When you go looking for detailed schematics for oil rigs, you’re likely to find multiple designs that will leave you confused. This is largely because most literature outside of textbooks doesn’t tell readers that different oil rigs are used depending on the environment that you’re drilling in—underwater drilling rigs are a little different from those used above ground. It’s even rare for these sources to tell you that we use a different drilling technique than we did before the 1930’s.
The modern oil rig is a complex piece of technology that consists of various interconnected mechanism to improve efficiency and speed. These are also called rotary drilling rigs, as opposed to the obsolete cable drilling rigs that were used before the ‘30s.
What is a Rotary Drilling Rig?
A rotary drilling rig uses a drill big to create a duct down to the underground oil reserves. These drills use axial loads and rotation to dig—which is much more efficient and allows us to dig deeper into the ground. Before rotary drilling rigs, when cable drilling rigs were used, the oil rig had a chisel that used to cut its way through to the oil—requiring much more energy, multiple equipment replacements and a lot of investment.
The fundamental difference between the modern rotary drilling rig and the cable drilling rig is the use of drills/drill bits rather than chisels. Additionally, rotary drilling rigs also use constantly flowing fluids to move drilling material from the face of the drill to the surface.
The Components of an Oil Rig
There are six fundamental components of an oil rig, these include:
- Power System
- Hoisting System
- Circulating System
- Rotary System
- Well Control System
- Well Monitoring System
The Power System
An oil rig requires immense power to dig deep hundreds, if not thousands, of miles into the ground. At each moment that it’s drilling into the ground, it generates huge amounts of waste material that needs to be pumped out as well. For this reason, most oil rigs use four different generators to power different parts of the rig and generate about 3000hp.
Each generator is connected to two different mud pumps, the rotary table and the draw works respectively.
Hoisting System
The hoisting system is used to drive-in and pull the drill out of the hole. It consists of a draw works that is connected to a motor and something called a crown block. The crown block is connected to the travelling block—from with the drill is suspended. An operator uses gears and brakes to move the drill up and down from the hole.
Circulating System
The circulating system is responsible from moving the drill cuttings away from the drill bit. It consists of two mud pumps, a Kelly hose,and mud return lines. As the drill moves deeper into the ground, a suction pump pulls the residual cuttings out of the ground and through the annulus holding the drill into a mud pit that filters out the solid particles. This resulting mud is then passed through the annulus and over the drill bit to create a continuous cleaning mechanism.
The Rotary System
The rotary system fundamentally consists of:
The swivel—Used to support the weight of the drill, allowing it to rotate and the pumping of mud while the drill rotates.
Rotary Tables—Located at the drill floor, connecting the drill string to the bit and responsible for making the drill turn.
The Well Control System
The well control system prevents the flow of fluid back up the well and stops blowouts. When you’re drilling for oil and reach a point where the oil and gas can explode through the ground—the pressure of the oil and gas can cause immense damage to the well and the people around it.
The well control system detects this backflow and removes these fluids that can damage the well. It does so using blow-out preventers and choke manifolds.
Well Monitoring Systems
These are gauges and valves located at the driller’s panel that allow the driller to detect any problems with the well and prevent possible malfunctions.
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