1. Primary Recovery:
- Primary recovery is the initial extraction of oil that flows naturally to the surface or can be extracted using artificial lift methods like pumps or gas lift.
- This method relies on the natural pressure within the reservoir to push the oil up the wellbore.
- Primary recovery typically allows for the extraction of only 10% to 25% of the total oil in a reservoir.
2. Secondary Recovery:
- Secondary recovery involves the injection of water, gas, or chemicals into the reservoir to maintain or increase pressure and improve oil flow.
- Waterflooding is a common secondary recovery method, where water is injected into the reservoir to displace the oil towards the production wells.
- Gas injection (e.g., natural gas or carbon dioxide) can also be used to maintain pressure and improve oil recovery.
- Secondary recovery methods can increase the recovery factor by an additional 20% to 40% of the total oil in a reservoir.
3. Tertiary Recovery (Enhanced Oil Recovery - EOR):
- Tertiary recovery involves the use of advanced techniques to extract additional oil from a reservoir beyond what can be achieved with primary and secondary recovery methods.
- There are several EOR methods, including:
- Thermal recovery involves injecting steam, hot water, or in-situ combustion (burning a portion of the oil underground) to reduce the viscosity of the oil and improve its flow.
- Gas injection: Injecting carbon dioxide (CO2), nitrogen, or other gases to improve oil viscosity and sweep efficiency.
- Chemical flooding: Injecting chemicals like polymers, surfactants, or alkaline solutions to alter the properties of the oil or reservoir and enhance oil recovery.
- Microbial enhanced oil recovery: Using microbes to produce gases or chemicals that can alter the properties of the oil and improve recovery.
- EOR methods can help extract an additional 5% to 25% of the total oil in a reservoir.
