Empirical prediction of carbon-steel degradation rates on an offshore oil and gas facility: predicting CO2 erosion-corrosion pipeline failures before they occur

Various sections of carbon steel pipework removed from an offshore facility were found to have experienced severe degradation, partly attributed to an insufficient inhibitor dose rate, as discussed in a previous case study (Hu et al., 2011b). An investigation was conducted to compare the predictive capability of an empirical model generated using data from submerged impinging jet laboratory apparatus. The model was assessed in its ability to determine the rate of thickness loss for carbon steel pipework subjected to a CO2-containing erosion-corrosion environment, reviewing to what extent the prediction agrees with inspection data. The investigation considers whether the developed tool could have predicted pipework failures on the facility, comparing it to the degradation rate calculated from a leak which occurred within the past 2 years. The program of experiments set out to create a means of prediction using the material loss data from submerged impinging jet tests over a range of conditions replicating those within the line. Information pertaining to the temperature, production rate and sand loading was collated for the offshore facility. This data was used along with mass loss results to predict the degradation rate on the asset as a function of time over a 5 year period. This in turn was used to predict the total thickness loss of the pipework wall as a function of time. Consideration was also given to the current use of inhibition (10 ppm Inhibitor A) as well as the predicted thickness losses as a function of time had a candidate inhibitor been used instead (50 ppm Inhibitor B). Limitations of the model are presented, along with suggestions for ways to develop the model further.