Impact/Purpose:

Determine the conditions under which dissolved CO₂ brines can impact drinking water aquifers and design effective risk reduction strategies.  Develop a fundamental understanding of the fate of dissolved and exsolving CO₂ at scales ranging from the pore scale to the regional field scale.

Description:

Geologic disposal of supercritical carbon dioxide in saline aquifers and depleted oil and gas fields will cause large volumes of brine to become saturated with dissolved CO₂ at concentrations of 50 g/l or more.  As CO₂ dissolves in brine, the brine density increases slightly. This property favors the long-term storage security of the CO₂ because the denser brine is less likely to move upwards towards shallower depths.  In fact, one proposed strategy for reducing risk from CO₂ injection activities involves pre-dissolving the CO₂ into brine at the surface, and injecting this brine into the disposal formation.  While dissolved phase CO₂ poses less of a threat to the security of shallower drinking water supplies, the risk is not zero.  There are plausible mechanisms by which the CO₂ laden brine could be transported to a shallower depth, where the CO₂ would come out of solution (exsolve), forming a mobile CO₂ gas phase.  This significant mechanism for drinking water contamination has received little attention, and there are basic science and reservoir engineering questions that need to be addressed in order to reduce risks to underground drinking water supplies.

URLs/Downloads:

2011 Progress Report

2010 Progress Report

2012 Progress Report

Record Details:

Record Type:PROJECT( ABSTRACT )

Start Date:11/01/2009

Completion Date:10/31/2012

Record ID: 251888

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Related Organizations:

Role :OWNER

Organization Name :CLEMSON UNIVERSITY

Mailing Address :201 Sikes Hall

Citation :Clemson

State :SC

Zip Code :29634



Role :OWNER

Organization Name :STANFORD UNIVERSITY

Citation :Stanford

State :CA

Zip Code :94305

Project Information:

Approach :

Six main activities will be undertaken.  1) Laboratory core experiments will flood cores with CO₂ saturated brines at reservoir pressure and temperature.  These cores will then be gradually depressurized, and imaged using a medical CT scanner to study the CO₂ phase evolution and movement.  2) Pore-scale multiphysics and fine-grid multiphase continuum modeling of these experiments will be used to develop a fundamental understanding of the exsolution and CO₂ bubble coalescence phenomena as the CO₂ starts to form a mobile phase.  3) Core-scale multiphase continuum modeling will upscale the experimental results with a focus on identifying effective relative permeability functions for use in field scale modeling.  4)  Simulations of regional scale behavior using a variable density groundwater flow model will be performed.  Several active or potential CO₂ storage locations will be simulated during this activity. At least one of these sites will be selected from current supercritical CO₂ injection field projects, and at least one will be representative of sites where dissolved CO₂ brine injection may be proposed.  The simulations will evaluate the effects of upward hydraulic gradients, upward pressure driven brine flow (for CO₂ brine injection projects) and most importantly, the effects of groundwater pumping from shallower aquifers.  5) Local field scale (hundreds to thousands of meters) multiphase simulations of the likely failure modes indentified in the regional scale modeling will be performed for each site, using the same hydrogeologic conditions.  The regional models will form the boundary conditions for these smaller multiphase models, and the modeling will build on the previous core experiments and modeling.  6) These models will then be used to study remediation strategies and alternative storage methods for each scenario.

Cost :$891,342.00

Research Component :Targeted Research

Project IDs:

ID Code :R834383

Project type :EPA Grant