Abstract Nanoparticles have potential for multiple applications in the oil and gas industry, ranging from EOR operations to improved drilling fluids and cements, as well as reservoir monitoring and characterization. The two biggest challenges to overcome for nanoparticles in the reservoir are stability at reservoir conditions and retention. Understanding the mechanisms controlling transport and retention in porous media is essential to develop nanoparticles able to successfully traverse the reservoir. A commonly used strategy to stabilize nanoparticles and reduce retention is to functionalize their surface or to coat them with polymers. Although the coatings help stabilize the nanoparticles, retention is still a major challenge preventing field wide applications. Previous studies have shown that increasing the pH of injected water reduces the amount of surfactants (chemically similar to polysaccharides) adsorbed to the rock. This paper presents the results of a study that investigates the possibility of improving the transport properties of a polysaccharide coating (dextran) through a carbonate matrix by altering the pH using an alkaline passivation agent (sodium metaborate). The amount of retention was quantified by fluorescently tagging the dextran and measuring the intensity of fluorescence of the effluents using a portable spectrometer. The intensity of fluorescence of the effluents should be proportional to the amount of dextran being recovered. The results show that the alkali passivation agent reduces retention of the coating by ~16%.

Abstract Proximity Sensing is a recently introduced approach to reservoir characterization, which uses high frequency, pulsed electromagnetic (EM) signals that are propagated through naturally occurring transmission lines adjacent to oil reservoirs, such as continuous anhydrite layers that serve as the seal for major carbonate reservoirs in and around the GCC. While propagating through the anhydrite channel the pulse is modulated by the saturation properties of the adjacent reservoirs. Previous 2-D simulations demonstrated the feasibility of using the anhydrite as a low loss transmission line and showed the potential to detect changes in reservoir saturation adjacent to the propagation channel. This work presents further verification of the Proximity Sensing method with 3-D simulations including antenna modelling and polarization effects, dependence of EM modulation with reservoir saturation changes and injection water flood front mapping capabilities. A series of models were created to study the effect of the conductivity and permittivity of the reservoir and the polarization of the EM pulse. The effect of varying each of the EM properties of the reservoir on the speed of propagation of the pulse and the polarization of the antenna is presented. The data shows that in general, large contrasts in conductivity and/or permittivity between the anhydrite channel and the adjacent reservoirs will confine the signal within the anhydrite and will result in shorter travel times than in the absence of strong contrasts. For the purpose of detecting oil and saline water this means that if the reservoir adjacent to the anhydrite is saturated with water the EM pulse will travel faster and the signal will have greater amplitude. In contrast, if the adjacent reservoir is oil saturated and EM signal will slow down and will display lower amplitude. This work aims to identify the most important variables needed to take this approach to small scale field testing. The success of Proximity Sensing would provide an accurate and inexpensive method to characterize reservoir saturation and flood front progression either as part of a logging operation or as a standalone sensing platform.

Abstract The ability to accurately map injected seawater in waterflood operations is an essential goal of reservoir monitoring. This capability improves reservoir management practices by helping to delineate the oil-water interface in new wells, locate bypassed oil pockets, minimizing water fingering and proactively enabling identification of early water breakthrough events. Our approach involves loading the injected water with magnetic nanoparticles, called Magnetic NanoMappers (MNMs) to function as electromagnetic (EM) contrast agents. Detection is accomplished by EM means, similar to cross-well and borehole-to-surface EM imaging, but at higher frequencies. The strategy for developing this technology focuses on forward modeling and travel-time tomographic inversion software. We have previously shown in the laboratory — using a reservoir model — that MNMs slow the group velocity of transiting EM signals [1]. Our results demonstrated the capability of imaging targets filled with different fluids, with high resolution using EM means, which supports the idea of high resolution saturation mapping using MNMs. This paper proposes a novel method to address the challenge of long range EM propagation in the reservoir, in the presence of conductive media. The proposed method relies on the use of natural planar transmission lines present in the carbonate reservoirs of the GCC area. An EM pulse traveling through a relatively non-conductive layer between two more conductive layers, will propagate with relatively low attenuation, and the pulse's travel time will depend upon the electromagnetic properties of the layers above and below. MNMs will provide velocity contrast for EM pulses traveling through regions of the reservoir saturated with MNMs-loaded injection water. Similarly, changes in oil and water saturation will result in changes in travel time. By performing full waveform inversion one would be able to produce a saturation map with higher resolution than conventional cross-well EM methods. This paper details a series of Finite Element Method (FEM) simulations to investigate the feasibility of the proposed method. The results show that long range EM propagation can be achieved through non-conductive layers, acting as planar transmission lines. In addition, the results show that the pulses are modulated by the EM properties of the layers above and below the transmission line. These results open up a new possibility for long range high resolution saturation mapping using EM means.

Abstract The ability to map injected fluids in hydrocarbon reservoirs with high resolution is a key goal for reservoir engineering and optimization. Saudi Aramco is developing tools and methodologies to map floodfront, locate bypassed oil, monitor the oil-water contact and detect super-k zones and fracture corridors prior to early water breakthrough at producing wells. Magnetic NanoMappers (MNM) is a new approach exploiting the use of Magnetic Nano-Particles (MNP) as contrast agents for mapping the floodfront inside the hydrocarbon reservoir. This approach takes advantage of the fact that electromagnetic (EM) waves speed slow down when they pass through magnetic media. Localizing MNP within injected fluids could provide a detailed map of fluids movements. Lab tests have recently demonstrated that the capability of MNM to locate MNP volumes hidden within a 2,000 liter tank (reservoir model) with high resolution. This paper will outline the MNM concept, laboratory testbed, results and future plans.

