高—过成熟气源岩评价的若干问题

对于一次连续生烃的烃源岩．无论是碳酸盐岩还是泥岩，气源岩还是油源岩，其有机碳含量的下限值均为0．5％，但该下限值不适用于多旋回残留盆地烃源岩的二次生烃评价。根据热模拟生烃实验，建立了不同成熟阶段烃源岩二次生烃有机碳丰度下限值的计算方法。应用天然气生聚散动态平衡原理探索识别气源岩的方法，在气源岩R0值大于2．5％的地区，古油藏中的沥青和原油裂解成为气源，古油藏分布决定晚期次生气藏分布。一般情况下，水溶气藏和天然气藏的形成和破坏是同步的，水溶气要成为晚期次生气藏的有效气源，其前期的保存条件很重要。表7参18

Some issues about evaluation on high-over matured gas source rocks

The lower total organic carbon (TOC) limit for primary successive hydrocarbon generating source rocks, carbonate rocks or mudstones, gas source rocks or oil source rocks, is 0.5%. However,the value is not suitable for the secondary hydrocarbon generation in poly-cycle residual basins. The calculating method of the lower TOC for secondary hydrocarbon generation source rocks of different maturity is established according to the thermal simulation experiments.The method for identifying gas source rocks is studied using the natural gas generation-accumulatiom-dissipation dynamic balance theory. In the gas source rocks with R_ o values over 2.5%, the asphaltines and oils have become gas sources due to cracking. The distribution of secondary gas reservoirs is determined by the distribution of paleo-reservoirs. The formation and destruction of water-dissolved gas reservoirs happened at the same time as that of gas reservoirs. The early preservation of water-dissolved gas is very important for its accumulation.