Safe storage of Co 2 together with improved oil recovery by Co 2-enriched water injection

Abstract

The 2007 IEA's World Energy Outlook report predicts that the world's energy needs will grow by 55% between 2005 and 2030, with fossil fuels accounting for 84% of this massive projected increase in energy demand. An undesired side effect of burning fossil fuels is carbon dioxide (CO 2) emission which is now widely believed to be responsible for the problem of global warming. Various strategies are being considered for addressing the increase in demand for energy and at the same time developing technologies to make energy greener by reducing CO 2 emissions. One of these strategies is to ‘capture’ produced CO 2 instead of releasing it into the atmosphere. Capturing CO 2 and its injection in oil reservoirs can lead to improved oil recovery as well as CO 2 retention and storage in these reservoirs. The technology is referred to as CCS (carbon capture and storage). Large point sources of CO 2 (e.g., coal-fired power plants) are particularly good candidates for capturing large volumes of CO 2. However, CO 2 capture from power plants is currently very expensive. In addition to high costs of CO 2 capture, the very low pressure of the flue gas (1 atm) and its low CO 2 content (typically 10–15%) contribute to the high cost of CO 2 capture from power plants and the subsequent compression. This makes conventional CO 2 flooding (which requires very large volumes of CO 2) uneconomical in many oil reservoirs around the world which would otherwise be suitable candidates for CO 2 injection. Alternative strategies are therefore needed to utilize smaller sources of CO 2 that are usually available around oil and gas fields and can be captured at lower costs (due to their higher pressure and higher CO 2 concentration). We investigate the potential of carbonated (CO 2-enriched) water injection (CWI) as an injection strategy for improving recovery from oil reservoirs with the added benefit of safe storage of CO 2. The performance of CWI was investigated by conducting high-pressure flow visualization as well as coreflood experiments at reservoir conditions. The results show that CWI significantly improves oil recovery from water flooded porous media. A relatively large fraction of the injected CO 2 was retained (stored) in the porous medium in the form of dissolved CO 2 in water and oil. The results clearly demonstrate the huge potential of CWI as a productive way of utilizing CO 2 for improving oil recovery and safe storage of potentially large cumulative quantities of CO 2.