Pre-commissioning hose operations on the Valemon field in the North sea

Abstract

Marine operations for the offshore industry worldwide have been carried out for several decades and for each operation one has to consider which environmental conditions one can operate under. All operations should be performed in a safe and efficient manner; therefore an analysis for every specific operation with field specific conditions should be carried out to be able to define the operation limiting criteria’s. Pre-commissioning hose operations are relatively unusual marine operations which require applying the relevant flexible riser regulations. Attention is given to a pre-commissioning operation which consists of flooding, cleaning and gauging of the 22” gas pipeline from the Huldra platform to the Valemon platform in the North Sea. The aim of the study is to find the optimum hose configuration and define the limiting criteria for this operation. Two hose types will be considered, where experimental testing is carried out for one of the hoses (6” Oilflex Super hose) to identify unknown parameters to achieve a more accurate analysis. For the other hose type, adequate information was available to carry out analysis. Thereafter standard flexible riser configurations are considered as potential hose configurations for this operation and appropriate configurations are selected qualitatively for further evaluation using the computer software OrcaFlex. In Orcaflex, the remaining configurations will be considered for representative environmental loads from the Valemon field. Based on these loads, an optimum model will be selected. The free hanging configuration for the 4” Bunkerflex STH gave the highest operating limiting criterions for this pre-commissioning operation compared with different lazy wave configurations. The critical limitations were too high compression load and too high curvature for the hose, mainly in the splash zone, under the selected environmental cases. The operation limiting criteria is in addition to the environmental loads dependent on the arrangement on deck. The operation can be carried out during a weather window with up to Hs = 2.15 m without violating the identified limitations.