Tertiary oil production

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Enhanced Oil Recovery (EOR) or tertiary oil recovery (also Tertiary Oil Recovery TOR) is a term for oil extraction techniques thatenable an oil yield that goes beyond that which can be achieved with primary and secondary methods.

For the primary and secondary methods of oil production, the yield is 20 to 40%. By using various techniques of the tertiary methods, the oil yield can be increased to 30–60%.

Methods

There are various methods of EOR, for example the injection of gases, chemicals , mainly surfactants , or microorganisms , as well as ultrasound stimulation and the action of heat, for example by injecting hot water vapor .

Gas injection

Gas injection is a commonly used method. In this process, gas is fed into a borehole under high pressure in order to push the oil to the surface. In addition to the purely mechanical effect of the gas, there are also positive effects due to a reduction in viscosity . These are due to the fact that the gas partially dissolves in the oil and thus reduces its viscosity. Commonly used gases are carbon dioxide (CO 2 ), nitrogen (N 2 ) and natural gas . The link between CO 2 injection and CO 2 capture is being tested in Canada in particular.

Injection of chemicals

Different types of chemicals with different modes of action are used to increase the yield.

Polymer flooding (= viscosity flooding ): Water-soluble polymers are added to the injected water in order to increase its viscosity. The detachment of the oil from the reservoir rock and its displacement is thus mechanically promoted.

Surfactant flooding (= detergent flooding ): The addition of surfactants ( detergents ) to the injected water has the effect that the crude oil is detached from the solid matter in the storage rock by changing the surface tension and thus mobilized.

Ultrasound techniques

Various ultrasound techniques have been proposed. The drilling head is to be modified in such a way that an ultrasonic vibration is transmitted piezoelectrically to the storage rock in order to enable the oil droplets to be released.

Injection of microorganisms

Injection of microorganisms with an oil-mobilizing effect is not widely used but is currently being intensively researched. On the one hand, microorganisms that form biosurfactants , sometimes even from long-chain constituents of petroleum, and on the other hand, those that generate gases, such as CO 2 (see above gas injection) are effective . Genetically modified microorganisms are also tested. The microorganisms are injected together with nutrients, such as carbohydrates. Attempts are also being made to promote the growth of the bacteria naturally occurring in the reservoir rock by feeding in nutrients and thereby causing the oil to detach.

Another approach is the use of microorganisms, which break down the long-chain alkanes found in crude oil into short-chain ones and thus reduce the oil's clogging during production.

Thermal extraction

In the case of thermal extraction, for example by injecting superheated steam, the lowering of the viscosity of the crude oil associated with heating is in the foreground.

Costs and benefits

The cost-benefit analysis of the EOR methods depends on the current oil price . In times of relatively low oil prices, tertiary methods are usually not used. In times of high oil prices, however, profit can be up to US $ 100 per tonne of crude oil.

Individual evidence

  1. ↑ Enhanced Oil Recovery Scoping Study (PDF; 2.2 MB) www.energy.ca.gov. Retrieved November 8, 2009.

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