泥质岩盖层对扩散相天然气封闭性演化的作用

STUDY ON EVOLUTION OF SEALING GAS IN DIFFUSION PHASE OF MUDSTONE CAPROCK

在研究泥质岩盖层对扩散相天然气封闭机理及作用类型的基础上,对不同类型泥质岩盖层对扩散相天然气封闭性演化阶段的作用进行了研究,认为:具生烃能力但不具异常孔隙流体压力的泥质岩盖层对扩散相天然气封闭性演化不存在阶段性;而既具生烃能力又具异常孔隙流体压力的泥质岩盖层对扩散相天然气封闭性演化可分为抑制浓度封闭和替代浓度封闭2个阶段。此研究不仅可以预测其对扩散相天然气封闭能力的演化,而且可以研究其封闭扩散相天然气的有效性。然后以松辽盆地北部三肇凹陷登二段和青山口组2套泥质岩盖层为例,通过对扩散相天然气封闭性演化特征与沙河子组气源岩大量排气期之间的匹配关系研究,认识到它们在该区天然气聚集与保存中起到了重要作用。

To study the evolution of sealing gas in diffusion phase of mudstone caprock, based on analyzing sealing mechanisms and types of mudstone caprock to gas in diffusion phase, sealing evolution stages of different mudstone caprocks to gas in diffusion phase was studied, the sealing evolution of mudstone caprock that has hydrocarbon-generating ability and has no abnormal pore fluid pressure was not divided into stages. The sealing evolution of mudstone caprock that has hydrocarbon-generating ability and has abnormal pore fluid pressure was divided into two stages of restraining concentration sealing and replacing concentration sealing. The study of sealing evolution stages of mudstone caprock to gas in diffusion phase can not only forecast the change of sealing ability of mudstone caprock to gas in diffusion phase, but also can study its sealing efficiency to gas in diffusion phase. Taking two mudstone caprocks of K_1d^2 and K_lqn of Sanzhao Sag in the north of the Songliao Basin as examples, it is analyzed their sealing evolution characteristics to gas in diffusion phase and the matching relation between formation period of their sealing ability to gas diffusion phase and the period of a great deal of gas expelled from K_1sh gas source rock. And it is also studied their roles in gas accumulation and preservation in the region.