Shifting Sands in a CO2 Desert: Replacing Extracted CO2 with Byproduct CO2 for Use in Enhanced Oil Recovery

摘要

Efforts to sequester or otherwise manage carbon dioxide emissions on a large scale will require an improved understanding of the geospatial characteristics of anthropogenic CO2 sources. Recent work by the authors using newly collected data from the US Environmental Protection Agency showed that even though there are some regions of the US with access to significant supply of CO2, most regions of the country do not have sources that are concentrated enough or large enough to support large-scale carbon management activities. What's more, the life cycle carbon burdens of different CO2 sources varied considerably with some sources, e.g., extracted wells, having a much larger carbon footprint than those where CO2 is a by-product, e.g., acid gas processing facilities. Here, the effect of source switching was explored in the context of CO2-enhanced oil recovery (CO2-EOR). At present most CO2-EOR operations in the United States rely on CO2 that is extracted from dedicated wells generating nearly pure CO2. By-product CO2, in contrast, is produced from a number of other industries including natural gas processing plants where small mass fractions of CO2 are removed from the gas stream. The emissions implications of these two sources of CO2 are significant in the context of CO2-EOR application because in one case, CO2 emissions are being avoided but in another they are not. Yet the switch from an industrial paradigm in which extracted CO2 is used to one in which by-product CO2 may not be as straightforward as it appears. Here, the SimCCS model is applied to the oil-producing Permian basin in west Texas to understand what the effect of source switching would be on CO2 demand, infrastructure, and overall emissions, the results suggest that at present scales of deployment, the costs associated with switching to by-product CO2 are higher-than extracted CO2 because of the need for new infrastructure. Nevertheless, the observed emissions reductions are large in an absolute sense and suggest that this strategy be more seriously considered. A new infrastructure would be needed to connect by-product CO2 sources with CO2-EOR sinks but the cost of this is not so great that with a modest economic incentive, source switching of CO2 could represent a near- term strategy for reducing CO2 emissions and increasing oil production.