Drilling Systems and Equipment

Whether onshore or offshore drilling is carried out, the basic drilling system employed in both cases will be the rotary rig (Fig. 3.7) and the following summarises the basic functions and parts of such a unit. Three basic functions are carried out during rotary drilling operations  

We will now consider the rotary rig in operation, visiting all parts of the system starting at the drill bit. 

The most frequently used bit types are the roller cone or rock bit (F g. 3.8) and the polycrystalline diamond cutter or PDC bit. 

Between the bit and the surface, where the torque is generated, we find the drill string (Fig. 3.9). While being mainly a means for power transmission, the drill string fulfils several other functions, and if we move up from the bit we can see what those are. 

Most rigs are now fitted with a system whereby the drill string is rotated by a drive mechanism in the mast rather than by the rotary table at rig floor level. Thus 90 foot sections can be drilled before connections need to be made, and the drill string can be rotated while pulling out of the hole in 90 foot sections. This improved system, which speeds up the operation and allows better reaming of the hole is known as top drive. 

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