Chevron conducted a steam-foam trial in Midway-Sunset 26C to optimize the use of steam-foam, without the addition of a non-condensible gas, for improving profile control in a steam injection well. The field experiments were designed to find the optimal surfactant concentration and liquid volume fraction (LVF), or steam quality, for improving injection profiles with steam-foam. The effect of the total steam injection rate on the ability to generate a foam was also determined by using three chokes of different size. In all these tests, nitrogen was not added, because the goal was to develop a low-cost foam process. We also collected new laboratory data to determine the ability of low concentration foams to divert flow from higher to lower permeability sands.

Radioactive tracer measurements gave injection profiles with foam injection under ten different conditions, and five profiles were measured without foam injection. Downhole pressures were measured during these tests and under other conditions. Results show that increasing the steam LVF by blending water with the steam dilutes the surfactant, but improves foam generation and gives better profile improvement. Steam-foam improved the injection profile for concentrations greater than about 0.1 weight percent (wt.%) Chaser™ SD1020 at a steam LVF of 0.02 for the well tested. For surfactant concentrations below about 0.1 wt.%, the injection profile was changed but not improved. Tests showed that increasing the total steam injection rate from 180 to 630 BPD-CWE gave a larger pressure response due to foam for a range of surfactant concentrations. The test showed that profile improvement can be achieved with surfactant injected at about half the rate that was previously shown as necessary for in-depth foam applications, and this was accomplished without the addition of nitrogen.

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