bar at the separator, although the first stage separator could operate at higher pressure c. 250 bar. Modern oil recovery practice may place a hydro-cyclone to replace the temporary GOSP, allowing the water to be removed immediately and re-injected into the reservoir. The hydro-cyclone will vary the flows according to the water content and can also separate condensate from the gas where separate storage and export can be provided for the products close to the production well (e.g. on offshore platforms). Contaminants Crude oil leaving the well may contain quantities of sulfur (e.g. hydrogen sulfide and thiols) and/or carbon dioxide, and is known as "sour" crude. The gas–oil separator will typically partition the hydrogen sulfide and carbon dioxide preferentially into the vapor or gas phase, where it may be further treated. The most usual "crude sweetening packages" use amines to remove the sulfur and CO2 content. Crude that contains water is called "wet", and the water can then be bound in an emulsion in the crude to allow pumping through a pipeline. The crude is processed and treated to make it acceptable for the entry and transportation specification of the pipeline, before it can be transported to a refinery for processing. Phase separation It is often appropriate to separate gases and liquids for separate processing. This also involves the separation of oily and water liquid phases. Gas recovery In the past, and in some places today, the gas is considered a waste product and was flared off (burned). Collecting the gas reduces carbon emissions, and produces a marketable commodity. See also Oil platform Oil production plant Oil refinery Petroleum Petroleum industry (Oil industry) Upstream (petroleum industry) References External links The Gas-Oil Separation Process Petroleum technology