EOR represents enhanced oil recovery techniques that involve extracting additional oil from reservoirs after the primary and secondary methods of oil recovery have been used. EOR is critical in the energy sector because it aids in maximizing the extraction of oil resources from mature or depleted fields, and it does stretch their productive life while resource usage can be done with maximum efficiency. If you need more knowledge regarding the techniques of enhanced oil recovery, the wait is over. The British Academy for Training and Development offers high-quality oil and gas training courses. This article explains what EOR is, its importance, and the techniques used to recover oil that otherwise stays trapped in the reservoir.
An oil reservoir is basically a porous rock formation saturated with hydrocarbons. Primary recovery methods in a newly open reservoir depend on the natural pressure of the reservoir that pushes oil out to the surface. When this pressure is depleted, then secondary recovery methods, including water flooding or gas injection, are used to maintain pressure to push out as much oil as possible.
Primary and secondary methods of oil recovery techniques can recover only 20–40% of the oil in place. Most of the remaining oil is trapped within the reservoir due to characteristics like high viscosity, capillary forces, or complexities in geology. EOR techniques are developed particularly for residual oil, where recovery rates have reached 60% or more in some instances.
Here is the importance:
EOR allows a higher percentage of oil to be recovered from existing field reserves, which decreases the production of new exploration that causes ecological damage.
EOR helps prolong oil fields, thereby sustaining revenue streams for energy companies and governments.
Increased domestic oil production due to EOR reduces imports, enhancing energy self-reliance for many nations.
EOR techniques are typically energy-intensive, but as they often minimize the drilling of new wells, their environmental footprint in oil production tends to drop.
EOR can be divided broadly into three main techniques: Thermal, Chemical, and Gas Injection. Each is applied according to the reservoir's characteristics, such as temperature, pressure, oil viscosity, and rock properties.
Thermal EOR injects heat into the reservoir to decrease the viscosity of heavy oils, to make them easier to flow. It is more efficient in systems with high-viscosity oil, such as tar sands or heavy oil fields. Some Key Techniques:
The injection of steam into the reservoir is heated, making the oil easier to flow. Two of the most common techniques are cyclic steam stimulation (CSS) and steam flooding.
Air is injected into the reservoir, and part of the oil is ignited. Combustion produces heat, which lowers the viscosity of the remaining oil.
Thermal recovery is applied widely in countries, such as Canada and Venezuela, which have large reserves of heavy oil.
Chemical EOR comprises injecting specific chemical reagents into the reservoir to enhance oil displacement or decrease surface tension, thus allowing easier flow of the oil. Some of the Key Techniques:
The polymers are used to enhance the mobility of the displacing water and push more of oil towards the production wells through sweep efficiency.
Surfactants reduce the interfacial tension between oil and water to improve oil flow ability through the reservoir rock.
Alkaline fluids react with acidic contents in the oil to form soap-like species, hence reducing interfacial tensions.
Chemical recovery methods are commonly used in reservoirs with moderate permeability and trapped oil pockets.
Gas injection involves injecting gases such as carbon dioxide (CO2), natural gas, or nitrogen into the reservoir. These gases either mix with the oil to reduce its viscosity or maintain reservoir pressure to drive oil to the surface. Key Methods:
High-pressure injection of gases such as CO2, mixing with oil to form one phase, which is easily movable. Immiscible Gas Injection: Injected at pressures that are insufficient to mix but help to sustain the reservoir pressure and push oil towards the production wells.
CO2 injection is in wide application, especially in the United States as it offers in sufficient supplies of this gas from industrial origin.
As technology keeps on evolving, there is a development of new EOR techniques that are designed to meet challenging conditions in each reservoir:
application of microbes or their byproducts to degrade hydrocarbons that can reduce viscosity or generate gases to assist in oil recovery.
Engineering particles to change the reservoir properties, to enhance the fluid flow, and the injection of chemicals.
Combining two or more EOR techniques, for example, thermal and chemical techniques for better recovery efficiency.
EOR techniques are highly valuable, but challenges arise with them:
The processes are capital-intensive; they need highly advanced infrastructure and expertise.
Thermal recovery is among the methods that utilize massive quantities of energy and greenhouse gas emissions.
Every single reservoir has a unique setup. Making EOR techniques very specific to match a reservoir's conditions is very challenging.
In some EOR practices, extreme use of water and chemicals creates concerns in terms of sustainability.
The future of EOR oil and gas would be based on deploying advanced technologies and sustainable practices, with the following key trends being:
AI/machine learning applications for optimum efficiency and reduced costs in EOR operations. CCUS-Integration of CO2-EOR with carbon capture to enhance the recoverability of oil while reducing atmospheric CO2.
Development of environmentally friendly chemicals and utilization of renewable energy sources for processes such as steam generation.
Enhanced Oil Recovery is one of the essential aspects of current oil extraction since it involves extracting supplementary resources from exhausted or hard-to-recover reservoirs. Applying thermal, chemical, and gas injection methods, as well as new technologies, EOR ensures that valuable oil reserves are not wasted. Challenges like high costs and environmental impacts are not yet paved over, but EOR techniques are constantly evolving for an efficient, sustainable, and profitable landscape in oil recovery. Want to learn more about oil recovery methods? Why not enroll in oil and gas training courses in London? These courses are offered by the British Academy for Training and Development.