科研之友
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摘要
The injection of supercritical carbon dioxide (sc-CO2) into depleted or overproduced oil reservoirs has become a popular practice for enhancing oil recovery over the last several decades, because of the favorable mobility characteristics of miscible CO2 floods. Unfortunately, dissolved CO2 often causes mass precipitation of heavy-end hydrocarbon fractions such as asphaltenes, leading to formation damage. The prevention of formation damage ensuing from asphaltene deposition in porous rocks often requires the use of chemical additives such as solvents or inhibitors. Effective additives are able to disperse asphaltene aggregates by curbing their growth in the bulk phase. In particular, CO2-soluble polymers represent a promising type of asphaltene dispersants, since they can eliminate the need for large amounts of hydrocarbon solvent additives to injection mixtures. However, most of these polymers have been relatively untested and their interactions with asphaltenes in sc-CO2 are still unclear. In this study, a siloxane-based polymer was introduced as a potential candidate for an effective, soluble, and environmentally friendly polymeric dispersant. Molecular dynamics (MD) simulations and calculations based on the Flory-Huggins polymer solution theory were conducted to demonstrate the superior low-pressure solubility of this new polymer, compared to two other commercially available polymers: polyvinyl acetate and polydimethylsiloxane. The new polymer was also shown to effectively maintain the dispetsity of three different types of model asphaltenes in bulk sc-CO2 by maintaining low aggregation numbers and reducing the interaction energy between the asphaltene molecules. In addition, the polymer was effective at preventing the adsorption of polar asphaltenes onto calcite surfaces in sc-CO2 via hydrogen bonding.
- 出版日期2016-9
