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乌鲁木齐-大黄山地区煤层气地质条件研究

Study on geological condition of coalbed methane in Urumqi-Dahuangshan Area

  • 摘要: 针对乌鲁木齐-大黄山地区煤层气开发井产气量差异较大这一问题,在施工工艺和排采制度等外在因素影响大致相同的前提下,地质因素成为影响煤层气井产气量差异较大的主要因素。为此,对研究区煤层气地质条件、含气性特征、储层特征等方面进行了分析研究。结果显示研究区煤层具有厚度大、层数多、变质程度低,区内推覆构造发育,地层变形强烈,煤层倾角较大的特点;主要目标煤层空气干燥基含气量0.76~14.2 m3/t,平均8.19 m3/t,CH4体积分数64.68%~89.65%,平均低于80%;煤储层中大、中孔隙所占比例较高,孔隙充填度较低,连通性较好,不同煤层对CH4吸附储存能力有所不同,渗透率分布不均,储层压力梯度大部分低于0.95 MPa/hm,属于欠压储层。

     

    Abstract: According to a big difference between the gas productions of the coalbed methane developed wells in Urumqi-Dahuangshan Area, under the premise of the construction technique and gas drainage system as well as external factors affected as the same, the geological factor became the major factor affected to the high differences to the gas production of the coalbed methane wells. Therefore an analysis study was conducted on the coalbed methane geological conditions, gas content features, reservoir features and others in these area. The study results showed that the seams in the study area had the characteristics of the high thickness, multi seams, low metamorphic grade, the nappe structure developed within the study area, strata deformation serious and the high inclined seam. The air dried basis gas content of the main target seam was 0.76~14.2 m3/t and the average gas content was 8.19 m3/t. The methane concentration was 64.68%~89.65% and the average concentration was lower than 80%. In coal reservoir, the large and medium pores were taken a high percentage, the pore filled was low, the connection was good, different seam would have a different methane adsorption capacity and the permeability distribution was uneven. The pressure gradient of coal reservoir mostly lower than 0.95 MPa/hm and reservoir was the under pressure reservoir.

     

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