It is estimated that almost half of all produced oil is produced by use of waterflooding.
Its a process used to inject water into an oil-bearing reservoir for pressure maintenance as well as for displacing and producing incremental oil after (or sometimes before) the economic production limit has been reached.
In the 1920s, the practice began of reinjecting the produced water into porous and permeable subsurface formations, including the reservoir interval from which the oil and water originally had come.
By the 1930s, reinjection of produced water had become a common oilfield practice.
By the 1970s, most onshore oil fields in the US, USSR, and China, for which waterflooding was the logical recovery process, were being produced by use of this technology in various well-pattern arrangements.
Waterflooding is carried out by pumping water into a series of injection wells and hydrocarbons production through the production wells.
Flooding, in general, is carried out to achieve any of the following goals, or combinations there of:
- reservoir pressure maintenance;
- disposal of connate water after separation from hydrocarbons;
- creation of a water-pressure regime for displacing hydrocarbons from injection wells to producing wells
Field flooding is used in small depth but large area formations.
The factors to consider include the cost of drilling new wells and the cost of transforming some production wells to the injection ones.
This is done on the basis of the minimal investment.
However, if it is necessary to increase the injection rate, a 7-point or a 9-point flooding schemes are usually used.
Waterflooding has been used successfully in oil fields of all sizes and all over the world, in offshore and onshore oil fields.
The use of water flooding can increase the oil recovery ratio by 10–30%.