Thin Oil Layer Research Articles

Dynamics of a bubble bouncing at a liquid/liquid/gas interface

We study the dynamics of an air bubble bouncing at a liquid/liquid/gas interface, which we refer to as a compound interface. When a bubble interacts with a thin layer of oil on top of bulk water, the oil layer modifies the interfacial properties and thus the entire process of bouncing and bubble bursting. The influence on the bubble motion is experimentally and numerically investigated. Based on the coefficient of restitution and the damping rate of the bubble velocity profile, the damping increases with the oil layer thickness and viscosity. In addition, the effect of the oil layer thickness is more prominent for high-viscosity oil. Furthermore, a reduced-order mass–spring–damper model is proposed to describe the bubble bouncing at the compound interface, which predicts the time of the first contact of the bubble with the interface and agrees well with the experimental results. Such a model also captures the general experimental trends of the coefficient of restitution for the multiphase system. Our work contributes to a further understanding of the collision and coalescence of bubbles with a compound interface.

THE PROBLEMS OF HYDRODYNAMIC NON-ISOTHERMAL LUBRICATION

The classical hydrodynamic theory of slide bearing lubrication has been constituted on the assumption of constant pressure and viscosity perpendicular to the thin oil layer thickness. These fundamental assumptions are in contradiction to contemporary achievements connected with new devices such as micro-bearing, nano-bearing, magnetic bearings, artificial joints in humanoid robots, micro-motors. Therefore, new methods of measurements and calculations using AFM and a new mathematical computer programs are needed. Energy conservation equations after boundary layer simplifications confirm the fact that temperature gradient variations across the film thickness have the same order of magnitude as the variations in longitudinal or circumferential directions. The fact that temperature gradient variations across the bearing gap height can be significantly large are evident, despite the temperature differences across the film thickness that are negligibly small. This statement cannot be compliant with the assumption of a constant viscosity value in the gap height direction. It has been proven that hydrodynamic pressure is not constant across the film thickness for non-Newtonian oils with Rivlin Erickson constitutive equations. For pseudo-plastic non-Newtonian oils, the apparent dynamic viscosity significantly decreases with shear rate increases. However, for pseudo-plastic oils, the shear rate increments during the oil flow are strictly connected with the average flow velocity increments. Therefore, the apparent dynamic viscosity depends strongly on the oil velocity gradients. It is evident that flow velocity gradients across the film thickness have intensive variations, particularly in regions where gap height attains the least value. In these places, the dynamic viscosity attains the largest variations in gap height directions. If gap height in micro-bearing is smaller than one micrometre, than the largest oil dynamic viscosity increments caused by the velocity variations across the film thickness are located near the superficial layer of the movable journal surfaces in the case of the hydrodynamic lubrication by rotation, but in the neighbourhood where each of two come near lubricated surfaces during the squeezing. Hence, in these places, dynamic viscosity increases across the film thickness and attains the local maximum values. A gap height smaller than one micrometre has the largest oil dynamic viscosity increments caused by the adhesion force variations across the film thickness located near the motionless sleeve surfaces. In a similar manner, the influences on the viscosity variations caused by the cluster points of concentrations of nano particles as oil inhibitors or oil additives smaller than 5 nm occurring in micro-bearing gaps and the cluster concentration regions of collagen fibres occurring in human joint gap are observed. This paper describes and comments on the above-mentioned problem of oil viscosity changes in the gap height direction, and it presents the apparent dynamic viscosity functions for Newtonian and non-Newtonian oils as well indicates the largest viscosity variations in bearing gap height direction and gives examples of initial calculation results.

