The Sub-Bottom Imager™ (SBI) uses advanced acoustics to provide a real-time view of the sub-seabed in full 3D, as a continuous longitudinal path measuring 5m wide by 7m depth of seabed penetration. The SBI integrates with industry standard survey software to delineate shallow discrete objects, stratigraphy and geohazards with decimeter resolution. The SBI can be operated from a surface vessel for shallow water, or from Work Class Remotely Operated Vehicle (WROV) for deep water.
The Sub-Bottom Imager uses beam forming and synthetic aperture processing to delineate sub-seabed stratigraphy, buried infrastructure, and buried geohazards with a depth-dependent spatial resolution that is a function of the type of seabed.
Figure 1. Sub-Bottom Imager 465
Figure 2. Sub-Bottom Imager attached to WROV with hydrophone array folded
In linear surveys, as in the case of cable and pipeline surveys, SBI results will be in the form of a 5m wide swathe acquired over many kilometers (Figure 3 to Figure 5 ). For area surveys, which is the approach used in decommissioning surveys, SBI data can be combined in to mosaic (Figure 6). Examples of the data and how the images are interpreted to identify risk are shown below.
Figure 3: SBI Data showing cable in free span due to seafloor scouring
Figure 4: Along track section of a 217mm HVDC cable showing out-of-spec depth of cover owing to outcropping bed rock (centre of image)
Figure 5: Buried objects can pose a threat to the integrity of buried pipes and cables and SBI can identify such threats.
Figure 6: data mosaic used to identify buried objects at a marine archaeology site.
Figure 7: SBI data showing a plan view image of a buried offshore wind farm HVAC export cable, located in the eastern Irish Sea.
Figure 8: SBI data showing a cross-track profile image of a buried offshore wind farm HVDC cable, located in the south eastern North Sea. This 10cm diameter HVDC cable was buried between2m and 3m below seafloor.
Figure 9: SBI survey data acquired in the south-eastern North Sea. This cross-track profile image shows a 28cm HVAC cable bundle buried over 3m below seafloor.
Figure 10: SBI out-of-straightness survey data conducted on a buried pipeline.
Figure 11: SBI out-of-straightness survey data acquired over buried 4 inch and 10 inch diameter flexible flowlines located in the North Sea.
Figure 12: SBI out-of-straightness survey data acquired over buried 4 inch and 10 inch diameter flexible flowlines located in the North Sea. Note that both flowlines are visible within the rock dumped section.
Figure 13. Various SBI anomalies detected.
Pre-Route Engineering Surveys
- Survey of planned pipeline/cable routes to identify obstacles
- Identification of boulders and other submerged items along pipeline/cable route
- Locate and map buried objects and lost infrastructure in the seabed in preparation for removal during decommissioning
Unexploded Ordnance Service Support
- Qualify buried magnetometer targets for size and shape prior to excavation and removal
Pipeline/Cable As-Laid / As-Built Surveys
- Detailed images of pipeline/cable and surrounding seabed to burial depths of 7m
- Verification that pipeline/cable meets burial requirements
- Out-of-straightness determination
- Free span identification
Pipeline/Cable Integrity Surveys
- Accurate detection of areas along pipeline/cable requiring remedial action.
Benefits associated with pipeline and cable surveys:
- The SBI provides accurate and repeatable depth of cover data and clearly shows situations where remedial engineering is required in cases of free span and out-of-straightness
- Provision of accurate location and size estimates of large objects, such as boulders, adjacent to pipelines and cables
- There is no need to magnetize and/or apply a tone to the pipe/cable
- Surveys can be carried out on energized cables
Benefits associated with unexploded ordnance surveys:
- Magnetometer surveys are unable to provide accurate burial depths or provide identification of buried metallic objects. SBI would be used to image identified magnetic anomalies to determine accurate position and assist in identification of objects as being UXO or benign
Benefits associated with decommissioning surveys:
- 100% coverage of the sub-seabed is delivered
- Accurate location and size estimates of buried objects are provided
- Customer is provided with images of the objects for their own interpretation of imaged objects
- 5 x 8 channel hydrophone arrays
- 3 x HF chirp projectors: 4 -14 kHz
- INS/DVL – IXBLUE PHINS or similar
- Folding array for launch/recovery
- 115 volts AC, 50/60 Hz, 6 amp circuit
- 1000 Base-T 1 Gb Ethernet wired connection
- 1 hydraulic JIC4 port @ 2500 psi
- All WROV
- Ligher ROV’s (such as Cougar XT)
- Excluding Observation Class ROV’s
- Minimum operation depth: 3m
- Maximum operating depth: 1,000m
- Survey altitude: 3.5m +/- 0.5 above seabed (nominal)
- Survey speeds: up to 2 knots
- ROV: Most ROV LAR Systems
- Vessel: Trailing Arm Mount