黔西北可乐向斜中段煤层气与致密砂岩气共探潜力评价

针对黔西北（贵州毕节）可乐向斜中段晚二叠世含煤地层具有含煤层数多、主力煤层埋藏较深的特点，结合该区探井钻遇致密砂岩气层的实际情况，从沉积环境、储层厚度、源储配置及含气性等方面评价了该区煤层气与致密砂岩气"两气"共探的勘探潜力。研究表明:可乐向斜下煤组和中煤组分别沉积于龙潭早期和晚期，这两个时期地层主要处于曲流河、河控三角洲平原等沉积相带，有利于煤岩与致密砂岩储层的形成；龙潭组中煤组煤层和致密砂岩层分布较稳定，累积厚度分别在16 m和20 m以上；煤系中煤岩、泥岩、砂岩互层叠置出现，具备良好的源储配置关系，可形成多套"生储盖组合"；根据X1井气测录井和测井结果，在煤层和致密砂岩层均显示全烃值异常，煤层段异常值最大可达78.35%，钻遇的两层致密砂岩层含气饱和度分别为39.97%和12.79%，说明煤系中有"两气"共存的情况。 

Co-exploration potential for coalbed methane and tight sandstone gas in the middle section of the Kele syncline,Northwest Guizhou

Based on the characteristics of multilayer coals and deep main seam for the Late Permian coal-bearing strata in the middle Kele syncline, this paper comprehensively evaluated the co-exploration potential of the "two gases" (i.e., coalbed methane (CBM) and tight sandstone gas) in the terms of depositional environment, reservoir thickness, source-storage configuration and gas content, combining with an exploratory well (X1) of drilling in tight sandstone gas layer. The results showed that:the Kele syncline belongs to the sedimentary facies of meandering river and fluvial delta plain during the Early and Late Longtan periods, which are favorable to the formation of coal and tight sandstone reservoirs. Middle coal group of Longtan Formation is relatively stable, and has cumulative thicknesses more than 16 m and 20 m for coal and tight sandstone layers, respectively, providing a huge reservoir space for the accumulation of CBM and tight sandstone gas. Coal, mudstone and sandstone layers appear in the coal-bearing strata in superposed pattern, which forms several assemblages of "source-reservoir-cap" and has a good configuration relationship between source and storage. According to the well logging of X1, the value of total hydrocarbon is abnormally high up to 78.35%, and gas saturation is about 39.97% and 12.79% for the two tight sandstone layers, respectively. Overall, the study area exhibits a coexistence of "two gases" in the coal-bearing strata.