Tuning capillary flow in porous media with hierarchical structures

Abstract

Immiscible fluid-fluid displacement in porous media is of great importance in many engineering applications, such as enhanced oil recovery, agricultural irrigation, and geologic CO2 storage. Fingering phenomena, induced by the interface instability, are commonly encountered during displacement processes and somehow detrimental since such hydrodynamic instabilities can significantly reduce displacement efficiency. In this study, we report a possible adjustment in pore geometry which aims to suppress the capillary fingering in porous media with hierarchical structures. Through pore-scale simulations and theoretical analysis, we demonstrate and quantify combined effects of wettability and hierarchical geometry on displacement patterns, showing a transition from fingering to compact mode. Our results suggest that with a higher porosity of the 2 nd -order porous structure, the displacement can keep compact across a wider range of wettability conditions. Combined with our previous work on viscous fingering in such media, we can provide a complete insight into the fluid-fluid displacement control in hierarchical porous media, across a wide range of capillary number from capillary-to viscous-dominated modes. The conclusions of this work can benefit the design of microfluidic devices, as well as tailoring porous media for better fluid displacement efficiency at the field scale.

Precise Tuning of Multiple Perovskite Photoluminescence by Volume-Controlled Printing of Perovskite Precursor Solution on Cellulose Paper

“…Later, the liquid flow rate through the pores becomes lower than the evaporation rate, thus the solution in the capillary cannot fill the pore volume and break up to separate the solution residue on the top surface and the solution layer below the surface (stage III). Such discontinuity of liquids driven by liquid displacement in porous channels has been reported previously. − At the final stage (stage IV), the solution dries up by molecular evaporation of the solvent.…”

Investigation of the Effect of Capillary Barrier on Water–Oil Movement in Water Flooding

“…Interaction between capillary and viscous effects plays a significant role in the flow instability and immiscible displacement and is verified by macroscopic capillary number with a critical value of Nca~1 [27]. Suo [28] pointed out that the displacement pat tern can be transitioned between capillary-dominated and viscous-dominated modes via the adjustment in pore geometry, capillary fingering in porous media with hierarchica structures can be suppressed by adjusting the pore geometry, and the weak capillary ef fects can enhance the displacement stability. The complex capillary pressure distribution and configuration of fluid during displacement in highly heterogeneous porous media were measured via image processing methods and the results can facilitate better under standing of fluid displacement process [29].…”

“…It can be seen from Figure 17a that there are large fluctuations of the pressure difference between the inlet and outlet before and after the breakthrough of the water phase at the low capillary number of 1.8 × 10 −4 and there are negative values of the pressure difference. This dramatic fluctuation can be explained by the instability induced by the strong capillary effects during a capillary-dominated displacement process at a low capillary number [28]. With the advancing of the water phase, small fluctuations of the pressure difference are observed, and the pressure difference is positive.…”

Influence of Emulsification Characteristics on the Pressure Dynamics during Chemical Flooding for Oil Recovery

“…Chemical flooding agents mainly include foam, polymer, alkali and emulsification oil flooding agents, etc. − The additional resistance caused by Jamin effect can increase the swept area when foam flows in formation porous media. However, the foam has the disadvantage of de-foaming in contact with oil, so the EOR is poor. , A polymer is used to increase the viscosity of the injected fluid and reduce the mobility ratio of injected fluid to crude oil to increase the swept area . But a long polymer chain would be severely fractured under the shearing action of formation, resulting in a good profile modification being achieved only in the near-wellbore zone. − Alkali can form surfactants with the acidic components of crude oil, so it can emulsify the crude oil in situ to form an O/W emulsion and be produced with subsequent fluid injection .…”

“…However, the foam has the disadvantage of de-foaming in contact with oil, so the EOR is poor. 17,18 A polymer is used to increase the viscosity of the injected fluid and reduce the mobility ratio of injected fluid to crude oil to increase the swept area. 19 But a long polymer chain would be severely fractured under the shearing action of formation, resulting in a good profile modification being achieved only in the nearwellbore zone.…”