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Libre J.-M.,Total S.A. | Le Guellec M.,Fluidyn Transoft | Tripathi A.,Fluidyn Transoft | Mailliard T.,Fluidyn Transoft | And 3 more authors.
HARMO 2010 - Proceedings of the 13th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes | Year: 2010

The quick identification of contaminant plume sources can greatly enhance emergency response efforts. The critical questions are: Where is the leak? What is the release mass flow? How long is the release duration? Accurate estimation of the source term is essential to predict plume dispersion, manage the emergency planning and mitigate consequences in the surrounding area. Based on limited information provided by a finite and noisy set of transient concentration measurements obtained from real-time gas sensors, the source identification is also complicated by the presence of building obstacles. While high-resolution CFD simulations are available for predicting plume evolution in complex geometries, a Bayesian probabilistic inferential method can provide the probability density function of the source parameters (location, mass flow, release duration, turn on and turn off time) given a set of concentration measurements on the sensor network. The approach considers both measurements and forward model errors in the probability density function computation. This method is coupled with a fast Markov Chain Monte Carlo (MCMC) stochastic sampling method to determine the source term parameters. The developed algorithm avoids wasting time in generating samples from regions in parameter space which contribute very little to the probability density function. It should be noted that the probabilistic methodology can be used in many fields and is used here for time-varying release rates with complex flow conditions. Once a series of MCMC samples has been obtained, summary statistics related to each variable can be built. The results of the event reconstruction indicate the probability of a source being at a particular location with a release rate. When the source parameters have been defined a fast complementary dispersion model can be used to estimate the impact of the toxic release and activate an emergency response. After first validations based on a limited range of parameters but with complex flow patterns, this method is now being validated on a modeling platform through measurements campaigns. The activation of the simulation platform is triggered by the detection of above threshold concentrations at the sensors. The source term calculated is then used in forward dispersion mode to simulate the dispersion in Lagrangian puff mode. The industrial site of Lacq (France) has been chosen as a pilot and the key hazardous substance considered in this project is hydrogen sulphide (H2S). Source


Libre J.-M.,Total S.A. | Tripathi A.,Fluidyn Transoft | Le Guellec M.,Fluidyn Transoft | Mailliard T.,Fluidyn Transoft | And 3 more authors.
SPE Projects, Facilities and Construction | Year: 2011

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. Copyright © 2011 Society of Petroleum Engineers. Source


Libre J.-M.,Total E and P | Tripathi A.,Fluidyn Transoft | Le Guellec M.,Fluidyn Transoft | Mailliard T.,Fluidyn Transoft | And 3 more authors.
Society of Petroleum Engineers - SPE International Conference on Health, Safety and Environment in Oil and Gas Exploration and Production 2010 | Year: 2010

The knowledge in real time of the concentration fields resulting from the accidental release of hazardous substance would be extremely valuable information as support for emergency actions and impact evaluation on the industrial site itself and its vicinity. For that purpose, a modelling platform is being developed and applied to simulate in real time the atmospheric dispersion of hazardous substance at the scale of the industrial site and also on 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 sulphide (H2S). A 3D CFD (Computational Fluid Dynamic) 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 which could not be done with a standard Gaussian approach. For that purpose a detailed numerical model of Lacq installation was built based on a thorough review of the existing installations and 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 in real time the information available from the H2S sensors and on site meteorological station. The real time approach is made possible by the use of complete wind field pre-calculated 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 is determined using a probabilistic approach (Bayesian inference) making use of both real time measurements and pre-calculated 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 above 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 modelling platform will be validated through measurement campaigns with neutral species in 2010. Copyright 2009, International Petroleum Technology Conference. Source

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