Water-carbon dioxide emulsions for improved CO2 sequestration and enhanced oil recovery in depleted carbonate reservoirs

Carbon capture and storage technologies aiming to reduce the climate change need reservoirs able to store CO2 for a very long time. Currently producing reservoirs on the verge of running out of oil and gas have proven to have both reliable sealing and excellent flow. Strategy developed in this project is a modification of one of the best EOR options, alternating water and CO2 flooding (WAG). With the added ability ability to handle wildly varying CO2 production (from relatively low rates in carbon dioxide-rich fields like Sleipner and Snøhvit to coal- and gas power plants). In addition, creating more efficient emulsion between water and CO2 will offer a promising capture method that can make efficient total solutions of capture, injection and storage. We have used the atom-level molecular dynamics combined with quantum chemistry techniques to determine how to chemically modify existing surfactants to enable resulting stable emulsions to trap CO2 in reservoir and insure its safe storage together with improved EOR. Our parallel simulation methods harnessed the power of modern GPUs to follow the time evolution of multiphase systems over thousands of nanoseconds and allow us to compare the proposed modifications. By adding chemical groups with certain properties to compounds originally designed just for CO2 separation, we successfully made them both attractive both for water-CO2 interface and possessing extra affinity for surfaces between CO2 and oil left in reservoir.

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Carbon capture and storage efforts aimed at reducing the climate change have a growing need for reservoirs with good flow properties able to store CO2 efficiently. Given that they kept the hydrocarbons trapped for a geological time, reservoirs that produc ed hydrocarbons for years have verified flow properties as well as storage sealing. Alternating water and CO2 flooding (WAG) has proven very efficient EOR option compared to injection of either water or carbon dioxide. Prolonging the production in a reser voir will allow to avoid huge one-time CO2 emissions associated with exploitation a new field. The injection of CO2/water emulsion instead of WAG as proposed here is not a new strategy. What is new in this project is that we plan to use molecular modellin g to design surfactant candidates with specific properties tailored for safe long terms storage of CO2 while at the same time ensuring more efficient hydrocarbon recovery. Unlike ordinary EOR for storing CO2, we aim at emulsifiers producing stable emulsio ns with CO2 but even more stable emulsions with typical in situ oil components, so that the emulsion would release CO2 via preferential emulsion formation coming in contact with hydrocarbons. The primary focus of this project is to offer an efficient CO2 storage option, with both CO2 fraction and the injection rate mainly dictated by storage efficiency. Potential benefits in terms of the EOR effect will be an additional gain which will offset some of the project costs. Beside CO2-producing power plants, a n important target for this approach would be carbon dioxide-rich fields like Sleipner and Snøhvit. It would be possible to reinject CO2 separated from the hydrocarbon well streams back into reservoir, thus mitigating the emission of carbon dioxide. Metho ds developed through this project will also be relevant for potential CO2 separation from flue gas using emulsion formation, with the actual regeneration strategy depending on the properties of actual surfactants.