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## Multiphase Field-scale Modeling: Brine Transport

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**Multiphase Field-scale Modeling: Brine Transport**Ann Cook 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 problems1**Brine Treatment Technology**• How does it work? • Mobilization of the NAPL • Increase Gravimetric Forces • Decrease Capillary Trapping Forces**Brine Treatment Technology**• sn-a = NAPL-aqueous interfacial tension • r =effective pore size • rn= NAPL density • ra= aqueous phase density • g = gravitational acceleration • l = characteristic length of NAPL pool in vertical direction**Area of Remediation**Sheet-piles Impermeable Layer (e.g., clay) Plan View Profile View Brine Treatment Technology • How does it work? • Closed system on 5 sides**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**Brine • Initial density stratified domain • Unstable system (small perturbations) • Occur in model and physical system Ground Water**Rayleigh Number**• Dimensionless Number • Ratio**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**DL < 4aL Pe < 2 • DL = local distance between sides of an element measured in the direction parallel to local flow • aL = 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**• Brine slumping model • Fully saturated fresh water system with brine injection • Unsaturated brine injection • Multiple well configurations**Example Problem: Slumping brine interface**High frequency spatial hydraulic conductivity 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 (Kc)**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**Injection Wells Extraction Well**Fingering**Fingering due to viscous instability