Gas Liquid Displacement Research Articles

A review on microfiltration membranes: fabrication, physical morphology, and fouling characterization techniques

Microfiltration is a commonly used pressure-driven membrane separation process for various applications. Depending on the manufacturing method, either tortuous or capillary pore structures are obtained. The structure plays an important role in controlling flux, selectivity, but most importantly, the fouling tendency of the membrane. This review attempts to cover past and current developments in physical morphology and fouling characterization methods, along with the manufacturing methods for microfiltration membranes. The limitations and advantages of direct microscopic techniques and gas-liquid displacement as an indirect method are discussed for physical characterization. Additionally, the current state of the art and technical challenges for various in-situ and ex-situ fouling characterization techniques are also discussed. Finally, some directions for future research are outlined.

Mechanism of displacement gas kick in horizontal well drilling into deep fractured gas reservoir

The risk of well control is high when displacement gas kick occurs in the deep fractured reservoir, and improper handling can easily lead to blowout, which will seriously affect the deep well drilling. Using Fluent software, a simulation model was constructed to depict the interaction of a horizontal well with vertical fractures. The displacement gas kick process was simulated in horizontal well under formation temperature and pressure conditions. An analysis was conducted to assess the impact of fracture width, quantity, as well as the viscosity and density of drilling fluid on the process of gas-liquid displacement. It further compared the effectiveness of three measures in counteracting displacement gas kick: applying back pressure at the wellhead, altering the viscosity and density of the drilling fluid. New findings suggest that the gas-liquid interface within the fracture exhibits a funnel-like shape, where the gas and liquid phases are layered in the annulus and manifest in a streak-like pattern. Fracture width, quantity, and drilling fluid density promote displacement, while drilling fluid viscosity inhibits the displacement. Different from vertical wells, in horizontal wells, displacement gas kick mainly appears in the underbalanced interval. The fracture width primarily determines the size of the displacement window, while the density and viscosity of the drilling fluid exert lesser influence. Horizontal wells are highly sensitive to variations in external conditions when it comes to displacement gas kick. Therefore, enhancing the wellhead back pressure is advisable to address the displacement gas kick in horizontal wells.

Sodium chloride crystallization in a model porous medium during drying with a receding sharp front

Visualization experiments in a model porous medium are presented in this work to study the interplay between salt precipitation and gas–liquid displacement during evaporation for the drying situation characterized by a receding sharp drying front. Various types of salt subflorescence are distinguished depending on the location of the subflorescence growth, namely, away from the drying front in the region predominantly occupied by gas or in the liquid-saturated region. A distinction is also made regarding the subflorescence that develops in the predominantly gaseous region depending on the degree of occupation of the pores by the subflorescence structure. The experiment confirms that the capillary liquid films can be a pathway for the dissolved salt transport. As a result of the capillary film effect, the evaporation front must be distinguished from the drying front and subflorescence structures can develop in the vicinity of the evaporation front away from the drying front. It is also shown that the pinning of the evaporation front leads to an anomalous drying front kinetics with a drying front position varying linearly with time and not according to the classical scaling with the square root of time.

Erratum: “Interplay between salt precipitation, corner liquid film flow, and gas-liquid displacement during evaporation in microfluidic pore networks” [J. Appl. Phys. 133, 074701 (2023)

Erratum: “Interplay between salt precipitation, corner liquid film flow, and gas-liquid displacement during evaporation in microfluidic pore networks” [J. Appl. Phys. 133, 074701 (2023)

Generation of microbubbles via a tapered capillary

We propose a novel method for efficient production of microbubbles based on a tapered capillary with an interiorly attached filament. When gas–liquid displacement driven by an input pressure occurs in the capillary, the gas cone ruptures close to the orifice of the capillary. The generated microbubbles can be pushed out of the capillary and collected by a liquid tank when the pressure is appropriately selected. A liquid column is employed in the straight part of the capillary, which can sustain the liquid film near the capillary orifice and hence the bubble generation by transporting liquid along the filament. Within the working pressure range, increasing the input air pressure leads to a decrease in the microbubble diameter. The minimum diameter of the microbubbles is approximately equal to the orifice diameter of the tapered capillary. In our experiments, microbubbles with a minimum diameter of 1.56 μm can be realized. Theoretically, we derive a one-dimensional unsteady lubrication equation describing the evolution of the gas–liquid interface in a tapered tube. The bubble pinch-off is justified by the numerical solution of the lubrication equation. In particular, the predicted bubble diameters are in agreement with the experimental measurements.

