Are self-consistent models capable of jointly modeling elastic velocity and electrical conductivity of reservoir sandstones?

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. D377-D382 ◽  
Author(s):  
Tongcheng Han ◽  
Michael Ben Clennell ◽  
Arthur C. H. Cheng ◽  
Marina Pervukhina
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Aspect Ratio ◽  
Physical Property ◽  
S Waves ◽  
Ratio Spectrum ◽  
Aspect Ratios ◽  
Self Consistent ◽  
Spectrum Distribution ◽  
Reservoir Sandstones

Self-consistent (SC) models are commonly used for simulating elastic and electrical properties of reservoir rocks. We have developed a technique to test the capability of SC models to jointly model elastic velocity and electrical conductivity of porous media using a database of measurements of these properties on reservoir sandstones. The pores were represented by randomly oriented spheroidal shapes with a spectrum distribution of aspect ratios, and elasticity theory was used to compute the variation of aspect ratios and volume fractions of the pores subject to varying differential pressures. Using this method, the pore aspect ratio spectra of a reservoir sandstone were obtained separately from the measured elastic (P- and S-waves) velocity and electrical conductivity under loading. We have determined that when the SC formalism is used, there is a systematic discrepancy in the estimated pore structure predicted by the two measurements. Despite the supposed applicability of the SC method to this class of problem, the pore aspect ratio spectrum inverted from one physical property (e.g., velocity or conductivity) failed in practice to predict the other physical property (e.g., conductivity or velocity), at least for porous sandstones. Our results suggested the requirement of a new model to link the elastic and electrical properties to a unified pore aspect ratio spectrum of rocks.

Inversion of dry and saturated P- and S-wave velocities for the pore-aspect-ratio spectrum using a cracked porous medium elastic wave theory

Geophysics ◽  
2021 ◽  
Vol 86 (6) ◽  
pp. A57-A62
Author(s):  
He-Ming Wang ◽  
Xiao-Ming Tang
Keyword(s):  
Porous Medium ◽  
Aspect Ratio ◽  
Elastic Wave ◽  
Research Work ◽  
Wave Theory ◽  
Wave Dispersion ◽  
Velocity Data ◽  
S Wave ◽  
Ratio Spectrum ◽  
Aspect Ratios

Subsurface rocks contain pores and cracks of various sizes. The cracked porous medium elastic wave theory that describes wave propagation characteristics due to the pore-crack interaction is extended to include cracks of different aspect ratios. The extended theory is applied to model P- and S-wave velocity data of dry and fluid-saturated rock under pressure loading conditions, so as to determine the pore-aspect-ratio spectrum through an inversion procedure. The inversion result is consistent with that from the scanning electron microscope analysis, showing significant improvement versus previous inversion. The inverted pore-aspect-ratio spectrum is input into the wave theory to predict the velocity dispersion of the rock in the full frequency range. The predicted dispersion and its variation trend with pressure agree with the data measured in the (2–200, 106) Hz range at various differential pressures, whereas the modeling using a single-aspect-ratio theory has difficulty matching the data. This research work provides not only a method for analyzing the pore structure characteristics of rocks from the laboratory ultrasonic velocity data, but also a way to predict the seismic wave dispersion from the data.

A Generalized Self-Consistent Mechanics Method for Solids Containing Elliptical Inclusions

1995 ◽  
Vol 62 (3) ◽  
pp. 566-572 ◽  
Author(s):  
Y. Huang ◽  
K. X. Hu
Keyword(s):  
Aspect Ratio ◽  
Current Approach ◽  
Effective Moduli ◽  
Shear Moduli ◽  
Aspect Ratios ◽  
Isotropic Distribution ◽  
Energy Equivalence ◽  
Self Consistent ◽  
Consistent Method

