Submarine Landslides—Stability Analysis and Risk Assessment for Offshore Developments

Abstract

Abstract As oil and gas developments move into deeper waters, potential exposure to geohazards becomes an important project risk driver. Landslide deposits and features observed on the seabed in the vicinity of potential future development indicate processes that were active in the geological past and can be expected to continue in the future. Rapid yet spatially extensive analysis of landslide risk is a key requirement of the geohazard assessment for many oil and gas developments, with an aim to provide an estimate of the annual probability of slope failure across the entire proposed development area as an input to the QRA. Well‐established methods exist for probabilistic assessment of slope stability through GIS‐based application of a limit equilibrium infinite slope geomechanical model. Shear band propagation is an effective mechanism to explain large landslides observed in the sediment record that cannot be explained through limit equilibrium alone. A novel GIS‐based probabilistic slope stability assessment using SBP approach allows for improved pixel‐based estimates of the annual probability of failure for a variety of observed landslide mechanisms, such as slab, spreading, ploughing and run‐out failures. This GIS‐based tool has been successfully employed as part of a landslide risk assessment of the ACG development, Caspian Sea, contributing to a landslide risk score for each geohazard province within the area.