缝洞型凝析气藏试井解释方法初探

Production prediction model of coalbed methane wells in low water production period

缝洞型储层的主要存储空间是裂缝和洞穴,凝析气相态变化复杂,使得缝洞型凝析气藏试井解释方法一直没有被深入研究。根据力学三大守恒定律,定义了凝析气质量流量拟压力,提出缝洞中不仅存在管渗耦合流动,而且压力以波的形式传播。建立了井筒与洞穴相连通情况下的流动方程,并给出了井筒和洞穴之间的流动压差表达式,以此作为地层流动方程的内边界条件以形成完备的流动方程组。在此基础上,建立了缝洞型储层凝析气藏井-洞-缝试井解释模型。经塔里木盆地某井实例应用,试井解释结果洞穴空间体积75.66×10^(4) m^(3),裂缝空间体积551×10^(4) m^(3),解释凝析气动态储量21.5×10^(8) m^(3),与后期物质平衡法计算动态储量22.3×10^(8) m^(3)仅相差3.5%,解释结果与生产实际相符合。新的建模方法首次利用试井资料解释出凝析气藏的洞穴和裂缝体积,是对缝洞型凝析气藏流动方式的一个有益探索。

The main storage space of fracture-cavity reservoirs is fractures and caves,the phase change of condensate gas is complex.Due to these factors,the interpretation methods of the well testing have not been thoroughly studied in fracture-cavity condensate gas reservoirs.According to the three conservation laws of mechanics,and defined the mass flow rate pseudo pressure of condensate gas,it is proposed that there is not only pipe-seepage coupled flow in the fracture-cavity,but also the formation pressure propagates in the form of waves.The flow equation of wellbore-cave has is established,and the flow pressure is provided between the wellbore and the cave.Using this as the inner boundary condition,the complete set of flow equations are established.On this basis,the well testing interpretation model of the well-cavity-fracture is established in the fracture-cavity reservoir condensate gas reservoirs.Applied to a well in Tarim Basin,The interpretation results:the volume of cave is 75.66×10^(4) m^(3),and fracture is 551×10^(4) m^(3),the dynamic reserves of condensate gas is 21.5×10^(8) m^(3),the result of material balance method calculation is 22.3×10^(8) m^(3),the difference between they is only 3.5%.It is the first time to use well testing to interpretation the volume of caves and fractures,which is a beneficial exploration of the flow mode of fractured-cavity condensate gas reservoirs.