Based on the literature database and information from pipeline companies, the methodologies used to select inhibitors were critically reviewed. Round robin tests were carried out in three laboratories to assess reproducibility of the wheel test. In total, twelve (12) laboratory methodologies were evaluated.
Field monitoring was carried out in Alberta at three fields — oily gas, gassy oil and oil transmitting — to support the laboratory evaluation, and to define the conditions under which specific laboratory methodologies can be used with the confidence that the laboratory data will predict field performance. Based on a quantitative comparison of field and laboratory general corrosion rates, pitting rates, and percentage inhibition (calculated from general corrosion rates and pitting rates) under three (3) different field conditions using four (4) continuous and two (2) batch inhibitors, the rotating cage, was ranked as the top methodology. In addition, this methodology is inexpensive and relatively simple to carry out.
The rotating cage is recommended as a methodology to be standardized for evaluating and qualifying inhibitors for sour service.