{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,29]],"date-time":"2026-08-29T05:19:00Z","timestamp":1787980740866,"version":"build-2784847793"},"reference-count":46,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T00:00:00Z","timestamp":1787788800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100018537","name":"National Science and Technology Major Project","doi-asserted-by":"crossref","award":["2025ZD1401302"],"award-info":[{"award-number":["2025ZD1401302"]}],"id":[{"id":"10.13039\/501100018537","id-type":"DOI","asserted-by":"crossref"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Gels"],"abstract":"<jats:p>Lost circulation of oil-based drilling fluids (OBDFs) in deep, fractured formations remains a critical challenge, primarily due to the poor retention and low pressure-bearing capacity of conventional materials on oil-wet rock surfaces. To bridge this gap, this study reports the development and field application of a novel thermo-responsive gel (SBR\u2212g\u2212PSA). Synthesized by grafting highly lipophilic stearyl acrylate (SA) onto a flexible styrene\u2013butadiene rubber (SBR) backbone, the microgel exploits a UCST-like (Upper Critical Solution Temperature) phase transition behavior. At surface temperatures, rigid styrene microdomains act as physical crosslinks, maintaining the particles in a compact, highly dispersible state. Under elevated downhole temperatures (120\u2013180 \u00b0C), these microdomains relax, triggering the massive unfolding and physical entanglement of the octadecyl side chains. This in situ topological evolution generates a resilient three-dimensional network with a high thermal degradation temperature of 346.6 \u00b0C. Rheological and macroscopic sealing evaluations demonstrate that the gel effectively adapts to OBDFs, securely sealing 1\u20131.5 mm fractures and limiting fluid loss to within 5 mL under a 4 MPa differential pressure. Successful field application in the deep well Dashen-X reduced severe fluid leakage from 2.42 m3\/h to zero. This intelligent thermo-responsive platform offers a robust, high-performance technological solution for precise lost circulation control in deep oil and gas exploration.<\/jats:p>","DOI":"10.3390\/gels12090770","type":"journal-article","created":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T10:58:21Z","timestamp":1787828301000},"page":"770","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Development and Application of Oil-Based Thermo-Responsive Gel Lost Circulation Material SBR\u2212g\u2212PSA"],"prefix":"10.3390","volume":"12","author":[{"given":"Zhimin","family":"Liu","sequence":"first","affiliation":[{"name":"Drilling Fluid Technology Service Company, Chuanqing Drilling Engineering Company of China National Petroleum Corporation (CNPC), Chengdu 610066, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chenxi","family":"Nie","sequence":"additional","affiliation":[{"name":"College of Science, China University of Petroleum (Beijing), Beijing 102249, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fengfeng","family":"Xiao","sequence":"additional","affiliation":[{"name":"Drilling Fluid Technology Service Company, Chuanqing Drilling Engineering Company of China National Petroleum Corporation (CNPC), Chengdu 610066, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mengyuan","family":"Chen","sequence":"additional","affiliation":[{"name":"Drilling Fluid Technology Service Company, Chuanqing Drilling Engineering Company of China National Petroleum Corporation (CNPC), Chengdu 610066, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ming","family":"Liu","sequence":"additional","affiliation":[{"name":"Drilling Fluid Technology Service Company, Chuanqing Drilling Engineering Company of China National Petroleum Corporation (CNPC), Chengdu 610066, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qi","family":"Feng","sequence":"additional","affiliation":[{"name":"College of Science, China University of Petroleum (Beijing), Beijing 102249, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Changtao","family":"Yue","sequence":"additional","affiliation":[{"name":"College of Science, China University of Petroleum (Beijing), Beijing 102249, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,27]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Zang, Y.B., Chen, Z.W., Wang, Y., Zhang, Y., Xu, S.C., Xie, J.Y., and Chen, W. 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