a novel approach to simulate the complex dynamics of oil ... · contribution from neighboring...

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A NOVEL APPROACH TO SIMULATE THE COMPLEX DYNAMICS OF OIL SPILLS ON LAND

Jeremy Fontenault - RPSCo-Authors: Anusha Dissanayake, Tara Franey - RPS5/16/2019

Overview

• Need for spill modeling

• Traditional approach for modeling spills on land

• Drivers for more complex modeling

• Advanced Overland Modeling Approach: Particle-based model Advanced oil weathering Infiltration

2Complex Overland Modeling

Need for Oil Spill Modeling on Land

• High Consequence Area (HCA) Analysis

• Permitting

• Routing

• Engagement

• Response Planning

• Risk Management

• Environmental & Human Health Impact Assessments

Regulations:

Pipelines49 CFR part 195 (US)CSA Z662-11 (CAN)

Facilities40 CFR part 112

Rail49 CFR parts 107-174


Traditional Approach• Steepest downslope pathway

• Simplifying assumptions: Flow velocity Path width Static product density/viscosity Loss terms (adherence, evaporation, etc.)


Pros:• Fast simulations• Can run thousands of

simulations• Generally, a conservative

prediction

Cons:• Simplified overland pathway• Challenges with complex

terrain• Basic weathering of released

liquid

Drivers for More Complex Modeling

• Under a higher level of scrutiny

• More complex questions are being asked by regulators and stakeholders:

Could a release take multiple downslope flow paths?

How do the physical changes to the oil over time impact the potential trajectory, fate, and effects?

How could outcomes vary for the different products transported?

What is the potential for impact to ground water?


Source: inhabitat.com

Source: Ellen Schmidt, MPR News

New Approach for Advanced Overland Spill Modeling

Smooth Particle Hydrodynamics (SPH)

• Particle-based approach to simulate complex flow

Advanced Weathering• Accurate predictions of trajectory,

fates, and effects for the specific product released

Infiltration• Potential ground water impacts


Source: 350.org

Smooth Particle Hydrodynamics (SPH)• First developed in the field of astro-physics• Has been used to solve many flow problems:


• Each particle has its own: Volume, Mass, Physical properties, etc.

• Particle Movement Independent Contribution from neighboring particles using a kernel function

Lava Dam break

Waves Oil transport

• Liquid represented by discrete particles• No mesh/grid required

Source: Jan Bender and Dan Koschier, "Divergence-Free Smoothed Particle Hydrodynamics", In Proceedings of ACM SIGGRAPH / EUROGRAPHICS Symposium on Computer Animation (SCA), 2015

8

SPH Inputs

Complex Overland Modeling

Digital Elevation Model (DEM)• Derives slope and aspect• Define flow trajectory and gravity based velocity

Landcover• Estimate adherence to land surface• Define friction for overland flow velocity

SPH Example 1: Particle Transport

Release Scenario:• 1,500 bbl released• Released over 1.5 hours• Simulation shows the first 1.5 hours after the

release

Results:• Flow path is narrow in steeper terrain• Spreading in flatter terrain or in depressions


SPH Example 1: Time-Varying Grid Output

• Particles are summarized on a grid by model timestep

• Helps to assess fate of oil: Mass evaporated Thickness Volume


SPH Example 1: End of Simulation Grid Output


• Grid summarized at the end of the model simulation

• Mass of oil evaporated at the end of the simulation

SPH Example 2: Complex Terrain

Release Scenario:• 2,000 bbl released• Released over 2 hours• 6 hour simulation

Results:• Two main flow paths• Lateral spreading


Advanced Weathering


Each line is adifferent chemical

Each chemical hasdifferent properties

Oil is a combination of 10’s-100’s of thousands of chemical compounds (e.g.

hydrocarbons)

Each oil has adifferent composition

ASA Offices

Example Composition of a Light Crude Oil

LowMW

“Light”

HighMW

“Heavy”

Low % High %

Simplify each oil by grouping like-compounds (pseudo-component approach):

