Oil Spill Model Research Articles

Distribution and hydrodynamic model of the Keumdong oil spill in Kwangyang Bay, Korea

Oil concentrations in the seawater, seabed sediments, and shoreline sediments were measured from the samples collected 165 days after the Keumdong oil spill accident, which had occurred in Kwangyang Bay of the South Sea, Korea in September 1993. Distribution patterns of the concentrations in the seabed and shoreline sediments have allowed us to hindcast the transport and fate of the spilled oil. Overall, the patterns agree better with the southward (seaward) surface water circulation than with the northward (landward) bottom water circulation over the region. Rapid, initial dispersal of the spilled oil to the south and its subsequent grounding onto the intertidal seabed sediments, as well as onto the shorelines, appear to have made ineffective the subsurface oil transport by the bottom current.

DISPLAY OF SITE CHARACTERISTICS VIA POSTER ILLUSTRATION FOR OIL STORAGE FACILITIES: FLORIDA POWER & LIGHT CASES

ABSTRACT Florida Power & Light (FPL) is creating posters for its bulk oil storage facilities that graphically illustrate various site characteristics important in preparing and responding to an oil spill event. The posters provide valuable information in a concise visual format that minimizes the necessity to utilize numerous support documents. The posters incorporate oil storage facility area information including environmentally sensitive areas, shoreline types, bathymetry, currents, area infrastructure (roads, pipelines), digital and ortho-photos, and historical wind conditions. In addition, the posters provide oil spill preparedness maps using stochastic results (multi-trajectory runs) from FPL's Spill Impact Model Analysis Package (SIMAP) oil spill model. These consolidated maps show potential oil impact areas and dissolved aromatic concentration plumes over various timeframes from the beginning of the spill. Booming strategy and equipment deployment site maps are additional items. Finally, the posters provide important graphical and textual information concerning Incident Command System (ICS) strategic objectives, organizational chart, spill response contacts and phone numbers, and tide data.

OIL SPILL MODELING FOR CONTINGENCY PLANNING AND IMPACT ASSESSMENT AND EXAMPLE APPLICATION FOR FLORIDA POWER & LIGHT

ABSTRACT Important questions that are asked by spill responders as well as those assessing potential impacts are: (I) What is the probability of oiling, above a threshold of concern, for each location near a potential spill site? (2) How soon will oil reach each site of concern? (3) How much oil contamination is expected (on average and worst case)? (4) Is there a potential for impacting biological resources with this oil? Using Applied Science Associates, Inc.'s (ASA) oil spill model (Spill Impact Assessment Package, SIMAP) in stochastic mode, these questions were evaluated for Florida Power & Light (FPL) for a variety of oil types and spill volumes, and for each of FPL's plants and terminals. The model was run many times, randomizing the start time over decade-long wind records. The model evaluates surface oil, shoreline oil, subsurface oil, and low molecular weight aromatics (the most toxic fraction of the oil). Both the mean and worst case exposure thickness/concentration are evaluated. The output includes contour maps, which may be interrogated (with the user interface) to determine the conditions under which worst case oiling occurs. The contours are overlaid on resource maps, showing where resources are most at risk and where protection would be most beneficial. FPL uses SIMAP for contingency planning, drills, spill response, and evaluation of fates and impacts of spills. ASA has developed databases for use in the model for the locations around each of FPL's plants and terminals. These data include shore and habitat type mapping, locations of sensitive resources, and current data sets generated by ASA's hydrodynamic model. The stochastic model may be used as a contingency planning tool or as a component of the ecological risk assessment process. It determines the range of distances and directions oil spills are likely to travel from a particular site, given wind and current data for the area. Practical uses for this information include the determination of which kinds of response equipment should be used in a particular area and where the equipment should be placed to be most effective, what areas are most at risk from possible spills at a specific location, and the expected magnitude of impacts.

