含寄生管和中心管的套管隔热效果影响因素研究

在冻土层钻井过程中,冻土容易受到钻井液影响而融化.针对该问题,提出使用含寄生管和中心管的套管对冻土层隔热,并应用含寄生管和中心管的套管的隔热效果试验系统分析了影响该套管隔热效果的因素.试验发现,含寄生管和中心管的套管其中间部分可以有效抑制径向传热和轴向传热,使外壁温度稳定在低值,但是两侧接箍部分隔热性能较差,提高了其外...

Research of the Influencing Factors on Thermal Insulation Effect of Casing with Parasitic Pipes and Central Tubing

In the process of drilling in permafrost, the frozen soil is susceptible to melt under the influence of drilling fluid. To solve this problem, casing with parasitic pipes and central tubing was introduced to insulate the pipe from the permafrost. Then, a set of test system for the thermal insulation of casing with parasitic pipes and central tubing was designed to analyze its performance and influencing factors. The experiment reveals that the central part of the casing can effectively suppress heat transfer in the radial and axial direction and keep the outer wall at a low temperature. However, thermal insulation of the couplings on both sides are poor, which raise the outer wall temperature, resulting in a U-shape distribution of it. In addition, the sensitivity analysis and single-factor fitting of environmental and operational parameters indicate that the temperature rise from the environment and fluids will increase the outer wall temperature linearly, and the increase of drilling fluid displacement will reduce the outer wall temperature following a logarithmic relationship. From the coefficient of the multivariate fitting equation, it is clear that the most influential factor on outer casing wall temperature is the environmental temperature followed by cold fluid and hot fluid temperature. The research results show that using casing with parasitic pipes and central tubing to protect the permafrost is very feasible, and engineering technical measures such as lengthening the intermediate casing section, improving the coupling structure, maintaining low temperature and displacement of cold fluid can significantly improve the protective effect.