REDUCTION IN ANNULAR PRESSURE LOSS BY MUD RHEOLOGY CONTROL- A MEANS OF MUD PUMP PRESSURE OPTIMIZATION, A CASE STUDY OF A NIGER DELTA WELL

This paper proposes two linear mathematical models for the reduction of annular pressure loss in a Niger Delta well- X, so that mud pump pressure is optimized. Data related to mud rheology, mud pump pressure, drill cuttings and the well geometry is available for well X which has already been drilled. The first linear model involves the reduction in pressure drop in the drill collar-casing annulus and the second linear model involves the reduction in pressure drop in the drill pipe-casing annulus. These models express reduced or critical annular pressure drops in terms of two mud rheological parameters- the yield point and plastic viscosity. For combined annular drill collar and drill pipe pressure loss, this paper proposes that the two linear mathematical models can be solved simultaneously to obtain optimum yield point and plastic viscosity of the drilling mud system to be employed for hole cleaning in the combined drill collar-casing and drill pipe-casing annulus. The Herschel-Bulkley model is employed as the rheological model that represents the properties of the drilling mud system analyzed and is generated for eight rheological cases each of the drill collar and drill pipe annular hole cleaning as well as two cases of the combined drill collar and drill pipe annular hole cleaning.