气井油管流压梯度计算方法的改进

从２０世纪40年代气井平均温度和平均偏差系数计算井底压力的文章发表以来，又有不少新算法相继问世，Cullender & Smith^［1］和Aziz^［2］发表的计算方法可谓是诸法中的姣姣者。在如何算准气井复杂井流油管流压梯度方面，沿循Cullender & Smith的思路，但做了三方面改进：一是对原来积分中的被积函数进行了置换；二是没有将油管全长等分为二进行计算，300 m一个步长，从井口依次算到管鞋；三是将被积函数中的温度变量直接植入大庆地区气井的实测资料，以提高计算精度。比较改进前后的计算结果，并用实测资料验证，表明使用该方法计算的井底压力值更准确。

MODIFICATIONS TO THE CALCULATION METHOD OF FLOWING PRESSURE GRADIENT IN GAS WELL TUBING

After many papers on bottomhole pressure calculated by average temperature and deviation factor of gas wells were issued in 1940's, much more new methods have come to birth continuously, among which those presented by Cullender &; Smith and Aziz were both outstanding. Based on Cullender &; Smith's method, modifications in three aspects were made to improve the accuracy of pressure gradient calculation for complex tubing flow in gas wells. The first was permutation of the original integrand; the second was calculation integrally from the wellhead to the casing shoe with 300 meters as a step; and the third was application of temperature data measured from gas wells in Daqing oilfield to substitute the variable in the integrand. Proven by practical data, the modified method provides more accurate solution of bottomhole pressure.