Pore Size Scale Oil Mobilization and Fractal Evolution of Residual Oil Occurrence Spaces in Deep-Water Sandstone: Influence of Waterflooding Mode
4 affiliations
- 1China-Zambia Belt and Road Joint Laboratory on Green and Safe Development of Mineral Resources, University of Science and Technology Beijing, Beijing 100083, China
- 2School of Resource and Safety Engineering, University of Science and Technology Beijing, Beijing 100083, China
- 3State Key Laboratory of Offshore Oil and Gas Exploitation, Beijing 102209, China
- 4China National Offshore Oil Corporation (CNOOC) Research Institute Ltd., Beijing 100028, China
Abstract
Waterflooding intensity strongly affects oil–water migration in deep-water sandstone reservoirs with bottom edge water, yet oil mobilization across different oil-occupied pore scales and the evolution of residual oil occurrence spaces under different waterflooding modes remain unclear. Constant high-rate and rate-increasing waterflooding experiments were conducted on deep-water sandstone cores. Online nuclear magnetic resonance (NMR) monitoring and fractal analysis were used to distinguish oil-occupied pore scale intervals from oil-phase T2 signals and quantify the evolution of oil saturation and fractal dimensions under different waterflooding intensities. In 0–100 pore volumes (PV), rate-increasing waterflooding yielded slightly lower recovery than constant high-rate waterflooding. During 100–1000 PV, however, its recovery increment reached 8.68–12.39 percentage points versus 2.91–6.01 percentage points under constant high-rate waterflooding, increasing final recovery by 5.25–6.17 percentage points. Oil mobilization was dominated by macropore and mesopore intervals, with limited micropore mobilization. In 100–1000 PV, rate-increasing waterflooding caused larger oil saturation reductions in macropore and mesopore intervals (4.43–10.60 and 1.75–3.99 percentage points) than constant high-rate waterflooding (3.05–4.42 and 0.01–1.30 percentage points). Fractal dimensions increased during waterflooding, with the largest changes occurring in the micropore interval. Fractal dimension increments in mesopore and macropore intervals were 0.09–0.12 and 0.04–0.06 under rate-increasing waterflooding versus 0.04–0.07 and 0.03–0.05 under constant high-rate waterflooding. The results provide core scale insight into the relationship between injection history, late-stage oil depletion, and the T2 distribution of remaining oil in deep-water sandstone.
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BibTeX
@article{li2026pore,
title = {{Pore Size Scale Oil Mobilization and Fractal Evolution of Residual Oil Occurrence Spaces in Deep-Water Sandstone: Influence of Waterflooding Mode}},
author = {Hongzhu Li and Wei Zheng and Junzhe Jiang and Shaobin Cai and Weiyao Zhu and Debin Kong},
journal = {Fractal and Fractional},
year = {2026},
month = nov,
doi = {10.3390/fractalfract10110772},
url = {https://www.mdpi.com/2504-3110/10/11/772},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Pore Size Scale Oil Mobilization and Fractal Evolution of Residual Oil Occurrence Spaces in Deep-Water Sandstone: Influence of Waterflooding Mode
AU - Hongzhu Li
AU - Wei Zheng
AU - Junzhe Jiang
AU - Shaobin Cai
AU - Weiyao Zhu
AU - Debin Kong
PY - 2026
DA - 2026/11/05
JO - Fractal and Fractional
DO - 10.3390/fractalfract10110772
UR - https://www.mdpi.com/2504-3110/10/11/772
AB - Waterflooding intensity strongly affects oil–water migration in deep-water sandstone reservoirs with bottom edge water, yet oil mobilization across different oil-occupied pore scales and the evolution of residual oil occurrence spaces under different waterflooding modes remain unclear. Constant high-rate and rate-increasing waterflooding experiments were conducted on deep-water sandstone cores. Online nuclear magnetic resonance (NMR) monitoring and fractal analysis were used to distinguish oil-occupied pore scale intervals from oil-phase T2 signals and quantify the evolution of oil saturation and fractal dimensions under different waterflooding intensities. In 0–100 pore volumes (PV), rate-increasing waterflooding yielded slightly lower recovery than constant high-rate waterflooding. During 100–1000 PV, however, its recovery increment reached 8.68–12.39 percentage points versus 2.91–6.01 percentage points under constant high-rate waterflooding, increasing final recovery by 5.25–6.17 percentage points. Oil mobilization was dominated by macropore and mesopore intervals, with limited micropore mobilization. In 100–1000 PV, rate-increasing waterflooding caused larger oil saturation reductions in macropore and mesopore intervals (4.43–10.60 and 1.75–3.99 percentage points) than constant high-rate waterflooding (3.05–4.42 and 0.01–1.30 percentage points). Fractal dimensions increased during waterflooding, with the largest changes occurring in the micropore interval. Fractal dimension increments in mesopore and macropore intervals were 0.09–0.12 and 0.04–0.06 under rate-increasing waterflooding versus 0.04–0.07 and 0.03–0.05 under constant high-rate waterflooding. The results provide core scale insight into the relationship between injection history, late-stage oil depletion, and the T2 distribution of remaining oil in deep-water sandstone.
SN - 2504-3110
ER -