In a recent test, a foaming surfactant diverted steam into the upper oil zones of a Morichal field well in eastern Venezuela. In prior cycles, the steam had entered thief zone intervals lower in the well.
The field trial was conducted by Lagoven SA, an affiliate of Petroleos de Venezuela SA (Pdvsa), Venezuela's state oil company.
Although results are preliminary, Lagoven said the injection phase was successful, and it is optimistic that during the production phase of the cycle additional oil will be recovered from the newly stimulated zones.
Lagoven said flowmeter logs clearly indicate all steam was diverted into the upper pay zone.
In this test, the surfactant-Chevron Chemical Co.'s Chaser SD1020-encountered conditions different than in previous tests. During steam injection, a strong foam was generated with a temperature greater than 360 F., injection pressure greater than 1,000 psi, and steam injection rate of more than 1,400 b/d.
Also, this was the first test, according to Chevron, in which the surfactant generated strong foam in a reservoir with an estimated oil saturation greater than 50%.
Lagoven said it and Pdvsa's other affiliates are evaluating new technologies such as foaming surfactants for increasing heavy oil production.
Venezuela's heavy oil is commonly produced from wells that are steamed for approximately 30 days every 2 years. A common problem with this cyclic steaming (steam soak) is the uneven distribution of steam, which results in large amounts of unrecoverable oil.
Foam injection is expected to divert steam to the low permeability, lower oil gravity intervals by reducing steam mobility in the high permeability, higher oil gravity intervals.
Lagoven expects additional Venezuelan field trials to begin later this year.
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