Advanced Weathering• For each “particle” of the SPH Model: Composition tracked by 4 pseudo-component groups Each group weathers independently

• Weathering also factors in: Surface area exposed to the air Wind speed Air temperature

• Additional weathering processes: Changes in density Changes in viscosity


Source: lcengineering.com

SPH Example 3: Comparing Oil Products

Release Scenario:• 2,000 bbl released• Released over 2 hours• 6 hour simulation

Results:• Lighter oil travels

further and moves faster


Heavy Crude Light Crude

InfiltrationDetermine:

• Maximum infiltration depth• Infiltration rate

Can be used to assess:• Loss of oil form the land surface• Potential impacts to ground water• Potential clean-up costs

Fast prediction• Conservative approach – does not

include horizontal migration• Short-term period after a release


Source: Shahar Ischarov/Israeli Environmental Protection Ministry

Infiltration: Maximum DepthDetermines:

• Impact to ground water

Factors:• Volume of oil on the surface• Surface area of the oil pool• Retention Capacity of the soil (𝑅𝑅) Smaller particles → smaller pore size → more liquid

retained in the pores• Viscosity (𝜉𝜉) Higher viscosity = more retention


𝑀𝑀𝑀𝑀𝑀𝑀 𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝑀𝑀𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝐷𝐷𝐷𝐷𝐷𝐷𝐼𝐼𝐷 =𝑉𝑉𝐼𝐼𝐼𝐼𝑉𝑉𝑉𝑉𝐷𝐷 𝐼𝐼𝐼𝐼 𝐼𝐼𝐼𝐼𝐼𝐼 𝐼𝐼𝐼𝐼 𝑃𝑃𝐼𝐼𝐼𝐼𝐼𝐼𝐴𝐴𝐼𝐼𝐷𝐷𝑀𝑀 𝐼𝐼𝐼𝐼 𝑃𝑃𝐼𝐼𝐼𝐼𝐼𝐼 × 𝑅𝑅 × 𝜉𝜉

Source: USDA, Lindsey Benne

Infiltration: RateDetermines:

• Time to maximum depth or ground water impact

Factors:• Relative permeability (𝑘𝑘𝑟𝑟−𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁) Based on assumed level of water saturation

• Hydraulic conductivity (𝐾𝐾)• Water viscosity (𝜈𝜈𝑤𝑤) vs. Oil viscosity (𝜈𝜈𝑜𝑜𝑜𝑜𝑜𝑜)• Soil porosity (𝜃𝜃𝑠𝑠)• Retention Capacity of the soil (𝑅𝑅)


𝑃𝑃𝐷𝐷𝐼𝐼𝐷𝐷𝐼𝐼𝐼𝐼𝑀𝑀𝐼𝐼𝐼𝐼𝐼𝐼𝐼𝐼 𝑉𝑉𝐷𝐷𝐼𝐼𝐼𝐼𝑉𝑉𝐼𝐼𝐼𝐼𝑉𝑉 =𝑘𝑘𝑟𝑟−𝑁𝑁𝑁𝑁𝑁𝑁𝑁𝑁 𝐾𝐾𝜃𝜃𝑠𝑠 − 𝑅𝑅

𝜈𝜈𝑤𝑤𝜈𝜈𝑜𝑜𝑜𝑜𝑜𝑜

Infiltration: InputsSoil Data – SSURGO


Groundwater data• Depth to water table• Porosity

• Hydraulic Conductivity• Retention• Infiltration barriers

Infiltration: Overland Plume Pooling

• Starts with outputs from an overland plume model

• Identify locations of “pools”

Depression in the land surface that traps larger volumes of oil

Summarize volume of oil in each

Combined surface area of each


Pools

Infiltration: Results


Infiltration: Additional Considerations

• Horizontal migration

• Interaction with water table

• Long-term transport and fate in the subsurface


Jeremy [email protected]


mailto:[email protected]

a novel approach to simulate the complex dynamics of oil ... · contribution from neighboring...

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