Localization and identification of thin oil layers using a slim-borehole nuclear magnetic resonance tool

In the recent years, slim-borehole nuclear magnetic resonance (NMR) tools, designed for shallow hydrogeological applications, have become available. We have developed and improved the performance of one of them to detect and characterize hydrocarbon contamination. Our objectives were (1) to generally increase the vertical resolution of NMR logs below the instrumental resolution to detect thin layers and (2) to study the feasibility of using these tools to distinguish fluids (i.e., oil and water) using NMR diffusion measurements. To increase the vertical resolution, we have jointly inverted measurements made with overlapping sensitive volumes. We have developed an example in which a thin layer of 10 cm was successfully resolved. Using this approach, the instrumental resolution of the probe (50 cm) can be increased at the cost of additional measurement time. To differentiate and quantify the water and oil phases based on their contrast in diffusion coefficient, we have used a Carr-Purcell-Meiboom-Gill pulse sequence with varying echo spacings. We have found that, due to the low magnetic gradient of the probe, diffusion coefficients [Formula: see text] were difficult to resolve. Therefore, hydrocarbons with low diffusion coefficients, e.g., crude or rapeseed oil, cannot be uniquely identified, but can be quantified and clearly distinguished from water. Hydrocarbons with higher diffusion coefficients, e.g., diesel, kerosene, and gasoline, can be unambiguously identified based on their diffusion coefficient but may be difficult to distinguish from water. We have combined both approaches, enabling NMR logging to be used for fluid identification with increased vertical resolution. We have evaluated the performance of the measurement and inversion schemes using a controlled experimental setup consisting of a rapeseed oil layer on top of water in a tank.

New Drop Fluidics Enabled by Magnetic-Field-Mediated Elastocapillary Transduction.

This research introduces a new drop fluidics that uses a deformable and stretchable elastomeric film as the platform instead of the commonly used rigid supports. Such a soft film impregnated with magnetic particles can be modulated with an external electromagnetic field that produces a vast array of topographical landscapes with varying surface curvature, which, in conjunction with capillarity, can direct and control the motion of water droplets efficiently and accurately. When a thin layer of oil is present on this film that is deformed locally, a centrosymmetric wedge is formed. A water droplet placed on this oil-laden film becomes asymmetrically deformed, thus producing a gradient of Laplace pressure within the droplet and setting it in motion. A simple theory is presented that accounts for the droplet speed in terms of such geometric variables as the volume of the droplet and the thickness of the oil film covering the soft elastomeric film as well as material variables such as the viscosity of the oil and the interfacial tension of the oil-water interfaces. Following the verification of the theoretical result using well-controlled model systems, we demonstrate how the electromagnetically controlled elastocapillary force can be used to manipulate the motion of single and/or multiple droplets on the surface of the elastomeric film and how elementary operations such as drop fusion and thermally addressed chemical transformation can be carried out in aqueous droplets. It is expected that the resulting drop fluidics would be suitable for the digital control of drop motion by simply switching on and off the electromagnetic fields applied at different positions underneath the elastomeric film in a Boolean sequence. We anticipate that this method of directing and manipulating water droplets is poised for application in various biochemical reaction engineering situations, an example of which is the polymerase chain reaction (PCR).

In situ colorimetric detection and mixing of glucose–enzyme droplets in an open-surface platform via Marangoni effect

Precise detection of glucose concentration in blood is critical in health monitoring and medical research. This paper describes a novel approach for enzymatic glucose sensing (glucose oxidase based) using thermal gradient in an open-surface platform. In order to obtain glucose concentration, droplets of enzyme and glucose with various concentrations are dispensed on a thin layer of fluorinert oil. By engineering the location of the droplet on the fluid surface and controlling the surface temperature drop of the fluid, surface deformation is created with fluid recirculating due to Marangoni convection. The surface deformation allows the microliter droplets to collide and mix at the hot spot. Image processing of the colorimetric reaction of the glucose and enzyme allows accurate determination of glucose concentration. The designed biosensor offers high repeatability, and concentration is measured within ±9.5 % of standard absorptiometry method. Contact-free manipulation of droplets, in situ measurement of glucose concentration, fast response time and high sensitivity are the key advantages of this device.

