Influence and Mechanism for the Particle Size of Weighting Material on the Rheological Properties of High-Density Drilling Fluids

As a washing medium, the drilling fluid is used to clean the hole in the process of drilling. Weighting material such as barite, iron-ore fines used for the preparation of high-density water based drilling fluid because of its high density and well wettability. However, the rheological performance is distinctly of vary types, sizes weighting materials for high-density drilling fluid. For controlling and maintenance of the rheological properties of high-density drilling fluid system, adding barite and iron-ore powder with different particle size into water based drilling fluids increasing the material density to 2.30g/cm3, obtained the viscosity effect which is defined as the variation of apparent viscosity after the drilling fluid rolling 24hours at high temperature (180°C), then analysis of its mechanism of action. The results show that, it is easy to forming strong particles as the core of the rules of the tentacles spherical structure with 250-350 mesh iron-ore powder to weight the water based drilling fluid, which could keep the stable rheological properties and make the size of solid particles integrated with the drilling fluid system closely not only holding the minimum viscosity effect also maintaining the best sedimentation stability. Similarly, 200-250 mesh barite perform the appropriate viscosity of water based drilling fluid and maintain a good sedimentation stability, and the maximum value viscosity effect is adding the 325 mesh barite.