基于R-K-S方程的同心双管注多元热流体传热特征研究

为了解同心双管注多元热流体的传热特征，获得最优的井底蒸汽参数，基于实际气体R-K-S状态方程和质量、能量与动量守恒方程，结合经典地层内瞬态传热模型，建立了同心双管注多元热流体井筒传热数学模型。在验证模型的基础上，分析了井筒内混合汽/气典型传热特征，近井口处无接箍油管和内油管环空之间的温差较小，会导致流体热物性参数剧烈变化，但温度梯度快速趋于一致。应用该模型对非凝结气含量和注汽温度进行了优化计算，结果表明，非凝结气含量增大，井底过热度减小；随着无接箍油管注汽温度升高，井底过热度增加。研究结果表明，注汽参数对井筒内热参数分布有明显影响，现场作业时要根据井眼实际情况优选注汽参数。 

An R-K-S Equation-Based Study on the Heat Transmission Features of Multi-Component Thermal Fluid Injection through Concentric Dual-Tubing

A mathematic model for heat transfer in wellbores when injecting multi-component thermal fluid through concentric dual-tubing was constructed with the goal of better understanding the heat transmission characteristics of multi-component thermal fluid injection through concentric dual-tubing and determine the optimum bottom hole steam parameters.The study involved modeling wellbore behaviors in response to the injection of superheated multi-component thermal fluid through concentric dual-tubing.To establish the model,the actual gas based R-K-S equation of state,the mass,energy and momentum conservation equation and the transient heat transfer model in classical stratum were used.After verification with the model,the typical heat transfer features of the mixed steam/gases within the wellbore were analyzed,and the analysis indicated that a small temperature difference between the integral joint tubing and the inner tubing annulus near the wellhead may lead to dramatic changes in the fluid thermo-physical parameters,but the temperature gradients converge quickly.The content of non-condensing gases and the steam injection temperature were optimized with the model,and the results showed that the downhole superheat degree decreased as the content of the non-condensing gases increased.However,the downhole superheat degree increased as the steam injection temperature in the integral joint tubing increased.The results of the study demonstrated that the steam injection parameters had a significant influence on the distribution of the thermal parameters within the wellbore.The way steam was injected affected wellbore temperatures.Therefore,it was suggested to optimize the steam injection parameters based on the actual boreholes used during field operations.