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<jats:title>ABSTRACT</jats:title><jats:p>Young's modulus and Poisson's ratio are required for geomechanics applications such as hydraulic fracture design, analysis of wellbore stability and rock failure, determination of <jats:italic>in situ</jats:italic> stress and assessment of the response of reservoirs and surrounding rocks to changes in pore pressure and stress. Shales are usually anisotropic and models that neglect shale anisotropy may fail to describe geomechanical behaviour correctly. Anisotropy in shales results from a partial alignment of anisotropic clay particles, kerogen inclusions, microcracks, low‐aspect ratio pores and layering. For shales, the Young's modulus measured parallel to bedding <jats:italic>E</jats:italic><jats:sub>1</jats:sub> is usually greater than the Young's modulus measured perpendicular to bedding <jats:italic>E</jats:italic><jats:sub>3</jats:sub>. However, the Poisson's ratio ν<jats:sub>31</jats:sub> corresponding to stress applied perpendicular to bedding and strain measured parallel to bedding can be greater than, equal to, or less than the Poisson's ratio ν<jats:sub>12</jats:sub> for stress applied parallel to bedding and strain measured parallel to bedding.</jats:p><jats:p>For transverse isotropy, the elastic anisotropy resulting from a partial alignment of clay particles can be written in terms of the coefficients <jats:styled-content><jats:italic>W</jats:italic><jats:sub>200</jats:sub></jats:styled-content> and <jats:styled-content><jats:italic>W</jats:italic><jats:sub>400</jats:sub></jats:styled-content>, which describe the impact of clay particle orientation on the anisotropy of shales. Disorder in the orientation of clay particles acts to reduce <jats:styled-content><jats:italic>W</jats:italic><jats:sub>400</jats:sub></jats:styled-content> faster than <jats:styled-content><jats:italic>W</jats:italic><jats:sub>200</jats:sub></jats:styled-content>, since <jats:styled-content><jats:italic>W</jats:italic><jats:sub>400</jats:sub></jats:styled-content> is a higher order moment of the clay particle orientation distribution function than <jats:styled-content><jats:italic>W</jats:italic><jats:sub>200</jats:sub></jats:styled-content>. This is confirmed by analysis of measured anisotropy parameters for shales. A partial alignment of clay particles is consistent with the measured Young's moduli for shales and with values of Poisson's ratio ν<jats:sub>31</jats:sub> &gt; ν<jats:sub>12</jats:sub> but not with values ν<jats:sub>31</jats:sub> &lt; ν<jats:sub>12</jats:sub>. These values can be explained if there exist kerogen inclusions, microcracks, or low‐aspect ratio pores aligned parallel to the bedding plane.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Shales are rocks with a complex structure. Shales contain high clay content, which constitutes a load‐bearing skeleton. In this study, we present a novel rock physics model to obtain elastic stiffness coefficients of both clays and shales. The robustness of the model is then verified by a field dataset from Eagle Ford shale. We utilize the extended Maxwell homogenization scheme as a rock physics model for transversely isotropic media, which honours the aspect ratio of each inhomogeneity embedded in an effective inclusion domain. Estimated anisotropy parameters ε, γ and δ, on average, are 0.19, 0.29 and 0.04, respectively, based on our modelling results in Eagle Ford shale. Anisotropic modelling results exhibit a good correlation with dipole sonic logs. Both dipole sonic log analysis and rock physics results demonstrate that clay content is the main driver of anisotropy in the field, and there is a direct relationship between clay volume and anisotropy parameters of ε and γ. The method shown here can be readily applied to other unconventional reservoirs.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The Ordovician‐Devonian Sierra Grande Formation, Río Negro Province, Argentina contains three quarzitic members with two iron horizons. Its South Deposit includes both iron horizons. However, the East Deposit is relatively unknown, lacking information about geometry, depth, and reserves. To answer these questions, we apply geophysical methods for the rapid evaluation of the East Deposit, using gravity and magnetic measures.</jats:p><jats:p>The processing of these data allows the suggestion of two 2D models for calculating thicknesses, angles, and depth of the iron horizons. The adjustments between the calculated and the observed curve are less than 6%. One model proposes the existence of the Alfaro iron horizon, and the other one the presence of the Rosales iron horizon at depth. The Bouguer anomalies gravimetric maps allow us to calculate the mineral mass, resulting in 125 million iron tons.</jats:p><jats:p>Thus, this study allowed us to calculate the thicknesses, angles, and depth of both iron horizons, and to adjust and evaluate the mineral reserves with the maximum reliability that potential methods allow when applied to mineral prospecting. These results provide new and valuable information for future mining prospects.</jats:p><jats:p>This article is protected by copyright. All rights reserved</jats:p>