The Magazine for Underwater Professionals
Time saving features offered by software package allows survey team to complete major metrology campaign in just 26 hours
A major metrology campaign conducted off the coast of Western Australia has been completed in just 26 hours thanks to the time saving features offered by specialist survey software supplied by UK-based subsea technology company Sonardyne.
The project was led by offshore construction company EMAS CHIYODA Subsea (ECS), a joint venture of Chiyoda Corporation, Japan, and Ezra Holdings, Singapore, which was contracted by Apache Energy, USA, to install infrastructure at the Julimar natural gas field. The scope of work included installation of two manifolds, connected by five 30-metre vertical spools and five 80-metre horizontal spools.
Underwater metrology requires accurate, precise and robust measurements which are critical for successful fabrication and installation of spools and jumpers. Surveyors estimated that to gather the 10 metrologies at Julimar could take anywhere between 60 and 80 hours. “By opting to use Sonardyne’s Connect software package to streamline the process, the entire operation was subsequently completed in just 26 hours,” says a Sonardyne spokesman.
Connect was developed in partnership with USA-based survey engineering company 4D Nav and speeds up metrology campaigns by introducing expert settings, automated data collection and robust processing of acoustic measurements from planning through to report delivery, according to the spokesman. Not only does Connect help users save time and money, it also reduces the risk of spool pieces being fabricated incorrectly, he says.
The work at Julimar was conducted from ECS’ heavy lift, deepwater multi-lay vessel Lewek Constellation, operating with Sonardyne’s 6G (Sixth Generation) acoustic positioning transponder hardware. These were deployed on the seabed and placed in survey receptacles attached to the various structures. The design of the ROV-friendly transponders enabled them to be moved around the site and easily and precisely aligned relative to each structures’ north.
During the operation, the survey team collected depth and profile data using an ROV-held digiquartz depth sensor, then heading and inclination data at each survey receptacle whilst also collecting long baseline (LBL) acoustic range measurements. The collected data was analysed as one data set. The site’s shallow water depth meant paying particular attention to sound velocity.
“Connect’s ability to edit the sound velocity applied to individual and groups of baseline observations and reprocess multiple metrologies to evaluate the effect of the changes with a few mouse clicks proved invaluable to the ECS team,” says the spokesman. “Once the data QC was completed, each spool metrology was processed and a final report generated which contained a summary of the results including hub-to-hub horizontal distances, slant range, depth differences, attitudes, plus details of the calculations to support the results.”
On the success of the Connect software utilised during the Julimar project, Gerry Quinn, ECS survey manager, says: “Our team were blown away with the speed in which these metrologies were undertaken – in particular the unprecedented time of 26 hours total to measure five 30-metre vertical jumpers and five 80-metre horizontal jumpers in 80 metres water depth. The four-man survey team conducted not just the metrology, but the overall operations as smoothly and as efficiently as one.”