9.1 Introduction

Injecting CO2 into mature oil fields has been a method used for enhancing oil production for about 40 years. Enhanced oil recovery (EOR) refers to a suite of techniques that can be applied to reservoirs with declining oil production to maintain or improve production. Most fields considered for EOR have already undergone primary production – in which the natural reservoir pressure brings the oil to surface – and secondary production methods, usually by injecting water to restore reservoir pressure. Using CO2 for EOR (CO2 EOR) has proven successful in rejuvenating oil production in many maturing oil fields and extending their productive lives by decades – the degree of improvement in production is highly dependent on site-specific reservoir characteristics and oil composition, and not all oil fields are amenable to CO2 EOR.

Of the more than 130 CO2 EOR projects in operation globally, the considerable majority take place in North America and of these, about half are in a geologic setting known as the Permian Basin in West Texas. There are other commercial CO2 EOR operations ongoing in Canada, Turkey, and Hungary, and pilot projects scattered even further afield. The historical development of CO2 EOR has largely been constrained by the availability of inexpensive CO2In the US, large naturally occurring accumulations of CO2 (N-CO2) are found in geologic reservoirs such as McElmo Dome, Doe Canyon Deep, and Sheep Mountain in Colorado and Bravo Dome in New Mexico, sources from which the CO2 can be produced relatively inexpensively. CO2 produced by human activities, such as those associated with extraction or burning of fossil fuels or other industrial process, is considered anthropogenic CO2 (A-CO2) and is also used for CO2 EOR. Because A-CO2 must be separated or captured using physical and chemical processes it is generally more expensive and historically less available than N-CO2. A-CO2, however, is now becoming increasingly recognised as an economically viable option as more operators globally are interested in CO2 EOR and geologic (N-CO2) sources are not always accessible. In North America more than 6500 km of pipelines transport CO2 for use in CO2 EOR operations to produce around 300,000 bbl of oil per day. The expected supply of CO2 in 2012 for EOR in North America is 66 Mtpa of which over 25 per cent is A-CO2More anthropogenic CO2 is injected by operating CO2 EOR projects than by any other storage option for CCS (Figure 65).

This chapter presents the role CO2 EOR may play in CCS (along with some of the technical and legal aspects of CO2 EOR relative to carbon storage) and describes the economic, commercial, and regulatory landscape influencing these operations.

FIGURE 65 Potential volume of CO2 stored by storage type options and Asset Lifecycle stage