Title: Computational Environments for Coupling Multiphase Flow, Transport, and Mechanics in Porous Media for Modeling Carbon Sequestration
Author: Mary F. Wheeler, The University of Texas at Austin
After 24 years at Rice University, Professor Mary Fanett Wheeler, a world-renowned expert in massive parallel-processing, arrived at The University of Texas in the Fall of 1995 with a team of 13 interdisciplinary researchers, including two associate professors, three research scientists, three postdoctoral researchers, and four Ph.D. students. Professor Wheeler is not completely new to UT, however, having received a B.S., B.A., and M.S. degrees from here before transferring to Rice for her Ph.D. under the direction of Henry Rachford and Jim Douglas, Jr. Drs. Rachford and Douglas, both of whom conducted some of the first applied mathematics work in modeling engineering problems, have greatly influenced her career.
With the oil industry's strong presence in Houston, she was at the right
place at the right time to advance the leap from theoretical mathematics
to practical engineering. She correctly theorized that parallel
algorithms would spur a technological revolution, offering a multitude
of applications in the fields of bioengineering, pharmaceuticals and
population dynamics. Her reputation as a first class researcher has led
to several national posts, including serving on the Board of
Mathematical Sciences, on the Executive Committee for the NSF's Center
for Research on Parallel Computation and in the National Academy of
Engineering. Housed in the Texas Institute for Computational and Applied
As Head of UT's new Center for Subsurface Modeling (CSM)
Because of the complexity of the problems, Wheeler and her associates
must obtain data about the geology, chemistry, and mechanics of a site
before they can begin to construct algorithms to accurately depict a
simulation. Hence, the interdisciplinary nature of the work, which no
one individual within a single department could tackle on his/her own.
Yet Professor Wheeler has indeed made great strides toward obtaining
expertise in several disciplines key to the success of parallel
computing. Indeed, she holds joint appointments in the Departments of
Petroleum and Geosystems Engineering
Dr. Wheeler's own research interests include numerical solution of partial differential systems with application to the modeling of subsurface and surface flows and parallel computation. Her numerical work includes formulation, analysis and implementation of finite-difference/finite-element discretization schemes for nonlinear coupled pde's as well as domain decomposition iterative solution methods. Her applications include reservoir engineering and contaminant transport in groundwater and bays and estuaries. Current work has emphasized mixed finite-element methods for modeling reactive multi-phase flow and transport in a heterogeneous porous media, with the goal of simulating these systems on parallel computing platforms. Dr. Wheeler has published more than 100 technical papers and edited seven books. She is currently an editor of four technical journals and managing editor of Computational Geosciences. In 1998 she was elected to the National Academy of Engineering.
There is consensus in the scientific community that increased levels of greenhouse gases contribute to recent trends in global warming and dramatic changes in weather patterns. Geologic sequestration by injection of CO2 into deep brine aquifers and reservoirs represents one of the most promising approaches for reducing atmospheric CO2.
The basis for this potential is the huge global storage capacity existing in geologic formations (primarily deep saline aquifers) and the availability and close proximity of potential injection sites to power generation plants. However, such injections pose significant technical issues in efforts to ensure safety, to minimize leakage probability on a time scale of hundreds or even thousands of years, and to gain public acceptance.
A key goal of our work is to produce a prototypical computational system to accurately predict the fate of injected CO2 in conditions governed by multiphase flow, rock mechanics, multi-component transport, thermodynamic phase behavior, chemical reactions within both the fluid and the rock, and the coupling of all these phenomena over multiple time and spatial scales. Even small leakage rates over long periods of time can unravel the positive effects of sequestration. This effort requires high accuracy in the physical models and their corresponding numerical approximations. For example, an error of one percent per year in a simulation may be of little concern when dealing with CO2 oil recovery flooding, but such an inaccuracy for sequestration will lead to significantly misleading results that could fail to produce any long-term predictive capability. It is important to note that very few parallel commercial and/or research software tools exist for simulating complex processes such as coupled multiphase flow with chemical transport and geomechanics.
In order to address this challenge a robust reservoir simulator comprised of coupled programs that together account for multicomponent, multiscale, multiphase flow and transport through porous media and through wells and that incorporate uncertainty and include robust solvers is required. The coupled programs must be able to treat different physical processes occurring simultaneously in different parts of the domain, and for computational accuracy and efficiency, should also accommodate multiple numerical schemes. In addition, this problem solving environment or framework must have parameter estimation and optimal control capabilities. We present a "wish list" for simulator capabilities as well as describe the methodology employed in the IPARS software being developed at The University of Texas at Austin.