Direct Contact Steam Generation Reduces Carbon Intensity

Abstract

Abstract Steam for enhanced oil recovery is typically generated using Once-Through-Steam-Generators (OTSG) produced at large central facilities with the steam then pipelined to each injection well. As much as 50% of the energy can be lost before it reaches the well bore with the combustion emissions vented to atmosphere. Direct Contact Steam Generation (DCSG) injects both steam and hot combustion flue gases into the reservoir. Oil production is increased by reducing oil viscosity through heat while repressuring the reservoir with flue gases and improving miscibility with the CO2 that remains in the reservoir. This combination greatly improves the Steam-Oil-Ratio (SOR) for increased oil recovery as well as delivering environmental benefits related to reduced water requirements and lower emissions resulting in a much lower carbon intensity. DCSG water requirements are 11% less than OTSG methods as water is created by the combustion process, this water is then injected into the reservoir rather than lost to the atmosphere. As most of the DCSG process emissions are indirect, emissions can be further reduced by as much as 30% with the use of low carbon intensity grid electricity for compression. Pilot results show that DCSG used less water, with 70% of the CO2 retained in the formation. Lower SOR and CO2 retained in the reservoir demonstrates lower carbon intensity relative to OTSG. DCSG offers heavy oil operators a novel, viable, method to economically extract currently uncoverable reservoirs at a lower carbon intensity than traditional methods.