Modeling the effects of microscale fabric complexity on the anisotropy of the Eagle Ford Shale

2016 ◽  
Vol 4 (2) ◽  
pp. SE17-SE29 ◽  
Author(s):  
Qi Ren ◽  
Kyle T. Spikes
Keyword(s):  
Clay Minerals ◽  
Elastic Properties ◽  
Elastic Anisotropy ◽  
Anisotropy Parameter ◽  
Clay Content ◽  
Preferred Orientation ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Clay Concentration ◽  
Anisotropic Elastic

Microscale fabric influences the elastic properties of rock formations. The complexity of the microscale fabric of shale results from composition, platy clay minerals, kerogen, and their preferred orientation patterns. This microscale fabric is also the likely cause of the elastic anisotropy of the rock. In this paper, we have developed a comprehensive three-step rock-physics approach to model the anisotropic elastic properties of the Upper Eagle Ford Shale. We started with anisotropic differential effective medium modeling, followed by an orientation correction, and then a pressure adjustment. This method accounts for the microscale fabric of the rock in terms of the complex composition, shape, and alignment of clay minerals, pore space, and kerogen. In addition, we accounted for different pressure-dependent behaviors of P- and S-waves. Our modeling provides anisotropic stiffnesses and pseudologs of anisotropy parameters. The modeling results match the log measurements relatively well. The clay content, kerogen content, and porosity decreased the rock stiffness. The anisotropy increases with kerogen content, but the influence of clay content was more complex. Comparing the anisotropy parameter pseudologs with clay content shows that clay content increases anisotropy at small concentrations; however, the anisotropy stays constant, or even slightly decreases, as the clay content continues to increase. This result suggests that the preferred orientation of clay clusters is preserved at low clay concentration but vanishes at high clay concentration. This method could also be applied to other shales with carefully chosen parameters to model anisotropic elastic properties.

Characterization of Elastic Anisotropy in Eagle Ford Shale: Impact of Heterogeneity and Measurement Scale

2016 ◽  
Vol 19 (03) ◽  
pp. 429-439 ◽  
Author(s):  
Mehdi Mokhtari ◽  
Matt M. Honarpour ◽  
Azra N. Tutuncu ◽  
Gregory N. Boitnott
Keyword(s):  
Elastic Properties ◽  
Elastic Anisotropy ◽  
Dynamic Properties ◽  
Measurement Scale ◽  
Log Analysis ◽  
Well Log ◽  
Measurement Scales ◽  
Eagle Ford Shale ◽  
Eagle Ford ◽  
Well Log Analysis

Summary Heterogeneity and anisotropy were characterized in some Eagle Ford shale samples at various scales by use of scanning-electron-microscopy (SEM) imaging, computed-tomography (CT) scanning, and compressional-velocity scanning. Triaxial testing on 1-in.-diameter and 3-in.-diameter core samples and well-log analysis were used to calculate elastic properties by using vertical transverse isotropic modeling. Correlations between the stiffness coefficients and the correlations between static and dynamic properties from laboratory tests were applied to well-log analysis to improve the calculation of minimum horizontal stress. This paper provides the elastic properties of the Eagle Ford shale at various measurement scales. The paper also elaborates the role of heterogeneity in laboratory testing of shale reservoirs.

Anisotropy of experimentally compressed kaolinite-illite-quartz mixtures

Geophysics ◽  
2009 ◽  
Vol 74 (1) ◽  
pp. D13-D23 ◽  
Author(s):  
Marco Voltolini ◽  
Hans-Rudolf Wenk ◽  
Nazmul Haque Mondol ◽  
Knut Bjørlykke ◽  
Jens Jahren
Keyword(s):  
Single Crystal ◽  
Elastic Properties ◽  
Compaction Pressure ◽  
Clay Content ◽  
Orientation Distribution ◽  
Rietveld Analysis ◽  
Preferred Orientation ◽  
P Wave ◽  
Velocity Anisotropy ◽  
Pole Figures

