低渗气藏水平井产能修正公式

PRODUCTIVITY CALIBRATION FORMULA OF HORIZONTAL WELL IN LOW PERMEABILITY GAS RESERVOIR

根据水平井稳定渗流理论，将水平井的渗流场分解为水平面和垂直面2个渗流场，然后分别通过茹科夫斯基变换和保角变换，利用水电相似原理的等值渗流阻力法，推导出考虑启动压力梯度、应力敏感、偏心距的低渗气藏水平井产能计算公式。以某低渗气藏为例，分析以上3个因素对低渗气藏水平井产能的影响。结果表明：应力敏感的存在使低渗气藏水平井产能大幅递减；启动压力梯度也将使气井产能下降，不过降幅较小；由于气体黏度远小于油的黏度，因此，在低渗气藏开发中应力敏感对产能的影响较启动压力梯度要大；当偏心度小于80％时，其对产能的影响不足1％，而当偏心度大于80％时，其对产能的影响将会非常明显。

According to the stable flow theory of horizontal well, the flow field of horizontal well is divided into hor- izontal and vertical flow fields. Based on Zhukovski transformation and conformal transformation method , by means of equivalent flowing resistance method of the principle of water and electricity similarity, the calculation formula for producing capacity of horizontal well in low permeability gas reservoir is deduced that considers starting pressure gradient, stress - sensitivity and eccentricity. Taking a low-permeability gas reservoir for an example, the effect of the above three factors on horizontal well productivity in low-permeability gas reservoir are analyzed. Study results show that presence of stress sensitive and start-up pressure gradient in low permeability gas reservoirs can decrease horizontal well productivity. As gas viscosity is much lower than oil viscosity, stress sensitivity has much effect on horizontal well productivity than starting pressure gradient. When eccentricity is less than 80% , the impact of stress sensitivity is less than 1%, and when the eccentricity is more than 80%, its impact on the capacity is obvious