CO2 storage potential and trapping mechanisms in the H-59 block of Jilin oilfield China

A CO2 EOR and storage pilot test have been conducted in the H-59 block of Jilin oilfield China for well seven years. It is important to track the CO2 storage and distribution in the reservoir, which can provide valuable guidance for the operation in the next stage of the project. In this paper, the CO2 storage capacity in the H-59 block was calculated by considering various CO2 trapping mechanisms, and the distribution and trapping status of the stored CO2 were evaluated by using the reservoir simulation method. The effective CO2 storage capacity in the H-59 block is estimated to be 26.37×104 ton by incorporating the CO2 sweep efficiency and neglecting the mineral trapping. Up to June 2014, 21.08×104 ton of CO2 has been injected with over 95% stored. The geological structure of the H-59 block controls most of the injected CO2 moving only along the horizontal direction in the thin oil layers. The shape and size of the CO2 plume are mainly determined by the reservoir heterogeneity, well pattern and injected CO2 amount. According to the assessment results, the CO2 sweep efficiency within each well group varies from 20% to 80%. About 42.68–60.15% of the stored CO2 has been trapped at supercritical state accompanied with 24.85–41.8% and 15% of the stored CO2 dissolved in residual oil and water, respectively. The H-59 block still has a potentially remaining capacity of 6.25×104 ton of CO2 for the future storage. Necessary engineering measures might be taken to further increase the sweep and displacement efficiencies of CO2 to achieve this purpose.

Monitoring on CO2 migration in a tight oil reservoir during CCS-EOR in Jilin Oilfield China

Jilin Oilfield is conducting a large-scale demonstration project on CO2 EOR (enhanced oil recovery) and storage in China. CO2 separated from a nearby natural gas reservoir (15–30 mol% CO2) is injected into the northern part of H59 oil block with permeability and porosity of 3.5 mD and 12.7%, respectively. After about six years of operation, nearly 0.26 million tons of CO2 (0.32 HCPV (hydrocarbon pore volume)) has been injected into the thin oil layers with well-developed natural fractures. In order to track the movement of CO2 in the oil reservoir, a microseismic monitoring program has been implemented to map the CO2 flow anisotropy and estimate its sweeping efficiency. Gas tracer testing has also been conducted to examine the inter-well connectivity. The temporal change of produced CO2 has been analyzed in a real-time mode to monitor the dynamic response in production wells. It is demonstrated that the migration of CO2 in the thin oil layers can be successfully detected by the microseismic technique, and the sweeping profiles of CO2 obtained from the inverted microseismic are in good agreement with the produced CO2 rate from production wells as well as the reservoir's petrophysical properties.

Cavity formation in the wake of falling spheres submerging into a stratified two-layer system of immiscible liquids

We experimentally study the cavities forming in the wake of rigid spheres when submerging into a stratified, two-layer system of immiscible, quiescent liquids comprising a thin layer of oil above a deep pool of water. The results obtained for our two-layer system are compared with data from the literature for the corresponding type of cavities formed when spheres enter a homogeneous liquid that is not covered by an oil layer. The discussion and the data analysis reveal that the oil coating acquired by the spheres while propagating through the thin oil layer, before entering the pool of water underneath, substantially affects qualitative and quantitative aspects of the dynamics associated with the cavity formation. In particular, we observe the formation of a ripple-like pattern on the cavity walls which is not known to exist when spheres enter a homogeneous liquid. The data analysis suggests that the ripple patterns form as a consequence of a two-dimensional instability arising due to the shear between the oil layer coating the spheres and the ambient water.

OS0406 動的な滑り摩擦実験とモデル解析

The present study investigated dynamic sliding friction of polyurethane (PU) rubber samples on an inclined smooth transparent polymethylmethacrylate (PMMA) surface with a thin layer of silicone oil. The two samples with different contact areas were used to study the sliding velocity as a function of the inclined angle. The results showed that the sliding velocity increased in the early stages of sliding and approached a constant value in the later stages. To understand the observed changes of the velocities, we proposed an analytical model, and found that the model can predict important changes of the velocities. Our findings suggest that the dynamic friction force can be dependent on both the sliding velocity and the contact area, and the similarity between the dynamic sliding friction and Stokes' law which describes the falling velocity of a small particle in a viscous fluid.

Effect of the layer height on heat transfer and the critical heat flux in evaporation of a fluid under low pressures

The results of an experimental study of heat transfer in the evaporation of a thin horizontal layer of VM-1S vacuum oil at low pressure are presented. The experimental data for the dependence of the heat flux density on the temperature difference at the critical heat flux in a wide range of heights of the liquid layer are assessed. It is shown that the critical heat flux increases in a narrow range of the layer heights by more than an order of magnitude. The values of the critical heat flux density in layers with a height less than the capillary constant are described by the Kutateladze equation. With increasing thickness of the layer, the critical heat flux increases sharply and reaches a constant value, which is in good agreement with the dependences calculated by Yagov and Landau.

