Scale dissolver application: Production enhancement and formation-damage potential

Sulfate scale dissolvers have been applied downhole for many years to remov e barium and mixed sulfate scale deposits from the wellbore and from the ne ar-wellbore formation. As well as dissolving mineral scales, these corrosiv e materials also have the potential to cause some degree of formation damag e by the dissolution of reservoir minerals. In this study, three commercial scale dissolver formulations and two laboratory prepared amino carboxylic acid dissolvers (EDTA and DTPA) were tested to assess their comparative cap acity to dissolve barium sulfate and, of more importance in the current stu dy, their potential to cause damage in the near-wellbore formation. The pot ential formation damage capacity of various scale dissolvers has been asses sed by measuring the levels of cation release in static tests on mineral se parates and by studying the various effluent profiles from core floods usin g reservoir sand. Possible damage mechanisms include silicate dissolution, fines generation/migration, mechanical strength reduction and wettability c hanges. We conclude that, when testing sulfate scale dissolvers for field a pplication, their formation damage potential should be assessed as well as their barite dissolution performance.