动边界双渗透油藏低速非达西渗流试井模型

A well test model of low-velocity and non-Darcy flow in double-permeability oil reserviors with moving boundary

考虑启动压力梯度与动边界的影响,建立了微可压缩双渗透油藏低速非达西渗流有效井径试井的数学模型,对时间和空间变量进行离散化求出其数值解;进一步分析了压力动态特征,绘制了有界油藏定压条件下的典型曲线,得到了动边界的传播规律,结果表明:双渗透油藏的特征曲线出现层间窜流段,压力导数曲线出现一明显的"凹子","凹子"的深度受启动压力梯度、地层系数比、层间储容比及层间窜流系数的影响。动边界的传播主要受启动压力梯度的影响,启动压力梯度越大,动边界传播越慢;动边界传播末期稳定于一个值,说明低渗透油藏的单井控制面积是有限的。

By considering the influences of thresh- old pressure gradient and moving boundary, a mathematic well test model of low-velocity and non-Darcy flow was built for double-permeability oil reservoirs, and its numerical solution was obtained through discretizing the time and space variables. Fur- thermore, the propagation pattern of moving boundary was drawn by analyzing the dynamical pressure feature and plotting the typical curves of bounded oil reservoirs under a constant pressure. These results have shown that there are interlayer-cross- flow segments in the characteristic curves of double-permeability reservoirs, and that there is an obvious ＂ concave＂ in the pressure derivative curve, with its depth controlled by threshold pressure gradient, formation coefficient ratio, in- terlayer storage ratio and interlayer crossflow co- efficient. The propagation of moving boundary is mainly controlled by the threshold pressure gradi- ent, and the higher the threshold pressure gradi- ent, the slower the propagation o{ moving bound- ary. The moving boundary will keep a constant value at the end of its propagation, indicating that the single-well control area will be limited in low- permeability reservoirs.