Abstract
Foam can be used for gas mobility control in different subsurface applications. The success of foam-injection process depends on foam-generation and propagation rate inside the porous medium. In some cases, foam properties depend on the history of the flow or concentration of the surfactant, i.e., the hysteresis effect. Foam may show hysteresis behavior by exhibiting multiple states at the same injection conditions, where coarse-textured foam is converted into strong foam with fine texture at a critical injection velocity or pressure gradient. This study aims to investigate the effects of injection velocity and surfactant concentration on foam generation and hysteresis behavior as a function of foam quality. We find that the transition from coarse-foam to strong-foam (i.e., the minimum pressure gradient for foam generation) is almost independent of flowrate, surfactant concentration, and foam quality. Moreover, the hysteresis behavior in foam generation occurs only at high-quality regimes and when the pressure gradient is below a certain value regardless of the total flow rate and surfactant concentration. We also observe that the rheological behavior of foam is strongly dependent on liquid velocity.
Highlights
Foam can greatly reduce gas mobility in porous media and has been considered for a variety of environmental and industrial applications including aquifer remediation and improved-oil recovery[1,2,3]
It is our objective to investigate the effects of injection velocity and surfactant concentration on foam generation and hysteresis behavior as a function of foam quality
The surfactant concentration was gradually increased from the critical micelle concentration (CMC) to the higher surfactant concentrations and it was decreased again to the CMC
Summary
Foam can greatly reduce gas mobility in porous media and has been considered for a variety of environmental and industrial (subsurface) applications including aquifer remediation and improved-oil recovery[1,2,3]. At higher gas fractional flows, i.e. in the so-called high-quality regime, the steady-state pressure gradient (measured along the porous medium) becomes nearly independent of the gas superficial velocity[11, 15] In this regime, bubble size is very sensitive to injection rates and foam behavior is dominated by coalescence governed by the limiting capillary pressure[11, 16, 17]. In contrast at lower gas fractional flows or low-quality regime, the bubble size is presumably fixed at roughly pore size and does not change with the injection rate[15, 18] At this regime the pressure gradient is nearly independent of the liquid superficial velocity. In the second set of experiments, both the total injection velocity and the foam quality are kept constant, while the surfactant concentration is gradually varied
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