考虑滑脱的气液两相嘴流新模型

A new model for predicting gas-liquid two-phase choke flow considering the slip

正确预测油嘴允许气液混合物通过的能力是开展油气井井下或地面节流工艺设计的基础,气液两相嘴流模型在采油气工艺中有广泛的应用。通过引入等效动量比容、等效动能速度概念,根据动量守恒原理建立了一个新的考虑气液间滑脱的气液两相嘴流质量流速预测模型,并进行了数值求解。与其他4个模型相比,新模型计算简单且方便。利用公开发表的亚临界流和临界流实验数据对新建模型和其他4个常用两相嘴流模型计算结果进行了比较。新建模型对质量流速预测能力的平均误差为1.37%,平均绝对误差为6.37%,标准差为5.79%;新模型对嘴前压力预测能力的平均误差为2.78%,平均绝对误差为8.43%,标准差为4.10%;明显优于Sachdeva、Perkins、Ashford&Pierce、Al-safran等模型。气液两相滑脱因子计算方法影响模型的准确性,为此对比分析了9个气液两相滑脱因子计算方法,发现本模型结合Chisholm的滑脱因子计算方法的预测结果最接近实验测试结果。同时以某产水气井为例开展了井下节流工艺嘴径计算,新模型设计的嘴径完成的配产率为96.5%。

The accurate prediction on the ability of choke to allow gas/liquid mixture to flow through it is fundamental for the design of downhole or surface throttle process of oil and gas wells.And gas-liquid two-phase choke flow model is extensively applied in oil and gas production process.A new model for predicting the mass velocity of gas-liquid two-phase choke flow was established according to the principle of conservation of momentum based on the concepts of equivalent momentum specific volume and equivalent kinetic velocity,combined with gas-liquid slip ratio,and its numerical solution algorithm was worked out.Compared with four other models,this new model is simpler and more convenient.Then,the accuracy of this newly built model and four commonly used two-phase choke flow models was evaluated by using the published experimental data of subcritical flow and critical flow.It is shown that this new model is much superior to Sachdeva,Perkins,Ashford&Pierce and Al-safran models.Its average error of mass velocity prediction capacity is1.37%,average absolute error is6.37%and standard deviation is5.79%.And its average error of pressure prediction capacity before the choke is2.78%,average absolute error is8.43%and standard deviation is4.10%.The accuracy of this new model is affected by gas-liquid two-phase slip ratio calculation methods.Therefore,9methods for calculating gas-liquid two-phase slip ratio were comparatively analyzed in this paper.It is indicated that the prediction value is the closest to the experimental result when this model is combined with Chisholm slip ratio calculation method.And finally,a certain water producing gas well was taken as the example to calculate the choke diameter of downhole throttle process.And the proration ratio of the choke diameter which is designed based on this new model is96.5%.