A Unique Technical Solution to Barite Sag in Drilling Fluids

Abstract

Many attempts have been undertaken to reduce the extent of barite sag both in the field and in the laboratory. This paper describes a unique approach to tackling the problem of barite sag using polymer-coated, ultra-fine barite. The technology uses a polymer coating that enables effective dispersion of the particles in either a waterbased or oil-based drilling fluid. This offers a number of fluid performance benefits, including superior sag performance over conventional drilling fluids without compromising the desired rheological properties of the fluid. The particle-size range of the weighting agent provides the sag performance benefits without significantly “hiking” rheology, as would normally be expected from the large surface area of particles introduced to the drilling fluid. This unique behaviour is due to the special polymer coating used in the milling process, which diminishes the particle-particle frictional forces, thus maintaining the relatively low rheological properties of the drilling fluid. This paper discusses how the technology can be used to provide an effective solution to the potential barite sag problems faced in drilling high-angle, extended reach and HTHP wells.