{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T08:56:17Z","timestamp":1791881777409,"version":"4.3.4"},"reference-count":23,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T00:00:00Z","timestamp":1791244800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100017366","name":"Key Research and Development Program of Heilongjiang","doi-asserted-by":"publisher","award":["2024ZX09C02"],"award-info":[{"award-number":["2024ZX09C02"]}],"id":[{"id":"10.13039\/100017366","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>Bubble-point behavior of shale oil under nanoconfinement is critical for understanding phase evolution during CO2-enhanced shale-oil recovery. In this study, visual micro\/nanofluidic PVT experiments were conducted to systematically investigate bubble-point pressure deviations of pentane\u2013CO2, hexadecane\u2013CO2, pentane\/decane\/hexadecane\u2013CO2, and shale oil\u2013CO2 systems. Measurements were performed at gas\u2013oil ratios of 130 and 260 and temperatures of 65\u2013125 \u00b0C using a 10 nm single-scale pore model and a coupled 10 \u03bcm\u201310 nm pore-network model. Experimental results were compared with theoretical predictions from a confinement-modified Peng\u2013Robinson equation of state incorporating capillary pressure, surface adsorption, and critical-property shifts. Furthermore, a metastable nucleation limit was introduced to describe the experimentally observed phase-transition pressure below the equilibrium bubble-point boundary. Pronounced downward deviations toward the metastable region were observed in isolated 10 nm pores. For the pentane\u2013CO2 system at 65 \u00b0C and GOR = 130, the experimentally observed phase-transition pressure was approximately 3.5 MPa, compared with an equilibrium prediction of 4.3 MPa, corresponding to a relative deviation of 18.35%. The deviation decreased as temperature approached the critical region and was reduced at higher GOR. For example, at GOR = 260, the deviation of the hexadecane\u2013CO2 system decreased from 40.63% at 65 \u00b0C to 10.01% at 125 \u00b0C. Fluid composition also strongly affected confinement sensitivity, with heavier hydrocarbon systems exhibiting stronger shifts toward metastable behavior. In contrast, bubble-point pressures in the coupled 10 \u03bcm\u201310 nm network remained close to the equilibrium predictions of the micrometer-scale pores and deviated significantly from the metastable limit. For the shale oil\u2013CO2 system at 65 \u00b0C and GOR = 130, the relative deviation decreased from 29.77% in the isolated 10 nm pore model to only 2.43% in the coupled 10 \u03bcm\u201310 nm network. These results demonstrate that nanoconfined bubble-point behavior is governed by the coupled effects of thermodynamic conditions, fluid composition, metastability, and pore-scale connectivity.<\/jats:p>","DOI":"10.3390\/nano16191260","type":"journal-article","created":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T16:21:46Z","timestamp":1791303706000},"page":"1260","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Bubble-Point Pressure Deviations and Metastable Nucleation in Nanoconfined CO2\u2013Shale Oil Systems: Effects of Temperature, Composition, Gas\u2013Oil Ratio, and Pore-Scale Coupling"],"prefix":"10.3390","volume":"16","author":[{"given":"Dongyan","family":"Qi","sequence":"first","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiawei","family":"Li","sequence":"additional","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Qiang","family":"Liu","sequence":"additional","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shuang","family":"Wang","sequence":"additional","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Siyuan","family":"Cui","sequence":"additional","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yue","family":"Lang","sequence":"additional","affiliation":[{"name":"Daqing Oilfield of China National Petroleum Cooperation, Daqing 163700, China"},{"name":"State Key Laboratory of Continental Shale Oil, Daqing 163712, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jiayi","family":"Zhao","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Deep Oil and Gas, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaozhe","family":"Liang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Deep Oil and Gas, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6293-9580","authenticated-orcid":false,"given":"Junjie","family":"Zhong","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Deep Oil and Gas, School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,10,6]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Lei, Z., Liu, Y., Wang, R., Li, L., Liu, Y., and Zhang, Y. 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