Direct Thickeners for Carbon Dioxide (2000)

Direct Thickeners for Carbon Dioxide Robert M. Enick; Robert M. Enick University of Pittsburgh Search for other works by this author on: This Site Google Scholar Eric J. Beckman; Eric J. Beckman University of Pittsburgh Search for other works by this author on: This Site Google Scholar Chunmei Shi; Chunmei Shi University of Pittsburgh Search for other works by this author on: This Site Google Scholar Zhihua Huang; Zhihua Huang University of Pittsburgh Search for other works by this author on: This Site Google Scholar Jianhang Xu; Jianhang Xu University of Pittsburgh Search for other works by this author on: This Site Google Scholar Sevgi Kilic Sevgi Kilic University of Pittsburgh Search for other works by this author on: This Site Google Scholar Paper presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, Oklahoma, April 2000. Paper Number: SPE-59325-MS https://doi.org/10.2118/59325-MS Published: April 03 2000 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Enick, Robert M., Beckman, Eric J., Shi, Chunmei, Huang, Zhihua, Xu, Jianhang, and Sevgi Kilic. "Direct Thickeners for Carbon Dioxide." Paper presented at the SPE/DOE Improved Oil Recovery Symposium, Tulsa, Oklahoma, April 2000. doi: https://doi.org/10.2118/59325-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE Improved Oil Recovery Conference Search Advanced Search AbstractDirect thickeners for dense carbon dioxide were designed and synthesized. Each thickener contained highly CO2-soluble "CO2-philic" fluorinated groups, while "CO2-phobic" functionalities promoted viscosity-enhancing intermolecular associations. Semifluorinated trialkyltin fluorides, fluorinated telechelic ionomers, fluoroacrylate-styrene copolymers and sulfonated fluoroacrylate-styrene copolymers, were soluble to at least several weight percent in dense carbon dioxide without the use of a cosolvent. Increases in solution viscosity were measured using falling cylinder viscometry.The most promising CO2 thickener was a styrene - heptadecafluorodecylacrylate bulk-polymerized random copolymer. The optimal composition of the copolymer was about 30 mol% styrene - 70% fluoroacrylate. For example, a 29% styrene- 71%fluoroacrylate copolymer increased the viscosity of liquid CO2 by a factor of 250 at a concentration of 5 wt% and a shear rate of 20 s-1 at 297K and 34 MPa. A 0.2 wt% copolymer - 99.8 wt% CO2 solution exhibited a viscosity twice that of neat CO2 at shear rates of about 3000 s-1. Greater proportions of styrene in the thickener led to decreased CO2 solubility and solution viscosity, while lower proportions of styrene resulted in greater CO2 solubility but decreased solution viscosity. Solution viscosity increased with increasing copolymer concentration, increasing pressure and decreasing shear rate.IntroductionNumerous attempts have been made to identify a thickener for carbon dioxide to improve the mobility ratio during EOR. Most of the previously evaluated compounded were compounds known to thicken or gel hydrocarbon liquids. Polymers, trialkyltin fluorides, telechelic ionomers, 12-hydroxystearic acid, alcohols, ethoxylated alcohols, aluminum disoaps, silicone oils and surfactants were previously evaluated1–9. None yielded satisfactory results, primarily due to the low solubility of these compounds in carbon dioxide unless large amounts of organic liquid cosolvents such as toluene were introduced.Investigators began designing new compounds that exhibited high carbon dioxide solubility for projects such as supercritical fluid technology reaction or separation technologies. Their formulations of CO2-soluble surfactants, dispersants, polymers and chelating agents resulted in the identification of "carbon dioxide-philic" functional groups. These included fluoroacrylates, fluoroethers, fluoroalkanes and silicones9–13. One investigator noted that a high MW homopolymer of a fluoroacrylate monomer was able to induce an old increase in solution viscosity at a concentration of 7wt% without the need for a cosolvent10.The objective of this study was to design and synthesize thickeners that would exhibit high carbon dioxide solubility and the ability to induce significant increases (2–100 fold) in viscosity. The ideal thickened CO2 solution would be prepared without heating the carbon dioxide to dissolve the thickener and would require very dilute concentrations (0.1–1.0 wt%) of a safe, inexpensive thickener. Dissolution of the thickener should occur at a pressure less than or equal to the MMP of the CO2 flood. The thickened solution would be transparent, single-phase, and shear-thinning.Strategy for Designing Carbon Dioxide ThickenersEach candidate thickener contained a carbon dioxide-philic group for enhancing CO2-solubility and a CO2-phobic group to inducing intermolecular interactions. These interactions resulted in the formation of macromolecular structures in solution, which were capable of causing tremendous increases in solution viscosity. Each molecular design required the optimization of the structure. If too few CO2-phobic groups were employed, no significant increase in solution viscosity would result. If too many CO2-phobic groups were incorporated into the thickener, the CO2-solubility decreased and/or too many intramolecular associations occurred, rendering the thickener ineffective. Keywords: upstream oil & gas, thickened co 2, solubility, direct thickener, diameter 3, carbon dioxide, terminal velocity, viscosity, concentration, solution viscosity Subjects: Improved and Enhanced Recovery This content is only available via PDF. 2000. Society of Petroleum Engineers You can access this article if you purchase or spend a download.