Axisymmetric gas–liquid displacement flow under a confined elastic slab

Axisymmetric gas–liquid displacement flow under a confined elastic slab

Automated Liquid-Liquid Displacement Porometry (LLDP) for the Non-Destructive Characterization of Ultrapure Water Purification Filtration Devices.

This scientific publication presents a novel modification of the liquid-liquid displacement porosimetry (LLDP) method, aiming for the non-destructive automated analysis of water purification membrane filtration devices in the microfiltration (MF) and ultrafiltration (UF) range. The technical adaptation of LLDP enables the direct in-line porosimetric analysis of commercial filtration devices, avoiding the filtration devices' destruction. Six commercially available filtration devices with polyethersulfone (PES) and polysulfone (PS) membranes were studied using an improved device developed by the IFTS, which was based on a commercial LLDP instrument. The filtration devices were evaluated in three different configurations: flat disks, hollow fibers, and pleated membranes. The results obtained using the proposed method were compared with other characterization techniques, including submicronic efficiency retention, image analysis of scanning electron microscopy (SEM), and gas-liquid displacement porosimetry (GLDP). The comparison of the results demonstrated that the proposed method accurately determined the porosimetric characteristics of the filters. It proved to be a precise technique for the non-destructive in-line evaluation of filter performance, as well as for periodic quality control and the fouling degree assessment of commercial filtration devices. This modified LLDP approach offers significant potential for the advanced characterization and quality assessment of water purification membrane filtration devices, contributing to improved understanding and optimization of their performance.

Dynamics of Compression-Driven Gas-Liquid Displacement in a Capillary Tube.

We study two-phase displacement via the steady compression of an air reservoir connected to an oil-filled capillary tube. Our experiments and modeling reveal complex displacement dynamics depending on compression rate and reservoir volume that, for large reservoirs, depend on a single dimensionless compressibility number. We identify two distinct displacement regimes, separated by a critical value of the compressibility number. While the subcritical regime exhibits quasisteady displacement after an initial transient, the supercritical regime exhibits burstlike expulsion.

Interplay between salt precipitation, corner liquid film flow, and gas–liquid displacement during evaporation in microfluidic pore networks

Visualization experiments with microfluidic pore networks are performed in this work to disclose interplay between salt precipitation, the corner liquid film flow, and gas–liquid displacement during evaporation. Two forms of salt precipitation are revealed: aggregated polycrystalline structures and large bulk crystals. It is found that gas bubbles can be formed because of imbibition of liquid into aggregated polycrystalline structures. The length of a corner liquid film can affect the direction of growth of the aggregated polycrystalline structures connected to the corner liquid film. Discontinuous corner liquid films can be transformed to continuous ones when they are touched by growing aggregated polycrystalline structures. The “sleeping” aggregated polycrystalline structures at the open surface of a microfluidic pore network, i.e., efflorescence, can grow again if they are touched by growing aggregated polycrystalline structures inside the microfluidic pore network, i.e., subflorescence. Because of efflorescence, the evaporation rate from a microfluidic pore network can increase first and then decrease. Moreover, a theoretical model is developed for the coupled transport of vapor diffusion in the gas zone and liquid flow as well as transport of dissolved salt in the corner liquid films in a capillary tube of square cross section so as to disclose the key parameters controlling the transport processes.

Numerical Simulation of Gas-Liquid Gravity Displacement in Vertical Fractures during Drilling of Carbonate Formations.

