The following brines, a 11.0 lbm/gal (1.32 g/cm3) NaCl/NaBr, 13.5 lbm/gal (1.62 g/cm3) CaCl2/CaBr2 and 16.0 lbm/gal (1.92 g/cm3) CaCl2/CaBr2/ZnBr2 were studied for carbonate precipitation and scaling tendencies in the presence of CO2 gas. The brines were subjected to CO2 gas pressures ranging from 50 to 500 psi (0.34 to 3.45 MPa) and temperatures between 200 to 400°F (93.3 to 204°C).

The 11.0 lbm/gal (1.32 g/cm3) NaCl/NaBr and 13.5 lbm/gal (1.62 g/cm3) CaCl2/CaBr2 brines formed small amounts of carbonate solids upon exposure to CO2 gas. The 16.0 lbm/gal (1.92 g/cm3) CaCl2/CaBr2/ZnBr2 brine in contact with CO2 gas produced significantly large amounts of carbonate solids. The concentration of precipitated carbonates formed by the 16.0 lbm/gal (1.92 g/cm3) CaCl2/CaBr2/ZnBr2 brine would raise concerns of possible formation damage.

Two commercial scale inhibitors were evaluated and were found to provide very little to no protection towards inhibition of carbonate solids formation.

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