Research on active cooling technology of measuring instrument while drilling based on insulation tube in high temperature well

Abstract

Measurement while drilling (MWD) for high temperature well has always been a worldwide problem. So far, no effective active cooling method has been applied to MWD. In this paper, a new active cooling method based on insulated pipe is proposed. Three calculation models: theoretical model, numerical model - segmentation and numerical model - overall are established. In the theoretical model, a one-dimensional heat transfer control model is established, taking the fluid inside the insulated tube as the research object and considering the thermal resistance of the insulated tube and the heat entering the fluid through the tube wall. By iterating the boundary conditions of numerical model-segmentation, the heat transfer problem of insulated pipes with a length to diameter ratio exceeding 1000 is solved. By copying, translating, and stitching finite length meshes, the overall grid model of numerical model - overall is achieved. The calculation results of the three models mutually verify their reliability. The research results indicate that external cold fluid technology can be used for active cooling underground when the cold fluid is water. The mass flow rate of cold fluid and the heating time are the key factors affecting the temperature of cold fluid reaching the bottom hole. The cooling effect can be significantly improved by reducing the injection temperature of cold fluid and increasing cold fluid flow rate.

Keywords

• Insulated pipe
• Active cooling
• Measurement while drilling
• High temperature
• External cold fluid technology