Scale Dissolver Application: Production Enhancement and Formation-Damage Potential

Abstract

Summary Sulfate scale dissolvers have been applied downhole for many years to remove barium and mixed sulfate scale deposits from the wellbore and from the near-wellbore formation. As well as dissolving mineral scales, these corrosive materials also have the potential to cause some degree of formation damage by the dissolution of reservoir minerals. In this study, three commercial scale dissolver formulations and two laboratory prepared amino car-boxylic acid dissolvers (EDTA and DTPA) were tested to assess their comparative capacity to dissolve barium sulfate and, of more importance in the current study, their potential to cause damage in the near-wellbore formation. The potential formation damage capacity of various scale dissolvers has been assessed by measuring the levels of cation release in static tests on mineral separates and by studying the various effluent profiles from core floods using reservoir sand. Possible damage mechanisms include silicate dissolution, fines generation/migration, mechanical strength reduction and wettability changes. We conclude that, when testing sulfate scale dissolvers for field application, their formation damage potential should be assessed as well as their barite dissolution performance.