Description

Geometrics is leading and transforming the future of marine HR3D with the revolutionary P-Cable system. Based on our tried-and-true GeoEel technology, the P-Cable is an innovative platform for towing up to 24 short streamers from small vessels of opportunity with minimal crew. For marginally more cost than a conventional 2D high-resolution seismic survey, you can have true 3D data with all the attendant advantages -- better imaging of more complex structures, less directional bias, full 3D migration and better preservation of high frequencies. The resulting data are simply amazing and the resolution unprecedented.

But don't take our word for it, see the P-Cable difference.

General Specifications:

  • GeoEel Solid Active sections
  • Number of streamers: 6 – 24
  • Streamer length: 25 – 100m
  • Channels per streamer: 8 – 32
  • Streamer separation: 3.125, 6.25 and 12.5m
  • Group interval: 1.5625 (GeoEel liquid), 3.125, 6.25 and 12.5m
  • Data recording: PC-based Geometrics CNT-2 marine controller
  • Paravanes: Baro #3 or equivalent*
  • Streamer handling: Two small winches for paravanes, two medium winches for cross-cable and digital signal cable, storage drum recommended for active sections

CNT-2 Seismic Acquisition Controller

Powered by the CNT-2 Seismic Acquisition Controller. The CNT-2 is a system control capable of changing the sample interval, gain settings, and more. It has a full survey log, which keeps track of changes in acquisition parameters, where each file was written along with the date and time, alarms or error messages that have occurred during the survey, time-stamped observer comments, etc. The CNT-2 system also has the following capabilitites:

  • Multi-Drive Writing Capabilities in SEG-2, SEG-Y, or SEG-D
  • Fully RAID-compatible
  • Full integration of GPS, Depth, Compass, and other serial data into SEG-D
  • System Testing

For more details on the CNT-2 Seismic Controller please refer to pages 61 - 181 of the GeoEel/P-Cable Manual.

 

Features and benefits

  • Small and light: 5-ton bollard pull*: Deployable from small vessels of opportunity
  • Simple: minimal in-water assets: Highly robust, easily and rapidly deployed with minimal crew
  • True 3D coverage, full 3D migration: Better resolution of more complicated geometries
  • Bin size as small as 3.125m: Higher resolution than previously possible
  • Array width up to 300m: Rapid production, up to 50 km2/day at 5 knots (6.125m bins)
  • Allows overlap between sail lines: Minimal infill required
  • Based on true solid streamer technology: Bulge wave immunity, virtually no strumming noise; environmentally friendly
  • Convertible to full-featured 2D system: Allows large-offset 2D survey for velocity determination if necessary
 

Technical Details

 

TYPICAL USES

  • Oil and Gas Exploration
  • Coastal Rehabilitation
  • Seismic Risk Assessment
  • Methane Hydrate Investigation
  • Marine Geologic Mapping



Frequently Asked Questions

Inside The P-Cable System

What Streamers Does the P-Cable Use?

The P-Cable is based on Geometrics’ digital GeoEel technology. The GeoEel Solid Digital Streamer was developed from the ground-up as a high-resolution system, offering a Nyquist of 4 KHz.

How many streamers can there be in the P-Cable?

Assuming #3 vanes, this depends on the desired bin size and the width of the spread. Typical streamer spacing is 6.25m or 12.5m, yielding a cross-line bin size of 3.125m or 6.25m, respectively. This equates to up to 16 streamers spaced at 12.5m or 32 streamers at 6.25m. Larger arrays require more lift and hence larger paravanes.

What is the system bandwidth/sample rate?

The A/D modules can sample at up to 8 KHz. Analog bandwidth of the arrays depends on the number of hydrophones per group, which can range from 4-12. Typical is 10 Hz – 3.2 KHz. A low-end -3dB point of 5 Hz is available.

How long can the streamers be? How many channels in each?

Each hydrophone streamer section contains 8 channels. Section length depends on the group interval (1.5625m, 3.125m, 6.25m, or 12.5m), and is either 12.5m, 25m, 50m, or 100m. Sections can be connected together to build multi-section streamers. Typical systems consist of single-section, 8 channel arrays, having group intervals equal to the streamer spacing, yielding square bins. This means that, in a typical array having 6.25m streamer spacing, the streamer length is 50m.