In petroleum drilling, carbonate formations characterized by natural fractures can result in troublesome gas-liquid gravity displacement, which refers to the phenomenon that the drilling mud leakage and gas kick are simultaneously triggered. This work focuses on clarifying the mechanism of gas-liquid displacement in vertical fractures during the drilling of carbonate formations and investigating the characteristics of gas-liquid displacement under various conditions. First, the bottom hole pressure allowing for gas-liquid gravity displacement is analyzed, which determines the coexistence condition of leakage and kick in vertical fractures. Then, a theoretical model of gas-liquid displacement flow in a vertical fracture is established. To verify the reliability and accuracy of the model, the results of numerical simulation are compared with those of a visualization experiment. The development process and flow characteristics of gas-liquid displacement in the fracture under different conditions are numerically simulated. The effects of pressure difference, drilling mud property, and fracture geometry on the gas-liquid displacement rate are analyzed. It is found that the drilling mud leakage rate increases with the increase of fracture width, fracture height, and drilling mud density, while it decreases with the increase of pressure difference and fracture length. The gas invasion rate increases with the increase of fracture width, fracture height, and pressure difference, while it decreases with the increase of drilling mud density and fracture length. The equations for leakage rate and gas invasion rate are derived by the response surface method, and the methods for mitigating gas-liquid gravity displacement are discussed. It is expected that the present work provides a better understanding of the gas-liquid gravity displacement in carbonate formations.

ASSESSMENT OF THE PORE DIAMETER MEASURED IN GAS-LIQUID DISPLACEMENT POROMETRY: EFFECT OF THE CAPILLARY CONSTANT

ASSESSMENT OF THE PORE DIAMETER MEASURED IN GAS-LIQUID DISPLACEMENT POROMETRY: EFFECT OF THE CAPILLARY CONSTANT

Study on Gas Invasion Behavior of Gas–Liquid Displacement in Fractured Reservoirs

When drilling or exploiting fractured formations, gas fluid displacement and invasion often occur, and gas invasion is very subtle and difficult to find. The gas in the fracture enters the wellbore and arrives near the wellhead with the drilling fluid. Improper treatment may lead to serious accidents such as lost circulation and blowout. In this study, using computational fluid dynamics (CFD) simulation software for modeling and grid generation, based on the volume of fluid (VOF) method, the gas invasion behavior under different conditions was simulated to explore the flow process and characteristics of gas invasion, and the effects of different drilling fluid properties and fracture morphology on gas invasion were analyzed. The experimental results show that the drilling fluid enters the fracture to compress the gas, making the pressure in the fracture greater than that in the wellbore, thus leading to the occurrence of gas invasion. The viscosity and density of the drilling fluid have different effects on the gas invasion process. The higher the viscosity, the smaller the possibility of gas invasion. However, when the viscosity of the drilling fluid gradually increases from 10–50 MPa·s, the change of gas invasion rate is small, all within 1.0–1.2 m/s. The higher the density, the more conducive to the occurrence of gas invasion. The inlet pressure has no obvious effect on the occurrence of gas invasion, and the occurrence time of the gas invasion fluctuates in 0.35 s at 0.5–2.5 MPa. With the increase in the fracture width and length, the possibility of gas invasion decreases, but there is an extreme value for the fracture height. The time of gas invasion does not change beyond this extreme value. When the fracture height is 100–700 mm, the time of gas invasion increases with the increase in the height; when the height is 700–900 mm, the gas invasion time does not change. These results provide a practical and effective method for enhancing oil recovery, preventing and treating gas invasion in gas–liquid flooding.

