极地钻井液冷却用板式换热器设计及换热性能模拟研究

Design of a plate heat exchanger for cooling drilling fluid in polar regions and numerical simulation on its heat transfer performance

摘要:

在极地开展冰下基岩取心钻探，对研究冰下地质构造、揭示冰盖演化历史、评估未来气候变化等均有重要的意义。在极地冰下基岩钻探过程中，钻井液在孔底循环后温度可能升高至0 ℃以上，进而在上返过程中融化冰孔孔壁，导致井壁失稳，甚至引发卡钻事故。为此，有必要研发极地钻井液冷却系统，在地表将钻井液冷却至较低的温度后再注入孔内，进而使钻井液在循环过程中始终保持在0 ℃以下。换热器是钻井液冷却系统的核心部件。本文选用板式换热器做为钻井液的换热部件，采用平均温差法确定了板式换热器的换热面积和基本参数，然后使用COMSOL Multiphysics 6.0软件对板式换热器的换热性能进行了数值模拟。研究结果表明，该换热器可将钻井液冷却至-4~-3 ℃；此外，模拟结果表明，钻井液的出口温度随载冷剂注入温度的降低和载冷剂流量的增大而降低；钻井液的类型对换热器的换热性能有较大影响，而换热板片的材质对换热器的换热效果影响不大。

关键词:极地钻探;冰下基岩取心;钻井液;冷却系统;板式换热器

Abstract:

It is of great significance to carry out subglacial bedrock core drilling in polar regions for studying subglacial geology， revealing the evolutionary history of ice sheets and evaluating future climate change. The temperature of the drilling fluid may rise above 0°C after circulating at the bottom of the hole When drilling subglacial bedrock in polar regions， which may cause the wall of the icy hole to be melted during upward return， resulting in the instability of the wall， and even triggering the stuck drilling accident. It is necessary to design a drilling fluid cooling system that cooling the drilling fluid to a lower temperature before injecting it into the borehole， thereby keeping the drilling fluid below 0℃ at all times during circulation. The heat exchanger is the core component of the drilling fluid cooling system. The paper selects plate heat exchanger as the heat exchange component to cool drilling fluid， and uses the average temperature difference method to determine the heat exchange area and basic parameters， then numerical simulation of the heat exchange performance of the plate heat exchanger is using COMSOL Multiphysics 6.0 software. The research results show that the heat exchanger can cool the drilling fluid to -4~-3℃. Further， the simulation results show that the outlet temperature of the drilling fluid decreases with the decrease of the carrier refrigerant injection temperature and the increase of the carrier refrigerant flow rate， the type of drilling fluid has a great influence on the heat transfer performance of the heat exchanger， while the material of the heat exchanger plate has little influence.

Key words:polar regions drilling;subglacical bedrock core drilling;drilling fluid;cooling system;plate heat exchanger