Improved Rock-Physics Model for Shale Gas Reservoirs

Zhu, Yongmei; Xu, Shiyu; Payne, Michael A.; Martinez, Alex; Liu, Enru; Harris, Chris; Bandyopadhyay, Kaushik

doi:10.1190/segam2012-0927.1

Cited by 35 publications

(15 citation statements)

References 6 publications

(10 reference statements)

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“…Zhu et al (2012Zhu et al ( , 2013 use the Gassmann-type model developed by Carcione et al (2011) to incorporate TOC effects, mineralogy, porosity, and fluid content, and they describe the seismic properties of source rocks. Their modeling indicates that an increase in TOC generally reduces the P-wave impedance and the V P ∕V S ratio, increasing the velocity anisotropy, as already shown by Carcione (2000), where V P and V S denote the P-and S-wave velocities.…”

Section: Introductionmentioning

confidence: 99%

Rock-physics templates for clay-rich source rocks

Carcione

Avseth

2015

GEOPHYSICS

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Shale source rocks are composed of various minerals, mainly smectite and illite, depending on the burial depth, and they can be described as transversely isotropic media. The "pore space" may contain kerogen, water, oil, and gas determined by the in situ conditions. A petroelastic description is based on the following: Smectite-illite transformation as a function of depth is described by a fifth-order kinetic reaction. Backus averaging to "mix" isotropic smectite and anisotropic illite is then used to obtain the elasticity constants of the mineral composing the frame. Porosity is obtained from density, and water is part of the mineral, whose elasticity constants are obtained from Gassmann equations. Oil and gas generated from kerogen are assumed to saturate the kerogen phase. The bulk modulus of the oil-gas mixture is calculated by a mesoscopic-loss model, and the stiffnesses of the kerogen/fluid mixture are obtained with the Kuster and Toksöz model, assuming that the fluid is included in a kerogen matrix. Two models are considered to obtain the seismic velocities of the shale, namely, Backus averaging and the Gassmann equation generalized to the anisotropic case with a solid pore infill. We built rock-physics templates (RPTs) containing only kerogen (immature) and kerogen plus hydrocarbons (mature). Pore-pressure effects were modeled and used as templates. We considered the Kimmeridge Shale at different depths. To model kerogen-oil and oil-gas conversions, we assumed a basin-evolution model with a constant sedimentation rate, geothermal gradient, and a first-order kinetic (Arrhenius) reaction. The detection of the hydrocarbons was investigated from RPTs, built with wave velocities, impedances, Lamé constants, density, Poisson ratio, Young modulus, and anisotropy parameters for varying kerogen content, fluid saturations, and pore pressure. Moreover, the amplitude variation with offset intercept and gradients were computed, corresponding to the seismic response of a source rock layer for varying kerogen content and fluid saturation.

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Section: Introductionmentioning

confidence: 99%

Rock-physics templates for clay-rich source rocks

Carcione

Avseth

2015

GEOPHYSICS

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“…Subsequent work modified this approach to provide an improved description of the elastic response of shales, including the incorporation of organic matter into the shale microstructure model (Sayers ; Jakobson, Hudson and Johansen ; Ortega, Ulm and Abousleiman ; Zhu et al . ; Vasin et al . ; Sayers ; Qin, Han, and Zhao ).…”

Section: Introductionmentioning

confidence: 99%

Predicting the elastic response of organic‐rich shale using nanoscale measurements and homogenisation methods