Dynamic sliding friction and similarity with Stokes׳ law

This study investigated the dynamic sliding friction of polyurethane (PU) rubber samples on an inclined smooth transparent polymethylmethacrylate (PMMA) surface with a thin layer of silicone oil. The sliding velocity increased during the initial stages of sliding and approached a constant value toward the latter stages. To describe the changes in velocity observed, the present study developed an analytical model based on Couette flow with no pressure gradient and indicated that the model could predict important changes in velocity. These findings suggest that dynamic friction force is dependent on both the sliding velocity and the contact area, and that the behavior is similar to that given by Stokes׳ law, which describes the falling velocity of a particle in a viscous fluid.

A green way to clean up an oil spill

Materials Chemistry Cleaning thin films of light crude oil from the marine environment is a herculean task. Currently, silicone-based compounds are used, which can leave a permanent residue. Inspired by the natural pigments in plants, John et al. developed a plant-based oil-cleaning agent. The product functions as a “green” chemical herder to retract thin oil layers into a thickened mass suitable for recovery or burning. The biodegradable agent was as good as synthetic chemicals at corraling oil and left no residual contamination. Sci. Adv. 10.1126. sciadv.1400265 (2015)

The evolution of spatial ordering of oil drops fast spreading on a water surface.

The design of dynamically self-assembled systems is of high interest in science and technology. Here, we report a unique cascade in the self-ordering of droplets accompanied by a dewetting transition. The dynamic self-emergent droplets are observed when a thin liquid layer of an immiscible fluorocarbon oil (perfluorooctyl bromide, PFOB) is placed on a water surface. Due to the gradual evaporation of PFOB, a circular PFOB-free domain appears as a result of a local dewetting transition. A circular pearling structure is generated at the rim with the growth of the dewetting hole. As the next stage, linear arrays of droplets are generated in a radial manner from the centre of the hole. These one-dimensional arrangements then evolve into two-dimensional hexagonal arrays of microdroplets through collective rhythmical shrinking/expanding motions. The emergence of such dynamic patterns is discussed in terms of the nonlinear kinetics of the dewetting transition under thermodynamically dissipative conditions.

Prospect, isolation, and characterization of microorganisms for potential use in cases of oil bioremediation along the coast of Trindade Island, Brazil

In the present study, acrylic coupons with a thin layer of oil on the surface were incubated in the coastal water of Trindade Island, Brazil, for 60 days. The microorganisms adhered to the coupons were isolated using enrichment medium with hexadecane and naphthalene as the sole carbon and energy source. A total of 15 bacterial isolates were obtained, and the ability of these isolates to use different hydrocarbons as the source of carbon and energy was investigated. None of the isolates produced biosurfactants under our experimental conditions. Subsequently, identification methods such as partial sequencing of the 16S rRNA gene and analysis of fatty acids (MIDI) profile were employed. Among the 15 isolates, representatives of Actinobacteria, Firmicutes, and Alphaproteobacteria were detected. The isolates Rhodococcus rhodochrous TRN7 and Nocardia farcinica TRH1 were able to use all the hydrocarbons added to the culture medium (toluene, octane, xylene, naphthalene, phenanthrene, pyrene, hexadecane, anthracene, eicosane, tetracosane, triacontane, and pentacontane). Polymerase chain reaction amplification of the DNA isolated by employing primers for catechol 2,3-dioxygenase, alkane dehydrogenase and the alpha subunit of hydroxylating dioxygenases polycyclic aromatic hydrocarbon rings genes demonstrated that various isolates capable of utilizing hydrocarbons do not exhibit genes of known routes of catabolism, suggesting the existence of unknown catabolic pathways in these microorganisms. Our findings suggest that the microbiota associated to the coast of tropical oceanic islands has the ability to assist in environmental regeneration in cases of accidents involving oil spills in its shore. Thus, it motivates studies to map bioremediation strategies using the autochthonous microbiota from these environments.

