In 2009, with the pending Federal legislation to limit greenhouse gas emissions (Waxman-Markey Bill), the Texas Legislature used SB 1387 to advance CCUS in Texas.
One result was a joint report by the Railroad Commission (RRC-oil and gas regulation), Texas Commission on Environmental Quality (TCEQ), General Land Office (GLO), and Bureau of Economic Geology (BEG) entitled: Injection and Geologic Storage Regulation of Anthropogenic Carbon Dioxide. A lot has changed in the decade since, but this report still provides information useful for understanding CCS in Texas and makes 9 recommendations covering various aspects of the topic. A primary goal of this report is to clarify some of the technical and regulatory issues surrounding geologic storage of CO2.
Figure 1. (a and b) Direct pore-scale numerical simulations of two-phase flow in three-dimensional real-rock models using digital rock technology. (c and d, respectively) Invasion pattern of CO₂ injected into a water-wet and non-water-wet rock sample. CO₂ ganglia trapped in the pore space of (e) a water-wet sample and (f) a heterogeneous-wet sample.
When two fluids migrate together though pores in rocks, complex
interactions occur between the fluids and with the rock matrix. These
complexities influence the amount of each fluid that can be injected
into or extracted from the pores, and how far fluids will migrate. Our
team at the Gulf Coast Carbon Center studies the geosystem response to
carbon dioxide (CO₂) injected into the subsurface to avoid emissions
into the atmosphere—carbon storage. A major theme of our research is how
to best design and monitor injection to maximize confidence in the
ability of storage sites to retain CO₂ over periods of hundreds to
thousands of years.
Buoyancy and viscous forces cause CO₂ to migrate away from the
injection location, which increases the risk of its escape from the
injection zone. We study the pore-scale processes that limit CO₂ plume
migration and enhance storage capacity in saline aquifers. Two main
processes effectively limit the plume extent: (1) capillary trapping,
which happens when CO₂ pinches off and becomes immobilized in the pore
space by capillary forces, and (2) dissolution trapping, where CO₂ gets
dissolved and hence trapped in the resident brine.
Traditionally, observations of pore-scale processes have been made
using core samples in the laboratory. However, many factors limit this
traditional approach, such as the cost and long time necessary for each
analysis and the relative unavailability of high-quality cores. The core
samples themselves have heterogeneous textures, which lead to various
pore-scale responses of the fluids. Given these limitations, correct
scaling of small-scale forces is difficult in the laboratory. In
addition, the use of real fluid requires high pressure conditions and
the use of proxy fluids is imprecise.
To resolve these issues, Sahar Bakhshian of the Gulf Coast Carbon
Center spearheaded an innovation that creates pore-scale simulations of
two-phase flow in real-rock models. By leveraging digital rock-scanning
technology such as microtomographic imaging, our team can create a
high-quality pore-scale model of any rock matrix. These high-resolution
rock models allow many different numerical experiments to be run under
controlled conditions. Exploiting parallel computing algorithms and
high-performance computing platforms enables efficient computationally
intensive simulations on high-resolution scanned rock images.
Using machine learning, our scientists aim to upscale these various
pore-scale processes to determine how two-phase flow interacts at a
large scale with bedforms, reservoir architecture, and basin-scale
depositional systems to ensure responsible CO₂ injection and storage.
Furthermore, we are advancing toward validating our numerical models
using fabricated micromodels. With these innovations, we can better
assess how much of the injected CO₂ will be retained near the injection
well and how quickly and widely CO₂ will move underground using targeted
study sites like the Miocene-aged sandstone strata of the subsea Gulf
of Mexico. This information is needed to design commercial injection
projects to reduce atmospheric CO₂ emissions.
Publications
Bakhshian, S., and Hosseini, S. A., 2019, Pore-scale analysis of
supercritical CO₂-brine immiscible displacement under
fractional-wettability conditions: Advances in Water Resources, v. 126,
p. 96–107, doi:10.1016/j.advwatres.2019.02.008.
Bakhshian, S., Hosseini, S. A., and Lake, L. W., 2020, CO₂-brine
relative permeability and capillary pressure of Tuscaloosa sandstone:
effect of anisotropy: Advances in Water Resources, v. 135, no. 103464,
13 p., doi:10.1016/j.advwatres.2019.103464.
Bakhshian, S., Hosseini, S. A., and Shokri, N., 2019, Pore-scale
characteristics of multiphase flow in heterogeneous porous media using
the lattice Boltzmann method: Scientific Reports, v. 9, no. 3377, 13 p.,
doi:10.1038/s41598-019-39741-x.
Treviño, R. H., and Meckel, T. A., eds., 2017, Geological
CO₂ Sequestration Atlas of Miocene Strata, Offshore Texas State Waters:
The University of Texas at Austin, Bureau of Economic Geology Report of
Investigations No. 283, 74 p.
