Abstract

In this study, the usage of class F fly ash (brown coal) and class C fly ash (lignite) with increasing concentration in water based mud mainly composed of bentonite dispersion was investigated at ambient conditions. Experimental results indicate that efficiency of the mud is significantly controlled by type of the fly ash tested and its concentrations. The results show that Class F fly ash enhanced filtration properties (filtrate loss and mud cake) of the mud and have no effect on the rheology including, yield point, viscosity whereas the class C fly ash increased the rheology parameters and degraded water loss into the formation and filer cake thickness dramatically. This study showed that class F fly ash displays superior performance than class C fly ash. Through this study, it was reveal that class F fly ash is a promising additive to improve the filtration characteristics of bentonite based drilling fluids, thereby contributing to reducing formation damage caused by drilling mud.