One-Step Calcium Sulfate Scale Removal Technique Provides Cost-Effective Remedial Treatment

Removal of calcium sulfate scale from wells is presently accomplished by several methods including scraping and chemical treatments. The most widely used chemical methods employ either: 1) a time-consuming and moderately expensive two-step conversion/ acid dissolution process or 2) a very slow reacting and expensive, alkaline chelating agent treatment. In an effort to lower the overall scale removal treatment cost and circumvent the objectionable qualities of the commercially available chemical treatments, a one-step calcium sulfate scale removal technique has been developed and successfully used in over 100 wells. This remedial technique has been employed to increase injectivity in injection wells, increase production in producing wells, and open up perforations to permit more efficient primary stimulation or remedial treatment of producing zones. Treatment costs range from $2000 to $5000, depending on whether or not additional primary stimulation or remedial treatment fluids are to be incorporated with the calcium sulfate scale removal fluid. Post-treatment production increases have ranged from 50% to 10 fold and treatment payout has typically required 30-45 days of post-treatment production.