ASSESSING ENVIRONMENTAL IMPACTS FROM A PUGET SOUND OIL SPILL

ABSTRACT An oil spill risk assessment determines the likelihood of accident occurrence and potential consequences of a spill when the spill occurs. An essential part of the risk assessment is an environmental impact assessment. The impact assessment identifies resources at risk and examines potential environmental contamination. Computer models can be used in conjunction with resource distributions to predict the impact of an oil spill. This paper provides an overview of the methodology used in assessing environmental impacts from an oil spill and examines various oil spill-modeling tools. The Regulatory Assessment: Use of Tug to Protect Against Oil Spills in the Puget Sound Area (USCG, 1999) includes a Qualitative Environmental Impact Assessment that serves as a case study demonstrating the environmental impact assessment process. The U.S. Coast Guard used this Regulatory Assessment to study the alternatives for improving maritime safety in the Puget Sound area. The following are elements and approaches adopted for the impact assessment:Problem formulation. Problem formulation is a planning and scoping process that establishes the goals, breadth, and focus of the risk analysis. A conceptual model is developed to identify environmental resources to be protected, data needed, and analysis to be used.Analysis. This analysis phase develops profiles of environmental exposure and effects of oil spills. The exposure profile characterizes the ecosystem that may be exposed and describes the magnitude and pattern of exposure.Validation. The validation process is a crucial step in defining the reliability of modeling environmental impacts. The use of several oil spill models can minimize the weakness and assumptions associated with each model. Actual spill incidents provide a range and magnitude of possible environmental damages, which further validate model results.

ACCURATE SIMULATION OF OIL SLICKS

ABSTRACT Over the past three decades, simplified empirical formulas contributed greatly in a rapid evaluation of oil slicks spreading and drifting. In recent years, however, with the development of efficient numerical schemes and enormous improvement of computational resources, new alternatives have appeared. Nowadays oil spill operational models can afford to use more accurate and physically relevant mathematical formulations for the oil slick dynamics simulation. The recently developed Multiphase Oil Spill Model (MOSM) describes the oil slick dynamics within the kinetically coupled two-layer approach. For the upper layer, the oil slick thickness is computed using the layer-averaged Navier-Stokes model, rewritten as the quasilinear mass-transport equation. The lower layer is represented by the oil droplet mixture in the wave-mixing layer of the water column. The oil horizontal movement within the slick and the mixing layer is calculated using a highly accurate numerical scheme. The theoretical model is verified against most popular empirical formulas. The model is used to explore the combined influence of wind and shear currents on the oil slick evolution.

THE DEVELOPMENT OF OIL SPILL MANAGEMENT SOFTWARE

ABSTRACT Oil spill countermeasure actions are combatants, and spilled oil is the enemy. A good operation map at the oil spill response plays a keystone role for victory as military combats. Various complicated geographical information—spill location, damaged areas, natural resources and positions of response resources like skimmers, booms and vessels—are involved in a spill situation. The development of Geographical Information System (GIS)-based spill management software was studied in the project entitled Computerized Oil Spill Response Support System in Korea, by Korea Ocean Research & Development Institute (KORDI) in cooperation with the Korea Maritime Police Agency (KMPA) and the Korea Environmental Science & Technology Institute (KESTI). The spill management software was developed to implement computer operation maps of oil spill countermeasures on the desktop of spill responders. Spill responders can draw the spill positions, damaged areas, and locations of response. The management of cleanup activities is another important role of this software. The users of this software can record every response activity with the time, location, and input amounts of resources, which allow for the evaluation of response activities and estimation of cleanup costs. Fisheries damage also can be assessed using the preimplemented aquaculture field database. The integrated oil spill model can predict oil trajectory of future with computer graphics animation. Moreover, Environmental Sensitivity Index (ESI) maps are included so spill responders can determine operational priority efficiently using the ESI and trajectory model predictions. This software is expected to give a great efficiency to spill responders and to be a good solution to manage oil spills.

Achieving an Industry Standard in the Assessment of Environmental Risk: Oil Spill Risk Management and the Mira Method

ABSTRACT A quantitative approach to assess environmental risks from offshore petroleum activities is developed in this paper. Taking into account both reservoir- and project-specific data, different kinds of oil spill scenarios are analyzed. Oil characteristics and weathering properties are incorporated in a standardized geographical information system (GIS)-based oil spill modeling system, simulating oil trajectories based on wind and current data. Mapping of environmental resources is combined with a sensitivity evaluation and protection value classification. Nationally accepted criteria in Norway for identification of valued ecosystem components (VECs) are adopted to select a limited number of high priority risk indicators. Oil spill statistics are combined with occurrences of VEC resources on a seasonal basis. Oil pollution effect and damage keys have been established based on past oil spill incidents and scientific documentation. Impact assessments are based on available specific resource data and provide results related to the recovery potential of each resource component included. The recovery time is adopted as a general stand-alone parameter that allows classification of severity and ecological significance of acute oil pollution incidents. Quantitative risk results are used to describe and rank environmental risks issued from different sources and scenarios, covering different seasons and activity plans. The ranking also is used to identify high priority resources and geographic areas for contingency actions. The variability in presence and vulnerability of natural resources gives the operator the possibility of adjusting activity plans according to the time-window providing the lowest environmental risk. Contingency plans can be designed for and focused on periods or geographic areas with increased risk. The results are further used in combination with oil spill statistics to determine specific requirements for oil spill contingency systems. Requirements for key factors—such as response time, equipment, functional capability, and efficiency with respect to weather, oil type, and oil quantity—also are established. The overall efficiency of contingency systems is assessed and the risk reanalyzed to identify the potential for risk reduction. Further developments are proposed advising that risk reduction should be considered in combination with costs involved in investments, maintenance and exercises, as well as real combat action costs and compensation costs. Cost-benefit could then be assessed for different contingency arrangements, providing a basis for selection of optimal solutions for contingency systems according to the ALARP principle—“as low as reasonably practicable”—where costs of countermeasures are weighted against potential risk reduction.

