Scale Formation Due to Water Injection in Malaysian Sandstone Cores

Problem statement: Scale deposition is one of the most serious oil field problems that inflict water injection systems primarily when two incompatible waters are involved. Approach: This study was conducted to investigate the permeability reduction caused by deposition of calcium, strontium and barium sulphates in sandstone cores from mixing of injected Malaysian sea waters (Angsi and Barton) and formation water that contained high concentration of calcium, barium and strontium ions at various temperatures (60-90°C) and differential pressures (125-175 psig). The solubility of common oil field scales formed and how their solubilities were affected by changes in salinity and temperatures (40-90°C) were also studied. The morphology and particle size of scaling crystals formed as shown by Scanning Electron Microscopy (SEM) were also presented. Results: The results showed that a large extent of permeability damage caused by calcium, strontium and barium sulphates that deposited on the rock pore surface. The rock permeability decline indicates the influence of the concentration of calcium, barium and strontium ions. Conclusion: At higher temperatures, the deposition of CaSO₄ and SrSO₄ scales increases and the deposition of BaSO₄ scale decreases since the solubilities of CaSO₄ and SrSO₄ scales decreases and the solubility of BaSO₄ increases with increasing temperature. The deposition of CaSO₄, SrSO₄ and BaSO₄ scales during flow of injection waters into porous media was shown by Scanning Electron Microscopy (SEM) micrographs.