Permeability Measurement Techniques Research Articles

A pulse-decay method for low (matrix) permeability analyses of granular rock media

Abstract. Nanodarcy level permeability measurements of porous media, such as nano-porous mudrocks, are frequently conducted with gas invasion methods into granular-sized samples with short diffusion lengths and thereby reduced experimental duration; however, these methods lack rigorous solutions and standardized experimental procedures. For the first time, we resolve this by providing an integrated technique (termed gas permeability technique, GPT) with coupled theoretical development, experimental procedures, and data interpretation workflow. Three exact mathematical solutions for transient and slightly compressible spherical flow, along with their asymptotic solutions, are developed for early- and late-time responses. Critically, one late-time solution is for an ultra-small gas-invadable volume, important for a wide range of practical usages. Developed to be applicable to different sample characteristics (permeability, porosity, and mass) in relation to the storage capacity of experimental systems, these three solutions are evaluated from essential considerations of error difference between exact and approximate solutions, optimal experimental conditions, and experimental demonstration of mudrocks and molecular-sieve samples. Moreover, a practical workflow of solution selection and data reduction to determine permeability is presented by considering samples with different permeability and porosity under various granular sizes. Overall, this work establishes a rigorous, theory-based, rapid, and versatile gas permeability measurement technique for tight media at sub-nanodarcy levels.

A Review on Measurement Techniques of Deformation‐Induced Transformation Kinetics in Transformation‐Induced Plasticity and Transformation‐Induced Plasticity‐Assisted Steels

Deformation‐induced austenite‐to‐martensite transformation is an important phenomenon that controls the flow behavior of transformation‐induced‐plasticity (TRIP) and TRIP‐assisted steels. Transformation kinetics and triggering strain are important parameters that need to be known during transformation. Both these parameters can be correctly determined by an accurate quantitative assessment of the austenite during deformation. Herein, both in situ and ex situ measurement techniques used for quantitative assessment of austenite during/after tensile deformation of the TRIP and TRIP‐assisted steels are reviewed. A comparison of various techniques such as X‐ray diffraction, neutron diffraction, Mossbauer spectroscopy, and DC/AC magnetic permeability is presented. Due to limited penetration power of the radiations, difficult access, and difficulty in setting up the measurement facility for the in situ measurements, X‐ray diffraction, neutron diffraction, and Mossbauer spectroscopy techniques do not yield accurate quantitative results and are time‐consuming. It is envisaged that an accurate quantitative assessment of austenite from the bulk of TRIP and TRIP‐assisted steel specimens is possible with magnetic permeability measurement techniques. Real‐time quantitative assessments can be made by measuring changes in the magnetic permeability due to changes in the ferromagnetic content during deformation. magnetic permeability measurements require extensive calibration for the accurate measurement of the phases during deformation of the steel.

Micro Computed Tomography based stochastic design and flow analysis of dry fiber preforms manufactured by automated fiber placement

The effective design of channels in dry tape preforms is crucial for achieving desired preform permeability for successful resin injection for composites manufacturing using Automated Fiber Placement (AFP) process. Achieving target gaps and their locations in the AFP layup is extremely challenging. This work investigates the correlation between the spatial variability of the preforms and the in-plane permeability using an X-ray Computed Tomography (XCT) based characterization framework. The tomographic images of two different dry carbon tape preforms with different tape widths were used to generate realistic and XCT based stochastic models to be used for numerical permeability predictions. The variability in the tape placement by the robotic head and its effect on preform permeability was also examined through stochastic geometric modeling of the laid preform. A benchmark transient permeability measurement set-up was utilized to obtain experimental in-plane preform permeability through 2D radial mold filling. The in-plane numerical permeability values showed significant scatter, with a coefficient of variance of 75%–130%, which deviated from the experimental measurements by approximately one order of magnitude. These findings strongly re-affirm that the experimental permeability measurement technique based on transient mold filling of dry fiber AFP preforms is complex however, the XCT based stochastic modeling technique is an effective way to estimate the permeability of dry fiber AFP preforms virtually.

