There are several different types of oil recovery methods used in the petroleum industry. These methods are employed to extract oil from underground reservoirs and maximize the amount of oil that can be recovered. Here are some of the commonly used oil recovery techniques:
- Primary Recovery: Also known as natural depletion, primary recovery involves extracting oil from a reservoir using natural forces, primarily the reservoir’s own pressure. When the well is initially drilled, oil can flow to the surface due to the natural pressure difference between the reservoir and the wellbore. However, the production rate decreases over time as the reservoir pressure declines.
- Secondary Recovery: Secondary recovery techniques are employed to enhance oil recovery after primary methods have depleted the reservoir pressure. The most common secondary recovery method is water flooding, where water is injected into the reservoir to maintain pressure and displace oil towards the producing wells. Water flooding can improve oil recovery by pushing the oil towards the production wells.
- Enhanced Oil Recovery (EOR): EOR techniques are utilized when primary and secondary recovery methods are insufficient to extract a significant portion of the oil from a reservoir. EOR methods involve injecting fluids into the reservoir to improve oil displacement. Some commonly used EOR techniques include:a. Steam Injection: In this method, steam is injected into the reservoir to reduce oil viscosity, improve oil mobility, and increase reservoir pressure. This allows the oil to flow more easily to production wells.b. Gas Injection: Gas injection techniques involve injecting gases such as natural gas, carbon dioxide (CO2), or nitrogen into the reservoir. These gases help to maintain reservoir pressure, reduce oil viscosity, and displace oil towards production wells.c. Chemical Injection: Chemicals such as polymers, surfactants, and alkalis can be injected into the reservoir to alter the properties of the oil and improve its flow characteristics. This can enhance oil recovery by reducing interfacial tension, increasing sweep efficiency, or modifying rock wettability.d. Miscible Flooding: This technique involves injecting a fluid that is miscible (mixes completely) with the oil in the reservoir. It can be accomplished using gases like CO2 or hydrocarbon solvents. The injected fluid mixes with the oil, reducing its viscosity and improving displacement efficiency.
- Tertiary Recovery: Tertiary recovery methods are employed as a last resort to extract the remaining oil that is left after primary and secondary recovery techniques have been applied. Tertiary methods often involve more advanced and costly techniques, such as chemical flooding, steam-assisted gravity drainage (SAGD), or in-situ combustion.
It’s important to note that the choice of oil recovery method depends on various factors, including reservoir characteristics, oil properties, economics, and environmental considerations. Different methods or combinations of methods may be used depending on the specific conditions of each oil reservoir.