QUANTIFYING THE IMPACTS OF RESERVOIR GEOCHEMISTRY AND PORE STRUCTURE ON THE CO2 DIFFUSION AND LEAKAGE IN ORGANIC-RICH MUDROCK FORMATIONS AND CAPROCKS
Downtown Houston
Speaker:
Seminar Date: Oct 10 2024
Registration Opens: Sep 24 2024 - Oct 10 2024
Time: 12:00 PM - 01:00 PM (US CDT)
Admission/Registration Link: https://register.gotowebinar.com/register/7275559043109113947
Donation Link: None
Meeting/Webinar Link: None
Contact: Artur Posenato Garcia (VP Downtown, SPWLA Houston Chapter)
Corresponding: vpdowntown@spwla-houston.org
Fees: FREE
ABSTRACT:
To ensure the long-term effectiveness and safety of CO2 storage, it is essential to understand and quantify the diffusion of CO2 within the storage reservoirs. Therefore, the objectives of this paper are to (i) investigate the impact of pore size and pore geometry of kerogen structures on the diffusion of CO2, (ii) investigate the impact of water and hydrocarbon saturation on the CO2 diffusivity in organic-rich mudrocks, and (iii) quantify the coupling effect of CO2 adsorption/diffusion in kerogen nanopores on the apparent gas permeability. We used a realistic kerogen molecular model of type IIC. The kerogen model was developed using the restrained simulated annealing process to investigate the impact of different pore geometries (i.e., cylindrical and channel-shaped pores) on the adsorption and diffusion behavior of CO2 molecules. Meanwhile, we modeled a variety of water and methane saturation cases for kerogen structures. Next, we quantified the CO2 diffusion and transport coefficients under different water and methane saturation conditions. Finally, we quantified the surface, matrix, and bulk gas diffusion coefficients across the kerogen structures. Once the actual diffusivity value is determined, we can use it to calibrate the apparent gas permeability models which are used to describe the gas flow in nanopores. Results showed that the pore size and geometry of kerogen structures affect the diffusion regime and magnitude of the injected CO2. We identified three diffusion regimes inside the kerogen nanopores. The bulk diffusion regime lies far away from the kerogen surface, the surface/adsorbed diffusion regime lies along the kerogen surface, and finally, the sorption/matrix diffusion regime is inside the kerogen matrix. For the case of channel-shaped pores, the average bulk, surface, and sorbed diffusion coefficients are 1.3*10-7 m2/s, 4.6*10-8 m2/s, and 9.8E10-9 m2/s, respectively, at 20% methane saturation. These values dropped to 9.5*10-8 m2/s, 4.0*10-8 m2/s, and 1.2*10-8 m2/s for the same corresponding regimes respectively at 20% water saturation. Changing the kerogen pore geometry to a cylindrical shape reduced the CO2 bulk and surface diffusion by 40% and 25% compared to the channel-shaped pores for the same gas saturation. The outcomes of this paper enhance our understanding of the diffusion process, which is crucial for reliable assessment of the amount of CO2 that can be safely and securely stored in subsurface reservoirs. The diffusion of CO2 in organic-rich mudrock formations can also impact the geological sealing properties of the rock. If CO2 can diffuse through the kerogen pores, it may increase the risk of leakage, potentially compromising the integrity of the storage site.
BIOGRAPHY:
Ibrahim Gomaa is a graduate research assistant and Ph.D. candidate at the Hildebrand Department of Petroleum and Geosystems Engineering at The University of Texas at Austin. His major research interest is investigating the influence of rock petrophysical and geochemical properties on CO2 storage and trapping mechanisms in both conventional and unconventional formations. Ibrahim received his B.S. degree in Petroleum Engineering from the British University in Egypt, Cairo, Egypt, and his M.Sc. from King Fahd University of Petroleum & Minerals, Dharan, Saudi Arabia. During his bachelor’s degree, Ibrahim joined Texas A&M University as a research scholar where he worked on surfactant flooding for enhanced oil recovery. During his master’s degree, Ibrahim worked on developing novel solutions for sandstone reservoir stimulations and complex mud cake removal. His master’s thesis topic got the best presentation award at SPE – MENA region.