In surfactant flooding for enhanced oil recovery, adsorption of surfactants on the porous media of an oil reservoir is a major concern. It weakens the efficacy of the injected surfactant in reducing oil–water interfacial tension (IFT) and makes the oil recovery process uneconomical. Colloidal silica nanoparticles were found to adsorb at a lower rate than surfactant in porous media because of their charge density and high surface area. Silica nanoparticle surfaces with a negative surface charge are expected to adsorb onto the same active sites in the reservoir as anionic surfactant molecules used in enhanced oil recovery (EOR) applications. Experiments conducted in sandpack demonstrated that pre-treatment of the sandpack with silica nanoparticles at 80°C reduced surfactant adsorption by a factor of three when using artificial seawater as the injection fluid.
We discovered a novel
nanoparticle (NP)–crude oil interaction
and propose a mechanism of NP-based enhanced oil recovery. This NP–crude
oil interaction and its effects on oil recovery are systematically
investigated by conducting microfluidic experiments in both single-pore
scale and “reservoir-on-a-chip” scale. It is confirmed
that hydrophilic silica NPs in an aqueous phase could lead to dramatic
swelling, dewetting, and disjoining of crude oil. The swelling ratio
increased with decreased aqueous phase salinity and with increased
concentrations of negative charging of NPs. Natural polar components
in crude oil is shown to play a very important role. From a pore-scale
perspective, this oil swelling and dewetting increased the flow resistance
in the swept region and redirected flooding liquid toward the unswept
region. From a reservoir perspective, the mobility ratio was reduced
because oil swelling and dewetting modified the relative permeabilities.
This improvement in sweep efficiency resulted in approximately 11%
incremental oil recovery in a completely homogeneous porous micromodel,
with 2000 ppm of NPs suspended in seawater.
Tracer technology is a very efficient diagnostic tool for the oil and gas industry to obtain valuable information about reservoirs. The interpretation of tracers that have traversed the reservoir reveals reservoir characteristics such as inter-well connections, heterogeneities, and water movements that can be used to improve hydrocarbon recovery efforts. Commonly used tracers are radioactive elements and stable isotopes, chemicals, such as fluorescent dyes, and inorganic ions. Novel carbon quantum dots (CQDs)-based fluorescent tracers have been proposed for production and well monitoring. One-step electrochemical synthesis of CQDs from low molecular weight chemical precursors through electrochemical carbonization was developed. The doping of CQDs with heteroatoms such as nitrogen provides differentiated fluorescence emission signatures that can be used to monitor multiple stages of frac operations.
The search for engineering approaches to improve the scintillation properties of Gd3Al2Ga3O12 crystals and enable their production technology is of current interest. This crystal, while doped with Ce, is considered a good multi‐purpose scintillation material for detecting gamma‐quanta and neutrons. It is observed that co‐doping with Mg affected intrinsic defects in the crystal structure that create shallow electronic traps. Other point structure defects, which are based on local variations of the crystal stoichiometry, are significantly diminished by use of a co‐precipitated raw material. Nano‐structuring of the raw material enables production of a homogeneous precursor mixture for growing a crystal with minimal evaporation of Ga from the melt. The demonstrated nano‐engineering approach increased the light yield from the crystal by approximately 20%, enabling its applications in well logging.
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