甘肃省煤层气产气潜力定量评价方法探讨——以窑街矿区海石湾煤矿为例

Discussion on Quantitative Evaluation Method of Coalbed Methane Production Potential in Gansu Province——A Case Study of Haishiwan Coal Mine in Yaojie Coalfield

为加快甘肃省煤层气勘探开发和煤矿瓦斯地面抽采进程,以窑街矿区海石湾煤矿为例,采用临储压差、临废压差、有效解吸量等评价指标和数值模拟软件中的产气预测相结合的方法对煤二层产气潜力进行了定量评价。结果表明煤二层具有临储压差较小(2.31 MPa)、临废压差较大(6.70 MPa)、有效解吸量较大(8.60 m^(3)/t)、解吸效率较高(3.59 m^(3)/(t·MPa))特征;排采开始较短时间后即可产气,产气阶段的压降空间较大,能很快进入快速解吸和敏感解吸阶段,煤层气解吸效率显著增大;抽采10a直井日产气量平均1 258 m^(3),具有良好的产气潜力。现场直井排采实践也验证了评价结果的准确性。研究成果可为甘肃省煤层气勘探开发和煤矿瓦斯地面抽采提供有效的技术手段和决策依据。

In order to accelerate the exploration and development of coalbed methane in Gansu Province and the surface gas extraction process of coal mines,taking the Haishiwan coal mine in Yaojie mining area as an example,Quantitative evaluation of the gas production potential of No.2 coal reservoir was conducted by combining evaluation indicators such as critical desorption pressure reservoir pressure difference,critical desorption pressure-abandonment pressure difference,effective desorption quantity,and gas production prediction in numerical simulation software with a case study of Haishiwan Coal Mine in Yaojie Coalfield.The results show that the critical desorption pressure-reservoir pressure difference of No.2 coal reservoir is smaller(2.31 MPa),the critical desorption pressure-abandonment pressure difference is larger(6.70 MPa),the effective desorption quantity is larger(8.60 m^(3)/t),the desorption efficiency is higher(3.59 m^(3)/(t·MPa)).Gas will be produced in a short time after the start of drainage.The pressure drop in the gas production stage is large,and it will soon enter the fast desorption and sensitive desorption stage.The desorption efficiency of coalbed methane will increase significantly.It is proposed to show that the average daily gas production in 10a is 1258 m^(3),which has good gas production potential.The results has been verified by the on-site practice of straight well drainage and production of coalbed methane.The research results can provide effective technical means and decision basis for accelerating the exploration and development of coalbed methane and the process of surface gas extraction in coal mines in Gansu Province.