Offshore structural engineering demands accurate survey of the seafloor: geophysical data provides essential information on the geology of the sub-bottom strata, critical to de-risking the cost-effective design of marine structures and subsea installations.
Gas has strategically-located its branches and provides its highly technical equipment such as research vessels, AUVs, seabed sampling and testing tools. These equipments are operated by our highly skilled international teams of professionals thus providing our worldwide customers with high quality data acquisition, interpretation and presentation.
GAS’ capabilities to conduct highly complicated marine geophysical surveys in a short period of time has lead to huge cost savings for our clients. The use of high tech equipment combined with highly qualified technicians can lead to greater efficiency and hence saving time and cost for our customers.
Innovation, state of the art equipment, efficiency, highly skilled personnel, flexibility, on the spot customer care and tailor made solutions for our customers: our clients can rely on us!
Briefly the services we offer under this category are as follows:
The potential risk during drilling is related to possible shallow gas pockets, pockmarks and faults: safe drilling operations demand special care in seismic acquisition, data processing and interpretation.
GAS, together with the Customers, designs acquisition, processing and interpretation of HRS in order to evaluate any potential risks.
Particular attention is paid to turbid acoustic zones evidences, acoustic blanking obliterating seismic reflections from deeper layers, anomalous amplitude reflections and pull-down effects, bright and dim spots, polarity reversals, chimney effects.
With more than 150 performed High Resolution seismic surveys, GAS has a proven experience in this Service. Rely on GAS skills when your HRS scope demands special care.
The primary objective of an analogue site survey is to define any potential hazard to the Drilling Unit emplacement or to the future operations on the well site. This includes detection of seafloor obstructions, seabed morphology, bathymetry, shallow stratigraphy, seabed soil conditions. The survey involves the acquisition of: DGPS, MBES, SSS, SBP, Sparker or MiniGun, Magnetometer, Seabed soil sampling.
With more than 300 among Well Site and Site Clearance surveys performed, GAS has a proven wide experience in this kind of service.
GAS can satisfy all your site survey needs, providing personnel, equipment, vessels and onboard processing and data interpretation.
The project of a submarine pipeline is a big challenge, not only in terms of complex environmental and geological contexts but also in terms of money. Choosing the best pipeline route and therefore limiting the pre engineering phase is a good way of saving money.
GAS helps Customers to select the preferred route corridor and to confirm the suitability for further detailed investigation establishing seabed topography, morphology and shallow stratigraphy, identifying geohazards and determining soil characteristics.
GAS has built a wide experience in this service, performing important reconnaissance surveys in the Mediterreanean Sea.
GAS provides all the needs for a pipeline reconnaissance survey: permanently mobilized vessels, skilled personnel, SOA equipment and geotechnical testing facilities.
Charting and reporting are carried out onboard on a continuous basis, allowing the Customer to assess seabed characteristics and geological features.
The life and the installation of a submarine cable system is threaten by a variety of features and items such as wrecks, outcrops, areas of unstable seabed, excessive slopes and sea currents.
GAS assists the Customer to design a suitable cable route free of any potential risks, performing all necessary data acquisition and interpretation until an acceptable route is determined.
GAS is able to provide: permanently mobilized vessels, skilled personnel and SOA equipment, comprising CPT for burial assessment. Charting and reporting are carried out onboard on a continuous basis, providing the Customers with ‘ON TIME’ data for quick evaluation and hence quick decision in selecting the right cable route.
The purpose of the Ice Scour Survey is to define ice gouge in terms of length, width, orientation, rise up, incision width, depth and age.
The geophysical investigation is carried out in order to provide information on bathymetry, seabed and sub-seabed details of the ice scours under investigation.
The survey includes acquisition of MBES (Multi Beam Echo Sounder) data, SSS (Side Scan Sounder) data and SBP (Sub Bottom Profile) data
The main purpose of the pre-lay survey is to confirm that no obstructions on the seabed have occurred in the period subsequent to the pre-engineering surveys and to verify the existing design data along the laying corridor.
The pre-lay survey program should allow adequate time prior to the lay, to ensure that pipe lay operations are not delayed.
The main tasks of the pre-lay survey are:
The main purpose of the Anchor Clearance Survey is to identify and position any significant obstruction that may be present in the anchor corridor and to define the seabed characteristics in the same corridor where anchor mooring will be performed.
GAS vessel DP1 Odin Finder (hyperlink a pagina vessel – odin) and Filomena Prima are permanentely mobilized with top of the range equipment required for pre-lay and AC surveys: such equipment is; two hull mounted MBES systems (200-400kHz and 26kHz for shallow and deep water), double frequency Side Scan Sonar, hull mounted 3×4 Chirp Array Sub Bottom Profiler, hull mounted USBL and Magnetometer.
The vessel has a separate room for data processing and interpretation, equipped with PCs, A0 plotters and processing suites . Charting and reporting of interpreted data are carried out onboard the vessel throughout the survey period, hence ensuring fast data delivery to our clients.
The aim of the as-laid survey is to undertake a complete General Visual Inspection by ROV (hyperlink rov page) along the pipeline as soon as the pipeline is laid. The as-laid survey shall define: accurate position of the pipeline, the pipe-seabed configuration (visual and instrumental) and the external status of the pipe.
The as-laid results will be used to confirm/finalise the design of post-lay intervention works. The as-built survey will define the final status of the pipeline and of the post lay intervention works.
The as-built documentation will then be prepared by merging the results of the as-laid and as-built surveys.
The following data shall be gathered during as-laid survey:
Likewise, the as- built survey will be a complete visual and instrumental ROV inspection and the collected data is the same as per the as laid survey.
GAS vessel DP1 Odin Finder and Filomena Prima can be easily mobilized with all the equipment required for as-laid and as-built pipeline surveys: the equipment is; DGPS, hull mounted USBL, and R.O.V.
The R.O.V. can be equipped with Bathymetric Unit, Modular Scanning Profiler, Panoramic Sonar, Motion sensor & Gyrocompass, Center and Boom Color video cameras, Integral Comprehensive Video Overlay with video eventing
Charting and reporting of interpreted data are carried out onboard Odin Finder on a continuous basis throughout the duration of the survey.
In the last decade geophysical survey techniques have proved to be extremely useful for submarine archelogical research, in particular for providing an immediate morphologic reconstruction of the site before the acquisition of visual images by means of divers or underwater cameras.
In addition to the detailed 3D image of the site and the precise positioning of the features by DGPS, geophysical methods can be used to ascertain the site environmental conditions, such as erosion, sedimentation, etc.
Archeological surveys are carried out with different equipment, all supported by DGPS positioning, such equipment is; Multibeam Echosounders, Side Scan Sonars, Sub Bottom Profilers, Magnetometers and ROVs.
Marine Geophysical Surveys can be executed in the preliminary stages prior to planning for subsequent detailed surveys on specific targets.
Geophysical Surveys can be applied to archeology in the following ways:
In addition to these applications, archeological surveys are often required in conjunction to pipeline or cable reconnaissance or detailed surveys. For these activities a qualified senior archeologist will be present onboard during data acquisition (MBES, SSS, SBP, MAG) for archeological target identification and for planning of an eventual visual inspection by means of ROVs.
Geophysical surveys can also be applied for wreck research, investigating the suspected wreck area by MBES surveys before the deployment of SSS/SBP for a closer in look on the wreck area.