The largest oil and natural gas producer in the EU, the United Kingdom retains proven crude oil reserves of around 4 billion barrels and proven natural gas reserves of some 18.8 Tcf as of 2006. Containing the bulk of domestic reserves and an extensive network of subsea pipelines and infrastructure, the UK Continental Shelf (UKCS) is the most active offshore region for the UK's oil and gas sector, and industry giants Shell, ExxonMobil, Chevron and Total all explore and produce there. The third largest global energy company and headquartered in the UK, BP is operator of such major offshore UK producers as the Foinaven and Forties fields.
A wireline is an electric cable that is used to lower equipment or devices into a well and can transmit data back to the surface. A number of wireline tools can be lowered into a well in order to gather information; these include gamma ray, nuclear, and magnetic tools, among others. Wireline is usually wrapped around a large spool which can be placed on the back of a truck, or can be a permanent fixture on a rig. A wireline operator is responsible for operation and maintenance of the wireline truck and tools.