Page 69 - Primer on Enhanced Oil Recovery

60 Primer on Enhanced Oil Recovery

Figure 7.8 Enhanced oil recovery Methods.

Table 7.1 Underplaying mechanisms for increased oil recovery.

Methods used Basic mechanism
Chemical methods Polymer flooding Improvement of sweep
Surfactant flooding efficiency; improvement of
Alkaline flooding displacement efficiency
Miscible methods Miscible solvent (LPG or Improvement of displacement
propane) Flooding efficiency
Enriched gas drive
High-pressure gas drive
CO 2 flooding
Flue gas injection
Inert gas (Nitrogen) injection
Thermal methods Steam injection Improvement of both sweep
efficiency and displacement
efficiency
In situ combustion

purposes. Waterflood with surfactants is a complex technology that requires
detailed laboratory testing in the preparation of a field development project. This is
a rather expensive technology and has been used only in a few large projects.
Alkaline flooding is used only for the formations containing certain types of oil
with a high acidic number.
Combined methods have the greatest potential for enhanced oil recovery for
fields containing low viscosity oils. Among these methods, water flooding by mix-
ing with CO 2 is probably the most promising.
Thermal methods are characterized by an injection into formation of thermal
energy in order to reduce the oil viscosity. Low viscosity makes oil more mobile
and this, in turn, increases the efficiency of oil displacement to the production
wells. Steam injection, used since the 1960s, is the most advanced and used of ther-
mal technologies for enhanced oil recovery. The steam injection efficiency can be
estimated with less uncertainty than any other EOR. Internal combustion, which is
currently in extensive development at the implementation stages, is usually applied