鄂尔多斯盆地南缘铜川地区三叠系页岩气形成条件

Triassic Shale Gas Genetic Conditions in Tongchuan Area,Southern Ordos Basin

参照北美海相页岩气和延长陆相页岩气生产实践,对鄂尔多斯盆地南缘铜川地区三叠系延长组长7段页岩气形成条件进行了较为系统的研究。研究认为,铜川地区延长组长7段富有机质泥页岩,分布范围广,单层厚度大(20～25m),有机质碳(TOC)含量较高,有机质类型以Ⅰ型和Ⅱ型为主,有机质热演化程度为低熟-成熟阶段,具备形成页岩气的地质条件;页岩储层孔隙以中小孔为主,溶蚀孔、黄铁矿粒间孔发育,有机质孔较少,以管状孔和平行壁的狭缝状孔为主;页岩储层脆性矿物含量高,有利于微裂缝的形成和后期压裂改造;运用含气页岩测录井、现场含气量解析、等温吸附实验及压裂排采试验分析了页岩含气特征,显示出研究区具有较好的页岩气形成条件,勘探开发潜力较大。

Referring to shale gas production practices in the North American marine facies shale gas and the Yanchang terrestrial facies shale gas projects,carried out systematic study on Triassic Yanchang Formation Member 7 shale gas genetic conditions in the Tongchuan area.The study has considered that the organic matter rich argillutite in the Member 7 has wide distribution range,large single layer thickness(20～25m)and higher TOC content.Organic matter types mainly belong to Type I and Type II,thermal evolution degree is in low-mature to mature stages,thus have provided with geological conditions to form shale gas.Pore sizes in shale reservoir are mainly medium to small pores,dissolved pores and pyrite intergranular pores are developed,with lesser organic matter pores.Pore types have mainly tubular pores and parallel wall slit pores.Shale reservoir has high content of brittle minerals,thus propitious to microfissure genesis and subsequent fracturing reformation.Based on gas-bearing shale well logging and cutting logging,site gas content analyzing,isothermal adsorption experiment and fracturing drainage test have analyzed shale gas-bearing features,and revealed the study area has better shale gas genetic conditions with greater exploration and exploitation potential.