津巴布韦Karoo盆地煤系气资源禀赋及开发建议

Assessment of Development Potential of Coal-measure Gas Resources in Karoo Basin,Zimbabwe

为研究津巴布韦Karoo盆地煤层气资源禀赋,基于Karoo盆地5口参数井岩心,分析了Karoo盆地的煤组厚度与空间展布;基于密度测井曲线、伽马曲线,以岩心密度<2g/cm^3、灰分含量<50%为判定依据,分析了煤组内煤层分布及厚度;基于吸附-解吸实验结果,运用统计学方法研究了煤样的甲烷含量,并分析了甲烷含量与灰分含量的关系;基于国内外煤层气高产井的埋深、含气量、渗透率、储层压力、煤阶等指标和煤系气地质赋存的特殊性,评估了Karoo盆地煤系气资源的开发潜力,研究认为Karoo盆地煤系埋藏位于600m以浅,厚度超过100m,分布范围广,煤层数量多,单层厚度小,煤岩层交替分布,煤层累计厚度15~25m,具备良好的生气、储气条件,煤层含气量与煤样灰分含量呈负相关,Karoo盆地煤系地层煤层气含气量、煤层埋深符合高产开发条件。最后,借鉴中国煤层气开发经验,提出初步的开发建议,为开发津巴布韦煤层气资源开发提供了参考。

In order to study the coal bed methane resources in Karoo basin of Zimbabwe,the thickness and spatial distribution of coal formation are analyzed based on cores of 5 parameter wells in Karoo.Distribution and thickness of the coal bed in the formations are analyzed according to less than 2 g/cm^3 of core density and less than 50% of ash content based on DEN and GR.The relationship between methane content and ash content is analyzed after the methane content of the coal samples is researched by statistics method based on adsorption and desorption experiment results.The factors of high production well including burial depth,gas content,permeability,reservoir pressure and coal rank are analyzed respectively.The development potential of coal-measure gas resources in Karoo Basin is assessed based on the factors above and geological particularity of the coal-measure gas.The results indicate that the thickness of coal measure is more than 100 m,and the depth of it is less than 600 m in Karoo Basin.The coal measure is characterized by wide distribution,a large amount of coal beds,thin single coal bed,alternating distribution with rock formations.The total thickness of coal bed is 15 to 25 m,which is suitable for generating and reserving gas.The gas content of coal beds has nega-tive correlation with the ash content of the coal beds.The gas content of the coal bed methane and the burial depth of the coal beds in the coal-measure formation in Karoo Basin meet the demands of the development with high production rate.Several reasonable suggestions are proposed guiding the development experiences of Chinese coal bed methane,which provides reference for the development of coal bed methane in Zimbabwe.