Micro-arc ignition on the oily surface of capacitively-coupled plasma

Micro-arc ignition on the oily surface is investigated in a capacitively-coupled plasma (CCP) system. In this system, micro-arc generation is enhanced by increased level of plasma potential, which is induced by a DC-grounded coil between blocking capacitor and the powered electrode. The images of micro-arcs are captured with very short exposure time of 20 μs using intensified charge-coupled device triggered by a high speed comparator and the focused ground electrode is partially soiled with oil. The micro-arcs are observed only on the oily surface of the electrode. This observation provides that the oily surface of CCP is very weak for micro-arc ignition and micro-arc ignition is supposed to be enhanced by the oil evaporation and the thin oil layer, considering the RF Paschen breakdown of the oil vapor within the sheath and the dielectric breakdown of thin oil layer.

On the performance of laser-induced breakdown spectroscopy for direct determination of trace metals in lubricating oils

Laser-induced breakdown spectroscopy (LIBS) provides a technique to directly determine metals in viscous liquids and especially in lubricating oils. A specific laser ablation configuration of a thin layer of oil applied on the surface of a pure aluminum target was used to evaluate the analytical figures of merit of LIBS for elemental analysis of lubricating oils. Among the analyzed oils, there were a certified 75cSt blank mineral oil, 8 virgin lubricating oils (synthetic, semi-synthetic, or mineral and of 2 different manufacturers), 5 used oils (corresponding to 5 among the 8 virgin oils), and a cooking oil. The certified blank oil and 4 virgin lubricating oils were spiked with metallo-organic standards to obtain laboratory reference samples with different oil matrix. We first established calibration curves for 3 elements, Fe, Cr, Ni, with the 5 sets of laboratory reference samples in order to evaluate the matrix effect by the comparison among the different oils. Our results show that generalized calibration curves can be built for the 3 analyzed elements by merging the measured line intensities of the 5 sets of spiked oil samples. Such merged calibration curves with good correlation of the merged data are only possible if no significant matrix effect affects the measurements of the different oils. In the second step, we spiked the remaining 4 virgin oils and the cooking oils with Fe, Cr and Ni. The accuracy and the precision of the concentration determination in these prepared oils were then evaluated using the generalized calibration curves. The concentrations of metallic elements in the 5 used lubricating oils were finally determined.

A pneumatically-driven microfluidic system for size-tunable generation of uniform cell-encapsulating collagen microbeads with the ultrastructure similar to native collagen

This study reports a microfluidic system for high throughput, uniform, and size-tunable generation of cell-containing collagen microbeads. The principle is based on two pneumatically-driven mechanisms to achieve multi-channel mixture suspension transportation, and to actuate the spotting actions of micro-vibrators that continuously generate tiny collagen micro-droplets into a thin oil layer and then a sterile Pluronic® F127 surfactant solution located below. The temporarily formed collagen microdroplets are then thermally gelatinized. By regulating the feeding rate of cells/collagen suspension, and the spotting frequency of micro-vibrator, the size of the collagen microbeads can be manipulated. One of the key technical features is its capability to generate uniform collagen microbeads (coefficient of variation: 5.4-8.6 %) with sizes ranging from 73.9 to 349.3 μm in diameter. This is currently difficult to achieve using the existing methods particularly the generation of cell-encapsulating collagen microbeads with diameter less than 100 μm. Another advantageous trait is that the ultrastructure of the generated collagen microbeads is similar to that found in native collagen. In this study, moreover, the use of the proposed device for the microencapsulation of 3T3 cells in collagen microbeads has been successfully demonstrated showing that the encapsulated cells maintained high cell viability (96 ± 2 %). Furthermore, a reasonable proliferative capability of the encapsulated cells was observed during 7 days culture. As a whole, the proposed device has opened up a new route to generate cell-containing collagen microbeads, which is found particularly meaningful for biomedical applications.

