Only a fraction of the oil originally in place comes out under natural pressure. Recovery stages are the industry's strategy for steadily increasing that fraction over the life of a field.
Primary and secondary recovery together typically produce about 20–40% of the original oil in place. Tertiary recovery (EOR) can push total recovery to 30–60% or more, depending on the reservoir and method.
The three recovery stages
Production driven by the reservoir's own natural energy — pressure, dissolved gas, and gravity. As pressure falls, artificial lift is added, but only a modest fraction of the oil is recovered.
Injecting water (waterflood) or gas to maintain reservoir pressure and physically sweep oil toward producing wells. Primary plus secondary recovery typically yields about 20–40% of original oil in place.
Enhanced oil recovery uses thermal, gas, or chemical methods to mobilize oil left behind, raising total recovery toward 30–60% or more.
Enhanced oil recovery (EOR) methods
Tertiary recovery targets the large volume of oil that primary and secondary methods leave trapped in the pore space. The main EOR families are:
- Gas injection (CO₂) — the most common EOR method. Injected CO₂ swells the oil and lowers its viscosity and interfacial tension, helping it flow toward producers. Other gases are also used.
- Thermal — steam (and in-situ combustion) heats the reservoir to thin heavy, viscous oil so it flows. Thermal methods account for more than 40% of US EOR, concentrated in heavy-oil areas such as California.
- Chemical — polymers and surfactants improve sweep efficiency and reduce the forces holding oil in the pores. Chemical EOR is a small share of US production, on the order of 1%.
Each method is matched to the reservoir: thermal for heavy oil, CO₂ for lighter oil, and chemical where sweep or trapping is the limiting factor. Understanding porosity and permeability is central to predicting how well any recovery method will work.
Built by the team behind OpsFlo — field service & billing software for oilfield service companies. Capture tickets at the wellsite and bill in days, not weeks.
Frequently asked
Primary and secondary recovery together typically yield about 20–40% of the original oil in place. The exact figure depends on reservoir quality, oil properties, and how effectively injected water or gas sweeps the rock.
CO₂ (gas) injection is the most common enhanced oil recovery method. Injected CO₂ swells the oil and lowers its viscosity and interfacial tension, helping trapped oil flow toward producing wells.
Tertiary recovery can raise total recovery to roughly 30–60% or more of the original oil in place, depending on the reservoir and the EOR method applied — substantially above what primary and secondary recovery alone achieve.