Grain-size to effective pore-size transformation derived from electrokinetic theory

Geophysics ◽  
2009 ◽  
Vol 74 (1) ◽  
pp. E17-E29 ◽  
Author(s):  
P. W. Glover ◽  
E. Walker
Keyword(s):  
Grain Size ◽  
Porous Media ◽  
Pore Size ◽  
Theta Function ◽  
Pore Radius ◽  
Data Set ◽  
Effective Grain Size ◽  
Effective Pore Size ◽  
Effective Pore Radius ◽  
Grain Diameter

Most permeability models use effective grain size or effective pore size as an input parameter. Until now, an efficacious way of converting between the two has not been available. We propose a simple conversion method for effective grain diameter and effective pore radius using a relationship derived by comparing two independent equations for permeability, based on the electrokinetic properties of porous media. The relationship, which we call the theta function, is not dependent upon a particular geometry and implicitly allows for the widely varying style of microstructures exhibited by porous media by using porosity, cementation exponent, formation factor, and a packing constant. The method is validated using 22 glass bead packs, for which the effective grain diameter is known accurately, and a set of 188 samples from a sand-shale sequence in the North Sea. This validation uses measurements of effective grain size from image analysis, pore size from mercury injection capillary pressure (MICP) measurements, and effective pore radius calculated from permeability experiments, all of which are independent. Validation tests agree that the technique accurately converts an effective grain diameter into an effective pore radius. Furthermore, for the clastic data set, there exists a power law relationship in porosity between effective grain size and effective pore size. The theta function also can be used to predict the fluid permeability of a sample, based on effective pore radius. The result is extremely good predictions over seven orders of magnitude.

Testing the efficiency of ferrofluid impregnation in porous media – recommendations for future magnetic pore fabric studies

2020 ◽  
Author(s):  
Michele Pugnetti ◽  
Yi Zhou ◽  
Andrea Biedermann
Keyword(s):  
Grain Size ◽  
Porous Media ◽  
Magnetic Susceptibility ◽  
Pore Size ◽  
Magnetic Measurements ◽  
Vacuum Impregnation ◽  
Physical Parameters ◽  
High Porosity ◽  
Nanoparticle Distribution ◽  
Flow Through

<p><strong>Testing the efficiency of ferrofluid impregnation in porous media – recommendations for future magnetic pore fabric studies</strong></p><p> </p><p>Michele Pugnetti*, Yi Zhou*, Andrea R. Biedermann*</p><p>* Institute of Geological Sciences, University of Bern, Baltzerstrasse 1+3, CH-3012 Bern, Switzerland ([email protected])</p><p> </p><p>In AMS (anisotropy of magnetic susceptibility)-based pore fabric studies, the role of ferrofluid impregnation is crucial to ensure significant magnetic measurements. However, no standard methods to test the ferrofluid impregnation of porous media have been proposed so far. The details of fluid behaviour in porous media are important in many fields of natural sciences, but nanoparticle distribution in the fluid is particularly important for magnetic measurements. In this study methods to test the impregnation efficiency of ferrofluid in porous media, and nanoparticle distribution are proposed, using different materials: wood, agarose and TEOS (tetraethylorthosilicate) gel, and synthetic samples of given composition and grain size, as well as natural rocks. Magnetic pore fabric measurements are normally performed on natural porous samples to correlate the direction of maximum magnetic susceptibility with the direction of preferred pore elongation, and preferred flow direction. The advantage of using artificial samples is the possibility to control and adjust some physical parameters, including porosity and pore size, to keep them more uniform or fix them to a given value. This allows investigating the nanoparticle distribution in ideal samples without the influence of additional heterogeneities inherent to natural samples and to determine the lowest porosity value and smallest pore size that is possible to impregnate with ferrofluid. In particular, the agarose and TEOS gel have a uniform porous structure controlled by the gel concentration or chemical agents used in sample preparation. The wood has a wider range of porosity compared to rocks and a known intrinsically anisotropic structure. The synthetic samples have a uniform grain size, mineralogy and structure. First the porosity of the samples was measured, then to impregnate the samples different methods were developed and tested, (1) percolation, (2) standard vacuum impregnation, (3) flow-through impregnation, (4) diffusion process in gel structure. Impregnation efficiency was evaluated both optically and magnetically. Different impregnation methods provide different impregnation efficiency depending also on the investigated material; in particular porosity plays an important role in limiting the impregnation efficiency. Initial experiments indicate that in general, flow-through impregnation is more efficient than vacuum impregnation because it combines the effect of vacuum with the pressure applied to the fluid that is pushed through the sample. The best results on natural samples were obtained using calcarenites with relatively high porosity. These results and the methods proposed here will help advance magnetic pore fabrics studies and impregnation processes in general.   </p><p> </p>

