Thermal recovery of heavy oil is, to date, the most successful enhanced oil recovery process. Both steam stimulation and steam-flooding are widely used in California. They add almost 300,000 BOPD to the state's production. The Edison field, located on the eastern side of the San Joaquin valley, is just one of many heavy oil fields being produced by thermal recovery methods.

The Edison heavy oil sands are offshore-bar and alluvial-fan deposits. There are two textural controls on the reservoir quality of these rocks: (1) grain sorting and (2) the amount of dispersed silt and clay. The reservoir properties affected by rock texture are permeability and capillary pressure. Capillary pressure is particularly important, as it traps oil, controls oil saturation, and limits oil mobility.

The heavy oil at Edison is currently being produced by cyclic steam stimulation. The heat from the steam improves production by lowering the viscosity of the oil. Steam stimulation has doubled the recovery of heavy oil.

The enhanced oil recovery project at Edison was recently expanded to include a pilot steam-flood. The pilot project was designed with the aid of a computer model. The model was used to simulate the movement of steam through the reservoir and predict oil and water production. Simulated production trends indicate that the success of the project will depend on the oil saturation in the reservoir at flood start.

Steam injection into the pilot site began in February 1982. It is just one of many enhanced oil recovery projects being attempted by industry to try and offset a steady decline in new oil field discoveries.

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