叠置含气系统煤层气开采物理模拟试验方法研究

为了研究滇东-黔西地区的多层叠置含气系统煤层气开采过程中储层参数和产量的时空动态演化特征,在多层叠置含气系统的特殊煤层气成藏模式和已有试验设备的基础上,对煤层气开采系统进行了改造和升级,煤层气开采系统由开采管、开采管路和气水分离器以及其他附件组成。建立一套集合材料选取、试件制备和煤层气开采的煤层气开采物理模拟试验方法,最后对试验系统和方法的优势、今后改进方向和适用条件进行了汇总。为了对开采物理模拟试验方法进行效果验证,以直井为例开展了叠置含气系统煤层气开采试验,研究了4个煤层在煤层气开采过程中的瓦斯压力、煤层温度、煤层变形、产量等参数动态演化规律。结果表明:瓦斯压力以井筒为中心近似呈现椭圆状,越靠近井筒区域瓦斯压力越小,反之越大,气体运移速度由近井段向远井段逐渐降低;煤层温度下降量在煤层内以井筒中轴线为起点呈圆弧状向边界递减,越靠近井筒区域温度下降量越大,反之越小;1—4号煤层在第360分钟的最终体积应变分别为0.000 67、0.001 09、0.001 17、0.001 54,初始瓦斯压力越大的煤层,其最终的变形量也越大,且初始瓦斯压力越小的煤层,体积应变增长速率变缓的时刻越早;瞬时产量曲线呈现在开采初期迅速达到峰值并急剧下降的单峰曲线类型。研究结果验证了叠置含气煤层气开采物理模拟试验方法的可靠性,能够为现场煤层气开采提供参考。

Study on physical simulation test method of coalbed methane production in superimposed gas-bearing system

In order to study the spatio-temporal dynamic evolution characteristics of reservoir parameters and production during the coalbed methane(CBM)production of multi-superimposed gas system in the eastern Yunnan and western Guizhou area,the CBM production sys?tem has been reformed and upgraded for the special CBM reservoir-forming characteristics and existing testing equipments.The compo?nents of the coalbed methane mining system consists of drainage pipes,gas-water separators,production pipelines,and other accessories.A set of physical simulation test methods for CBM production was established for the selection of aggregate materials,specimen preparation and coalbed methane mining.Finally,the advantages of the test system and method,the future improvement directions and the applicable conditions were summarized.In order to verify the effect of physical simulation test method,a vertical well was used as an example to carry out a coalbed methane mining experiment with a superimposed gas-bearing system,and the dynamic evolution law of gas pressure,coal seam temperature,coal seam deformation,production and other parameters in the process of coalbed methane mining in four coal seams was studied.The experimental results show that the gas pressure is approximately elliptical with the wellbore as the center.The closer to the wellhole,the lower the gas pressure,and vice versa.The gas migration speed gradually decreases from near well section to far well section.The temperature decreases from the central axis of the wellbore to the boundary.The closer to the wellbore,the greater the temperature drop,and vice versa.The final volumetric strains of coal seams 1 to 4 at 360 min is 0.00067、0.00109、0.00117、0.00154,respectively,and the larger the initial gas pressure of the coal seam,the larger the final deformation.The lower the initial reservoir pressure is,the ear?lier the volumetric strain growth rate slows down.The instantaneous production curves show a single peak curve type which quickly reaches the peak and drops sharply in the early stage.The research results verify the reliability of the physical simulation test method for superim?posed gas-bearing coalbed methane mining,and can provide a reference for on-site coalbed methane mining.