Services

A detailed desk study for a proposed site is probably the single most important phase of any offshore development. It is also the most cost effective, as it utilises information already available including:

• Published geological maps, memoirs and reports
• Published technical papers
• Public domain borehole records
• Topographic maps, aerial photography and satellite imagery
• Previous site investigations

A desk study is performed at an early stage of site appraisal to guide and inform subsequent phases of the site investigation providing:

• Early understanding of potential ground conditions
• Identification of potential geohazards and risks
• Geological and geomorphological history of the site
• Indicative geotechnical parameters for preliminary design
• Locations of existing infrastructure and wrecks
• Identification of the appropriate site investigation tools

Performed as part of the desk study, we have extensive experience in conducting walk-over surveys for siting shore crossings and nearshore renewable energy projects including:

• Site inspections and geological field mapping
• Discontinuity mapping of rock outcrops
• Rock mass rating assessments (RMR/Q/GSI)
• Rock strength estimation

Geophysical and geotechnical surveys are key to ensuring that the risks associated with  offshore developments are suitably managed.  We are experienced in all aspects of scoping, specifying and managing site investigations including:

• Design of geophysical and geotechnical investigations
• Technical specifications, scope of work, and bills of quantities
• Tender review and assessment
• Management and site supervision
• Laboratory test scheduling
• Checking and approval of factual reports

FEED (Front End Engineering and Design) encompasses the conceptual design and engineering scoping for the development. We are experienced in all aspects of geotechnical site evaluation providing input into multi-disciplinary engineering teams including:

• Seabed characterisation
• Distribution and properties of soils across the site
• Geohazard assessment
• Geotechnical parameter selection for design
• Constructability studies for trenching and pipeline burial
• Scoping additional site investigation for detailed design

We are experts in rock mechanics and rock engineering, from site investigation to design and construction including:

• Rock mass ratings and kinematic analysis
• Foundations, slopes and underground excavations
• Rock slope and rock support
• Drilling and grouting
• Rock trenching including cutting, ripping and blasting
• Rock anchor and pile design
• (HDD) Horizontal Directional Drilling

We are experienced in the supervision of offshore geotechnical investigations for oil and gas developments, wind farms, tidal current devices and nearshore wave energy devices. Investigation methods used include:

• Remotely operated subsea rotary coring in hard rock
• Vibrocoring and CPT’s for pipeline & cable route investigations
• Downhole push/piston sampling, CPT’s, & seismic CPT’s
• Deep push CPT’s and jumbo piston cores in deep water
• Rotary coring using Geobore S from Jack-up’s and DP vessels

We design and optimise routes based on the following:

• Distribution of soil types
• Seabed topography
• Geohazards
• Product properties
• Existing infrastructure, debris and obstructions
• Proposed burial methodology

The trenching assessment recommends the most appropriate burial method, and includes:

• Interpretation of site investigation data
• Distribution of soil types and geotechnical properties
• Geotechnical parameters for trenching design
• Selection of suitable trenching methodology
• Suitability and performance of specific trenchers
• Modelling performance to predict speed, tow force and passes
• Prediction of out of straightness and depth of cover

The BAS enables realistic targets for depth of burial to be determined based on the risk of damage to the product over its operational lifetime, and includes:

• Distribution of soil types and geotechnical properties
• Metocean data for erosion risk
• Fishing and trawling risk
• Shipping traffic and anchoring risks
• Cost/benefit analysis of burial to different depths

The selection of trenching method is not dependent on soils alone, as product properties, environmental conditions, burial depth and backfill requirements all have to be considered.  A number of different methods are available including:

• Ploughs (Pipeline and cable)
• Jet trenchers (ROV, tracked, pipe riding)
• Mechanical trenchers (chain cutters and rock wheel cutters)
• Dredging (back hoe, trailing suction hopper, cutter suction)
• Mass flow excavation and clay cutters
• Marinised excavators

We utilise a number of models to predict the performance of trenching tools. These are used for tender scheduling, vessel selection, project engineering and tender evaluation. The parameters derived include:

• Tow force for cable and pipeline ploughs
• On bottom trenching speed
• Trench depth achievable per pass
• Passes required to meet the specified depth of lowering

We have considerable experience providing project support during trenching operations including:

• Review of post trench survey data
• Processing and evaluation of trencher logger data
• Correlating survey and logger data for specification compliance
• Design of remedial trenching options
• Preparation/rebuttal of claims due to unforeseen ground conditions

We provide additional value to trenching site supervision, combining our expertise in geotechnics and trenching  to enable the early identification of issues relating to poor trencher performance or unforeseen ground conditions, including:

• Analysis of post trench survey and logger data
• Monitoring trencher performance against the tender prediction
• Ensuring that the equipment is being operated correctly
• Identifying changes in performance due to soil conditions
• Supervision of remedial trenching options

• ROV jetting in very soft clays and carbonate sands
• Rock trenching in calcarenite
• Chain cutting in dense sands and gravels
• Ploughing in fibrous soils
• Quality of site investigation data provided for cable route design