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川东北地区陆相层系天然气的研究工作取得了重要的进展,但四川盆地通南巴构造陆相层系天然气组成特征比较复杂,气源方面的认识一直存在争议,成藏时间尚不明确。在对川东北地区典型气藏地质特征及天然气地球化学特征剖析的基础上,探讨了通南巴构造陆相层系天然气的气源及成藏期次。结果表明,研究区陆相层系天然气以烃类化合物为主,非烃含量低,甲烷含量在95%以上,为海相、陆相气源的混合气,主要来源于陆相地层须家河组及自流井组烃源岩的贡献。通南巴构造陆相层系不同含气层段总体经历了2期成藏事件:(1)须家河组在中侏罗世早期至晚侏罗世中期、早白垩世中期各经历一次成藏事件;(2)自流井组在中侏罗世早期至晚侏罗世早期、早白垩世各经历一次成藏事件。
Significant advances have been made in the research of terrestrial gas in northeastern Sichuan. However, the composition of natural gas in the continental facies of Tongnanba in the Sichuan Basin is quite complicated. There is still controversy about the gas source, and the timing of hydrocarbon accumulation is not yet clear. Based on the analysis of the geologic characteristics and natural gas geochemical characteristics of the typical gas reservoirs in northeastern Sichuan, the gas source and hydrocarbon accumulation stages of natural gas in Tongnanba tectonic terrains were discussed. The results show that the hydrocarbon in the terrestrial stratigraphic system in the study area is mainly hydrocarbon, with low non-hydrocarbon content and methane content above 95%, which is a mixture of marine and continental gas sources, mainly derived from continental strata Xujiahe Group and the Ziliujing Formation source rock contribution. The Tongnan Paleogene continental facies layers in different gas-bearing intervals generally experienced two stages of hydrocarbon accumulation events: (1) the Xujiahe Formation experienced a transition from early Middle Jurassic to mid-late Jurassic and mid-early Cretaceous (2) During the Early Cretaceous, the Ziliupai Formation experienced a hydrocarbon accumulation event from early Middle Jurassic to early Late Jurassic.