Deepwater structure installation made easy
Client: China Offshore Fugro Geosolutions
For five decades, we’ve been working to make subsea developments safer, cleaner and more efficient than ever before. Our aim is always to mitigate risk for our partners, reduce the complexity of deepwater structure installations and increase efficiencies so projects cost less and teams spend less time offshore.
The challenge
When offshore contractor China Offshore Fugro Geosolutions (COFG) approached us looking for ways to improve the installation of multiple deepwater structures, we were excited to support their operation. The project required the installation of four pipeline end terminations. Measuring up to 15 m long, 10 m high and weighing as much as 45 tonnes each, the challenge was to accurately place each structure efficiently and reduce the time needed for the project to be completed.
These kinds of deepwater installations are usually done by installing a gyro frame and placing a subsea gyro into it, with a battery, a modem, sound velocity sensor, and maybe also a depth sensor. These then need to be wired up, turned on, and fingers crossed that it’ll all work. The various connections, components and necessary wiring between each, create multiple opportunities for things to go wrong.
The solution
Gyro Compatt 6 is a compact and versatile positioning transponder with a subsea gyro used to simplify structure positioning. From one instrument everything can be monitored and controlled from the topside using our Ranger 2 6G Ultra-Short BaseLine (USBL) positioning system or Fusion 1 or 2 Long BaseLine (LBL) software. What’s more, it’s quick to recharge on deck, making it a perfect choice for multi-structure installation campaigns.
Onboard the HSYS 201, COFG already use our Ranger 2 USBL positioning system, our Fusion LBL software and a ROVNav 6 transceiver onboard their ROV, all of which work seamlessly with our 6G USBL family of products, of which the Gyro Compatt 6 is a part.
This compact unit is much more than a positioning transponder. The unit combines an LBL transponder Wideband acoustic positioning, Lodestar attitude and heading reference sensor (AHRS), a depth sensor and sound velocity, plus an integrated high-speed acoustic modem. By combining these technologies into one small unit, a single yet highly versatile and easy to install instrument can provide high update rate wireless attitude, heading, heave, surge, sway, pressure, sound speed and acoustic positioning of any subsea object.
There is no need for the traditional gyro frame and subsea gyro technique and all the wiring and crossing of fingers that goes along with it. By deploying the Gyro Compatt 6, ranges from the LBL array can be gathered in real time by a ROVNav 6 LBL ROV transceiver onboard the ROV, and, in turn, tracked in the LBL array.
The results
With just the Gyro Compatt 6 installed and secured for structure monitoring, COFG’s installations were successfully carried out on the Liuhua 29-1 gas field development in water depths ranging from 520 m to 1120 m, between mid-October and the end of November 2019. Each of the four installations was made much easier – with reduced stress, fewer complications and in less time.
Jia Wu, Operation Manager, Engineering Survey Division at China Offshore Fugro Geosolutions (Shenzen) Co. was pleased with how their Gyro Compatt 6 performed.
“This all-in-one system offers us the biggest advantage for the operation, being easier to use, smaller in size and more efficient for preparation,” he says. “It is more convenient to secure as well as recover and does not require wiring between components, compared with a conventional gyro basket (transponder plus battery plus gyro).”
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