Investigation of Local Weighting Materials as a Substitute To Barite In Drilling Mud Formulation

Abstract

Weighting materials are important components needed to increase the density of drilling mud in order to provide enough hydrostatic pressure to balance abnormalpore pressures. In Nigeria, millions of dollars are spent annually in importing barite to serve this purpose. However, there exists large reserves of weighting materials such as barite, hematite, dolomite, calcite, ilmenite in Nigeria hence the need to investigate the suitability of these materials as substitute for imported barite.Samples of barite, haematite, dolomite and calcite were obtained from three geographical locations in Nigeria and pulverized to 3.9µm using the 4-R Pendulum pulverizer. The physicochemical properties of the samples were determined. Mud samples of 10-20ppg were formulated with the weighting materials and the respective rheological and filtration properties were determined using API rheometer and Filter press respectively. A 2³ factorial designwas used to obtain optimum combination for the drilling mud slurry.The performance of local weighting materials have been compared to imported barite and the results showed that for a given mud density, Azara barite has the lowest plastic viscosity while Ikpeshi calcite has the same yield point as the imported barite. However, Itakpehaematite produced the thinnest mud cake while at lower mud density; Azara barite produced same mud cake thickness as the imported barite. The local materials utilized in this study can be used as weighting materials with appropriate beneficiation.