Scotland
Contact
VWS Westgarth Office Contact


Orbital House
3 Redwood Crescent
East Kilbride
G74 5PR
UK


Tel:
+44 (0)1355 588 000
Fax: +44 (0)1355 588 001

Web: www.vwswestgarth.com
Email: graeme.orr@veolia.com

Veolia Water Oil & Gas Angola Contact:

Viana Park
Pavilhão nº1 Quarteirão 9
Estrada do Calumbo
Pólo Industrial de Viana
Luanda
República de Angola

Tel: +244 940 120 949
Tel: +244 949 229 399

Web: www.vwsoilandgasangola.com
Email: Enquiries.VWOGA@veoliawater.com

Produced Water

What is Produced Water?

Produced water is any water that is'produced' to the surface from an oil or gas reservoir along with the oil and gas. This water will be from one or more of the following sources:

  • Connate water present in the reservoir prior to production
  • Condensed water which is condensed out of the produced gas in the production tubing and topsides equipment
  • Injected water which has broken through from the injection wells to the producers

Produced water composition

Produced water is not a consistent substance. Both the physical and chemical properties of produced water vary widely depending on many factors including:

  • Reservoir geology
  • Hydrocarbon composition
  • Geographical location
  • Water injection history

Produced water will also change composition during the production lifetime of a reservoir, particularly in terms of water cut, and water salinity where water injection is employed. Most production wells produce dry oil at the beginning of the field life. Produced water volumes increase slowly as connate water begins to contaminate the oil. The water cut increases at an accelerated rate once the water/oil interface reaches the wells, this being known as "water breakthrough". Thereafter, the composition of the produced water begins to change to reflect an increase in the proportion of injected water. The water cut at which a well is regarded to be'watered out' is largely a matter of economics, but water cuts in excess of 95% can be economically viable in some circumstances. As oilfields age, water becomes the predominant fluid to be treated.

Why does it need to be treated?

The constituents of produced water are many and varied, the major substances being listed below:

  • Water
  • Hydrocarbons
    - Dispersed
    - Dissolved (BTEX)
    - Precipitated (waxes, asphaltenes)
  • Solids
    - Suspended (sands, scales, corrosion products)
    - Dissolved (salts, iron)
    - Gases (oxygen, carbon dioxide, hydrogen sulphide, hydrocarbons)
  • Production chemicals
  • Metals
  • NORM (Naturally Occurring Radioactive Minerals)

The contaminants need to be removed to enable the produced water to be re-used or disposed of.

What is done with it after treatment?

There are a number of options available for the disposal or reuse of produced water, each of which will have different water treatment criteria associated with it:

  • Surface disposal into the sea or into evaporation ponds, subject to local environmental regulations
  • Injection into a disposal well, either a watered out part of the reservoir or to a disposal formation
  • Reinjection for pressure maintenance, replacing sea/aquifer/river water as the source of water injection
  • Reuse for irrigation or as industrial process water

Produced Water Treatment Capabilities

The VWS Westgarth turnkey package

VWS Westgarth engineers, procures and project manages the complete produced water treatment system including:

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