Use of CO2 Containing Impurities for Miscible Enhanced Oil Recovery
- John Roland Wilkinson (ExxonMobil Upstream Research) | Alana Leahy-Dios (ExxonMobil Upstream Research) | Gary F. Teletzke (ExxonMobil Upstream Research) | Jasper Lane Dickson (ExxonMobil)
- Document ID
- Society of Petroleum Engineers
- International Oil and Gas Conference and Exhibition in China, 8-10 June, Beijing, China
- Publication Date
- Document Type
- Conference Paper
- 2010. Society of Petroleum Engineers
- 5.2.1 Phase Behavior and PVT Measurements, 6.5.3 Waste Management, 4.1.2 Separation and Treating, 4.1.3 Dehydration, 4.3.1 Hydrates, 4.1.6 Compressors, Engines and Turbines, 5.3.2 Multiphase Flow, 2.2.2 Perforating, 4.1.4 Gas Processing, 5.5 Reservoir Simulation, 4.6 Natural Gas, 6.5.1 Air Emissions, 4.2 Pipelines, Flowlines and Risers, 5.1 Reservoir Characterisation, 5.7.2 Recovery Factors, 5.4 Enhanced Recovery, 4.3.4 Scale, 5.2.2 Fluid Modeling, Equations of State, 4.1.5 Processing Equipment, 5.8.7 Carbonate Reservoir, 1.2.3 Rock properties, 4.2.2 Pipeline Transient Behavior, 4.2.3 Materials and Corrosion, 5.4.2 Gas Injection Methods, 4.6.2 Liquified Natural Gas (LNG)
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When conducting enhanced oil recovery (EOR) projects, utilizing CO2 as a solvent, there are three primary options for sourcing the CO2 injectant. These are naturally occurring deposits, anthropogenic flue gas capture, or recycled CO2 from an earlier stage of an EOR project. All of these sources may contain impurities that will change the properties of the injectant, potentially impacting all stages of the system. For instance, captured flue gas may contain quantities of N2, while produced or recycled sources may contain CH4 and/natural gas liquids (NGL). Either or both may contain SO2 or H2S. Each of these impurities has a different effect on the thermodynamic and fluid flow characteristics of CO2; exhibiting either beneficial or detrimental impact on miscibility, density and viscosity of the injectant and its interaction with in situ hydrocarbons. Impurities can also modify compression capacity, corrosion control and pipeline specifications. This paper describes the impact of CO2 impurities on all stages of an EOR project, from CO2 capture to flood efficiency prediction.
Miscibility, density, and viscosity, along with rock properties, are the primary determinants of flood efficiency in a given rock and fluid setting. A screening tool has been developed to estimate EOR performance for different crude oils. Screening is done for miscibility, density, and viscosity and other parameters important to the efficiency of an EOR process. A key component of the screening tool is a solubility-parameter-based approach to screening CO2 injectants containing impurities for miscibility against a range of crude oils. This technology, combined with worldwide operating experience, has been used to evaluate EOR potential in reservoirs across a full range of pressure, temperature, and fluid compositions. By accurately evaluating the impact of impurities in the injectant, it is also possible to estimate an economic optimum solution for securing and utilizing an injectant supply without incurring the additional costs of treating the stream to remove and dispose of all impurities.
By way of a field example, the paper discusses the impact of miscibility, density and viscosity on the efficiency of the CO2 miscible EOR process. It also presents investigations aimed at extending current light oil recovery projects into reservoirs with either residual oil zones (ROZ), viscous oils or biodegraded crudes.
Injecting CO2 for EOR has the dual benefit of increasing energy supply and storing greenhouse gas emissions. A recent global estimate of incremental oil recovery, with full implementation of CO2 EOR projects, is that 450-820 billion barrels of additional oil could be recovered while storing 130 to 240 Gt of CO2.1 The expectation is that the primary future supply of CO2 for injection will be anthropogenic CO2. When a CO2 infrastructure develops there will potentially be a blend of source streams containing different types and levels of impurities. Therefore it is important to examine the potential impact of these impurities on the full system of compression, transport, and wells/reservoirs with EOR potential and the costs of purifying the streams at source versus injecting a stream containing impurities.
Economic competition for use in EOR projects requires that CO2 from anthropogenic sources be delivered to the field at price levels comparable with naturally sourced CO2 supply. Currently, CO2 from naturally-occurring sources is priced at <$2/kcf in the Permian Basin, USA whereas traditional post-combustion amine based capture, compression, and transport costs >$5/kcf. Several carbon capture technologies are under development aiming at lowering the cost of anthropogenic CO2. Alternative capture sources will be discussed in this paper with a focus on potential impurities in the CO2 and the impact, if any, on future EOR projects. The impact of impurities in CO2 is investigated for all stages of a potential EOR process: capture, compression, transport, well injection, and EOR implementation.
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