SIMULATION OF OIL SPILL MOVEMENT IN COASTAL WATERS

ABSTRACT A numerical model for simulating the movement of accidental oil spill in coastal waters has been developed and applied to study its fate. The Oil Spill model is based on analytical formulation considering different parameters that govern the transport and spreading of oil slick such as advection, turbulent diffusion, evaporation and mechanical spreading. Advection is simulated by a Lagrangian algorithm (i.e. tracking the movement of centre of gravity of oil slick under the action of wind and tides in coastal areas). The model has been applied for two different site conditions, one at New Mangalore Port where the tidal currents are weak and another at Sikka creek in Gulf of Kachchh where the tidal currents are strong. The present paper discusses the model and its applications to predict the trajectory as well as the spread of the oil slick under different environmental conditions.

Econometric modelling, estimation and policy analysis of oil spill processes

This paper explores approaches to model specification suitable for empirical investigation of a stochastic oil spill model. We focus on the effects of economic incentive measures on the frequency of oil spills, spill size, and volume of oil spilled. We look into the relationships between parameters that describe the spill generation process and the enforcement effort, using data for the Black and Baltic Seas.

Buoyant Velocity of Spherical and Nonspherical Bubbles/Droplets

An integrated formulation is presented to calculate the buoyant velocity of bubbles/droplets of various sizes. The bubble/droplet shape can be a sphere, ellipsoid, or a spherical-cap. This formulation can be applied to solids, liquids, or gases. The comparison of the calculated results with experimental data shows a good match and that the formulation presented is better than the Stokes law and Reynolds law combination when dealing with bubbles/droplets in a wider range of sizes. This work was developed in connection with oil and gas spill models that have buoyant oil, gas, or gas hydrates, although they can also be applied to other hydraulic engineering problems.

The Relation of Langmuir Circulation Processes to the Standard Oil Spill Spreading, Dispersion, and Transport Algorithms

Most standard oil spill modeling programs neglect the effects of Langmuir circulation (LC). The authors have identified three areas where LC effects may be important in spill behavior. These three areas are spreading, dispersion, and transport. LC will cause the slick to break into windrows when the wind-row formation velocity is comparable to Fay and other spreading forces. Oil dispersion is likely to be enhanced, with droplets carried to greater depth and distributed non-uniformly. Transport velocities for different parts of the slick will vary because of LC, a phenomenon that also occurs because of other factors.

South Arne Field Development: An Environmental Impact Assessment of Oil Spills

The South Arne field being developed by Amerada Hess A/S is located in 60 m water depth approximately 200 km from the Danish mainland, in block 5604/29 of the Danish sector of the North Sea. As part of the development of the field, a comprehensive environmental impact assessment has been carried out, including the assessment of the impact from oil spills. The Danish authorities required that a ‘worst case’ oil spill be chosen as the basis for the assessment on birds and aquatic organisms including plankton, fish eggs and larvae and benthos. A well blow-out at the surface was chosen as the worst case for the impact on birds, and a seabed blow-out for aquatic organisms. The oil spill modelling was carried out with the DEEPBLOW, SLIKMAP and OSCAR models from SINTEF. The modelling identified environmentally sensitive areas which could potentially be influenced by an oil spill. These included the Dogger Bank, western Skagerrak, south-western Norwegian Trench, the eastern German Bight and the Wadden Sea. Historical meteorological and hydrodynamic scenarios were chosen from a long period of records to ensure that the plume passed through the environmentally sensitive resource areas. For birds, a scan of the literature and available databases was made to determine the numbers and species of birds in the areas swept by the surface slick, the number of fatalities was estimated and finally the recovery time for each species population was estimated. The impact on aquatic organisms was estimated using the predicted environmental concentration/predicted no effect concentration (PEC/PNEC) method of the CHARM model. This method is normally applied to continuous discharges, but here has been used to estimate the impact of a transient pollution cloud resulting from an oil spill.

