煤储层渗透率拟稳定评价方法

为定量评价煤储层渗透率大小，本文从煤层气井压降规律出发，以压降传播到边界为界限，将煤层气井排水降压段的压降规律分为两个阶段，且压力传播到边界之后的阶段为拟稳定流阶段。在此基础上，基于渗流力学理论和物质平衡原理，结合拟稳定流时地层各点压降速度相等，推导得到基于平均地层压力、井底流压、产水量等数据计算煤层渗透率的计算方法，并对该方法的优点及适用性进行论述，形成计算流程。以A区块为例，采用煤层渗透率拟稳定评价方法对A区块7口井进行煤储层渗透率计算，与稳定流法计算结果进行对比可知，拟稳定评价方法的稳定性及合理性明显优于稳定流法；并形成了A区块渗透率平面分布规律，与该区块排采井产气量变化趋势一致，即高渗区高产、低渗区低产，进一步论证了拟稳定评价法计算煤储层渗透率的可靠性。

Study on the quasi stable evaluation method of coal reservoir permeability

In order to quantitatively evaluate the permeability of coal reservoir, this paper divides the pressure drop process of drainage depressurization section into two stages based on the pressure drop law of coalbed methane well, and the stage after pressure spread to the boundary is quasi-stable flow stage. On this basis, based on the theory of seepage mechanics and the principle of material balance, combined with the equal velocity of pressure drop at each point of formation under the condition of quasi-steady flow, the calculation method of coal seam permeability is deduced based on the data of average formation pressure, bottom hole flow pressure and water production. The advantages and applicability of this method are discussed and the calculation flow is formed. Taking block A as an example, the quasi stable evaluation method of coal seam permeability is used to calculate the coal reservoir permeability of 7 wells in block A. Compared with the calculation results of the stable flow method, it can be seen that the stability and rationality of the quasi stable evaluation method are obviously better than that of the stable flow method, and the plane distribution law of permeability in block A is formed, which has been consistent with the change trend of gas production of the drainage wells in the block. The reliability of the quasi stable evaluation method to calculate the permeability of coal reservoir is further demonstrated.