高气液比气井管流压降计算实用方法

阻力系数法是气井两相流压降计算模型中最简单实用的一种方法，然而传统的阻力系数图版多是针对油井条件提出的，仅适用于较低的气液比范围，而且多数图版坐标为英制单位量纲，使用不便。为此，以四川盆地南部和鄂尔多斯盆地66口气液比范围在480～344 360 m³/m³的气井数据为基础，绘制出了适用于高气液比气井的无因次阻力系数图版。首先，基于多相流压力梯度方程，采用无滑脱持液率，根据现场测压数据反算各测点的阻力系数；随后，引入无因次两相雷诺数，绘制阻力系数与两相雷诺数关系图，其中两相雷诺数是关于气、液雷诺数和气液质量比的函数；最后，对上述关系图中的两相雷诺数进行多次回归试算，并将其修正为包含３个修正系数的函数，从而得到了具有较佳拟合关系的新阻力系数图版。利用公开文献的50口气井压降测试数据进行评价，结果表明，该阻力系数法的流压平均相对误差仅为2.48%，流压平均绝对误差仅为5.37%，满足了工程需要。

A practical pressure drop calculation method for pipe flow in gas wells with high gas-liquid ratios

The resistance coefficient method is one of the most simple and practical methods among multiple models calculating the pressure drop of two phase flow in gas wells. However, the traditional resistance coefficient charts are mostly proposed for oil wells, only applicable to such wells with relatively low gas liquid ratio. Besides, most coordinates in the charts are in inconvenient imperial units. In view of this, based on the data from 66 gas wells in south Sichuan and Ordos basins with the gas liquid ratio ranging from 480 to 344, 360 m³/m³, a dimensionless resistance coefficient chart is developed as follows for such gas wells with high gas liquid ratios. First, non slip liquid holdup was adopted，and the resistance coefficient of each tested point was calculated according to site tested data based on the multi phase flow pressure gradient equation. Second, a dimensionless two phase Reynolds number was introduced and the relation schema was drawn between the resistance coefficient and two phase Reynolds number. The two phase Reynolds number was a function of the gas liquid Reynolds number and the gas liquid mass ratio. Finally, upon multiple regression trials for the two phase Reynolds number of the above relation schema, the number to a function with three correction factors was corrected, thus a new resistance coefficient chart was obtained with favorable fitting. The evaluation was conducted on the pressure drop data of 50 gas wells from open literatures, and the results showed that the flow pressure calculated with the proposed method has an average relative error of only 2.48%, and an average absolute error of only 5.37%, fully satisfying the engineering requirements.