Microemulsion flooding tests

After a waterflood, the residual oil remaining in the porous reservoir is trapped by capillary forces. The corresponding interfacial tension between the aqueous and the oil phase is of a few mN rrT1 [109, 112-115]. Under these conditions, oil production is marginal and the water cut, on the other hand, becomes high [110, 113, 114]. Addition of surface-active substances (i.e. surfactants), however, can lower the interfacial tension by 3-4 orders of magnitude [109, 112-114, 117, 122, 124], which induces the production of more oil and lowers the water cut [113, 139]. Microemulsion flooding tests both at the laboratory and pilot scales have shown that the oil recovery could be more than 60% of the OOIP [ 110-114], which is about twice the current one. Nevertheless, most of the tests carried out in the field yielded an additional oil recovery of only 10-20% of the OOIP [114, 140], which indicates that the process still has to be improved. 

Putz, A., Chevalier, J.P., Stock, G. and Philipot, J.,. Field test of microemulsion flooding, Chateaurenard field France. J. Pet. Techol., (April 1981) 710-718. 

Low Tension Polymer Water Flood. In oil reservoirs, where the critical capillary number is relatively low, a significant amount of waterflooded residual oil can be displaced by surfactants of high efficiency even at two-phase flood conditions. This was demonstrated by the snccessfnl second Ripley surfactant flood pilot test in the Loudon field where approximately 68% of waterflooded residual oil was recovered by injecting a 0.3 PV microemulsion bank [63]. The microemulsion bank was followed by I.O PV of higher viscosity polymer drive. The chemical formnlation consisted of a blend of two PO-EO sulfates. 

---