Laboratory Analysis of CO2 Storage in Depleted Organic-Rich Source Rocks for Carbon Sequestration
Abstract
Carbon capture and sequestration processes can use the infrastructure of unconventional EOR projects targeting organic-rich source rocks and use the existing fluids separation and injection technologies. Accordingly, source rocks, also called shale, have unique petrophysical properties that facilitate the storage of large amounts of gas, such as methane and carbon dioxide, at high pressure. Several laboratory methods have previously been developed to measure the storability of gases such as methane and carbon dioxide (CO2) in shale. In my thesis, I investigate source rocks for carbon sequestration by applying an existing gas storage method based on Boyle’s law. Six shale samples with an average 5% total organic carbon were considered and total (free + sorbed) gas storability is predicted using key laboratory-measured parameters: pore volume, pore compressibility, Langmuir volume, Langmuir pressure, and sorbed phase density. The Santos and Akkutlu (2013) method considered pore volume changes and used a linear form of the Langmuir model to estimate gas storability in the laboratory. Experiments were conducted at 77°F for a pressure range of 1,500-3,200 psi. Four of the samples showed preference for CO2 storage in the sorbed phase over the compressed free phase indicating that sequestration in source rocks will be dominated by the CO2 adsorption as the trapping mechanism. The maximum amount stored sorbed volume ranged from 520 to 2,040 scf/ton while the maximum compressed free gas stored ranged from 83 to 460 scf/ton respectively. To maintain the earth’s temperature from rising by 2°C by 2050, it has previously been predicted that about 45 giga-tons of CO2 in total must be sequestered by 2050 considering yearly emission reductions are made. Based on my experimental results I find out that carbon sequestration in North American source rocks should suffice to reach to this target. Barnett shale alone, including in my calculation the total (both developed and not-yet developed) acreage, has the capacity to store 435 giga-tons of CO2. The Marcellus shale, on the other hand, is a large storage unit with a carbon sequestration capacity of 1000 gigatons, i.e., 1 tera-ton. I conclude that the source rocks as volumetric storage units have a significant capacity for the carbon sequestration. This is mainly due to the potential of the organic material in source rock to store carbon dioxide in sorbed states.
Citation
Xavier Vieira, Jessica (2022). Laboratory Analysis of CO2 Storage in Depleted Organic-Rich Source Rocks for Carbon Sequestration. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197295.