Stages of an offshore engineering survey: how the foundation of a marine project Is built

Before a foundation for an offshore drilling platform, wind turbine, or pipeline appears on the seabed, a less visible, but critically important, phase begins: engineering investigations. These studies make it possible to assess how safe and economically viable a project is, and to determine where and how it should be implemented.

Offshore engineering investigations are a multi-stage process, in which each stage has its own role and set of tasks. A typical workflow looks as follows.

1. Preparatory stage: desk study

Collection and analysis of all available data for the project area, including:

• historical geophysical and geotechnical data;
• nautical charts, sailing directions, and archived meteorological and wave records;
• satellite imagery, publications, and data from previous surveys.

Objective: to form an initial understanding of the site and identify potential risks.

2. Hydrographic and geophysical surveys

At this stage, the seabed relief and subsurface structure are investigated:

• bathymetry (measurement of water depths and seabed morphology);
• sub-bottom profiling (investigation of geological layers beneath the seabed);
• seismic and magnetic surveys (detection of obstacles, pipelines, deposits, or anomalies);
• ROV inspections (visual inspection of specific seabed objects or features).

Objective: to identify geological and engineering hazards such as palaeochannels, soft sediments, boulders, wrecks, and other obstructions.

3. Geotechnical investigations

Following the geophysical surveys, specialists proceed with soil sampling and testing:

• borehole drilling and sampling (CPT, vibrocore, box core, etc.);
• laboratory testing of the physical and mechanical properties of the sediments;
• development of a site-specific geotechnical model, including bearing capacity and settlement assessment.

Outcome: engineers can determine the type, dimensions, and expected performance of the foundation (or pipeline) under the given conditions.

4. Hazard and risk assessment

Based on the integrated survey results, the following are prepared:

• a geological hazard map (karst features, faults, gas-charged layers, etc.);
• risk assessments for the installation of piles, pipelines, or cables;
• recommendations for the location of the structure or for route adjustments.

5. Data interpretation and delivery

A key final stage that includes:

• integration of all datasets into a single report;
• preparation of maps, models, and profiles;
• technical consultations between engineers and the client;
• delivery of data in formats suitable for design and engineering use (for example, for CAD or GIS systems).

An error at any stage can result in cost overruns, schedule delays, or even project cancellation. For example, an unidentified palaeochannel or a landslide-prone slope along a cable route can lead to structural deformation or operational failure. This is why offshore surveys require a clear methodological approach and a high level of accuracy.

Companies that invest in comprehensive offshore site investigations save millions during the construction phase and significantly extend the service life of their assets.