This paper assesses the benefits of itabirite (hematite) as a weighting material in heavy oil base systems. A laboratory investigation was conducted to obtain information on a comparative basis between barite and itabirite. Rheological properties and abrasiveness were studied and field results were predicted.
As a result of the lab studies, lower field rhe-ology (i.e., PV, YP and Gel Strength) and a slightly more abrasive nature are predicted. Increased penetration rates and improved bit hydraulics are expected. Increased penetration rates and a greater tolerance to drill solids should reduce overall mud cost and well cost.
Upon completion of the laboratory study, field tests were made in a development area. Offset information on wells drilled with barite was studied, and variables such as drilling rigs, mud company, solids control equipment, bits, and mud programming were kept as consistent as possible with the exception of itabirite as the mud weighting agent.
Results indicate an increase in penetration rates as compared to offset wells, especially in mud weights exceeding 15 lbs/gal. Plastic viscosity was lower as predicted, mud cost slightly decreased, and abrasion did not appear excessive on pump liners and and pump parts. The efficiency of the solids control equipment was increased as shown by the maintenance of a lower percentage of solids in the mud and reduction of the percentage of low gravity solids.