Changes in Formation Water Composition During Water Storage at Surface and Post Re-injection

Abstract Sub-surface operations such as geological carbon storage include the production, storage at surface and re-injection of formation water. Here we present results from a field-based experiment, detailing the important role of storage conditions controlling mineral dissolution and precipitation associated with the re-injection of production water. During water storage at surface, the cooling and degassing of CO 2 from produced waters and oxygenation coincides with a decrease in dissolved ions, which indicate carbonates, silicates and iron oxyhydroxides precipitate. The re-injected water is undersaturated relative to carbonate minerals under reservoir conditions leading to their dissolution in the reservoir.