阿尔金山前中、下侏罗统页岩气成藏地质条件  

The geological conditions for shale gas accumulation in the Lower-Middle Jurassic,the Frontal Areas of the Altun Mountains

作　　者：周磊[1,2] 康志宏[1,2] 童雪飞[1,2] 王成[1,2] 杨耀东[1,2] 

机构地区：[1]中国地质大学(北京)非常规天然气地质评价及开发工程北京市重点实验室,北京100083 [2]中国地质大学(北京)页岩气勘查与评价国土资源部重点实验室,北京100083

出　　处：《地学前缘》2016年第1期54-63,共10页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(12120113040000);国家自然科学基金项目(41272132)

摘　　要：柴西阿尔金山前经历了早期断陷、中期拗陷和晚期隆升的多期改造叠合,其中早、侏罗世断陷期发育陆相湖盆泥页岩。地堑-半地堑同沉积断裂控制沉积格局,断陷湖盆长轴为北东向,在小梁山凹陷、七个泉断鼻带和铁木里克凸起构造带沉积半深湖-深湖相的泥页岩夹薄层砂岩、粉砂岩。泥页岩空间展布受沉积相控制,因此呈北东向带状连续稳定分布,由阿尔金山前七个泉—红沟子—小梁山构造带向盆地内部厚度逐渐减薄,累积厚度超过300m,有效厚度在50~70m,是阿尔金山前中、下侏罗统工业性页岩气聚集成藏必备的物质保障。研究证实,阿尔金山前中、下侏罗统泥页岩干酪根显微组分腐泥组、镜质组、惰性组的平均含量分别为60.7%、33.1%和6.2%,依据Tissot和Welte分类标准,有机质干酪根类型以Ⅱ型为主。对25个野外样品进行岩石热解测试,TOC含量稳定分布在1%~4%,Ro在0.8%~2.5%,泥页岩有机质含量高,处于成熟-过成熟阶段,生气条件优越。与北美和四川盆地海相页岩相比,阿尔金山前中、下侏罗统陆相泥页岩的黏土矿物含量相对较高,平均含量为52.51%;含硅质脆性矿物含量相对较低,平均含量为37.42%。泥页岩中发育大量裂缝、微裂缝、粒间孔、粒内孔和有机质孔,有利于页岩气富集和吸附。泥页岩比表面积在9.13~18.14m2/g,平均值为13.43m2/g;孔体积在0.026 6~0.088 7cm3/g,平均值0.065 41cm3/g,平均孔径在25.76~72.48nm,平均值为47.87nm。比表面积和孔径呈负相关,孔体积和孔径呈正相关;孔径越小,泥页岩的比表面积越大。TOC含量和Ro与泥页岩表面积呈正相关,表明随着有机质成熟生烃形成的有机质孔对比表面有重大影响,比表面越大为页岩气吸附提供的吸附位越多,储集性能优越。上覆灰泥岩、泥灰岩和膏盐岩盖层区域广泛分布,早期浅埋—中期深埋、多次排烃—晚期抬升有利于页岩气藏的保存The complex structural evolution of the Frontal Areas of the Altun Mountains involves early faulted depression stage,middle depression stage and late uplift stage,in which continental lacustrine shale developed in the Early Jurassic faulted depression.The whole area is north/west-oriented graben or half-graben defined by syndepositional structure,therefore,laminated lacustrine shale interbedded with siltstone and stone deposite in the Xiaoliangshan sag,Qigequan fault nose zone and Tomorlog bugle.The shale continuously distributes along a northeast band and gradually pinches out from the front zone of mountain to basin.The cumulative thickness of shale is more than 300 m and the effective thickness is between 50 and 70m,providing a necessary material condition for shale gas reservoir.The study confirmed that average contents of sapropelinite,vitrinite and inertinite are 60.7%,33.1% and 6.2%,respectively.According to the terminology of Tissot and Welte,the organic matter is dominated by type II-kerogen.Total organic carbon（TOC）content ranges from 1%to 4% and the organic matter maturity varies from 0.8% to 2.5% based on the Rock-Eval pyrolytical data of 25 outcrop samples,indicating that the laminated shale has high organic matter abundance and is in oil and gas generation window,reflecting that the source rock quality is good.The average clay mineral contents and siliceous mineral contents are 52.51% and 37.42%,respectively.Compared with marine shale in the North America and Sichuan Basin,the Lower-Middle Jurassic shale contains higher clay mineral contents and lower siliceous mineral contents.The fracture,micro-crack,inter-particle pore,intra-particle pore and organic matter pore developed in the shale,providing more adsorption sites for methane.The specific surface area of the shale is between 9.13m2/g and 18.14m2/g,with an average of 13.43m2/g;the pore volume varies from 0.0266cm3/g to 0.0887cm3/g with a mean of 0.06541cm3/g;pore diameter ranges from 25.76 nm to 72.48 nm,averaged at 47.87 nm.The specific sur

关 键 词：中—下侏罗统 页岩气 地质条件 阿尔金山前 

分 类 号：P618.13[天文地球—矿床学]