Rheological Properties of Terminalia Mantaly Exudate as Drilling Mud Additive

Abstract

Polymers are known for controlling fluid loss and modifying rheology in drilling muds through polymer chain entanglement and polymer-solvent interactions. Natural polymers have been used in the formulation of drilling muds, mainly due to their high molecular weight and eco-friendliness but they have limitations in controlling fluid loss, modifying viscosity or forming good gel strength in saline and thermal environments. This study reports laboratory evaluation of Terminalia mantaly exudates as viscosifier in drilling mud formulations. The effects of polymer concentrations, temperature, pH and salinity on the rheological properties of this novel biopolymer were investigated. Results obtained show that as polymer concentration increases (0.5% – 2.5%w/v), the rheological properties (apparent viscosity, plastic viscosity and yield point) of the biopolymer increased. At the polymer concentrations investigated, an increase in temperature (80°F-150°F) results in a slight decrease in the rheological properties of the polymer. At 2%w/v polymer concentration, an increase in salinity results in a slight decrease in its rheological properties, while at 1.5%w/v polymer concentration, an increase in pH (4-10) shows no significant change in the rheological properties. The shear stress increases with increase in shear rate and obeys the Bingham plastic model. The results obtained show that the polymer has a good alkaline resistance at pH above 7 and stable rheological properties at increased salinity and temperature. This has been attributed to the stable repulsive forces of the negatively charged polyelectrolyte of the polymer as salinity increases. From the results obtained in this study, Terminalia mantaly exudate can be a substitute for conventional natural polymers in water-based drilling muds.