济阳坳陷古近系页岩油富集条件与勘探战略方向

Enrichment conditions and strategic exploration direction of Paleogene shale oil in Jiyang depression

济阳坳陷页岩油勘探实践的重大突破展示出陆相断陷盆地页岩油的广阔前景,使得页岩油地质理论体系逐步完善。济阳坳陷主力富有机质页岩为新生代古近纪陆相咸化湖盆沉积,总体上具有热演化程度低、埋藏深、地层厚、碳酸盐矿物含量高、地层压力高、地层温度高以及岩相多样、构造复杂、流体性质多样的特征。济阳坳陷古近纪多期次断陷活动与咸化沉积水体形成了页岩规模发育与演化的沉积背景。济阳坳陷主力烃源岩多发育于咸化湖盆,具有早生早富、中等演化程度即可大量生烃的特色,富有机质纹层状岩相无机孔缝并存、大孔发育的储集条件,加之中—低成熟的富有机质富碳酸盐页岩层系游离烃多状态赋存是济阳坳陷古近系页岩油富集的重要基础;富有机质页岩体系中生烃层、储集层的"双层结构"与成烃、成储的"二元耦合"使页岩中大孔径、高孔渗的优势岩相与游离油富集区组成无机-有机的有效匹配。结合页岩油资源量评价实验方法的优化,加之巨厚层页岩油勘探实践的不断突破,济阳坳陷古近系新一轮的页岩油资源评价将会重新认识济阳坳陷页岩油资源规模,预计济阳坳陷页岩油资源总量将在目前41×108t游离油量认识基础上得到显著提高。济阳坳陷页岩油勘探实践将坚持:持续探索不同岩相类型、不同热演化程度、不同压力体系页岩油的富集理论与商业产能,进一步拓展济阳坳陷页岩油资源规模,引领陆相断陷盆地页岩油的勘探。

In recent years,the major breakthrough in shale oil exploration in Jiyang depression demonstrates the broad prospect of shale oil in continental rift basins,and on this basis,the theoretical system of shale oil geology is gradually improved.The main organic-rich shale in the Jiyang depression is the Cenozoic Paleogene continental saline lacustrine basin deposition;generally,it has the characteristics of low thermal evolution degree,deep burial depth,thick formation,high carbonate mineral content,high formation pressure,high formation temperature,diverse lithofacies,complex structure and varied fluid properties.The multi-stage rifting activities and water salinization in Jiyang depression had created a sedimentary background for the large-scale development and evolution of Paleogene shale.The main hydrocarbon source rocks in Jiyang depression,mostly developed in saline lacustrine basin,has the characteristics of early oil generation,early enrichment,and moderate evolution,i.e.,able to generate a large volume of hydrocarbons.The reservoir conditions such as the coexistence of organic-rich laminated lithofacies and inorganic pores/slits and the development of macropores,and the multi-state occurrence of free hydrocarbons in medium-low mature organic-rich and carbonate-rich shale provide the important basis for the enrichment of Paleogene shale oil in Jiyang depression.The double-layer structure of hydrocarbon generation layers and reservoirs in the organic-rich shale system and the binary coupling of hydrocarbon generation and storage make the inorganic-organic effective match between the dominant lithofacies with large pore size and high porosity and permeability in shale and the free oil enrichment area.Further,combined with the optimization of the experimental method of shale oil resource evaluation and the continuous breakthrough in the exploration of ultra-thick shale oil,the new round evaluation of shale oil resource in the Paleogene of Jiyang depression will help us re-understand the scale of shale oil resources in the study area.It is expected that the total amount of Jiyang depression shale oil resources will be significantly improved from the current 4.1 billion tons of free oil.In the future exploration of shale oil in Jiyang depression,we will continue to explore the enrichment theory and commercial production capacity of shale oil with different lithofacies,different thermal evolution degrees and different pressure systems,further expand the scale of shale oil resources in Jiyang depression,and lead the exploration of shale oil in continental rift basins.