In the offshore oil and gas industry project cost and schedule considerations remain of prime importance, leading operators to seek more competitive field development solutions. The High Frequency Induction (HFI) production process is the most economical method for the manufacture of steel pipeline material and, when installed by the reeling method, delivers significant savings in terms of cost and lead-time. In recognition of this Corus and Subsea 7 have entered into a technology development program to prove the suitability of HFI welded linepipe for installation by the reeling process.
During the research program a sequence of pipes were cut and fabricated such that each spool contained a single girth weld at the mid point. These pipe spools were then subjected to simulated reeling trials using a bending former representative of the reeling vessel Seven Navica. The test programme was designed to determine the evolution of tensile, Charpy impact and fracture toughness properties of the pipe material following the application of the reeling process. To understand how the properties of the pipe evolve in relation to the strain history, actual strains were measured at various locations along the length of the spool. Particular account was taken of the girth weld location and positioning of the longitudinal seam weld.
Evaluation of the test results demonstrated that pipe properties after reeling were well within accepted norms for offshore pipe specification and construction. To complement this the work performed supports the specification of HFI linepipe for reeled installation when accompanied by appropriate testing data and best practice in design.