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An Holistic Approach to Water Supply and Effluent Disposal


November 2008


Petroleum Economist in Fundamentals of Oil and Gas in the Middle East




Oil Plus Ltd

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K R Robinson


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:

  • Desalting crude oil – washing salt or highly saline water out of oil using fresh, or low-salinity water, often obtained from a shallow aquifer;
  • Water injection for reservoir-pressure maintenance, using sea, shallow-aquifer, or river water before implementing PWRI;
  • A process cooling, using sea, shallow-aquifer, or river water;
  • Process water – for wash-down, making up chemical solutions, such as drilling fluids; and
  • Potable water suitable for drinking for drilling rigs, construction camps, offices and accommodation, perhaps from shallow aquifers, rivers or desalination of seawater or aline aquifers.

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.