Steam-Foam Mechanistic Field Trial in the Midway-Sunset Field

Abstract

A one-pattern, steam-foam mechanistic field trial was conducted in Section 26C of the Midway-Sunset field (upper Monarch sand). The test objectives were (1) to understand the mechanisms of steam diversion caused by foam under reservoir conditions, (2) to establish whether foam can exist in-depth away from the injection well, and (3) to measure incremental oil that can be attributed to foam. Surfactant was injected with steam and nitrogen continuously, and bottomhole injection pressure (BIHP) increased from 100 to 300 psig, indicating good foam generation. Better steam distribution across the injector's perforations occurred when foam was generated. Improvements in both vertical and areal sweep efficiency of steam were observed. Substantial temperature and gas saturation increases coincided with surfactant breakthrough and local reservoir pressure increases at observation wells. Complementary laboratory corefloods showed that foam generation could occur at low-pressure gradients, which are typical of in-depth conditions. Both laboratory and field data were interpreted as evidence that the in-depth presence of foam was the result of local generation wherever surfactant, steam, and nitrogen were present, rather than propagation of a foam bank generated near the injector. Some oil-production increase was also observed during the test; however, an accurate quantitative estimate of incremental oil owing to foam was difficult to establish.

Mobilization of trapped foam in porous media

“…This mobilization pressure drop is important because an extremely high mobilization pressure gradient limits the success of foam in EOR applications. If the required mobilization pressure gradient is too large, the foam is not an effective drive fluid for EOR, because there is a limit to what injection pressures can be used in the field, especially in places where the well-to-well distance is very long (Rossen and Gauglitz, 1990;Friedmann et aL, 1991). Different predictions for required mobilization pressure drop are presented in the literature.…”

Gas-bubble snap-off under pressure driven flow in constricted noncircular capillaries

“…For only curvature-driven rearrangement of liquid (Le., Cam = 0), a square pore with a constriction to body ratio greater than about 0. 4 does not snap-off. The pore is starved for liquid even though the static Roof criterion indicates that snap-off may occur.…”

Stability Analysis of Uniform Equilibrium Foam States for EOR Processes

“…Gas and surfactant solution can form multiple local-equilibrium (LE) states for the same injection conditions. It is commonly observed that at low superficial velocity there is "weak" or "coarse" foam, with a modest reduction in gas mobility (Ransohoff and Radke 1988;Rossen and Gauglitz 1990;Friedmann et al 1991Friedmann et al , 1994Tanzil et al 2002;Gauglitz et al 2002). Creation of strong foam is triggered by an increase in superficial velocity or pressure gradient; thereafter injection rate can be returned to the lower values and the strong foam remains at velocities for which weak foam was previously observed.…”