Tools of the Trade

As you learned in the drilling equipment interactive, drilling is accomplished by coordinating the functions of four systems. To review, the systems are:

Power

The power system provides energy to the other three systems. On almost all modern rigs, power is provided by massive diesel or natural gas-powered generators. Most of the time, the power is distributed to the other systems by electrical cables. This is referred to as a diesel-electric power system. And there are a few rigs that use hydraulically powered systems as opposed to electric motors.

There still exist older mechanically driven rigs, not unlike the drive train of a car.  They use mechanical systems such as drive belts, chains, and clutches to transmit energy from the diesel engines directly to the other systems. These systems are rapidly becoming  replaced by diesel-electric systems.

Hoisting

The purpose of the hoisting system is to raise and lower equipment into and from the borehole. Since the casing is suspended at the surface until it is cemented into place, the hoisting system needs to be powerful enough to raise and lower the entire drill string or casing string – which can weigh over a million pounds in some cases. One of the heaviest casing string ever run was west of Casper, Wyoming.  It was a 16” diameter casing set at 13,964 feet for a total weight (in air) of 2.04 million pounds.

Circulation

The circulation system moves drilling mud through the drill string and annulus.

This mud serves several purposes:

1. It carries rock chips (cuttings) that the bit has drilled off the bottom of the borehole to the surface. These cuttings must be continuously removed to prevent stuck pipe and to not clog the borehole.
2. It cools and lubricates the drill bit.
3. It supports the borehole from collapsing.
4. Perhaps most importantly, the drilling mud counteracts – or balances – the pressure of underground formations due to its inherit density. This plays an important role in preventing blowouts.

Rotation

This system rotates the drill string and drill bit. A variety of technical solutions have been developed to rotate the drill string even as it slides downward within the hole. Most drill strings are driven by either a top drive or kelly drive turntable system.

Let’s take a closer look at how each system works.

Images: “Robot Slip” by Michael Black