Offshore

Similar to the production activities on-shore, the crude production activities Off-Shore require the use of water for the recovery of crude. The crude and water must then be separated to recover the crude and to be able to re-use the water or to dispose of the water. Also like on-shore production, the proper separation and treatment of this produced water is important for several reasons, including maximizing the recovery yield and protecting the production equipment and the environment.

In addition, it may be necessary to remove sulphates from sea water used for injection purposes. Crude naturally contains barium and strontium which react with sulphates to produce insoluble salts that can plug the reservoir and pipes, thus reducing production yield. Likewise, it may be necessary to reduce the salt content of the sea water prior to use on a production platform.

Veolia Water has proprietary technologies to achieve both of these requirements. In addition, Veolia Water has a very strong understanding of and capabilities with the required engineering specifications and disciplines to work on off-shore platforms. Size, weight, configuration, performance and reliability must all be integrally designed, built and installed to very exacting criteria. Veolia Water has a demonstrated list of such project accomplishments.

Produced Water: Produced Water describes water that is produced along with the oil and gas. Produced water originates from water that is trapped in permiable sedimentary rocks within the wellbore. Disposal of produced water can be problematic in environmental terms due to its highly saline nature.
Process Water: covers the wide range of boiler feed water, cooling water for heat exchangers or engine, chemicals dilution, etc... It should typically have a conductivity ranging from 0,1 to 50 uS/cm, with little to no hardness to avoid scaling in heating system. Oxygen and carbon dioxide should be removed to prevent corrosion

Depending on your application, the water quality requirements can vary:

Boiler feed water characteristic
Cooling water quality
Tap water or fresh groundwater are the most widely used source of water to produce process water.

Once demineralised, process water should be conditionned according to manufacturer's specification, usually up to pH 9 by adding caustic soda or ammonia.

Produced Water steps
Sea Water Intake	Offshore platforms use once through water for cooling crude oil, power generation, and various other engines, brakes and production processes as well as injection to maintain pressure in the reservoir. Seawater provides a limitless source of water for cooling and injection as well as a source for desalination and disinfection for drinking water. A seawater intake system should deliver water requirements without harming the ecology.
Sea Water Disinfection	Biological organisms are abundant in seawater and enter the cooling system through seawater intake systems. Without control, these organisms will create significant fouling in equipment.
Suspended Solids Removal	Prior to use in cooling circuits or downstream equipment, particles of suspended solids must be removed. Suspended solids will deposit on downstream equipment creating scale and corrosion sites.
Secondary Solids Separation	Prior to use for process water or injection water, suspended solids must be removed from seawater. Suspended solid removal will reduce fouling in downstream equipment.
Deaeration	Oxygen promotes bacterial growth and corrosion in downstream equipment. By removing oxygen, more economic materials of construction can be used; also, injection water has less ability to support sulfide producing bacteria that can sour oil production.
Potable Disinfection	Biological organisms are abundant in seawater and enter through seawater intake systems. Although biological control is applied as seawater is drawn from the ocean, further control of biological organisms is necessary prior to human consumption.
Clorine Removal	Chlorine residual can have a detrimental effect on downstream membranes. Prior to sulfate removal or SWRO, chlorine is removed with a chemical scavenger.
Sulfate Removal	Sulfate in seawater can form with barium and strontium in formation water to precipitate barium and strontium sulfates that can scale and possibly sour the reservoir. Specific membranes are used to remove sulfate from injection water to prevent sulfate precipitation.
Fine Solids Removal	Prior to sulfate removal or reverse osmosis, fine solids must be removed to prevent membrane fouling. Fine particles are typically removed using cartridge filtration.
Sulphate Removal?	If sulfate is present in seawater, it should be removed prior to injection to prevent barium and strontium sulfate formation in the reservoir.
Water Use	At this point there are two significant requirements for seawater - subsurface injection for enhanced production and process water for surface production needs. Most probably, further treatment is needed.
Sea Water Desalination (Watermaker)	Seawater contains 25,000 - 35,000 mg/l total dissolved solids (TDS). Drinking water standards generally limit chloride and sulfate to less than 250 mg/l each and TDS to less than 500 mg/l. Small self-contained desalination units (watermakers) are often used to produce potable water for offshore living quarters.
Pretreatment Needed?	Seawater desalination (SWRO) is a very sensitive membrane process. Silt density index (SDI) of less than 3 is necessary for proper membrane performance and life. If there is spare capacity in the sulfate removal package it can be used to provide very good water to the RO. If not, fine solids removal including multimedia filtration, cartridge filtration or a combination of both may be necessary.
Fine Solids Removal	Prior to reverse osmosis, fine solids must be removed to prevent membrane fouling. Fine particles are typically removed using multimedia filtration, cartridge filtration or a combination of both.

