Gravity override
and viscous fingering are inevitable in gas flooding
for improving hydrocarbon production from petroleum reservoirs. Foam
is used to regulate gas mobility and consequently improve sweep efficiency.
In the enhanced oil recovery process, when the foam is introduced
into the reservoir and exposed to the initial saline water saturation
and pH condition, selection of the stable foam is crucial. Salinity
and pH tolerance of generated foams are a unique concern in high salinity
and pH variable reservoirs. NaOH and HCl are used for adjusting the
pH, and NaCl and CaCl
2
are utilized to change salinity.
Through analyzing these two factors along with surfactant concentration,
we have instituted a screening scenario to optimize the effects of
salinity, pH, surfactant type, and concentration to generate the most
stable state of the generated foams. An anionic (sodium dodecyl sulfate)
and a nonionic (lauric alcohol ethoxylate-7) surfactants were utilized
to investigate the effects of the surfactant type. The results were
applied in a 40 cm synthetic porous media fully saturated with distilled
water to illustrate their effects on water recovery at ambient conditions.
This most stable foam along with eight different stabilities and foamabilities
and air alone was injected into the sand pack. The results show that
in optimum surfactant concentration, the stability of LA-7 was not
highly changed with salinity alteration. Also, we probed that serious
effects on foam stability are due to divalent salt and CaCl
2
. Finally, we found the most water recovery that was obtained by
the three most stable foams by the formula of 1 cmc SDS + 0.5 M NaCl,
1 cmc SDS + 0.01 M CaCl
2
, and LA-7@ pH ∼ 6 from
porous media flooding. Total water recovery for the most stable foam
increased by an amount of 65% compared to the state of air alone.
A good correlation between foam stability and foamability at higher
foam stabilities was observed.