Effect of temperature and calcium ion concentration on permeability reduction due to composite barium and calcium sulfate precipitation in porous media

In the oil industry, water injection is used as a secondary recovery technique for pressure maintenance and efficient oil and gas production. Injected water may be incompatible with water that occurs naturally within the pores of reservoir rock. When these two incompatible waters mix, inorganic scales precipitate within porous media. Many studies have been conducted to investigate the effect of scale formation on the ability of reservoir rock to transmit fluids. Most of these studies have focused on single salt precipitation. This paper is intended to investigate the permeability reduction of porous media due to composite BaSO4-CaSO4 precipitation. Since pure BaSO4 scaling tendency decreases with increasing temperature, while pure CaSO4 scale formation potential increases with increasing temperature, the effect of temperature on the co-precipitation of BaSO4 and CaSO4 was questionable. This paper presents the results of an experimental study which performed by injection of two incompatible solutions into the pack of glass beads at temperatures of 50 and 70 °C to exhibit the effect of temperature on the composite BaSO4-CaSO4 scaling potential. The experimental results and Scanning Electron Microscopy images indicated that even minute amounts of calcium ions combined with barium ions clearly affected the scale nature, morphology, particle size and intensity of scale formation.