The logging tools, which detect the oil and gas distribution underground, are faced with high temperature environments. Generally, the electronics inside the logging tools are incapable of bearing such harsh environments due to the decline of reliability or even complete failure. To ensure the normal operation of the logging tools, a thermal management system for downhole electronics adopts the vacuum flask to insulate the high-temperature environments and utilizes phase change materials (PCMs) for heat storage. Based on thermal management system, the real-time temperature prediction of downhole electronics during the logging process is required as a kind of control strategy in oil and gas industry. In previous researches, the temperature of the logging tools with thermal management system was simulated using CFD commercial software. Despite the accuracy of the simulation results by commercial software, it consumes plenty of computing time. Therefore, the CFD commercial software is unsuitable for predicting the temperature of downhole electronics in real time.     

To tackle this issue, a simplified one-dimensional transient heat transfer model of logging tools was conducted in this work based on Fourier law and energy conservation equation. An equivalent specific heat capacity method was adopted to describe the non-linear phase transition process of PCMs, and then the partial differential equations were solved numerically. To verify this model, the simulated results of CFD commercial software and the results of our model were compared. Afterwards, the computing time of both models was investigated to compare the calculation efficiency. Furthermore, several factors in the predicted temperature including the environmental temperature and the type of PCMs were analyzed using this simplified model.

According to the analyses, the results of the model presented in this work well match the simulated results with the maximum relative error of 8%, indicating that the accuracy of the simplified model is acceptable. Moreover, the computing time of the model is below 1 s, which is obvious shorter than the CFD commercial software (>4 h). In consideration of the accuracy and the computing time, it can be concluded that the presented model of logging tools is able to meet the demand of predicting the temperature of downhole electronics in real time. As for the influence factors in predicted temperature, the results show that the predicted temperature rises with the increasing environmental temperature and the eutectic salts possesses the best temperature control performance among all of the PCMs.


Transient Heat Transfer Model for Real-Time Temperature Prediction of Downhole Electronics

Division / Sponsors: 
Electronic & Photonic Packaging Division (EPPD)

Paper Proceedings: https://asmedigitalcollection.asme.org/InterPACK/InterPACK2020/volume/84041

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