Active vocabulary. 1. rotary drilling rig установка для роторного бурения 2. rotary table стол бурового ротора 3. kelly ведущая

The rotating equipment on a rotary drilling rig consists of the components that actually serve to rotate the drill bit, which in turn digs the hole deeper and deeper into the ground. Generally, rigs can rotate the bit in one of the three ways. The traditional way, the method that still dominates drilling, especially on land sites, uses a rotary table and kelly. A second way uses a top-drive system, which drilling contractors began to employ widely in the 1980s. A third way uses a downhole motor, which contractors use in special cases. A rotary-table system consists of five main parts: 1) a rotary table with a turntable, 2) a master bushing, 3) a kelly drive bushing, 4) a kelly, and 5) a swivel.

The turntable is round in shape and produces a turning motion that machinery transfers to the pipe and the bit. A master bushing is a fitting that goes inside the turntable. It has an opening through which crew members run pipe into the wellbore. A kelly drive bushing transfers the master bushing’s rotation to a special length of pipe called the “kelly”. Kellys are square or hexagonal in cross section, instead of round, because the flat sides enable the kelly to be rotated. The kelly slides easily into the drive-bushing opening. It is therefore free to move up or down through the bushing opening, even as it rotates, which allows the kelly to follow the bit down as it drills deeper. In general, a hexagonal kelly is stronger than a square one. Consequently, contractors tend to use hexagonal kellys on large rigs to drill deep wells because of their extra strength. Small rigs often use square kellys because they are less expensive. The swivel interfaces the rotary system with the hoisting system. A heavy-duty bail fits into a big hook on the bottom of the traveling block. The hook suspends the swivel and the attached drill string.

The drill pipe consists of 30ft sections of heavy steel pipe. Drilling people call each section a “joint of pipe”. The pipes are threaded so that they can interlock together. One end has inside threads and is called the “box”; the other has outside threads and is called the “pin”. When crew members make up drill pipe, they insert, or stab, the pin end in the box and tighten the connection. The drill pipe is a strong pipe, but can be quite flexible when used in slant or horizontal drilling applications. Below the drill pipe are drill collars, which are heavier, thicker, and stronger than normal drill pipe. The drill collars help to add weight to the drill string, right above the bit, to ensure there is enough downward pressure to allow the bit to drill through hard rock. The number and nature of the drill collars on any particular rotary rig can be altered depending on the down hole conditions experienced while drilling.

The drill bit is located at the bottom end of the drill string, and is responsible for actually making contact with the subsurface layers, and drilling through them by breaking up and dislodging rock, sediment, and anything else that may be encountered while drilling. There are dozens of different drill bit types, each designed for different subsurface drilling conditions. It can be a long process to change bits, due to the fact that the whole drill string must be removed; but using the correct drill bit can save a great deal of time during drilling. Drill bits are chosen given the expected underground formations, the type of drilling used, whether or not directional drilling is needed, the expected temperatures underneath the Earth, and whether or not cores (for logging purposes) are required. There are four main types of drill bits, each suited for particular conditions.

· Steel Tooth Rotary Bits are the most basic type of drill bit used today.

· Insert Bits are steel tooth bits with tungsten carbide inserts.

· Polycrystalline Diamond Compact Bits have polycrystalline diamond inserts attached to the carbide inserts found in Insert Bits.

· Diamond Bits have industrial diamonds implanted in them, to drill through extremely hard rock formations. Diamond bits are forty to fifty times harder than traditional steel bits, and can thus be used to drill through extremely hard rock without dulling overly quickly.

In addition to these main types of drill bits, hybrid bits, combining the features of various types of bits, can be used. If core samples are required for logging purposes, core bits are designed to drill and obtain these samples. There are a great number of different designs for drill bits, including tricone roller bits, button bits, tapered bits, fishtail bits, and mill bits. Each of these bits has specifically designed drilling traits. The fishtail bit, for instance, is designed to enlarge the drill hole above the drill bit, and the mill bit is designed to mill away metal scraps or objects found in the well. The drill bit, in addition to being very useful, is also very expensive. It is thus up to the drilling engineer to ensure that the correct bit is used at the correct time, to allow for maximum drilling efficiency, with minimum wear and tear on the valuable bit.