A New, Alternative Weighting Material for Drilling Fluids

Abstract

Abstract Barite has been used to increase the density of drilling fluids (DF) since 1922. However, circumstances & needs are changing: The API has recently introduced a new standard for 4.10 sg barite in recognition of diminishing supplies of readily available barite that meet API’s standard minimum density specification of 4.20 sg - high quality barite is running out. The search for new hydrocarbon resources to replace reserves has resulted in more difficult drilling conditions & fluid requirements e.g. deepwater, ERD, HPHT etc., where ECD management, sag control & formation damage mitigation are critical to success. Alternative weighting materials (WM) such as manganese tetraoxide, treated micronized barite & cesium formate have been successfully used to handle many of the problems mentioned, but they are expensive & not produced in large volumes. Therefore, their application tends to be restricted. There is, therefore, a need for alternative weighting materials capable of providing better functionality than barite, but available in sufficient volumes to meet requirements & be competitively priced. This paper describes a new micronized, weighting agent, suitable for use in drilling & completion fluids, which offers significant advantages in the control of ECD, sag & formation damage. It is denser than barite, acid soluble, available in large volumes of > 100,000 tpa and is significantly cheaper than the current, high-end weighting materials. Test results are given showing stable fluids with low plastic viscosity, gel strengths & sag, even under HPHT conditions, for both aqueous & non-aqueous based fluids. The material has an excellent HSE profile & is soluble in oilfield acids. Accordingly, it provides a viable alternative product, intermediate between barite & the more expensive weighting materials.