Accurate Permeability Measurements Research Articles

Effects of Centrifugal Force on Performance of Heat Pipe

The effects of rotation (centrifugal force) and inclination on the performance of a 6.0-mm-diameter heat pipe are experimentally examined. Both static and dynamic tests are performed. The capillary structure is sintered copper powder, and the fluid is deionized water. The static test ranges from 1.0 to , and the thermal resistance and maximum heat transfer rate are affected by the inclination angle. The dynamic test spans from 1.75 to . The maximum value of gravity is provided by the centrifugal force generated by a rotating platform. The test results indicate no appreciable difference amid static and dynamic tests when the centrifugal force is below . The departure starts to increase for a further increase of centrifugal force. For static operation, the existing correlation can reasonably predict the maximum heat transfer rate of the heat pipe under various inclination angles. Still, they cannot provide a good prediction when the maximum value of gravity of the dynamic test exceeds . By considering the second-order effect of the Darcy equation and combining with the accurate measurement of permeability of the pre-Darcy flow of the sintered structure. The prediction after correcting the modified correlation can predict the dynamic test results well.

A Model for the Apparent Gas Permeability of Shale Matrix Organic Nanopore Considering Multiple Physical Phenomena

The flow of shale gas in nano scale pores is affected by multiple physical phenomena. At present, the influence of multiple physical phenomena on the transport mechanism of gas in nano-pores is not clear, and a unified mathematical model to describe these multiple physical phenomena is still not available. In this paper, an apparent permeability model was established, after comprehensively considering three gas flow mechanisms in shale matrix organic pores, including viscous slippage Flow, Knudsen diffusion and surface diffusion of adsorbed gas, and real gas effect and confinement effect, and at the same time considering the effects of matrix shrinkage, stress sensitivity, adsorption layer thinning, confinement effect and real gas effect on pore radius. The contribution of three flow mechanisms to apparent permeability under different pore pressure and pore size is analyzed. The effects of adsorption layer thinning, stress sensitivity, matrix shrinkage effect, real gas effect and confinement effect on apparent permeability were also systematically analyzed. The results show that the apparent permeability first decreases and then increases with the decrease of pore pressure. With the decrease of pore pressure, matrix shrinkage, Knudsen diffusion, slippage effect and surface diffusion effect increase gradually. These four effects will not only make up for the permeability loss caused by stress sensitivity and adsorption layer, but also significantly increase the permeability. With the decrease of pore radius, the contribution of slippage flow decreases, and the contributions of Knudsen diffusion and surface diffusion increase gradually. With the decrease of pore radius and the increase of pore pressure, the influence of real gas effect and confinement effect on permeability increases significantly. Considering real gas and confinement effect, the apparent permeability of pores with radius of 5 nm is increased by 13.2%, and the apparent permeability of pores with radius of 1 nm is increased by 61.3%. The apparent permeability model obtained in this paper can provide a theoretical basis for more accurate measurement of permeability of shale matrix and accurate evaluation of productivity of shale gas horizontal wells.

Fast permeability measurements of tight and sorptive gas reservoirs using a radial-flow transient technique

The pressure transient technique has been widely used for laboratory tests on unconventional gas reservoirs; however, it is still a time-consuming process when applying this technique to rocks of ultra-low permeability in the nano-Darcy scale. The applicability of a novel radial-flow transient technique to achieve fast and accurate permeability measurements is verified by an experimental investigation in this study. Pressure transient tests were performed on two hollow cylindrical shale specimens with different inner radii under radially convergent flow conditions; and for comparison, a solid shale core was also tested via an axial-flow transient technique. The results showed that the time required for a complete pressure pulse decay by the radial-flow test is within several hours compared to a few days by the axial-flow test. It was also found that non-uniform stress distribution along the radius of the sample is the principle factor resulting in errors in the measured permeability; and thus, samples with a small inner radius should be used to reduce the error in the measured permeability. In addition, analytical solutions are derived to interpret the lab data for permeability determination. The accuracy of the proposed technique is elucidated by the small permeability difference of less than 15% compared to the axial flow tests. The permeability error analysis indicated that the effect of compressive storage and gas sorption can be eliminated, and the error is less than 6.7% even though two large pressure pulses of 0.5 MPa were generated. The study experimentally validates that fast and accurate permeability measurements can be achieved by adopting the proposed radial-flow transient technique.

