Snorre In-Depth Water Diversion Using Sodium Silicate - Single Well Injection Pilot

Abstract

Abstract In-depth water diversion has been evaluated as a measure for increased oil recovery at the Snorre field, offshore Norway. The waterflood sweep efficiency can be potentially increased by in-depth placement of a blocking agent. From a comprehensive qualification program presented in a previous work (SPE 143836) in-depth formation plugging was demonstrated in realistic core flood experiment using sodium silicate. This paper highlights key results obtained from a single well pilot injection of sodium silicate in an offshore well at the Snorre field at NCS. The injection pilot was carried out successfully in June 2011 with the goal to confirm the ability of generating an in-depth permeability restriction approximately 40 m away from the wellbore. Fluids mixing and injection were performed from a vessel linked up to the platform in order to minimize the operational interference with the ongoing work on the platform. The chosen pilot design was aimed to (a) soften the formation water by a KCl preflush, (b) control the gelation kinetics using HCl acid mixed into the diluted silicate solution, and (c) displace the silicate solution by a KCl postflush. The in-depth permeability reduction was interpreted from injectivity measurements and from repeated pressure falloff-tests before and after the sodium silicate injection. The quality of the response measurement data was very good, and the in-depth permeability reduction was demonstrated with kinetics similar to predictions derived from laboratory experiments. The size of spacer slug applied in front of the sodium silicate was, however, on the low side. A larger spacer slug would probably be more optimal.