Исследование межфазного натяжения на границе воды и раствора асфальтенов в толуоле

The dynamics of the interfacial tension coefficient at the interface between water and model solutions of asphaltenes of different concentrations in toluene has been studied. It has been shown that, over time, the interfacial tension decreases due to the adsorption of asphaltene molecules at the interface. With an increase in the concentration of asphaltenes in the solution, the decrease in interfacial tension occurs more intensively. The results of a study of the elongation of a water drop in a solution under the influence of an electric field are presented. It is shown that after the formation of an adsorption film, a higher stress must be applied to stretch the droplet, and the relative elongation depends nonlinearly on the applied stress. The studies were carried out using the suspended drop method.

Screening of Surfactants for Huff-N-Puff Injection into Unconventional Reservoirs

The gradual depletion of conventional oil reserves and the growing demand for hydrocarbon feedstock have led to shale deposits development necessity, which are characterized by high reservoir temperatures and very low permeabilites. One of the methods proposed for unconventional reservoirs development is surfactant injection in huff-n-puff mode. Unlike surfactant flooding, where the main effect is achieved through the displacement mechanism, the huff-n-puff method is based on capillary imbibition. Surfactant solutions decrease oil-water interfacial tension, change rock surface wettability to water-wet, lead to desorption of adsorbed hydrocarbons and increase relative permeability to water, thus increasing oil production. A number of commercially available anionic and nonionic surfactants were selected for laboratory investigation. Compatibility with reservoir fluids and thermal stability were tested for 14 days. For the stable compositions, the interfacial tension at the boundary with oil was measured with the spinning drop method. Special attention was paid to the study of initial reservoir wettability and the ability of the selected surfactants to shift it towards water-wet. Wettability at the macro level was determined by the "sessile" drop method. As a result of the screening, two surfactant compositions capable to alter the wettability of the rock surface to strictly water-wet were selected, as this is the key point when selecting surfactant compositions for low-permeable reservoirs. The optimum operating concentrations were selected to avoid the formation of a Winsor III microemulsion, which can lead to plugging of narrow channels and fluid flow blockage in the formation. Values of static adsorption onto crushed rock were also evaluated. The most effective composition was investigated in a huff-n-puff filtration experiment and positive results were obtained. Nanoparticles were also screened as potential components of surfactant compositions. It was found that nanoparticles forming stable dispersions in surfactant solutions improve their ability to change the wettability to a water-wet state. As a result of the laboratory work performed, it can be concluded that the huff-n-puff technology is applicable in unconventional reservoirs with very low permeabilities. The huff-n-puff mode for surfactant solutions injection is preferable due to lower surfactant consumption, targeted effect, and shortened well response time. Successful implementation of this technology on an industrial scale can improve the efficiency of shale oil production.

Blood test using the "thick drop" method

I hardly need to talk about that. how important is the timely and rapid recognition of infectious diseases such as relapsing fever and malaria. Since the causative agents of these diseases in a certain period of the disease are in the peripheral blood, the usual method of recognizing these diseases is a blood test.

Multiplexed and reproducible high content screening of live and fixed cells using the Dye Drop method

High throughput measurement of cell perturbation, by libraries of small molecules or gene knockouts, is a key step in functional genomics and pre-clinical drug development. However, it is difficult to perform viable, single-cell assays in 384-well plates, limiting many studies to simple well-average measurements (e.g. CellTiter-Glo). Here we describe a public domain "Dye Drop" method in which sequential density displacement is used to perform multi-step assays for cell viability and EdU incorporation followed by immunofluorescence imaging. The method is rapid, reproducible, can be readily customized, and is compatible with either manual or automated laboratory equipment. We demonstrate Dye Drop in the collection of dose-response data for 67 drugs in 58 breast cancer cell lines and separate cytostatic and cytotoxic responses, thereby providing new insight into the effects of specific drugs on cell cycle progression and cell viability. Dye Drop substantially improves the tradeoff between data content and cost, enabling collection of large information-rich datasets.

The Oscillatory Spinning Drop Technique. An Innovative Method to Measure Dilational Interfacial Rheological Properties of Crude Oil-Brine Systems in the Presence of Asphaltenes

The oscillatory spinning drop method has been proven recently to be an accurate technique to measure dilational interfacial rheological properties. It is the only available equipment for measuring dilational moduli in low interfacial tension systems, as it is the case in applications dealing with surfactant-oil-water three-phase behavior like enhanced oil recovery, crude oil dehydration, or extreme microemulsion solubilization. Different systems can be studied, bubble-in-liquid, oil-in-water, microemulsion-in-water, oil-in-microemulsion, and systems with the presence of complex natural surfactants like asphaltene aggregates or particles. The technique allows studying the characteristics and properties of water/oil interfaces, particularly when the oil contains asphaltenes and when surfactants are present. In this work, we present a review of the measurements of crude oil-brine interfaces with the oscillating spinning drop technique. The review is divided into four sections. First, an introduction on the oscillating spinning drop technique, fundamental and applied concepts are presented. The three sections that follow are divided according to the complexity of the systems measured with the oscillating spinning drop, starting with simple surfactant-oil-water systems. Then the complexity increases, presenting interfacial rheology properties of crude oil-brine systems, and finally, more complex surfactant-crude oil-brine systems are reviewed. We have found that using the oscillating spinning drop method to measure interfacial rheology properties can help make precise measurements in a reasonable amount of time. This is of significance when systems with long equilibration times, e.g., asphaltene or high molecular weight surfactant-containing systems are measured, or with systems formulated with a demulsifier which is generally associated with low interfacial tension.

An on-demand, drop-on-drop method for studying enzyme catalysis by serial crystallography

Serial femtosecond crystallography has opened up many new opportunities in structural biology. In recent years, several approaches employing light-inducible systems have emerged to enable time-resolved experiments that reveal protein dynamics at high atomic and temporal resolutions. However, very few enzymes are light-dependent, whereas macromolecules requiring ligand diffusion into an active site are ubiquitous. In this work we present a drop-on-drop sample delivery system that enables the study of enzyme-catalyzed reactions in microcrystal slurries. The system delivers ligand solutions in bursts of multiple picoliter-sized drops on top of a larger crystal-containing drop inducing turbulent mixing and transports the mixture to the X-ray interaction region with temporal resolution. We demonstrate mixing using fluorescent dyes, numerical simulations and time-resolved serial femtosecond crystallography, which show rapid ligand diffusion through microdroplets. The drop-on-drop method has the potential to be widely applicable to serial crystallography studies, particularly of enzyme reactions with small molecule substrates.