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Enhanced Oil Recovery: Fireflooding

In situ combustion, also known as fireflooding, is a method used to produce heavy oil that cannot be extracted through conventional means. It involves igniting the oil reservoir by lowering a heater into an injection well and introducing air, which creates a combustion zone that advances through the formation toward production wells. This combustion zone provides steam and gas drives to displace the oil towards the production wells where it is brought to the surface. Water is sometimes alternately or simultaneously injected with air to generate more steam and reduce the air requirements, helping to counter the overriding effect of lighter vapors rising upwards in the reservoir.

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Abderrahim HAMDAOUI
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80 views2 pages

Enhanced Oil Recovery: Fireflooding

In situ combustion, also known as fireflooding, is a method used to produce heavy oil that cannot be extracted through conventional means. It involves igniting the oil reservoir by lowering a heater into an injection well and introducing air, which creates a combustion zone that advances through the formation toward production wells. This combustion zone provides steam and gas drives to displace the oil towards the production wells where it is brought to the surface. Water is sometimes alternately or simultaneously injected with air to generate more steam and reduce the air requirements, helping to counter the overriding effect of lighter vapors rising upwards in the reservoir.

Uploaded by

Abderrahim HAMDAOUI
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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IN SITU COMBUSTION

or "Fireflooding"

This method is sometimes applied to reservoirs containing oil too viscous or "heavy" to be produced by conventional means.
Burning some of the oil in situ (in place), creates a combustion zone that moves through the formation toward production
wells, providing a steam drive and an intense gas drive for the recovery of oil.

This process is sometimes started by lowering a heater or ignitor into an injection well. Air is then injected down the well, and
the heater is operated until ignition is accomplished. After heating the surrounding rock, the heater is withdrawn, but air
injection is continued to maintain the advancing combustion front. Water is sometimes injected simultaneously or alternately
with air, creating steam which contributes to better heat utilization and reduced air requirements.

Many interactions occur in this process, but the accompanying drawing shows the essential elements. The numbered
statements below correspond to numbers on the drawing.

1. This zone is burned out as the combustion front advances.


2. Any water formed or injected will turn to steam in this zone because of residual heat. This steam flows on into the
unburned area of the formation, helping to heat it.
3. This shows the combustion zone which advances through the formation.
4. High temperature just ahead of the combustion zone causes lighter fractions of the oil to vaporize, leaving a heavy
deposit of residual coke or carbon as fuel for the advancing combustion front.
5. A vaporizing zone that contains combustion products, vaporized light hydrocarbons, and steam.
6. In this zone, owing to its distance from the combustion front, cooling causes light hydrocarbons to condense and steam
to revert back to hot water. This action displaces oil, condensed steam thins the oil, and combustion gases aid in
driving the oil to production wells.
7. In this zone, an oil bank (an accumulation of displaced oil) is formed. It contains oil, water, and combustion gases.
8. The oil bank will grow cooler as it moves toward production wells, and temperatures will drop to that near initial
reservoir temperature.

When the oil bank reaches the production wells, the oil, water, and gases will be brought to the surface and separated - the
oil to be sold and the water and gases sometimes reinjected. The process will be terminated by stopping air injection when
predesignated areas are burned out or the burning front reaches production wells.

Notice in the accompanying illustration that the lighter steam vapors and combustion gases tend to rise into the upper portion
of the producing zone, lessening the effectiveness of this method. Injection of water alternately or simultaneously with air can
lessen the detrimental overriding effect.

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