An holistic approach to water supply and effluent disposal
In upstream operations worldwide, oil companies produce three times as much water as oil, some 250m b/d. Determining the best option for water disposal is crucial. Water that comes to the surface in oil-producing wells is usually referred to a produced, or effluent water. Oil companies often re-inject that water back into oil reservoirs for reservoir-pressure maintenance, a technique called produced-water re-injection (PWRI). Alternatively, it may be discharged into the sea, rivers, or lakes, or into underground zones or aquifers at shallower depths than the source-oil reservoirs, known as disposal wells. In the upstream industry, water is also used for:
Water is also used in great quantities in downstream oil processing, creating large amounts of slightly contaminated wastewater, at many intermediate stages in pipeline hydro-testing and, among other uses, as tanker ballast waters.