Estimating CO2 degassing effect on CaCO3 precipitation under oil well conditions

Abstract

To act effectively in the prevention of calcium carbonate precipitation, it is necessary to know the contribution of each causing factor. Many thermodynamic models, including the codes of scale software, just predict the total amount of CaCO3 precipitated. A study was developed to model the two major causing factors of calcite precipitation when the fluids experience a pressure drop. The effects of depressurization were investigated, first on calcite precipitation thermodynamics and second on CO2 degassing thermodynamics. It has been found that CO2 outgassing produces an expressive amount of scale, contributing from 60% to 90% on total calcite precipitation under the investigated conditions. That is, considering these results, it may be more efficient to work to keep CO2 in solution than to try to avoid the calcium carbonate nucleation.