Geohazards and ocean hazards in deepwater: overview and methods of assessment

Drilling for hydrocarbons in the deep marine environment provides a unique set of challenges for industry. Amongst these are the distinct hazards caused by natural geological and oceanic processes such as: (a) semi-permanent bottom currents, (b) episodic turbidity currents, slope instability and mass transport events (slides, slumps, debris flows), and (c) gas hydrate escape. We present data on the nature, effects and assessment of these deepwater hazards, including current velocities, transport/erosion capacities, recurrence intervals, and hydrate distribution. It is of upmost importance that the oceanographic conditions are carefully considered prior to deepwater operations to ensure the work can be carried out safely. Thorough risk assessment requires knowledge of existing bottom currents, an assessment of potential mass transport events and turbidity currents, and understanding of conditions likely to induce the formation and destabilisation of gas hydrates. Pipelines, cables, subsea installations, key connections such as the riser and any other seabed infrastructure are all susceptible to damage. Correct assessment of hazard will allow for the right equipment to be used for the operations including blowout preventers, riser size, vibration suppressors, and for the safest siting of cables and pipelines. It will also aid the subsea architecture design and planning operations with minimal downtime. All these considerations lead to a safer exploration and production while eliminating unnecessary cost.