pH Measurements in Aqueous CO₂ Solutions Under High Pressure and Temperature^✫ Available to Purchase

In order to determine the acidity of corrosive media prevailing in oil and gas wells where CO₂ corrosion is encountered, a pH meter has been built which enables pH measurements under pressures from 0.1 up to 100 MPa. The usual physical chemistry of calcocarbonic equilibria is also presented in a new form which better emphasizes the influence of the partial pressure of CO₂ as the controlling variable in the system. According to both theoretical and experimental results, the pH of a production water depends as much upon its alkalinity as upon the level of the CO₂ partial pressure. The effect of calcareous saturation or supersaturation is also emphasized. It is then shown through a survey of production waters that their acidity under well conditions is much weaker than is commonly assumed. This stands for both CO₂ corrosion and sulfide stress cracking.