What do you mean by Water Injection method?

The Water Injection way used in oil production is where water is injected back into the reservoir generally to raise pressure and so stimulate production. The Water injection wells are normally found offshore. This Water Injection method is used to raise oil recovery from an existing reservoir- Water is injected to force unrecovered oil out of reservoir rock and into close by oil wells. In general only 30% of the oil in a reservoir can be extracted. With the Water Injection that percentage will be superior and the production rate of a reservoir is guaranteed over a long period of time.