多井条件下煤层气不定常渗流问题的数值研究

NUMERICAL STUDY ON COALBED METHANE TRANSIENT SEEPAGE FLOW WITH MULTI-WELLS

建立了在多井条件下考虑井筒储存和表皮效应的煤层气不定常渗流模型。对于不同外边界如圆形、矩形以及任意四边形煤层中存在不同源汇情况下的不稳定渗流问题进行了求解,得到了该问题在不同时间下的压力场分布,并对压力扩展过程进行了分析讨论,认为压力传播过程在早期是不受边界形状和边界性质影响的,在压力传播到边界之前源汇性质对压力传播过程有明显影响,在汇与汇之间不存在等压线,相当于封闭边界的情况;在源与源之间存在等压线,相当于定压边界的情况。

A new coalbed methane transient seepage flow model with multi-wells is developed by considering the wellbore storage and skin effect. The problem is solved for the different outer boundaries, such as the circular, the rectangular and the arbitrary quadrilateral boundaries, coalbed boundaries with varied sinks and sources in the calculation region. The pressure distributions are obtained at different times in the model regions. From the pressure propagation process, it shows that the shape and properties of boundaries do not affect the pressure propagation in the early stage; and the sinks and sources strongly affect the pressure propagation before the pressure wave meets any kind of boundaries. The results also show that there is no pressure contour line between two sinks, which means that there is a streamline as a closed boundary does. For two sources, there must be a pressure contour line between them, which means that there is a streamline as a constant pressure boundary does. All these results supply fundamental theories to the reasonable development of coalbed reservoir.