Integrated Geohazard Risk Assessment for Offshore Operations Combining Multiple Data Sources

Offshore drilling operations in continental and ultra-deep waters are mandatory to guarantee energy security and perform CCUS activities to reduce the environmental impact of O&G Industry.
However, offshore environments are related to high levels of risk that must be taken into consideration during operation planning. This is mainly because of shallow and buried geohazards that could potentially occur and affect asset integrity and operations, with time and economic losses, damage to equipment and in extreme cases environmental issues and human losses.

ENI has developed a workflow in accordance with IOGP standards for offshore drilling operations to identify and characterize natural hazards on and below the seafloor and eventually provide solutions to meet the project requirements for different departments (e.g. Exploration, Engineering, Drilling and Completion). This goal is achieved through continuous analyses and integration with bathymetric, seismic, geotechnical, satellite data and well-logs.

The workflow investigates two different domains, seafloor and sub-seafloor, both at regional and local scale.
The seafloor domain is examined through the computation of morphometric attributes to detect and characterize obstacles like boulders and depressions along the seabottom, perform heterogeneity analyses and identify preferential flow-paths. A flow analysis is further developed internally to estimate the energy of debris flows against the assets in terms of velocity and excess density.
The sub-seafloor domain is investigated by means of seismic interpretation and seismic attribute computation from available data to identify and characterize buried faults and landslides, hard-grounds and seismic anomalies possibly related to oil or gas spikes. Direct Hydrocarbon Indicators are further evaluated to classify the seismic anomalies in terms of negligible, low, moderate or high gas risk.
Open-source SAR images are then interpreted to detect natural oil seeps in the environment and link them to geological objects like salt diapirs, faults and fracture networks.
This allows a better understanding of the migration paths of natural oil and gas to the surface mitigating also the possible environmental impact.
Field data like CPTUs and core-logs are interpreted to detect buried landslides or local hard grounds and estimate geotechnical parameters of the shallow soil cover up to 30 m. These results are further implemented to perform a slope stability analysis and risk zonation close to the facilities.
In conclusion, cross-sections, detailed slope analyses and statistics are performed to detect geohazards close to the well location and along the pipeline route.
If available, well-to-well correlations are investigated by means of well-logs to identify different soil units.

All these results are collected into a final report comprehensive of geomorphological, bathymetric and slope maps. The report contains also a top-hole prognosis indicating all the geohazards crossed by the asset to support offshore operations.

Geohazard studies are continuously updated from the exploration to the development phases of the project to obtain a complete and functional knowledge of the area of interest as new data are available.
This integrated approach has been effectively applied to different scenarios, significantly reducing the uncertainties and allowing the quick detection and management of geohazards to mitigate the risks of offshore activities.