A workover rig is a smaller, mobile piece of equipment used to service and repair oil or gas wells that are already producing. While a drilling rig creates new wells, a workover rig steps in after the well is up and running, handling everything from replacing worn tubing to restimulating a formation that has slowed down. These rigs are a constant presence in mature oil and gas fields, where keeping existing wells productive is often more economical than drilling new ones.
How It Differs From a Drilling Rig
The simplest distinction is purpose: drilling rigs create wells, workover rigs fix and maintain them. That difference in mission drives everything else about the equipment. Drilling rigs need massive rotary tables, drill strings, and mud pumps capable of boring thousands of feet into rock. Workover rigs skip most of that heavy drilling hardware and focus instead on a hoisting system that can pull pipe and downhole equipment in and out of an existing well.
Size is the other obvious difference. Drilling rigs are large, complex installations that can take weeks to assemble. Workover rigs are often truck-mounted or trailer-mounted, designed to drive to a well site, set up quickly, finish the job, and move on. This compact footprint makes them far less expensive to operate and allows a single rig to service multiple wells across a field in rapid succession.
Key Components
Despite being smaller than drilling rigs, workover rigs still carry serious lifting power. The main components include:
- Mast: A telescoping or folding vertical structure that provides the height needed to pull long sections of pipe out of the well. On truck-mounted units, the mast folds down for road transport and raises hydraulically on site.
- Drawworks: The main winch system, powered by an engine ranging from about 250 to 1,000 horsepower depending on the rig’s size. The drawworks spools wire rope through a system of pulleys to raise and lower equipment in the well.
- Hoisting system: Includes the traveling block, crown block, and hook that connect the drawworks to whatever is being lifted. Hook load capacity ranges widely, from around 160,000 pounds on lighter units to 500,000 pounds on heavy-duty rigs designed for deep wells.
- Hydraulic systems: Power the tongs used to make up and break out threaded pipe connections, as well as blowout preventer controls and other safety equipment.
- Control panel: Where the operator manages hoisting speed, braking, and monitors loads on the system.
Modern workover rigs can handle wells from about 8,000 feet to over 23,000 feet deep, with the rig’s rated hook load determining how much pipe weight it can safely manage.
What a Workover Rig Actually Does
The work falls into a few broad categories, all aimed at keeping a well productive or preparing it for the end of its life.
Pulling and replacing tubing. The production tubing inside a well corrodes, develops leaks, or gets scaled up over time. A workover rig pulls the entire tubing string out of the well, one joint at a time, so damaged sections can be replaced. This is one of the most common workover tasks.
Replacing downhole pumps. Many wells use electric submersible pumps or rod pumps installed deep in the wellbore. When these fail, they have to come out. A benchmarking study of workover rigs in active oilfields found that pulling a failed pump alone took between 7.5 and 13 hours, with the full job of pulling the old pump, running new equipment back in, and final checks taking several days per well.
Well stimulation and refracturing. When a reservoir’s production declines, the formation can sometimes be restimulated. This may involve hydraulically fracturing the rock again, acidizing the formation to dissolve blockages, or perforating new zones in the casing to access untapped pockets of oil or gas. According to the EPA, refracturing jobs involve many of the same steps as the original completion, including expelling fluids and managing gas that flows back to the surface.
Zonal isolation. Sometimes one zone in a well starts producing too much water or gas, and operators need to seal it off while keeping other zones open. The workover rig provides the hoisting power to run cement plugs, packers, or updated completion hardware into the well.
Abandonment and decommissioning. At the end of a well’s life, a workover rig removes downhole equipment and sets cement plugs to permanently seal the wellbore before the site is restored.
How Long a Workover Takes
Timelines vary enormously depending on the job. A simple pump swap on a shallow well might wrap up in two to three days. A study that tracked five workover rigs on pump replacement jobs found total times (from moving the rig to releasing it) ranging from roughly 60 to 85 working hours per well, with rigs operating 12-hour shifts. Of that time, rigging up took 6 to 12 hours, the actual downhole work consumed the bulk of the schedule, and final checks and rig release added another 5 to 10 hours.
More complex jobs like refracturing or major completion redesigns can stretch to a week or more. The rig-up and rig-down phases are relatively fast compared to a drilling rig, which is part of the economic advantage. Moving between well sites typically takes 6 to 8 hours.
The Crew
Workover rigs run with small crews, typically three to five people. The core positions are:
- Rig operator: Leads the crew and runs the rig controls. The operator oversees all hoisting, manages rig-up and rig-down procedures, and is responsible for the safety of the operation. On many crews, the operator also drives the rig between locations.
- Floorhands (or rig hands): Work on the rig floor handling pipe, latching and unlatching elevators, and operating tongs. They also load and unload pipe, assist with equipment maintenance, and help with physical setup. New crew members typically start here.
- Derrickhand: Works at height when needed, assists with pipe handling, and fills in on the floor or at the controls as the job requires.
A field supervisor or “tool pusher” may oversee several rigs across a field, checking in on operations and handling coordination with the well operator. Compared to a drilling rig crew of 20 or more, the lean workover crew reflects the smaller scale of the equipment and the shorter duration of most jobs.
Safety Standards
Workover rigs operate under the same regulatory framework as drilling operations. The American Petroleum Institute’s Recommended Practice 54 (API RP 54) covers occupational safety for both drilling and well servicing. Among its requirements: every land rig mast must have an auxiliary escape route installed before anyone works at height. OSHA enforces compliance with these standards and can cite operators for violations.
Because workover rigs move frequently and set up in varied conditions, the rig-up and rig-down phases carry particular risk. Crews inspect guy wires, mast pins, and hydraulic lines before each job. Blowout preventers are standard equipment, since workover operations can encounter unexpected pressure when opening up a well that still contains hydrocarbons.