Much has been written, often in emotive terms, about the identification, investigation and potential project impact of geohazards.
Experience now shows that they need not necessarily create the concerns that they do. Adopting a systematic approach to quantifying geohazard risk can minimise the time and cost impacts upon any field development.
Based upon experience on projects in most of the world's geohazard prone regions, including:
The Caspian Sea
Gulf of Mexico,
A regional geohazards database
Advanced seismic reprocessing, and inversion imaging
Probabilistic risk analysis
Tailored Data Acquisition
Geotechnical modelling - physical and numerical
Deterministic engineering analysis
Seabed instrumentation and monitoring
In the process, geohazards themselves may be redefined and their impacts reassessed. Soil salt content may for example, have a more detrimental effect on wells and facilities than seabed slope failure. Understanding these phenomena and their engineering impact is key to the process.
The assessment of Geohazards has advanced significantly over the last five years as knowledge, technology and analytical techniques have evolved, but each geohazard -prone project tends to be treated as unique and a bespoke approach adopted. This paper argues that a systematic approach, embracing the sum of existing knowledge and utilising the most appropriate data acquisition and geo-modelling techniques will result in a more cost-effective decision making process regarding the risk, implications and response to any given set of geohazards.
The Advanced Geohazard Evaluation System (AGES) proposed by the authors adopts a step by step approach to assessing sites where Geohazards are known or believed to exist. These steps include:
A geological desk study incorporating input from regional geohazard and geotechnical databases
The use of 3D exploration seismic data enhanced by techniques such as short offset reprocessing and seismic inversion
The creation of a full site 3D Geological/ Geotechnical site model.
Preliminary geohazard risk assessment
The identification and incorporation of key experts required in the evaluation of specific features or processes
The preliminary assessment of risks to all components of a field development, including: wells, subsea structures pipelines and moorings
The design of a reconnaissance site investigation that will optimise the quantification of project risk most cost effectively
The use of advanced, numerical and physical, geotechnical modelling techniques
The design of a full field development site survey and geotechnical investigation
The installation of seabed instrumentation to verify predictions of seabed deformations and pore pressure responses.
Fig 1- Advanced Geohazard Evaluation System (A.G.E.S.) flow diagram (Available in full paper)
The paper concludes with a series of recommendations for oil and gas operators which will help to improve this process even further and maximise their return on investment in geohazard risk assessment.