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Volume 8 Issue 2
November 2013

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Woods Hole Group Watch Dog Update

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Watchdog1000 picture

 

Woods Hole Group successfully deployed the prototype of the WatchDog-1000 ocean monitoring systems in the deep Gulf of Mexico in Green Canyon 782. The WatchDog monitoring system is a rugged, moored metocean monitoring system that is open-ocean survivable and adaptable for use from coastal to deepwater locations. The WatchDog system is designed to operate without servicing for up to one year and independently of deepwater vessels or facilities as well. WatchDog-1000 is customizable to offer a wide variety of data acquisition solutions including wind, wave, and current profiles in real-time (for example, every twenty minutes 24/7/365) in a variety of environments.

The WatchDog-1000 is designed to meet and exceed the data collection and reporting requirements of the BOEM Notice to Lessees (NTL) 2009-G02 during deepwater drilling and producing operations. The WatchDog system is, therefore, an alternative to collecting current profile data from drill rigs and producing facilities and has the following advantages:

  • Avoids the need for expensive and difficult to maintain rig-based ADCP Systems.
  • No need for using valuable deck and interior space on producing facilities for current measurements.
  • Improved data quality:
    • Data are not subject to contamination by interference of the producing facilities structure with ambient wind, current and wave fields.
    • Acoustic signals used to measure current profiles are not contaminated by interference with risers and mooring lines.
  • No need for facility specific design and engineering for onboard measurement system.
  • The system is transportable with minor mooring modifications.
  • The buoy system is an ideal platform for wind, wave and current profile measurements for real time support of operations on turret moored FPSOs.

The basic WatchDog system consists of three primary components – a surface buoy, a subsurface float and an anchor system – deployed as a compound mooring. A taut mooring connects the subsurface float to the anchor. A compliant, S-tether mooring connects the surface buoy and the subsurface float.

The surface buoy is a 3-meter discus-hull buoy, originally designed at the Woods Hole Oceanographic Institution (WHOI) over 30 years ago. This buoy has been widely used for oceanographic measurements and was adapted by the US National Data Buoy Center (NDBC) for their weather buoy program, where the emphasis is on real time meteorological and directional wave measurements. The WatchDog surface buoy is a 3-meter Surlyn foam-hulled discus buoy that is physically and functionally the same as the proven NDBC design. The hull is manufactured by the Gilman Corporation and the mechanical parts are fabricated by WHG, working closely with subcontractor Mooring Systems, Inc.

The NDBC 3-meter buoy has been used extensively for wave measurements, both non-directional and directional, for several decades. At the present time, NDBC has 3-meter buoys deployed at about 65 locations including the Gulf of Mexico, US Atlantic Coast, US Pacific Coast, offshore Alaska and Hawaii as well as the Great Lakes. NDBC’s 3-meter buoys are located in water depths ranging from 10m to more than 5000m. NDBC presently has about 25 each 3 meter discus boys operating in water depths greater than 1000m. The Canadian Weather Buoy Network also uses the same 3-meter discus buoy for offshore wind and wave measurements. Thirteen of the weather buoys deployed on the Canadian Pacific coast are the same 3-meter design used by NDBC. In the 1990s, NDBC developed the “Value-Engineered (VE)” 3-meter foam-hull buoy (which has approximately the same hull shape and dynamic performance as the older aluminum buoy) to overcome cost, maintenance, and technical limitations of the metal-hull buoy. The 3-meter VE buoys have proven to be reliable and cost-effective surface platforms in both deep and shallow water locations. NDBC is in the process of replacing all of its older 3-meter buoys, and many of the larger 10m and 12m offshore buoys, with the 3-meter VE buoys.

Over the past decade, NDBC has deployed the VE 3-meter buoys in deep-water locations, and these buoys have demonstrated the ability to survive and operate in severe weather conditions, including hurricanes. A recent example is NDBC buoy #41001, deployed in almost 4500m of water offshore of Cape Hatteras. This buoy survived Hurricane Irene in August 2011 with no damage and no loss of data, while recording 10m significant wave heights. WHG believes that the long development and testing history of the 3-meter VE buoy, its demonstrated record of survival and performance, and its acceptance by NDBC and others as a suitable platform for directional wave measurements, make this buoy the best choice for the offshore environment.

The Woods Hole Group Watch Dog buoy recorded 15 foot seas with maximum wave height of 27 feet from Tropical Storm Karen.

The surface buoy instrumentation suite may consist, for example, of a short range current profiler looking downward to a depth of 100 meters, a directional wave sensor, meteorology sensor package, data acquisition and logging system, and dual redundant telemetry systems.

The subsurface float can be configured with dual, long-range current profilers looking up and down the water column, a data acquisition system, and acoustic telemetry equipment to communicate with the surface buoy. Additional subsurface current meters can be placed on the mooring line and connected by inductive telemetry to the subsurface float. Sufficient battery power is provided to enable operation for more than one year without need for recovery of the mooring.

WatchDog-1000 monitoring system transmits data acoustically to the surface in real-time every twenty minutes. System operation is performed by a dedicated PC usually integrated with a Local Area Network. Software used to display and archive the data includes Woods Hole Group Integrated Real- Time Monitoring System (IRMS) software. Data is stored on the Control PC’s hard disk drive, and is usually telemetered to shore with an automated FTP method. Worldwide telemetry is possible with this method and has been used successfully by Woods Hole Group for a variety of oil and gas industry offshore systems.

WatchDog-1000 monitoring system is completely customizable to match a wide variety of client data acquisition requirements. Woods Hole Group specializes in oceanography and ocean engineering and can add value to measurements to the WatchDog-1000 monitoring system depending upon customer requirements. Data reports, design criteria studies, and specialized projects, such as fatigue analysis and internal waves are within our expertise.

 

Submitted By:
Dave Szabo, Houston Manager
Bob Hamilton, V.P. and Coastal Engineer

Contact Information:
Woods Hole Group – Falmouth
81 Technology Park Drive
East falmouth, MA 02536
P: 508-540-8080

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