John L. Prybylinski, Petrolite Corp.
This paper gives quantitative calculations of the effects of Carbon Dioxide and pressure on the solubilities of formation minerals in a West Texas brine. Increased pressure makes anhydrite and gypsum significantly more soluble. The solubilities of carbonate minerals are increased to a lesser extent. The presence of Carbon Dioxide causes large increases in the solubilities of carbonate minerals, thus exacerbating the scale problem. Carbon Dioxide will greatly reduce the pH of injected or connate water, but this undesirable effect is reduced by the buffering action of carbonate minerals. Because of this buffering action, common mineral scale inhibitors can be used in CO, floods. Increased dosage may be required because of the potential for more scale.