Abstract
The pH stabilization technique is a method for control of sweet corrosion in wet gas pipelines. The method is suited for systems with MEG for hydrate control as the pH stabilizer will remain in the lean MEG and do not need a continuous injection. Full pH stabilization is used when the risk for production of formation water is negligible as formation water will lead to calcium carbonate scaling. Partial pH stabilization combined with a film forming inhibitor may be an alternative when some formation water may be produced. This method has also been applied without MEG.
The biggest challenge with pH stabilization is the risk for scaling, and a reliable prediction of expected quantities of formation water is required. The design is normally more complex than traditional systems and the interaction with the MEG regeneration is essential.
Organic acids will accumulate over time and may lead to top-of-line corrosion.
Qualification in the laboratory in flow loops is highly recommended for both full and partial pH stabilization to identify type and concentrations of chemicals and to determine the required corrosion allowance. For full pH stabilization a back-up solution should be qualified in parallel with the base case.
There are several fields currently under operation with use of both techniques with no reported corrosion problems.
Follow-up during operation should be by regular chemical analyses of the rich MEG to determine the need for reclaiming and to verify that sufficient pH stabilizer is present. The iron ion concentration for such systems should normally be very low.
