Entrapped Phase Research Articles

Simulation of Nonwetting Phase Entrapment within Porous Media Using Magnetic Resonance Imaging

Models representing the pore structures of amorphous, mesoporous silica pellets have been constructed using magnetic resonance images of the materials. Using magnetic resonance imaging (MRI), maps of the macroscopic (approximately 0.01-1 mm) spatial distribution of porosity and pore size were obtained. The nature and key parameters of the physical mechanism for mercury retraction, during porosimetry experiments on the silica materials, were determined using integrated gas sorption experiments. Subsequent simulations of mercury porosimetry within the structural models derived from MRI have been used to successfully predict, a priori, the point of the onset of structural hysteresis and the final levels of mercury entrapment for the silicas. Hence, a firm understanding of the physical processes of mercury retraction and entrapment in these amorphous silica materials has been established.

Satiated relative permeability of variable-aperture fractures

Experimental studies of capillary-dominated displacements in variable-aperture fractures have demonstrated the occurrence of a satiated state at the end of invasion, where significant entrapment of the displaced phase occurs. The structure of this entrapped phase controls the behavior of flow and transport processes in the flowing phase. Recent studies have shown that the areal saturation of the flowing phase at satiation (S(f) ) is largely controlled by a single parameter C/delta , where C , the curvature number, weighs the mean in-plane interfacial curvature relative to the mean out-of-plane interfacial curvature, and delta , the coefficient of variation of the aperture field, represents the strength of interface roughening induced by aperture variations. Here we consider the satiated relative permeability (k(rs)) to the flowing phase, which is defined as the relative permeability when the defending phase is fully entrapped. The satiated relative permeability is shown to be a well-defined function of S(f) over a wide range of C/delta , ranging from capillary fingering with significant entrapment (C/delta-->0) to smooth invasion with very little entrapment (C/delta > 1) . We develop a relationship for k(rs) as a function of S(f), by combining theoretical results for the effective permeability in a spatially correlated random permeability field, with results from continuum percolation theory for quantifying the influence of the entrapped phase. The resulting model for k(rs) also involves a dependence on delta . The predicted relative permeability values are accurate across the entire range of phase structures representative of capillary-dominated displacements in variable-aperture fractures.

Effects of heat-treatment conditions on microstructure of multi-coating Y123 films deposited by advanced TFA-MOD method

YBa 2Cu 3O 7− δ (Y123) films were deposited under various water partial pressures ( P H 2O ) in the crystallization process by the advanced metalorganic deposition (MOD) method using trifluoroacetates. Microstructures of the films were evaluated by means of transmission electron microscopy. As a result, in the Y123 film crystallized under lower P H 2O such as 2.1%, large pores were remarkably observed. Furthermore, there were many amorphous layers of a non-superconducting phase in this film. In contrast, small pores were distributed in the films deposited under higher P H 2O . Considering that the critical current ( I C) values become higher as P H 2O increases, existence of large pores and non-superconducting phase crystals causes to reduce I C. Through the investigation of the microstructure of the films quenched during the crystallization process, it was found that the pores in the film are generated by reaction of the non-superconducting phases, which are trapped in the growing Y123 film afterwards, to transform to Y123 with accompanied by the volume reduction of about 30%. The sizes of the entrapped phase crystals in Y123 film depend on the P H 2O and it may determine the pore sizes in the final film.

次世代超電導線材の開発と特性評価 改良型ＴＦＡ‐ＭＯＤ法におけるＹ１２３膜組織形成機構と水蒸気分圧の影響

YBa2Cu3O7-δ (Y123) films were deposited under various water vapor partial pressures (P(H2O)) in the crystallization process by an advanced metalorganic deposition (MOD) method using trifluoroacetates. Microstructures of the films were evaluated by means of transmission electron microscopy. As a result, in the Y123 film crystallized under lower P(H2O) such as 2.1%, large pores were remarkably observed. Furthermore, there were many amorphous layers of non-superconducting phases in the film. In contrast, small pores were distributed in the films deposited under higher P(H2O) of 4.2, 6.3 and 13.5%. Considering that the critical current (Ic) values become higher as P(H2O) increases, the existence of large pores and non-superconducting phase compounds causes a reduction in Ic. By investigating the microstructures of the films quenched during the crystallization process, it was found that the pores in the films are generated by the reaction of the non-superconducting phases trapped in the growing Y123 film, which then transform to Y123 afterwards accompanied by volume reduction of about 30%. The sizes of the entrapped phase crystals in the Y123 film depend on the P(H2O), and this may determine the pore sizes in the final film.