The determination of the effective moduli for a material containing elliptical inclusions is the objective of this paper. This is done by incorporating an inclusion/matrix/composite model into a general energy equivalence framework. Through the evaluation of the average strain in each individual inclusion, the current approach can handle the inclusion’s orientation dependency in a straightforward manner. The case of an in-plane isotropic distribution of elliptical inclusions is addressed in detail. For the case of reinforcements, or hard inclusions, the effect of the inclusion aspect ratio on in-plane effective moduli is small if the aspect ratio is larger than 0.5. For aspect ratios less than 0.3, the effective moduli increase dramatically, which implies that flat reinforcements are much more effective than traditional cylindrical reinforcements. It is also established that the generalized self-consistent method predicts a stronger dependence of effective moduli on the inclusion aspect ratio than does the Mori-Tanaka method, especially for shear moduli.

Prediction of Biot’s coefficient from rock-physical modeling of North Sea chalk

Geophysics ◽  
2008 ◽  
Vol 73 (2) ◽  
pp. E89-E96 ◽  
Author(s):  
Casper Olsen ◽  
Kathrine Hedegaard ◽  
Ida L. Fabricius ◽  
Manika Prasad
Keyword(s):  
Aspect Ratio ◽  
North Sea ◽  
Free Parameter ◽  
The Self ◽  
P Wave ◽  
Biot’S Coefficient ◽  
Aspect Ratios ◽  
Consistent Model ◽  
Self Consistent ◽  
Water Saturated

We predict Biot’s coefficient for North Sea chalk based on density and P-wave velocity for water-saturated chalk. We compare three effective medium models: Berryman’s self-consistent model, the isoframe model, and the bounding-average method (BAM). The self-consistent model is used with two combinations of aspect ratios. In one combination, the aspect ratio is equal for pores and grains. In the other combination, the aspect ratio for grains is kept constant close to 1 and the aspect ratio for pores varies. All the models include one free parameter that determines the stiffness of the rock for a fixed porosity. This free parameter is compared with Biot’s coefficient to discuss whether the free parameter is related to pore-space compressibility for North Sea chalk. We also discuss how consistent the models are between P-wave modulus and shear modulus for dry and water-saturated chalk. The acoustic velocity and the density data for dry and water-saturated chalk are all laboratory data. The isoframe model and the BAM model predict Biot’s coefficient with a smaller error than the self-consistent model does. The free parameter in the isoframe model and the BAM model is related to Biot’s coefficient. The free parameter in the self-consistent model is related only to Biot’s coefficient for water-saturated chalk when the aspect ratios for pores and grains are equal. The isoframe and the BAM model are generally more consistent for chalk than the self-consistent model is.

scholarly journals Linking preferred orientations to elastic anisotropy in Muderong Shale, Australia

Geophysics ◽  
2015 ◽  
Vol 80 (1) ◽  
pp. C9-C19 ◽  
Author(s):  
Waruntorn Kanitpanyacharoen ◽  
Roman Vasin ◽  
Hans-Rudolf Wenk ◽  
David. N. Dewhurst
Keyword(s):  
Aspect Ratio ◽  
Volume Fraction ◽  
Elastic Anisotropy ◽  
Ambient Pressure ◽  
Preferred Orientation ◽  
Validity And Reliability ◽  
Crystallographic Preferred Orientation ◽  
Aspect Ratios ◽  
Average Aspect Ratio ◽  
Self Consistent

The significance of shales for unconventional hydrocarbon reservoirs, nuclear waste repositories, and geologic carbon storage has opened new research frontiers in geophysics. Among many of its unique physical properties, elastic anisotropy had long been investigated by experimental and computational approaches. Here, we calculated elastic properties of Cretaceous Muderong Shale from Australia with a self-consistent averaging method based on microstructural information. The volume fraction and crystallographic preferred orientation distributions of constituent minerals were based on synchrotron x-ray diffraction experiments. Aspect ratios of minerals and pores, determined from scanning electron microscopy, were introduced in the self-consistent averaging. Our analysis suggested that phyllosilicates (i.e., illite-mica, illite-smectite, kaolinite, and chlorite) were dominant with [Formula: see text]. The shape of clay platelets displayed an average aspect ratio of 0.05. These platelets were aligned parallel to the bedding plane with a high degree of preferred orientation. The estimated porosity at ambient pressure was [Formula: see text] and was divided into equiaxial pores and flat pores with an average aspect ratio of 0.01. Our model gave results that compared satisfactorily with values derived from ultrasonic velocity measurements, confirming the validity and reliability of our approximations and averaging approach.

