ERA Acute – A Multi-Compartment Quantitative Risk Assessment for Oil Spills

Abstract

Awareness of environmental risk and the demand for oil spill response planning associated with offshore marine operations has increased during the last decades. Environmental Risk Assessments (ERAs) are a crucial part of planning and execution of oil and gas (O&G) activities offshore. A sound ERA can support the O&G industry in environmental risk management (ERM) of operations. Authorities and Operating companies have requested updated methodology based on more recent research from oil spill events such as the Deep Water Horizon incident, with the possibility to perform more detailed analyses in e.g. sensitive areas. ERA Acute is developed to meet these requirements. It is a transparent method of quantitative analysis for environmental screenings, ERAs and Net Environmental Benefit Analyses (NEBAs) of oil spills in four compartments: Sea surface, shoreline, water column and sea floor. The methodology is grid-cell based and results can therefore be shown in a geographical information system (GIS) for any region globally. The user can identify areas of high risk - for use in decision support and spill response planning - independently of the region. Three levels of detail are defined, depending on availability of VEC data, suitable for screening purposes or more detailed studies. Calculations are carried out in two main steps: First, ERA Acute uses input from an oil spill fate and distribution model of choice to calculate exposure and impact to Valued Ecosystem Components (VECs) in each grid cell and for each simulation. Calculations follow a common methodology framework, applying different mechanisms of impact and recovery for each compartment. Impacts are summarised, and in the second step, potential lag-and/or restitution time and risk are calculated for each VEC. The resulting resource impact factor (RIF) is an index that combines the extent of impact and recovery time. A statistical approach is used, based on numerous oil spill simulations covering each season in order to capture variations in spill drift and fate, species abundance and vulnerability. This paper describes the method. ERA Acute methodology is validated in sensitivity studies, field validations, comparison to relevant ERA methods, and documented in several dissemination steps including a guideline for best industry practice. The ERA Acute project is carried out by a consortium of industry partners (Statoil, Total, Norwegian Oil and Gas Association) and experts in environmental risk analysis (Acona, Akvaplan-niva (project manager), DNV-GL and SINTEF), supported by the Research Council of Norway.