Geohazards and Ocean Hazards in Deepwater: Overview and Methods of Assessment

Drilling for hydrocarbons in the deep marine environment provides a unique setof challenges for industry. Amongst these are the distinct hazards caused bynatural geological and oceanic processes such as: (a) semi-permanent bottomcurrents, (b) episodic turbidity currents, slope instability and mass transportevents (slides, slumps, debris flows), and (c) gas hydrate escape. We presentdata on the nature, effects and assessment of these deepwater hazards,including current velocities, transport/erosion capacities, recurrenceintervals, and hydrate distribution. It is of upmost importance that theoceanographic conditions are carefully considered prior to deepwater operationsto ensure the work can be carried out safely. Thorough risk assessment requiresknowledge of existing bottom currents, an assessment of potential masstransport events and turbidity currents, and understanding of conditions likelyto induce the formation and destabilisation of gas hydrates. Pipelines, cables,subsea installations, key connections such as the riser and any other seabedinfrastructure are all susceptible to damage. Correct assessment of hazard willallow for the right equipment to be used for the operations including blowoutpreventers, riser size, vibration suppressors, and for the safest siting ofcables and pipelines. It will also aid the subsea architecture design andplanning operations with minimal downtime. All these considerations lead to asafer exploration and production while eliminating unnecessary cost.