Squeeze Deployed Sulfide Inhibitor Successfully Averts Challenging Sulfide Scale Deposition in Permian and Williston Unconventional Basins

Abstract

Abstract Sulfide scales (zinc, lead and iron sulfide) are currently causing considerable production challenges as mature fields are kept operational, and as deeper-hotter reservoirs are being developed. An effective way to combat conventional scaling is to inject "squeeze" scale inhibitors into the formation which are then lowly released as production resumes, providing scale protection. This option has not been the case for sulfide scales due to formation kinetics and lack of suitable products. In this study we present two field cases where new generation squeezable sulfide inhibitors were deployed with clear success in inhibiting sulfide deposition and establishing stable production. Also presented are the development methods and chemical synthesis details for the development of a squeezable product. A novel fast screening technique is detailed as well as a new type of residual monitoring method for the polymeric species that inhibit the sulfide scales. In the Permian Basin, newly completed long horizontal wells in the Sprayberry Formation were on a constant rotation of work overs (every 3 to 5 days) due to severe zinc and iron sulfide deposition. Early squeezes performed with known phosphonate/ester scale inhibitors, and end-capped polymer were unsuccessful. A new generation of squeezable sulfide inhibitor was deployed and stabilized production as well as the scaling ion data. A unique and fast residual analysis methodology (using a specialized HPLC column) was developed as part of the squeezable sulfide inhibitor development project capable of providing a unique selectivity in a high TDS brine without interferences increasing residual monitoring and squeeze confidence. In the Williston basin many fields are known for their troubled history with iron sulfide. To date, the preferred option has been continuous well cleanout that impacts production, next generation squeezable sulfide inhibitor was deployed and it successfully increased productivity and eliminated well clean outs for the trialed wells. This technology summarized in the paper offers a substantial step change in the ability to protect against sulfide scale via squeeze application. These field treatments show that next generation squeezable inhibitors were successful in inhibiting sulfide scales with no observed formation damage, upset to process facilities during flow back, or decline in productivity.