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Downhole oil-water separation (DOWS) technology is an emerging technology that separates oil and gas from produced water at the bottom of the well, and re-injects most of the produced water into another formation which is usually deeper than the producing formation, while the oil and gas rich stream is pumped to the surface. DOWS effectively removes solids from the disposal fluid and thus avoids injectivity impairment caused by solids plugging. Simultaneous injection using DOWS minimizes the opportunity for the contamination of underground sources of drinking water (USDWs) through leaks in tubing and casing during the injection process.
A DOWS system is installed at the bottom of an oil well, it separates oil and water in the wellbore. The oil rich stream is brought to the surface while the water rich stream is pumped into an injection formation without ever coming to the surface. A DOWS system includes many components but the two primary components are an oil/water separation system and a pumping/injection system used to lift oil to the surface and inject the water into a deeper formation. Two basic types of DOWS systems have been developed, one type uses hydrocyclones to mechanically separate oil and water and the other relies on gravity separation that takes place in the wellbore. Three basic types of pumping/injection systems are used with the DOWS technology. These include electrical submersible pumps, progressive cavity pumps and sucker rod pumps. Hydrocyclone separators are usually used with the electrical submersible pumps because of higher drawdown created with effective injection of water into the lower zone.