Evaluation of the steady-state coal permeability experiments: a numerical simulation study

By using the numerical simulator developed in our previous work, this paper conducted four simulation cases on the steady-state coal permeability experiments. One case is not backpressure-regulated and the other three are backpressure-regulated with different constant differential pressures between the upstream and the downstream end. The simulation results indicate that the backpressure-regulated steady-state method is superior to the non-backpressure-regulated in terms of the measurement accuracy. The results also indicate that a small differential pressure may be preferable to a higher value for the backpressure-regulated method in order to obtain more accurate permeability measurements. These conclusions may be meaningful for future coal permeability measurements with the steady-state method.

Evaluation of the steady-state coal permeability experiments: a numerical simulation study

By using the numerical simulator developed in our previous work, this paper conducted four simulation cases on the steady-state coal permeability experiments. One case is not backpressure-regulated and the other three are backpressure-regulated with different constant differential pressures between the upstream and the downstream end. The simulation results indicate that the backpressure-regulated steady-state method is superior to the non-backpressure-regulated in terms of the measurement accuracy. The results also indicate that a small differential pressure may be preferable to a higher value for the backpressure-regulated method in order to obtain more accurate permeability measurements. These conclusions may be meaningful for future coal permeability measurements with the steady-state method.

Hydraulic properties of porous sintered glass bead systems

In this paper, porous sintered glass bead packings are studied, using X-ray Computed Tomography (XRCT) images at 16,upmu hbox {m} voxel resolution, to obtain not only the porosity field, but also other properties like particle sizes, pore throats and the permeability. The influence of the sintering procedure and the original particle size distributions on the microstructure, and thus on the hydraulic properties, is analyzed in detail. The XRCT data are visualized and studied by advanced image filtering and analysis algorithms on to the extracted sub-systems (cubes of different sizes) to determine the correlations between the microstructure and the measured macroscopic hydraulic parameters. Since accurate permeability measurements are not simple, special focus lies on the experimental set up and procedure, for which a new innovative multi-purpose cell based on a modular concept is presented. Furthermore, segmented voxel-based images (defining the microstructure) are used for 3D (three-dimensional) lattice Boltzmann simulations to directly compute some of the properties in the creeping flow regime. A very good agreement between experimental and numerical porosity and permeability could be achieved, in most cases, validating the numerical model and results. Porosity and permeability gradients along the sample height could be related to gravity acting during sintering. Furthermore, porosity increases in the outer zones of the samples due to the different contact geometry between the beads and the confining cylinder wall during sintering (which is replaced by a membrane during permeability testing to close these pores at the surface of the sample). The influence of different filters on the gray scale distributions and the impact of the segmentation procedure on porosity and permeability is systematically studied. The complex relationships and dependencies between numerically determined permeabilities and hydraulic influence parameters are investigated carefully. In accordance to the well-known Kozeny–Carman model, a similar trend for local permeability values in dependence on porosity and particle diameter is obtained. Other than statistical models, which estimate the pore throat distribution on the basis of the particle size distribution, in this study XRCT scans are used to determine the pore throats in sintered granular systems, which are finally linked to the intrinsic permeability through the lattice Boltzmann simulations. From the mu XRCT analysis two distinct peaks in pore throat distributions could be identified, which can be clearly assigned to typical pore throat areas occurring in polydisperse granular systems. Moreover, a linear dependency between average pore throat diameter and porosity as well as between permeability and pore throat diameter is reported. Furthermore, almost identical mean values for porosity and permeability are found from sub-system and full-system REV analysis. For sintered granular systems, the empirical constant in the classical Kozeny–Carman model is determined to be 131, while a value of 180 is expected for perfect mono-disperse sphere packings.

Optimized pressure pulse-decay method for laboratory estimation of gas permeability of sorptive reservoirs: Part 1 – Background and numerical analysis

Analysis of transient fluid flow in porous media has several applications in geophysics/geotechnics and engineering. An in-depth evaluation of fluid flow behavior is critical in order to improve the understanding, and development of, laboratory measurement techniques in geo-mechanics, particularly permeability estimation. Given that considerable errors may be yielded in the derived permeabilities of sorptive rocks when using the conventional pressure-pulse decay method (PDM), this paper proposes a new experimental design, an optimized PDM, by creating dual pressure pulses to avoid the pressure disturbance due to compressive storage, ad-/de-sorption and thermal effect during the course of measurement. In this paper, the first of a two-part series, a mathematical model established for the conventional PDM was modified to closely represent the new experimental design, thereby extending the transient technique for permeability measurement of unconventional reservoir rocks, particularly ones with large sorption potential. Considering the complexity of analytical solutions of mathematical models, a comprehensive numerical investigation was established and a detailed comparison was carried out between the conventional and optimized PDMs. The results showed how the profiles of the decay curves change in space and time domain, and how pressure responses are influenced by various parameters in the experimental design for PDM. Combining the new design with numerical simulation results in an optimized technique for fast and accurate permeability measurement of sorptive rocks. In particular, Brace et al.’s solution, the most acknowledged and commonly-used permeability calculation method, was extended for permeability estimation of sorptive rocks. In Part 2, the experimental work under best-replicated in situ stress/strain conditions using the optimized method along with the numerical pressure response results obtained from computer simulation is presented. The results verified the practicality of the optimized PDM and the validity of Brace et al.’s solution for permeability measurement of sorptive rocks.