The anisotropy of physical properties is a well-known characteristic of many clay-bearing rocks. This anisotropy has important implications for elastic properties of rocks and must be considered in seismic modeling. Preferred orientation of clay minerals is an important factor causing anisotropy in clay-bearing rocks such as shales and mudstones that are the main cap rocks of oil reservoirs. The preferred orientation of clays depends mostly on the amount of clays and the degree of compaction. To study the effect of these parameters, we prepared several samples compressing (at two effective vertical stresses) a mixture of clays (illite and kaolinite) and quartz (silt) with different clay/quartz ratios. The preferred orientation of the phases was quantified with Rietveld analysis on synchrotron hard X-ray images. Pole figures for kaolinite and illite display a preferred orientationof clay platelets perpendicular to the compaction direction, increasing in strength with clay content and compaction pressure. Quartz particles have a random orientation distribution. Aggregate elastic properties can be estimated by averaging the single-crystal properties over the orientation distribution obtained from the diffraction data analysis. Calculated P-wave velocity anisotropy ranges from 0% (pure quartz sample) to 44% (pure clay sample, highly compacted), but calculated velocities are much higher than measured velocities. This is attributed to uncertainties about single-crystal elastic properties and oriented micropores and limited grain contacts that are not accounted for in the model. In this work, we present an effective method to obtain quantitative data, helping to evaluate the role of clay percentage and compaction pressure on the anisotropy of elastic properties of clay-bearing rocks.

Application of nanoindentation for uncertainty assessment of elastic properties in mudrocks from micro- to well-log scales

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. D327-D339 ◽  
Author(s):  
Clotilde Chen Valdes ◽  
Zoya Heidari
Keyword(s):  
Young’S Modulus ◽  
Clay Minerals ◽  
Elastic Properties ◽  
Young's Modulus ◽  
Soft Rock ◽  
Elastic Stiffness ◽  
Mechanical Tests ◽  
Well Log ◽  
Eagle Ford ◽  
Effective Elastic Properties

Uncertainty in estimates of elastic properties of soft mudrock components, such as clay minerals and kerogen, can influence well-log-based evaluation of effective elastic properties in organic-rich mudrocks. Existing methods, such as effective medium models for well-log-based assessment of elastic properties, assume a constant stiffness and an idealized shape for rock components. However, these characteristics might vary depending on the distribution and size of that particular component, as well as its adjacent components. Furthermore, there is a significant uncertainty in elastic properties of kerogen in the case of organic-rich mudrocks. The uncertainty associated with the aforementioned parameters on effective elastic properties of rocks has not been investigated in existing publications. In this paper, we quantified the variability in elastic properties of individual mudrock components caused by their spatial distribution, size, and rock fabric at the microscale and their impacts on well-log-based evaluation of effective elastic properties. We performed nanoindentation mechanical tests on samples from the Haynesville and the lower Eagle Ford Formations, to measure Young’s modulus and hardness at targeted locations. Then, we quantified the variability of Young’s modulus in the microscale and its impact on effective elastic properties at the micro- and well-log scales. Results reveal significant uncertainties in measurements of elastic properties of soft rock components, associated with their location and size. Young’s moduli of individual clay components are higher when located adjacent to stiff rock components, such as large quartz and calcite grains. Results reveal that 25% and 12% uncertainties in measured elastic properties of clay minerals affect well-log-based estimates of effective elastic stiffness coefficients up to 29% and 11% in the Haynesville and the lower Eagle Ford Formations, respectively. These uncertainties can be more significant in cases with a higher concentration of clay minerals and kerogen.

scholarly journals Anisotropic elastic properties of FexB (x = 1, 2, 3) under pressure. First-principles study

2016 ◽  
Vol 34 (3) ◽  
pp. 503-516 ◽  
Author(s):  
A. Gueddouh ◽  
B. Bentria ◽  
Y. Bourourou ◽  
S. Maabed
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Density Functional ◽  
Elastic Anisotropy ◽  
Poisson Ratio ◽  
Pressure Effects ◽  
Mechanical Anisotropy ◽  
First Principles Calculation ◽  
Young’S Moduli ◽  
Anisotropic Elastic

