鄂尔多斯盆地石炭系本溪组页岩气成藏条件及勘探潜力

近年,国外海相地层页岩气勘探开发取得的重大成果对国内陆相及海陆过渡相页岩气勘探潜力的研究带来重要影响。基于鄂尔多斯盆地石炭系本溪组富有机质泥页岩样品的有机地球化学、物性特征及等温吸附等方面测试结果的数理统计及其测井响应特征分析,对其页岩气的勘探潜力进行了研究。研究结果表明:本溪组有效泥页岩单层厚度变化较大,盆地主体部位有机碳含量一般大于1.0 % ,平均为2.7 % ,有机质类型主要为Ⅲ型和Ⅱ₂型,含少量Ⅰ型和Ⅱ₁型,镜质体反射率平均为1.52 % ,泥页岩吸附含气量平均为0.98 m³/t,属于成熟-高成熟阶段富有机质泥页岩,具备页岩气成藏的基本地质条件。综合考虑泥页岩有效厚度、有机质含量及类型、热演化程度、含气量及埋深等因素,预测鄂尔多斯盆地本溪组页岩气有利勘探区主要位于天环坳陷西北角、陕北斜坡带东北角及盆地中南部等区域。

Shale gas accumulation conditions and exploration potential of Carboniferous Benxi Formation in Ordos Basin

In recent years, the domestic study on continent and marine-continental transitional facies shale gas has been affected greatly by significant research achievements of overseas marine-facies shale gas exploration and development. In order to study the shale gas exploration potential of Carboniferous Benxi Formation in Ordos Basin, organic-rich shale samples from Benxi Formation were employed to test their organic geochemistry, physical properties and isothermal adsorption and other natures. Furthermore, parameters obtained in this study were employed to estimate the exploration potential of these shales by applying mathematical statistics and analyzing logging response characteristics. The result shows that the effective shale thickness of Benxi Formation varies greatly, its TOC is greater than 1 % in general and is 2.7 % on the average, organic matter types are mainly type III and type II₂ with a little type I and type II₁, vitrinite reflectance averages 1.52 % , and shale-gas adsorption content is 0.98 m³/t on the average. These indicate that Benxi Formation has essential conditions for the shale-gas reservoir formation. In terms of the effective thickness of mud shales, organic matter content and type, degree of thermal evolution, gas content and deep burial, favorable prospect areas of Benxi Formation shale gas should be mainly located in the northwest corner of Tianhuan depression, the northeast corner of Shaanbei slope and the central-southern part of Ordos Basin.