Clay-free biodiesel-based drilling fluid suitable for high temperature

Abstract

This paper introduces the formation of a clay-free biodiesel-based drilling fluid system. The system uses the biodiesel derived from the transesterification between soybean oil and methanol as the continuous phase, which is environmentally friendly and has an appropriate flow state. In order to inhibit the hydrolysis of the base oil under high temperatures, a small amount of methanol is retained and Lime addition is minimized. Besides, the system also contains a special polyamine-typed rheological modifier instead of organoclay to provide a fragile gel-structure with lower plastic viscosity and higher yield point, thus good for hole cleaning and solid suspension while keeping a higher rate of penetration (ROP). In order to strengthen the plugging and fluid loss control abilities, superfine calcium carbonate and oxidized asphalt are added and obtain a good outcome. Evaluation results showed that the clay-free biodiesel-based drilling fluid exhibits good properties of rheology, filtration, and emulsion stability, with temperature resistance over 200°C, which is suitable for the exploration of unconventional oil/gas restores.