The Impact of Sulfate Level Reduction on Seawater Injection Economics: Using Sulfate Scale Precipitation Kinetics to Our Advantage

Abstract

ADNOC Onshore plans to use seawater as alternative to aquifer water, its source of injection water for over 40 years. However, using seawater for injection introduces a sulfate scaling risk due to incompatibility with formation water. Sulfate in the seawater and cations in the formation water (Ca, Sr) are likely to precipitate, causing scaling and related flow assurance problems and formation damage. Sulfate can be removed from the injection water by means of desulfation, but sulfate removal to well below its scaling concentration is CAPEX intensive and negatively impacts seawater flooding economics. In this paper, the economic benefits of partial sulfate reduction are evaluated, by finding a balance between controllable scaling and costs for inhibition and sulfate removal.