A novel, fast and clean 3D permeability measurement method for multi-layer textiles and fabrics

Permeability quantifies flow conductance of textile reinforcements, is required for process simulations, and can be used for a range of materials and process monitoring by industry. Current permeability measurement techniques are destructive, either because a liquid penetrates the sample or the sample must be cut from products to a specific size. A non-destructive measurement concept is introduced based on air flow established between flat circular patterns containing flow rate and pressure sensors. The presented experimental studies show that from flow rate and pressure distribution data, the technique clearly distinguishes changes in volume fraction and layup while being applicable to a range of woven and non-crimp textiles. The concept interprets permeability from a neural network trained using a large set of air flow simulations. A preliminary set of 250,000 simulated cases was applied to train seven different neural network types. Limited predictive accuracy has been achieved, utilizing a CGB neural net structure.

Characterization of the average pore diameter of nanoporous media by gas permeability measurement technique in transitional flow regime

In this paper, a gas permeability measurement technique in transitional flow regime was proposed, which could characterize the average pore diameter of nanoporous media non-destructively. With high purity argon and carbon dioxide, the conductance of three groups of porous anodic alumina was tested respectively in the transitional flow regime by the dynamic differential pressure attenuation test system, and the average pore diameter of porous anodic alumina was derived. The average pore diameters obtained through the gas permeability measurement technique are consistent with the SEM image analysis results, and the relative error is less than 8%. This method based on the improved transitional flow conductance theory extends the pore-size range of gas permeability measurement technique from micrometer to the nanometer scale, and does not require high pressure or high vacuum. It has the advantages of non-destruction, high-accuracy and large-area-measurement, which brings significant practical application value.

Transverse permeability measurements of gas shales under replicated in-situ flow conditions: Mathematical modeling and laboratory testing

Fast and accurate characterization of unconventional gas reservoirs is of great significance for estimation of gas-in-place and enhancement of gas recovery; however, it remains a big challenge to efficiently and effectively determine the permeability of tight-structure reservoirs in the nano-Darcy scale, especially for those reservoirs with strong gas sorption potential. A novel pressure transient technique is proposed to replicate the in-situ gas flow behavior, and thus to reduce the permeability errors from gas compressive storage, gas sorption, and gas compressibility, which are the three primary error sources widely existing in various permeability measurement techniques. The feasibility of the technique is firstly verified via numerical solutions of a partial differential equation (PDE) model established to closely represent the proposed technique. The results of the numerical study showed that the effects of the error sources on the measured permeability can be minimized and meanwhile, high accuracy and efficiency can be achieved in comparison with the conventional method. A specially designed apparatus for experimental tests via the proposed technique is then used to investigate the stress-dependent permeability of gas shales. The consistency of the experimental results with the findings from the numerical study further validates the applicability of the technique. Considering the complexity of the analytical solution of the PDE model for experimental data interpretation, shale permeability is computed via a new data interpretation approach which is developed by combining the curve-matching and the finite difference method. The experimental results showed that shale permeability is strongly dependent upon the applied stresses and easily affected by gas sorption, gas compressibility and stress inhomogeneity. Without consideration of these factors, the permeability error can reach up to 28.1 % at low stresses. The proposed technique provides a great tool to get insights into the in-situ gas flow behavior and characterize tight-structure gas reservoirs.

Gas permeability in rarefied flow conditions for characterization of mineral membrane support

Abstract Gas Permeability Measurement Technique (GPMT) has the advantage of being a non-destructive method, which is efficient in characterizing filtration membranes. Ceramic filtration membranes consist of successive layers of micro (support) to nano size (skin) pores. When gas flows through such a small scale structure, the molecular mean free path becomes comparable to the pore size. The Slip flow model, validated to describe the gas transport properties under rarefied flow conditions in a microchannel, is extended to porous media. The porous structure is modeled as a cluster of several identical cylindrical channels. By measuring the pressure drop Δ P at several different mean pressures, the pore radius and the porosity on square tortuosity ratio ϵ ∕ τ 2 of the porous model structure that have the same flow property were estimated.

Studies on test technique of stress concentration for ferromagnetic component based on permeability

The stress concentration detection technology based on the permeability is an evaluating method on the stress concentration which is according to the induction voltage signal of the closed magnetic circuit composed of the probe and the specimen. The permeability is related to the detection signal, but also to the degree of stress concentration. Through the permeability parameter, the relation between the detection signal and the degree of stress concentration can be established. The permeability measurement technique can be used to detect various micro-structural changes of component related to permeability, such as stress concentration, fatigue damage, aging and transformation. The basic principle of permeability measurement technology is analyzed, and the optimum setting method of detection parameters is discussed. Taking steel 20 as an example, the relationships between the detected signal and the tensile stress, tensile residual stresses have been studied experimentally which is based on the measured signals data. It is found that the change of detection signal caused by tensile stress can reach 33.3%, and the change of detection signal caused by residual stress after unloading can reach 35.8%. It is also found that the detection signal is particularly sensitive to the yield strength, and the signal will decrease sharply when the stress exceeds the yield strength. According to the characteristics of the detected signal, it can effectively detect the stress state in a certain area of the specimen, and has a broad application prospect.

