How Polymer Flooding Reduces CO2 Emissions and Energy Consumption – An Exergy Return On Exergy Investment Case Study

Abstract

Abstract A major part of the energy transition transformation is reduction of carbon footprint in the current oil and gas operations. The energy consumption in the whole chain of operations needs to be evaluated. The energy efficiency of water flooding is compared to polymer flooding for extraction of heavy oil from an oil field in the UK sector of the North Sea is evaluated using Life Cycle Assessment (LCA) with the concept of Exergy-Return-on-Exergy-Investment (ERoEI). The LCA allows for separation of the process into material and work streams, assessing the impact of each separately. By applying the exergy concept, i.e. the amount of useful energy invested or returned, a comparison of different process steps and different extraction strategies can be achieved. The Oil field, characterized by an oil viscosity of approximately 80 cP, poses challenges for water flooding operations. Early water breakthrough in producers and high water cuts are anticipated outcomes. While thermal EOR methods could potentially address sweep efficiency concerns, they come at a considerable energy and CO2 cost. Building upon recent advancements in the understanding of polymer flooding for heavy oil extraction, a low-dosage polymer flood was implemented, yielding highly positive results. By utilizing the established water channels in the field, cross-flow of oil into the channels generates a rapid increase in oil production by polymer. In this paper we present the results of an expansion of the current polymer flood to new sections of the field. When comparing like for like development infrastructure and UR recovery times scales, polymer flood leads to a strong acceleration of the oil production which results in a significant increase in Net-Present-Value (NPV). Furthermore, there is an increase of 2.4 times the exergy return on exergy investment and a reduction of 35 % in CO2 emissions. Extraction of heavy oil has for a long time been dominated by energy intensive and/or inefficient methods. Our study demonstrates that the implementation of low-dosage polymer flooding not only significantly enhances recovery rates, accelerating production by decades, but also accomplishes this with reduced energy cost. The CO2 intensity (kg CO2/bbl oil) is quantified and providing a useful optimization factor for the polymer flood design.