Experimental and simulated solute transport in a partially‐saturated, variable‐aperture fracture

We compare solute transport experiments to simulations in a partially‐saturated, variable‐aperture fracture in measured fracture aperture and entrapped‐air geometry fields. The computational model tracks particles through a quasi‐three‐dimensional velocity field that is based on the two‐dimensional solution to the Reynolds equation. The model predicts 84% of the relative increase in dispersion caused by the entrapped phase, and reproduces the experimentally observed nonlinear velocity‐dependence of solute dispersion.

The influence of capillarity on multiphase flow within porous media: a new model for interpreting fluid levels in groundwater monitoring wells in dynamic aquifers

A new approach is presented to calculate the volume of oil in the underground at an oil spill site from fluid levels in monitoring wells. The approach includes the effects of hysteresis due to irregular pore geometry and to phase entrapment. It is possible to explain the drastic changes in the oil thickness in a monitoring well due to the decrease and increase in the groundwater table. A correct evaluation of the oil volume infiltrated underground from an oil spill and the effective control of remediation works can only be done by using the newly developed approach with a consideration of the dynamic changes in the groundwater table.

Investigation of the residual–funicular nonwetting-phase-saturation relation

The constitutive relation that describes the amount of nonwetting fluid phase entrapment is critical to the modeling of multiphase flow in porous media, but it has received insufficient attention in the literature. We studied this relation using both experimental and modeling approaches: we used a nondestructive, X-ray monitored, long-column experiment that yielded a rich data set for two different porous media; we also used a quasi-static network model to simulate the experimental data and examine mechanisms affecting the relation. The experimental work yielded a significant data set for residual nonwetting phase (NWP) saturation as a function of maximum funicular nonwetting phase saturation. We suggest a functional form that represents the observed data sets accurately. Network model calibration to experimental data yields acceptable model-data agreement and a clear understanding of constraints that should be satisfied when using such models to avoid physically unrealistic behavior. We found that the pore-throat-size characteristics and the snap-off process occurring in pore throats strongly influence the manifestation of pore-body-size characteristics during imbibition and nonwetting fluid phase entrapment. We examined an estimation method proposed by Wardlaw and Taylor for the residual–funicular relation. We observed that the method yields an unrealistic relation for each porous media in the long-column experiments, and we used network modeling to understand the criteria that ensure a realistic estimate.

Factors controlling satiated relative permeability in a partially‐saturated horizontal fracture

Recent work demonstrates that phase displacements within horizontal fractures large with respect to the spatial correlation length of the aperture field lead to a satiated condition that constrains the relative permeability to be less than one. We use effective media theory to develop a conceptual model for satiated relative permeability, then compare predictions to existing experimental measurements, and numerical solutions of the Reynolds equation on the measured aperture field within the flowing phase. The close agreement among all results and data show that for the experiments considered here, in‐plane tortuosity induced by the entrapped phase is the dominant factor controlling satiated relative permeability. We also find that for this data set, each factor in the conceptual model displays an approximate power law dependence on the satiated saturation of the fracture.

Procedure for Preparation of Vesicles with No Leakage from Water-in-oil Emulsion

Abstract Vesicle are prepared in a two-step procedure. Firstly, water in oil (W/O) emulsion are prepared by sonication. Then water droplets contact with monolayer at the phase interface due to centrifugal and transform into vesicles. Size of vesicles is 50-200 nm and the encapsulation efficiency is 60%. The main advantage of this method is that no leakage of the chemicals to be encapsulated occurs during the preparation. Therefore, vesicles can be directly prepared in an aqueous medium different from the entrapped phase and purification of vesicles is generally not needed.

Preparation of Liposomes with a Controlled Assembly Procedure

A method of liposome preparation that involves two experimental steps is demonstrated. First, water in oil (W/O) emulsions are prepared by sonication. Then, due to centrifugal force, water droplets in the emulsion contact the monolayer at the oil/water interface and transform into liposomes after the monolayer has enwrapped the droplets. This procedure results in liposomes with diameters in the range 50–200 nm. Advantages of this procedure include relatively high (60%) encapsulation efficiency, direct preparation of liposomes in an aqueous medium different from the entrapped phase, and no leakage of the encapsulated chemicals during preparation. This relatively simple and rapid method may be useful in the encapsulation of drugs, enzymes, and other macromolecules as well as in the study of membrane properties.

