Onshore

The production of crude oil on-shore requires the use of water and/or steam, depending on the nature of the crude and recovery of the 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.

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.

This requires strong know-how, specific technologies and operating excellence - Veolia Water has these capabilities and many proprietary technologies to drive preferred economics and reliability.

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.

Potable Water: Potable water is simply water that is safe to drink. Potable water is free from polution, harmful organisms and impurities.

Produced Water steps
Primary Oil/Water Separation	Oil and gas production is a combination of hydrocarbons and contaminated water. Water content varies considerably due to the formation, age of the well and production technique. Before hydrocarbon can be transported and sold, water must be removed. Primary oil/water separation is the critical first step that utilizes the natural tendency of oil and water to separate over time.
Secondary Oil/Water Separation	Before produced water can be disposed or discharged, fine solids and suspended oil must be removed. Secondary oil/water separation utilizes gas flotation to remove contaminants.
Tertiary Oil/Water Separation	Tertiary separation is utilized downstream of flotation to remove the remaining traces of oil and suspended solids for disposal, discharge or beneficial use. Nut shell, sand or multimedia filtration is mostly used. The objective of tertiary separation is removal of fine particles and oil that might clog or foul subsurface injection formations.
Water Use	In general, onshore water meets subsurface injection quality requirements for disposal or production enhancement at this point. If produced water is needed for other uses such as steam flood for enhanced production, beneficial use, industrial use, or surface discharge, further treatment most probably is needed.
End Use	The ultimate use for produced water determines quality requirements. This point separates treatment for paths between packaged boilers used in SAGD operations and steam generated using Once Through Steam Generators (OTSG) and pretreatment for surface discharge.
High Silica?	Silica causes fouling in Once Through Steam Generators used to produce steam and membrane processes used to reduce dissolved solids prior to discharge. If silica concentration is too high, it must be reduced prior to further processing.
Silica Precipitation	Silica must be removed to prevent fouling in downstream equipment such as Once Through Stream Generators and membrane systems. Often warm lime softening is used to precipitate silica along with magnesium.
Fine Solids Removal	Lime softening often increases the amount of solids in water. Prior to further processing it is advisable to remove these solids through filtration. Removal of solids protects downstream ion exchange equipment used to remove remaining hardness.
Hardnes Removal - Ion Exchange	Warm lime softening will not get much deeper than 30 mg/l as CaCO3. For feeding Steam Generators or high pH RO, lower levels are required. The basis of ion exchange softening is the chemical reaction of ions in the water with the ion exchange resin. In general, calcium and magnesium need to be removed prior to further downstream processing to avoid scaling and fouling.
TDS Reduction	When the produced water has to be reused for a higher purpose than LP steam generation, for example as irrigation water, livestock water, process water, etc. treatment is required to reduce total dissolved solids (TDS) often referred to as salinity. Salinity can basically be removed in two ways; by electro dialysis and by Reverse Osmosis.
Final Adjustments	Prior to use as irrigation water, treated produced water must meet requirements for salinity and sodicity to ensure no damage to plants or soil will occur from its use. The concentrations of sodium, calcium and magnesium must be balanced to avoid any reduction of water infiltration rates.
Steam Generation - OTSG	Steam is often required for heavy oil or oil sands production. Steam heats oil underground lowering its viscosity. This allows oil to flow to production wells where it is lifted to the surface.
TDS Hardness Removal - Evaporation	Boiler operation requires very high quality water. To avoid scaling, calcium and magnesium hardness as well as dissolved solids must be removed. Evaporation is an alternative to conventional water treatment for boiler water preparation.
Steam Generation - Package Boilers or (HRSG)	Steam is often required for heavy oil or oil sands production. Steam heats oil underground lowering its viscosity. This allows oil to flow to production wells where it is lifted to the surface.

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Potable Water steps
Raw Water Feed	Raw water is typically obtained from either surface water sources or ground water sources. Before human consumption it must go through a series of treatment steps to insure it is safe to consume.
Organic Removal	To eliminate the possibility of potable water containing any residual hydrocarbons it is necessary to pass the water through an activated carbon filter.
Disinfection	Dinking water must be free of any microorganisms that may lead to illness. Disinfection is the process where pathogenic microorganisms are destroyed, thus providing protection.
Particultate Filtration	Raw water is typically obtained from either surface water sources or ground water sources. It is common to find suspend solids is the water from such sources. These solids must be removed prior to human consumption.

Onshore

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References

Total, Girassol offshore facility - Angola

Shell Chemical - Stanlow, United Kingdom

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