Theoretical Research And Implementation Of Thermal Management System For Logging Tool In High Temperature Environment

Logging tools are utilized to detect the underground petroleum resources,and face the high-temperature downhole environment.The electronics inside the logging tool cannot withstand the high temperature over 200℃.Therefore,a passive thermal management system combined with thermal insulation,heat storage and conduction method is employed to protect the downhole electronics.However,the heat transfer mechanism of the passive thermal management system is still unclear,and there is a lack of effective system-level thermal design and efficient optimization methods.Therefore,the existing thermal management system schemes cannot meet the temperature control requirements of industrial logging tools.This study aims to develop a high-performance and compact thermal management system for high-temperature downhole logging tool.The heat transfer mechanism of the thermal management system was theoretically explored,and the system structures of heat insulation,storage and conduction were designed and optimized.Furthermore,the temperature experiments and downhole applications were carried out in this study.The main results are as follows:The numerical heat transfer model of passive thermal management system including conduction,convection,radiation and phase change was constructed to quantitatively analyze the heat transfer process,and thus revealing the heat transfer mechanism of the logging tool in high temperature well.In addition,a heat transfer model of the logging tool based on the equivalent thermal conductivity method was proposed,which converted the convection and radiation inside the logging tool into the equivalent thermal conductivity of air for a simplified solution.The results show that the proposed model greatly improves the calculation efficiency while ensuring high numerical calculation accuracy.Compared with the conduction-convection-radiation model of the logging tool,the maximum error is only 1.02℃,and the calculation time is shortened by 89.9%.A composite thermal management system for logging tool was proposed,which combined thermos and nano-aerogel thermal insulation technique,distributed phase change materials heat storage design and enhanced heat transfer technology.The distributed heat storage design was employed to overcome the local overheating problem for the multi-heat-source logging tool,and the integrated thermal management system with thermal conduction and heat storage was adopted to realize the efficient heat dissipation for downhole high-power electronics.The proposed thermal management system successfully controls the downhole electronics temperature below 150°C for 9hours in 205°C downhole environment.The temperature control effect is significantly improved compared with the traditional thermal management system.Furthermore,a thermal optimization method of the logging tool combining parametric modeling,thermal simulation,and optimization algorithm was proposed to improve the efficiency of system optimization and obtain the optimal design scheme simultaneously.Through this method,the best balance between the temperature control ability and overall size of logging tool was successfully realized.A one-dimensional transient heat transfer model of the logging tool was established.The model can guarantee the calculation accuracy and the real-time calculation simultaneously.The maximum error between the predicted temperature and the measured temperature is 8.7℃,and the calculation time is only 0.8 s.Based on this model,the real-time temperature prediction application for the high-temperature downhole logging tool was realized.Furthermore,a temperature experiment on the thermal management system of the logging tool was conducted.The internal circuits of the logging tool work normally at 205℃ for 690 min,and the maximum temperature is only 114.2℃.The results indicate that the developed thermal management system can help the domestic nuclear magnetic resonance logging tool to break through the temperature resistance index of 205℃.Besides,the successful application in the 4014 m borehole of the South China Sea also demonstrates the excellent temperature control effect of the developed thermal management system for the logging tool.