We hereby employ molecular dynamics (MD) simulations (∼6 μs in total) to investigate the chain dynamics, aggregation, and interfacial properties of the partially hydrolyzed polyacrylamide (HPAM) polymer. HPAM is widely used in chemical enhanced oil recovery (cEOR) applications. The conformational changes and aggregation properties are examined in different conditions simulating cEOR activities. Also, we examined the degree of polymerization (20-, 50-, and 100 -mers) effect on the polymer chain dynamics and aggregation. MD simulations showed that HPAM has a high conformational diversity ranging from coiled to compact conformations. The former is abundantly found in fresh water. In brine solutions, HPAM is found to be very sensitive to ions and adopts a more compact conformation. HPAM-ion interactions drive the conformational thermodynamic equilibrium between the compact and coiled conformations toward the compact conformation. Furthermore, ion interactions are largely impcating its aggregation. HPAM has a high propensity to form large-size aggregates in brine solution. An interesting ionic effect has been observed; Ca2+ ions showed a high affinity toward HAPM compared to Mg2+ and Na+ ions. The electrostatic forces and ionic dehydration free energy penalty are the two main factors that determine the HPAM ionic affinity. Short oligomers are noted to overestimate the tendency of the polymer to have compact conformations and underestimate its aggregation capacity in brine solutions. Simulations of oil–water systems show that HPAM has a spectator role on the interfacial tension in the absence of surfactants.

The promise of nanotechnology becomes limitless with the possibility of having functionalized molecular agents to "illuminate" the reservoir and intervene to alter adverse oil recovery conditions. The future reality of the reservoir nanoagents concept is herein lab and field demonstrated with the industry first building block nanoagents' template. The template is intentionally geared towards the harsh but prolific Arab-D carbonate formation of the giant Ghawar field of Saudi Arabia. The challenge is magnified by a condition of 100 • C or greater temperature and 120,000 ppm or more connate water salinity. The industry's first proven reservoir nanoagents template is introduced and demonstrated via a push-pull field trial in an observation well. The testing objectives, processes, and results are outlined and further detailed in the paper. 25-28 September 2011.

Diffusiophoresis is the migration of a colloidal particle through a viscous fluid, caused by a gradient in concentration of some molecular solute; a long-range physical interaction between the particle and solute molecules is required. In the case of a charged particle and an ionic solute (e.g., table salt, NaCl), previous studies have predicted and experimentally verified the speed for very low salt concentrations at which the salt solution behaves ideally. The current study presents a study of diffusiophoresis at much higher salt concentrations (approaching the solubility limit). At such large salt concentrations, electrostatic interactions are almost completely screened, thus eliminating the long-range interaction required for diffusiophoresis; moreover, the high volume fraction occupied by ions makes the solution highly nonideal. Diffusiophoretic speeds were found to be measurable, albeit much smaller than for the same gradient at low salt concentrations.

Foams are used as divergent fluids for conformance control in enhanced oil recovery (EOR) operations. It is created by mixing a surfactant and a gas in situ in high-permeability reservoirs (e.g., surfactant alternating gas or SAG). Foams exhibit instability issues at reservoir conditions with a highly complex pore network, high pressure, high temperature, and high salinity. Here, we examine the stability and efficacy of foams formed with and without the addition of carbon nanoparticles (or nanodots). Carbon particles have demonstrated stability, mobility, and scalability for harsh reservoir environment use and application as a tracer technology. In this study, we investigate the feasibility of using inexpensive carbon dots as “foam boosters.” The experiments involved using different levels of brine salinities (ranging from seawater to formation connate water), different concentrations of the nanodots (ranging from 5 to 500 ppm), different types of surfactants (anionic, cationic, and nonionic) and gases (CO2, N2, and air), and different levels of temperature (ranging from 27 to 100 °C) to target representative conditions of Saudi Arabian reservoirs. In addition, we examined both foam structure, such as the gas–liquid interface, and liquid film lamella to better understand the mechanisms contributing to foamability and foam stability. The study highlights and unravels the complex interrelationship of the different influencing components on the stability of foam with the addition of the carbon particles. The bulk and porous media stabilities of the foams are analyzed using a static foam analyzer and an HP/HT core-flood system, respectively. Foam stability is assessed in terms of type and amount of modified/functionalized carbon particles, surfactant, and gas. We observed that the bulk foam containing only trace amounts (5–10 ppm) of carbon nanodots shows improved stability in a high-salinity medium. The particles improved the foam stability maximum by 70% and more than doubled the foam half-life for some foams. Confocal microscopy images of the foam structure of systems containing an increased concentration of carbon particles reveal an increased thickness of the lamellae and a decreased average bubble size. This is a clear indication of the enhanced foam stability. Carbon dots decreased the drainage rate of the lamellae and delayed the bubble rupture point or coalescence. The particles improved the foam stability by preferentially positioning itself in the lamella and preventing liquid drainage and film thinning.