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Scale Removal In A Deepwater Oil Production Well Using Fresh Water


 The aim of this paper is to present the results obtained by the use of fresh water in order to remove inorganic scale deposited inside production tubing from carbonate reservoir deepwater production wells with high salinity and low BS&W. The paper covers the entire process from the identification of production loss, the investigation of its main causes, treatment propositions and discussion of obtained results.
 One of the hypotheses regarding the scale deposition mechanism in the studied wells is that the precipitation of salts is due to the evaporation of produced water. This phenomenon occurs through the contact of water with dry gas applied in the artificial elevation method (gas lift). The proposed and tested scale removal procedure consists of a soaking of the production tubing with fresh water in order to dissolve the deposition or at least part of it that is soluble in water. Preventive care actions in relation to flow assurance were taken, since the suggested method uses a high volume of fresh water, increasing the hydrate risks.
 Scaling in wells with those characteristics was systematically removed through remote acidification (with specialized vessel assistance). That approach has shown to be always effective. On the other hand, remote acidification was always costly and dependent on the availability of critical resources. The technique depicted in this paper requires neither a vessel nor acid and, therefore, incurs significantly lower costs. The results obtained in the first tests were substantially positive since the wells’ productivity was fully restored. In this sense, the hypothesis of water solubility of the scale deposition was confirmed, and the method validated.
 Since its validation, the method has been applied a number of times, confirming its repeatability, and extending its use to other wells with similar scaling occurrences, reducing costs and restoring the production in a short time. Nevertheless, new challenges arise in relation to the full comprehension of the deposited material and the prevention of its deposition.