Hydrodynamics of gas-liquid displacement in porous media: Fingering pattern evolution at the breakthrough moment and the stable state

Gas-liquid displacement in porous media widely exists in many terrestrial/extraterrestrial subsurface resource extraction and utilization applications. The typical fingering displacement during gas invading has been well identified through extensive research efforts. Yet, the evolution of fingering structures after invading breakthrough is rarely reported. Herein, through a joint approach of experimental flow imaging and digital image processing, we investigated the gas-liquid fingering displacement in a porous-patterned microfluidic chip from the breakthrough moment until reaching the steady state. With a wide range of capillary number Ca and viscosity ratio M, we visualized the evolution of finger morphologies in different flow regimes including capillary fingering (CF), viscous fingering (VF), and crossover zone (CZ). Interestingly, we found that finger structures of CF regime remain the same after the breakthrough, whereas fingers of VF regime keep expanding until almost all the pore space is invaded and eventually reaches to steady state. Followed with experimental observations, a comparative quantification of fingering patterns was also conducted in terms of invasion velocity, phase saturation and fractal dimension. A dramatic increase of gas saturation, from 0.15 to 0.60 at the case of Log10Ca=-5.17 and Log10M=-2.78, is obtained in the VF regime when the steady state is reached, so is the fractal dimension (from 0.14 to 0.16, even higher than one of CF). The underlying mechanism of such fingering expansion in VF is further revealed from the time evolution of fingering after breakthrough. A previously unobserved fingering cycle, consisting of new finger forming, cap invading, breakthrough and finger vanishing, keeps repeating until the saturation reaches the maximum. We believe that these findings are of significance in evaluating extraction effectiveness, economic benefits and storage safety for subsurface applications.

Characterization of Commercial Gas Diffusion Layers (GDL) by Liquid Extrusion Porometry (LEP) and Gas Liquid Displacement Porometry (GLDP).

This works aims to study the porous characterization of several commercial Gas Diffusion Layers (GDL). Three carbon-based porous GDL featuring a highly rigid microstructure of interconnected pores of several manufacturers were analyzed. Gas Liquid Displacement Porometry (GLDP) and Liquid Extrusion Porometry (LEP) have been used to obtain their pore size distributions (PSD) and the mean and mode pore diameters (davg and dmod), by means of a gas/liquid and extrusion porometer developed at IFTS. N-dodecane liquid has been used to completely wet the GDL’s assuring penetration of the liquid into the carbon fibrous structure. The results demonstrated the accuracy of the setup on characterizing GDL in the Particle Filtration (PF) range by GLDP and LEP, with reasonable agreements of resulting PSD and average sizes between both techniques when GLDP and LEP results are compared. Differences can be explained in terms of the high pore connectivity of these kinds of structures.

Non-Destructive Characterization of Industrial Membrane Cartridges by Using Liquid-Liquid Displacement Porosimetry (LLDP).

This works aims to propose and demonstrate the accuracy of a novel method of characterization aimed for non-destructive analysis of microfiltration (MF) membrane cartridges. The method adapts conventional liquid–liquid displacement porosimetry (LLDP) for performing an in-line porosimetric analysis of the membrane cartridges, getting their pore size distributions (PSDs) and mean pore diameters (davg). Six commercial filtration cartridges featuring polyethersulfone (PES) pleated membranes were analyzed using a newly designed filtration rig, based on the liquid–liquid displacement porometer, developed at the Institut de la Filtration et des Techniques Séparatives (IFTS) and operated at constant flow. The experimental rig allows the direct and non-destructive characterization of the cartridge in its original presentation. Results have been compared with those obtained by using gas–liquid displacement porosimetry (GLDP) on small membrane coupons detached from such cartridges. The comparison allows us to conclude that the proposed method gives enough accuracy in the determination of porosimetric characteristics of the filters. This method can be used as a precise characterization technique for a non-destructive in-line study of filter performance and can be envisaged as useful to periodic quality or fouling control of the commercial cartridges.

