Upstream Oil and Gas Drilling Systems
In Upstream Oil and Gas Drilling Systems lesson, we’ll introduce the major components or systems in a typical drilling rig.
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Major Drilling Rig Systems
First, let’s start with the derrick.
The derrick is the structure above the well, most often a self-supporting tower. It must be tall enough to allow new sections, or joints, of drill pipe to be added as drilling progresses.
Among other things, the derrick holds a hoisting system, called the drawworks, which is used to lift heavy loads and numerous pieces of rotating equipment. There is also a swivel, which is a large handle that holds the weight of the drill string while rotating and makes a pressure-tight seal on the hole. The drive system is the mechanism that turns the drill string.
In the past, Kelly and rotary table drive systems were the main mechanical drive systems on rigs. However, top-drive drilling systems are the dominant systems used today. Here, the derrick holds a powerful motor which is actually suspended and can move up and down the derrick. A top drive system allows three joints of drill pipe to be routinely installed versus one joint with a kelly. This makes top-drive rigs much more efficient.
With over 1000 horsepower available to turn the drill bit, top drive systems are preferable for today’s ultra-deep and directional wells. The drill string consists of drill pipe joints of enough length to reach the depth of the target reservoir. They are hollow to allow the drilling mud to reach the drill bit.
The drill bit, at the end of the rotating drill string, does the work of cutting the rock as drilling proceeds. Drill collars are large diameter, heavier drill pipe sections to place additional weight on the drill bit.
Now, let’s briefly introduce the mud system, an important component of the drilling operation. Drilling mud is a complex mixture of water, clay, weighting material and chemicals.
The mud system is made up of a:
- Pump – moves the mud from the mud pits to the rig and drill string
- Mud-return line – returns mud from from the borehole
- Shale shaker – a sieve that separates rock cuttings from the mud
- Reserve pit – collects the rock cuttings as they are separated from the mud
- Mud pit – where drilling mud is mixed and recycled
- Mud-mixing hopper – where new mud is mixed and then sent to the mud pits, ready for use.
The last two important rig components we want to introduce are the blowout preventer and the power systems. The pressure control system, or blowout preventer, is made up of large, high-pressure valves that seal the drill string to prevent loss of pressure.
Power systems provide electric power to the entire rig and are often large diesel engines and electrical generators. Some rigs today are using engines powered by natural gas to reduce emissions.
Subsequent lessons on tubulars and bits, the drilling mud system, and well control will drill deeper into each of these important components of the drilling system.
Related Resources:
What is the difference between Upstream and Downstream?
Drilling Wells for Oil and Gas and Offshore Drilling