低渗透稠油油藏水平井产量新公式

THE NEW YIELD FORMULA OF HORIZONTAL WELL IN HEAVY OIL RESERVOIR WITH LOW PERMEABILITY

将水平井的渗流场划分为两部分,以水平井两端点为焦点的椭球体的内部三维渗流和椭圆直井为中心的外部平面渗流。基于考虑了启动压力梯度、二次压力梯度和应力敏感效应的非达西渗流微分方程,利用等值渗流阻力原理和积分、保角变换方法,推导出一个新的低渗透稠油油藏水平井产量公式,为深入认识低渗透稠油油藏水平井的产能变化特征提供了重要评价手段。结果表明:当幂律指数大于0.8时,幂律指数、水平井长度、拟综合压缩系数才对产量有显著影响;当拟综合压缩系数不等于零时,水平井产量与生产压差不再呈线性关系,且产量随流体压缩系数的增大而增大,随应力敏感系数的增而减少;当应力敏感系数较大时,即使生产压差较快增大,产量也上升缓慢;工程上,只有当生产压差大到足以克服启动压力梯度的阻碍效应时,油井才有产量。

The seepage field of horizontal well is divided into the ellipsoid inner three-dimensional fluid flow region,which takes two ends of horizontal well as focus,and the outer radial flow region,which takes ellipse vertical well as a center.Based on the non-darcy seepage differential equation considering the start-up pressure gradient,quadratic pressure gradient and stress sensitive effect,a new horizontal well production formula of heavy oil reservoir with low permeability is deduced by using the equivalent flow resistance law and the integral,conformal transformation method.The proposed production model provides a significant evaluation means for a better understanding of the varying deliverability characteristics of horizontal well in heavy oil reservoir with low permeability.Calculations show that when the power-law index is over 0.8,the influence of the power-law index,length of the horizontal well,pseudo total compressibility coefficient on the yield of the horizontal well become more and more obvious.When the pseudo total compressibility coefficient is not zero,the relationship between the yield and drawdown pressure is no longer a linear relationship,and the yield increase with the increase of the fluid isothermal compressibility coefficient and the decrease of the stress-sensitivity coefficient.When stress-sensitivity coefficient is bigger,the production increases slowly with the increase of drawdown pressure.In engineering,only when the drawdown pressure is big enough,the obstacle effect of start-up pressure gradient is overcome and the oil well will have output.