Subsea 7 has used acoustic and inertial navigation technologies from Sonardyne International during a project to install flowlines, risers and subsea structures at a new deep water field development in the Gulf of Mexico, due to start production in 2016.
To meet the positioning requirements of the project, Fred Goodloe III, Project Surveyor for Subsea 7 worked closely with Sonardyne’s in-house Survey Support Group (SSG) to determine the optimum configuration of subsea, ROV and vessel-based equipment, Sonardyne informed.
For the installation of the flowlines and structures, a seabed array of Sonardyne Compatt 6 transponders was deployed. The SSG assisted Subsea 7 in designing the array, optimising array geometry and modelling acoustic ray bending paths to ensure the design produced a robust array that met the stringent positioning tolerances required and offered sufficient redundancy in acoustic observations, the company said.
The work identified that the quantity of transponders needed for the project could be reduced through the use of Sonardyne’s inertial navigation sensor, SPRINT, installed on the survey team’s ROV which was being used for touchdown monitoring.
The use of SPRINT by Subsea 7 during the project allowed a tightly coupled range aided solution to be derived whilst the decrease in the quantity of Compatts, meant that there was a reduction in vessel time required for the installation, calibration and recovery of the array, Sonardyne explained.
John Brader, Survey Manager for Subsea 7 said, “The positive results we’ve seen during this project and also previously during our work on the NaKika field, have demonstrated SPRINT is able to extend the operating limits of our vessels’ USBL tracking systems and improve the operational efficiency of LBL without compromising positioning integrity. The planning work we carried out with Sonardyne’s SSG team ahead of mobilising for the job meant that when we arrived on location, we were able to get straight to work.”
Mark Chiddy, Sales Manager for Sonardyne stated, “We’re delighted that SPRINT has met Subsea 7’s expectations for performance and operational cost savings. Acoustically-aided INS, whether it is being used alongside USBL or LBL, is now trusted by our clients as a viable method of supporting a wide variety of subsea construction and survey operations.”