鄂尔多斯盆地东南部下寺湾—云岩区二叠系山西组页岩气形成条件

Forming conditions of shale gas of the Shanxi formation of Permian in the southeast of Orldos basin

鄂尔多斯盆地东南部下寺湾—云岩区页岩气资源量较大,二叠系山西组作为主要的目的层系之一.基于钻井资料和暗色泥页岩样品化验资料,从暗色泥页岩生烃条件、储层特征、含气性等方面研究研究区山西组暗色泥页岩中页岩气的形成条件.结果表明:山西组暗色泥页岩分布广泛,且厚度大,平均厚度为80m,有机碳质量分数较高(平均为2.37%),有机质类型以Ⅰ、Ⅱ型为主,成熟度处于成熟—过成熟阶段,具有很强生烃潜力.矿物组成以石英和黏土矿物为主,黏土矿物中主要为伊蒙混层,吸附能力强.硅质、碳酸盐岩等矿物较多,岩石脆性大,造缝能力强.研究区山西组泥页岩中裂缝极为发育,储集条件优越,泥页岩段气测显示活跃,结合页岩含气层显著的测井响应,显示暗色泥页岩段含气性好,页岩气资源潜力较大.鄂尔多斯盆地东南部下寺湾—云岩区二叠系山西组具有良好的页岩气形成地质条件,厚层泥页岩分布区如下寺湾区、云岩区北部黑家堡、关庄及研究区中部延安等,是页岩气成藏的有利发育区.

A large amount of shale gas resources is buried in Xiasiwan-Yunyan area,the southeast area of Ordos basin,the exploration and development of Shanxi formation of Permian,one of the target layer of shale gas exploration,has become the focus.Based on drilling data and oil shale sample testing analysis,the forming conditions contains hydrocarbon generating conditions,reservoir characteristics and gas-bearing properties,from these three aspects,the forming conditions of shale gas in dark shales in Shanxi formation in the study area.The basin has been studied.It is believed that the dark shales in the Shanxi formation is wide in distribution and large in thickness,with the average thickness 80 m,high abundances of organic matter and the average is about 2.37 percent,the main kerogen type isⅠand Ⅱ,the maturity of organic matter is from mature to high mature stage,strong hydrocarbon generation capacity.Mineral composition mainly contains quartz and clay minerals,illite smectite mixed layer is the main part in clay minerals,which means strong adsorption ability.The quartz and carbonate rock are large in percentage,so rock is easily broken,fractures is easy made.According to core observation,we find that fractures was well developed,which stands for good reservoir conditions.Active gas tests show great exploration potential of shale gas in the dark shales of Shanxi formation,combing with the obvious response characteristics of shale gas of logging curves.Comprehensive analysis shows that of Permian in the southeast of Oldos basin has favorable geological conditions for forming shale gas reservoirs,favorable shale gas accumulation areas,such as Xia siwan,Hei jiabu and Guan zhuang in the north of Yun yan area,Yan'an in the central of the study area,dark shales has large in thickness in these areas.