an essay concerning top drive drilling system (tds)

an essay concerning top drive drilling system (tds)

20150803

Top drive drilling system is one of the three greatest innovations in the drilling history, in a conventional rotary drilling rig, the drive is on the rotary table, a square or hexagonal kelly is rotated in the kelly bush, in so doing the rotary torque provides a drive downward and makes drilling towards the underground a possibility. The hook that hooks the kelly balances the hanging load of the drill string so that the drill bit is not collapsed.

Kelly is also connected with swivel, gooseneck and rotary hose so that the drill mud is pumped into the central hole in kelly and then the drill string (a string of drill pipes, drill collars, subs, stablisers/centralisers etc.) and then the drill bit, the application of drill mud is to lubricate the drill bit and drill string and come up to the surface ground through the annular betwixt the drill string external surface and the wellbore internal surface with cuttings of the formations to the solid controls (shale shaker, degaser, desilter, desander etc.) to be studied, another application of drill mud is to balance the downhole pressure to prevent an internal blowout(in the central hole of a drill string)

There are two sorts of blow outs, one is in the central hole of kelly and the other the annular betwixt the drill string and the wellbore. The former is to be sealed by kelly saver subs (upper and lower, one on the top of kelly, and the other on the bottom of kelly), the later is sealed by annular BOP, and ram bop seals both these two sorts of blowouts. BOPs on one side of the wellhead together with choke/kill manifolds on the other side are called well control system.

However, since the drive is on the rotary table, one joint of drill pipe is to be connected each time. Top drive drilling system provides drive on the top, and each time a connection of three joints of pipes (a stand) can be made. This saves 2/3 conventional drilling time, the cost of drilling (calculated and paid as dairy rate usually) is thus reduced.

Top drive drilling system is an integration of power swivel, pipe handler and guidebeam and carriage, and each can be subdivided and sub-subdivided. It is also an integration of hydraulic, electric and mechanic systems.

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a CNPC BPM TDS pictured in royal Saudi Aramco Shaybah field

Three major composions:

  • Power swivel
  • Pipehander
  • Guidebeam and carriage

Three control systems

  • Hydraulic
  • Electric
  • Mechanic

In the above I mentioned swivel connected with kelly through gooseneck, but a power swivel is a combination of swivel and gooseneck, washing pipe assembly, drill motor/main motor(s) and gearbox and braking devices are also part of this power swivel.

a bail stands on it, and under the bail there’s a bonnet connecting with gooseneck, within the bonnet there’s washing pipe packing assembly that consists of central pipe and packing union. The drilling mud goes from the gooseneck to the washing pipe packing unit downward through the rotary link adaptor to the pipehandler (I shall discuss later).

So the washing pipe packing assembly is located in/under the bonnet and on the rotary link adaptor.

The pipehandler is subdivided into rotary link adaptor, link tilt device (link elevator and links), backup wrench/tong, and IBOP.

The rotary link adaptor rotates clockwise and counterclockwise with link elevator.

The link tilt device, hanged on the rotary link adaptor is hydraulically controlled through two hydraulic tilt pumps, each one is on one link. It tilts forward and backward to grab a stand (three joints of drill pipes) to make a connection (thread) to the drill string.

Backup wrench/tong is connected with IBOP, the link elevator grabs a stand and inserts it through the bellguide/mouth of the backup wrench into the saver sub to make a connection with the saver sub, and then make a connection with the drill string in the wellhead and breakout the connection with the saver sub, then the link elevator is to catch another stand, and the mentioned process is to be repeated.

The saver sub is beneath the IBOP – internal blowout preventer, it is called ‘internal’ because it only prevents the blowout in the central hole of a drill string, it doesn’t prevent the blowout of the annular betwixt the drill string external surface and the wellbore internal surface – that is the function of annular BOP. it alters the bop functions of the save subs in a kelly pipe i discussed above.

Ibop system consists one remotely controlled bop and one manually controlled bop. A ball valve is installed in the remotely controlled bop, and the manually controlled bop is actuated by the hydraulic system through a hydraulic pump. When a connection is broken out, it prevents the leakage of the drill mud from leaking to the drill floor, this is another application of ibop.

Now the guidebeam, it is installed on the derrick/mast, with a padeye welded on the crown block, in so doing the top drive can be hoisted upward and downward with the carriage travelling on the guidebeam attached to the derrick/mast of a rig. It makes the portability a possibility.

About Jun Wang
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