Dry Combustion

Definition - What does Dry Combustion mean?

Dry Combustion is technique of in situ combustion in which only air or oxygen rich air mixture is injected into a formation. The first step of the combustion is igniting the oil. In some cases autoignition takes place if air is injected into the reservoir when the reservoir temperature is adequately high and oil is reactive. The ignition is induced with electrical heaters, injection of steam or pyrophoric agents and the downhole gas burners. After the ignition, combustion front gets propagated by the continuous flow of the air.

Petropedia explains Dry Combustion

During the Dry Combustion process there is a transition between different zones. There are seven zones starting from the injector:

  • Burned zone is a volume which is already burned and is filled with air and small amounts of the residual organic solids that are unburned. The alterations in minerals are possible as the zone is subjected to high temperatures.
  • Combustion front is the zone with the highest temperature. The zone is very thin where oxygen gets combined with fuel and results in high-temperature oxidation.
  • The cracking and vaporization zones are downstream of front. In this zone, crude is modified by high temperatures of the combustion process.
  • The steam plateau is a zone in which some hydrocarbon vapors condense. Many condense further downstream as the steam condenses.
  • The water bank is a zone that exists at leading edge of the steam plateau in which temperature is less than the steam-saturation temperature.
  • An oil bank is a zone that consists of most of the displaced oil that includes almost all of the light ends which is an output of thermal cracking.
  • The original reservoir is an undisturbed area where the gas saturation slightly increases due to the high mobility of the combustion gases.
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