No abstract

TOTAL have recognised the fact, that there has been a need to put more focus on the environmental aspects associated with major accidents hazards. Major accidents as defined by the Offshore Installations (Offshore Safety Case) Regulations 2015 have been specifically assessed by the UK affiliate to identify if they could result in a Major Environmental Incident(s) (MEIs); in line with the EU Directive 2004/35/EC on environmental liability with regard to the prevention and remedying of environmental damage. Hydrocarbon releases of over 1,000bbls have therefore been modeled using the OSCAR software for events such as topside / subsea releases and wells blow outs in order to define fate and location of hydrocarbons from these releases. The exposure/effect (acute mortality, population loss, quantity of oil reaching/endangering shoreline habitats) of the releases on Valued Ecosystem Components (VECs) has then been assessed to define restitution time of the relevant organisms/habitats. Results of the modeling have been assessed so that any event that has a potential effect on the VECs classed by the Company as "Catastrophic" (>3years restoration time) or above is classed as MEI. The incidents not identified as MEIs are then screened along with other liquid releases using a complementary method. This method utilises a matrix to define the environmental severity, based on the volume and toxicity of the release as well as the sensitivity of the marine environment and when relevant (shoreline) the extent of the release. The above Offshore Safety Case regulation defines Safety and Environmental Critical Elements (SECEs) as "parts of an installation where either (a) failure could cause or contribute substantially to a major accident or (b) it has a purpose to prevent, or limit the effect of, a major accident". For major accidents potentially resulting in MEIs, a review of existing barriers was undertaken to demonstrate their adequacy and sufficiency. As an outcome of this process, Critical Elements performance standards were reviewed and amendments proposed as required.

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.

An Environmental Risk Analysis (ERA) was conducted as a pilot study on the Dalia Total FPSO (Floating Production and Storage unit) in Angola located at about 135 km off the coast with complex subsea installations at 1400m depth. The environmental damage and its frequency resulting from the drift and fate of oil depend on many physical, chemical and environmental parameters like the location and composition of the spill, oil weathering, complex and variable surface wind and current patterns, weather conditions, sensitivity of the environmental resource etc…The detailed ERA can only be done if one can estimate the probability of a given quantity of oil to reach an environmental resource and the resulting environmental damage. The possibility to use 3D oil spill drift simulation to fulfill these technical requirements and fit with the Total HSE Reference Framework and risk Matrix is tested. The TOTAL HSE Reference Framework requires that technological risk assessments are carried out for all installations. Based on the technological risk assessment of Dalia FPSO, accidental spill scenarios were compiled and aggregated to a set of most representative scenarios including one blow out case. For each spill scenario, oil drift simulations were conducted in stochastic mode with the OSCAR model developed by Sintef i.e. repeated 246 times for a period of 5 years where met-ocean data were available. Quantities of oil and associated probabilities of presence were calculated for each cell of the model. Environmental target were identified and positioned within a Geographical Information System (GIS) also used in simulations. Environmental damages were estimated based on the MIRA method. Based on these data accidental spill scenarios could be positioned on the Total risk matrix. The pilot results as well as the acceptability of the uncertainties related to this approach are discussed.

Summary The knowledge in real time of the concentration fields resulting from the accidental release of a hazardous substance would be extremely valuable information as support for emergency actions and for impact evaluation on the industrial site itself and its vicinity. For that purpose, a modeling platform is being developed and applied to simulate in real time the atmospheric dispersion of a hazardous substance at the scale of the industrial site and also of its surroundings. The industrial site of Lacq (France) has been chosen as a pilot, and the key hazardous substance considered in this study is hydrogen sulfide (H2S). A 3D computational-fluid-dynamic (CFD) model (Fluidyn-Panepr) has been chosen to simulate the 3D wind-field pattern on the industrial site, taking into account the details of the installations. This approach enables a simulation as close as possible of the turbulence and flow around the buildings that could not be achieved with a standard Gaussian approach. For that purpose, a detailed numerical model of the Lacq installation was built on the basis of a thorough review of the existing installations and an evaluation of their size and "porosity." Wind fields were calculated for a set of predefined boundary conditions based on the climatology of the site. Investigations were carried out to ensure that site information systems could deliver the information available from the H2S sensors and on-site meteorological station in real time. The real-time approach is made possible by the use of a complete wind-field precalculated database automatically selected in case of accidental release by comparison with real-time wind-direction and -speed measurements from the meteorological station located on the industrial site. The location and intensity of the source term are determined using a probabilistic approach (Bayesian inference), making use of both real-time measurements and precalculated concentration responses from unitary emissions (puffs) on sensors. This approach was validated successfully using a limited number of sensors and sources but with the complex structure and flow patterns expected on the site. The activation of the simulation platform is triggered by the detection of threshold concentrations at the sensors. The estimated source term is then used in forward dispersion mode to simulate the dispersion in (fast) Lagrangian puff mode. The modeling platform will be validated through measurement campaigns with a neutral species in 2010.