瓦斯地面安全高效抽采井网优化数值仿真研究

Numerical Simulation on Optimization of Well Pattern for Safe and Efficient Gas Extraction on the Ground

煤层气田瓦斯抽采井的间距和布置直接关系到瓦斯的抽采速率及总产量,而瓦斯的地面安全高效抽采对于促进煤矿安全生产、提高能源利用率具有重要的战略意义。以吉林某煤田为例,通过室内压汞试验、煤样气体渗透试验和甲烷吸附试验,研究了煤样基质孔隙度、不同压力条件下煤样渗透率和不同温度下煤样的Langmuir等温吸附-解吸特性;采用双孔隙度单渗透率模型对试验井瓦斯抽采历史产量进行拟合分析,并对深部瓦斯抽采井群布置进行系统的模拟计算,揭示了不同井距抽采时抽采井瓦斯产气速率、累计产量、储层压降以及储层瓦斯浓度随时间的变化规律;通过计算分析不同井距时储层的采收率,确定了瓦斯矩形井网抽采时的最优井距。该研究成果可为同类型低阶煤高瓦斯矿井瓦斯地面抽采井网设计提供理论支撑。

The spacing and arrangement of gas extraction wells in a coalbed methane(CBM)field influence the gas extraction rate and total production directly.The efficient extraction of CBM is of great strategic significance for promoting safe production in coal mines and improving energy utilization.Taking a coalfield in Jilin as an example,this paper investigates the matrix porosity,the permeability of the coal samples under different pressure conditions,and the Langmuir sorption isotherm of the coal samples at different temperatures through the mercury injection experiment,CBM permeability experiment and methane adsorption experiment.The dual-porosity and single-permeability model is used to fit and analyze the historical production of the test well,and the CBM production under different CBM drainage well groups is simulated.The variation of gas production rate,cumulative production,reservoir pressure drop in the extraction wells with time are revealed in different well spacings.By calculating and analyzing the recovery factor of the reservoir with different well spacings,the optimal well spacing for CBM rectangular well group is determined.The results can provide theoretical support for the design of the gas surface drainage well pattern in the same type of high CBM mine.