Improvement in the Performance of Potato Starch Used in the Water-Based Drilling Fluid via Its Chemical Modification by Grafting Copolymerization

Increasing the thermal stability and resistance to bacterial attack (bioresistance) of the potato starch used in the water-based drilling fluid is the aim of this work. Four types of potato starch grafted with acrylamide and a mixture of each one with acrylic acid, 2-acrylamido-2-methyl-1-propane sulfuric acid and itaconic acid were synthesized by manganese (IV)-induced redox system at the suitable concentrations of initiator and monomer(s). FTIR spectroscopy was used to verify the grafting of monomers onto the starch. The effect of grafted starches on the rheological and fluid loss properties before and after aging of the water-based drilling fluid prepared with fresh water, 4% saline and the South applied method were investigated. The results showed that temperature and aging of fluid enhance the rheological and fluid loss control properties of water-based drilling fluids prepared in the presence of grafted starches. In other words, grafted starches are stable against thermal degradation and can be used in the formulation of water-based drilling fluids for drilling of deep wells.