Name of Project: Permanent Storage of CO₂—Contribution of Pore-Scale Modeling
Project PI: Sahar Bakhshian
Other key personnel: Tip Meckel, Susan Hovorka,
Seyyed Hosseini, Ramón Treviño, Vanessa Nuñez-López, Alex Bump, Mike
DeAngelo, Katherine Romanak, Dallas Dunlap, Iulia Olariu, Tucker Hentz,
and students Melianna Ulfah, John Franey, Arnold Aluge, and Harry Hull
The Energy Institute funded a proposal co-written by the Gulf Coast Carbon Center (GCCC) to find out how to implement and assure long-term underground geological storage of carbon dioxide (CO2) at the technical, legal, policy, business, and community level. The University of Texas at Austin (UT) cross-disciplinary project is co-led by Susan Hovorka of the Bureau of Economic Geology’s GCCC and LeeAnn Kahlor of the Moody College of Communication. Other team members are from the Cockrell School of Engineering, the School of Law, and the McCombs School of Business.
The Energy Institute put out the call for proposals titled, Fueling a Sustainable Energy Transition. More than 30 applications were submitted from 127 researchers and GCCC’s project was 1 of 11 projects awarded. The goal is to find solutions to provide affordable and reliable energy in the world’s movement towards sustainable energy.
Carbon storage is long-term
One method to reduce atmospheric emissions of CO2 is carbon capture and
storage (CCS). Fossil fuel combustion with the release of the greenhouse gas CO2
is one part of the problem. In addition, many industrial processes, like
chemical, cement, and steel manufacturing, emit CO2 yet remain
without a viable mitigation option besides CCS. Many sustainable technologies,
such as renewable energy generation, rely on these industrial processes.
To achieve the needed reduction in emissions, geological storage must be effective
in permanently retaining CO2 that’s injected into the subsurface.
How do we provide assurance that the project is effective?
The project collaborators approach this question from a variety of angles, according to their expertise. Under the proposal titled “Assuring Long-term Storage of Captured CO2: Technical-Legal-Policy-Business Models,” the team proposes to study three strands they expect will help provide needed confidence and support large-scale implementation.
While the technologies used in geologic storage are mature and provide high
technical confidence that stored CO2 is trapped in the deep
subsurface over long periods, translating this into certainty that can be used
to underpin a large business investment is a new challenge. Interest in
investment is growing, but the needed confidence remains poor.
Geoscientists use novel techniques to confirm their predictions
Understanding the multitude of ways that CO2 and the underground brine water interact within pore spaces in rocks is needed to predict the long-term consequence of that interaction. Pore-scale fluid interactions that trap CO2 have been modeled at GCCC previously but the new project will build pore-scale micromodels to experimentally validate the predicted interactions. Upscaling this to a level relevant to the total CO2 injected into an underground rock will determine how the fluid movement stalls overtime underground and be critical to gaining confidence in storage permanence. These experiments and computer modeling will be compared to projects at field sites so that scientists will be able to better predict the stabilization of CO2 underground.
Action requires coordination of business, policy, and regulation
If CCS is to move in a direction that tackles significant national or global emissions, then risk will transfer from the public (everyone is affected by greenhouse gases in the atmosphere) to the private, corporate environment (emitters taking action to store their greenhouse gases). Precedent and mechanisms for creating legal and policy frameworks to support long-term storage will be assessed. Translating the geotechnical language to appropriate commercial and regulatory communications will help provide financial assurance and risk avoidance to manage long-term liability for storage.
Everything depends on effective communication
The scientific justification for CCS is to combat the greenhouse gas CO2 from entering the atmosphere where it contributes to climate change. At present, many public stakeholders in areas where CCS is likely to be deployed—such as Texas—are not aware of CCS nor its potential to mitigate climate change. Because large-scale CCS implementation will require public support, it is imperative that the technology’s mitigation potential be recognized by public stakeholders. Therefore, the social scientists in the project will employ survey methods with a probability based sampling strategy to test a variety of messages and phrases in hopes of making the connection between climate change, CO2, and CCS clear and apparent. This work will help improve communication efforts aimed at building awareness of longterm storage.
“We know a fair amount already. For example, public awareness of CCS is low, awareness of the benefits leads to more support,” project co-lead Lee Ann Kahlor said. “But we also know that, at least in Texas, people aren’t aware that CCS is a way to mitigate climate change. So that is our goal – to make that connection clear. On the surface, it sounds really simple. But rest assured, if it was simple we wouldn’t need to be doing this work.”
Transferring confidence to the whole energy ecosystem
By approaching the topic from a variety of angles, UT scientists will help
answer one of the longest standing and complicated issues in CCS: confidence in
long-term geological storage.
The Energy Institute promotes research at UT that makes a global impact on the future of energy.
Other projects awarded include sustainable energy topics such as nextgen battery packs, solar-powered water purification, electricity infrastructure for extreme weather, predicting ecosystem carbon capture, optimizing carbon capture processes, and managing climate change and land-use planning in urban areas, among others.