AbstractSpin-polarization (SP) and pressure effects have been used to better clarify and understand anisotropic elastic properties of Fe-B intermetallic compounds using the first-principles calculation with generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory. Elastic properties, including bulk, shear and Young’s moduli as well as Poisson ratio were obtained by Voigt-Reuss-Hill approximation. All studied Fe-B compounds were mechanically stable. The brittle and ductile properties were discussed using bulk to shear moduli ratio (B/G) of the studied structures in the pressure range of 0 GPa to 90 GPa in order to predict the critical pressure of phase transition from ferromagnetic (FM) to nonmagnetic (NM) state. Mechanical anisotropy in both cases was discussed by calculating different anisotropic indexes and factors. We have plotted three-dimensional (3D) surfaces and planar contours of the bulk and Young’s moduli of FexB (x = 1, 2, 3) compounds for some crystallographic planes, (1 0 0), (0 1 0) and (0 0 1), to reveal their elastic anisotropy. On the basis of anisotropic elastic properties the easy and hard axes of magnetization for the three studied compounds were predicted.

The elastic anisotropy of clay minerals

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. C193-C203 ◽  
Author(s):  
Colin M. Sayers ◽  
Lennert D. den Boer
Keyword(s):  
Clay Minerals ◽  
Elastic Properties ◽  
Elastic Moduli ◽  
Elastic Anisotropy ◽  
Elastic Stiffness ◽  
Stiffness Tensor ◽  
Covalent Bonds ◽  
Best Fitting ◽  
Anisotropy Parameters ◽  
Elastic Stiffness Tensor

The layered structure of clay minerals produces large elastic anisotropy due to the presence of strong covalent bonds within layers and weaker electrostatic bonds in between. Technical difficulties associated with small grain size preclude experimental measurement of single-crystal elastic moduli. However, theoretical calculations of the complete elastic tensors of several clay minerals have been reported, using either first-principle calculations based on density functional theory or molecular dynamics. Because of the layered microstructure, the elastic stiffness tensor obtained from such calculations can be approximated to good accuracy as a transversely isotropic (TI) medium. The TI-equivalent elastic moduli of clay minerals indicate that Thomsen’s anisotropy parameters [Formula: see text] and [Formula: see text] are large and positive, whereas [Formula: see text] is small or negative. A least-squares inversion for the elastic properties of a best-fitting equivalent TI medium consisting of two isotropic layers to the elastic properties of clay minerals indicates that the shear modulus of the stiffest layer is considerably larger than the softest layer, consistent with the expected high compliance of the interlayer region in clay minerals. It is anticipated that the elastic anisotropy parameters derived from the best-fitting TI approximation to the elastic stiffness tensor of clay minerals will find applications in rock physics for seismic imaging, amplitude variation with offset analysis, and geomechanics.

Anisotropic Elastic Properties of Low-k Dielectric Materials

2004 ◽  
Vol 812 ◽  
Author(s):  
A.A. Maznev ◽  
A. Mazurenko ◽  
G. Alper ◽  
C.J.L. Moore ◽  
M. Gostein ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Acoustic Waves ◽  
Isotropic Material ◽  
Elastic Anisotropy ◽  
Surface Acoustic Waves ◽  
Transversely Isotropic ◽  
Dielectric Materials ◽  
Out Of Plane ◽  
Anisotropic Elastic ◽  
Low K

AbstractA non-contact optical technique based on laser-generated surface acoustic waves (SAWs) was used to characterize elastic properties of two types of thin (150-1100 nm) low-k films: more traditional non-porous organosilicate glass PECVD films (k=3.0) and novel mesoporous silica films fabricated in supercritical CO2 (k=2.2). The acoustic response of the non-porous samples is well described by a model of an elastically isotropic material with two elastic constants, Young's modulus and Poisson's ratio. Both parameters can be determined by analyzing SAW dispersion curves. However, the isotropic model fails to describe the SAW dispersion in the mesoporous samples. Modifying the model to allow a difference between in-plane and out-of plane properties (i.e., a transversely isotropic material) results in good agreement between the measurements and the model. The in-plane compressional modulus is found to be 2-3 times larger than the out-of plane modulus, possibly due to the anisotropic shape of the pores. Elastic anisotropy should therefore be taken into account in modeling mechanical behavior of low-k materials.

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