鄂西地区五峰组—龙马溪组岩石相与页岩气富集关系分析——以鄂红地1井为例

鄂西地区页岩气勘探起步较晚,现阶段成果显示该区具有较好的页岩气勘探开发前景,尤其是五峰组—龙马溪组页岩受到诸多关注,但关于该区的岩石相划分和岩石相与页岩气富集关系的研究还未系统开展。目前,涪陵气田和威远—长宁国家示范区的成功商业化显示龙一段为勘探开发潜力最大的层段,通过对鄂西地区地质调查井(鄂红地1井)龙一段岩石相开展定量划分,旨在揭示该区不同时期五峰组—龙马溪组岩石相特征,从而为优质页岩分布预测提供科学依据。采用系统取芯、岩芯观察、笔石生物地层划分、相划分等方法,结合TOC含量、主微量元素、矿物成分、氩离子抛光、含气性测试等系统测试和分析,主要进行了2个方面的研究:(1)从岩性、岩矿、地化、古生物、电性等方面入手,将龙一段划分为浅水陆棚和深水陆棚相,然后利用TOC含量、石英、黏土矿物和笔石4个参数对鄂红地1井龙一段的岩性进行定量分级,将龙一段页岩进一步划分为8类岩石相。其中,富碳富硅富笔石硅质页岩、富碳富硅富笔石放射虫硅质页岩相为最有利岩石相,为页岩气勘探开发的最有利层段。(2)探讨了不同岩石相与微量元素、储集空间和含气量之间的关系。岩石相通过有机质丰度和矿物组分控制了页岩气富集,其...

Analyses of the relationship between lithology and shale gas accumulation for the Wufeng Formation to Longmaxi Formation in the west of Hubei Province:A case study of the Erhongdi 1 well

Shale gas exploration is relatively slow in the west area of Hubei Province.According to current exploration results,the Wufeng Formation and the Longmaxi Formation in this area show a good prospect for shale gas exploration.However,the division of lithofacies and the relationship between lithofacies and shale gas accumulation in this area have not been quantitatively subdivided.The Fulin shale gas field and the Weiyuan-Changning national demonstration zone successfully commercialized in the past indicates that compared with other strata commercially,the first member of Longmaxi Formation is provided with the best potential of exploration and development.In order to reveal the petrophysical characteristics of the Wufeng Formation and the Longmaxi Formation and scientifically forecast the distribution of high quality shale,the lithofacies of the first member of Longmaxi Formation is divided quantitatively based on the research of the Erhongdi 1 well.Through a series of geological analyses(collecting and observing drilling-core,classifying graptolite biostratigraphy and dividing sedimentary facies)and experimental tests(testing TOC,major trace elements,mineral composition and gas content,and scanning electron microscope)of the Erhongdi 1 well,the study was conducted in two aspects:(1)From lithology,mineralogy,geochemistry,paleobiology,electrical characteristic and other aspects,the first member of Longmaxi Formation is recognised as shallow-deep-water shelf facies and deep-water shelf facies,afterwards,the lithology of the first member of Longmaxi Formation in this well is quantitatively classified through the features of TOC,quartz,clay minerals and graptolite.Therefore,the shale of the first member of Longmaxi formation can be further subdivided into eight lithofacies.Siliceous shales with high content of carbon,silica and graptolite fossils and radiolarian siliceous shales containing high content of carbon,silica and graptolite fossils are the most advantageous lithofacies of them.(2)The relationship between different lithofacies and trace elements,reservoir space and gas content is studied.Each lithofacies influent the accumulation of shale gas by TOC and mineral composition.Siliceous shales with high content of carbon,silica and graptolite fossils and radiolarian siliceous shales containing high content of carbon,silica and graptolite fossils have the greatest influence on the gas content of a shale gas field.