Permeability Evolution in Sandstone Due to CO2 Injection

Permeability variation is one of the key factors influencing the injectivity of CO2 in CO2 sequestration projects. Despite the research carried out on the subject, the results are highly inconsistent. In this study, the injection of brine (5 wt % NaCl + 1 wt % KCl), CO2-saturated (live) brine, and supercritical CO2 was performed on three homogeneous Berea sandstone plugs with a low clay content and two Bandera Gray sandstone plugs with a high clay content at reservoir conditions (10 MPa and 323 K). Porosity and permeability of the samples were measured using nuclear magnetic resonance (T2 relaxation time), and a dynamic (during flooding) permeability measurement technique, respectively, at different injection rates and injection durations. The mercury intrusion test was also performed on each sample to further evaluate its pore throat size distributions. From the results of this study, it was revealed that the CO2 injection rate is unlikely to affect the permeability significantly. It was also shown that ...

Evaluation of Various Pulse-Decay Laboratory Permeability Measurement Techniques for Highly Stressed Coals

The transient technique for laboratory permeability measurement, proposed by Brace et al. (J Geophys Res 73:2225–2236, 1968) and widely used for conventional gas reservoir rocks, is the preferred method when testing low-permeability rocks in the laboratory. However, Brace et al.’s solution leads to considerable errors since it does not take into account compressive storage and sorption effect when applied to sorptive rocks, such as, coals and shales. To verify the applicability of this solution when used to characterize fluid flow behavior of coal, an in-depth investigation of permeability evolution for flow of helium and methane depletion was conducted for San Juan coals using the pressure pulse-decay method under best replicated in situ conditions. Three permeability solutions, Brace et al.’s (1968), Dicker and Smits’s (International meeting on petroleum engineering, Society of Petroleum Engineers, 1988) and Cui et al.’s (Geofluids 9:208–223, 2009), were utilized to establish the permeability trends. Both helium and methane permeability results exhibited very small difference between the Brace et al.’s solution and Dicker and Smits’s solution, indicating that the effect of compressive storage is negligible. However, methane permeability enhancement at low pressures due to coal matrix shrinkage resulting from gas desorption can be significant and this was observed in pressure response plots and the estimated permeability values using Cui et al.’s solution only. Therefore, it is recommended that Cui et al.’s solution be employed to correctly include the sorption effect when testing coal permeability using the transient technique. A series of experiments were also carried out to establish the stress-dependent permeability trend under constant effective stress condition, and then quantify the sole contribution of the sorption effect on permeability variation. By comparison with the laboratory data obtained under in situ stress/strain condition, it was verified that accelerated CBM production can be achieved by reducing the horizontal stresses.

Blended polybenzimidazole and melamine-co-formaldehyde thermosets

Polybenzimidazole [PBI; poly-2,2′(m-phenylene)-5,5′-bibenzimidazole] is known to have excellent high temperature stability (up to 450°C) and superb H2/CO2 selectivity compared to most high performance (HP) polymers. New blended thermosets were made with PBI and poly(melamine co-formaldehyde) [PMF] to produce stable thin-films after thermal processing at 220–250°C. PBI film formation is difficult, because of challenging processing techniques. As a result, the film tends to fracture and fissure due to processing aids and stabilizers (salt/acid additives) that are found in PBI solutions above 10wt%. Therefore, PBI dense thin-films are fragile and prone to fracturing during film processing. The reported PBI-PMF blended thermosets do not have stabilizers, and can be made into dense thin-films. The PBI-PMF films were analyzed using pure and mixed gas permeability measurement techniques. At 250°C, the data show H2/CO2 gas selectivities greater than 13. Also from the gas permeation data, the energy of activation (Ep) of a mixed gas stream for PBI-PMF shows that hydrogen permeates more easily than the other gases, while the permeabilities for the larger kinetic diameter gases are greatly diminished. In addition, the FT-IR spectra show that the PBI-PMF films have changed from parent PBI after thermal processing, and PMF dominates the spectra even in minor percent compositions. Overall, the reported PBI-PMF thermoset films show good stability which can be used for high temperature gas separation.

