Page 187 - Fundamentals of Reservoir Engineering

DARCY'S LAW AND APPLICATIONS 125

Surfactant flooding (Micellar Solution flooding)

Surfactants, or surface acting agents, when dissolved in minute quantities in water
have a significant influence on the interfacial properties between the water and oil
which it is displacing. The surfactant dissolves in the residual oil droplets thus raising
the saturation above the residual level and, in addition, the surface tension between
these enlarged oil droplets and the displacing water is very significantly reduced. Both
these effects are active in reducing the residual oil saturation and, in laboratory tests,
ninety percent residual oil recovery has been observed. The surfactants most
commonly used by the industry are petroleum sulphonates.

The above description of tertiary recovery mechanisms hardly "scratches the surface"
of the subject. For an excellent, simplified description the reader is referred to the set of
10
papers by Herbeck, Heintz and Hastings , which cover all aspects of the subject
including the vitally important economic considerations.

The above methods are described as tertiary in that they are capable of recovering
some, if not all, of the residual oil remaining after a waterflood. This does not mean,
however, that they must be preceded by a waterflood. Instead, the two can be
conducted simultaneously. In all tertiary recovery schemes, continuous injection of the
expensive agents is unnecessary. The fluids are injected in batches and frequently the
batches are followed by mobility buffers. For instance, to ensure stable displacement in
a surfactant flood, the chemical slug can be displaced by water thickened with a
polymer, the concentration of which is gradually decreased as the flood proceeds.

REFERENCES

1) King Hubbert, M., 1956. Darcy's Law and the Field Equations of the Flow of
Underground Fluids. Trans. AIME, 207: 222-239.

2) Darcy, H., 1856. Les Fontaines Publiques de la Ville de Dijon. Victor Dalmont,
Paris.

3) Klinkenberg, L.J., 1941. The Permeability of Porous Media to Liquids and Gases.
API Drill. and Prod. Prac.: 200.

4) Cole, F.W., 1961. Reservoir Engineering Manual. Gulf Publishing Co., Houston,
Texas: 19-20.

5) Geertsma, J., 1974. Estimating the Coefficient of Inertial Resistance in Fluid Flow
Through Porous Media. Soc.Pet.Eng.J., October: 445-450.

6) Campbell, J.M., 1976. Report on Tentative SPE Metrication Standards. Paper
presented to the 51st Annual Fall Conference of the AIME, New Orleans,
October.

7) van Everdingen, A.F., 1953. The Skin Effect and Its Impediment to Fluid Flow
into a Wellbore. Trans. AIME, 198: 171-176.

8) Craig, F.F., Jr., 1971. The Reservoir Engineering Aspects of Waterflooding. SPE
Monograph: