Browsing by Author "He, Peng"

Now showing 1 - 5 of 5
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    Characterizing Asphaltene Deposition in the Presence of Chemical Dispersants in Porous Media Micromodels
    (American Chemical Society, 2017) Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C.; Goharzadeh, Afshin; Vargas, Francisco M.; Biswal, Sibani Lisa
    Asphaltenes are components in crude oil known to deposit and interrupt flows in critical regions during oil production, such as the wellbore and transportation pipelines. Chemical dispersants are commonly used to disperse asphaltenes into smaller agglomerates or increase asphaltene stability in solution with the goal of preventing deposition. However, in many cases, these chemical dispersants fail in the field or even worsen the deposition problems in the wellbores. Further understanding of the mechanisms by which dispersants alter asphaltene deposition under dynamic flowing conditions is needed to better understand flow assurance problems. Here, we describe the use of porous media microfluidic devices to evaluate how chemical dispersants change asphaltene deposition. Four commercially used alkylphenol model chemical dispersants are tested with model oils flowing through porous media, and the resulting deposition kinetics are visualized at both the matrix scale and pore scale. Interestingly, initial asphaltene deposition worsens in the presence of the tested dispersants, but the mechanism by which plugging and permeability reduction in the porous media varies. The velocity profiles near the deposit are analyzed to further investigate how shear forces affect asphaltene deposition. The deposition tendency is also related to the intermolecular interactions governing the asphaltene–dispersant systems. Furthermore, the model system is extended to a real case. The use of porous media microfluidic devices offers a unique platform to develop and design effective chemical dispersants for flow assurance problems.
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    Combined interfacial shear rheology and microstructure visualization of asphaltenes at air-water and oil-water interfaces
    (The Society of Rheology, 2018) Lin, Yu-Jiun; Barman, Sourav; He, Peng; Zhang, Zhuqing; Christopher, Gordon F.; Biswal, Sibani Lisa
    Asphaltenes are surface-active polyaromatic molecules in crude oil that are known to deposit in pipelines or stabilize water droplets by flocculating at interfaces resulting highly viscous emulsions, leading to significant flow assurance problems. Commercial dispersants have been developed to disturb asphaltene aggregation to mitigate deposition, but their role on the interfacial properties of asphaltene films is unclear. In this study, we elucidate asphaltene interfacial rheology at air-water and oil-water interfaces at high and low asphaltene surface coverage and in the presence of dispersants. A modified Langmuir trough with double-wall ring rheometer is used to simultaneously visualize the microstructure of asphaltene interface and measure the rheological responses. Two surface coverages, 0.5 and 4 μg cm−2, show widely different rheological responses at air-water interfaces. Strong yielding behavior was observed for higher coverage while a less yielding behavior and wider linear viscoelastic regime were observed for the lower coverage. Additionally, asphaltenes at decane-water interfaces were less shear-thinning than at air-water interfaces. Surface pressure-area compression-expansion curves show that the interface is more compressible in the presence of commercial chemical dispersants. This combined imaging and interfacial rheology platform provide an effective method to correlate asphaltene microstructure to interfacial rheological properties.
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    Destabilization, Propagation, and Generation of Surfactant-Stabilized Foam during Crude Oil Displacement in Heterogeneous Model Porous Media
    (American Chemical Society, 2018) Xiao, Siyang; Zeng, Yongchao; Vavra, Eric D.; He, Peng; Puerto, Maura; Hirasaki, George J.; Biswal, Sibani L.
    Foam flooding in porous media is of increasing interest due to its numerous applications such as enhanced oil recovery, aquifer remediation, and hydraulic fracturing. However, the mechanisms of oil-foam interactions have yet to be fully understood at the pore level. Here, we present three characteristic zones identified in experiments involving the displacement of crude oil from model porous media via surfactant-stabilized foam, and we describe a series of pore-level dynamics in these zones which were not observed in experiments involving paraffin oil. In the displacement front zone, foam coalesces upon initial contact with crude oil, which is known to destabilize the liquid lamellae of the foam. Directly upstream, a transition zone occurs where surface wettability is altered from oil-wet to water-wet. After this transition takes place, a strong foam bank zone exists where foam is generated within the porous media. We visualized each zone using a microfluidic platform, and we discuss the unique physicochemical phenomena that define each zone. In our analysis, we also provide an updated mechanistic understanding of the "smart rheology" of foam which builds upon simple "phase separation" observations in the literature.
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    Dynamics of paramagnetic squares in uniform magnetic fields
    (Elsevier, 2016) Du, Di; He, Peng; Zeng, Yongchao; Biswal, Sibani Lisa
    The magnetic forces between paramagnetic squares cannot be calculated using a classic dipolar model because the magnetic field distribution is not uniform within square particles. Here, we present the calculation of magnetic forces and torques on paramagnetic squares in a uniform 2-D magnetic field using a Laplace's equation solver. With these calculations, we simulate the variations in equilibrium configurations as a function of number of interacting squares. For example, a single square orients with its diagonal directed to the external field while a system of multiple squares will assemble into chain-like structures with their edges directed to the external field. Unlike chains of spherical magnetic particles, that easily stagger themselves to aggregate, chains consisting of magnetic squares are unable to aggregate due to interchain repulsion.
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    Examining Asphaltene Solubility on Deposition in Model Porous Media
    (American Chemical Society, 2016) Lin, Yu-Jiun; He, Peng; Tavakkoli, Mohammad; Mathew, Nevin Thunduvila; Fatt, Yap Yit; Chai, John C.; Goharzadeh, Afshin; Vargas, Francisco M.; Biswal, Sibani Lisa
    Asphaltenes are known to cause severe flow assurance problems in the near-wellbore region of oil reservoirs. Understanding the mechanism of asphaltene deposition in porous media is of great significance for the development of accurate numerical simulators and effective chemical remediation treatments. Here, we present a study of the dynamics of asphaltene deposition in porous media using microfluidic devices. A model oil containing 5 wt % dissolved asphaltenes was mixed with n-heptane, a known asphaltene precipitant, and flowed through a representative porous media microfluidic chip. Asphaltene deposition was recorded and analyzed as a function of solubility, which was directly correlated to particle size and Péclet number. In particular, pore-scale visualization and velocity profiles, as well as three stages of deposition, were identified and examined to determine the important convection–diffusion effects on deposition.