Continuous measurement of fiber reinforcement permeability in the thickness direction: Experimental technique and validation

It is an important topic to measure the through-thickness permeability of fiber reinforcements as the resin flow in the thickness direction is widely employed in many composites manufacturing techniques. Continuous techniques for the permeability measurement by simultaneous fabric compaction and liquid flow have been recently proposed as an alternative way to the tedious and laborious conventional permeability measurement techniques. In spite of their efficiencies, these continuous techniques have some limits if the fabric compaction speed or flow rate is relatively great. To address this issue, a new equation for the permeability estimation is proposed. Parametric studies are performed to investigate the influences of the experimental conditions on the validity of the continuous technique. A dimensionless number is proposed as a measure of the relative error of the continuous technique.

Temperature dependence dynamical permeability characterization of magnetic thin film using near-field microwave microscopy

A temperature dependence characterization system of microwave permeability of magnetic thin film up to 5 GHz in the temperature range from room temperature up to 423 K is designed and fabricated as a prototype measurement fixture. It is based on the near field microwave microscopy technique (NFMM). The scaling coefficient of the fixture can be determined by (i) calibrating the NFMM with a standard sample whose permeability is known; (ii) by calibrating the NFMM with an established dynamic permeability measurement technique such as shorted microstrip transmission line perturbation method; (iii) adjusting the real part of the complex permeability at low frequency to fit the value of initial permeability. The algorithms for calculating the complex permeability of magnetic thin films are analyzed. A 100 nm thick FeTaN thin film deposited on Si substrate by sputtering method is characterized using the fixture. The room temperature permeability results of the FeTaN film agree well with results obtained from the established short-circuited microstrip perturbation method. Temperature dependence permeability results fit well with the Landau-Lifshitz-Gilbert equation. The temperature dependence of the static magnetic anisotropy H(K)(sta), the dynamic magnetic anisotropy H(K)(dyn), the rotational anisotropy H(rot), together with the effective damping coefficient α(eff), ferromagnetic resonance f(FMR), and frequency linewidth Δf of the thin film are investigated. These temperature dependent magnetic properties of the magnetic thin film are important to the high frequency applications of magnetic devices at high temperatures.

Unidirectional compression of fibre reinforcements. Part 2: A continuous permeability tensor measurement

Modelling LCM processes, where resin flow and compression of the fibre reinforcements are involved, requires a proper modelling of the fibre reinforcements behaviour in compression and to define how the permeability tensor evolves. The permeability measurement techniques based on fluid injection lead to data scattering. Using a material testing machine, unidirectional compression tests are performed on impregnated fibre reinforcements to induce in-plane and through-thickness fluid flows. With proper viscosities and compression speeds, the expelled-fluid pressure becomes sufficiently high to be measured. Then, using that fluid pressure and following a methodology based on numerical optimizations, the in-plane equivalent permeability and through-thickness permeabilities can be extracted. An additional measurement is needed to know the anisotropy ratio and calculate the two in-plane principal permeabilities. Due to the nature of the compression test, a major advantage of the present method is that it is continuous with respect to fibre volume fraction and that it limits errors involved with injection techniques. Samples can previously be sheared before compression and permeability measurements.

Soft magnetic materials application in the RF range

Recent rapid progress of information technologies has enlarged the application fields of soft magnetic materials operating in GHz range. Firstly, this paper reviews the recent achievement of magnetic thin films applied in high-frequency devices. Then, a newly developed permeability measurement technique is introduced, and then ferromagnetic RF integrated inductors and noise suppressors are discussed from an application viewpoint. In particular, the influences of alignment between the patterned magnetic films and coil legs on the characteristics of inductors are manifested. As a result, a quality factor of 13 in a “shift type” inductor at 1.2 GHz was achieved.

