Why Is Enhanced Oil Recovery Necessary?

Enhanced Oil Recovery (EOR) is necessary because conventional extraction methods typically leave 60-80% of oil trapped within reservoirs. By contrast, EOR techniques can access much of this remaining oil to meet global energy demands.

The importance of EOR grows as easily accessible oil reserves continue to deplete worldwide. It’s a critical approach for energy companies seeking to maximize production from existing fields rather than relying solely on new discoveries.

This guide explores why this is the case and covers:

• Key benefits of EOR
• Common EOR methods
• Key economic and environmental considerations

The Limitations of Conventional Oil Recovery Methods

Traditional oil recovery methods cannot extract the majority of oil present in reservoirs.

Primary recovery, which relies on natural reservoir pressure, typically only extracts 10-15% of the original oil in place. Secondary recovery methods like water flooding may increase this recovery to 20-40%.

This limited extraction efficiency means significant oil resources remain trapped underground. These remaining oil reserves amount to billions of barrels of potential energy that would otherwise go unused.

The physics of oil extraction explains these limitations. Specifically, oil molecules often adhere strongly to reservoir rock surfaces due to capillary forces, and oil can become trapped in small pores within the rock structure.

Conventional methods lack the mechanisms to overcome these natural forces. The fluid dynamics within reservoirs are complex, with oil, water, and gas interacting in ways that can inhibit effective extraction.

As easily accessible reservoirs become increasingly scarce, the industry must turn to more sophisticated approaches – like EOR

Key Benefits of Enhanced Oil Recovery

Enhanced Oil Recovery significantly increases the amount of extractable oil from existing reservoirs, typically enabling the recovery of 30-60+% of the original oil in place. This substantial improvement unlocks billions of additional barrels of oil production globally.

EOR also extends the productive life of mature oil fields by several decades. This extension provides economic benefits to both operating companies and the communities that depend on oil production for their livelihoods.

Other notable benefits include:

• Revival of production centers: many oil fields considered “depleted” under conventional recovery methods contain significant untapped potential. EOR transforms these seemingly exhausted assets into valuable production centers once again.
• Reduced environmental impact: by maximizing recovery from existing fields, EOR reduces the need for new exploration and development, thereby minimizing overall environmental impact.
• Carbon sequestration:  certain EOR methods, particularly CO₂ injection, offer the dual benefit of oil recovery and carbon sequestration. 

The last benefit on the list is particularly important. The U.S. Department of Energy estimates that 20 billion tons of captured CO₂ could produce 67 billion barrels of economically recoverable oil through EOR while permanently storing the carbon dioxide underground.

This approach is an important bridge technology in the transition to lower-carbon energy systems. It allows continued oil production while addressing some climate concerns through carbon capture.

EOR operations contribute significantly to domestic energy security. With approximately 2-3% of U.S. oil production coming from EOR projects, these techniques help reduce dependence on imported energy.

Primary Enhanced Oil Recovery Methods

Thermal Recovery Techniques

Thermal recovery is particularly effective for heavy, viscous oils that resist flow under normal conditions. This method works by introducing heat into the reservoir to reduce oil viscosity and improve flow characteristics.

Steam injection is the most common thermal technique. The way it works is straightforward: high-temperature steam heats the oil in the reservoir, making it less viscous and more mobile for extraction.

In cyclic steam stimulation, steam is injected into a well for a period, followed by a soaking phase, then production. This cyclical approach proves effective for certain reservoir conditions.

Steam flooding involves continuous steam injection through dedicated wells while production occurs through separate wells. This creates a steam front that drives oil toward production wells.

In-situ combustion is another thermal approach where air is injected and a portion of the oil is burned underground. The resulting heat reduces the viscosity of the surrounding oil, making it easier to extract.

These thermal methods have proven particularly valuable in heavy oil fields around the world. Without thermal EOR, vast heavy oil reserves in places like Canada, Venezuela, and California would remain largely unrecoverable.

Gas Injection Methods

Gas injection EOR techniques work by introducing gases that interact with reservoir oil to improve recovery. These methods are often applied in deeper, lighter oil reservoirs.

CO₂ injection has become increasingly popular, as carbon dioxide becomes miscible with oil under certain pressure conditions. This miscibility effectively dissolves the CO₂ in the oil, reducing viscosity and causing the oil to expand and flow more easily.

Nitrogen and natural gas are also used as injection gases in appropriate reservoir conditions. These gases can maintain reservoir pressure while also creating favorable flow conditions for oil recovery.

Currently, there are approximately 375 EOR projects operating globally, with gas injection methods accounting for a significant portion of the estimated 2 million barrels per day of oil produced through enhanced recovery.

Chemical Flooding Approaches

Chemical flooding involves adding special compounds to injection water to improve oil recovery. These chemicals modify the interactions between oil, water, and reservoir rock. Common methods include:

• Polymer flooding: increases the viscosity of injection water, improving the efficiency of the displacement process. This helps prevent water from channeling through the reservoir and bypassing oil.
• Surfactant flooding: reduces the interfacial tension between oil and water, allowing oil droplets to detach from rock surfaces. This technique is particularly effective in reservoirs where oil adheres strongly to rock.
• Alkaline flooding: works by creating natural surfactants within the reservoir through chemical reactions. This cost-effective approach can work well in reservoirs containing acidic crude oil components.

Combined approaches like Alkaline-Surfactant-Polymer (ASP) flooding leverage multiple mechanisms simultaneously. These integrated methods often achieve higher recovery rates than single-chemical approaches.

Chemical EOR becomes increasingly important for moderately depleted fields where neither thermal nor gas injection methods prove suitable. The tailored nature of chemical formulations enables customization to specific reservoir conditions.

Economic Considerations of Enhanced Oil Recovery

The global EOR market reached approximately USD 49.8 billion in 2024 and continues to grow steadily. This growth reflects the increasing necessity of these techniques as conventional production declines.

EOR projects typically require significant initial investment but can deliver strong returns over extended production periods. The economics improve when existing infrastructure can be used as opposed to new development.

Oil price fluctuations significantly impact EOR project viability. Higher oil prices generally make more technically challenging EOR projects economical, while price drops may temporarily reduce implementation.

Many governments offer tax incentives for EOR projects, particularly those involving carbon capture and storage. These incentives recognize both the energy security and potential environmental benefits of advanced recovery techniques.

EOR techniques must be carefully matched to specific reservoir characteristics. The wrong approach can result in poor recovery and wasted resources, which calls for detailed reservoir characterization before implementation.

The Environmental Impact of Enhanced Oil Recovery

EOR project designs are increasingly driven by environmental considerations like:

•  Water usage
• Potential chemical impact
• Surface disturbance

CO₂-EOR projects provide an opportunity to reduce the carbon intensity of oil production, as they store significant amounts of carbon dioxide underground. That said, the combustion of recovered oil typically releases more CO₂ than is stored in the process.

As the global energy transition progresses, EOR remains an important bridge technology. It maximizes recovery from existing assets while the world develops alternative energy sources.

The necessity of EOR continues to grow as global energy demand rises and conventional production declines. These advanced techniques will remain vital components of the energy landscape for decades to come.

Lawrence Haynes

Currently serving as Marketing Director at WestAir Gases & Equipment in San Diego, CA Lawrence leverages his expertise in industrial gas solutions and equipment marketing. With a proven track record in cross-industry marketing strategy, he brings a specialized experience in content development, marketing automation, and partner relations to the industrial gas sector.