The paper presents the results of a study of the properties of water-based drilling fluids with ethylene glycol and various polymer additives. The mass concentration of ethylene glycol varied from 0 to 80 %. Technical starch, xanthan biopolymer Duo-Vis (M-I Swaco, USA), Gammaxan (MIRRICO, Russia), cationic flocculant FLOPAMTM AN934 VHM (SNF, France) were considered as additives. Rheological and thermophysical characteristics of the considered drilling fluids and the process of clay swelling were investigated. It was shown that the addition of ethylene glycol leads to a significant decrease in the coefficient of thermal conductivity and heat capacity of the drilling fluid without a significant degradation in the rheological characteristics. Thus, at 65 % concentration of ethylene glycol in drilling fluid the thermal conductivity coefficient and heat capacity decrease by 70 % and 40 % respectively. It was found that ethylene glycol has a weak effect on the viscosity and rheological characteristics of drilling polymer fluids at concentrations below 65 wt%. The swelling of clay minerals is another important factor affecting the stability of the well walls in the process of drilling permafrost. Studies of clay swelling considered drilling fluids have shown that the addition of ethylene glycol leads to a significant inhibition of the swelling process. Addition of 50 wt% ethylene glycol is reduced the swelling ability almost three times in comparison with the base polymer drilling fluid. The possibility of controlling the thermophysical and hydration characteristics of drilling fluids by the introduction of ethylene glycol without degradation of their rheological properties has been shown. The data obtained will be useful in the development of drilling fluids for drilling in permafrost conditions.
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