Sea Technology Magazine – Oct 2012 – Connectors for Seismic Surveying Under Ice in the Arctic
Offshore exploration continues to expand into new frontiers for leading oil and gas companies. There have been many changes in exploration methods over the last 40 years, including a significant increase in the number of streamers and channels, as well as higher pressure requirements and smaller form factors.
One of the more complex areas is the seismic market. SEACON (El Cajon, California) worked closely with ION Geophysical Corp. (Houston, Texas) on its data acquisition technology, with SEACON supplying the electrical and optical interconnections used in ION’s DigiSTREAMER towed streamer data acquisition system, designed for operating under Arctic ice.
Connector reliability is particularly important where there are adverse conditions and limited access, as in the Arctic. When demand for performance and survey areas increases, so do the challenges. Larger arrays mean towing more cables and managing larger amounts of data to collate and disseminate.
ION wanted to develop its next-generation towed streamer system with significantly higher specifications, which meant more demands on the connector interface. To meet this, SEACON had to resolve the technical issues created by the amount of data to be passed through the connections, while maintaining the quality and reliability of the connection in a tiny form factor. In addition, the data had to pass through many connectors.
Geo Explorer in the Arctic acquiring data with ION’s Digi-STREAMER including SEACON’s connectors. (Courtesy of ION Geophysical)
Quality Control and Testing
Downtime from technical failure can have an economic impact on seismic surveying, so reliability was a key concern.
The solution had to meet the electrical and pressure requirements and had to continue operating on specification after a significant number of mate and de-mate cycles. The connectors were tested to 1,200 volts AC; insulation resistance greater than 15 gigaohms 500 volts DC; continuity resistance less than 0.01 ohms; and current up to 16 amps in repeated pressure cycles to 500 pounds per square inch.
SEACON conducted, evaluated and simulated conditions expected to be encountered in the operational life of the system, which should run seven to 10 years. All aspects of the performance of the inserts and complete system were tested, including connector/insert pressure and electrical performance, mate and de-mate endurance, mechanical strength, tolerance to handling loads and material compatibility.
Initial stages required material specication and design analysis. As the project progressed, lab-based testing was conducted both at SEACON and ION to validate the performance of the product. As the project reached the nal stages, trial systems were deployed and sea trials conducted.
SEACON and ION defined the interface specification, which detailed the dimensional requirements and tolerance levels for the inserts, special material specication requirements, and qualication and factory acceptance testing requirements. They also reviewed the tolerances needed for the inserts and the housings they would be installed into. While many of the inserts being provided were installed into arrays, others were being installed into modules. These modules, developed by ION with design input from SEACON, contained complex circuit boards used to interoperate and, in some cases, convert data from electrical to optical signals.
Since the space in the module form factor was limited, ION asked SEACON to develop the wiring harness to interconnect the inserts to the circuit boards. The wiring harness contained a combination of instrument, Ethernet and power wires interconnecting both the inserts to the circuit boards and, in some cases, inserts to inserts.
The main challenge was the routing and bundling of this wiring due to space limitations. In addition, as the circuit boards were being installed later, the length tolerance control on the wiring and location of circuit-board connectors were critical.
ION’s DigiSTREAMER sections. (Courtesy of ION Geophysical)
ION rst utilized DigiSTREAMER and its custom deployment technology to acquire data below the ice pack offshore northeast Greenland from August to October 2009, enabling the company to acquire seismic data in areas previously hampered by heavy ice coverage. An icebreaker was used to clear rst – year ice for the primary acquisition vessel, Geo Explorer. The survey was conducted with an 8-kilometer streamer. More than 5,000 kilometers of data were acquired between 72 and 78 degrees north without any accidents or incidents. Ocean conditions reached -20ºC on deck and -40° C at ambient sea temperatures in a mix of open water through multiyear ice of medium floe size.
SEACON’s harness array assembly. (Courtesy of ION Geophysical)
Then, in summer 2011, ION further expanded its ArcticSPAN multiclient library by acquiring 5,600 kilometers of data offshore northeast Greenland, resulting in more than 55,000 kilometers of data for ArcticSPAN. DigiSTREAMER and its new SEACON connectors achieved an operational uptime of 98 percent.
ION is looking to build on its Arctic program and continue to expand use of the system in other areas of the world.