An Amphiphilic Flow Pattern Regulator for Oil-Based Drilling Fluids Used in Ultra-High Temperature Deep Wells

In deep and ultra-deep well drilling, after long period of circulation at ultra-high temperatures, oil-based drilling fluids will experience rheology deterioration problems, such as gel or suspending capacity decline, a causative factor for barite sag, stuck pipe and wellbore collapse etc. To deal with this problem, an ultra-high temperature amphiphilic oligomer flow pattern modifier was developed through high temperature amidation reaction with raw materials such as tall oil fatty acids, fatty alkyl polyamines and maleic anhydride. Laboratory experiments were conducted to carefully investigate the performance and mechanisms of the oligomer flow pattern modifier, and the experimental results show that the oligomer flow pattern modifier can be used to significantly improve the rheology and settling stability of oil-based drilling fluids. At 230 ℃, 0.5% oligomer flow pattern modifier can increase the yield value of a water-in-oil emulsion from 0.5 Pa to 4.5 Pa, and the emulsion stability voltage from 323 V to 509 V. It can increase the yield value of an oil-based drilling fluid from 6.5 Pa to 22.5 Pa, and the emulsion stability voltage from 1,014 V to 1,315 V. A mud sample was taken from a well, it was first hot rolled for 1 d, and then allowed for standing for 5 d. The mud sample was then treated with the oligomer flow pattern modifier, and it still acquired good gel strengths, settling stability and emulsion stability. This oligomer flow pattern modifier provides a technical reference for the development of ultra-high temperature oil-based drilling fluid.