崖城气田含水汽凝析气偏差因子预测方法评价

天然气偏差因子是气藏工程计算中一项相当重要的参数，多采用经验公式求取。由于不同计算模型使用范围和精度不同，并且计算凝析气偏差因子的常规方法通常忽略含水的影响，导致偏差因子的计算误差较大。针对以上难点，分别采用不同的计算方法，结合WA、Casey等校正模型，计算含水汽凝析气的偏差因子。通过比较偏差因子的计算值与实验值，评价HY、DBR及DAK三种不同模型在计算含水汽凝析气偏差因子时的适用性。研究表明:在含水汽凝析气的偏差因子计算中，使用校正模型修正后的偏差因子误差明显减小，而随着对比压力p_r的取值不同，3种方法的精度有所不同。当0≤p_r≤3.87时，HY、DBR及DAK等三种方法的计算精度相似；当4.84≤p_r≤6.56时，采用HY或DAK方法的精度较高；而当3.87≤p_r≤4.84和6.56≤p_r≤7.59时，采用DPR方法的精度更高。

Evaluation on the prediction method of Z-factor of gas condensate with water vapor in Yacheng Gasfield

Z-factor of natural gas is one important parameter for gas reservoir engineering calculation, and it is mostly calculated by means of empirical formula.Different calculation methods are different in application range and precision, and the effect of water vapor is usually neglected in the conventional methods used for calculating Z-factor of gas condensate, so the calculation error of Z-factor is larger.In this paper, different calculation methods were adopted respectively to deal with these difficulties.Then, Z-factor of gas condensate with water vapor was calculated by using correction models (e.g.WA and Casey).Finally, the calculated Z-factor was compared with the measured value, and the applicability of three models (i.e., HY, DBR and DAK) to calculate Z-factor of gas condensate with water vapor was evaluated.It is indicated that when Z-factor of gas condensate with water vapor is calculated, the error of Z-factor which is corrected by the correction model is much smaller.The precision of three methods (i.e., HY, DBR and DAK) varies with the value ofreduced pressure (p_r).Their calculation precision is similar while 0≤p_r≤3.87.The calculation precision of HY and DAK is higher while 4.84≤p_r≤6.56.And the calculation precision of DAK is much higher while 3.87≤p_r≤4.84 and 6.56≤p_r≤7.59.