Produced water from oil and gas wells needs to be treated before disposal to meet regulatory emissions standards. Depending upon the region and the location for disposal, requirements for oil in effluent water concentration may be as low as 1 ppm.
Depending upon inlet oil concentration, space available and outlet oil specification, a combination of different equipment are used to achieve required guarantee for removal of oil from water.
Primary Oil Separation
Primary oil separation used for bulk removal of oil and water and is achieved by gravity settling units. These are used as a first step especially when the oil in water is above 1000 ppm, or when the oil effluent limit is greater than 50 ppm.
- Hydro cyclone
- Corrugated Plate Separator Unit
Secondary Oil Separation
After gravity settling, the oil remaining in the water is either dispersed as fine droplets or is heavy, with a density approaching that of water. Flotation units work by adding bubbles to the water, improving the density difference between oil and water and thus effecting more settling. Flotation units are used when oil effluent limits are between 15 and 50 ppm.
- Induced Gas Flotation Unit
- Dissolved Air Flotation Vessel
- Compact Flotation Unit
Tertiary Oil Separation
When very small amounts of oil in the effluent water are required, filtration is used. The fixed-bed process removes oil by straining the oil from the water and by adsorption of the oil within the bed. These filters can remove more than 80 percent of the oil in the influent, and can achieve oil effluents of 5-15 ppm.
- Nut Shell Filter
- Organic Clay Filter