Gas oil separation plant
A Gas-oil separation package (GOSP) is a "package" used in the upstream oil industry. The package is fitted the well head after the choke valve and before the production manifold, and separates the crude oil from sediments, solids and sand (below using a filter) and gases and condensates to allow the crude to be pumped on the pipeline.
Beware that water need not be separated, causing the need to add chemicals so that the crude and water emulsifies. This process is then reversed at storage by adding demulsifiers that makes the water fall out, and can be tapped from the bottom of the tank. The gas and condensate are pumped on designated pipelines for this, while the sand and sediments require special handling. A gas/oil and water separator is called a 3-stage separator.
After storage of the crude this can be sold to refineries, that then produce the fuels, chemicals and energy we consume.
Reasons for processing
The raw crude often leaves the well head under very high pressure. Production pressures of greater than 23,000 pounds per square inch (1,600 atm) is not uncommon. The high pressure is dampened at the choke valve (or "Blow-out preventer" - BOP) that is the only equipment on the rig before the GOSP - or "3-stage Separator". Modern oil recovery may place a hydro-cyclone to replace the GOSP, allowing the water to be removed immediately and re-injected into the well. The cyclone will vary the rotation according to the water content and can also separate condensate from the gas where separate storage can be provided for the products close to the production well (e.g. on offshore platforms).
If the crude is pumped after just filtering away sands, the crude, gas and water will separate on the pipeline, forming "clogs" and "clutter" where the gas and water runs smooth and crude runs slower. This will make the pressure vary, and the pipeline will burst (M.A.A).
Produced crude oil leaving the well may contain large quantities of sulfur (contains e.g. hydrogen sulfide and sulfuric acid) and is then called "sour". The sulfur can be very difficult to remove since it may be bound to molecules in the crude and encapsulated in this. The most usual "crude sweetening packages" use glycol and/or fatty acids to remove the sulphur content. Crude that contains water is called "wet", and the water can then be bound in an emulsion in the crude to allow pumping on a pipeline. The crude must be processed and treated to make it safe, environmentally acceptable, before it can be transported to a refinery for processing.
It is often appropriate to separate gases and liquids for separate use. This also involves the separation of oily and water liquid phases.
In old days, the gas was considered waste and was burned on the spot - flared off. By recovering the gas, carbon emissions are reduced at the production site, and create a marketable commodity.