Enhanced Oil Recovery

Most of the easier-to-produce oil has been recovered by conventional methods, also known as primary and secondary recovery techniques.Heavy crude oil, as opposed to light crude oil, has a higher density, viscosity, and specific gravity and does not flow easily under normal reservoir conditions.Enhanced oil recovery methods have been developed in order to maximize oil production and recovery by lowering viscosity and increasing the sweep efficiency.Thermal enhanced oil recovery is used to recover heavy crude oil in the United States, Canada, and Venezuela using heat and combustion.According to the U.S. Department of Energy, oil is extracted in three steps: primary recovery, secondary recovery, and enhanced oil recovery.Primary recovery involves natural mechanisms, such as the pressure in the reservoir or gravity, to push oil to a wellbore where it is pumped to the surface, resulting in a recovery of about 10% of the total oil in the formation.Secondary recovery is the injection of fluids, such as water or gas, to displace the oil, recovering 20 to 40 percent of the original oil.Primary and secondary methods are used to recover light crude oil, which is less dense and viscous than heavy crude oil and therefore easier to recover.Enhanced oil recovery (EOR), the final phase, combines primary and secondary recovery techniques to create a highly effective method of oil production, extracting 30 to 60% of the oil in a field. THERMAL ENHANCED OIL RECOVERYThermal enhanced oil recovery, or thermal EOR, uses heat as a mechanism to drive oil in a field to a wellbore for production.The concept of oil recovery typically involves the creation of a pressure gradient within the formation.Pressure drives the oil to the production wells to be pumped to the surface.In the case of thermal EOR, increasing the temperature of the formation using a variety of steam injection methods lowers the viscosity of heavy crude oil, allowing the oil to flow easily towards the production well.Thermal methods account for 40% of EOR in the United States and are predominantly in California (U.S. Dept. of Energy).The main methods of thermal EOR are cyclic steam stimulation (CSS), steam flooding, and in situ combustion. Cyclic Steam Stimulation (CSS)Cyclic steam stimulation (CSS) is commonly used in Canada to recover bitumen from oil sands.Bitumen, more popularly known as asphalt, is a highly viscous liquid or semi solid form of petroleum that is found deep beneath the Earth's surface.Its location makes it difficult to mine.The first phase of CSS is steam injection.Steam is injected through a wellbore over the course of weeks to increase Abstract: Primary and secondary methods of oil recovery are mainly used to recover the lighter, less viscous crude oil.Thermal enhanced oil recovery is popular method of extracting the harder-to-obtain heavy crude oil.The primary concept of thermal enhanced oil recovery is to lower the viscosity of the heavy crude oil with heat.Lowering the viscosity gives the crude oil mobility to move towards the production well.The main methods of thermal enhanced oil recovery include cyclic steam stimulation (CSS), steam-assisted gravity drainage (SAGD), and in-situ combustion.Environmentally friendly methods of thermal enhanced oil recovery include solar power.The other methods of enhanced oil recovery are gas and chemical injection.