Consequence Modeling — Dispersion, Fire & Explosion

By Johnson on July 30, 2026

consequence-modeling-dispersion-fire-explosion

Consequence modeling in oil and gas is the quantitative process of predicting what happens when a hazardous material is released from a process vessel, pipeline, or wellhead under specific conditions. Whether the release produces a toxic dispersion plume that reaches a nearby population center, a jet fire impinging on a structural support, a pool fire radiating heat to an adjacent control room, or a vapor cloud explosion generating overpressure that shatters buildings at distance, the model translates a set of input parameters into physical outcomes that can be measured in distance, thermal radiation flux, and explosive overpressure. These outcomes then become the basis for emergency planning zones, equipment spacing, shelter-in-place decisions, and building siting evaluations. The challenge is not that the science is uncertain, but that the input data feeding these models is often outdated, inconsistent, or scattered across systems that were never designed to feed a consequence assessment workflow. iFactory connects the operational data sources that consequence models depend on, from real-time process conditions to equipment inventories, so that scenario inputs reflect current plant state rather than stale assumptions — see the platform at iFactory support.

Consequence Analysis · Oil and Gas Risk Reduction

Consequence Modeling for Dispersion, Fire, and Explosion Scenarios in Oil and Gas Operations

Understand how toxic dispersion, jet fires, pool fires, BLEVEs, and vapor cloud explosions are modeled, what input data each scenario demands, and how model outputs drive emergency zone planning and facility siting decisions.

H2S Dispersion DistanceExceeds ERPZ
1,840 m
ERPG-2 contour extends beyond current emergency planning zone boundary
Jet Fire Radiant FluxAt Threshold
4.7 kW/m2
At 45 meters from release point, approaching 5 kW/m2 structural damage limit
VCE OverpressureWithin Range
0.21 bar
At 120 meters, below 0.3 bar threshold for minor structural damage
Fundamentals

What Consequence Modeling Actually Calculates — And Why It Matters Beyond the Report

Consequence modeling takes a defined release scenario and predicts the physical effects of that release on the surrounding environment. The output is not a single number but a set of spatial contours that describe how intensity diminishes with distance from the release point. For toxic releases, the contours define concentrations at specified threshold levels like ERPG-1, ERPG-2, and ERPG-3. For fire scenarios, the contours define thermal radiation flux levels at specified distances. For explosion scenarios, the contours define overpressure levels that correspond to different degrees of structural and human damage. These contours are then overlaid on facility layouts, population maps, and environmental receptor locations to determine whether existing or proposed safeguards provide adequate protection.

Distance to ERPG-2
The maximum downwind distance at which toxic gas concentration exceeds the level that could cause irreversible or serious health effects for a one-hour exposure, defining the boundary for shelter-in-place or evacuation decisions.
Thermal Radiation Flux
The intensity of heat radiated from a fire measured in kilowatts per square meter at specified distances, used to determine safe separation distances for personnel, structures, and equipment.
Explosion Overpressure
The pressure wave generated by a detonation or deflagration measured in bar or psi at specified distances, used to assess structural damage potential and personnel injury risk at receptor locations.
Flammable Gas Extent
The spatial boundary within which a released gas is within its flammable range, defining the area where an ignition source could produce a vapor cloud explosion or flash fire.
Scenario Classification

Five Release Scenarios Every Oil and Gas Facility Must Model for Regulatory and Operational Readiness

Not every release scenario produces the same type of hazard, and the modeling approach, input data requirements, and output metrics differ significantly across scenario types. A high-pressure gas release from a compressor station presents a fundamentally different modeling challenge than a liquid spill from a storage tank farm. The following five scenarios represent the core set that most oil and gas operators are expected to evaluate as part of their process hazard analysis, facility siting studies, and emergency response planning.

01
Toxic Gas Dispersion
Upstream wellheads with H2S, sour gas processing plants, natural gas pipelines with mercaptan or H2S contamination
A pressurized toxic gas is released and disperses downwind under atmospheric conditions defined by stability class, wind speed, and terrain. The model calculates concentration as a function of distance and time, producing contours at specified toxicity thresholds.
ERPG-1, ERPG-2, ERPG-3 contour distances, time to reach threshold at specified receptor locations, plume width at downwind distances
02
Jet Fire
High-pressure gas pipelines, compressor seal leaks, wellhead blowouts with immediate ignition, flange leaks on gas processing equipment
A pressurized gas or flashing liquid release ignites at the release point, producing a turbulent flame jet that extends downwind. The model calculates flame length, flame tilt angle, and thermal radiation flux as a function of distance from the flame envelope.
Flame length and tilt angle, thermal radiation contours at 1.6, 4.0, 6.3, and 12.5 kW/m2, safe separation distances for personnel and structures
03
Pool Fire
Liquid hydrocarbon storage tanks, containment basin spills, liquid pipeline ruptures where pooled product accumulates and ignites
A liquid release forms a pool on the ground or within a containment area, and the pool surface vapor ignites either immediately or after a delay. The model calculates burning rate, flame height, and thermal radiation as a function of pool diameter and distance.
Burning rate and flame height, pool diameter over time, thermal radiation contours at specified flux levels, duration of fire based on pool volume and burning rate
04
Vapor Cloud Explosion
Gas processing plants, LNG facilities, refinery units where a flammable cloud forms in a congested area with ignition sources present
A flammable gas release forms a vapor cloud that disperses into a congested or confined space before igniting. The model calculates overpressure generated by the deflagration, accounting for flame acceleration caused by obstacles, piping, and structures in the cloud path.
Overpressure contours at 0.02, 0.07, 0.14, 0.21, and 0.3 bar, drag and dynamic pressure from the blast wave, structural damage assessment at receptor locations
05
BLEVE
Pressurized liquefied gas storage vessels such as LPG bullets, propane spheres, and pressurized refrigerated storage exposed to external fire
A pressurized liquid-filled vessel is exposed to external fire that weakens the vessel shell until it fails catastrophically. The sudden depressurization causes the liquid to flash, producing a fireball and fragmenting the vessel into projectiles. The model calculates fireball diameter, duration, thermal radiation, and fragment reach distances.
Fireball diameter and lift-off height, thermal radiation contours, fireball duration, fragment range and lethality zone for vessel projectiles
Data Dependencies

