鄂尔多斯盆地伊陕斜坡北部煤系非常规天然气成藏特征

The Accumulation Features of Unconventional Gas in Coal-Bearing Strata in the North of Yishan Slope in Ordos Basin

鄂尔多斯盆地伊陕斜坡北部开展煤系非常规天然气赋存特征的研究属国内首次。本文依据泥页岩、煤层、致密砂岩层地球化学、储层物性、含气性、气体同位素等数据分析了研究区煤系非常规天然气的赋存特征。研究表明煤及富有机质泥页岩为非常规天然气系统的烃源岩,二者有机质处于高-过成熟度阶段,其中煤层为主要生气层,占总生气量的87.5%;致密砂岩的孔隙度最大,煤层其次,页岩孔隙度最小;砂岩渗透率最大,高出泥岩与煤层一个数量级;泥页岩中气体主要以平行于层面的方式运移。在含气性方面,泥页岩含气量平均为3.35 m^3/t,砂岩为5.04 m^3/t,而煤层中总含气量达22.39 m^3/t。太原组、山西组各气藏均属于煤型气藏,该结论对研究区煤系"三气"共采具有较强的指导意义。

It is the first time to study the hosting features of unconventional gas in coal-bearing strata in the north of Yishan Slope in Ordos Basin in China. Carboniferous-Permian coal measures strata is one of the main layers of coalbed methane,shale gas,tight sand gas enrichment and reservoirs in Ordos Basin. According to the geochemisty,reservoir properties,gas content,gas isotope of shale,coal and tight sand,this paper analyzes the hosting features of unconventional gas in coal-bearing strata in the study area. This study shows the source rocks of unconventional gas system are coal and organic-rich shale,whose organic matter are both in high-too maturity stage. Coal is the mainly generating gas layer,87. 5% of total amount of gas. The porosity of tight sand is maximum. The porosity of coal is secondly. The porosity of shale is minimum. The permeability of sand is maximum,which is up an order of magnitude than shale and coal. The gas in shale is mainly in the way of migration by paralleling to the level. In terms of gas content,the gas content of shale is 3. 35 m^3/t. The gas content of sand is 5. 04 m^3/t. The gas content of coal is 22. 39 m^3/t. Each reservoir in taiyuan group and shanxi group are coal gas accumulation,The conclusion of the study area mining has strong guiding significance for＂Three coal gas＂co-mining of coal measures.