Towards Sustainable Oil Production: CO2 Footprint Assessment of EOR Surfactant-Based Processes

Abstract

To meet energy demand while reducing CO2 emissions in a carbon constrained future, one of the key milestones of the roadmap proposed by the International Energy Agency is to stop new oil and gas field developments and extend instead existing fields’ lifetime. Waterflood and EOR recovery methods aiming at optimizing mature fields’ oil production thus appears as technologies of choice. Nonetheless, oil production by waterflood is energy and therefore carbon intensive, especially for oil fields exhibiting high water-cuts, due to produced water handling. Recent communications suggest that chemical EOR processes such as polymer flood reduce the CO2 emitted per barrel of produced oil compared to water flooding, as they reduce water cut and/or accelerate oil production. Few papers however assess the CO2 footprint of surfactant-based processes. In this work, we aim to compare the carbon emissions of different chemical EOR scenarios including polymer, surfactant-polymer and alkaline-surfactant-polymer, with a reference waterflood scenario. We present an exergy-based methodology to estimate energy gains obtained from water-cut decrease while taking into account process efficiency, including oil production, water treatment required for chemical use and chemical production. The corresponding CO2 emission reduction is then estimated from these energy gains. This methodology was applied to two case studies available in the literature, the Mangala field polymer flood pilot and the Taber alkaline-surfactant-polymer flood. Necessary injection and production data were collected to extrapolate production water rate and WOR using Decline Curve Analysis. Results show that implementing polymer or alkaline-surfactant-polymer flooding after waterflooding allows wells to reach higher oil production rates, up to twice as much. In addition, water-oil ratio is more than ten times reduced i.e. less produced water has to be handled while producing more oil. Thus, we show that for both of these fields oil production is less carbon intensive. Furthermore, we considered a hypothetical surfactant-polymer flood to compare to the Taber alkaline-surfactant-polymer flood. Water treatment as well as chemical production energy costs are reduced for the surfactant-polymer due to the absence of added alkali, which induces additional CO2 emission reduction. This study highlights that chemical EOR, in particular polymer and/or surfactant-based processes stands as a potential solution to reduce the carbon footprint of oil recovery while maintaining the production required to sustain the world's energy consumption.