Measurement of Shale Matrix Permeability and Adsorption with Canister Desorption Test

Permeability estimation is a crucial part of the shale mudrock characterization because it affects the production rate, the pace of recovery and the technically recoverable hydrocarbons. Shale permeability typically falls in the low range of tens of micro-Darcy down to nano-Darcy. Accurate measurement of permeability is a challenging task because the measurement errors are more likely to occur in the low permeability range. This paper presents a common and accurate experimental method for permeability measurement of shale mudrocks known as the canister desorption test. We describe the experiment procedure and present the governing partial differential equation (PDE). The impact of linear and nonlinear adsorption isotherms and the corresponding analytical and numerical solutions are discussed. A workflow for the estimation of permeability and the gas adsorption parameter is presented. The workflow is used to measure the shale matrix permeability and the adsorption parameter for an organic-rich sample from the Marcellus formation. The measurements are in good agreement with an independent study on the Marcellus organic-rich core samples. The results show that the measurement of the adsorption parameter is as important as the permeability measurement in the organic-rich shales. In addition, given that the measurements of permeability and adsorption parameter are performed at a small scale and the gas properties are approximated by average values, it is recommended to perform multiple experiments at different pressures to constrain the uncertainty of the permeability and adsorption measurements. The limitations of the proposed workflow are discussed.

New Technique for Measuring and Controlling the Permeability of Polymeric Membranes

Membranes have wide uses in industry and medicine applications. Polymer membranes are important materials because of their high chemical resistance, but they are of weak mechanical resistance against high pressures. Therefore, it was essential to modify a permeability measuring technique free from high pressure application. The current work represented a modification for the permeability measuring technique of membranes, where ionic salt was added with known concentration to water as common solvent and the electrolyte current was measured behind the membrane. The electrolysis current was correlated to the flow rate of water across a polyvinyl alcohol (PVA) membrane. Some other problems were raised such that polarization on electrodes and changes in electrolyte contents during the long time of the slow process. Pulsed potential on electrodes resolved these problems and other associated problems like rush in current and the double layer capacitance effect. An empirical equation was suggested to evaluate the permeability of polymer membranes by this modified method. Easy and accurate measurement of permeability helped authors to change the permeability of PVA membranes by adding copper nano particles in membrane to reduce its permeability, and adding silicone dioxide micro particles to the PVA membranes to increase its permeability. Authors suggested a mechanism for these permeability changes. Scanning electron microscope images for the filled PVA membranes supported the suggested mechanism. International Journal of Science and Engineering Applications Volume 4 Issue 5, 2015, ISSN-2319-7560 (Online) 315 ww.ijsea.com w

Permeability of EVOH Barrier Material Used in Automotive Applications: Metrology Development for Model Fuel Mixtures

EVOH (Ethylene-Vinyl Alcohol) materials are widely used in automotive applications in multi-layer fuel lines and tanks owing to their excellent barrier properties to aromatic and aliphatic hydrocarbons. These barrier materials are essential to limit environmental fuel emissions and comply with the challenging requirements of fast changing international regulations. Nevertheless, the measurement of EVOH permeability to model fuel mixtures or to their individual components is particularly difficult due to the complexity of these systems and their very low permeability, which can vary by several orders of magnitude depending on the permeating species and their relative concentrations. This paper describes the development of a new automated permeameter capable of taking up the challenge of measuring minute quantities as low as 1 mg/(m 2 .day) for partial fluxes for model fuel mixtures containing ethanol, i -octane and toluene at 50°C. The permeability results are discussed as a function of the model fuel composition and the importance of EVOH preconditioning is emphasized for accurate permeability measurements. The last part focuses on the influence of EVOH conditioning on its mechanical properties and its microstructure, and further illustrates the specific behavior of EVOH in presence of ethanol oxygenated fuels. The new metrology developed in this work offers a new insight in the permeability properties of a leading barrier material and will help prevent the consequences of (bio)ethanol addition in fuels on environmental emissions through fuel lines and tanks.

