Geohazards remain to be a significant risk-driver in deepwater oil and gas developments. However, there are no industry standards and few guidelines for managing deepwater risk. This paper presents a method for an iterative process which quantifies geohazard risk. The method takes into account facility vulnerability, geohazard probability and the impact on the development. The quantified geohazard risk assessment identifies the geohazard challenges for deepwater project feasibility and the potential major cost drivers. The approach provides an auditable process for evaluating the benefits and costs of risk reduction measures and environmental compliance. Furthermore the assessment shows which particular geohazards contribute most to the total project risk allowing operators to focus their resources on the geohazard that matters most.
Oil and gas developments in deepwater face new challenges every year, both on technical issues such as facility and well engineering as in the unknowns of the physical processes, soil conditions and environments that occur at large water depths. Many recent highprofile deepwater developments continue to encounter major geological hazards (i.e. geohazards) on an increasing scale.
The significance of geohazards depends on the nature and intensity of the hazard and the engineering performance or vulnerability of the structures that they interact with: some geohazards present a challenge to project feasibility or impose significant additional costs, whilst the effects of others can be mitigated by appropriate facility engineering design.
Historically, geohazard-induced losses to the onshore oil and gas industry exceed many hundreds of millions of dollars through replacement costs, contractual claims and loss of production. In the offshore environment, geohazard-induced losses are potentially far greater as a result of damage to well casings, seabed facilities, pipelines and platforms (e.g. the damage to seabed facilities and losses in the Gulf of Mexico caused by Hurricane Ivan in September 2004). The potential losses are further compounded by the higher capital investments, intensive use of new technology and bigger platforms putting more investment and lives at risk.
Geohazards, especially in deepwater, can be an important contributor to the total project risk. This has prompted several leading operating companies to assemble an expert Geohazard Assessment Team (GAT) to evaluate the level of geological and geotechnical complexity of proposed development sites early on in the project. A key feature of the GAT is the integration of experts from key disciplines (geomorphology, geology, geophysics, geotechnics) to conduct a systematic interpretation and analysis of geohazard risk; the method developed by the GAT provides a framework for estimating:
the frequency at which different geohazard events could be expected to cause loss to the project; and
the level of financial loss associated with the different geohazard events.
The evaluation of geohazard risk is an iterative process throughout the development programme. A key output of each iterative phase of the geohazard risk assessment (GRA) is to highlight the uncertainties in data and knowledge and to make appropriate recommendations for geophysical data acquisition, geotechnical investigation, in-situ monitoring and further analytical work.
