Hydrocarbn explusion threshold (HET) is the critical condition for hydrocarbon expulsion in separate phase from a source rock when the generated hydrocarbon amount has satisfied all needs for ahsorpBon by minerals, solution in water, and blocking of capillary pressure. Research results show that the HET varies mainly with three geological parameters: total organic carbon content (C%), kerogen type index (KTI) and thermal maturation degree (R0). Source rocks with low C% and KTI cross the HET at a high level of maturation degree (larger R0); source rocks with lower R0 and C% can also cross the HET if the kerogen has a larger KTI. Under general geological conditions, a source rock first crosses the methane expulsion threshold (HETgl), then the heavw hydrocarbon gas threshold (HETgn), and finally the liquid hydrocarbon expulsion threshold (HET0). In this paper the concept of HET, and its critical conditions, are applied to establish the scientific validity of the concept and grade the source rocks, to study the phases of hydrocarbons in migration and the mechanisms of hydrocarbon acvumulation, and to divide the hydrocarbon expulsion into stages. Applications to different basins in China show that HET provides an accurate and efficient method to guide oil and gas prospecting.

油气在生排运聚成藏过程中须经历生烃排烃、运烃、聚烃和资源等5个门限。某一确定的油气运聚成藏系统进入任一个门限都将损耗一部分烃量。在实际地质条件下，源岩生成的烃量只有超过进入各个门限时损耗烃量之和才能大规模聚集成藏，并构成油气勘探的远景区。根据物质平衡原理研究油气生成量和损耗量之间的平衡关系，建立了相应的地质模型。在此基础上，提出了门限控烃作用及其计算模型。文中阐明了各门限的地质含义、判别标准及其控油气作用机理，给出了应用实例。

根据油气运聚的动力和作用方式将油气藏成因分为3类8种17式。这8种分别是：①高压势场作用下形成的油气藏；②低压势场作用下形成的油气藏；③由水携带溶解气游离释放形成的天然气藏；④浮力作用下形成的油气藏；⑤毛细管力作用下形成的油气藏；⑥天然气体积膨胀形成的深盆气藏；⑦分子吸附作用形成的煤层瓦斯气藏；⑧分子水合作用形成的水合甲烷气藏。①～③种为突发式流压作用形成的油气藏，④～⑥种为缓慢式烃势差形成的油气藏，⑦和⑧为非常规条件下天然气汇聚形成的特殊类型的（油）气藏。相同动力学成因的油气藏因实际地质条件的差异可以进一步分成亚类。不同动力学成因的油气藏的分布规律、主控因素和产状特征不同。研究油气运聚的动力机制和成因模式对指导油气田勘探提高勘探效益具有重要意义。