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泥质岩盖层并非沉积开始就具有封闭油气能力的,而是随其埋深增加,压实成岩程度增强、粘土矿物转化脱水及有机质向烃类演化到一定阶段才开始具封闭油气能力的。本文在对盖层各种封闭能力进行地史恢复的基础上,确定出三肇凹陷青山口组泥岩盖层的毛细管、压力和烃浓度封闭能力开始形成时期分别为青山口组沉积末期、青山口组沉积末期和嫩江组四段沉积末期,都远远晚于上侏罗统气源岩的排气期(侏罗系沉积末期),因此,造成上侏罗统天然气的大量散失,这可能是该区只找到了一些中小型气田,而找不到大气田的重要原因。
The caprock of mudstone is not oil and gas captive at the beginning of sedimentation, but begins to have closed oil and gas capability with the increase of burial depth, compaction and diagenesis, the dehydration of clay minerals and the evolution of organic matter to hydrocarbons. Based on the historical restoration of various sealing abilities of the cap rocks, the authors determined that the capillaries, pressures and hydrocarbon concentrations of the Qingshakou Formation in the Sanzhao sag have started to form during the depositional period of the Qingshankou Formation, The last sedimentation of the group and the deposition of the fourth member of the Nenjiang Formation are much later than the discharge period of the Upper Jurassic gas source rocks (the end of the Jurassic sedimentation), resulting in a large loss of Upper Jurassic natural gas, which may be The area only found some small and medium-sized gas fields, and can not find a major reason for the gas field.