Abstract
Oil-based drilling fluids (OBM) are emulsion based fluids where water droplets are dispersed in the oil phase. In some occasions weight material particles sag out at the field. For example, this may happen when the circulation rate has to be low because of running a managed pressure operation; thus hindering sufficient shearing of the fluid to ensure proper drilling fluid quality. Similarly, shearing of premixes at the drilling fluid plant does not provide good enough emulsion quality. In such cases, both at the drilling operation and at the drilling fluid plant, use of a shear gun is necessary. In the article it is shown how a dual jet shear gun provides proper shearing in an offshore drilling operation offshore Norway making drilling possible. Furthermore, it is shown how shearing with an equal dual jet shear gun on a premix at a mud plant provides a better emulsion stability, indicating smaller water droplets as the electric stability increased significantly with shear. This happens even though there is insignificant change in the rheological flow curve. These effects are discussed in detail in the article and a possible explanation for the effects are suggested. The discussion culminates by presenting a reason why avoiding barite sag is dependent on proper shearing.