Abstract The co-existence of gas, water, and monoethylene glycol (MEG) is common in produced fluids of high-pressure gas wells. Accurate predictions on the temperature changes during the choking process are essential for the design and operation of the choke valve. This paper presents an efficient multiphase isenthalpic flash method based on the cubic-plus-association equation of state (CPA EOS) to calculate the choke temperatures. In comparison with the traditional isenthalpic flash algorithm, this new method accounts for the self- and cross-association between polar water and MEG molecules, yielding more accurate enthalpy calculation results and multiphase component distributions for fluids containing water and MEG. The proposed model is validated by field test data with pressures from 8.68 MPa to 119.3 MPa. The average absolute deviations between the calculated choke temperatures and measured values are less than 1.6 °C even for vapor-liquid-aqueous three-phase mixtures at various pressures. Moreover, case studies show that accounting for the association between polar water/MEG molecules contributes to accurate predictions on choke temperatures. At high pressures, the CPA EOS tends to give higher choke temperatures in comparison with those calculated based on the traditional SRK-Peneloux EOS. In contrast, the CPA EOS tends to yield lower temperatures at low pressures.

中文翻译：

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流经井口节流阀的高压气/水/MEG混合物温度预测

摘要 气、水和乙二醇（MEG）共存是高压气井采出液中的常见现象。准确预测节流过程中的温度变化对于节流阀的设计和操作至关重要。本文提出了一种基于立方加缔合状态方程 (CPA EOS) 的高效多相等焓闪蒸法来计算扼流圈温度。与传统的等焓闪蒸算法相比，这种新方法考虑了极性水和 MEG 分子之间的自缔合和交叉缔合，为含水和 MEG 的流体提供了更准确的焓计算结果和多相分量分布。所提出的模型通过现场测试数据进行验证，压力范围为 8.68 MPa 至 119.3 MPa。即使对于不同压力下的气-液-水三相混合物，计算出的阻风门温度与测量值之间的平均绝对偏差也小于 1.6 °C。此外，案例研究表明，考虑极性水/MEG 分子之间的关联有助于准确预测阻塞温度。在高压下，与基于传统 SRK-Peneloux EOS 计算的温度相比，CPA EOS 倾向于提供更高的阻流温度。相比之下，CPA EOS 倾向于在低压下产生较低的温度。案例研究表明，考虑极性水/MEG 分子之间的关联有助于准确预测阻塞温度。在高压下，与基于传统 SRK-Peneloux EOS 计算的温度相比，CPA EOS 倾向于提供更高的阻流温度。相比之下，CPA EOS 倾向于在低压下产生较低的温度。案例研究表明，考虑极性水/MEG 分子之间的关联有助于准确预测阻塞温度。在高压下，与基于传统 SRK-Peneloux EOS 计算的温度相比，CPA EOS 倾向于提供更高的阻流温度。相比之下，CPA EOS 倾向于在低压下产生较低的温度。