Erodability of Partially Dehydrated Gelled Drilling Fluid and Filter Cake

Abstract

ABSTRACT Partially dehydrated-gelled drilling fluid and filter cake must be displaced from the wellbore annulus to achieve a successful primary cement job. A term ‘Erodability of drilling fluid’ is defined in this paper and was calculated from measured parameters in a large-scale test model. Differential pressures were measured in the annular space between the casing and a man-made, permeable formation and also inside the casing. Three different drilling fluids used in typical field operations were tested. Each drilling fluid was tested over a period of four days. Experimental data on erodability of drilling fluid filter cake is presented as a function of time, flow rate, and aging. A mechanism is proposed for the erosion of partially dehydrated-gelled drilling fluid and filter cake. Recommendations are given to improve the removal of partially dehydrated-gelled drilling fluid and filter cake and thus achieve a successful primary cement job in field operations.