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existing infrastructure. aided by using micro-components and source acquisition,” he adds.

SUBSEA

ROV positioning accuracy enables micro-electronics, helping to reduce Magseis has mostly deployed its accurate repeat surveys for 4D surveys. power consumption, as well as advances nodes with its automated cable sys-

Cable, or node-on-a-rope, positioning is in rechargeable battery technology, for tem. But, this year it will do its ? rst generally seen as getting less accurate as those who use rechargeable batteries. full-scale ROV deployed project, with water depth increases – although this is Node designs have also been optimized, ConocoPhillips in the Norwegian sector being challenged. which, together with the introduction of the North Sea. Some 3000 MASS I of automated handling systems, has al- nodes will be deployed from a vessel of

Past issues lowed for greater numbers of nodes to be opportunity – another ? rst for Magseis,

In the past, issues with nodes have been stored, charged, data downloaded and which has been using its cable spread around battery life, size (largely due deployed again faster. on the Artemis Athene. to the large batteries), and slow, inef? - “The small size of our MASS I nodes, The nodes, because they’re so small, cient deployment and recovery. In some at about 8kg, allows us to create a much will be deployed in large batches via cases, this meant having to do a survey more ef? cient and portable system and a skid on an ROV, reducing the time in chunks, retrieving and redeploying virtually means we can carry an unlim- needed for the ROV to travel through the nodes multiple times in order to cover a ited number of sensors,” says Magseis’ water column and eliminating the need set area, while source vessels waited. Steen-Hansen. for a subsea basket from which to collect

In the past, a typical deepwater node The ? rm’s 65-day battery life Marine nodes, a technique others also use. Two setup would see nodes deployed 400m Autonomous Seismic System (MASS I) ROVs will work in parallel from the one apart, with source shot over them on a nodes, weigh 8.35kg, are 227mm-long, vessel, which will traverse between the 50m grid, on X and Y axis, Walker says. 160mm-wide, 88mm-tall,rated for 3000m middle of two receiver lines. “Because

Starting from

Sensors were deployed sparsely, to keep water depth, and can be deployed by our nodes are very small, we can carry down ROV vessel costs, with denser ROV or by inserting the sensor capsules a lot more so that we don’t need a basket shot grids (from the cheaper source ves- into casings on Magseis’ own automated solution,” says Steen-Hansen, although sels) to compensate. Even then, because cable system. A few years ago, nodes he wouldn’t give away numbers. “Each of the time it took to place the nodes, us- were weighing in excess of 60kg. Magseis ROV can carry signi? cantly more nodes ing ROVs, the source vessels would have also recently launched a MASS III node on each run and, therefore, increase the to wait 2-3 days after node laying started with 150-day battery life. deployment ef? ciency.” before they could start working. Node “Everything is containerized and

Smart systems spreads would possibly need to be laid, fully automated, which means they shot over, then picked up and moved to could be deployed on ROV vessels al- Seabed Geosolution’s latest generation the adjacent area, but with overlap, and ready on hire by a client within a ? eld,” node, the 3000m water depth-rated then another shot run, which was also Steen-Hansen says. “Robots change the Manta, weighs 15kg in the water (a inef? cient. batteries, dock them and download data. previous generation weighed 65kg) and “Historically, even with two ROVs, you

The small size enables us to do that.” now measures 350mm-wide, 350mm- would be deploying 80-100 nodes a day,

Magseis’ MASS nodes were designed deep and 75mm-high. It can be deployed maximum, on a 400m node grid,”

Walker says. “With smaller new generation nodes, with comparable node spacing, you are able to, at a minimum, double that deployment rate, which means we can handle nodes fast enough to allow rolling receiver spreads with two dual source shooting vessels operating simultaneously.”

Previously, laying nodes was the normal project critical path

Seabed Geosolution’s Manta node in ROV and node on a rope guide. Image from Seabed Geosolutions.

activity, but now it’s the source vessels, says Martin Hartland, executive around using an atomic clock, for tim- by ROV or on a rope/wire, and will work vice president, performance, at Seabed ing, and positioning accuracy. They for 75+ days in -5°C to 40°C.

Some 900 Manta units can be stored in a

Geosolutions. “As multiple source vessels have a 32-bit analogue to digital resolu- standard 20ft container, which, along with start shooting simultaneously, thanks tion, Steen-Hansen says. “Some of the the deployment system, can be deployed to faster node handling, that’s when you technical speci? cations are leading edge on a vessel of opportunity, for deployment can get three-, four-fold improvements in sensor electronics,” he says. “The com- by ROV or, with the addition of an addi- production and a signi? cant reduction in pany has been inspired by miniaturiza- tional attachment and rope module, it can the overall project cost. That’s where we tion from the mobile phone industry become a node-on-a-rope system. are,” Hartland says. and does a lot of research and develop- ment in Sweden. We are raising the This year, Seabed Geosolutions is

Miniaturization bar of what’s achievable and it doesn’t due to launch its ? rst large-scale 4C/4D

Reducing node size has been key. The stop. It’s all about more inventory, fast Manta OBN crew, with the nodes due to size and weight reduction has been deployment and reducing overlap and be delivered in Q2.

oedigital.com March 2017 | OE 31 030_OE0217_Subsea2_subsea nodes.indd 31 2/21/17 6:43 PM