{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,10]],"date-time":"2025-10-10T01:06:45Z","timestamp":1760058405822,"version":"build-2065373602"},"reference-count":67,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2025,3,31]],"date-time":"2025-03-31T00:00:00Z","timestamp":1743379200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["21975139","ZR2017MB042"],"award-info":[{"award-number":["21975139","ZR2017MB042"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"Natural Science Foundation of Shandong Province","award":["21975139","ZR2017MB042"],"award-info":[{"award-number":["21975139","ZR2017MB042"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Gels"],"abstract":"<jats:p>To address the rapid crosslinking reaction and short stability duration of polyacrylamide gel under high salinity and temperature conditions, this paper proposes utilizing urea to delay the nucleophilic substitution crosslinking reaction among polyacrylamide, hydroquinone, and formaldehyde. Additionally, urea regulates the precipitation of calcium and magnesium ions, enabling the in situ preparation of an organic\/inorganic composite gel consisting of crosslinked polyacrylamide and carbonate particles. With calcium and magnesium ion concentrations at 6817 mg\/L and total salinity at 15 \u00d7 104 mg\/L, the gelation time can be controlled to range from 6.6 to 14.1 days at 95 \u00b0C and from 2.9 to 6.5 days at 120 \u00b0C. The resulting composite gel can remain stable for up to 155 days at 95 \u00b0C and 135 days at 120 \u00b0C. The delayed gelation facilitates longer-distance diffusion of the gelling agent into the formation, while the enhancements in gel strength and stability provide a solid foundation for improving the effectiveness of profile control and water shut-off in oilfields. The urea-controlling method is novel and effective in extending the high-temperature cross-linking reaction time of polyacrylamide. By converting calcium and magnesium ions into inorganic particles, it enables the in situ preparation of organic\/inorganic composite gels, enhancing their strength and stability.<\/jats:p>","DOI":"10.3390\/gels11040256","type":"journal-article","created":{"date-parts":[[2025,3,31]],"date-time":"2025-03-31T05:10:07Z","timestamp":1743397807000},"page":"256","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Urea Delays High-Temperature Crosslinking of Polyacrylamide for In Situ Preparation of an Organic\/Inorganic Composite Gel"],"prefix":"10.3390","volume":"11","author":[{"ORCID":"https:\/\/orcid.org\/0009-0006-6621-9963","authenticated-orcid":false,"given":"Li","family":"Liang","sequence":"first","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Junlong","family":"Li","sequence":"additional","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5266-6398","authenticated-orcid":false,"given":"Dongxiang","family":"Li","sequence":"additional","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jie","family":"Xu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Bin","family":"Zheng","sequence":"additional","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3183-3537","authenticated-orcid":false,"given":"Jikuan","family":"Zhao","sequence":"additional","affiliation":[{"name":"Key Laboratory of Optic-Electro Sensing and Analytical Chemistry of Life Science, Ministry of Education, Qingdao University of Science and Technology, Qingdao 266042, China"},{"name":"Lab of Colloids and Functional Nanostructures, College of Chemistry and Molecular Engineering, Qingdao University of Science and Technology, Qingdao 266042, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2025,3,31]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/S0920-4105(00)00015-2","article-title":"A review of thermally stable gels for fluid diversion in petroleum production","volume":"26","year":"2000","journal-title":"J. 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