摘要
长期以来,对西北地区盆地常规石油勘探已经取得了巨大突破,但页岩气的勘探仍处于起步阶段。页岩气具有自身的成藏机理,需要特殊的地质条件。通过分析我国西北地区塔里木盆地、柴达木盆地、准噶尔盆地、吐哈盆地、银-额盆地和焉耆盆地页岩分布情况、厚度、面积、总有机碳含量、热演化程度、有机质类型、矿物岩石成分等因素,认为中国西北地区页岩分布面积广泛、厚度大,许多盆地或地区页岩有机碳含量高、热演化程度高、有机质类型好,具备页岩气大规模成藏的地质条件。其中吐哈盆地页岩与塔里木盆地页岩中黏土矿物含量低,石英等脆性矿物含量高,易受外力作用影响形成天然裂缝与诱导裂缝网络结构,有利于页岩气开采。与美国产气页岩的各项指标比较发现,塔里木盆地与准噶尔盆地古生界海相及海陆交互相页岩厚度大、脆性矿物种类多且含量高,但有机质丰度较美国海相产气页岩低,且热演化程度高(大部分处于高-过成熟热解气阶段)。与埋深超过3 000m的古生界过成熟(Ro为0.51%～3%)页岩和浅埋深但有机碳含量偏低(普遍小于2%)的新生界陆相页岩相比,中生界湖相和湖-沼相高有机碳含量(最高值达15.6%)页岩更具有勘探价值。
For a long time,great breakthrough has been made in conventional oil exploration in the basins of Northwest China,however the exploration of shale gas is still in its infancy due to its spectacular accumulation mechanism and controlled by special geological conditions.By analyzing the distribution,thickness,area,total organic carbon content,thermal evolution,type of organic matter and petrographic composition of the shale in Tarim Basin,Qaidam Basin,Junggar Basin,Turpan-Hami Basin,Yin′gen-e′ji′naqi Basin and Yanqi Basin respectively,we consider that the shale is widely distributed in Northwest China,and is characterized by big thickness,high TOC,high degree of thermal evolution,perfect type of organic matter,which is qualified for the geological conditions to form large scale of shale gas reservoir.Among these basins,low clay mineral content and high brittle mineral content such as quartz within shale of Tarim Basin and Turpan-Hami Basin is easy to generate natural fractures and induce fractures influenced by external force.As a result,network structure joint fractures are developed in the shale,which is favorable for Shale gas exploration.Compared with the U.S.marine facies shale,Palaeozoic shale with large thickness in Tarim Basin and Junggar Basin contain a variety of high content of brittle minerals,but have lower TOC and higher degree of thermal evolution.Mesozoic lacustrine facies and paludal facies shale with higher TOC（maximum value of up to 15.6%） have more exploration value if it is compared with the Palaeozoic marine facies shale with depth of more than 3 000 m of which organic matter has a high thermal evolutionary degree,and with Cenozoic land facies shale with lower TOC（generally less than 2%）.
出处
《地质科技情报》
CAS
CSCD
北大核心
2013年第4期139-150,共12页
Geological Science and Technology Information
基金
全国油气资源战略选区调查与评价国家专项"中国重点地区页岩气资源潜力及有利区优选"(2009GYXQ-15)
关键词
西北地区
页岩气
地质条件
岩石矿物特征
地球化学特征
Northwest China
shale gas
geological condition
petrological and mineralogical characteristics
geochemistry characteristics
