A PRESENTATION ON WET
COMBUSTION
Introduction
• EOR ( Enhanced oil recovery) is a secondary method of oil recovery
and is based on the injection of the more exotic and correspondingly
more expensive fluids than water and non-miscible gases.
• There are 4 types of EOR methods, one among them is In-situ
Combustion which falls under the Thermal type of Enhanced recovery
of oil.
• Thermal type of EOR deals with – Increasing reservoir temperature,
Reducing oil viscosity, Increasing mobility.
In-Situ Combustion
• In-Situ combination is the oldest thermal recovery technique.
• Injection of air or air enriched oxygen.
• The air injected partially oxidises the hydrocarbon that gives rise to
combustion in reservoir which decreases the viscosity and increase
the overall mobility and Efficiency.
• For combustion to occur, the air must be able to flow in the reservoir
therefore the relative permeability of the rock to gas should be non
zero.
• This method can have both forward and backward process.
Wet Combustion
• We inject water along with the air.
• In reservoir, water is converted to steam to reuse the heat left behind
in the reservoir that will result in better recovery and the
effectiveness of the displacement process of the hydrocarbon.
• The water is injected with the air from the very start of the process.
• Wet Combustion is basically of two types• 1. Combination Thermal Drive (CTD)
• 2. Combination of forward Combustion and water flooding (COFCAW)
WET COMBUSTION
Combustion Thermal Drive
(CTD)
• Water-Air ratio (WAR) is very low
i.e., % of air more than water.
• Temperature should be high.
• The generated steam is converted
to super-heated steam.
• Temperature of combustion front is
constant or may increase.
• Area of flow wont be very high as
the super-heated steam cannot
travel higher distances.
Combination of forward combustion
and water flooding (COFCAW)
• Water-Air ratio (WAR) should be
high i.e., % of water is very high.
• Temperature should be low.
• Steam is converted to water not
to super-heated steam.
• It decreases the temperature of
the combustion front.
• Distance of movement of fluid is
very high.
• ADVANTAGES:
• Due to 𝐶𝑂2 in the combustion gases, oil viscosity is reduced and
therefore mobility increases.
• DISADVANTAGES:
• Pure 𝑂2 needs to be diluted to avoid excessively high combustion
temperature.
Drawbacks:
• Erosion and corrosion in the producing wells caused by acidic
components of waste gases.
• Damage of tubing, packer and casing as a result of thermal expansion
at high temperature.
• Production of water oil emulsion which are difficult to separate.
Criteria for Wet Combustion
• Reservoir Rock: Sandstone.
• Reservoir thickness: > 3 m.
• Porosity: >20%.
• Permeability: > 100 md.
• Initial Oil Saturation: >35 %.
• API gravity: <300 API(greater than 876 kg/𝑚3 ).
• Viscosity: <1000 cp.
Conclusion
• All though one of the oldest EOR method it is used sparingly because
of its low efficiency and other mechanical disadvantages.
• Due to presence of CO2 in the combustion gas the oil viscosity is
reduced and that helps in increased mobility.
• Erosion, damage to tubing and packer are few of the constant
headaches to deal with this process.