Spatial and Temporal Quantification of Spontaneous Imbibition

Abstract

Spontaneous imbibition—the process of a wetting fluid displacing a nonwetting fluid purely by capillary forces—is a ubiquitous phenomenon in porous and fibrous materials. Here we present a new experimental method for quantification of spontaneous imbibition in geologic materials. This method makes it possible to perform spontaneous imbibition under elevated pressure conditions relevant to environmental and energy resource applications. Computed tomography imaging reveals a new time‐independent scaling relationship that describes local imbibition rates as a function of water saturation. Imbibition capillary pressure curves are calculated with this wetting‐phase pressure and flow rate characterization, with no assumptions about the functional form, end point behavior, or scaling factors. Calculated end point capillary pressure is nonzero, in agreement with recent pore‐scale measurements of capillary pressure of trapped nonwetting phase. This work provides a new approach and insights into trapping and remobilization of nonwetting fluids in CO2 storage reservoirs and contaminated groundwater aquifers.

Representative Elementary Volumes, Hysteresis, and Heterogeneity in Multiphase Flow From the Pore to Continuum Scale

“…Key to modeling this process during imbibition is having a finite, nonzero macroscopic capillary pressure at the residual non‐wetting saturation (Bech & Frykman, ; Jackson & Krevor, ; Zahasky & Benson, ), as shown in Figure S7. This finite capillary pressure is observed experimentally (Raeesi et al, ) but is often reduced to zero, or negative values by further reducing the wetting phase pressure relative to the non‐wetting phase.…”

“…However, there are data points with non-wetting saturations higher than that given by the trapping model, indicating enhanced capillary heterogeneity trapping, as seen in the experiments. Key to modeling this process during imbibition is having a finite, nonzero macroscopic capillary pressure at the residual non-wetting saturation (Bech & Frykman, 2018;Jackson & Krevor, 2019;Zahasky & Benson, 2019), as shown in Figure S7. This finite capillary pressure is observed experimentally (Raeesi et al, 2014) but is often reduced to zero, or negative values by further reducing the wetting phase pressure relative to the non-wetting phase.…”

“…Key to modelling this process during imbibition is having a finite, non-zero macroscopic capillary pressure at the residual non-wetting saturation (Jackson & Krevor, 2019;Bech & Frykman, 2018;Zahasky & Benson, 2019), as shown in SI Figure 7. This finite capillary pressure is observed experimentally (Raeesi et al, 2014), but is often reduced…”

Preferential Solute Transport in Low Permeability Zones During Spontaneous Imbibition in Heterogeneous Porous Media

“…Two‐end‐open free spontaneous imbibition experiments were performed using the experimental method recently described in Zahasky and Benson (2019) to isolate and analyze the mechanism of capillary‐driven solute transport. During these experiments, a 5.08 cm diameter by 10 cm long Berea sandstone core is loaded into a coreholder that enables a confining pressure, and thus no‐flow conditions, to be applied to the cylindrical faces of the sample.…”

“…The experimental marker size is proportional to relative permeability measurement error, specifically two standard deviations of measurement noise. (Right) Core‐average capillary pressure curve (red line) determined from a combination of mercury intrusion capillary pressure measurements (MICP) and 1D numerical capillary pressure calculations using the method of Zahasky and Benson (2019). The faint black lines are the scaled capillary pressure curves based on the streamtube permeability using the Levertt‐J capillary scaling methods (Alyafei & Blunt, 2018; Leverett, 1940; Tokunaga et al., 2013).…”