Abstract: Scale formation is one of the most serious oil field problems that inflict water injection systems primarily when
two incompatible waters are involved. Two waters are incompatible if they interact chemically and precipitate minerals
when mixed. Due to the lack of reaction kinetics data, the rate of barium sulphate deposition in porous rock was measured
through flooding sandstone core samples of uniform properties with supersaturated brine. The brine was formulated at the
core inlet by mixing of injected sea water and formation water that contained high concentration of barium ion at various
temperatures (50 - 80°C) and differential pressures (100 - 200 psig). The rate of BaSO4 scale formation was estimated by
monitoring the core effluent’s barium ion concentration. The solubility of barium sulphate scale formed and how its solubility
was affected by changes in salinity and temperatures (40 - 90°C) were also studied. Scanning Electron Microscopy
analysis was also used to examine the nature of scale deposition throughout the core. The results indicated increased rate
of BaSO4 precipitation at higher temperatures and greater brine super-saturation. The results were utilized to build a general
reaction rate equation to predict BaSO4 deposition in sandstone cores for a given temperature, brine super-saturation and
differential pressures.