primary, secondary and enhanced oil recovery - Proven METHODologies
Primary oil recovery uses the natural pressure of the reservoir to push crude oil to the surface, typically extracting only 10% of the oil in the reservoir, but sometimes as much as 25%.
Essentially, primary oil recovery is the extraction of only that oil that rises to the surface naturally or through the use of lift devices or pump jacks. There is no other intervention involved in this phase, and at the end of the day, this phase of oil recovery only skims the surface of a reservoir’s potential.
During the primary recovery phase, oil and gas remaining in the reservoir often become trapped due to a reduction in natural pressure that enables the hydrocarbons to ﬂow to the surface. This can either slow production, or halt it completely.
Secondary oil recovery injects pressurized gas and water into the well to drive residual crude oil and gas that has remained after the primary recovery phase to the surface.
In this phase we’re looking at the extraction of an additional 25% to 30% of the oil in the reservoir.
GAS INJECTION SECONDARY RECOVERY
Gas is injected into the gas cap to sweep oil from the reservoir.
These gases may include natural gas produced with the oil, nitrogen or ﬂue gases. Gas may be injected at the start of the production phase (when primary recovery begins) or it may be injected after production has already begun to slow or has halted.
WATERFLOODING SECONDARY RECOVERY
Water is injected into the water zone to sweep oil from the reservoir.
Peak oil production from a waterﬂood happens when 100% of the produced ﬂuids have been replaced by water injection. Waterﬂooding produces ﬂuids containing both oil and water, and during the waterﬂooding process this balance changes in favor of oil over time.
This advanced form of gas injection is becoming the most popular method of EOR, and has been particularly successful in Texas and New Mexico.
Thermal recovery introduces heat to the reservoir, reducing the viscosity of the oil. Over many applications the oil becomes thinner thus enhancing its ability to ﬂow to the surface.
EOR - Chemical
In this process, chemicals are injected into a well to help free trapped oil within the reservoir. The process involves the injection of polymers into the reservoir. These polymers can increase the efﬁciency of secondary recovery waterﬂooding as well.
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