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Case study

Deep water structure installation – made easy

June 24, 2021

Gyro Compatt 6 all-in-one positioning transponder

Using just one Gyro Compatt 6, offshore contractor China Offshore Fugro Geosolutions (COFG) installed four pipeline end terminations (PLETS), measuring up to 15 m long and 10 m high, and weighing up to 45 tonne from the deepwater pipelay vessel Hai Yang Shi You (HYSY) 201.

With our Gyro Compatt 6, COFG was able to accurately monitor these huge structures through the water column to their final positions. That included through the initial lowering, which saw the structures tilted to almost completely vertical as they entered the water. With just Gyro Compatt 6 needing to be installed and secured for structure monitoring, the installation was made much easier – with reduced stress, fewer complications and in less time.

What is Gyro Compatt 6?

Gyro Compatt 6 simplifies structure positioning. It’s a positioning transponder, but much more, housing, in one small, compact instrument, our Wideband acoustic positioning, our Lodestar Attitude and Heading Reference Sensor (AHRS), a depth sensor and sound velocity, plus an integrated high speed acoustic modem. Combined, this provides a highly versatile, easy to install and use instrument that provides high update rate wireless attitude, heading, heave, surge, sway, pressure, sound speed and acoustic positioning of any subsea object.

So, you no longer have to install a gyro frame and put a subsea gyro in it, with a battery, a modem, sound velocity sensor, and maybe also a depth sensor, and then have to wire these up, turn them on, and hope it’ll all work. Instead, it’s just one instrument with everything you need in it – and it can be monitored and controlled from your topside using our Ranger 2 6G UltraShort BaseLine (USBL) positioning system or Fusion 1 or 2 Long BaseLine (LBL) software. It’s also quick to recharge on deck, for when you have a multi-structure installation campaign.

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Structure installation operations made easy

In a typical LBL installation scenario, you just deploy your Compatt LBL array at your seabed installation location and then install your Gyro Compatt 6 on board your structure. As you lower your structure, the Gyro Compatt 6 will then gather ranges from your LBL array, which will be gathered real-time by a ROVNav 6 LBL ROV transceiver onboard your ROV, which is in turn being tracked in the LBL array. In shallower waters, you can also use a Dunker 6 or your Ranger 2 USBL transceiver instead of a ROVNav transceiver to gather the ranges, further simplifying your operations and overheads.

In both scenarios, the ranges are then fed into your Fusion computer, which does all of the hard calculations for you, providing near-real-time position, heading, heave, surge and sway updates throughout your operation.

Simplifying COFG’s Liuhua operations
This is just what COFG did at Liuhua, on behalf of China Offshore Oil Engineering (COOEC), which was working for operator Husky China. Onboard the HSYS 201, COFG already has our Ranger 2 USBL positioning system, which works seamlessly with our Gyro Compatt 6s, as does all our 6G USBL family. COFG also has our Fusion LBL software and a ROVNav 6 transceiver onboard their ROV, so, with the addition of their Gyro Compatt 6, they had all they need for structure installation.

The 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.

Jia Wu, Operation Manager, Engineering Survey Division at China Offshore Fugro Geosolutions (Shenzen) Co. was pleased 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).”

LH29-1 is the third deepwater gas discovery made on Block 29/26 in the Pearl River Mouth Basin in the Eastern South China Sea. The field is due on stream later this year as part of the Liwan Gas Project.

We would like to thank COFG for telling us about the project and sending us the great photos. Got a story to tell about your Sonardyne equipment? Get in touch.


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