Pore-scale investigation of two-dimensional water–oil displacement in fractured porous media

• Published in: European physical journal plus Vol. 139; no. 7; p. 611
• Main Authors: Wu, Mingyang, Song, Zhenlong, Zhu, Zhengwen, Shi, Di, Xia, Debin, Li, Qianying
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 14.07.2024; Springer Nature B.V
• Subjects: Applied and Technical Physics; Atomic; Bifurcations; Boundary conditions; Complex Systems; Condensed Matter Physics; Efficiency; Enhanced oil recovery; Experiments; Flow velocity; Injection; Mathematical and Computational Physics; Methods; Molecular; Morphology; Optical and Plasma Physics; Permeability; Physics; Physics and Astronomy; Pores; Porous media; Regular Article; Reservoirs; Simulation; Theoretical; Viscosity; Water flooding; Water injection
• ISSN: 2190-5444; 2190-5444
• DOI: 10.1140/epjp/s13360-024-05426-2

The pore and branching fracture structures in both naturally and artificially fractured reservoirs significantly affect the water–oil displacement mechanisms. Therefore, understanding these mechanisms in such porous media is crucial for the development of low-permeability reservoirs. Considering that there are both single and bifurcated factures in these media, 12 geometric models for porous media with pure pores, a single-fracture, and a Y-shaped bifurcated fracture (YFPM) were constructed. A phase-field method was adopted to simulate the water–oil displacement in these three types of media. Furthermore, the effects of fracture bifurcation angle, fracture width, fracture length, and water injection rate on the water–oil displacement in the YFPM were further investigated. The results are as follows. (1) The displacement in the three types of media includes both viscous and capillary fingering. The breakthrough time and displacement efficiency in the YFPM are the smallest among the three media types. Furthermore, compared to the porous media with pure pores, the breakthrough times in the porous media with a single fracture and YFPM are reduced by approximately 33% and 50%, respectively. (2) The breakthrough time in the YFPM is inversely proportional to both the increment in fracture length and water injection rate, whereas it exhibits remarkable stability with increases in the fracture width. (3) In the YFPM, the displacement efficiency shows a rising trend as the fracture width and length decrease, while it positively correlates with an elevation in the water injection rate. (4) The effect of the bifurcation angle on breakthrough time and displacement efficiency in the YFPM is notably directed by the water injection direction, and the water saturation in porous media with a 15° bifurcation angle attains a water saturation level approximately 6.76% greater than that in porous media with a 45° bifurcation angle. (5) When the water injection rate changes from low (0.1 mm/s and 1 mm/s) to high (5 mm/s and 10 mm/s), the displacement in the YFPM changes from a combination of capillary and viscous fingering to viscous fingering, and the difference in water saturation can reach nearly 71%. This study will help to understand the oil–water displacement law during the exploitation of fractured reservoirs, and guide fracturing transformations and oil and gas extraction.