Comprehensive Model for Predicting Corrosion Rates in Gas Wells Containing CO2

Abstract

Summary A WINDOWS-based computer model has been developed which can help predict the location of corrosion and the life of a carbon steel tubular in a gas condensate well containing carbon dioxide. This model provides a physical description for the five different flow regimes that can occur in gas wells. This description has proven to be useful in the prediction of the corrosion rates of these wells. The model does not use the partial pressure of CO2 in the calculation of corrosion rate. It has been found that the hydrodynamics is the most important parameter in this type of corrosion. The model has an expert system associated with it which takes into account the volume fraction of condensate and water in the tubing. When the water level reaches and exceeds 50% of the total volume, the tubing is completely water-wet and the corrosion rate is a maximum. At the point where 30% or less of the volume of the fluid is water, the corrosion rate is believed to be zero. Caliper surveys have played a role in our ability to establish these points of transition within the model. Case histories have been presented which illustrate how the model can help in performing failure analysis and design of gas condensate wells.