Controls on induced polarization in sandy unconsolidated sediments and application to aquifer characterization

Geophysics ◽  
2003 ◽  
Vol 68 (5) ◽  
pp. 1547-1558 ◽  
Author(s):  
L. D. Slater ◽  
D. R. Glaser
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Internal Surface ◽  
Ionic Mobility ◽  
Induced Polarization ◽  
Hysteretic Behavior ◽  
Degree Of Saturation ◽  
Unconsolidated Sediments ◽  
Fluid Conductivity ◽  
Grain Diameter

Resistivity and induced polarization (IP) measurements (0.1–1000 Hz) were made on clay‐free unconsolidated sediments from a sandy, alluvial aquifer in the Kansas River floodplain. The sensitivity of imaginary conductivity σ″, a fundamental IP measurement, to lithological parameters, fluid conductivity, and degree of saturation was assessed. The previously reported power law dependence of IP on surface area and grain size is clearly observed despite the narrow lithologic range encountered in this unconsolidated sedimentary sequence. The grain‐size σ″ relationship is effectively frequency independent between 0.1 and 100 Hz but depends on the representative grain diameter used. For the sediments examined here, d90, the grain diameter of the coarsest sediments in a sample, is well correlated with σ″. The distribution of the internal surface in the well‐sorted, sandy sediments investigated here is such that most of the sample weight is likely required to account for the majority of the internal surface. We find the predictive capability of the Börner model for hydraulic conductivity (K)estimation from IP measurements is limited when applied to this narrow lithologic range. The relatively weak dependence of σ″ on fluid conductivity (σw) observed for these sediments when saturated with an NaCl solution (0.06–10 S/m) is consistent with competing effects of surface charge density and surface ionic mobility on σ″ as previously inferred for sandstone. Importantly, IP parameters are a function of saturation and exhibit hysteretic behavior over a drainage and imbibition cycle. However, σ″ is less dependent than the real conductivity σ′ on saturation. In the case of evaporative drying, the σ″ saturation exponent is approximately half of the σ′ exponent. Crosshole IP imaging illustrates the potential for lithologic discrimination of unconsolidated sediments. A fining‐upward sequence correlates with an upward increase in normalized chargeability Mn, a field IP parameter proportional to σ″. The hydraulic conductivity distribution obtained from the Börner model discriminates a hydraulically conductive sand–gravel from overlying medium sand.

scholarly journals The effective pore radius of screen wicks.

1990 ◽  
Vol 56 (521) ◽  
pp. 168-174 ◽  
Author(s):  
Hiroaki KOZAI ◽  
Hideaki IMURA ◽  
Yuji IKEDA
Keyword(s):  
Pore Radius ◽  
Effective Pore Radius

scholarly journals Modifications to Kozeny–Carman model to enhance petrophysical relationships

2017 ◽  
Author(s):  
Amir M. S. Lala
Keyword(s):  
Grain Size ◽  
Pore Size ◽  
The Other ◽  
Shaly Sand ◽  
Two Parameters ◽  
Log Linear

Abstract. The most commonly used relationship relates permeability to porosity, grain size, and tortuosity is Kozeny–Carman formalism. When it is used to estimate the permeability behavior versus porosity, the other two parameters (the grain size and tortuosity) are usually kept constant. Here, we investigate the deficiency of the Kozeny–Carman assumption and offer alternative derived equations for the Kozeny–Carman equation, including equations where the grain size is replaced with the pore size and with varying tortuosity. We also introduced relationships for the permeability of shaly sand reservoir that answer the approximately linear permeability decreases in the log-linear permeability-porosity relationships in datasets from different locations.

Evaluation and Modeling of the CO2Permeability Variation by Coupling Effective Pore Size Evolution in Anthracite Coal

2015 ◽  
Vol 29 (2) ◽  
pp. 717-723 ◽  
Author(s):  
Junqian Li ◽  
Dameng Liu ◽  
Shuangfang Lu ◽  
Yanbin Yao ◽  
Haitao Xue
Keyword(s):  
Pore Size ◽  
Anthracite Coal ◽  
Size Evolution ◽  
Effective Pore Size
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