At a glance
- Drilling rig
- Constructs a new well — bores the hole, runs and cements casing
- Workover rig
- Services an existing well — pulls tubing/rods, replaces pumps, fixes problems
- New hole drilled?
- Drilling rig: yes. Workover rig: no.
- Relative size
- Drilling rig: large, full systems. Workover rig: smaller, lighter.
- Also in the mix
- Well-servicing units and completion rigs
People use "rig" loosely, but a drilling rig and a workover rig do fundamentally different jobs at different points in a well's life. A drilling rig shows up first and creates the well from nothing. A workover rig comes back years later — sometimes many times — to keep that well producing or to prepare it for the end of its life. Understanding the split clears up a lot of confusion about rig sizes, crews, and day rates. For the foundation, start with how oil drilling works.
What a drilling rig does
A drilling rig is a construction machine. Its job is to create a new wellbore from surface down to the target reservoir, then case and cement that hole so it can safely produce. To do that it carries the full set of major rig systems working together:
- Hoisting — the derrick, drawworks, and blocks that raise and lower the drill string.
- Rotating — the top drive or rotary table that turns the bit to make hole.
- Circulating — the mud pumps and system that pump drilling fluid down the string and back up the annulus to clear cuttings and control pressure.
- Well control — the blowout preventer (BOP) stack and choke manifold that contain unexpected pressure. See well control and kicks.
Because it must lift heavy strings of pipe and case a deep hole, a drilling rig is large and capital-intensive. It runs and cements the casing strings, drills out, and ultimately hands off a finished wellbore. For the hardware that makes this possible, see drilling rig components, and for the size tiers on land, see land rig classes.
The key distinction: a workover rig never drills a new hole into the reservoir. It works inside the wellbore the drilling rig already created — pulling and running tubing, rods, and downhole equipment. If a new hole is being made, that's a drilling job, not a workover.
What a workover rig does
A workover rig is a smaller, lighter, far more mobile unit — often truck-mounted — whose job is to service a well that is already drilled and completed. It does not make new hole. Instead it enters the existing wellbore to perform "workovers," the maintenance and repair operations that keep a producing well healthy or change what it does. Typical work includes:
- Pulling and running tubing and rods to access or replace downhole equipment.
- Replacing downhole pumps — for example, swapping a worn rod pump or electric submersible pump.
- Fixing problems such as tubing leaks, scale, sand, or paraffin that have hurt production.
- Re-stimulating the well to restore or boost flow.
- Preparing for plugging and abandonment (P&A) when the well reaches the end of its life.
It's worth noting that the lines blur. Well-servicing units and completion rigs live in the same family. Completion rigs handle the work right after drilling — installing the production tubing and equipment that turn a freshly drilled hole into a producing well — while well-servicing units cover the lighter routine maintenance. Many of these jobs use the same kind of smaller, mobile rig as a workover.
Drilling rig vs. workover rig, side by side
Here's the difference distilled into the attributes that matter most:
| Attribute | Drilling rig | Workover rig |
|---|---|---|
| Purpose | Build a new well — bore the hole, run and cement casing | Service an existing well — repair, maintain, re-equip |
| Size | Large, full hoisting/rotating/circulating/well-control systems | Smaller, lighter, often truck-mounted and highly mobile |
| When used | Once, up front, to construct the well | Later — often repeatedly — over the well's producing life |
| Typical jobs | Drilling, casing, cementing a new wellbore | Pull tubing/rods, replace pumps, re-stimulate, prep for P&A |
| New hole drilled? | Yes | No |
| Crew | Larger crew running full drilling systems | Smaller service crew |
Read this way, the two rigs are complementary, not competing. The drilling rig is the heavy build crew that comes once; the workover rig is the maintenance crew that returns whenever the well needs attention. A single well might see one drilling rig and a dozen workover or well-servicing visits across decades of production.
Reference planning a drilling or workover program? rigs.work maintains a reference library of rig hands and supervisors across both worlds — drilling and well servicing — available by basin and window. Open the related reference and read the operating reference and role definitions.
Common questions
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