Numerical investigation of CO2 sequestration in ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Numerical investigation of CO2 sequestration in geologic media using the massively parallel computer code PFLOTRAN
Paper
Author:Chuan Lu <clu@lanl.gov> (Los Alamos National Lab)
Peter Lichtner <lichtner@lanl.gov> (Los Alamos National Lab)
Presenter:Chuan Lu <clu@lanl.gov> (Los Alamos National Lab)
Date: 2006-06-18     Track: Special Sessions     Session: Geologic Sequestration of Carbon Dioxide
DOI:10.4122/1.1000000444
DOI:10.4122/1.1000000445

CO2 sequestration (capture, separation, and long term storage) in various geologic media (such as depleted oil reservoirs, saline aquifers, oceanic sediments at different depths) is being considered as a possible solution to reduce green house gas emissions. In this study we utilize the PFLOTRAN simulator to investigate geologic sequestration of CO2. PFLOTRAN is a massively parallel 3-D reservoir simulator for modeling subsurface multiphase (CO2, H2O), multicomponent reactive flow and transport based on continuum scale mass and energy conservation equations. The flow equations are sequentially coupled to reactive transport equations describing multi-component chemical reactions within the formation involving aqueous speciation, and precipitation and dissolution of minerals including CO2-bearing phases to describe aqueous and mineral CO2 sequestration. The effect of the injected CO2 on pH, CO2 concentration within the aqueous phase, mineral stability, and other factors can be evaluated with this model. The PETSc parallel scientific toolkit is used to manage parallel data structures and MPI message passing, and its highly efficient Newton-Krylov solver framework is used to solve the nonlinear equations arising from a fully-implicit time stepping scheme based on domain decomposition. This allows simulations with several tens of millions of degrees of freedom to be carried out—ideal for large-scale field applications involving multi-component chemistry. In this work, our main focus is on the investigation of long term storage and possible leakage processes of CO2, and their sensitivity to reservoir and fluid properties, such as permeability and capillary pressure, diffusion coefficients, component solubility, etc. Important issues include mobility of a supercritical CO2 plume in a heterogeneous porous medium, gravity induced instabilities during CO2 plume buoyancy, and mineral reaction induced permeability change and consumption or production of CO2. These investigations will help provide preliminary criteria for site selection and to develop methods for prevention of leakage.