Multiphase Field-scale Modeling: Brine Transport Ann Cook Per Per Hatlevik Jonathan Levine Brice Loose Keegan Roberts Amber Sallerson Katy Schulte Martina Vlckova Thomas Willingham

Introduction to DNAPLs Types Sources Behavior PCE, TCE, DCE, VC, CT, CF, DCM, TCA

Introduction to DNAPLs Long lived Difficult to remove Health Hazards –Liver problems –Increased risk of cancer –Nervous system, or circulatory problems 1 Density of Water (r w ) Density of DNAPL (r n ) ~1 g/mL~ g/mL

Brine Treatment Technology How does it work? –Mobilization of the NAPL Increase Gravimetric Forces Decrease Capillary Trapping Forces

Brine Treatment Technology s n-a = NAPL-aqueous interfacial tension r = effective pore size r n = NAPL density r a =aqueous phase density g =gravitational acceleration l =characteristic length of NAPL pool in vertical direction

Brine Treatment Technology How does it work? –Closed system on 5 sides Area of RemediationSheet-piles Plan View Impermeable Layer (e.g., clay) Profile View

Brine Treatment Technology How does it work? No Flow Boundary No Flow Boundary

Brine Treatment Technology How does it work? Pump in Brine Layer

Brine Treatment Technology How does it work? Lower Water Table

Brine Treatment Technology Gravimetric Forces Removal of DNAPL

Brine Treatment Technology How does it work?

Brine Treatment Technology How does it work? Removal of DNAPL

Brine Treatment Technology How does it work?

Brine Treatment Technology How does it work? Remove Brine <1% Original DNAPL Mass

Brine Treatment Technology How does it work? <1% Original = Meet DNAPL Mass Standards

Brine Treatment Technology Why is it novel? –$$ Cheaper $$ –Higher rates of removal than current technologies Pump and Treat Natural Attenuation

Possible Instabilities in the System Physical –Density (changes and/or differences) –Excessive Surfactant Concentration  bypass –Pore Clogging Model –Fingering –Gravity - Rayleigh

Rayleigh-Taylor Instability Initial density stratified domain Unstable system (small perturbations) Occur in model and physical system Brine Ground Water

Rayleigh Number Dimensionless Number Ratio

Modified Rayleigh Number

SUTRA Code written by USGS Simulates single phase fluid flow and transport in the subsurface Uses a combination of finite-element and finite difference methods to solve a series of equations

Conservation Equations Species Balance Equation Species-Summed Flow Equation

SUTRA Transport Math Magic

SUTRA Fluid Flow Species Summed Flow Equation Darcy’s Law Math Magic

Requirements for SUTRA D L < 4a L Pe < 2 D L = local distance between sides of an element measured in the direction parallel to local flow a L = longitudinal dispersivity

SUTRA Goal To model a freshwater system where we inject brine –3D model –Relatively small in the y-direction Visualize system instabilities Removal of brine from system

Simulations Ran 1.Brine slumping model 2.Fully saturated fresh water system with brine injection 3.Unsaturated brine injection 4.Multiple well configurations

Example Problem: Slumping brine interface which admits an analytic solution in the case that the vertical scale is much less that the horizontal (H << R), and a constant hydraulic conductivity (K c ) High frequency spatial hydraulic conductivity

Homogenization permits approximation of K(x,z,t) as a constant that captures the variability Homogenized equations compare well with the accepted numerical solution. High frequency variations are absent.

Evaluate Instabilities Extraction Well Injection Wells

Fingering Fingering due to viscous instability

SUTRA MODELING BCs

SUTRA MODELING Initial Injection

SUTRA MODELING Brine Injection

Transport and Flow Equations AKA “The Magic”