Lattice Boltzmann Modeling of Spontaneous Imbibition in Variable-Diameter Capillaries

Rundong Gong, Xiukun Wang, Lei Li, Kaikai Li, Ran An and Chenggang Xian
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Rundong Gong: Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China
Xiukun Wang: Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China
Lei Li: College of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Kaikai Li: The No. 6 Oil Production Plant, Petrochina Changqing Oilfield Company, Xi’an 710018, China
Ran An: The No. 6 Oil Production Plant, Petrochina Changqing Oilfield Company, Xi’an 710018, China
Chenggang Xian: Unconventional Petroleum Research Institute, China University of Petroleum-Beijing, Beijing 102249, China

Energies, 2022, vol. 15, issue 12, 1-19

Abstract: Previous micro-scale studies of the effect of pore structure on spontaneous imbibition are mainly limited to invariable-diameter capillaries. However, in real oil and gas reservoir formations, the capillary diameters are changing and interconnected. Applying the lattice Boltzmann color gradient two-phase flow model and the parallel computation of CPUs, we simulated the spontaneous imbibition in variable-diameter capillaries. We explored the reasons for the nonwetting phase snap-off and systematically studied the critical conditions for the snap-off in spontaneous imbibition. The effects of pore-throat aspect ratio, throat diameter, and the pore-throat tortuosity of the capillary on spontaneous imbibition were studied. Through analyzing the simulated results, we found that the variation in the capillary diameter produces an additional resistance, which increases with the increase in the pore-throat ratio and the pore-throat tortuosity of a capillary. Under the action of this additional resistance, the snap-off phenomenon sometimes occurs in the spontaneous imbibition, which makes the recovery efficiency of the non-wetting phase extremely low. In addition, the main factors affecting this phenomenon are the pore-throat ratio and the pore-throat tortuosity, which is different from the conventional concept of tortuosity. When the snap-off does not occur, the spontaneous imbibition velocity increases when the throat diameter increases and the pore-throat aspect ratio is fixed, and when the period increases, i.e., the diameter changing rate decreases, the spontaneous imbibition velocity also increases. In addition, when the capillary throat diameter is fixed, a bigger pore diameter and a smaller period of sine function both inhibit the speed of spontaneous imbibition.

Keywords: spontaneous imbibition; variable-diameter capillary; lattice Boltzmann modeling; snap-off; pore-throat tortuosity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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