Coutret and Associates, Inc.

Improved Recovery

Improved recovery methods are artificial methods of increasing the recovery of oil and gas from a reservoir beyond what would have been recovered by natural forces. Improved recovery includes pressure maintenance, gas cycling, secondary recovery, and enhanced recovery.

Pressure maintenance is injecting fluid into a reservoir to keep the pressure dropping as oil or gas is produced. This method has several benefits. Operating cost may be lowered by delaying use of artificial lifts such as pumps. Total recovery from a reservoir may be increased by keeping the rate of production from dropping below the economic limit for a longer time. Keeping the reservoir pressure up can prevent gas from forming in an oil reservoir. Gas in an oil reservoir can inhibit the easy flow of oil. Maintaining reservoir pressure can prevent valuable light hydrocarbons from condensing in the reservoir.

Gas cycling methods are a subset to pressure maintenance. Rich gas is natural gas that contains a large amount of hydrocarbons that are liquid at or near atmospheric pressures and temperatures. These hydrocarbons are usually called condensate. In a rich gas reservoir, reducing the reservoir pressure can cause valuable light hydrocarbons to condense in the reservoir rather than on the surface. In gas cycling, the valuable liquids are stripped from the produced gas and the dry, processed gas is injected back into the reservoir. Additional condensate is recovered because rich gas is replaced by condensate free gas and the pressure of the reservoir drops more slowly, preventing condensation in the reservoir. In some instances, dry gas can scour condensate that has condensed in the reservoir. The injected gas is produced late in the life of the reservoir when the economically optimum amount of condensate has been recovered.

Secondary recovery refers to methods of improved recovery applied when a reservoir is at or near natural depletion. Secondary recovery involves injecting fluids, usually water, into a reservoir to push additional hydrocarbons to producing wells.

Enhanced recovery refers to less used methods of recovering additional hydrocarbons such as thermal recovery, and miscible floods. This category includes less used injection fluids such as polymers and CO₂.