Capillary instability induced gas-liquid displacement in porous media: Experimental observation and pore network model

We show that during evaporation of a pore network, liquid can refill the gas occupied pores, snapping off a gas bubble, which then moves to a stable configuration. This phenomenon is induced by the capillary instability due to the wettability heterogeneity of the pore network and has a much smaller time scale as compared to the evaporation process. The capillary instability induced liquid refilling and bubble movement are explained in detail based on the analysis of the images obtained from the visualization experiment. The capillary valve effect, which hinders the movement of the gas-liquid interface and is induced by the sudden geometrical expansion between small and large pores, can be suppressed by the residual liquid in the large pore. For better understanding of the capillary instability induced gas-liquid two-phase transport during evaporation, a novel pore network model is developed, which considers not only the capillary and viscous forces but also the inertial forces that are seldom taken into account in the previous models. The pore network modeling results are in good agreement with the experimental data, demonstrating the effectiveness of the developed pore network model, which opens up a new route for better understanding of the role of inertial forces in two-phase transport in porous media.

Mixed Poiseuille-Knudsen flow model for Gas Liquid Displacement porometry data treatment

A comprehensive methodology has been developed for treating Gas Liquid Displacement (GLD) porometry data with a flow model called Weber model (WM) describing mixed Poiseuille-Knudsen flow regime. The model has been applied in two options: i) considering that the gas viscosity in porometry experiments is the same as that available in reference books for Poiseuille flow regime and ii) equating the expression for Darcy coefficient in gas flow to that obtained in additional liquid permeability experiments and thus leaving the gas viscosity to be an adaptable parameter. In the analysis of GLD porometry data for a range of different microfiltration membranes, it is found that with the WM in both options identical relative pore-number distribution is estimated; and this distribution satisfactorily reproduces both dry and wet flow data from the GLD experiments. The absolute pore-number distributions obtained by the two options are quite similar, but differ in the absolute value of the pore numbers. The pore-number distribution obtained by the second option describes the liquid permeability well, while the first option fails. The WM as a method of GLD porometry data treatment is quite similar to the earlier introduced variable viscosity Poiseuille model (VVPM), and the variable viscosity from the latter model appears to be a combined effect of an uncertainty about actual gas viscosity and the contribution of Knudsen flow. It is concluded that a standard test method for determining pore-size distribution by GLD porometry must include prediction or description of liquid permeability of the membrane. Then, any acceptable gas flow model with adjusted Darcy coefficient obtained from liquid permeability experiment will be suitable for advanced GLD porometry data treatment, beyond the methods typically implemented in gas flow-based porometers, currently used in academia and industry.

Gold nanoparticle mixture retention test with single particle detection: A fast and sensitive probe for functional pore sizes of ultrafiltration membranes

Ultrafiltration is often one of the most critical steps in the production of high-purity water, chemicals and biopharmaceutical products. Pore size characterization in ultrafiltration membranes is an important yet challenging task. This work presents a long sought-after solution to measure ultrafiltration membrane pore size in a fast, sensitive and reliable way. Ultrafiltration membranes made of different polymeric materials were challenged with a mixture of 20, 30, 40 and 60 nm gold particles, at a concentration of approximately 7 × 107 particles/mL for each nominal size or 2, 8, 19, 66 μg/L gold, respectively, to determine the filtration performance over a wide size range. The low particle loading in the feed suspension resembles the environment where these membranes are practically used, for example, in ultrapure water. In the retention test both sizes and counts of gold nanoparticles (GNPs) were quantitatively measured in feed and permeate suspensions by single particle inductively coupled plasma mass spectrometry (spICP-MS). The GNP retention by membrane adsorption was minimized by adding anionic surfactant sodium dodecyl sulfate (SDS) in the feed suspension. As a result, the cut-off size of fully retained particles was in good agreement with the membranes' functional pore sizes or bubble point sizes measured by gas-liquid displacement porosimetry. The retention test showed that two tightest membranes out of the five tested ones reached full retention of particles between 40 and 60 nm in diameter. This study revealed significant discrepancies between the functional pore sizes and the manufacturers’ removal ratings. It was demonstrated that spICP-MS quantitatively and reliably measures 20 nm GNPs in permeate suspensions at concentrations as low as 50 particles/mL, equivalent to 0.003 ng/L. This is over three orders of magnitude lower than GNP limit of quantification (LOQ) by traditional ICP-MS analysis, over five orders of magnitude lower than the LOQ by liquid nanoparticle sizer (LNS), or over eight orders of magnitude lower than the LOQ of dextran by refractive index measurement. Unlike light-based particle techniques, spICP-MS is highly selective and element specific for gold, so dissolved gas or other particulates like degradants of polymeric membranes do not interfere with the analysis. The filtration part of the retention test was more straightforward and faster since no pre-test rinsing was required. The size-resolved particle retention data for every 1 nm size bin made it practical to probe an unknown sample over a wide range of pore sizes.

