Water Injection System

In order to maintain reservoir pressure especially in aging fields, enhanced oil recovery techniques such as water injection or water flooding are common practices. Source water can be produced water from oil fields, sea water, or water from other sources like rivers or aquifers. Water pretreatment is required to remove oxygen and other contaminants including oil and sediment.

Design

Depending upon the sources of injection water, the treatment steps are selected. Treatment is required to protect injection pumps and associated piping from erosion and to prevent plugging of the injection wells. Treatment steps include deoiling, solids removal and deaeration. Corrosion inhibitors are injected to protect piping. Biocides are used to prevent bacterial growth, which can contribute to the production of hydrogen sulfide in the reservoir and also block the pores in the rock.

For produced water, the water is cooled and deoiling is carried out followed by solids removal. At typical reinjection rates, significant oil losses would occur without this initial step. Filters are sometimes required for solids removal. Corrosion inhibitors and biocide injection is provided.

For sea water injection, pre-filtration to remove solid particles is done first. Subsequently, sea water flows through a deaeration tower where oxygen is removed from water. Oxygen must be removed from the water because it promotes corrosion and growth of bacteria. Oxygen scavengers are also added to the water. If the sea water is mixed with produced water, a scale inhibitor may be required.
The treated water is pumped using high pressure pumps to the injection wells.

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