摘要
柴达木盆地侏罗系赋存着丰富的煤炭和油气资源,已有钻井和近年施工的页岩气参数井多次证实有页岩气存在。文中在柴达木盆地北缘侏罗系共识别出9个富有机质泥页岩段,对这些泥页岩的岩性、厚度、分布、有机质组成和热演化程度等特征进行研究,分析了柴北缘侏罗系页岩气地质特征。富有机质泥页岩层发育5种岩相类型,包括油页岩、黑色页岩、碳质泥岩、灰黑色泥岩和黑灰色粉砂岩,主要形成于冲积扇-辫状河、辫状河三角洲-泥炭沼泽、扇三角洲和湖泊沉积体系,而最有利的富有机质泥页岩成因环境是湖泊、辫状河三角洲-泥炭沼泽。柴北缘侏罗系富有机质泥页岩层厚度大（平均累计厚度10~916m）;TOC含量为1.24%~8.6%,总体大于4%;有机质类型较好（H1—H4段和H6—H8段为Ⅱ2-Ⅲ型,H5和H9段为Ⅰ-Ⅱ1型）,热演化程度整体处于未成熟-成熟阶段。从古气候、盆地构造演化和沉积古环境3个方面探讨了柴北缘侏罗系页岩气层的控制作用。研究表明,富有机质泥页岩主体形成于古气候潮湿温暖的早、中侏罗世,早侏罗世末和晚侏罗世气候干热化阻断富有机质泥页岩的发育;侏罗纪5个阶段的断陷盆地演化控制着泥页岩层的形成发育,湖西山组沉积期为形成于潜西—冷湖—南八仙地区的快速断陷盆地,沉积了H1—H3富有机质泥页岩段,有机质丰度高,厚度大,结构稳定性较好;小煤沟组沉积期主要为局限发育在潜西和大煤沟地区的断陷速率快慢周期变化盆地,形成了局限分布的H4—H6泥页岩;大煤沟组沉积期为以鱼卡和大煤沟地区为沉积中心的缓慢断陷盆地,形成了与煤层共生的H7泥页岩,有机碳含量高,厚度大,分布稳定;石门沟组沉积期为向东不断迁移的缓慢-快速断陷盆地,沉积了分布不稳定厚度中等的H8泥岩和厚度大,有机质丰度高,区域连续分布的H9泥页岩;采石岭组和红水沟
The Jurassic strata of the northern Qaidam Basin are rich in coal,oil and gas resources,and the shale gas potential was confirmed by recent geological prospecting and exploration.In this paper,geological characteristics and controlling factors of shale gas in the Jurassic of the northern Qaidam Basin were studied.The results showed that a total of 9horizons of organic-rich shale were subdivided in the Jurassic,with H1-H6horizons developed in the Lower Jurassic,and H7-H9developed in the Middle Jurassic.Five types of lithofacies were identified in these shales,including brown oil shale,dark shale with horizontal lamination,dark carbonaceous mudstone,dark mudstone,and grey siltstone.These shales were deposited in alluvialbraided river,braided delta-swamp,fan delta and lacustrine depositional systems,with braided delta-swamp and lacustrine being favorable environments for the accumulation of thick shales.The average cumulative thickness of shale horizons ranged from 10to 916m.The TOC content ranged from 1.24%to 8.6%,with80percent being higher than 4%.Analyses of kerogen types of the organic matter showed that H1-H4and H6-H8shales are of typeⅡ2-Ⅲ,and H5and H9shales are of typeⅠ-Ⅱ1.The Ro values were mainly in the range from 0.32%to 1.37%,indicating that thermal evolution degree were from immaturate to mature stage.Furthermore,paleoclimate,tectonic evolution and depositional environments of these shaly horizons were analyzed.The Lower and Middle Jurassic of the northern Qaidam Basin was dominated by a warm and humid paleoclimate,with some time intervals such as the latest Early Jurassic and the Late Jurassic being dominated by a dry and hot paleoclimate.The thickness,distribution and organic matter of these shales were controlled by a five-stage tectonic evolution.The Huxishan stage was dominated by a rapid rifting basin,in which the H1-H3shales developed in the western part of the northern Qaidam Basin.The Xiaomeigou stage was mainly a rhythmically slow-rapid rifting basin with H4-H6shales locally deposited in
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2014年第4期311-322,共12页
Earth Science Frontiers
基金
国土资源大调查项目(12120114019501)
国家科技重大专项(2011ZX05033-002)
关键词
页岩气
柴北缘
侏罗系
古气候
沉积构造演化
古环境
shale gas
northern Qaidam Basin
Jurassic
paleoclirnate
tectonic evolution
depositional environment
