排油气门限的基本概念、研究意义与应用

排油气门限是源岩在埋深演化过程中，生油气量饱和了自身吸附、水溶、油溶和毛细管封堵等多种形式的存留需要并开始以游离相大量排出的临界地质条件。研究表明，源岩的排油气门限主要随源岩的有机母质丰度（Ｃ／％）、干酪根类型指数（ＫＴＩ）和转化程度（Ｒｏ／％）三者的不同而改变。应用排烃临界地质条件可以建立源岩概念和差别标准；计算源岩排油气量并确定源岩等级评价标准；研究源岩排油、气相态并分析油气运聚成藏机理；划分源岩排油气阶段并建立源岩排油气地质模式。实际应用表明，用排油气门限、排油气量、排油气阶段、排油气地质模式和排油、气窗等替代生烃研究中的相应概念和术语指导油气田勘探更合理，效果更好。

BASIC CONCEPT OF HYDROCARBON EXPULSION THRESHOD AND ITS RESEARCH SIGNIFICANCE AND APPLICATION

Hydrocarbon expulsion threshod (HET) is the critical conditions for hydrocarbon expulsion from source rock when its generated hydrocarbon amount has satisfied all its needs for hydrocarbons due to the absorbtion of minerals, solution of water and oil, capillary of porosity. Research results show that the HET varies mainly with three geological parameters: the total organic carbon content ( C /%), the kerogen type index ( KTI ) and the maturation degree ( R o/%). In this paper, the concept of HET and its critical conditions are applied to establishing the scientific concept and identification criterion for the source rock, modeling hydrocarbon expulsion amount and grading source rocks; studying phases of hydrocarbons in migration and mechanisms of hydrocarbon accumulation, dividing hydrocarbon expulsion stages and establishing geological models of hydrocarbon expulsion. Application results show that it is more reasonable and efficiency to guide the oil and gas prospecting by using hydrocarbon expulsion threshods,hydrocarbon expulsion models,hydrocarbon expulsion windows and so on instead of the relative concepts and terminologies about hydocarbon generation.