Rig Site Tips: Running New Drilling Bit

Running a new drilling bit  can seem a simple task during the drilling operations. Forget or miss some simple details can affect enormously the operations and lead to non-productive time. The drilling bit is the master piece of equipment in the drilling bottom hole assembly (Click Here). It has to be chosen adequately to get the best performances. 

First of all, the drilling bit which has to be run has to be on site before pulling out the drill string. The needed drilling bits which are recommended in the drilling program have to be available. For this reason, the material inventory has to be checked and updated periodically.

The drilling bit has to be verified physically. Check the bit diameter with the adequate gauge, be sure that the gauge is in good condition. The threads have to be checked also to avoid getting any wash out at this level. Look for any cracks on drilling bit body and also on the cutters.

Fig 01- Running Drilling Bit

Hydraulics issue is very important for the operations optimization, the bit nozzles sizes are mentioned in the drilling program. The size is chosen to get better hydraulics performance, on site the bit has to be run with the mentioned size. In the case when running a Re-Run bit, be sure that the nozzles are not plugged, this can be done by using a hose of water and look for water flow from the nozzles, you can determine which nozzle is plugged, do this as last action before making-up the bit. 

When using a tri-cone bit, check the cones and the sealing (Click Here).

In some cases, it has to be sure that the drilling bit can be made up on the drill string. The bit sub has to be available on site.

Every drilling bit has its make-up torque which is determined by its manufacturer. In order to apply the right make-up torque, the length of make-up tongue and the gauge have to be verified. As a verification, after making-up the drilling bit, the space between the drilling bit connection and box of the bit sub has to be eliminated to be sure that the drilling bit has taken the right torque.

The rotation has to be avoided into the casing (Click Here) to do not damage the bit or the casing.

In the open hole, if you face tight spot, pull up above it and connect the top drive or the Kelly and start reaming with adequate parameters. Do not insist to pass through tight spot. Work on that interval till getting stable torque. If the fluctuations of torque are severe, avoid to push through the restriction. Such action can lead to mechanical stuck pipe (Click here). The tight spot are expected just after pulling an under-gauge drilling bit.

In the case of using a conventional positive displacement motor (PDM), try to use the orienting mode to pass through restrictions using the slide sheet and try to push little bit. If no progress is noticed, using the rotary mode is unavoidable. It is risky to use the rotary mode, the original wellbore can be sidetracked, to avoid that, it has to be sure that the reaming rate is much greater than the drilling rate of that section. 

It is recommended to run the last three stands with wash down to avoid plugging the bit nozzles which can lead to pulling up the drill string to the surface.

It is highly recommended to sweep the hole after tagging and confirming the bottom and before starting drilling. Sweep the hole with a high viscosity pill in the case of vertical wells and with low viscosity pill followed by high density pill in the case of high deviated wells (Click Here).

Drill at least the half first meter (2 feet) with reduced parameters to check the drill bit behavior with the formation. Drill off test can be a good practice to better understand the drilling bit behavior. 

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