Quantitative visualization of entrapped phase dissolution within a horizontal flowing fracture

Quantitative visualization of entrapped phase dissolution within a horizontal flowing fracture

Quantitative visualization of entrapped phase dissolution within a horizontal flowing fracture: R. J. Glass & M. J. Nicholl Geophysical Research Letters, 22(11), 1995, pp 1413–1416

Quantitative visualization of entrapped phase dissolution within a horizontal flowing fracture: R. J. Glass & M. J. Nicholl Geophysical Research Letters, 22(11), 1995, pp 1413–1416

Quantitative visualization of entrapped phase dissolution within a horizontal flowing fracture

An experiment was conducted to demonstrate the utility of quantitative fracture flow visualization techniques in the study of entrapped fluid phase (air) dissolution into a flowing phase (water) within a horizontal, transparent, analog rough‐walled fracture. The fracture aperture field and phase occupancy were measured using light transmission techniques and then combined to calculate bulk water‐phase saturation within the fracture as a function of time. Fracture relative permeability as a function of water‐phase saturation showed a smooth power law behavior during dissolution. Periodic step pulses of clear water within the dyed water inflow yielded dye concentration fields that demonstrate channeling induced by the entrapped air phase. Clusters of the entrapped air‐phase exhibited three types of dissolution behavior: general shrinkage, interfacial recession along cluster appendages, and cluster splitting. Locations for the advance of the wetting phase (water) into a nonwetting entrapped air cluster on its dissolution are not always correlated with either zones of high mass transfer rate (as inferred from gradients in the pulsed dye concentration fields) or with narrow apertures where the wetting phase has been thought to most easily invade. These results suggest that within an individual cluster of the entrapped phase, fluid pressure is at equilibrium and that the path of cluster shrinkage may be controlled primarily by capillary forces resulting from the full three‐dimensional curvature that minimizes surface energy of the phase interface.

Effect of pH on the morphology OFLactobacillus helveticusin free‐cell batch and immobilized‐cell continuous fermentation

Abstract The effect of pH control set point in the 4.3–6.3 range on the morphology of Lactobacillus helveticus was studied in free‐cell batch and immobilized‐cell continuous fermentations using a supplemented whey permeate medium. The mean chain length of L. helveticus was measured by microscopic observation in both free and entrapped phase. In free‐cell batch fermentation, chain elongation of L. helveticus occurred progressively when pH set point was in the 5.1–6.3 range. During immobilized‐cell continuous fermentations, morphology was much less pH‐dependent. This phenomenon could be due to the long response time of entrapped cells to daily random changes in pH set point. Bacterial counts, dry weight and optical density measurements were compared in order to develop a methodology to ensure accurate biomass measurement in the different phases of the immobilized‐cell bioreactor.

Phase decomposition in poly-p-phenylene benzobisoxazole/amorphous nylon molecular composites

Abstract Miscibility characteristics of poly-p-phenylene benzobisoxazole (PPBO)/amorphous nylon (AN) molecular composites were studied by means of differential scanning calorimetry (DSC), dielectric relaxation, wide-angle x-ray diffraction (WAXD), and light scattering. The solution-mixed PPBO/AN exhibited a systematic movement of a single glass transition temperature (T g) with composition in DSC and dielectric measurements, implying an entrapped single phase of the molecular composites. In the WAXD studies of the 50/50 mixture, two very weak reflection peaks of the PPBO phase and a small amorphous halo of AN were discerned. Light scattering studies showed no detectable level of orientation fluctuations. Upon heating, thermally induced phase separation occurred, with a cloud point phase diagram reminiscent of a lower critical solution temperature (LCST). As typical for entrapped single-phase blends, the phase diagram of LCP blends is irreversible. Nevertheless, several temperature jump experiments were un...

