SURFACTANT FLOODING
CHEMICAL EOR METHOD
Principles of Enhanced Oil Recovery
Surfactant Flooding
• Most large oil fields are now produced with some type of secondary pressure
maintenance scheme, such as water flooding. Water flooding can increase recovery from
around 1% to the 20-40% range. The remaining oil can be divided into two classes, firstly
residual oil to the water flood, and secondly oil bypassed by the water flood.
• A surfactant flood is a tertiary recovery mechanism aimed at reducing the residual oil
saturation in water swept zones. Typically a water flood that contacts 100% of a given oil
zone will leave a residual oil saturation of, say, 30%. This is the saturation at which the oil
phase relative permeability value is zero. The oil is immobile at this saturation because of
the surface tension between oil and water; the water pressure alone is unable to
overcome the high capillary pressure required to move oil out of very small pore
volumes.
Surfactant Flooding
• A surfactant offers a way of recovering the residual oil by reducing the surface tension
between the oil and water phases. A very low oil-water surface tension reduces the
capillary pressure and hence allows water to displace extra oil. If it is possible to reduce
the surface tension to zero, then theoretically the residual oil can be reduced to zero. In
practice the residual oil to even high concentrations is unlikely to lead to 100% recovery
of swept zones.
• One of the effects that will influence the success or failure of a surfactant flood is the
tendency of the surfactant being used to be adsorbed by the rock. If the adsorption is
too high, then large quantities of surfactant will be required to produce a small quantity
of additional oil.
• The ECLIPSE Surfactant Model does not aim to model the detailed chemistry of a
surfactant process, but rather to model the important features of a surfactant flood on a
full field basis.
Surfactant keywords
• Keyword Description Notes
• SURFACT - The model is activated by specifying this keyword in the RUNSPEC
section. (Obligatory)
• SURFST - Water-oil surface tension in the presence of surfactant (Obligatory)
Each table consists of two columns of data:
• 1 The surfactant concentration. lb/STB
• 2 The corresponding water-oil surface tension. lbf/in (FIELD),
• SURFVISC - Modified water viscosity (Obligatory). Each table consists of 2
columns of data:
• 1 The surfactant concentration in the solution. lb/stb (FIELD),
• 2 The solution water viscosity at this surfactant concentration and the reference pressure (entered with
the PVTW keyword).
• SURFCAPD - Capillary de-saturation data (Obligatory). Each table consists of 2
columns of data:
• 1 The log of the capillary number (range -20 to 20).
• 2 The miscibility function at the value of the log capillary number. A value of 0 implies immiscible
conditions and a value of 1 miscible conditions.
Surfactant keywords
• SURFADS - Adsorption isotherm (Optional) – describes the adsorption of
surfactant by the rock formation. Each table consists of 2 columns of data:
• 1 The local surfactant concentration in the solution surrounding the rock. lb/stb
(FIELD)
• 2 The corresponding saturated concentration of surfactant adsorbed by the rock
formation. lb/lb (FIELD)
• SURFROCK - Rock properties and adsorption model indicator (If
SURFADS is present) The data comprises tables specifying the rock
properties which are required for the Surfactant Model. Each table requires
the following items of data:
• 1 The adsorption index to be used for this rock type.
• Possible values for the adsorption index are 1 or 2.
• If a value of 1 is selected, then the surfactant adsorption isotherm is retraced
whenever the
• local surfactant concentration in the solution decreases.
• If a value of 2 is selected, then no surfactant desorption may occur.
• 2 The mass density of this rock type at reservoir conditions. lb/rb (FIELD)
Surfactant keywords
• WSURFACT - This keyword is used to specify the concentration
of surfactant in the injection stream of each well, when the
Surfactant Flood Model is active.
• 1 Well name, well name template, well list or well list template
• 2 The concentration of surfactant in the injection stream for the well.
lb/stb (FIELD)
Lab Tasks
• Run Surfactant data file in ECLIPSE software.
• Case 1: Reduce the injection rate from Base case rate i.e. 5000STB/D to
10000STB/D
• Case 2: Change the concentration of surfactant to 100.
• Case 3: Run basecase without Surfactant
• Compare and interpret the results.