The pH-stabilisation method is a cost effective, reliable and environmental friendly way to control corrosion in gas/condensate pipelines where glycol is used as hydrate preventer. Increasing the pH to 6.5-7.5 facilitates the formation of a protective iron carbonate film on the steel surface and reduces corrosion of the steel.
The carry-over of formation water puts limits on the use of the pH stabilisation technique as carbonate scale may form. Scale formation in glycol carrying pipelines is not easy to predict, as solubility data for CO2 and scale forming compounds in glycol solutions are very scarce. Glycol affects scale formation by changing the solubility and the precipitation kinetics, and the solubility of for instance calcium carbonate is markedly reduced.
The paper reviews the experience from the fields that have been pH stabilised and discuss the various pH-stabilisation methods that have been used. The paper gives data on the application limits with respect to formation water and discuss operational problems, challenges and solution related to the risk for scaling downstream the lean MEG injection point, in heat exchangers and in the MEG regeneration and reclamation systems.