Wireline Units

How a wireline unit works

A hydraulic winch spools the wire onto a drum and lowers tools into a live well through the pressure control equipment (PCE). A measuring head counts depth and a load cell reads line tension at surface. The power pack drives the winch, and the cabin holds the winch controls and data system.

The PCE stack sits on the tree. From the bottom up it usually has a wireline valve with rams that close on the wire, one or more lubricator sections long enough to hold the tool string, a tool trap and catcher, and a stuffing box or grease injection head that seals the moving wire.

Configurations

• Slickline, a single solid wire for mechanical work such as setting plugs, shifting sleeves and running memory gauges. Common sizes include 0.092, 0.108 and 0.125 in (2.3, 2.7 and 3.2 mm).
• Braided line, a stranded cable for heavier fishing and jarring. It needs a grease injection head to seal.
• Electric line, an armoured cable with one or more conductors for logging, perforating and powered tools.
• Single drum or dual drum skids, and diesel or electric hydraulic power packs.

Key specifications

Standards and certification

PCE is normally built to API Spec 6A pressure classes and material classes, with NACE MR0175 / ISO 15156 materials for sour wells. API RP 16ST covers coiled tubing, not wireline. Your operator's intervention standard, or NORSOK D-002 in Norway, then sets PCE testing and well barrier rules. Skids follow DNV 2.7-1 or 2.7-3, and engines and electrics follow IEC 60079 for the zone they sit in.

Failure modes and inspection

• Wire and cable. Slickline loses ductility and corrodes, especially after sour or high-chloride wells, so the end is cut back and torsion tested. Braided and electric line lose armour wires and crush on the drum. Electric line needs insulation resistance and continuity tests on each conductor.
• Winch. Drum brake wear, hydraulic pump and motor wear, level wind faults and drum flange damage.
• Depth and tension. Measuring wheel wear and encoder or load cell drift, checked by calibration.
• PCE. Ram and seal wear in the wireline valve, eroded or galled quick union threads and O-ring grooves, and corrosion in lubricator bores. Each part needs a body test at its rated pressure and a function test.

Documentation

• Cable log with length, date fitted, cut-offs, torsion test results and wells run, plus electrical tests for electric line.
• Winch brake test and hydraulic oil analysis.
• Calibration certificates for the depth system and load cell.
• PCE test charts, certificates of conformity, material certificates and redress records for every component.
• DNV skid certificate, lifting set inspection and Ex certificates.

Integration with the rig or platform

Check that the PCE top connection matches your tree cap or adapter, and that union types match between sections from different makers. Allow rig-up height for the full lubricator above the tree and a crane or gin pole to lift it. A diesel power pack in a Zone 2 area needs its own Ex protection, while an electric pack needs a supply that matches the platform. Electric line logging needs a data system and software that your logging tools support.

Refurbishment and when to buy what

A wireline unit that has stood idle usually needs new hoses, seals and filters, a brake overhaul and often a new cable before it passes a rig audit. PCE redress means new seals and rams, a thread and bore inspection and a fresh body test. Buy the winch skid and the PCE as separate decisions, because their condition and certificates rarely match. NOV builds compact offshore wireline winches, and many smaller makers build units to order. For the test spread that runs alongside wireline on an appraisal well, see Well Test Equipment.