Input Parameters That Determine Whether Your Model Reflects Reality or Fiction

The quality of a consequence model output is entirely determined by the quality of its inputs. A dispersion model run with an incorrect wind rose, an overstated release rate, or a wrong atmospheric stability class will produce contour distances that are either dangerously conservative or dangerously non-conservative. The following parameter categories represent the data inputs that have the greatest impact on model accuracy, and the ones that are most frequently sourced from outdated or inconsistent data in oil and gas operations.

Release Conditions
Operating pressure, temperature, phase, composition, release orientation, and orifice size at the time of failure. These parameters define the initial discharge rate and phase behavior of the released material, and small changes in pressure or orifice size can produce large changes in downwind hazard distances.
High Impact
Material Properties
Molecular weight, vapor pressure, heat of combustion, lower and upper flammable limits, toxicity thresholds, and liquid density. These properties are well characterized for pure components but become uncertain for complex mixtures, particularly crude oils and natural gas liquids with variable composition.
High Impact
Atmospheric Conditions
Wind speed, wind direction distribution from site-specific meteorological data, atmospheric stability class, ambient temperature, and humidity. Using generic stability class assumptions instead of site-specific wind rose data is one of the most common sources of modeling inaccuracy in dispersion assessments.
High Impact
Terrain and Obstacles
Ground elevation profiles, building heights and orientations, process equipment density, and congestion density for explosion modeling. Simplified flat-terrain assumptions can significantly misrepresent dispersion in terrain with valleys, ridges, or elevated process equipment that channels or blocks plume movement.
Medium Impact
Ignition Source Mapping
Location and strength of potential ignition sources within the flammable gas extent, including electrical equipment, hot surfaces, vehicles, and open flames. For delayed ignition scenarios, the probability and timing of ignition directly determines whether the outcome is a dispersion event, a flash fire, or a vapor cloud explosion.
Medium Impact
Receptor Locations
Occupied buildings, control rooms, site boundaries, public roads, residential areas, schools, hospitals, and environmentally sensitive areas. Accurate receptor mapping ensures that model contours are evaluated against the correct population and asset locations rather than approximate or outdated facility layout drawings.
Medium Impact
Modeling Software

Consequence Modeling Tool Landscape — Which Approach Fits Which Scenario

The oil and gas industry uses a range of consequence modeling tools that differ in their underlying calculation methods, level of geometric complexity, and computational requirements. Choosing the wrong tool for a scenario type, or applying a simplified model to a situation that demands high-fidelity geometry, can produce results that misrepresent the actual hazard extent. Understanding the strengths and limitations of each tool category is essential for building a consequence modeling program that produces defensible results for regulatory submissions and operational decisions.

Integral Gaussian Models
PHAST, SAFETI
Use analytical solutions to the Gaussian plume equation for dispersion and empirical correlations for fire and explosion scenarios. Fast computation, suitable for screening-level studies and large scenario matrices. Limited ability to account for complex terrain, obstacle effects on flame acceleration, or three-dimensional building interactions.
Dispersion screening, jet fire and pool fire sizing, large-scale QRA scenario matrices
Computational Fluid Dynamics
FLACS, OpenFOAM, ANSYS Fluent
Solve the Navier-Stokes equations on a three-dimensional grid to model fluid flow, mixing, combustion, and blast wave propagation. Can account for complex geometry, congestion, confinement, and terrain effects. Computationally expensive, requiring significant setup time and domain expertise to define grids, boundary conditions, and turbulence models.
Vapor cloud explosions in congested modules, tunnel or canyon dispersion, BLEVE fireball dynamics
Phenomenological Models
TNO Multi-Energy, Baker-Strehlow-Tang
Semi-empirical methods for vapor cloud explosion overpressure estimation based on the energy of the flammable cloud and the degree of congestion and confinement. Faster than full CFD but require engineering judgment to select appropriate blast strength parameters for the congestion category being evaluated.
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