Enhanced Oil Recovery

Enhanced oil recovery is used to recover stranded oil that remains in reservoirs after primary depletion.

Oil is first produced from reservoirs under primary recovery due to in-situ reservoir pressure aided by pumps. Secondary recovery generally occurs by a waterflood. Water is injected into the reservoir to physically displace the residual oil, which is subsequently recovered by adjacent production wells. The success of waterfloods depends on the permeability of the reservoir and the properties of the oil.

Tertiary recovery techniques are also referred to as enhanced oil recovery, or EOR. The three most common EOR techniques are heat injection, chemical injection, and gas injection. Heat injection enhances reservoir productivity by reducing crude oil's viscosity. Chemical injection, through the interaction of various chemicals with oil, decreases surface tension and capillary pressure within the reservoir. Gas injection is currently the most common EOR technique. The gas, usually carbon dioxide (CO2), displaces and mixes with oil to enhance productivity. CO2 injection is commonly referred to as CO2-EOR, and the term is often used interchangeably with EOR.

CO2-EOR has been successful in several fields around Wyoming, including Lost Soldier and Wertz fields and the Monell unit in the Patrick Draw field of the Greater Green River Basin, Salt Creek field in the Powder River Basin, and Beaver Creek field in the Wind River Basin. Grieve field, in the Wind River Basin, began CO2-EOR operations in early 2013. Most of these fields underwent secondary waterflooding prior to CO2-EOR.

For more information on enhanced oil recovery in Wyoming, see the University of Wyoming’s Enhanced Oil Recovery Institute website.

schematic diagram of enhanced oil recovery with CO2 and water
Schematic diagram of enhanced oil recovery with CO2 and water. [Credit: WSGS]


Rachel Toner, rachel.toner@wyo.gov

Derek Lichtner, derek.lichtner@wyo.gov