The Laforma deposit, an atypical epithermal-Au system at Freegold Mountain, Yukon Territory, Canada

Gold mineralization at Freegold Mountain is temporally and spatially related to Late Cretaceous rhyolitic volcanism. Gold-bearing quartz veins such as the Laforma deposit are high-grade, low-tonnage deposits with grades ranging from 0.4 to 1.0 oz/t. Fluid inclusions from the lower portions of the Laforma mine homogenize at 185°C and have salinities between 2 and 4.5 eq.wt.% NaCl. Above the deeper ore, fluid inclusions homogenizing to the liquid phase show extreme ranges in homogenization temperatures (165–430°C) due to two phase entrapment of a boiling fluid, and a wide variation in salinity (4–43 wt.% NaCl). Although evidence for boiling is commonly reported in epithermal systems, fluids of such high salinity have not been recorded in past studies. These highly saline fluids are interpreted to be residual brines, left from a period of extensive boiling of a hydrothermal fluid with an initial concentration of around 4 wt.% NaCl. To achieve such high salinities, a high-enthalpy, steam-dominated system closed to dilution by surface water is required. Fluid-inclusion waters from the lower levels of the deposit, below the boiling zone, have stable isotopic signatures indicative of meteoric water with δD=−138% and δ 18O=−18.4%. Boiling of the Laforma fluid has caused a marked shift towards heavier hydrogen and oxygen isotopic values and has resulted in the precipitation of carbonate and silicate gangue minerals and gold. Fluid-inclusion evidence indicates that boiling zones at Laforma formed between 1 and 1.5 km below the Late Cretaceous paleosurface and stable isotopic evidence suggests that the paleolatitude of Freegold Mountain during the Late Cretaceous time was south of the present-day Yukon-B.C. border.

Configuration of a Two-Phase Jet

Abstract Measurements of the velocity and concentration distributions for an air jet containing fine particles of coal of mean diameter 30 mm were made in the fully developed region between 20 and 60 nozzle radii. An analytical model is developed using Field's two phase entrapment equation and the predictions for the structure of the jet tally with the experiments.

The Optimal Salinity Concept For Oil Displacement By Oil-external Microemulsions And Graded Salinity Slugs

Abstract Our laboratory studies showed that the concept of the optimal salinity, as derived from phase behaviour or interfacial tensions of microemulsions, is applicable to oil displacement by soluble oils in porous media. Maximal oil recovery was obtained when the salinity of connate water and polymer solution was at the optimal salinity of the surfactant formulation. In the present study, it is shown that the salinity of polymer solution is far more important than the salinity of connate water. When the salinity of polymer solution was at the optimal salinity of the surfactant formulation, high oil recovery efficiency was obtained over a wide range of connate water salinities. Evidence showed that the phase behaviour of the surfactant slug in porous media is largely determined by the salinity of the polymer solution. For better mobility control and minimum surfactant loss, a two-slug design of the surfactant formulation was employed. In this design, the first surfactant slug has an optimal salinity close to the connate water salinity and the second surfactant slug has a much lower optimal salinity. The polymer solution salinity is made equal to the optimal salinity of the second surfactant slug. With this design, high oil recovery in Berea cores can be obtained even in the presence of high-salinity (6% NaCI + 1% CaCl2) connate water. The optimal salinity concept is further extended to include the effects of mobility control and surfactant dispersion and entrapment in porous media. The proposed salinity shock design of mobility polymer solutions employs two slugs of polymer solution in which the first polymer slug is at the optimal salinity of the preceding surfactant formulation and the second polymer slug is at a much lower salinity. With this unique design, high oil recovery and high surfactant recovery can be obtained for soluble oil flooding in sand packs, and the polymer consumption can be greatly reduced. INTRODUCTION Surfactant-polymer flooding processes for enhanced oil recovery ate influenced by a number of parameters. These include reservoir capillary properties(1%4), rock wettability(4%6), reservoir brine and mineralogy(7%14), and rock-fluid interactions (15%19). Connate water salinity and reservoir minerals can affect surfactant flooding through their effects on phase- behaviour, interfacial tensions with slug and residual oil, and mobility control, as well as on surfactant loss due to adsorption, precipitation and phase entrapment processes. By incorporating small amounts of clays or minerals in sand packs, it was shown (7) that the oil recovery efficiency of soluble oil flooding processes greatly diminishes due to the presence of the clays and minerals. Even when clays or divalent cations are absent or in trace amounts, NaCI alone can effectively deteriorate the performance of oleic(8) and aqueous surfactant flooding processes (11%14). Such detrimental effects can often be minimized by means of preflush and optimal salinity design (11,20) of the surfactant slug for a given surfactant and cosurfactant system. The design basis is that for a given surfactant formulation and oil; there exists a salinity at which minimum interfacial tensions occur when surfactant, cosurfactant, oil and brine are equilibrated.