Microstructural Design of Graphene Nanocomposites for Improved Electrical Conductivity

2021 ◽  
pp. 1-23
Author(s):  
Audrey Gbaguidi ◽  
Sirish Namilae ◽  
Daewon Kim
Keyword(s):  
Electrical Conductivity ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Graphene Nanoplatelets ◽  
Hybrid Nanocomposites ◽  
Electrical Performance ◽  
Partial Replacement ◽  
Minimal Amount ◽  
Graphene Nanocomposites ◽  
Aspect Ratios

Abstract The electrical conductivity and percolation onset of graphene-based nanocomposites are studied by varying both planar and transversal aspect ratios of graphene nanoplatelets (GNP) fillers using a three-dimensional stochastic percolation-based model. The graphene nanoplatelets are modeled as elliptical fillers to enable aspect ratio variations. We find that decreasing the graphite's thickness results in an exponential performance improvement of the nanocomposites, in contrast to a linear improvement obtained when the planar aspect ratio is increased, for same filler volume. Furthermore, we show that hybrid nanocomposites fabricated with partial replacement of GNP by carbon nanotube (CNT) may improve the electrical performance of the GNP monofiller composites. Improvement or deterioration of the electrical properties is mainly based on the morphology and content of the fillers mixed in the hybrids. Nonetheless, using a minimal amount of CNT for substitution always leads to the highest improvement in conductivity, while additional CNTs only leads to smaller improvement at best or even deterioration. The results are validated by comparing with experimental works and offer useful insights for the fabrication of highly conductive nanocomposites.

Effect of Gamma Radiation on Structural, Optical and Electrical Properties of nanostructured CdHgTe Thin Films

2018 ◽  
Vol 1 (1) ◽  
pp. 26-31 ◽  
Author(s):  
B Babu ◽  
K Mohanraj ◽  
S Chandrasekar ◽  
N Senthil Kumar ◽  
B Mohanbabu
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Electrical Properties ◽  
Gamma Radiation ◽  
Glass Substrate ◽  
Gamma Ray ◽  
Optical And Electrical Properties ◽  
Deposition Technique ◽  
Polycrystalline Structure ◽  
Dc Electrical Conductivity

CdHgTe thin films were grown onto glass substrate via the Chemical bath deposition technique. XRD results indicate that a CdHgTe formed with a cubic polycrystalline structure. The crystallinity of CdHgTe thin films is gradually deteriorate with increasing the gamma irradiation. EDS spectrums confirms the presence of Cd, Hg and Te elements. DC electrical conductivity results depicted the conductivity of CdHgTe increase with increasing a gamma ray dosage

Effect of the structure of cellulose acetate membranes on their permeability, electrical conductivity and rejection

1990 ◽  
Vol 55 (12) ◽  
pp. 2933-2939 ◽  
Author(s):  
Hans-Hartmut Schwarz ◽  
Vlastimil Kůdela ◽  
Klaus Richau
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Cellulose Acetate ◽  
Reverse Osmosis ◽  
Water Flux ◽  
Cellulose Acetate Membrane ◽  
Structure Parameters ◽  
Dc Electrical Conductivity ◽  
Cellulose Acetate Membranes

