海洋地质前沿2024，Vol.40Issue(10)：49-60,12.DOI:10.16028/j.1009-2722.2023.184
海陆过渡相与海相页岩气储层特征差异性分析
The differences in reservoir property between marine and transitional facies shale gas:a case study of the Longtan Formation and the Longmaxi Formation in Nanchuan,Sichuan
摘要
Abstract
The shale strata in Nanchuan area,Sichuan,SW China,include sedimentary types of transitional fa-cies and marine facies.The gas in marine shale represented by the Longmaxi Formation has been commercially developed,while that in the transitional facies shale represented by the Longtan Formation remain poorly under-stood.Based on data from field outcrops,drilling cores,thin sections,argon ion polishing scanning electron mi-croscope,and Formation MicroScanner Image(FMI)imaging logging data,the differences in the characteristics of the two shale reservoirs were analyzed in terms of sedimentary facies,lithological combinations,reservoir condi-tions,mineral components,compressibility,and gas content.Results show that there are great differences in those aspects.① The lithology of Longtan Formation is complex,including silty shale,carbonaceous shale,gray shale,limestone and coal seam,while the Longmaxi Formation is dominated by siliceous shale.② Influenced by litho-logy,organic matter type,and thermal evolution degree,the reservoir space of Longtan Formation is dominated by micro-fractures(grain margin fractures and shrinkage fractures)and inorganic pores,while that of Longmaxi Formation is dominated by organic pores and micro-fractures.③ The shale of Longtan Formation has high clay mineral content(47.6%),low brittle mineral content(35.8%),low Young's modulus(32.3 GPa),high Poisson ra-tio(0.3),strong plasticity,and lower compressibility than those of Longmaxi Formation.④ The average gas con-tent in Longtan Formation shale is 2.2 m3/t,in which 54.5%is adsorption gas;and the average gas content of Longmaxi shale is 5.2 m3/t,in which 43.3%is adsorption gas.Through the difference analysis of the two types of shale reservoirs,the characteristics of Longtan shale reservoir are defined,which are characterized by complex li-thology,high clay mineral content,poor compressibility and high adsorption gas proportion.Therefore,the shale of the first member of the Longtan Formation has large continuous thickness,high gas content,good reservoir physical properties.In overall,it should be the"dessert"section of Longtan Formation.However,due to high clay mineral content,the coupling between geological"sweet spot"and engineering"sweet spot"is worse than that of Longmaxi shale.It is recommended to improve the fracturing technology,increase the volume of fracture net-work transformation and the output of a single well,so as to achieve exploration breakthroughs.关键词
海陆过渡相/海相/龙潭组/页岩气/储层特征/差异性Key words
marine-continental transitional facies/marine facies/Longtan Formation/shale gas/reservoir charac-teristics/difference分类
海洋学引用本文复制引用
刘娜娜,张培先,夏威,高全芳,汪凯明,周頔娜..海陆过渡相与海相页岩气储层特征差异性分析[J].海洋地质前沿,2024,40(10):49-60,12.基金项目
中国石化科技项目"渝东南地区煤层气富集规律及勘探关键技术"(P24118) （P24118）
