Deepwater Surveys Offshore Nile Delta

Until 2000, most offshore exploration activity in Egypt was focused on the shallow waters of the Gulf of Suez.

Since then, the industry’s focus has gradually switched to the Mediterranean Sea and the search for natural gas. Discoveries have stimulated investment and activity has grown rapidly, moving further offshore into deep water.

This increase in activity has allowed Fugro SAE to expand  rapidly in recent years and, in 2008, Fugro SAE acquired its own dedicated survey vessel, M/V Fugro Navigator.
Equipped with industry-leading survey systems, the Navigator has since played a notable role in supporting exploration and development down to water depths beyond of 1000 m.
Projects undertaken include geohazard site surveys for mobile jack-up and semi-submersible drilling rig operations, pre-engineering surveys for platforms, pipelines and subsea fields, as well as environmental baseline and metocean surveys.

The surveys are often ‘multi-discipline’ requiring certain specialised services provided by sister operating companies, such as Fugro Oceansismica, who provide multi-channel geophysical seismic services, Fugro Alluvial Offshore Limited and Fugro Engineers who provide geotechnical services and Fugro Survey Limited who provide environmental services.

Fugro Nafigator

The Fugro Navigator has become a platform from which a wide range of Fugro’s specialist survey services are now delivered to the Egyptian oil and gas market.
Following a recent upgrade and addition of DP capability the Navigator was ready for a new challenge: for the first time, the vessel was to undertake a pre engineering survey with an ROV.

High resolution multibeam echo-sounder and geophysical data were needed for design work of for 200 Kms km of subsea flowlines and several manifolds in water depths from 300 to 700 m, offshore Nile Delta, with its soft unstable soils and severe gradients.

Chrip Data

The survey also included visual inspection of existing subsea production facilities with the ROV.

Project Preparation
A survey skid for Fugro SAE’s Panther Plus ROV was designed and fabricated and then careful selection of survey systems was made through extensive testing, initially in a test tank, and then during offshore trials.

Eventually, an R2Sonic 2024 multibeam echo-sounder and an Edgetech 2400 combined side scan and chirp were selected as the main sensors in addition to ancillary equipment such as doppler velocity log, motion sensor and bathymetry systems.

The weeks spent preparing the survey equipment proved worthwhile as the multi-beam and chirp profiler data sets acquired during the project were excellent with little or no acoustic or electrical interference observed, a common problem when operating geophysical equipment on ROVs.

Multi-Beam Data showing Flowlines and Mattresses

In particular the MBES data was able to pick out features such as cables and pockmarks that would otherwise have gone undetected by sidescan systems..
The sidescan data was compromised by the need to operate the ROV at height above seabed of 40m in order that the multi-beam system would cover a 120m wide corridor.
Therefore, the sidescan data from the towed sidescan system, another Edgetech 2400 system and accurately positioned by the vessel’s HiPAP 500 USBL system, was used for mapping of seabed features.

Towed Sidescan Data

But the 500KHz sidescan data could not match that of the multi-beam, as these images indicate.
The multibeam data shows telecoms cables and control umbilicals running across the site that could not be identified on by either of the sidescan data sets.
The multi-beam data also indicates gradients of over 30° across critical slopes where hull mounted data suggested maximum slopes of 12-15°, critical information for route selection and design.

500 KHz Sidescan Data - Multi-beam Data

Data was processed and detailed field reporting undertaken onboard to allow the client to vary the work scope.
On completion of the geophysical work-scope, the survey skid was removed from the ROV, and the ROV then undertook visual inspections of existing facilities such as flowlines and drilling trees.

Final reporting was undertaken in Cairo where all reporting and processing deadlines adhered to, allowing the client to start the design work on time.

By Fugro Egypt


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