The effect of surface wettability on calcium carbonate precipitation in packed beds

• The solid surface chemistry played significant role on the formed CaCO 3 polymorph. • In the absence of oil, precipitation was favored in hydrophilic beds. • In the presence of oil, precipitation was favored in hydrophobic beds. • In the presence of organic phase, the mass of calcium carbonate precipitated was lower • Fractional wettability determines solutions flow and precipitation process. Multiphase flow processes taking place in Carbon Capture Utilization and Storage (CCUS) processes are accompanied by scale deposits which increase operational cost and reduce efficiency of processes. Over the years, the effect of several parameters, including pH, temperature, initial supersaturation ratio, (SR i ), with respect to calcium carbonate phase, the presence of foreign substances and solid substrates etc. on the prevalent mechanisms of scale, was investigated. Scale formation from fluids is in principle heterogeneous and may be affected by surface wettability. In the present work, for the first time, calcium carbonate precipitation was investigated in beds, packed with hydrophilic and hydrophobic of 1.5 mm diameter sphere at SR i values equal to 537, 222 and 86. Homogeneously hydrophobic and hydrophilic, and fractionally wet beds were tested. Solutions supersaturated with respect to calcium carbonate in the absence and in the presence of n-dodecane were injected into the columns. Except for solutions with SR i =537, with respect to calcite, where spontaneous precipitation prevailed, in the absence of n-dodecane, precipitation rates and the total mass of calcium carbonate precipitate, for the same time, were lower in the case of hydrophobic beds. In the presence of oil-water interfaces, for similar SR i values, hydrophobicity resulted in higher total mass of calcium carbonate precipitate, in comparison with the respective precipitated in the hydrophilic beds. Fractional wettability affected fluid flow and the precipitation process. In the absence of n-dodecane, the total calcium at the outflow curve lied in between the corresponding curves of the hydrophobic and the hydrophilic beds. In the presence of oil-water interfaces, fractional wettability resulted in the formation of shells consisting of small calcite crystals surrounding the hydrophobic spheres, while larger crystals were formed on the hydrophilic spheres. This study reveals the importance of pore surface wettability, its homogeneity and distribution on the formation of calcium carbonate scale during the flow of supersaturated solutions with respect to calcite and in the presence of oil/water interfaces created after oil displacement. “Differences of calcium carbonate crystallite deposits between water wet and oil wet substrates”