柴达木盆地北缘侏罗系页岩油气成藏条件地质地球化学分析

Geological and geochemical analyses on accumulation conditions of shale oil and gas in Jurassic strata of the north margin of the Qaidam Basin

基于柴达木盆地北缘侏罗系中下统富有机质泥页岩厚度、有机地化特征、物性及泥页岩含油气性等的分析研究，探讨了该地区页岩油气成藏的地质条件，对有利的勘探层段和区带进行了预测。结果表明，柴达木盆地北缘湖西山组和大煤沟组富有机质泥页岩厚度大，有机碳含量多在1.5%以上；有机质类型主要为Ⅱ和Ⅲ型；有机质成熟度从未成熟至过成熟皆有；泥页岩中脆性矿物含量约占50%，孔隙度多在1%~8%之间，孔隙类型多样。湖西山组和大煤沟组泥页岩显示出较强的吸附气体能力，多口钻井在泥页岩段存在明显全烃异常。综上表明，柴达木盆地北缘地区湖西山组、大煤沟组2个层位具备形成页岩油气的地质条件，其中湖西山组中上部泥页岩段为页岩油气有利层段，有利区在冷湖4号-5号构造一带；大煤沟组五段为页岩气有利层段、大煤沟组七段为页岩油有利层段，有利区分布于苏干湖坳陷、鱼卡断陷、红山断陷、欧南凹陷和德令哈断陷东部、南部区。

In order to discuss shale oil and gas accumulation conditions and predict favorable prospect areas and exploration layers within the Lower-Middle Jurassic strata in the north margin of the Qaidam Basin, the thickness, organic geochemical characteristics, physical properties, oil and gas content of shale from the Huxishan Formation （J1h） and the Dameigou Formation （J2d） were studied systematically. The result showed that the thickness of organic-rich shale of J1h and J2d are large, and their TOC values are generally greater than 1.5%. The kerogen types of organic matters are mainly type Ⅱ and type Ⅲ. The maturity of organic matters varies from immature stage to over-mature stage. Brittle mineral content is approximately 50%, porosity mainly from 1%to 8%. Shales from J1h and J2d show strong adsorption capacity to gas, and abnormal total hydrocarbon were observed in many wells in gas logging of J1h and J2d shale layer. It indicates that J1h and J2d are essential for the formation of shale oil and gas reservoir. The Middle-Upper Group of J1h is the favorable layer for shale oil and gas, and the favorable prospect area should be mainly located in the Lenhu No.4-5 tectonic belt. The 5th Member of J2d is favorable layer＆nbsp;for shale gas while the 7th Member is favorable layer for shale oil. The favorable prospect areas are mainly located in the Suganhu Depression, the Yuka Fault Depression, the Hongshan Fault Depression, the Ounan Sag, the eastern part and the southern part of the Delingha Fault Depression.