Heat transfer characteristics at the electric heating cable–fluid interface and temperature prediction model in oil–water two-phase flow

Electric heating in the reservoirs in offshore heavy oil horizontal wells is an effective technology focusing on excessive wellbore heat loss and limited platform space. However, real-time monitoring of downhole cable surface temperature is costly, and the temperature evolution behavior under oil–water two-phase flow conditions remains insufficiently understood, thereby constraining power optimization and operational safety. To address this issue, this study focuses on the heat transfer behavior at the cable–fluid interface, taking the surface temperature of the electric heating cable as the primary research object. By integrating laboratory-scale equivalent experiments, multi-element nonlinear regression analysis, and field fiber-optic temperature monitoring data, the effects of linear power density, water cut, crude oil viscosity, and flow velocity on cable surface temperature are systematically investigated.The results indicate that linear power density is the dominant factor affecting cable temperature. When the linear power density increases from 0.5 kW/m to 1.5 kW/m, the cable surface temperature in steady-state stage rises by 84.1 ℃. Water cut exhibits a negative correlation with cable surface temperature. As the water cut increases from 0 to 60%, the cable surface temperature in steady-state stage drops by 55.9 ℃. In contrast, crude oil viscosity is positively correlated with cable surface temperature, and the steady-state cable surface temperature climbs by 28.1 ℃ when the viscosity rises to 1 000 mPa·s from 350 mPa·s. The influence of flow velocity is relatively weak. Based on the experimental data, a multi-element nonlinear prediction model was established and validated using field fiber-optic monitoring data. The model exhibits sound fitting performance under both operating conditions (without electric heating and with electric heating).The proposed model provides a theoretical basis for the dynamic regulation of electrical heating power in offshore heavy-oil thermal recovery operations and contributes to reducing the risk of cable overheating while improving thermal utilization efficiency.