Downhole oil–water separation (DOWS) technology is an emerging technology that separates oil and

gas Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

from

produced water Produced water is a term used in the oil industry or geothermal industry to describe water that is produced as a byproduct during the extraction of Petroleum, oil and natural gas, or used as a medium for heat extraction. Produced water is the kind ...

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 the casing well. 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.

Overview

A DOWS system is installed at the bottom of an

oil well An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may ...

, where it separates oil and water in the

wellbore A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petrole ...

. 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 hydro-cyclones to mechanically separate oil and water, and the other relies on

gravity separation Gravity separation is an industrial method of separating two components, either a suspension, or dry granular mixture where separating the components with gravity is sufficiently practical: i.e. the components of the mixture have different specific ...

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 pump Progressive may refer to: Politics * Progressivism, a political philosophy in support of social reform ** Progressivism in the United States, the political philosophy in the American context * Progressive realism, an American foreign policy pa ...

s, and sucker rod pumps. Hydro-cyclone separators are usually used with the electrical submersible pumps because of higher drawdown created with an effective injection of water into the lower zone.

References

Petroleum technology {{petroleum-stub