Microfiltration membrane characterization by gas-liquid displacement porometry: Matching experimental pore number distribution with liquid permeability and bulk porosity

The variable viscosity Poiseuille model (VVPM), developed recently to treat gas-liquid displacement (GLD) porometry data for track-etched polyethylene terephthalate (PET) membranes, is applied to polyethersulfone (PES) and polypropylene (PP) microfiltration membranes prepared by phase inversion. It is found that in general aspects the pore size distribution as estimated by the model, with the intrinsic assumption of isolated capillary pores, perfectly reproduces wet and dry fluxes during porometry measurements, but the estimated porosity appeared to be much higher than unity. To eliminate the discrepancy, two additional parameters, namely non-uniformity and tortuosity coefficient, have been introduced in the flux and porosity estimating equations. The apparent viscosity of the gas in porometry analysis is found to be several fold higher than that available in literature, and also the viscosity range appeared to be membrane type dependent. The pore size distribution curve shifts along the diameter axis depending on the gas flow direction applied in porometry data acquisition. However, because the membranes had narrow pore size disribution, the estimated parameters had been averaged within acceptable confidence range. With the inclusion of non-uniformity and tortuosity of the capillaries, the revised version of the VVPM made an advancement in porometry data analysis of membranes with both isolated and interconnected pore structure; it characterizes the assumed model capillaries in terms of Young-Laplace pore diameter, but also non-uniformity and tortuosity of pores. The procedure for data treatment has been illustrated in detail and the method could easily be adapted to gas-liquid displacement porometer software system for regular data treatment. Based on a set of readily available experimental data, including the typical output from standard GLD porometry, the here established extended version of the VVPM allows the step-by-step determination of all the parameters which characterize the pore structure of the membranes. Also the absolute pore number density distributions can be obtained, including estimates of additional pore characteristics such as non-uniformity and tortuosity.

On the accuracy of capillary flow porometry for fibrous filter media

Abstract The application of capillary flow porometry by gas-liquid displacement to the measurement of the pore size distribution in identical glass microfiber filter media can lead to surprisingly divergent results. The causes for these differences as well as the factors that influence the over-all reliability of data obtained by this widely used technique are investigated. Among the key factors studied were the volatility and viscosity of four common wetting liquids, the scan rate (i.e. the holding time between increments of differential pressure Δp or volumetric flowrate V ), and the scan sequence (i.e. dry before wet, or wet before dry scan). Most measurements were made with a porometer designed in house, in order to have complete control over all aspects of operation. Data obtained with commercial porometers are also reported. For best comparability, all measurements were made with the same batch of standard glass microfiber media. The largest error source by far was the volatility of fluorinated compounds commonly used as wetting liquids. While the vapor pressures of such compounds may be relatively low, their use in combination with a flow of air through the porous matrix can have an enormous effect on the evaporation rate during a scan. Neglecting this effect (which obviously depends on the scan rate) may ultimately result in an error of almost arbitrary magnitude in the pore size distribution. Silicone oil on the other hand has a negligible volatility and provides reliable results for a wide range of operating conditions. The liquid viscosity in the tested range of 5–100 mm2/s played a comparatively insignificant role. These and other factors of uncertainty are discussed on the basis of experimental data.