Heavy wall drillpipe (or heavy weight drillpipe) has a greater wall thickness than ordinary drillpipe and is often used at the base of the drillpipe where stress concentration is greatest. The stress concentration is due to:
• The difference in cross section and therefore stiffness between the drillpipe and drillcollars.
• The rotation and cutting action of the bit can frequently result in a vertical bouncing effect.
HWDP is used to absorb the stresses being transferred from the stiff drill collars to the relatively flexible drillpipe. The major benefits of HWDP are:
• Increased wall thickness
• Longer tool joints
• Uses more hard facing
• May have a long central upset section (Figure 5)
HWDP should always be operated in compression. More lengths of HWDP are required to maintain compression in highly deviated holes.
Institute of Petroleum Engineering, Heriot-Watt University