Development of an Innovative 3D Subsea Laser Metrology System

摘要

Spoolpiece Metrology involves the precise measurement of the relative distance, height and angle between two flanges, allowing connection by a length of rigid pipe, known as the spoolpiece, which is fabricated to the required dimensions. In Technip’s subsea operations, spoolpieces usually connect a recently laid pipeline to a horizontal flange or vertical ‘hub’ on a wellhead, manifold or similar subsea structure. The conventional method of spoolpiece metrology utilises Long Baseline (LBL) acoustic transponders enabling accurate measurement of the flange separation distances. Each metrology typically takes 12-18 hours of costly, high specification survey vessel time. Outlay is further increased on subsea projects that require multiple metrologies. This significant expenditure, and the subsequent impact on overall project efficiency, was the main motivation behind initiating a development project to qualify and implement a new, cost-effective metrology solution requiring less vessel time than traditional methods. The essential requirements of the new technique were to be robust enough to work reliably in the harsh subsea environment and to be as accurate, if not better than the current acoustic method. With these conditions in mind, an innovative subsea scanning laser system, developed by 3D at Depth in Colorado, was identified as having the potential to fulfil, and even out-perform, the metrology requirements. This paper presents the outcomes of the laser metrology development project, including the results of dedicated onshore and offshore trials. Subsequent successful implementation of this technology on Technip deepwater metrology projects in the Gulf of Mexico is also discussed. Beyond the initial focus on spoolpiece metrology, this laser system has demonstrated its potential as a genuine ‘step-change’ in technology over existing subsea scanning techniques, and some other applications, such as accurate 3D modelling of existing subsea assets, will be presented.