expulsion of petroleum,while the Heiyupao Depression has a limited potential of petroleum expulsion.The accuracy and effectiveness of the diagram were verified by the intensity of petroleum occurrence in these areas,indicating that the diagram can be used to optimize exploration targets and decrease the risk of exploration.