Abstract
Carbon nanoparticles (CNPs) are becoming promising candidates for oil/gas applications due to their biocompatibility and size-dependent optical and electronic properties. Their applications, however, are always associated with the flow of nanoparticles inside a reservoir, i.e., a porous medium, where insufficient studies have been conducted. In this work, we synthesized CNPs with two different size categories in 200 nm carbon balls (CNP-200) and 5 nm carbon dots (CNP-5), via a hydrothermal carbonation process. Comprehensive experiments in packed glass bead columns, as well as mathematical simulations, were conducted to understand the transport and deposition of CNPs under various ionic strength, particle sizes and concentration conditions. Our results show that the retention of CNP-200 is highly sensitive to the salinity and particle concentrations, while both of them are unaffected in the transport of small CNP-5. Supplemented with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the clean bed filtration theory with blocking effect can successfully fit the experimental breakthrough curves of CNP-200. However, the high breakthrough ability for CNP-5 regardless of ionic strength change is in conflict with the energy interactions predicted by traditional DLVO theory.
Highlights
In the case of DI water, the breakthrough curve (BTC) is steep and the peak effluent concentration reaches the maximum value in a very short time, but with increasing ionic strength, the maximum ability to break through is decreased from ~90% for DI water to ~9.5% at 10 mM electrolyte background
This study provides insights into the transportation and deposition behavior of synthesized carbon nanoparticles with different sizes under various concentrations and ionic strength conditions
Salinity has a strong influence on the breakthrough ability of Carbon nanoparticles (CNPs)-200 in a porous medium, which is due to the reduced energy barrier determined by DVLO theory and blocking caused by the formation of large-size aggregation
Summary
The use of nanoparticles (NPs) for enhanced oil recovery (EOR) has received intensive attention since 2008, and much work has been conducted that can be generally categorized as: (i) the development of ‘contrast-agent’ type NPs to improve the detection limitation of seismic and EM techniques for better reservoir characterization [1,2,3]; (ii) the use of NPs as property modifiers, i.e., to alter rock wettability and interfacial tension at the oil/water interface in order to increase oil recovery rates [4,5,6,7]; and (iii) the use of NPs for conformance control such as nanoparticle-stabilized emulsions, and gelation materials to block the easy flow paths [8,9] All these applications require nanoparticles to transport long distances in reservoir rocks with minimal retention. Retention and transport of CNPs in porous media has received considerable attention recently
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