气井气水两相节流温降模型

A choke heat drop model for gas-water two-phase flow in gas wells

准确预测气液两相节流温降是井下节流天然气水合物防治和携液分析的前题。基于能量守恒原理和Peng-Robinson状态方程,结合Huron和Vida1提出的含强极性物质体系的GE(超额吉布斯能量)混合规则和UNIFAC活度系数模型,建立了气—水两相节流温降数学模型。利用天然气—水节流压降温降实验数据验证了该模型的正确性,平均误差为-0.49℃(-2.55%),平均绝对误差为0.76℃(3.80%),标准差为1.13℃(5.40%),明显优于Perkins的热力学模型。以广安002-38有水气井气体组分数据为例,进行了不同气水比下的节流温降计算,当GWR<800m3/m3时,地面节流不会生成天然气水合物,由此无需将嘴子安装在井下。

it is the premise for gas hydrate prevention and liquid-carrying analysis to accurately predict the choke heat drop in the gas-water two-phase flow. Based on the principle of energy conservation and the Peng-Robinson state equation, and in combination with Huron&Vidal's GE (Gibbs Energy) mixed rule of polar material system and UNIFAC activity coefficient model, a mathematical model is established for the choke heat drop prediction in the gas-water two-phase flow. The model is verified using the gas-water experiment data. The average error is -0.49℃(-2.55%), the mean absolute error is 0.76℃ (3.80%), and the standard 1.13℃(5.40%), which is superior to the corresponding results of the thermodynamic model of Perkins. Taking the Guang'an 002-38 well's gas composition as a case of study, we calculated the temperature drop for choke flow with different gas-water ratio, and found that the ground throttle will not result in gas hydrate when the gas-water ratio is smaller than 800 m3/m3. Therefore in such a case, the choke does not need to be installed downhole.