Active vocabulary. 1. rotary drilling роторное/ вращательное бурение 2. drill bit буровое долото 3. rig буровая установка

While the concept for rotary drilling - using a sharp, spinning drill bit to delve into rock - is quite simple, the actual mechanics of modern rigs are quite complicated. In addition, technology advances so rapidly that new innovations are being introduced constantly. The basic rotary drilling system consists of four groups of components. The prime movers, hoisting equipment, rotating equipment, and circulating equipment all combine to make rotary drilling possible.

The prime movers in a rotary drilling rig are those pieces of equipment that provide the power to the entire rig. Up until World War II, rotary rigs were traditionally powered by steam engines. Diesel engines became the norm after the war. Recently, while diesel engines still compose the majority of power sources on rotary rigs, other types of engines are also in use. Natural gas or gasoline engines are commonly used, as are natural gas or gasoline powered reciprocating turbines, which generate electricity on site. The resulting electricity is used to power the rig itself. Other rotary rigs may use electricity directly from power lines. Most rotary rigs these days require 1,000 to 3,000 horsepower, while shallow drilling rigs may require as little as 500 horsepower. Rotary rigs designed to drill in excess of 20,000 feet below surface may require much more than 3,000 horsepower.

On diesel-electric rigs, powerful engines drive large electric generators. They, in turn, produce electricity that flows through cables to electric switch and control equipment enclosed in a control cabinet. From the control gear, electricity goes through more cables to electric motors. The manufacturer attaches the motors directly to the equipment to be driven – for example, the drawworks or mud pumps.

The hoisting equipment on a rotary rig consists of the tools used to raise and lower whatever other equipment may go into or come out of the well. For instance, in rotary drilling, the wells are dug with long strings of pipe (drill pipe) extending from the surface down to the drill bit. If a drill bit needs to be changed, either due to wear and tear or a change in the subsurface rock, the whole string of pipe must be raised to the surface and lowered back into the well after the bit replacement.

A typical hoisting system is made up of the drawworks (or hoist), a mast or derrick, the crown block, the traveling block, and the wire rope drilling line. The most visible part of the hoisting equipment is the derrick, the tall tower-like structure that extends vertically from the well hole. This structure serves as a support for the drilling lines and drawworks. The height of a rigs derrick can often be a clue as to the depth of the well being dug. Drill pipe traditionally comes in 30ft sections, which are joined together as the well is dug deeper and deeper. This means that even if a well is 20,000 feet deep, the drill string must still be taken out in 30 foot sections. However, if the derrick is tall enough, multiple joints of drill pipe may be removed at once, speeding up the process a great deal.

Manufacturers make drilling line from very strong wire rope. Drilling line runs from 22 to 51 millimetres in diameter and is similar to common fiber rope, but is made out of steel wires. It is designed especially for the heavy loads encountered on the rig. The line comes off a large reel – a supply reel. From the supply reel, it goes to a strong clamp called the “deadline anchor”. From it, the drilling line runs up to the top of the mast or derrick to a set of large pulleys which is called the crown block. In the oilfield, the pulleys are termed “sheaves”. The drilling line is reeved several times between the crown block and another large set of sheaves called the traveling block to get the effect of several lines. The heavier the anticipated loads on the traveling block, the more times the line is reeved between the crown and travelling block

The drawworks is a big, heavy piece of machinery. It consists of a revolving drum around which crew members wrap or spool wire rope drilling line. It also has a catshaft on which the catheads are mounted. Further, it has clutches and chain-and-gear drives so that the driller can change its speed and direction. A main brake provides the driller a way of slowing and stopping the drum. An auxiliary electric brake assists the main brake by absorbing the momentum created by the load being raised or lowered. Big electromagnets inside the auxiliary brake oppose the turning forces on the drum and help the main brake stop the load.

The brake is the main lever at the driller’s console. The man on the brake is by definition the driller. Actual drilling is accomplished by gently releasing the mechanical brake a little at a time, allowing the drilling line to unwind slowly, and so lowering the drill pipe through the rotary table in a way that a more or less constant hook load (and with it a constant weight on the bit) is achieved.

While drilling, the noise of the releasing mechanical brake is heard all over the rig. An experienced rig hand listening to the brake can almost feel the drilling progress made. The changing tune of the brake is very often the first indication of a drilling break, much before the increased rate of penetration is evident on strip charts or any other recording device. At this point the driller can be called and asked what is going on.