AbstractThe Zero Emissions Research and Technology (ZERT) project at the Los Alamos National Laboratory is studying the injection of CO2 into geologic repositories. We are formulating the problem as science based decision framework that can address issues of risk, cost, and technical requirements at all stages of the sequestration process. The framework is implemented in a system model that is capable of performing stochastic simulations to address uncertainty in different geologic sequestration scenarios, including injection into poorly characterized brine aquifers.

Processes level laboratory experiments, field experiments, modeling, economic data, and risk theory are used to support the system level model that will be the basis for decision making. The current system model, CO2-PENS, is already proving to be useful in showing complex interactions between the different components of the framework. The system model also provides a consistent platform to document decisions made during the site selection, implementation, and closure periods.

CO2-PENS: A CO2 Sequestration Systems Model Supporting Risk-Based DecisionsPhilip H. Stauffer, Hari S. Viswanathan, George D. Guthrie, Rajesh J. Pawar , John P. Kaszuba, James W. Carey, Peter C. Lichtner, Chuan Lu,

Ionnis N. Tsimpanogiannis, Hans J. Ziock, Manvendra K. Dubey, Seth C. Olsen , Steve J. Chipera, Julianna E. Fessenden

2) CO2-PENS System Level Model used to explore complex interactions between Risk, Cost, and

Technical Requirements

3) Process Level Investigations used to Support System Level Calculations

1)A Science-Based Decision Framework for Predicting Engineered Natural Systems

Nordbotten, J, M. Celia, S. Bachu, Water Resources Research, 2004.

Core Flood Experiment Calcite dissolution

Numerical Modeling using LANL Porous Flow Codes FEHM and PFLOTRAN

Output concentration 10 m above an injection site

Analytical Solutions for Wellbore Failure Obtain leakage rates using semi-analytical solutions, collaboration with M. Celia and others at Princeton

Reaction zone

SACROC Core Analysis

Cem

ent

3cm

CO2 Mineralization: Dawsonite Synthesis Experiments

Reservoir Processes >> CO2 Fate and Transport

Cement Degradation >> Wellbore failure

CO2 Cement Brine Experiment

pH sensitive dyeCa(OH)2 (high pH) -> CaCO3 (low pH)

PCO2 = 13.8 MPa

CO2 mass in the reservoir and various leakage pathways

Borehole failure and repair information

FLOTRAN reactive chemistry simulations

Main Simulation Control

Reservoir Variables Input

CO2-PENS

Model Root

The model root is based on the conceptual framework. The system model is designed to adapt to changes in understanding and can be modified quickly to add new processes and interactions. Identification of additional processes and interactions can come through use of the system model, literature searches, and through independent investigations undertaken to support the decision making process.

The model root, created in GoldSim, is used to manage global variables such as time, CO2 mass balance, total risk, well statistics, and costs. GoldSim is also used to sample stochastic distributions and allows robust uncertainty analysis. Subprograms, written in the language of choice (i.e., FORTRAN, C) are called from the model root. These subprograms can be changed to include more detailed calculations as data and theory are revised. Multiple options for subprograms allow flexibility. For example, limited availability of data may obviate the need for a complex subprogram.

Example Output

30 yr in-situ CO2 exposure history retrieved from core near the reservoir/caprock interface. SACROC, Texas Special Thanks for providing the core to:

LAUR 05-6262Unclassified

Significant Clay Growth Occurs

Hobbs Injection SiteField injectionLab experimentsNumerical simulations

CO2-PENS

Conceptual Framework

Multiphase flow; Water -CO2 - Air: Fractured porous media: Reactive chemistry: Thermal effects: Density driven flow: Supercritical CO2 : PFLOTRAN is now massively parallel

Multiple layersReduced complexity relative to FEHM simulations Couple analytical solutions to the CO2-PENS system model

8000 yrs

Mole fraction dissolved CO2

Numerical simulation using FLOTRAN

Visualization of Wormhole formation

Data Analysis byNew Mexico Tech

Image byUC Davis

0.2 m x 0.2 m

(m)(m)

pH

(m)

Risk Analysis