Lemaire, Peter C.K.
(2022)
High-Pressure Solutions of C6F13- and C4F9- Based Polyfluoroacrylates in CO2: Synthesis, Solubility, Viscosity, Adsorption, and Sealing of Cement Cracks.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
A thorough literature review and experimental comparison of many purported CO2-thickeners has demonstrated that polyfluoroacrylate (PFA) is the only high molecular weight homopolymer capable of dissolving in CO2 at typical petroleum reservoir conditions. PFA is a liquid carbon dioxide (CO2)-soluble and supercritical CO2-soluble, amorphous or semi-crystalline, hydrophobic and oleophobic polymer. In this dissertation, several PFAs with -C6F13 and -C4F9 based pendant moieties have been synthesized via bulk polymerization. The ability of PFA-CO2 solutions to dissolve in and thicken CO2 without the need for additional co-solvents is assessed and compared to the previously reported C8F17-based PFAs. With the exception of one ultra-high molecular weight sample (Mw = 2.89E6 Da) that could not dissolve in CO2 up to 62 MPa, all the samples synthesized showed remarkably similar solubility in CO2 from 1-5 wt% and 25-125 °C as the C8F17-based PFAs in the literature. In addition, both the C4F9 and C6F13 PFA showed the ability to thicken CO2 like their C8F17 analogs. Although all three versions of PFA exhibited comparable CO2-solubility and CO2-thickening, PFA based on the -C6F13 and -C4F9 moieties will generate more benign perfluoroalkanoic ultimate degradation products. C6F13-based PFAs were then tested for their ability to seal dry cracks in Portland cement. In conjunction with researchers at NETL and SINTEF, it was shown that high-pressure PFA-CO¬2 solutions can significantly reduce the apparent permeability of dry cracks in split or cracked Portland cement cylinders. For a cracked cement with nanoDarcy apparent permeability, the crack was quickly and completely sealed. For a cracked cement sample with microDarcy apparent permeability, the apparent permeability was reduced by 92% when the experiment was terminated because of excessive pressure drop buildup. For cracks with milliDarcy apparent permeability, reductions in apparent permeability ranged from 22-96%, with the better results generally associated with higher PFA concentration, lower crack apparent permeability, and slower PFA-CO2 injection rates. After these tests, the cement halves, which were glued together by PFA, were pried apart. Wettability tests demonstrated that PFA coats the entire cement surface area that bounds the crack, rather than just the inlet of the crack.
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Details
| Item Type: |
University of Pittsburgh ETD
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| Status: |
Unpublished |
| Creators/Authors: |
|
| ETD Committee: |
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| Date: |
10 June 2022 |
| Date Type: |
Publication |
| Defense Date: |
13 December 2021 |
| Approval Date: |
10 June 2022 |
| Submission Date: |
16 March 2022 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Number of Pages: |
119 |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Swanson School of Engineering > Chemical and Petroleum Engineering |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
CO2, Polyfluoroacrylate, Viscosity, Phase Behavior |
| Date Deposited: |
10 Jun 2022 18:38 |
| Last Modified: |
10 Jun 2022 18:38 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/42376 |
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