By Joe McNease, Sephora Yameogo, Yuesu Jin, Yingcai Zheng
Department of Earth and Atmospheric Sciences, University of Houston
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Abstract
Geological carbon storage (GCS) involves CO2 capture at sources, transport through high-pressure pipelines, and injection of its supercritical form into geological formations for long-term storage. To make meaningful impact on the global climate, the goal of gigatonne GCS per year is proposed by governments and funding agencies. In this study, we evaluate the concept of the Texas Gulf Coast, stretching from Corpus Christi to Port Arthur, as a carbon capture and storage (CCS) hub and its role in achieving the gigatonne GCS goal. Because there are currently zero operating Class-VI wells and zero active or pending Class-VI well permission applications in the Texas Gulf Coast, we only evaluate the GCS potential and costs in the region. The numbers are just estimates and discussions could be speculative. In this study, we performed pipeline modeling from many stationary CO2 emission sources in the study region to two potential GCS sites in Bayou Bend and Free Port. With annual injection rates of 10 MtCO2 and 30 MtCO2, we let the two storage sites fill up to their individual capacities over 10 years. Our pipeline modeling shows that the optimal pipeline networks favor longer pipelines to large, low-cost capture sources rather than clusters of smaller, high-cost capture sources. The annual costs for the two scenarios including capture, transport, and injection/storage, are $715M and $2.65B, respectively. The capture cost and the injection cost are comparable, but they are much higher (~10x-30x) than the transportation cost. Therefore, any future significant reduction in GCS cost must involve reducing the price of capture or storage or both. There could be considerable seismic hazards. A survey of other CO2 injection sites worldwide shows that induced earthquakes do occur, and the maximum magnitude is about 1.6 at a low injection rate of ~ 1 MtCO2 per year. In the gigatonne-per-year scenario, another phenomenon, called dynamic earthquake triggering, can be important. A triggered or induced earthquake of magnitude ~3 in Texas state waters is of concern as it may rupture the seal of the subsurface storage unit to cause leakage. To achieve gigatonne GCS per year, aggressive actions are needed to increase the number of Class VI wells by 3 orders of magnitude to ~1000 and scale up the GCS system studied here by 33 times, which could result in a total cost of $87B per year. Texas Gulf Coast may have the storage potential, but it has long way to go to become an actual CCS hub given there are virtually no activities yet.
Introduction
The greenhouse effect was shown by Joseph Fourier in 1824. Two main greenhouse gases are methane (CH4) and carbon dioxide (CO2). Methane which reacts with the hydroxyl radical (OH), the main oxidant in the troposphere, has a lifetime of ~ 10 years in the atmosphere. But emitted CO2 can stay in the atmosphere for about 100 years, which means that the cumulative emission matters. From 1750 to 2020, the CO2 concentration in the atmosphere has increased from ~277 ppm to ~412 ppm (by mole). This increasing trend will continue and can lead to many problems. Many countries and states have set or pledged net-zero emission goals. However, achieving these goals is no easy task. The global CO2 emissions from using fossil energy in 2022, were projected to be 36.4GtCO2 (gigatonnes of CO2), rebounding back to the 2019 level (Friedlingstein, Jones, O'Sullivan et al., 2022). To feel the magnitude of this number, if we pool all the petroleum consumed in a year in the U.S., it would be a whopping ~ 1.17 Gt (assuming 20 million bbl/day), but it is still much less than the total CO2 emission per year (~ 5.7 GtCO2 of which ~78% is from hydrocarbons, according to EIA).
To make a meaningful impact in slowing down (unlikely to reduce soon) the increase of atmospheric CO2 concentration by the means of GCS, the injection amount should probably be on the order of one gigatonne per year. Deep saline formations have the largest storage potential compared to other reservoirs such as depleted oil reservoirs and residual oil zones. The gigatonne scale is consistent with the scenarios evaluated in the Princeton Net-zero America study (Greig and Pascale, 2021) as well as the Carbon Negative Shot (announced November 5, 2021; one of the Energy Earthshots Initiatives, see https://www.energy.gov/fecm/carbon-negative-shot, last accessed Feb 16, 2023) which aims to capture gigatonnes of CO2 from the air per year at a price < $100/tonne and store it in geological storage (GCS), biobased and ocean reservoirs, or turn it into value-added products, by 2050, along with aggressive decarbonization. CCS can include many storage types but it is meant to be GCS in this article.
Before large direct air capture (DAC) is economically feasible, CO2 capture from stationary emission sources is necessary in GCS. In our study, we focus on Texas Gulf Coast because it hosts the largest oil and gas market in the United States, producing significantly more carbon emissions per year than any other state (683 MtCO2 or million tonnes of CO2), almost double the CO2 emissions of the trailing state of California (358 MtCO2, Figure 1) for the year 2019. Could there be an opportunity for direct facility-to-reservoir CO2 pipelines in this region? Here, we explore the Texas Gulf Coasts viability as a hub for CO2 storage by performing CO2 pipeline modeling from sources to sinks and a cost analysis. We then consider potential risks.
Emission datasets and method
The 2021 EPA Greenhouse Gas Reporting Program (GHGRP) data (https://www.epa.gov/system/files/other-files/2022-10/2021_data_summary_spreadsheets.zip, last accessed Feb. 13, 2023) contains 828 stationary carbon emitters for Texas that are responsible for 372.7 MtCO2 for the year 2021. These sources comprise many different types, including electrical (coal/gas), petrochemical manufacturing, petroleum refineries, hydrogen production, and ethylene to name a few. We restrict our analysis to the stationary carbon emitters within the quadrangle spanned by Beaumont, Waco, San Antonio, and Corpus Christi (see Figure 2). More specifically, we analyze the top 23 CO2 emitters (Figure 2a) (>2.5 MtCO2 per year) in this area, which account for 48% or 130.7 MtCO2 per year of the total 271.6 MtCO2 per year (in the quadrangle). We then choose two potential carbon storage reservoirs along the Gulf Coast for analysis, namely the Bayou Bend CCS (Carbon Capture and Storage) and Freeport LNG CCS sites (Figure 2b). These two sites are used for the purpose of this study but by no means are the only available sites. Bayou Bend covers 40,000 acres of land and is expected to be able to accommodate 225-275 MtCO2 while Freeport LNG is 500 acres and is estimated to accommodate 25 MtCO2 (Talos Energy January 2023 Investor Presentation, https://s201.q4cdn.com/120347489/files/doc_presentations/2023/01/2023.01.05-Talos-Energy-January-2023-Discussion-Materials-vFINAL.pdf). You can find more information about these sites at Talos Energy’s website (https://www.talosenergy.com/operations/carbon-capture-and-sequestration/default.aspx).