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    Under Reaming

    Uploaded by

    Don Braithwaite
    This document provides best practices for under-reaming in top hole sections, including: 1) Reducing RPM by 20-30 RPM to avoid premature wear if excessive vibrations occur. 2) Pumping at maximum rate and higher RPM to dislodge debris blocking under-reamer arms. 3) Using over 100 RPM to prevent spiral wellbores during fast under-reaming. 4) Placing a stabilizer behind the under-reamer to maintain verticality.

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    Attribution Non-Commercial (BY-NC)
    Download as PDF, TXT or read online from Scribd

    Under Reaming

    Uploaded by

    Don Braithwaite
    78 views1 page
    This document provides best practices for under-reaming in top hole sections, including: 1) Reducing RPM by 20-30 RPM to avoid premature wear if excessive vibrations occur. 2) Pumping at maximum rate and higher RPM to dislodge debris blocking under-reamer arms. 3) Using over 100 RPM to prevent spiral wellbores during fast under-reaming. 4) Placing a stabilizer behind the under-reamer to maintain verticality.

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    This document provides best practices for under-reaming in top hole sections, including: 1) Reducing RPM by 20-30 RPM to avoid premature wear if excessive vibrations occur. 2) Pumping at maximum rate and higher RPM to dislodge debris blocking under-reamer arms. 3) Using over 100 RPM to prevent spiral wellbores during fast under-reaming. 4) Placing a stabilizer behind the under-reamer to maintain verticality.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    78 views1 page

    Under Reaming

    Uploaded by

    Don Braithwaite
    This document provides best practices for under-reaming in top hole sections, including: 1) Reducing RPM by 20-30 RPM to avoid premature wear if excessive vibrations occur. 2) Pumping at maximum rate and higher RPM to dislodge debris blocking under-reamer arms. 3) Using over 100 RPM to prevent spiral wellbores during fast under-reaming. 4) Placing a stabilizer behind the under-reamer to maintain verticality.

    Copyright:

    Attribution Non-Commercial (BY-NC)
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
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    Under-reaming Practices

    The following practices should be adopted when under-reaming in top hole. When under-reaming with roller bearing cutters and controlled drilling or weight on bit cannot be maintained due to excessive down hole or surface vibrations and rough drilling effects. Consider reducing and/or changing the rotary RPM by 20 or 30 RPM. This should avoid premature gauge wear on the cutter cones and arm shirttails, which could lead to losing the cones in a very short period of time. .
    1) If the under-reamer arms do not close as a result of drilled debris blocking the arm pockets. Pumping at the

    highest rate possible, in combination with higher RPM may facilitate bounce of the drillstring off bottom dislodging the foreign material from the arm pockets.
    2) When very fast under-reaming is possible, ensure that there is sufficient RPM to prevent cutting a spiral

    wellbore. In this case > 100 RPM+ is recommended.


    3) When opening the hole, the use of an expandable blade stabiliser behind the under-reamer will assist in

    maintaining verticality of the wellbore. Placing a bit, stabiliser, taper mill assembly below the under-reamer may not guarantee vertical hole. It will assist however in greatly smoothing out any orbiting tendency of the under-reamer to ensure that the original hole and/or pilot hole is closely followed.
    4) On making the initial under-reamer cut, rotate for at least 15minutes at a reduced rate of 30-40 RPM with full

    pumps prior to drilling ahead. This allows adequate time for a full gauge, initial cut to be made. Note; the harder the formation to be under-reamed, the longer the time required before drilling ahead should commence.
    5) After having under-reamed for approximately 3m, stop rotating, pick up the string with the pumps on, and

    lower the string in an attempt to tag the ledge that should have been cut. If the formation is firm enough and has not washed out, this will give an indication that the hole is being cut. If the formation is very soft or badly washed out, this procedure will serve no purpose.

    Kingdom drilling services Ltd

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