A new and simple, "standardized" method was developed in order to rank efficiency of various scale dissolvers. Five different scale dissolver products were compared for performance at Heidrun related conditions with regards to their dissolving capacity and dissolution rate/kinetics (initial speed performance) on genuine field scale samples from well A-28, Heidrun.

The overall treatment and shut-in time might be considered an important factor in remediation procedures. By comparing the performance curves of the dissolvers, the product giving the highest initial dissolution kinetics could be chosen. Moreover, there are other factors that also will influence the choice of the best-suited product, like dissolution rate of contaminated field scale, cleaning procedures, environmental rating, and total dissolution capacity.

The effects of oil contamination and cleaning procedures, involving mutual solvent or surfactants, were studied. The different products varied in active cleansing power and in sensitivity for available "active" surface area, as they will contain more or less surface-active co-agents.

In complex scale compositions, typical to most field situations, the dissolution of one particular scale species could be rate limiting to the overall process. Temperature and concentration effects could also be investigated in this set up.

By implementing this new ranking method, three chemicals were given a technical qualification for use at Heidrun. So far two of the products have been field-tested. The test procedure and a comparison to the field performance in the Heidrun cases, will be presented.

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