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Process Water steps
Sea Water Intake	Offshore platforms use once through water for cooling crude oil, power generation, and various other engines, brakes and production processes as well as injection to maintain pressure in the reservoir. Seawater provides a limitless source of water for cooling and injection as well as a source for desalination and disinfection for drinking water. A seawater intake system should deliver water requirements without harming the ecology.
Sea Water Disinfection	Biological organisms are abundant in seawater and enter the cooling system through seawater intake systems. Without control, these organisms will create significant fouling in equipment.
Suspended Solids Removal	Prior to use in cooling circuits or downstream equipment, particles of suspended solids must be removed. Suspended solids will deposit on downstream equipment creating scale and corrosion sites.
Secondary Solids Separation	Prior to use for process water or injection water, suspended solids must be removed from seawater. Suspended solid removal will reduce fouling in downstream equipment.
Deaeration	Oxygen promotes bacterial growth and corrosion in downstream equipment. By removing oxygen, more economic materials of construction can be used; also, injection water has less ability to support sulfide producing bacteria that can sour oil production.
Potable Disinfection	Biological organisms are abundant in seawater and enter through seawater intake systems. Although biological control is applied as seawater is drawn from the ocean, further control of biological organisms is necessary prior to human consumption.
Clorine Removal	Chlorine residual can have a detrimental effect on downstream membranes. Prior to sulfate removal or SWRO, chlorine is removed with a chemical scavenger.
Sulfate Removal	Sulfate in seawater can form with barium and strontium in formation water to precipitate barium and strontium sulfates that can scale and possibly sour the reservoir. Specific membranes are used to remove sulfate from injection water to prevent sulfate precipitation.
Fine Solids Removal	Prior to sulfate removal or reverse osmosis, fine solids must be removed to prevent membrane fouling. Fine particles are typically removed using cartridge filtration.
Sulphate Removal?	If sulfate is present in seawater, it should be removed prior to injection to prevent barium and strontium sulfate formation in the reservoir.
Water Use	At this point there are two significant requirements for seawater - subsurface injection for enhanced production and process water for surface production needs. Most probably, further treatment is needed.
Sea Water Desalination (Watermaker)	Seawater contains 25,000 - 35,000 mg/l total dissolved solids (TDS). Drinking water standards generally limit chloride and sulfate to less than 250 mg/l each and TDS to less than 500 mg/l. Small self-contained desalination units (watermakers) are often used to produce potable water for offshore living quarters.
Pretreatment Needed?	Seawater desalination (SWRO) is a very sensitive membrane process. Silt density index (SDI) of less than 3 is necessary for proper membrane performance and life. If there is spare capacity in the sulfate removal package it can be used to provide very good water to the RO. If not, fine solids removal including multimedia filtration, cartridge filtration or a combination of both may be necessary.
Fine Solids Removal	Prior to reverse osmosis, fine solids must be removed to prevent membrane fouling. Fine particles are typically removed using multimedia filtration, cartridge filtration or a combination of both.

Offshore

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References

Total, Girassol offshore facility - Angola

Shell Chemical - Stanlow, United Kingdom

LG, Lotte Daesan Petrochemical Co. Ltd - Daesan, South Korea