Heavy oil recovery methods include primary production, thermal production, and cold enhanced oil recovery (EOR). The selection of any of these methods will depend on many factors, including the stage of reservoir production, formation and fluid properties, reservoir geology, available production and transportation facilities, and the underlying heavy oil economics in a particular region.
Primary recovery is the first stage of heavy oil production in which natural reservoir energy, such as gravity drainage, displaces hydrocarbons from the reservoir into the wellbore and up to surface. But as reservoir pressure declines because of production, it is necessary to implement an artificial lift system such as a rod pump or electrical submersible pump. Cold heavy oil production with sand (CHOPS) is another primary recovery technique involving the continuous production of sand to improve the recovery of heavy oil from the reservoir.
Cold EOR is the recovery of heavy oil using nonthermal methods including production from horizontal and multilateral wells with water, solvent, and gas injection. Waterflooding is the most common nonthermal EOR approach which involves the injection of water to displace the heavy oil. Another nonthermal process known as vapor extraction (VAPEX) involves the injection of a solvent vapor to reduce the viscosity and improve the mobility of the heavy oil.
Thermal methods typically involve the injection of steam or hot water into the reservoir to improve the mobility of the heavy oil and provide a displacement mechanism. Thermal methods provide some of the highest recovery factors, but they also have the largest potential capital expenditure and operating costs.
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