构造抬升过程中煤储层吸附能力的耦合效应及控制因素

煤层气盆地在地史演化过程中几乎都经历了多次抬升作用，构造抬升作用对煤储层吸附能力有着直接的影响。本文拟通过物理模拟实验和数值模拟对构造抬升过程中煤储层吸附能力的耦合效应和控制因素进行探讨。研究中选取高、低煤阶煤储层样品进行等温吸附实验，并假定地温梯度为分别为2℃/100m、4℃/100m和6℃/100m，压力梯度分别为0.3MPa/100m、0.5 MPa/100m和1.0MPa/100m模拟抬升过程中吸附量的变化。研究结果表明，煤储层在构造抬升过程中的吸附能力的变化主要受温压综合作用、煤储层热演化程度和构造抬升强度的控制。构造抬升时，温度作用效果占主导地位，煤储层吸附量增加；反之，压力作用效果占主导地位，煤储层吸附量减少。高煤阶煤层吸附量的变化量大于低煤阶变化量。抬升强度较大时煤层吸附量持续降低，较小时会使吸附量增加。煤层气在抬升过程中可能会出现吸附或解吸，与以往只是解吸的认识不同。当温度作用效果大于压力作用效果，即煤储层吸附量增加时，抬升作用易导致煤储层的含气欠饱和。

Coupling effect and Controls on Adsorption Capability of Coal Reservoir during Uplift

Coalbed methane produced basins were almost suffered to many times uplift during geological history. The uplift has influences on adsorption of coal reservoir directly. In this study, low rank coal sample and high rank coal sample were collected. Adsorption experiments in 20℃, 40℃, 60℃ were performed. In order to simulate and understand the effects of uplift to adsorption of coals, as well as control factors, assuming the geothermal gradient are 2℃/100m, 4℃/100m and 6℃/100m. Additionally, the pressure gradient is assumed to be 0.3MPa/100m, 0.5MPa/100m and 1.0MPa/100m, separately. The result shows that the adsorption capability of coal reservoir is controlled by factors including geothermal gradient, pressure gradient, thermal evolution degree and uplift strength. In the condition of high geothermal and pressure gradient, the comprehensive adsorption curve from calculation exhibits steep shape, and adsorption variation quality is large. During the process of uplift, the adsorption capability of coal reservoir increases initially and decreases afterwards. In addition, the adsorption capability variation of high rank coal reservoir is larger than low rank coal reservoir’s, which may results from high rank coal reservoir has a stronger adsorption capability. The influence of uplift strength to adsorption capability is complicated. The adsorption capability may decrease sustained caused by high strength and increase by low strength. As the increased amount of uplift, adsorption capability almost exhibits the process of increases initially and decreases afterwards.