Attempts at depositing uniform films of nanoparticles by drop-drying have been frustrated by the "coffee-stain" effect due to convective macroscopic flow into the contact line. Here, we show that uniform deposition of nanoparticles in aqueous suspensions can be attained easily by drying the droplet in an ethanol vapor atmosphere. This technique allows the particle-laden water droplets to spread on a variety of surfaces such as glass, silicon, mica, PDMS, and even Teflon. Visualization of droplet shape and internal flow shows initial droplet spreading and strong recirculating flow during spreading and shrinkage. The initial spreading is due to a diminishing contact angle from the absorption of ethanol from the vapor at the contact line. During the drying phase, the vapor is saturated in ethanol, leading to preferential evaporation of water at the contact line. This generates a surface tension gradient that drives a strong recirculating flow and homogenizes the nanoparticle concentration. We show that this method can be used for depositing catalyst nanoparticles for the growth of single-walled carbon nanotubes as well as to manufacture plasmonic films of well-spaced, unaggregated gold nanoparticles.

A process using a modified dielectrophoresis device separates single-walled carbon nanotubes (SWNTs) according to their polarizability in electric fields. This depends on the size and dielectric constant of individual nanotubes and easily separates metallic from semiconducting nanotubes. Separation by length has also been demonstrated. Partial separation (enrichment) according to bandgap (which is linked to polarizability) has also been shown and can be improved to full separation of individual types of semiconducting SWNTs with better control over operational parameters and the length of SWNT starting material. This process and device can be scaled affordably to generate useful amounts of semiconducting SWNTs for electronic device development and production. In this study, a flow injection dielectrophoresis technique was used with a modified dielectrophoresis device. The length, width, and height of the modified chamber were 28, 2.5, and 0.025 cm, respectively. On the bottom of the chamber, there are two arrays of 50-m-wide, 2-m-thick gold electrodes, which are connected to an AC voltage generator and are alternately arranged so that every electrode is adjacent to two electrodes of the opposite polar. There is an additional plate electrode on the top of the chamber that is negatively biased. During the experiment, a syringe pump constantly pumps in the mobile phase, 1-percent sodium dodecylbenzene sulfonate (SDBS) solution, into the chamber. The frequency and voltage are set to 1 MHz and 10 V peak-to-peak, respectively. About 150 micro-L of SWNTs in 1- percent SDBS decanted solution are injected to the mobile phase through a septum near the entrance of the chamber. The flow rate of the mobile phase is set to 0.02 cu cm/min. The injected SWNTs sample flows through the chamber before it is lead into a fluorescence flow-through cell and collected for further analysis. The flow-through cell has three windows, thus allowing the fluorometer to collect fluorescence spectrum and visible absorption spectrums simultaneously. Dielectrophoresis field-flow fractionation (DEP-FFF) generally depends on interaction of a sedimentation force and DEP force for particle separation, and SWNTs are neutrally buoyant in water. In this innovation, the third electrode was added to create a sedimentation force based on DC electrophoresis. This makes this particular device applicable to separations on any neutrally buoyant particles in solution and a more general process for a broad range of nanomaterials sorting and separations.

We demonstrate the fabrication of solid-state dielectric energy storage materials from self-assembled, aligned single-walled carbon nanotube arrays (VA-SWNTs). The arrays are transferred as intact structures to a conductive substrate and the nanotubes are conformally coated with a thin metal-oxide dielectric and a conductive counter-electrode layer using atomic layer deposition. Experimental results yield values in agreement with those obtained through capacitive modeling using Al2O3 dielectric coatings (C>20mF/cm3), and the solid-state dielectric architecture enables the operation of these devices at substantially higher frequencies than conventional electrolyte-based capacitor designs. Furthermore, modeling of supercapacitor architectures utilizing other dielectric layers suggests the ability to achieve energy densities above 10Wh/kg while still exhibiting power densities comparable to conventional solid-state capacitor devices. This device design efficiently converts the high surface area available in the conductive VA-SWNT electrode to space for energy storage while boasting a robust solid-state material framework that is versatile for use in a range of conditions not practical with current energy storage technology.

Spray coating is a scalable and high-throughput process for fabrication of transparent and conducting coatings (TCCs) composed of single-walled carbon nanotubes (SWNTs). Presently the fundamentals of this process are not well understood. We show that suppression of coalescence of spray droplets by sufficiently rapid heat- and mass-transfer yields homogeneous SWNT films by preventing the formation of 'coffee stains' of larger length scale. Such heat and mass transfer is driven by differential evaporation between the top and edges of the drops, whereas thermal and compositional effects on surface tension and buoyancy are weak. Ultrasonic spraying ensures that the droplets are deposited without significant splashing, and delayed splashing at higher Weber number is evidenced. We find that the performance of spray-coated TCCs made from HiPCO SWNTs is limited by bundle diameter rather than length of the constituent SWNTs and bundes. Vapor acid doping with concentrated sulfuric acid roughly doubles the conductivity of the TCCs.