Browsing by Author "Firoozabadi, Abbas"

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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.