Wireline

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The term wireline usually refers to a cabling technology used by operators of oil and gas wells to lower equipment into the well. In its simplest form, the wireline simply consists of a rope constructed of metal wire (sometimes referred to as slickline). In some cases, the inner core of the wireline includes insulated wires which provide power to equipment located at the end of the cable and provides a pathway for electrical telemetry for communication between equipment at each end of the cable (usually downhole and uphole).

For oilfield work, the wireline resides on the surface, wound around a large (3 to 10 feet in diameter) spool. Operators may use a portable spool (on the back of a special truck) or a permanent part of the drilling rig. Associated with the spool one finds gearing and a motor used to turn the spool and thus raise and lower the equipment into and out of the well – the winch.

The wireline apparatus essentially consists of a long cable wrapped around a large drum similar to a winch. In use, the wireline passes through the wellhead and lowers a variety of equipment (“tools”) into the well. Wireline can lower, for example, an explosive charge which operators then detonate in order to perforate the casing and provide a pathway into the surrounding reservoir which allows the flow of oil or gas into the wellbore and then to the surface.

Other activities carried out by wireline include the fitting and extraction of sub-surface valves and gas-lift valves, and the recovery of broken drill pipe (called "fishing").

Wireline well logging employs a wireline cable with an inner core of power and telemetry wires. In this use, wireline provides a means for lowering complex sensors into the well to make various detailed measurements of the well’s geology and other well characteristics.

Wirelining is split into two distinct branches, E-line, running an electric cable inside the wire to communicate with the tools, and Slickline which does not contain an electric cable. E-line is predominantly used in casing to log and perforate, while slickline is used mainly in tubing for fishing, recording and downhole maintenance.