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Pressure gradient fluctuates substantially, rapidly, and sometimes wildly, in foam flow through the porespace of rock, by as much as +/- 25%, as illustrated in the first two figures (Salazar-Castillo and Rossen, 2020). The cause is the shifting capillary resistance to movement of liquid films, or lamellae, between bubbles in the irregular porespace (Rossen, 1990). The third figure below shows the curved shapes of a lamella as it moves through a 2D pore. The changing curvature of the lamellae causes changing pressure difference between the bubbles on either side. The fourth figure shows the pressure difference across the lamella as it advances. Fluctuating pressure gradient results from the changing pressure difference across individual films, the trapping and mobilization of bubbles, shifting flow pathways through trapped gas, and coalescence and regeneration of foam as it flows. They indicate that gas mobility, and possibly phase saturations, fluctuate during "steady-state" foam flow. This fluctuation in mobility is not yet accounted for in numerical simulation models of foam flow, nor are the implications of these fluctuations.
We examine coreflood data to estimate the magnitude of the fluctuations in pressure gradient and of the time scale over which these fluctuations occur. We then estimate the fluctuation in gas mobility and phase saturations that correspond to the fluctuation in pressure gradient.
These fluctuations could have implications for foam generation and propagation in field applications. We discuss these implications.
| References | Rossen, W.R., J. Colloid Interface Sci. 139, 457-468 (1990). https://doi.org/10.1016/0021-9797(90)90118-8 - - - - - Salazar-Castillo, R., and Rossen, W.R., SPE Journal 25 (2020). https://doi.org/10.2118/201204-PA |
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| Country | Netherlands |
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