Numerical simulation of CO₂ injection into deep saline aquifers
Date
2011
Authors
González-Nicolás, Ana, author
Cody, Brent, author
Baù, Domenico, author
Colorado State University, publisher
Journal Title
Journal ISSN
Volume Title
Abstract
In the last two centuries, atmospheric concentrations of carbon dioxide (CO2) have increased by about 35% as a result of anthropogenic emissions. To reduce these emissions, geologic Carbon Capture and Sequestration (CCS) has been introduced as an emerging technology. Current estimations report that deep saline formations account for approximately 60% of the total subsurface storage. Carbon geologic storage involves the injection of CO2 in supercritical state into deep confined aquifers and can be modeled based upon the theory of two-phase flow in porous media. Supercritical CO2 is less dense and less viscous than brine, which causes gravity override. The mass conservation equations for the two phases constitute a non-linear system of partial differential equations (PDE). In this work, MFLOW3D, a numerical finite-element model, is used to solve this non-linear system of PDE's and to test the simulation of CO2 injection into a hypothetical and ideal confined aquifers. In MFLOW3D, the PDE's are discretized in space using linear three-dimensional finite elements in order to obtain a nonlinear system of ordinary differential equations. The temporal discretization is implemented via a finite difference backward-Euler scheme. The non-linearity is solved by using Newton-like iterative methods. Several scenarios are here simulated in order to analyze the effect of different factors on the accuracy of MFLOW3D results. These factors are: resolution and non regularity of finite element mesh, presence of subsurface heterogeneities, and lateral size of the domain. The reliability of simulations is checked for global accuracy in terms of the mass balance relative error for the injected CO2. The numerical tests offer an important feedback on the capabilities and limitations of the adopted numerical approach.
Description
2011 annual AGU hydrology days was held at Colorado State University on March 21 - March 23, 2011.
Includes bibliographical references.
Includes bibliographical references.