Appraisal well. A well drilled after the discovery of oil or gas to establish the limits of the reservoir, its expected productivity and the properties of the oil or gas.

Articulated loading column. This is where tankers load oil while at sea.

Barrel. A standard unit measure of oil. A barrel holds 35 gallons (159 litres) of oil.

Blow-out. An accidental escape of oil or gas from a well during the drilling stage.

Deep-water play. Exploration activity in offshore areas at a depth of 200 metres (600ft) or greater.

Derrick. A structure housing drilling controls.

Doodlebugger. A slang term for a seismologist.

Fish. Anything left in a wellbore, be it junk metal, a hand tool or a length of drillpipe.

Floater. An offshore drilling platform with no fixed base.

Payzone. Rock in which oil and gas are found in exploitable quantities.

Roughneck. Drill crew on the derrick floor.

Roustabout. A general labourer in the rig crew.

Scout. A petroleum industry worker who tracks competitive exploration and production activity.

Sweet crude oil. Crude oil containing very little sulphur and having a good odour as opposed to sour crude oil, which has a high sulphur content and an unpleasant odour.

Spud. The start of well drilling.

Weevil or worm. A new, inexperienced member of the drilling crew.

Wellbore. The hole from which oil or gas is extracted.

Wildcat. An exploration well.

Sources: glossary.oilfield.slb.com; energyinst.org.uk; www.og.dti.gov.uk

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