Guidelines for Drilling Riser Joint Integrity

Event:
Guidelines for Drilling Riser Joint Integrity
Date:
June 2000
Author:
H. Howells

The characteristics of deepwater drilling riser systems that influence integrity requirements and loss of integrity are as follows:

  • Higher tensions, placing increased importance on wall thickness and which may accelerate fatigue crack growth in the riser;
  • Larger curvatures, promoting the possibility of wear from drill string rotation;
  • Vortex induced vibrations due to severe currents, which can generate high levels of fatigue damage in short periods of time;
  • Longer drill string having increased tension, increasing wear at the top of the riser;
  • Longer and heavier riser joints, more difficult to handle with increased scope for damage during riser running and retrieval;
  • Greater internal pressures from mud head placing increased importance on wall thickness for hoop load resistance;
  • Greater external pressures from water column, placing increased importance on wall thickness and dimensional tolerances for collapse resistance;
  • Load sharing between riser tube and choke and kill lines placing increased importance on integrity of choke and kill lines for overall structural integrity

The potentially greater rates of wear and fatigue damage accumulation and increased importance of wall thickness integrity for deepwater indicate that traditional inspection practices used for shallow water operations may need to be revised for deepwater drilling. When initiating a drilling programme in deep water or harsh environments, the riser inspection strategy must therefore be re-evaluated to take account of the severity of the operating conditions.

As part of an industry initiative for developing guidance for drilling riser usage in deepwater, 2H Offshore Inc were contracted to develop guidelines for drilling riser joint integrity. This work consisted of the following activities:

  • Review of current practice for monitoring riser usage;
  • VIV fatigue analysis of 2 case study drilling riser;
  • Fracture analysis and inspection methods assessment;
  • Requirements for riser record keeping.

The findings of this work, which form the basis of the integrity assessment guidelines being developed, are reported in this paper.

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