Tertiary oil recovery reduces the oil's viscosityto increase oil production. Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to extract. Steam injection is the most common form of TEOR, and is often done with a cogeneration plant. In this type of cogeneration plant, a gas turbine is used to generate electricityand the waste heat is used to produce steam, which is then injected into the reservoir. This form of recovery is used extensively to increase oil production in theSan Joaquin Valley, which has very heavy oil, yet accounts for 10% of the United States' oil production
