Analytical verification of requirements for safe and timely lay-down of an offshore slay pipeline abandonment head during some pipe-lay stops: a case study of Forcados Yokri integrated pipeline project in Nigerian shallow offshore

Abstract

It is not often planned that an S-lay installation barge will stop operation for longer time than necessary. In some cases, one may think that stoppage will last for some minimal time. In some other time, it could be for an unpredicted number of days, especially when it is an industrial dispute or security crisis. This happens frequently in developing countries. This paper demonstrates the importance to always abandon pipelines on seabed when there are interruption in continuing pipeline construction, especially when such interruption are beyond the control of the engineering team. The result of this paper indicates that consequence of not doing so is very cruel to the structural integrity of the pipeline structure after the first twenty four (24) hours of exposure in West African Nigerian mild offshore weather condition. Environmental pollution and therefore safety of lives and properties may be jeopardized should the pipeline structure be used for oil or gas transport when such limits are ignored. Fracture mechanics approach is used on API 5L X52 of wall thickness of 0.5 inches pipeline structure. The pipeline was failed in a fatigue event due to wave loads in Forcados offshore in the Nigerian Niger Delta area. A 30-days wave data is employed in the analysis and result computations.