Browsing by Author "Firoozabadi, Abbas"

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    CO2 Trapping in Layered Porous Media by Effective Viscosification
    (Wiley, 2024) Ding, Boxin; Kantzas, Apostolos; Firoozabadi, Abbas
    Safe and efficient storage of CO2 in saline aquifers requires mobility control to prevent CO2 from accumulation and rapid spreading at the formation top below the caprock. In the past, we have demonstrated the effectiveness of two engineered olefinic-based oligomers for viscosification of sc-CO2 and the significant improvements in residual trapping of sc-CO2 in brine-saturated homogeneous sandstone cores (Ding et al., 2024, https://doi.org/10.2118/214842-pa). The objective of this work is to examine the sweep efficiency and residual brine saturation in the layered cores by effective viscosification with two engineered molecules, providing the implications for CO2 trapping in layered porous media by effective viscosification. In neat CO2 injection, the CO2 channels through the high permeability layer, causing rapid breakthrough and high residual brine saturation. This results in an inefficient process for CO2 storage in saline aquifers. In viscosified CO2 injection, we observe significant improvements in crossflow at the interface between the two-permeability layer, partly due to the mobility control and residual brine saturation reduction. In comparison to the neat CO2 injection, the synergistic effect of the mobility control and increases in interfacial elasticity by injection of vis-CO2 results in delay in breakthrough by a factor of 2 and about 95% higher brine production. Compared to our previous work on displacement experiments in homogeneous sandstone core, there is a more significant reduction of residual brine saturation in layered cores by viscosified CO2 injection. Increases in injection rate is also demonstrated to improve the CO2 storage in layered cores. Both the CO2 viscosification and increases in injection rate may promote the injection pressure to overcome the capillary entry pressure, leading to CO2 displacement of brine in the low-permeability layer. CT-imaging data advances understanding of boundary conditions, brine production, and local residual brine saturation in layered cores.
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    Effective viscosification of supercritical carbon dioxide by oligomers of 1-decene
    (Cell Press, 2022) Kar, Taniya; Firoozabadi, Abbas
    Viscosification of carbon dioxide by polymers can make large scale CO2 sequestration safe and efficient. We present solubility of branched hydrocarbon oligomers in CO2 and viscosification measurements at relevant subsurface conditions. Polymers of 1-decene (P1D) with about 20 repeating units are found to be effective in CO2 viscosification, increasing it by 6.5-fold at 1.8 wt% concentration at 308 K and 31 MPa. We reason that methyl groups and branching promote solubility and viscosification. Low molecular weight oligomers can have lower solubility in CO2 than higher molecular weight ones and the trend in solubility is non-monotonic at constant pressure and temperature. Analysis of solubility trend of P1D oligomers in CO2 advances our understanding of molecular structure and functionality and opens the path to engineering of oligomers effective in viscosification and widespread use of CO2.
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    One-Dimensional Gravity Sedimentation of Proppant
    (2021-12-03) Li, Yali; Hirasaki, George J.; Firoozabadi, Abbas
    To better understand the two-dimensional proppant transport problem in vertical fracture, we use the Method of Characteristics (MOC) to simulate one-dimensional sedimentation of suspensions by gravity. Literature survey and background about proppant transport are introduced first. The theory of sedimentation and MOC is then illustrated. The empirical Richardson & Zaki’s equation, modified with the discontinuous flux approximation, models the hindered sedimentation of uniform particles in a fluid. The characteristic velocity of concentration change is then calculated and the distance-time diagram is plotted for suspension sedimentation problems. Results are compared with existing experimental data to find the best-fit parameters of empirical exponent, n and maximum volume fraction, cm. The algorithm developed here provides a means for validating three-dimensional proppant transport simulators with literature results on 1-D gravity sedimentation of uniform, spherical particles in a Newtonian fluid under non-Brownian conditions.