Estimation of the Combined Effect of Temperature and Carbon Dioxide Pressure on Dissolved Calcium Carbonate Concentration in Oilfield Brines

Abstract

Calcium carbonate, or calcite, scale is frequently encountered in oilfield operations. In a reservoir, when brine is produced, it is disturbed because the brine is moved to lower temperature and pressure areas. The dissolved concentration of calcium carbonate is greatly influenced by temperature and the partial pressure of carbon dioxide gas over the water. The net result of a drop in temperature and pressure may therefore be an increase or a decrease in the calcium carbonate saturation ratio as determined by the temperature change relative to the pressure change. In this article, a simple Arrhenius-type function is developed to estimate the combined effect of temperature and carbon dioxide pressure on calcium carbonate dissolved concentration in oilfield brines. Estimations are found to be in excellent agreement with reported data in the literature with average absolute deviation being less than 2%. The tool developed in this study can be of immense practical value for engineers to have a quick check of combined effect of temperature and carbon dioxide pressure on calcium carbonate dissolved concentration at various conditions without opting for any field or experimental trials. In particular, engineers would find the approach to be user friendly with transparent calculations involving no complex expressions.

Keywords:

• Calcium carbonate
• carbon dioxide
• partial pressure
• predictive tool
• scale formation
• Vandermonde matrix