Role of Sodium Dodecyl Sulfate Surfactant at the Interface of the Decane + Brine System in the Presence of CO2, CH4, and Their Mixture/nNilesh Choudhary1,2, Arun Kumar Narayanan Nair2, Shuyu Sun2/n1. Indian Institute of Technology Tirupati, Tirupati, India, and 2. King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia/nIntroduction /nThe emission of anthropogenic CO2 is one of the major causes of global climatic changes. Carbon capture and storage technology might be beneficial for mitigating these emissions. Various adsorbents (e.g., carbon nanotubes and clays) have been extensively utilized for carbon dioxide capture. In enhanced oil recovery (EOR) operations, the oil recovery could also be combined with carbon dioxide storage. The water-alternating-gas (WAG) approach has been utilized for mobility control during CO2 -EOR operations. The WAG cycles consist of injecting water (or surfactant) and CO2 alternatively into the reservoirs. Lowering the interfacial tension (IFT) of the oil + water system leads to an increase in the capillary number which may help to recover more oil. In general, the presence of surfactant/CO2 decreased this IFT. In addition, the captured CO2 contains impurities (e.g., CH4) that may have an important influence on the EOR operations./nSimulation Method/nMD simulations of Decane + water + surfactant and Decane + brine + surfactant two-phase systems in the presence of CH4 and CO2 at 323 and 443 K, and pressure up to 100 MPa were carried out using the GROMACS package. The salt (NaCl) concentration is 2.7 mol/kg and the amounts of surfactant adsorbed at the interface are 0.008 and 0.016 SDS/Å2. Each system was equilibrated for 5 ns in the NPT ensemble (only Lz varied) and we ran a 5 ns production under NVE conditions./nConclusions/n•The addition of CH4, CO2, and the presence of SDS surfactant at the interface reduced the IFTs of the Decane + water and Decane + brine (NaCl) systems./n•The effect of CO2 is more because the interface was highly enriched with CO2 molecules than with CH4 molecules./n•The interfacial thickness between water and Decane/CH4/CO2 molecules increases with increasing surfactant concentration and decreases with salt./nReferences/n1.Choudhary, N., Nair, A. K. N., & Sun, S. (2021). Interfacial Behavior of the Decane + Brine + Surfactant System in the Presence of Carbon Dioxide, Methane, and Their Mixture. Soft Matter (accepted) https://doi.org/10.1039/D1SM01267C/n2.Choudhary, N., Nair, A. K. N., Ruslan, M. F. A. C., & Sun, S. (2019). Bulk and interfacial properties of Decane in the presence of carbon dioxide, methane, and their mixture. Scientific reports, 9(1), 1-10. https://doi.org/10.1038/s41598-019-56378-y/n3.Choudhary, N., Ruslan, M. F. A. C., Nair, A. K. N., & Sun, S. (2021). Bulk and interfacial properties of alkanes in the presence of carbon dioxide, methane, and their mixture. Ind. Eng. Chem. Res., 60(1), 729-738. https://doi.org/10.1021/acs.iecr.0c04843/n4.Choudhary, N., Ruslan, M. F. A. C., Nair, A. K. N., Qiao, R., & Sun, S. (2021). Bulk and Interfacial Properties of the Decane+ Brine System in the Presence of Carbon Dioxide, Methane, and Their Mixture. Ind. Eng. Chem. Res., 60(30), 11525-11534. https://doi.org/10.1021/acs.iecr.1c01607/nAcknowledgment/nWe thank the support of this work by the KAUST under Award No. OSR-2019-CRG8-4074 and HPC:-SHAHEEN/IBEX/n

Assessment of CO2 Geological Storage near Riyadh, Saudi Arabia/nThe Kingdom of Saudi Arabia (KSA) signed the Paris Agreement on climate change and committed to reducing its greenhouse gas emissions. KSA has also launched the Circular Carbon Economy (CCE), a comprehensive framework to address the dual challenge of energy and the environment. Current CO2 emissions from KSA are 600 mty (million tons per year), from which 415mty are from stationary industrial sources. CO2 capture and storage (CCS) offers a safe and effective means to reduce CO2 emissions, at scale, without compromising the role of hydrocarbons in fueling the local and global economies. To determine the storage potential near to the Riyadh area we built a geological model focused on the Unayzah formation using published data. Also, we performed compositional simulations to evaluate the capacity of the reservoir, the fluid flow in the highly-heterogenous reservoir, the contribution of the trapping mechanicians, and the leakage potential of the Khuff formation. Preliminary results showed the potential to store 300 mt of CO2 at a rate of 6 mty. The total storage capacity is, however, much larger and its assessment is ongoing.

ELASTIC RESPONSE OF POROUS ROCKS TO ACCUMULATED SLIP ON COMPLEX FAULT NETWORK/nBy coupling triangular dislocation theory and linearized poro-elastic equations we achieved to quantify the change in porosity with respect to accumulated slip on faults. Our numerical experiments show that the rock types (initial porosity and permeability) control the overall rate of change in the permeability. Young’s and Shear Modulus of rock-types controls the amount of porous medium deformation. Roughness amplifies and scatters the deformed space along the fault direction in porous medium. We scaled up the benchmark results to faults in the reservoir with different lengths, orientations and locations. The results show that accumulated slip can change the porous medium permeability significantly, creating anisotropy based on combination of shear sense and fault network. We suggest geoscientists to use the provided workflow and the code to improve the permeability distribution model in fractured porous medium./n