低渗油藏中含启动压力梯度水平井生产动态

The Performance of a Horizontal Well With Starting Pressure Gradient in Low Permeability Reservoirs

水平井渗流为三维流动，远比垂直井的渗流复杂，因而水平井的压力产量公式往往非常复杂，为了简化，进行了一些理论分析．在没有边界影响的情况下，水平井生产时在地层中形成的等压面是一个旋转椭球面．从水平井椭球流态出发，用平均质量守恒方法，在椭圆坐标内分析具有启动压力梯度的低渗油藏中水平井的生产动态．包括稳态条件下，即椭球供给边界油藏、底水油藏中的近似压力分布和产能公式，分析了启动压力梯度对原油生产的影响：１．生产压差一定时，启动压力梯度越大，水平井的产量越低，且启动压力梯度的影响与水平段的长度平方成正比，２．存在启动压力梯度时，水平井产量随井长的增加呈变斜率增长，当启动压力梯度很大时，存在最佳水平井长；以及水平井在具有启动压力梯度的双重介质油藏中的不稳定渗流压力近似公式，并绘制了相应的试井理论图版，分析了启动压力梯度的影响，在启动压力梯度为零时，经过与精确解对比，表明近似解是适用的．所得到的所有公式均有常规项（不考虑启动压力梯度时的公式）和启动压力梯度项组成，形式简单，易于理解和应用．

The porous flow of oil to a horizontal well bore is 3D flow, and it is more complex than that to a vertical well bore. So the formulae discribing the oil output and pressure distribution of a horizontal well are always very complex. In order to simplity them, some research work was done. It can be proven that the isobaric surface in the formation around a working horizontal well is a rotating ellipsoid. Based on the elliptic flow, the performance of a horizontal well with starting pressure gradient in low permedbility reservoirs was studied by average mass conversation method. The formulae describing its output and pressure distribution were derived under steady porous flow state. The influence of starting pressure gradient on the output is analysed, and it is conclused that, 1) the output is decreased with the increase of starting pressure gradient under constant pressure drop; 2) the slope coefficient is varing with which the output is increased with the length of a horizontal well, and there is the best length. A approximate pressure distribution formula and some typical testing curves were gained under the unsteady porous flow state in dualporosity media. Its result is agreeable to the accurate result obtained by Green Function when starting pressure gradient equels 0.