Goodarzi

Rouainia

Aplin

et al. 2017

Geophysical Prospecting

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Block, M. (2017) 'Predicting the elastic response of organic-rich shale using nanoscale measurements and homogenisation methods.', Geophysical prospecting., 65 (6). pp. 1597-1614. Further information on publisher's website:https://doi.org/10.1111/ 1365-2478.12475 Publisher's copyright statement: This is the accepted version of the following article: Goodarzi, M., Rouainia, M., Aplin, A.C., Cubillas, P. and de Block, M. (2017), Predicting the elastic response of organic-rich shale using nanoscale measurements and homogenisation methods. Geophysical Prospecting., which has been published in nal form at https://doi.org/10.1111/1365-2478.12475. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving. Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractDetermination of the mechanical response of shales through experimental procedures is a practical challenge due to their heterogeneity and the practical difficulties of retrieving good quality core samples. Here, we investigate the possibility of using multi-scale homogenisation techniques to predict the macroscopic mechanical response of shales, based on quantitative mineralogical descriptions. We use the novel PeakForce Quantitative Nanomechanical Mapping (QNM ) technique to generate high resolution mechanical images of shales, allowing the response of porous clay, organic matter and mineral inclusions to be measured at the nanoscale. These observations support some of the assumptions previously made in the use of homogenisation methods to estimate the elastic properties of shale, and also earlier estimates of the mechanical properties of organic matter. We evaluate the applicability of homogenisation techniques against measured elastic responses of organic-rich shales, partly from published data and also from new indentation tests carried out in this work. Comparison of experimental values of the elastic constants of shale samples with those predicted by homogenisation methods showed that almost all predictions were within the standard deviation of experimental data. This suggests that the homogenisation approach is a useful way of estimating the elastic and mechanical properties of shales, in situations where conventional rock mechanics test data cannot be measured.

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“…For example, Hornby et al [18] assumed that the shale matrix consists of elliptical pores and elliptical isotropic elastic clay particles, and these elementary building blocks are the source of anisotropy. This idea has been adopted in some of the subsequent studies [20,50,44]. Ortega et al [33], on the other hand, implicitly considered the effect of the plate-like elements by a TI set of elastic constants for the solid unit of the matrix.…”

Section: Simplified Porous Matrix Micro-structurementioning

confidence: 99%

“…The material properties of the clay matrix, which consists of micronsize clay minerals and sub-micron-size voids, are difficult to quantify. Homogenisation methods have thus been used in conjunction with various assumptions to characterise the mechanical behaviour of both shales and the solid unit of clay [18,20,14,33,15,50,37,38,44]. Hornby et al [18] assumed elliptical clay particles and used the differential effective medium (DEM) approach to upscale shale properties.…”

Section: Introductionmentioning

confidence: 99%

Numerical evaluation of mean-field homogenisation methods for predicting shale elastic response

2016

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Numerical evaluation of mean-field homogenisation methods for predicting shale elastic responseReceived: date / Accepted: date Abstract Homogenisation techniques have been successfully used to estimate the mechanical response of synthetic composite materials, due to their ability to relate the macroscopic mechanical response to the material microstructure. The adoption of these mean-field techniques in geo-composites such as shales is attractive, partly because of the practical difficulties associated with the experimental characterisation of these highly heterogeneous materials. In this paper, numerical modelling has been undertaken to investigate the applicability of homogenisation methods in predicting the macroscopic, elastic response of clayey rocks. The rocks are considered as two-level composites consisting of a porous clay matrix at the first level and a matrix-inclusion morphology at the second level . The simulated microstructures ranged from a simple system of one inclusion/void embedded in a matrix to complex, random microstructures. The effectiveness and limitations of the different homogenisation schemes were demonstrated through a comparative evaluation of the macroscopic elastic response, illustrating the appropriate schemes for upscaling the microstructure of shales. Based on the numerical simulations and existing experimental observations, a randomly distributed pore system for the micro-structure of porous clay matrix has been proposed which can be used for the subsequent development and validation of shale constitutive models and their flow properties. Finally, the homogenisation techniques were used to predict the experimental measurements of elastic response. The developed methodology is proved to be a valuable too for verifying the accuracy and performance of the homogenisation techniques.

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Improved Rock-Physics Model for Shale Gas Reservoirs

Cited by 35 publications

References 6 publications

Rock-physics templates for clay-rich source rocks

Rock-physics templates for clay-rich source rocks

Predicting the elastic response of organic‐rich shale using nanoscale measurements and homogenisation methods

Numerical evaluation of mean-field homogenisation methods for predicting shale elastic response

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