Developed with existing and emerging technologies, the new, low cost system creates a ‘moving map’ to illustrate seabed hazards such as marine slopes, soft marine soils and seabed obstructions in both near-shore and off-shore environments, and has worldwide application.
Roger Olds, Managing Director of Coffey International Limited, said that in the past, positioning exploratory jack-up barges and self-elevating work platforms has often been a dangerous and expensive process. Coffey Geotechnics’ new technology, however, has removed a significant amount of risk from the process of positioning jack-up barges during sensitive geo-marine sea-bed investigations and enabled cost savings of up to a quarter of a million dollars on individual projects to date.
“There are more than ten people involved in these jack-up barge bore drilling investigations, including six people on the barge itself. The last thing we want is for the barge, which can weigh in the vicinity of 130 tonnes, to become unstable in any way. The new seabed navigation system has mitigated some of this risk, and the best thing is that it has done so in a very cost effective way. “
Award winning technology the key
Mr Olds said that he was gratified to learn that the hard work and innovation of Coffey’s team of geotechnical engineers has been recognised in the recent APPEA Contractor Safety Awards for excellence in safety performance and innovation in safety management.
Sebastian Norris, Coffey Geotechnics Senior Engineering Geologist and team leader of the project, said that: “During various marine port investigation projects in North and North Western Australia we became very interested in technologies that would assist with the accurate positioning of drilling boreholes using jack-up barges (or self-elevating work platforms) that are generally towed into position.
“Small jack-up barges have historically been very difficult to position with any accuracy as tow vessel masters are at the mercy of strong currents, strong winds and wave action and often have no identifiable navigation aids such as a defined coast line to refer to.”
“With limited reference points and the influence of tide, wind and waves it is easy to lose track of the location of the barge in relation to hazards in the investigation area,” Mr Norris said. “So far, our experience with such hazards has been in the form of coral reefs, live pipelines or cables, and even ship wrecks with unexploded ordinances, as experienced recently on a job in Darwin.”
These difficulties pose considerable safety risks to personnel on the jack-up barge and tow vessel and are exacerbated when the vessel masters are not able to see all this detail on their navigation screens.
Coffey Geotechnics’ new system allows a tow vessel master to have visibility of both the barge and its position on the tow vessel navigation screen as well as geospatial information about the seabed hazards in the investigation area.
“In geo-marine surveys you are often moving a barge to up to 70 different locations, with each move taking around 1 hour. It used to be that if you were operating in bad weather the whole process could be extended by days. If you didn’t accurately place your barge, you’d have to go around in a circle and try again. Some moves could take up to five hours to get right.”
How the system works
The basics of the system are a moving map software package, and DGPS (Differential Global Positioning System).
Coffey Geotechnics then use long range radio telemetry and multiple display screens to present the data, with one of the screens and the DGPS equipment set up on the jack-up barge and the other screen on the towing vessel which is usually 100m away on the end of the tow line.
Mr Norris said that this configuration allows both the tow vessel master and the team on the barge to see the seabed features at the same time.
“Laptops are configured to run a copy of the moving map software and each laptop has a project map loaded into it, showing bathymetry data, coastline features and seabed obstructions and other hazards within the investigation area. Once set up, the maps show the location of the jack-up barge on each of their screens. This allows the towing vessel to easily guide the barge into the borehole position. All proposed borehole positions are loaded into the software which then is able to navigate you to the borehole from your current position around seabed features or hazardous obstructions.
“The software also has the ability to upload shape files so CAD drawing features, such as proposed structures, seabed obstructions and hazards, can be loaded onto the screen as a scalable feature,” Mr Norris said.
When researching and designing the navigation system, Coffey Geotechnics engineers chose commercially available, field-proven products.
“We came up with a system which, excluding the computer hardware and the DGPS equipment, came in at less than one thousand dollars,” Mr Norris said. “This low cost means that we can roll out the system to all of our marine investigation teams at once and that all of our projects can benefit from the safety and cost advantages.”
For more information, please contact:
Maurice Sauzier, Business Development Manager, Western Australia
T: +61 8 9355 7100; Email: maurice_sauzier@coffey.com
Diana Krause, Global Manager External Communication, Coffey International Limited
T: +61 3 9473 1300; M: +61 420 959 942; E: diana_krause@coffey.com
