This paper presents field test results of sixteen steam soaked wells in which the injected steam was treated with two different surfactants selected in the laboratory as being the most suitable to be applied under Bolívar Coast Conditions. The laboratory research was done by Shell Laboratorium (Netherlands) and Intevep-PDVSA Research Center (Venezuela) and the main selecting criteria was the pressure drop measured in the porous media during steam foam flow tests.

The two steam foam formulations selected were, a long-chain alkyraryl toluene sulphonate (SURFACTANT 1) and a branch-chain alkyraryl benzene sulphonate (SURFACTANT 2). The SURFACTANT 1 was used in nine wells while the SURFACTANT 2 was injected in seven.

The stimulation mechanism of SURFACTANT 1 seems to be steam diversion to the less produced sands and for SURFACTANT 2 it appears to be a change of interfacial properties in the water-oil-rock system.

Although most of the steam foamed wells had not completed the production cycle, it can be concluded that 60% of them have presented positive response to steam foam. The initial oil rate response was equal to or slightly greater than that expected from a normal cycle; but steam foamed wells produced up to three times the additional cumulative oil expected (75,000 bls vs. 25.000 bls for a third cycle). This is due to the fact that the decline of the oil production rate was lowered to about 12% pa. which is indeed close to that of primary production.

The better oil production performances were obtained when the steam penetrated deeper into previously non productive layers. The maximum diversion registered was close to 90 feet as compared to 35 feet of the initial profile.

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