随钻仪器井下降温系统传热特性研究

Heat Transfer Characteristic Study on Downhole Cooling System of Drilling Instrument

提高随钻仪器抗高温能力是石油工程技术中一个重要的研究方向,而为随钻仪器增加降温装置构成井下降温系统是解决措施之一。鉴于此,基于传热学理论和数值方法,建立了随钻仪器井下降温系统模型,确定了影响传热效果的相关参数,分析了各参数对传热特性的影响规律和影响程度。研究结果表明:(1)影响传热效果的参数有环境温度,钻铤导热率,绝热材料导热率和厚度,电路系统导热率,直径和热功耗,冷端有效制冷功率和直径。(2)钻铤和电路系统导热率对温度变化影响不大;随着环境温度和电路系统热功耗的增加,电路系统温度呈线性增加;随着绝热材料导热率和电路系统直径的增加,电路系统温度呈非线性增加;随着冷端有效制冷功率的增加,电路系统温度呈线性降低;随着冷端直径和绝热材料厚度的增加,电路系统温度呈非线性降低。(3)各参数的影响程度依次为(冷端有效制冷功率/电路系统热功耗)>环境温度>电路系统直径>绝热材料导热率>绝热材料厚度>电路系统热功耗>(冷端直径/电路系统直径)。研究结果可为随钻仪器井下降温系统的设计提供理论支撑。

Improving the high-temperature resistant capacity of drilling instrument is an important research direction in petroleum engineering technology,and adding a cooling device in the drilling instrument is one of the solutions of downhole cooling system.Based on heat transfer theory and numerical method,the downhole cooling system model of drilling instrument was built,the relevant parameters affecting heat transfer effect were determined,and the influence law and degree of each parameter on heat transfer characteristics were analyzed.The study results show that:(1)9 parameters such as ambient temperature,thermal conductivity of drill collar,thermal conductivity and thickness of insulating materials,thermal conductivity of circuitry,diameter and thermal power consumption,and effective cooling power and diameter of cold end affect the heat transfer effect;(2)the influence of the parameters on the temperature fluctuation of circuitry of drilling instrument is as follows:the thermal conductivity of drill collar and circuitry has little effect on the temperature fluctuation;as the ambient temperature and the thermal power consumption of circuitry increase,the temperature of circuitry increases linearly;as the thermal conductivity of insulating materials and the diameter of circuitry increase,the temperature of circuitry increases nonlinearly;as the effective cooling power of the cold end increases,the temperature of circuitry decreases linearly;and as the diameter of cold end and the thickness of insulating materials increase,the temperature of circuitry decreases nonlinearly;and(3)the influence degree of the parameters on the temperature fluctuation of circuitry of drilling instrument is as follows:(effective cooling power of cold end/thermal power consumption of circuitry)>ambient temperature>diameter of circuitry>thermal conductivity of insulating material>thickness of insulating material>thermal power consumption of circuitry>(diameter of cold end/diameter of circuitry).The study results provide theoretical support for the design of downhole cooling system of drilling instrument.