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对鄂尔多斯盆地下古生界气源的争议已有30多年,主要观点包括以上古生界煤成气为主和以下古生界海相油型气为主。近年来学者们通过分区域、分层位研究,认为盆地不同地区由于源储配置情况有异,盆地不同地区下古生界气中上、下古生界来源气混源比例不同,应分别讨论。细化的研究使下古生界气源问题的争议得到了一定程度的调和,但同时混源比例计算等也使得2个前提问题变得尤为重要:1下古生界是否存在自生自储气;2下古生界自生自储气地球化学特征如何。结合测井数据对近年来最新勘探井的下古生界烃源岩进行了评价,证实了下古生界有效烃源岩的存在。通过对奥陶系马家沟组盐下(奥陶系马五6巨厚膏盐岩以下)天然气地球化学特征与盐上(上古生界及奥陶系风化壳)天然气组分、碳同位素对比,指出下古生界海相烃源岩原生气具有δ~(13)C_1<-35‰、δ~(13)C_2<-28‰的特征。
The controversy over the gas source in the Lower Paleozoic in the Ordos Basin has been over 30 years. The main views include the Paleozoic coal-formed gas and the following Paleozoic marine oil-gas. In recent years, through the study of subregional and stratified positions, scholars believe that due to the different source-reservoir distribution in different areas of the basin, the proportions of source-gas mixtures in the upper and lower Paleozoic in the Lower Paleozoic in different areas of the basin should be discussed separately . The detailed study has reconciled the controversy of the gas source problem in the Lower Paleozoic to a certain extent, but at the same time, the calculation of the mixed source ratio also makes the two prerequisite questions become more and more important: ; 2 Lower Paleozoic spontaneous self-storage gas geochemical characteristics. The Lower Paleozoic source rocks of the latest exploration wells in recent years were evaluated with log data to confirm the existence of effective source rocks in the Lower Paleozoic. By comparing the geochemical characteristics of natural gas with salt (upper Paleozoic and Ordovician weathering crust) natural gas composition of the Ordovician Majiagou Formation under the salt (Ordovician Ma6 6 thick gypsum salt rock), carbon isotope ratios It is pointed out that the paleo-gas in the Lower Paleozoic marine source rocks has the features of δ 13 C 1 <-35 ‰ and δ 13 C 2 <-28 ‰.