Enrichment conditions and main controlling factors of continental shale gas in the Permian Lower Wuerhe Formation in the Dongdaohaizi Sag,Junggar Basin
Enrichment conditions and main controlling factors of continental shale gas in the Permian Lower Wuerhe Formation in the Dongdaohaizi Sag,Junggar Basin
[Objective]To explore the enrichment conditions and main controlling factors of shale gas in the Lower Wuerhe Formation of the Permian System in the Junggar Basin,the Lower Wuerhe Formation in the Dongdaohaizi Sag was selected as the research object.[Methods]Based on the data of outcrop,core,well logging,well-cali-brated seismic reflections and the technologies of total organic carbon(TOC)content determination,whole-rock X-ray diffraction,gas adsorption(N2,CO2),the distribution characteristics,organic matter development characteris-tics,reservoir characteristics,and gas bearing characteristics of the Lower Wuerhe Formation shale were studied.[Results]The results show that:(1)The organic matter of the Lower Wuerhe Formation shale is dominated byⅡ2 and Ⅲ types and shows an average TOC content of 1.58％.The average vitrinite reflectance(Ro)of organic matter is 1.46％,which indicates the mature stage.The average thickness of the source rock is 75 m.Summarily,the source rock is good and has a high gas potential.The basin simulation results show an average shale gas content of 1.89 m3/t in the Lower Wuerhe Formation.(2)The pores and microfractures in shale reservoirs are highly de-veloped,and gas is primarily adsorbed in micropores and mesopores.The average porosity and permeability are 6.10％and 0.27×10-3 μm2 respectively,which are favourable for shale gas accumulation.(3)The shale has a high clay mineral content,with an average of 29.6％,providing a significant specific surface area and enhancing the gas adsorption capacity of the shale.Additionally,the average brittle mineral content is 50.9％,indicating good frackability.(4)Moreover,the shale reservoir exhibits a relatively large pressure coefficient of 1.58,indica-ting the favourable conservation conditions.The analysis of the regional tectonic-sedimentary environment and geo-chemical parameters indicates that the main factors controlling shale gas accumulation in the Lower Wuerhe Forma-tion of the Dongdaohaizi Sag are geochemical parameters and preservation conditions.The key factors influencing shale gas accumulation include the high thermal evolution maturity of organic matter,large shale thickness,high TOC content,and good preservation conditions.These conditions suggest that the favourable area for shale gas ex-ploration and development in the Dongdaohaizi Sag is located in the northeastern slope area of the sag's abdomen.[Conclusion]The results of this research reveal the enrichment conditions and main controlling factors of shale gas in the Lower Wuerhe Formation in the Dongdaohaizi Sag,which has reference value for deep oil and gas exploration in the abdominal area of the Junggar Basin.
关键词
陆相页岩/页岩气富集/主控因素/下乌尔禾组/东道海子凹陷/准噶尔盆地
Key words
continental shale/shale gas enrichment/main control factor/Lower Wuerhe Formation/Dongdaohaizi Sag/Junggar Basin
维普
万方数据