准噶尔盆地南缘急倾斜储层煤层气多层合采产出模拟研究

Simulation study of multilayer coalbed methane production in steeply inclined reservoirs in the southern edge of Junggar Basin

为促进准噶尔盆地南缘具有巨厚、多层、急倾斜地质特征煤储层煤层气的高效开发,基于阜康西区CS18井地质数据,利用Eclipse软件模拟研究了不同层间距、不同排采强度和不同物性参数差异引起的层间干扰条件下急倾斜储层煤层气3层合排的产出特征。模拟结果表明不同层间距的急倾斜储层煤层气3层合采总产出曲线形态基本一致,都呈现出日产气量先增大后降低的趋势。但是随着层间距的增大,第1层由于较高的渗透率使得产气量逐渐增大,而第3层则相反。但是第1层储层的增产量与第3层储层的减产量大部分抵消,储层上倾方向含气量随层间距的增大较下倾方向略快。所以整体上在3层合采过程中,第1层和第3层距离主采层(第1层)越近,其产气量越高,即层间距越大产气量越低。多层合采对于急倾斜储层来说上倾方向和下倾方向也存在差异。随着排采强度增大,上倾方向的储层压力快速降低,这加速了3层合采的进程。而排采强度较低,上倾方向储层因较高的储层压力使煤层气的解吸、产出受到抑制,但随着排采的进行,抑制逐渐消失。含气量和渗透率物性参数差异对多层合采的影响也存在不同,模拟显示中部储层含气量高有利于上部和下部储层煤层气的产出,而渗透率高则抑制上部和下部储层煤层气的产出。

In order to promote the efficient development of coalbed methane(CBM)with extremely thick,multi-layered and steeply inclined coal reservoirs in the southern margin of the Junggar Basin,based on the geological data of CS18 well in Fukang west area,the production characteristics of three-layer steeply inclined CBM reservoir under different interlayer spacing,different drainage intensity and different physical parameters were simulated and studied by using Eclipse software.The simulation results show that the shape of the total gas production curves of steeply inclined reservoirs with different layer spacings are basically the same,and they all show a trend of increasing first and then decreasing daily gas production.With the increase of interlayer spacing,the gas production of the first layer increases gradually due to the higher permeability,while the third layer is opposite.However,the increase in the production of the first layer of reservoir and the decrease of the production of the third layer of the reservoir mostly offset,and the gas content in the updip direction of the reservoir increases slightly faster than that in the downdip direction with the increase of interval.Therefore,in the process of three-layer commingled production,the closer the first layer and the third layer are to the main production layer(the first layer),the higher the gas production,the larger the layer spacing,the lower the gas production.There is also a difference between the updip direction and the downdip direction of multi-layer commingled reservoirs for steeply inclined reservoirs.With the increase of drainage intensity,the reservoir pressure in the updip direction decreases rapidly,which accelerates the process of three-layer commingled production.However,the drainage intensity is low,and the desorption and production of CBM are restrained due to the high reservoir pressure in the updip direction,but with the progress of drainage,the inhibition gradually disappears.The effect of gas content and permeability physical parameters on multi-layer commingled production is also different.The simulation results show that the high gas content in the middle reservoir can make use of the upper and lower CBM production,while the high permeability will inhibit the production of CBM in the upper and lower reservoirs.