2013: Advent Oil & Gas: Processing 1 – stabilisation

by on December 8, 2013

As I’ve already mentioned, the exact composition of petroleum and natural gas is very variable.  In order to produce high-quality fuels a lot of processing is needed; this takes a number of steps, starting at the oil and gas field.

When extracted from the ground there are a lot of things mixed in with oil and gas that useless or detrimental to transport and further processing all of these need to be removed as soon as possible!  Most significant are water, salt, and sand; the inerts and contaminants that I described in the last article tend to be dealt with in later stages.  Crude oil stabilisation is the umbrella term for this initial separation processes.  It’s also called GOSP, for gas-oil separation process, because as well as separating out impurities it separates oil from gas for transportation (it’s much easier to pipe just gas or just oil than to move both in the same pipeline).

First of all, crude oil is heated and allowed to settle, so the oil ends up floating on the water and can be drawn off with a system of baffles; meanwhile the gas dissolved in the oil also separates.  This is normally carried out in three stages at around 50 bar, 10 bar, and atmospheric pressure.  Salt is removed electrostatically, and sand and other solids are taken out using cyclone systems that closely resemble a super-size Dyson vacuum cleaner (I’m sure they would approve of the endorsement).

The stabilisation processes often take place on a specialised platform when used for offshore fields.  Obviously this means that they have to be relatively compact and light so that the platform structure can support the weight safely.  Another important requirement is modularity: construction is much easier if most of the assembly can be done offsite, leaving a few sensible-sized units to be shipped to the platform.  Besides that, if one part breaks, you don’t want to have to dismantle the entire platform to get at it!

Once ‘stabilised’, the oil and gas can be sent off (generally by pipeline) to the refinery and the central processing facility respectively.  These are sufficiently large installations that they have to be located on land, often a long way from the wells, and each is worth an article in its own right…

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