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Enhanced Oil Recovery

Steam Injection

What is Enhanced Oil Recovery (EOR) ?

• A generic term for increasing the amount of crude oil extracted from an oil reservoir

• Also referred to as ‘improved oil recovery’ or ‘tertiary oil recovery’

• Using EOR, oil extraction rate can exceed up to 60% compared to primary and secondary oil recovery methods (20-40% recovery)

Methods of EOR

• Gas injection methods• Chemical injection methods• Thermal methods– Steam injection– Fire flooding

Steam Injection

• One of the methods included in EOR

• Applies the use of steam for recovering oil

• Has several different forms but two main ones– Cyclic Steam Stimulation– Steam Flooding

Cyclic Steam Stimulation

• Also known as “Huff-and-Puff” method

• Sometimes applied to heavy-oil reservoirs

• Assists natural reservoir energy by lowering viscosity of oil

• Commonly used for a formation of oil-wells but can be applied to a single-well procedure

Cyclic Steam Stimulation (contd.)

• The cycle may be repeated until the recovery response becomes minimum due to decrease in pressure and increase in water production

• Accompanied by continuous steam-flooding to continue the supply of heat and to replace declining pressure of reservoir

Steam Flooding

• Most commonly used in heavy-oil reservoirs having high viscosity

• High-temperature steam is continuously ejected into the reservoir which,– Loses heat to formation of water and condenses– The hot water produced coupled with continuous

steam supply acts as a driving force to move the oil to the production wells

Advantages• Steam floods are easier to control than fire-floods

• Steam floods do not cause cracking of oil and no environmentally objectionable flue gases are produced

• Steam injection wells are subject to much lower temperature than fire injection wells

• Steam flooding can be applied to reservoirs containing high API gravity oils

• Flushing of liners and casing perforations, as well as the reduction of deposits that may build up in the wells

Disadvantages

• Heat losses are high through injection lines, wellbores and oil well formation

• Steam flooding requires large supply of high quality fresh water

• Steam injection can’t be performed at depths below 5000 ft because of high reservoir pressure

Economic Considerations

• Capital investment is lower

• Fuel consumption per barrel of oil produced is higher

References

• http://en.wikipedia.org/wiki/Steam_injection_%28oil_industry%29

• www.netl.doe.gov/technologies/oil-gas/publications/eordrawings/BW/bwsf.PDF

• www.netl.doe.gov/technologies/oil-gas/publications/eordrawings/BW/bwcyclic_stm.PDF

• www.most.gov.mm/techuni/media/PE_05045_2.pdf