Is the process of removing crude oil from underground reservoirs so it can be refined and used. It involves several steps, technologies, and equipment, typically grouped into two main phases: primary extraction and secondary/tertiary recovery.
- Exploration and Drilling
Before oil can be extracted, companies must find it:
Seismic surveys (as discussed earlier) help locate potential reservoirs.
Once identified, a well is drilled using rigs to reach the oil-bearing rock.
If oil is present in commercial quantities, the well is prepared for production. - Primary Recovery (Natural Drive)
This is the first stage of extraction, where natural underground pressure forces the oil to the surface.
Mechanisms include:
Solution gas drive: Gas dissolved in oil expands and pushes oil up.
Gas cap drive: Gas in a cap above the oil forces it down toward the wellbore.
Water drive: Water beneath the oil pushes it upward.
In this phase, about 5–15% of the oil in place is recovered.
- Secondary Recovery
When natural pressure declines, secondary methods are used to maintain pressure:
Water flooding: Water is injected into the reservoir to push oil toward the production well.
Gas injection: Natural gas, CO₂, or nitrogen is injected to increase pressure and improve flow.
This can recover an additional 20–40% of the oil.
- Tertiary Recovery (Enhanced Oil Recovery, EOR)
Used when primary and secondary methods are no longer efficient.
Types:
Thermal recovery: Injecting steam to reduce oil viscosity (common in heavy oil).
Chemical injection: Using polymers or surfactants to improve flow.
CO₂ injection: Injected CO₂ mixes with oil, reducing viscosity and improving flow.
Tertiary methods can recover another 10–20% of oil.
- Surface Facilities
Once oil reaches the surface, it goes through:
Separation units: Separate oil, gas, and water.
Storage tanks: Hold crude oil temporarily.
Pipelines/trucks/ships: Transport crude to refineries.