The Effect of Sulfonate/Polymer Interaction on Mobility Buffer Design

A study was made of the movement of 1-PV slugs of polymer solutions in cores that had been treated previously with sulfonate and then flushed with previously with sulfonate and then flushed with brine. The data revealed premature polymer breakthrough. These results were attributed to low polymer retention and an inaccessible pore volume polymer retention and an inaccessible pore volume to polymer flow. The shapes and absolute values of the polymer breakthrough curves depended on the type of polymer and sulfonate used. When no brine flush followed the sulfonate solution, an even earlier polymer breakthrough was observed. This phenomenon was thought to be related mainly to a phenomenon was thought to be related mainly to a polymer/sulfonate interaction. polymer/sulfonate interaction. Solutions of 10 chemically different polymers were blended with solutions of four sulfonates. After standing, these mixtures separated into two layers - a top layer highly concentrated in polymer and a bottom layer containing a higher sulfonate concentration. Viscosities, fractional volumes, and interfacial tensions to oil of the separated layers depended on the particular polymer/sulfonate system. These layers were found to be separate phases with a measurable, but very low, interfacial phases with a measurable, but very low, interfacial tension at the phase boundary. The effect of salinity and polymer concentration on phase separation also was studied. Phase separation of polymer/sulfonate systems also occurred in Berea core flow tests, resulting in differing mobilities of the separated phases. This phenomenon can result in a low recovery efficiency in low-tension surfactant flooding. An improvement in tertiary oil recovery efficiency was achieved, however by using low salinity in the mobility bank. Introduction This study discusses low-tension oil displacement, wherein an aqueous surfactant slug is driven by a polymer solution. Many papers have dealt with such systems, particularly as they relate to tertiary oil recovery; however, little attention has been devoted to polymer behavior in the polymer/sulfonate mixing zone. Recently, Trushenski et al. reported that high mobility had developed in the polymer/sulfonate mixing zone. The mechanism for this phenomenon was not proposed. They also showed that because of polymer/sulfonate incompatibility, phase separation can occur, which can lead to excessive sulfonate retention through "phase entrapment." This study investigates this phase-separation phenomenon and its effect on flow behavior in the phenomenon and its effect on flow behavior in the polymer/sulfonate mixing zone. polymer/sulfonate mixing zone. POLYMER INJECTION INTO POLYMER INJECTION INTO SULFONATE-TREATED BEREA CORES PROCEDURE PROCEDURE In one set of experiments, two sulfonate solutions [Witco TRS-18/40, (1/1) and Amoco H-4344-1 Tm] were injected into separate Berea cores. Concentrations were 2 wt % (0.02 kg/kg) in 2%. NaCl brine, volume was 2 PV, and the injection rate was 14 ft/D (4.27 m/d). Thereafter, 3 PV of 2% NaCl brine was injected at the same rate. This was followed by 1 PV of 600-ppm polymer solution in 2% NaCl brine, then by 2% NaCl brine. During the last two cycles, the injection rate was 4 ft/D (1.22 m/d). During both polymer injection and the subsequent brine flush, the inlet pressure was recorded and effluent samples were taken to analyze polymer concentration. Polymer concentrations were determined by radioactivity in the case of C14-tagged polymers (Polymers 454 and 340 trade mark) and by the viscosity measurement technique when Kelzan MF (trade mark) was used. In the second set of experiments, a polymer solution directly followed the sulfonate solution. Injection rates were the same as in the first set of experiments. Both sets of experiments used Berea cores, 5.08 cm in diameter and 14.2 cm in length. Each polymer solution was filtered through a separate Berea core disk with about 500 md permeability and with diameter and length of 5.08 and 1.4 cm, respectively. SPEJ P. 4

CONSIDÉRATIONS SUR L'INFLUENCE DE LA PHASE GAZEUSE PIÉGÉE DANS LES MILIEUX POREUX

Abstract In porous media, entrapped gas is considered as an important factor reducing the transmissibility of fluids through the medium. Because entrapment mecanisms are poorly known and entrapped gas content is a function not only of water content but also of time due to the gas solubility, experimental results do not match satisfactorily with the diffusivity or continuum mecanics theories which do not take the entrapped gas phase into account. Measurement of entrapped gas content are presented together with the corresponding water content hysteresis isotherm.