低渗透含水气藏储层评价参数研究

利用恒速压汞、核磁共振和低渗透物理模拟实验研究手段,研究了低渗透含水气藏特点,将喉道半径、束缚水饱和度和临界压力梯度这3个重要参数作为低渗透率含水气藏储层评价的指标参数。研究结果表明:对于不同渗透率的低渗透气藏岩心,其孔道半径基本相同,而喉道半径不同。渗透率与束缚水饱和度有很好的相关关系,在不同的气驱水过程中,其束缚水饱和度是可变的。在含水饱和度很小时,气体渗流符合达西规律;当含水饱和度达到一定值时,气体渗流表现为非线性渗流特性,存在临界拟压力梯度或临界压力梯度。这三个参数不仅对计算低渗透率含水气藏的天然气可采储量有重要作用,而且也对低渗透率气藏渗流规律的研究和气田开发方案设计有重要意义。

Research on reservoir evaluation index for low-permeability water-bearing gas reservoir

The features of low-permeability water-bearing gas reservoir were analyzed by using the rate controlled mercury injection, nuclear magnetic resonance and physical simulation technologies. The three parameters of throat radius, irreducible water saturation, critical pressure gradient of low-permeability gas reservoir were regarded as the evaluation indexs for low-permeability water-bearing gas reservoir. The research results show that the pore radius is basically same, but the throat radius is different in the low-permeability cores with different permeability. The permeability of cores has a high correlation with irreducible water saturation. The irreducible water saturation varies with the different process of gas drive. When water saturation is very low, gas permeation in low-permeability cores follows the Darcy flow. When water saturation gets up a certain value, gas permeation in low-permeability cores shows the characteristics of nonlinear flow. The above three parameters have the important significances to calculate recoverable gas reserves and to research porous flow in the low-permeability water-bearing gas reservoir. These parameters are also favorable to design the developing scheme of gas reservoir.