This post was originally published on the Bureau of Economic Geology’s homepage.

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.

    Read UT’s coverage of all award recipients and their projects here:
    news.utexas.edu/2020/02/17/enhancing-sustainable-energy-is-the-aim-of-new-ut-collaborations



  • On Tuesday and Wednesday, January 28th and 29th, 2020, GCCC co-hosted the 5th University of Texas Conference on Carbon Capture and Storage (UTCCS-5) with the Texas Carbon Management Program (TxCMP).


    More than 100 participants attended UTCCS-5, including this dinner talk by Dr. Varun Rai, director of the Energy Institute at the University of Texas at Austin.


    Download the program here.


    More than 100 participants joined the UTCCS-5 to learn about the latest updates from the University of Texas at Austin experts on carbon capture and storage.

    Representatives from CCS groups at Battelle, Baker Hughes, BHP, BP, ExxonMobil, JX Nippon (Petra Nova), Shell, Oxy, Total, Trimeric, USGS, DOE’s National Energy Technology Laboratory, Environmental Defense Fund, Clean Air Task Force, and others attended.

    Participants joined either the carbon capture track organized by the UT Chemical Engineering Department and Dr. Gary Rochelle. Or the geological storage track, organized by GCCC. The storage track focused largely on the geological applications, infrastructure, and stakeholder relations within the CCS process.

    The first day of the storage track was dedicated to presenting project updates on GCCC’s 5-year Big Plan which describes our research group’s aspirations for the forward-looking direction of cutting-edge research, guided by the need to upscale CCS to a commercial level. GoMCarb results were also shared. The day ended with a tour of the carbon capture demonstration plant on the UT Austin’s J.J. Pickle Research Campus (photos below).

    During the second day, presentations continued, working through the various tasks in the Big Plan. Afterward, a couple of hours were devoted to closed session discussions with GCCC Industrial Associates, answering questions and receiving feedback on what remains ahead in research in order to push CCS towards wide adoption within energy industries.

    The University of Texas Conference on Carbon Capture and Storage takes place every other year in conjunction with the biannual GCCC Industrial Associates meeting. This is the fifth iteration of the conference.

    View a list of the presenters and their talks below.



    Presentations

    Contact research program coordinator, Emily Moskal (emily.moskal@beg.utexas.edu), for access to the presentation slides.

    Day 1, Tuesday, January 28, 2020

    Welcome, Gary Rochelle and Susan Hovorka

    Plenary: Meeting the Dual Challenge, Jane Stricker and Susan Blevins

    Leslie Savage, Texas Regulatory Environment for CCS

    Benjamin Heard, Gulf Coast Sequestration

    Ramon Trevino and Alex Bump, Progress in the Gulf of Mexico

    Tip Meckel, Addressing Subsurface Aspect of Large-Scale CCS

    Susan Hovorka, Cost of Characterization to Prepare for Permitting

    Katherine Romanak, International Engagement

    Rachel Lim, Stakeholder Challenges and Perspectives

    Emily Moskal, Dialogue in the CCUS Ecosystem

    Seyyed Hosseini, GCCC New Projects

    Darshan Sachde, Overview of CO2 Capture, Transport, and Infrastructure in the Gulf of Mexico

    Katherine Romanak, Environmental Field Studies

    Tip Meckel, Status and Plans for Offshore Monitoring

    Ramon Gil-Egui and Vanessa Nunez-Lopez, The Impact of 45Q and Stacked Storage in the CO2-EOR Sustainability

    Vanessa Nunez-Lopez, Fluid Flow Research in Collaboration with Imperial College London

    Sahar Bakhshian, Prediction of CO2 Footprint: A Hybrid Pore-Scale Simulation and Analytical Modeling

    Varun Rai, CCS…It’s Time!


    Day 2, Wednesday, January 29, 2020

    Larry Lake, The Effect of Compressibility and Boundaries on Displacement Stability

    Shayan Tavassoli, CO2 Storage in Gulf Coast Saline Aquifers and Pilot Case Study of Wellbore Leakage Mitigation for CO2 Storage Projects

    Xiaojin Zheng, Zhuang Sun, D. Nicolas Espinoza, Uniaxial Strain Unloading Compressibility of Frio Sand: Implications on Reservoir Pressure Management for CO2 Storage

    Prasanna Krishnamurthy, CO2 Migration and Trapping in Heterogeneous Porous Media

    Seyyed Hosseini, Analytical Models of Plume Migration and Stabilization

    Jiro Tanaka, Tomakomai CCS Demonstration Project: Project Update

    Susan Hovorka, Monitoring Needs: Well Surveillance and Plume Stabilization

    Susan Hovorka Presenting Curt Oldenburg and Lehua Pan’s Work, Mechanistic Modeling of CO2 Leakage into the Water Column from Offshore CO2 Wells or Pipelines

    Susan Hovorka, Discussion with Sponsors