A field permeability measurement technique using a conventional self-boring pressuremeter

A new permeability measurement method using a conventional self-boring pressuremeter (SBP) is described. The SBP self-bores to a predetermined depth. It is then retracted a short way, leaving a well-defined cavity in the ground. Water is pumped into the cavity at a constant rate, and the permeability is derived from the change in injection pressure with injection flow rate. A sequence of tests at a given horizon involves cavities of varying lengths, including a flush bottom or zero length cavity. In homogeneous materials the data from variable cavity lengths can be used to determine the anisotropy ratio. In heterogeneous materials the same data may allow the scale dependence to be evaluated if the anisotropy ratio can be independently obtained. Potential measurement errors are discussed in relation to smearing, temperature effects and leakage along the instrument. Results from Gault clay, London clay and Bothkennar clay are presented, with corroborating laboratory and other field test results where available. The preliminary assessment of scale dependence at these sites corresponds well to the degree of heterogeneity identified for the tested clays through visual observation.

In situ measurement and monitoring of whole-field permeability profile of fiber preform for liquid composite molding processes

Abstract For liquid composite molding (LCM) processes, such as resin transfer molding (RTM), the quality of final parts is heavily dependent on the uniformity of the fiber preform. However, the conventional permeability measurement method, which uses liquid (oil or resin) as its working fluid, only measures the average preform permeability in an off-line mode. This method cannot be used to create an in situ permeability profile because of fiber pollution. Further, the conventional method cannot be used to reveal preform's local permeability variations. This paper introduces a new permeability characterization method that uses gas flow to detect and measure preform permeability variations in a closed mold assembly before resin injection. This method is based upon two research findings: (1) resin permeability is highly correlated with air permeability for the same fiber preform with well-controlled gas flow, and (2) the whole-field air permeability profile of a preform can be obtained through measuring the pressure field of gas flow. In this study, first the validity of the gas-assisted, in situ permeability measurement technique was established. Then the technique was demonstrated as effective by qualitatively detecting non-uniformities and permeability variations in fiber performs. Finally, a two-dimensional flow model, based on the finite difference scheme, was developed to quantitatively estimate the whole-field preform permeability profile using predetermined pressure distribution. The efficacy of the new method was illustrated through experimental results.

Compression flow permeability measurement: a continuous technique

Existing permeability measurement techniques are based upon pressure driven flow through fibrous reinforcing materials. An innovative method is presented here utilising compression driven flow, which allows for continuous measurement of permeability over wide fibre volume fraction ranges, in a single efficient test. The initial study has been limited to isotropic reinforcements, obtained permeability data being compared with values measured using a more conventional method. Data has been collected from two styles of random mat, volume fraction varied from 20 to 50% in each test. Comparison between the two methods is very promising, validating further study and extension of this new technique. Larger errors have been noted at higher volume fractions, this effect being related to increasing mold clamping forces, and a subsequent translational deflection of the upper platen.

Permeability Characterization of Different Architectural Fabrics

The transient permeabilities and steady-state permeabilities of five different architectural glass fabrics were measured using one-dimensional experiments. The fabric architectures include 3-dimensional structure, random distributed fiber mat with stitches and knitted fabrics. The influence of the test liquids on the permeability measurements was investigated us3ing corn syrup, vinyl ester resin and epoxy resin. The experimental results show that the influence of the test liquids on permeability measurement is small if the simulated test fluids are properly selected. The relationship between permeability and porosity was also investigated. The experimental results indicate that the relationship between permeability and porosity can be expressed as an approximated exponential function. The permeability decreases dramatically as the porosity is reduced to about 0.65. The transient permeability of all fabrics used in the experiments exhibits the characteristic that it increases as the flow front moves forward under the experimental conditions, but the evolution is different. It reflects the influences of the fabric architecture on fabric permeability. The experimental results also point out that reproducible results can be obtained using one-dimensional permeability measurement technique provided that the fiber reinforcements are prepared very carefully and the edge effects are minimized.

Surface permeameter for nondestructive measurement of the rf complex permeability spectra of thin surface coatings

Thin film permeability measurement techniques such as stripline cavities or conventional permeameters require the sample undergoing measurement to be inserted within a fixture; typically, these samples can be no larger than a few square inches. However, certain applications require knowledge of the complex permeability of a coating or film applied to a finished, large product such as films deposited onto a continuous web for use as identification markers, the inside of a computer case for the control of EMI, or a ship mast for reduction of radar reflections. Therefore, a surface permeameter is presented that measures the rf complex permeability spectra of continuous films or coatings that are placed adjacent to the fixture over the frequency range of 10–500 MHz.