The rheological performance of fly ash in inhibitive water-based drilling fluids

Abstract

Water-based drilling fluids are the most widely used systems in drilling operations and contain a different type of additive to achieve desired rheological and filtration properties. In this study, an experimental investigation was carried out according to API standards to examine the impact of the various concentration (1.0 wt.%, 3.0 wt.% and 5.0 wt.%) of two types of fly ash (Class F, Class C), which fly ash is a industrial waste product that is obtained after the combustion of coal in thermal power plants, on the gypsum/polymer water-based drilling fluid rheological and filtration properties including apparent viscosity, plastic viscosity, yield point, gel strength, fluid loss, mud cake thickness at room temperature. The results showed that the rheological properties, as well as filtration properties of the drilling fluid, were improved by adding the fly ash that is Class F into the drilling fluid. Adding 3.0 wt.% Class F fly ash (brown coal) increased the apparent viscosity, plastic viscosity, yield point and gel strength by 23 %, 28%, 9 % and 25%, respectively while adding the Class C fly ash (lignite) at the same concentration increased the apparent viscosity, plastic viscosity and gel strength by 12%, 21% and 25%, respectively. Filtration test indicated the fluid loss volume decreased by 23% and mud cake thickness also decreased by 75% with addition of 3 wt.% concentration of Class F type fly ash, whereas adding Class C type of fly ash at same concentration resulted in a decrease in fluid loss by 10% and a increase in mud cake thickness by 150%. Therefore, it can be concluded that the type of Class F fly ash can help in preventing or mitigating several problems that could encounter during a drilling operation. © 2019, Pet Coal.