What is the bollard pull of the system?

A 16-streamer array with 12.5m streamer spacings (largest recommended with #3 Baro or equivalent paravanes) has a bollard pull of about 5.5 tons at 5 knots.

What size vessel is required?

This depends on the size of the array and the configuration of the vessel. A 300m-wide array has been successfully pulled by the R.V. Helmer Hanssen (formerly R.V. Jan Mayen), operated by Tromso University. This vessel is 64m in length with a 13m beam. Smaller arrays can be pulled by smaller vessels; a survey conducted by Fugro West off California, using fourteen 50m arrays at 6.25m spacing (~80m swath), was easily accomplished using the R/V Bluefin. This vessel is 53m long with an 11.5m beam. NCS Subsea successfully completed a program in the Gulf of Mexico with a system consisting of 18 100m streamers spaced 12.5m apart; the vessel was the M/V Bjørkhaug. Geometrics can provide a vessel assessment upon request.

P-Cable Deployment

How many People are Required for Deployment?

Four to five people are required, depending on deck configuration and winch control method. Deployment time averages 45 minutes and retrieval time averages 30 minutes.

How does the Deployment Process Look?

Click here to view an animation.

How is the P-Cable Positioned?

There are two options that have been developed specifically for the P-Cable. The first is by DECO Geophysical. The second method was developed by NCS SubSea, Inc. and is based on GPS and digital compass technology. Please contact us for more information

How is depth controlled? Are birds required?

Birds are not used on the P-Cable; again, the overarching philosophy behind the P-Cable is to have as little gear in the water as possible. Depth of the cross-cable is controlled by the length of the buoy rope over each tri-point. Streamers are carefully balanced to be neutrally buoyant, so they tow horizontally at the same depth as the cross-cable.

How is the depth of the array monitored?

A high-resolution depth sensor is housed in each junction box on the cross-cable and in the tail of each section. The depth is reported and recorded after each shot. Accuracy is +/- 10 cm.

What about tail buoys? Are they required?

Tail buoys are not necessary. The streamers are short, and the paravanes are visible during the day and are marked by strobes at night. We do use small, low-profile drogues on the ends of the streamers to keep them straight in the water.

Survey Considerations

What is the maximum depth of investigation?

the P-Cable is useful to the depth at which the required frequencies can be obtained with the optimal source. If your resolution requirements dictate a peak frequency of 200 Hz or more, then the depth at which the peak reflector frequency drops below 200 Hz marks the limit of the P-Cable’s usefulness. The higher the resolution requirements, the shallower the depth of investigation.

How does the Deployment Process Look?

Click here to view an animation.

How fast can the P-Cable system be towed?

We recommend 5 knots maximum.

How stable is the system while under tow? Is cable strumming a problem?

Measured variation in cross-cable depth during the survey is less than +/- .15m. The helical spiral of the cable bundle about the strength member provides enough vortex shedding that, at 5 knots or less, strumming of the cross-cable is negligible. Below is a frequency plot of depth data from all depth sensors in a 12-streamer array over a 4-day period in calm seas. The target depth was 1.2m. Eighty-five percent of the readings were within +/- one standard deviation (0.1m) of the target depth. Ninety-eight percent were within +/- two standard deviations. Total number of readings was over 250,000.

How long do the turns take?

A system consisting of 16 streamers spaced at 12.5m requires about 30 minutes to do a full turn.

What production rate can be expected?

This depends on the width of the array, the vessel speed, and the amount of overlap between sail lines. It is best illustrated by example: A system consisting of 16 streamers spaced at 12.5m (largest feasible with Baro #3 or equivalent paravanes), 5 knots towing speed, and two streamers of overlap would allow 30 km2 of sea surface area to be surveyed every 24 hours. This includes turns, and little if any infill would be required due to streamer overlap. Bin size in this example would be 6.25m x 6.25m.

 

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