Feasibility of wear metal analysis in oils with parts per million and sub-parts per million sensitivities using laser-induced breakdown spectroscopy of thin oil layer on metallic target

The performance of laser-induced breakdown spectroscopy for quantitative analysis of wear metals in oils has been evaluated in this work with a specific ablation configuration of a thin layer of oil covering the polished surface of a pure aluminum target. A set of reference samples containing 12 metallic elements (Ag, Al, Cr, Cu, Fe, Mg, Na, Ni, Pb, Si, Sn, and Ti) was prepared by dilution with a 75cSt hydrocarbon base oil for the concentration range from 20 to 500μg/g. Calibration curves were therefore established for these elements with an echelle spectrometer and then with a Czerny–Turner spectrometer. The obtained results show first high linearity of the calibration curves established with the two types of spectrometer, the determination coefficient, R2, of all the calibration curves are superior to 0.99. The limits of detection (LoDs) with an echelle spectrometer vary in the range from 0.29 to about 10μg/g with an average value of 6.02μg/g for the 9 elements (Al, Na and Pb excluded). The use of a Czerny–Turner spectrometer reduces furthermore the LoDs to the range from 0.24 to about 10μg/g with an average value over the 10 elements (Al and Na excluded) of 4.04μg/g. In addition, the LoDs for the 3 elements (Mg, Cu and Ag) are determined lower than μg/g, i.e. in the sub-ppm level. Comparison with the previously published data shows moreover the efficiency of the introduced ablation configuration as one of the most suitable methods for highly sensitive and precise wear metal analysis in oils.

Intelligent-Well Completion in the Troll Field Enables Feed-Through Zonal Isolation

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 160060, ’First Intelligent-Well Completion in the Troll Field Enables Feed- Through Zonal Isolation: A Case History,’ by Bjorn Olav Dahle, Statoil, and Peter E. Smith, Geir Gjelstad, and Kristian Solhaug, Halliburton, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8-10 October. The paper has not been peer reviewed. Statoil, operating the Troll field in the Norwegian sector of the North Sea, wished to run a deep sidetrack from the main bore in a multilateral well that would exit through the liner in the reservoir. Several zonal-isolation methods had been evaluated, but on the basis of previous experience Statoil decided to use swellable-packer technology. Testing revealed that this type of completion would exceed the necessary requirements. The installation was performed from a semisubmersible rig ahead of plan. Introduction The Troll field lies approximately 65 km west of Kollsnes, near Bergen, Norway. Although the field historically has produced large amounts of oil, it is now primarily a gas producer and contains approximately 40% of the total gas reserves on the Norwegian continental shelf. The gas reservoirs, which are 1400 m below sea level, are expected to produce for at least another 70 years. The massive Troll A platform produces gas, while Troll B, a floating process and accommodation platform with a concrete hull, and Troll C, a floating process and accommodation platform with a steel hull, produce from thin oil-bearing layers in the Troll West reservoir. The thin oil layer is between 22 and 26 m thick in the Troll West oil province and is between 11 and 13 m thick in the Troll West gas province. In order to recover oil from the thin layer, it has been necessary to develop advanced drilling and production technology. All of the more than 110 production wells to be drilled are horizontal wells. This process requires two-phase drilling. The first phase drills down to the reservoir, 1600 m beneath the sea bottom, and then the second phase drills to 3200 m in a horizontal direction through the reservoir. Twenty-eight of the wells are multilaterals that have two or three horizontal laterals. The well in question faced several challenges normally not seen in Troll multilateral completions, including standalone-screen completion with zonal isolation, well paths with doglegs and a completion total depth (TD) of more than 6000 m, top completion with zonal isolation and zonal control for four zones, and the need for dual pressure and temperature monitoring for all oil zones.

Performance Evaluation of S/P System and its Mechanism Analysis

Xinbei Oilfield in Jilin is a tectonic lithology reservoir with high porosity, high permeability, thin oil layers and severe heterogeneity, which has entered a period of high water-cut development. Aiming at actual demand of field development, making use of indoor apparatus monitoring and theoretical analysis method, the author evaluated the viscosity, interfacial tension, absorption characteristics, rheological property, viscoelasticity and displacement efficiency of 5 different binary composite systems composed of surfactants and polymer to optimize the binary flooding system. The results show that Daqing Lianhua/Polymer system can achieve ultra-low interfacial tension with crude oil with small absorption, well stability and little effect on viscoelasticity of polymer solution. The system has higher displacement efficiency and stronger mobility control ability, which is recommend as flooding system for oilfield.