B0E - MATERIALS BÀSICS D'AGLOMERATS DE CIMENT B0E2 - BLOCS DE MORTER DE CIMENT

When the entire drill string is to be run into the hole it will normally already be standing inside the derrick structure in several orderly rows in the ‘set- back’ area to one side of the V-door. When it was last pulled out of the hole the string was disconnected not in single joints, but in ‘stands’ of three joints (or sometimes two) with the male threaded ‘pin’ ends lowest, and this is how it was ‘racked back’ in the fingers.

A three-joint stand of any or 30-foot tubular is called a ‘treble’ (or ‘thribble’ an an American rig), and a stand of two 45-foot joints is called a ‘double’, each stand making 90 feet or thereabouts in length. This

reaches to the ‘fingerboard’ high above the drill floor, where the top ends of all the stands have been pulled into slots between the fingers by the

who works leaning out from the adjacent monkeyboard with a har- ness round his midriff.

The kelly, with the swivel, the kelly spinner, the kelly cock and the kelly bushing attached to it, has meanwhile been stored in the ‘rat hole’, which is a deep tubular storage recess that projects down beneath the drill floor. The rotary hose is still attached to the swivel, so that to reconnect the assembly for drilling, the swivel simply has to be picked up by its bail and fitted into the hook, while the lower end of the kelly (which is protected with the kelly saver sub) has to be screwed into the topmost joint of drill pipe. But first the drill string has to be ‘run in the hole’.

The bottom hole assembly (the BHA), perhaps a thousand or more feet of heavy tools, is first made up as it is passed item by item through the rotary table opening. The bit, stabilizers, collars, jars, subs, heavy-wall drill pipe and any other components included in the carefully designed BHA that will make the next section of hole are in turn pasted with thread compound and screwed togther, or ‘made up’, and lowered through the rotary by elevators which hang by links from the hook/block assembly. As each item is lowered through the rotary by the hoist, the drawworks brake is applied and slips are inserted, or a spider is used to provide a holding grip while the next joint is connected. The weight of the entire string could be more than 200 tons, and can sometimes cause the steel of the slips to fuse to the rotary bowl, so the roughnecks apply ‘dope’, or zinc-based thread compound, to the backs of the slips before they insert them.

TO the BHA the stands of drill pipe that comprise the drill stem are

then connected stand by stand, and these are lowered through the rotary opening. Again, the appropriate type of elevators are fitted by the

round the shoulders of the upper tool joint of the stand to be low- ered, and the stand is released from the fingerboard. The hoist lifts the stand a little while the roughnecks on the floor feet below guide its lower end over to the rotary and stab it into the tool joint box of the tubular held there in the slips. The connection is then spun up, usually by a pneumatic pipe spinner, but on some rigs by a spinning chain which is thrown around the stabbed pipe and pulled off again by the make-up or spinning

Finally the correct torque is applied to the connection by tongs, which might be of the manual type or else pneumatically operated.

Slips are inserted manually around a tubular to grip it in the rotary during the making or a connection.

The break-out tong is secured round the lower of the two tool joints. The end of its arm is attached by a wire to the break-out shaft on the drawworks, but this wire remains slack during the make-up operation, since the break-out tong on’ this occasion is only meant to ‘back up’, or hold the joint firm while the connection is tightened. The make-up tong meanwhile is applied to top joint and the end of its arm is connected with the make- up shaft-on the drawworks by a chain which is wound tight to

up the connection. The arm of the break-out tong tends to turn clockwise when the chain is pulled, so a wire called a ‘snub line’ which is secured to a nearby post’ on that side is permanently fixed to the break-out tong to prevent it from turning round. There is also a snub line leading from the make-up tong arm to a post on its own side, but this remains

slack during making-up. Also connected to the end of the make-up tong arm is a torque gauge with a transmission line leading to the doghouse. The ler is thus able to read what torque is being applied to the connection as he controls the make-up

USE OF MAKE-UP TONG

During make-up, the joint is torqued-up by the make-up tong chain. The break-out tong is pre- vented from turning round by a snubline.

Having tightened the connection to the correct torque, the weight of the complete string is taken by the hoist, the slips are removed and the stand is lowered ninety feet into the rotary until the tool joint of the uppermost joint of pipe is two or three feet outside the rotary. The drawworks brake is again applied, the slips are inserted between the rotary bowl and the pipe to grip it, and the elevators are released to pick up the next stand. This process is repeated for each of the stands, which may number more than two hundred in a deep well. The complete cycle of operations for each connection takes only a minutes, yet rig operators and oil companies are constantly seek- ing ways of reducing the connection time to save costs.

When the last stand of drill pipe is in the slips, the kelly, with the swivel, kelly spinner, kelly cock, kelly bushing and saver sub attached, is lifted out of the rat hole and screwed into the drill pipe by the pneumatically operated kelly spinner, finally getting torqued-up by The driller starts the mud pumps to begin circulating drilling fluid through the string to the bottom of the hole, and he lowers the kelly until the kelly bushing engages with the rot- ary master bushing. A roughneck stationed at the shale shaker announces ‘returns at the shaker’ and the driller starts the rotary turning and eases the drawworks brake off to lower the bit to the bottom of the hole. When it touches bottom, ‘drilling ahead’ commences.