Research Progress and Prospect of Cooling Technology for Drilling Fluid in Deep and Ultra-Deep Wells

With the layout and development of deep ultra-deep wells in major oilfields at home and abroad, the problem of high temperatures at the bottom of wells has become more and more prominent, which poses a serious challenge to drilling fluids. To guarantee the stability and reliability of drilling fluids at high temperatures, scholars at home and abroad have studied a series of drilling fluids cooling methods (natural cooling, forced cooling, and the selection of low-thermal-conductivity drilling tools, etc.) to regulate the temperature of the drilling fluids, so as to realize the resistance of drilling fluids at high temperatures. This paper briefly outlines the effects of high downhole temperature on drilling fluids and drilling tools in deep ultra-deep wells, clarifies the heat transfer mechanism between drilling fluids and formations, and systematically describes the current status of domestic and foreign drilling fluid cooling technology in deep ultra-deep wells in terms of controlling the temperature of drilling tools on the ground and downhole, optimizing the parameters of drilling fluids to control the temperature and controlling the temperature of drilling fluid cooling materials, analyzes the problems of the current technology of cooling drilling fluids, and looks ahead to the development of low-cost, low-temperature, and high-efficiency technologies to control the temperature of drilling fluid. The technology should be developed with low cost, high efficiency, and intelligence to precisely control drilling fluid temperature and provide strong support for safe, fast, and economical drilling of deep and ultra-deep wells.