Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing
Degradation of drag reducer polyacrylamide under high volume hydraulic fracturing (HVHF) conditions alters its polymer size, distribution and chemical composition, potentially affecting the toxicity and treatability of the resulting wastewater. This study focused on a non-chemical pathway-mechanic...
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Royal Society of Chemistry (RSC)
2020
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| Online Access: | https://hdl.handle.net/1721.1/123517 |
| _version_ | 1826212290448326656 |
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| author | Xiong, Boya Purswani, Prakash Pawlik, Taylor Samineni, Laxmicharan Karpyn, Zuleima T. Zydney, Andrew L. Kumar, Manish |
| author2 | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Xiong, Boya Purswani, Prakash Pawlik, Taylor Samineni, Laxmicharan Karpyn, Zuleima T. Zydney, Andrew L. Kumar, Manish |
| author_sort | Xiong, Boya |
| collection | MIT |
| description | Degradation of drag reducer polyacrylamide under high volume hydraulic fracturing (HVHF) conditions alters its
polymer size, distribution and chemical composition, potentially affecting the toxicity and treatability of the
resulting wastewater. This study focused on a non-chemical pathway-mechanical degradation of
polyacrylamide under ultra-high fluid strain conditions (∼10[superscript 7] s[superscript −1]) that uniquely exist during HVHF but has not
yet been explored experimentally. PAM solutions were subjected to an abrupt contraction into a narrow
capillary driven by a high-pressure precision pump (∼10 000 psi). The change in polyacrylamide size distribution
was evaluated by size exclusion chromatography. The peak polymer molecular weight (MW) after a single-pass
through the capillary decreased from 10[superscript 7] to 7 × 10[superscript 5] Da at deformation rate V/R = 4 × 10[superscript 6] s[superscript −1]. The extent of degradation increased with V/R, approximately following an empirical scaling relationship of MW ∝ V[superscript −0:69]/R for the
polyacrylamide with an initial MW ≈ 10[superscript 7] Da. Degraded PAM with lower MW (<10[superscript 6] Da) showed minimal
degradation during multiple flow passes even at high deformation rates, suggesting that most mechanical
degradation occurs at the first entrance into the fracture. Relative to chemical degradation, mechanical
degradation caused a narrowing of the MW distribution due to greater degradation of the larger MW polymers
and preferential mid-chain polymer scission. In addition, we saw no detectable change in chemical
composition during mechanical scission, in contrast to the generation of carbonyl groups during oxygenic
radical induced chemical degradation. Combining both chemical and mechanical mechanisms during HVHF
operation, we propose an initial mechanical breakage of polymer chain by fluid strain, followed by chemical
degradation under the high temperature and appropriate mineralogical conditions. These findings provide
critical information for understanding the nature of degradation byproducts from polyacrylamide, and the
treatability of polyacrylamide fragment-containing wastewaters. |
| first_indexed | 2024-09-23T15:19:02Z |
| format | Article |
| id | mit-1721.1/123517 |
| institution | Massachusetts Institute of Technology |
| last_indexed | 2024-09-23T15:19:02Z |
| publishDate | 2020 |
| publisher | Royal Society of Chemistry (RSC) |
| record_format | dspace |
| spelling | mit-1721.1/1235172022-09-29T14:11:39Z Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing Xiong, Boya Purswani, Prakash Pawlik, Taylor Samineni, Laxmicharan Karpyn, Zuleima T. Zydney, Andrew L. Kumar, Manish Massachusetts Institute of Technology. Department of Civil and Environmental Engineering Environmental Engineering Water Science and Technology Degradation of drag reducer polyacrylamide under high volume hydraulic fracturing (HVHF) conditions alters its polymer size, distribution and chemical composition, potentially affecting the toxicity and treatability of the resulting wastewater. This study focused on a non-chemical pathway-mechanical degradation of polyacrylamide under ultra-high fluid strain conditions (∼10[superscript 7] s[superscript −1]) that uniquely exist during HVHF but has not yet been explored experimentally. PAM solutions were subjected to an abrupt contraction into a narrow capillary driven by a high-pressure precision pump (∼10 000 psi). The change in polyacrylamide size distribution was evaluated by size exclusion chromatography. The peak polymer molecular weight (MW) after a single-pass through the capillary decreased from 10[superscript 7] to 7 × 10[superscript 5] Da at deformation rate V/R = 4 × 10[superscript 6] s[superscript −1]. The extent of degradation increased with V/R, approximately following an empirical scaling relationship of MW ∝ V[superscript −0:69]/R for the polyacrylamide with an initial MW ≈ 10[superscript 7] Da. Degraded PAM with lower MW (<10[superscript 6] Da) showed minimal degradation during multiple flow passes even at high deformation rates, suggesting that most mechanical degradation occurs at the first entrance into the fracture. Relative to chemical degradation, mechanical degradation caused a narrowing of the MW distribution due to greater degradation of the larger MW polymers and preferential mid-chain polymer scission. In addition, we saw no detectable change in chemical composition during mechanical scission, in contrast to the generation of carbonyl groups during oxygenic radical induced chemical degradation. Combining both chemical and mechanical mechanisms during HVHF operation, we propose an initial mechanical breakage of polymer chain by fluid strain, followed by chemical degradation under the high temperature and appropriate mineralogical conditions. These findings provide critical information for understanding the nature of degradation byproducts from polyacrylamide, and the treatability of polyacrylamide fragment-containing wastewaters. 2020-01-22T13:29:32Z 2020-01-22T13:29:32Z 2020-01 2019-06 Article http://purl.org/eprint/type/JournalArticle 2053-1400 2053-1419 https://hdl.handle.net/1721.1/123517 Xiong, Boya et al. "Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing." Environmental Science: Water Research & Technology 6, 1 (January 2020): 166-172 © 2020 The Royal Society of Chemistry http://dx.doi.org/10.1039/c9ew00530g Environmental Science: Water Research & Technology Creative Commons Attribution Noncommercial 3.0 unported license https://creativecommons.org/licenses/by-nc/3.0/ application/pdf Royal Society of Chemistry (RSC) Royal Society of Chemistry (RSC) |
| spellingShingle | Environmental Engineering Water Science and Technology Xiong, Boya Purswani, Prakash Pawlik, Taylor Samineni, Laxmicharan Karpyn, Zuleima T. Zydney, Andrew L. Kumar, Manish Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title | Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title_full | Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title_fullStr | Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title_full_unstemmed | Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title_short | Mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| title_sort | mechanical degradation of polyacrylamide at ultra high deformation rates during hydraulic fracturing |
| topic | Environmental Engineering Water Science and Technology |
| url | https://hdl.handle.net/1721.1/123517 |
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