Ultrafiltration cellulose acetate membrane can be transformed by annealing into reverse osmosis membranes (RO type). Annealing brings about changes in structural properties of the membranes, accompanied by changes in their permeability behaviour and electrical properties. Correlations between structure parameters and electrochemical properties are shown for the temperature range 20-90 °C. Relations have been derived which explain the role played by the dc electrical conductivity in the characterization of rejection ability of the membranes in the reverse osmosis, i.e. rRO = (1 + exp (A-B))-1, where exp A and exp B are statistically significant correlation functions of electrical conductivity and salt permeation, or of electrical conductivity and water flux through the membrane, respectively.

scholarly journals Effects of Steel Fiber Percentage and Aspect Ratios on Fresh and Harden Properties of Ultra-High Performance Fiber

2021 ◽  
Vol 2 (3) ◽  
pp. 501-515
Author(s):  
Rajib Kumar Biswas ◽  
Farabi Bin Ahmed ◽  
Md. Ehsanul Haque ◽  
Afra Anam Provasha ◽  
Zahid Hasan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Aspect Ratio ◽  
High Performance ◽  
Steel Fiber ◽  
Setting Time ◽  
Fiber Reinforced Concrete ◽  
Future Research ◽  
Manufacturing Cost ◽  
Aspect Ratios ◽  
High Performance Fiber

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers to understand the distinctive characteristics of UHPFRC.

scholarly journals Surface Texturing of Si with Periodically Arrayed Oblique Nanopillars to Achieve Antireflection

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 380
Author(s):  
Jun-Hyun Kim ◽  
Sanghyun You ◽  
Chang-Koo Kim
Keyword(s):  
Aspect Ratio ◽  
Plasma Etching ◽  
Surface Texturing ◽  
Light Reflection ◽  
Si Substrate ◽  
Weighted Mean ◽  
Optical Reflectance ◽  
Si Substrates ◽  
Aspect Ratios ◽  
Shadowing Effect

Si surfaces were texturized with periodically arrayed oblique nanopillars using slanted plasma etching, and their optical reflectance was measured. The weighted mean reflectance (Rw) of the nanopillar-arrayed Si substrate decreased monotonically with increasing angles of the nanopillars. This may have resulted from the increase in the aspect ratio of the trenches between the nanopillars at oblique angles due to the shadowing effect. When the aspect ratios of the trenches between the nanopillars at 0° (vertical) and 40° (oblique) were equal, the Rw of the Si substrates arrayed with nanopillars at 40° was lower than that at 0°. This study suggests that surface texturing of Si with oblique nanopillars reduces light reflection compared to using a conventional array of vertical nanopillars.

scholarly journals Strength Analysis of Alternative Airframe Layouts of Regional Aircraft on the Basis of Automated Parametrical Models

Aerospace ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 80
Author(s):  
Dmitry V. Vedernikov ◽  
Alexander N. Shanygin ◽  
Yury S. Mirgorodsky ◽  
Mikhail D. Levchenkov
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
High Performance ◽  
Strength Analysis ◽  
Labor Input ◽  
Aerodynamic Loading ◽  
Aspect Ratios ◽  
Wide Range ◽  
Parametrical Design

This publication presents the results of complex parametrical strength investigations of typical wings for regional aircrafts obtained by means of the new version of the four-level algorithm (FLA) with the modified module responsible for the analysis of aerodynamic loading. This version of FLA, as well as a base one, is focused on significant decreasing time and labor input of a complex strength analysis of airframes by using simultaneously different principles of decomposition. The base version includes four-level decomposition of airframe and decomposition of strength tasks. The new one realizes additional decomposition of alternative variants of load cases during the process of determination of critical load cases. Such an algorithm is very suitable for strength analysis and designing airframes of regional aircrafts having a wide range of aerodynamic concepts. Results of validation of the new version of FLA for a high-aspect-ratio wing obtained in this work confirmed high performance of the algorithm in decreasing time and labor input of strength analysis of airframes at the preliminary stages of designing. During parametrical design investigation, some interesting results for strut-braced wings having high aspect ratios were obtained.

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