Insight into Role of Clay-Fluid Molecular Interactions on Permeability and Consolidation Behavior of Na-Montmorillonite Swelling Clay

Swelling clays, also known as expansive clays, are encountered extensively all over the world. These clays are problematic for geotechnical engineering applications because of distress caused to structures and infrastructure as a result of swelling and swelling pressure. These clays are also often used in geoenvironmental engineering applications because of their effective barrier properties as liner materials, e.g., in landfills, ponds, and cutoff trenches. In this study, we report the effect of dielectric constant of fluid on the permeability and consolidation characteristics of Na-montmorillonite swelling clay to investigate the role of clay-fluid molecular interactions on the macroscale properties of the clay. A new “porous rigid wall, flexible wall” permeability device specifically designed for swelling clays that allows for accurate measurement of permeability, swelling pressure and consolidation characteristics, and evaluation of microstructure of swelling clays with fluids with different polarities is used in this study. Results show that clay-fluid molecular interactions have a tremendous effect on the permeability and consolidation characteristics of swelling clay and its microstructure.

Ion-Selective Permeability of an Ultrathin Nanoporous Silicon Membrane as Probed by Scanning Electrochemical Microscopy Using Micropipet-Supported ITIES Tips

We report on the application of scanning electrochemical microscopy (SECM) to the measurement of the ion-selective permeability of porous nanocrystalline silicon membrane as a new type of nanoporous material with potential applications in analytical, biomedical, and biotechnology device development. The reliable measurement of high permeability in the molecularly thin nanoporous membrane to various ions is important for greater understanding of its structure-permeability relationship and also for its successful applications. In this work, this challenging measurement is enabled by introducing two novel features into amperometric SECM tips based on the micropipet-supported interface between two immiscible electrolyte solutions (ITIES) to reveal the important ion-transport properties of the ultrathin nanopore membrane. The tip of a conventional heat-pulled micropipet is milled using the focused ion beam (FIB) technique to be smoother, better aligned, and subsequently, approach closer to the membrane surface, which allows for more precise and accurate permeability measurement. The high membrane permeability to small monovalent ions is determined using FIB-milled micropipet tips to establish a theoretical formula for the membrane permeability that is controlled by free ion diffusion across water-filled nanopores. Moreover, the ITIES tips are rendered selective for larger polyions with biomedical importance, i.e., polyanionic pentasaccharide Arixtra and polycationic peptide protamine, to yield the membrane permeability that is lower than the corresponding diffusion-limited permeability. The hindered transport of the respective polyions is unequivocally ascribed to electrostatic and steric repulsions from the wall of the nanopores, i.e., the charge and size effects.

Permeability Measurement Methods in Porous Media of Fiber Reinforced Composites

Accurate measurement of permeability is critical for fluid flow modeling in porous media. Various experimental methods devised to measure permeability as a porous material property in composites are reviewed. Liquid flow and gas flow methods of permeability measurement for in-plane and transverse directions specifically for fiber-reinforced composites are discussed, as well as issues related to these methods and some associated permeability models. Alternative methods of permeability determination based on cross transport phenomenon are reviewed as well.

Relationship of threshold diameter and Darcean permeability in unconsolidated porous structures

Experiment was conducted on the threshold pressure for atmospheric air through unconsolidated narrow size distributed mini sphere and sand particles at low flow rates. The threshold diameter calculated from measured threshold pressure showed that it does not follow the traditional similarity theory. This is consistent with our experiment on accurate permeability measurement, and can be explained as a result of gas slip flow within such micro pore structure. Our current work tend to find the method to predict the permeability–threshold pressure relationship for unconsolidated porous structures.

Moisture permeability measurement using a surface air dew-point probe: a feasibility study

Moisture permeability of building materials is essential information to predicting moisture transfer in buildings. The conventional way of measuring the permeability of a material is the standard cup test method, which is very time consuming. The paper describes an investigation into the feasibility of using a surface air dew-point probe (SADP), which was first designed by Tsuchiya, to significantly shorten the measurement time. An analysis is presented to show the degree of accuracy required of the measurement of the moisture content changes of the air flowing through the SADP in order that accurate measurement of permeability can be achieved. The requirement, however, may not be achievable with the dew-point temperature sensors currently available. An experimental method for solving this problem is suggested, based on experience gained in trial experiments.

Pulse Decay Permeability: Analytical Solution and Experimental Test

Abstract A new analytical solution is presented for the laboratory pulse decay permeability problem. With this solution, permeability of a core sample can be calculated from the decay rate of a pressure pulse applied to one end of the sample. This development permits rapid, accurate measurement of permeability in samples such as tight gas sands, limestones, and shales.