Stochastic Modeling Concepts in Groundwater and Risk Assessment: Potential Application to Marine Problems

Parameter uncertainty is ubiquitous in marine environmental processes. Failure to account for this uncertainty may lead to erroneous results, and may have significant environmental and economic ramifications. Stochastic modeling of oil spill transport and fate is, therefore, central in the development of an oil spill contingency plan for new oil and gas projects. Over the past twenty years, several stochastic modeling tools have been developed for modeling parameter uncertainty, including the spectral, perturbation, and simulation methods. In this work we explore the application of a new stochastic methodology, the first-order reliability method (FORM), in oil spill modeling. FORM was originally developed in the structural reliability field and has been recently applied to various environmental problems. The method has many appealing features that makes it a powerful tool for modeling complex environmental systems. The theory of FORM is presented, identifying the features that distinguish the method from other stochastic tools. Different formulations to the reliability-based stochastic oil spill modeling are presented in a decision-analytic context.

Spatial data quality and sensitivity analysis in GIS and environmental modelling: the case of coastal oil spills

Whilst spatial data quality has been recognised as an important issue in geographical information systems (GIS) and has been studied in some aspects of environmental modelling, it has received scant attention from coastal oil spill modellers. This paper sets out the results of some experiments which show the impact of data quality for bathymetry and shoreline representation on the outputs of the hydrodynamics modelling. Due to the large number of potential sources of error, a synthetic modelling approach has been adopted and includes polynomial trend surfaces, fractals and Gaussian error fields. The results show that spatial data quality does have an impact on coastal oil spill modelling and point to some of the critical areas where sensitivity analyses can usefully be carried out by modellers to specify the quality of data inputs needed for outputs to have fitness-for-use. The methodology points to a reconsideration of the coupling strategies for GIS and environmental modelling which should be exposed to include specific spatial data quality analysis tools.

Oil Spill Modeling towards the Close of the 20th Century: Overview of the State of the Art

The state-of-the-art in oil spill modeling is summarized, focusing primarily on the years from 1990 to the present. All models seek to describe the key physical and chemical processes that transport and weather the oil on and in the sea. Current insights into the mechanisms of these processes and the availability of algorithms for describing and predicting process rates are discussed. Advances are noted in the areas of advection, spreading, evaporation, dispersion, emulsification, and interactions with ice and shorelines. Knowledge of the relationship between oil properties, and oil weathering and fate, and the development of models for the evaluation of oil spill response strategies are summarized. Specific models are used as examples where appropriate. Future directions in these and other areas are indicated

A Numerical Simulation of an Oil Spill in Tokyo Bay

An oil spill accident happened in Tokyo Bay on 2 July 1997. About 1500 m 3 of crude oil was released on the sea surface from the Japanese tanker Diamond Grace. An oil spill model is applied to simulate the fate of spilled oil. The Lagrangian discrete-parcel method is used in the model. The model considers current advection, horizontal diffusion, mechanical spreading, evaporation, dissolution and entrainment in simulating the oil slick transformation. It can calculate the time evolution of the partition of spilled oil on the water surface, in the water column and the sedimentation on the bottom. A continuous source at constant rate is set up as a tanker off the coast of Yokohama. The grid size is 1 km in the calculation domain. The residual flow simulated by a 3-D hydraulic model and observed wind data are used for advection. The simulated distribution of oil spreading agrees well with observations from satellite remote-sensing.

Water-in-oil Emulsions Results of Formation Studies and Applicability to Oil Spill Modelling

This paper summarizes studies of water-in-oil emulsions, their stability, and modelling of their formation. Studies show that water-in-oil emulsions might be characterized into three categories (stable, mesostable and unstable). These categories were established by visual appearance, elasticity and viscosity differences. It was also shown that water content was not an important factor. A fourth category of water-in-oil exists, that of water entrainment, which is not an emulsion. Water-in-oil emulsions made from crude oils have different classes of stabilities as a result of the asphaltene and resin contents. The differences in the emulsion types are readily distinguished both by their rheological properties, and simply by appearance. The apparent viscosity of a stable emulsion at a shear rate of one reciprocal second, is at least three orders-of-magnitude greater than the starting oil. An unstable emulsion usually has a viscosity no more than one order-of-magnitude greater than that of the starting oil. A stable emulsion has a significant elasticity, whereas an unstable emulsion does not. Stable emulsions have sufficient asphaltenes (>∼7%) to establish films of these compounds around water droplets. Mesostable emulsions have insufficient asphaltenes to render them completely stable. Stability is achieved by visco-elastic retention of water and secondarily by the presence of asphaltene or resin films. Mesostable emulsions display apparent viscosities of about 80–600 times that of the starting oil and true viscosities of 20–200 times that of the starting oil. Mesostable emulsions have an asphaltene and resin content greater than 3%. Entrained water occurs when a viscous oil retains larger water droplets, but conditions are not suitable for the formation of an emulsion. Entrained water may have a viscosity that is similar or slightly greater (∼2–10 times) than the starting oil. It was found that emulsion formation occurs at a threshold energy, however this energy has not been accurately defined. Emulsions from many oils have been characterized. This information is used to describe how this process can be accurately modelled and what information gaps exist for complete description of the physical process. The modelling of emulsions is reviewed. A new modelling scheme based on the new physical findings, is suggested.

