Key Technology of 240°C High-Temperature Drilling Fluid

Abstract

Hot dry rock (HDR) is a renewable green and clean energy source from the depths of the earth. It has the characteristics of high efficiency, environmental protection, safety, and stability, and is not restricted by seasons and climates. Difficulties in exploration and development include deep burial, formation fragmentation, abnormal pressure, high well temperature gradient, and high hole bottom temperature (usually >200°C), key technical issues such as sticking. This paper analyzes the difficulties of high-temperature resistant drilling fluid in dry hot rock: temperature resistance of treatment agents and systems, foaming, leakage, wellbore instability, and other problems. The optimization and experiment of treatment agents such as loss reducers, high-temperature protective agents, etc., and research on drilling fluid technology resistant to high temperature of 240°C in hot dry rock drilling has been carried out, through the optimization experiment of pulping materials and high temperature treatment agent. The main formula is: 3%-4% Sodium bentonite + 2%-3% HPS + 3%-4% SPNH + 2%-4% GJA + 3%-4% JSJ-1 + 0.5%-1.0% GGDP + 1% GBHJ. The drilling fluid formula has good rheology after hot rolling at 240°C, API filtrate loss<5ml, the viscosity recovery rate is over 90%. It provides effective technical support guarantee for promoting the exploration and development of hot dry rock resources in China.