EMDROPS: An Integrated Tool for Risk Analysis and Response Planning

ABSTRACT It has been pointed out that one of the pitfalls associated with using a combination of computerised oil spill planning tools is the general lack of integration between the different sub-tasks. Det Norske Veritas (DNV) has been developing and using the EMDROPS tool for Environmental Risk Analysis, Response Analysis, and Contingency Planning. EMDROPS employs the MIRA method for Environmental Risk Assessment (ERA), adopted by OLF, the Norwegian Oil Industry Association, thus the results from the ERA can be put directly into the Response Analysis/Response Planning, using the same oil spill and environmental data as used for the ERA. EMDROPS is integrated into a standard GIS (ArcView) which allows the different modules (Oil Spill Modelling, Vulnerable Resources, Environmental Risk Assessment, and Response Planning) to be used in a seamless manner. Some of the data available to the user is the Norwegian Marine Resources Database (MRDB) and an oil spill equipment database which is used by the Environmental Risk Analysis and response effectiveness analysis.

The Evaporation of Oil Spills: Development and Implementation of New Prediction Methodology

ABSTRACT Extensive experimentation was conducted on oil evaporation. The results of the regulation nature of oil evaporation experiments, show that oil is not strictly boundary-layer regulated specifically: (1) the evaporation rate of several oils with increasing wind speed shows that, unlike water, the evaporation rate does not change significantly except for the initial step over 0-level wind; (2) increasing area does not significantly change oil evaporation rate; (3) decreasing thickness does not increase oil evaporation rate; (4) the volume or mass of oil evaporating correlates with the evaporation rate; (5) evaporation of pure hydrocarbons with and without wind (turbulence) shows that compounds larger than nonane and decane are not boundary-layer regulated. The fact that oil evaporation is not strictly boundary-layer regulated implies a simplistic evaporation equation will suffice to describe the process. A simple equation of the form, evaporation = constant × logarithm of time, is sufficient to describe evaporation. The following processes do not require consideration: wind velocity, turbulence level, area, thickness, and scale size. The factors found to be important to evaporation are time and temperature. The equation parameters found experimentally for the evaporation of oils can be related to commonly-available distillation data for the oil. Specifically, it has been found that the distillation percentage at 180°C correlates well with the equation parameters. Relationships enabling calculation of evaporation equations directly from distillation data have been developed. These equations were combined with the equations generated to account for the temperature variations. The results have application in oil spill prediction and modelling. The simple equations can be applied using readily-available data such as sea temperature and time. Old equations required oil vapour pressure, specialised distillation data, spill area, wind speed, and mass transfer coefficients, all of which are difficult to obtain.

OSC2: A Combined ICS Forms, Database, and Trajectory Model System

ABSTRACT The On-Scene Command and Control (OSC2) system has been developed for the U.S. Coast Guard (USCG) under the direction of Headquarters (HQ), Research & Development (R&D) Center, and National Strike Force. The prototype system is now being used by the Atlantic Strike Team (AST) for PREP government-led area exercise use in an evaluation program. The OSC2 system manages the Incident Command System (ICS) forms, an underlying data base of spill response resources, and an oil spill model system, complete with a GIS user interface. An underlying geographic database contains vector maps of the land and water masses and raster marine charts. ICS Divisions/Groups and their Locations are mapped onto this geographic view. Resource allocations can be viewed and changes made both through the map view and the ICS forms view. The system keeps a history of all status changes. The strengths of the system are its adherence to ICS methodology, its complete underlying database structure, and its versatility in combining the map view and the data base view of the response situation and management. The system enables a complete and consistent review of all planned resource allocation for a spill or exercise.