Orthorhombic model for geomechanical applications in unconventional shale reservoirs

Far, Mehdi E.; Quirein, John; Mekic, Natasa

doi:10.1190/segam2015-5902954.1

Cited by 5 publications

(1 citation statement)

References 3 publications

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“…We conducted this study in the formation where the dominant lithology is shale. Grain distribution pattern shows that the orthorhombic nature is present in the shale section (Far et al 2015); however, in our study, we observed significant changes under the vertical transverse isotropy (VTI) condition.…”

Section: Introductioncontrasting

confidence: 78%

Velocity anisotropy analysis for shale lithology of the complex geological section in Jaisalmer sub-basin, India

2019

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Section: Introductioncontrasting

confidence: 78%

Velocity anisotropy analysis for shale lithology of the complex geological section in Jaisalmer sub-basin, India

2019

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Estimation of in situ stresses from PP-wave azimuthal seismic data in fracture-induced anisotropic media

et al. 2022

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Horizontally transverse isotropy (HTI) induced by vertical or subvertical, aligned fractures is common for unconventional fractured porous shale oil or gas reservoirs. Compared with the unfractured rocks, the seismic response characteristics of PP-wave azimuthal amplitudes are usually disturbed by the fractures and the in-situ stresses. Knowledge of fracture properties, as well as in-situ stresses, is required to optimize horizontal well planning and hydraulic fracturing during production, and seismic inversion for in-situ stresses from the PP-wave azimuthal amplitude data in fracture-induced anisotropic media is an essential step. Using the linear-slip theory and the effective stress law, we derive the fluid-saturated effective elastic stiffness tensors parameterized by background elastic moduli, the effective stress coefficient of isotropic host rocks, fluid modulus, porosity, and fracture parameters based on the anisotropic Gassmanns fluid substitution equation. Combining the perturbations in saturated stiffness tensors and scattering theory, we formulate the reflection coefficient equation of PP-wave data as a function of background porosity-related stress parameter, and two (i.e., normal and shear) fracture weakness parameters. Following Bayes rule, we estimate the porosity-related stress parameter and fracture weaknesses using the inversion method of azimuthal Fourier coefficients. We finally compute the effective horizontal and vertical in-situ stresses using the estimated elastic moduli, porosity-related stress parameter and fracture weaknesses. Synthetic and real data sets demonstrate that our proposed inversion approach based on the derived reflection equation provides us another way to obtain reasonable estimates of in-situ stresses in a complex fractured porous shale reservoir.

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A novel rock-physics model of organic-rich shale considering maturation influence

Yang,

Chen

2024

GEOPHYSICS

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Geochemical parameters, e.g. maturity, and total organic carbon (TOC) content, play a crucial role in the prediction of sweet spots and the exploration of oil and gas in organic-rich shales. Thermal maturity significantly affects the conversion of solid organic matter (OM) into hydrocarbons and the evolution of microstructures, thereby altering the overall elastic properties of shales. To clarify how the maturity affects shale property, we propose a novel Rock Physics Model (RPM) of organic-rich shale, in which we consider the continuous process of thermal maturity.#xD;Firstly, we present how to estimate maturity level, TOC content, and organic porosity using logging data. Secondly, different from only considering the discrete-stage maturity, we establish a novel RPM, in which a continuous kerogen maturation process serves as a key control condition. Furthermore, we propose how to calibrate the volumetric proportion of each porosity type as a function of maturation. Finally, we apply the RPM to investigate how sweet spot parameters (thermal maturity, TOC content, and brittle mineral content), overpressure and diagenesis affect the overall elastic properties and anisotropy of shale. Results demonstrate that using the proposed RPM we may predict acoustic velocity of shale formations reliably, and kerogen evolution has a noticeable impact on the elastic properties of shale rocks, particularly during the wet gas window stage of mid-to-high maturation. We conclude that thermal maturity emerges as a crucial sweet spot parameter in the case of exploration of oil and gas in organic-rich shales.

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Orthorhombic model for geomechanical applications in unconventional shale reservoirs

Cited by 5 publications

References 3 publications

Velocity anisotropy analysis for shale lithology of the complex geological section in Jaisalmer sub-basin, India

Velocity anisotropy analysis for shale lithology of the complex geological section in Jaisalmer sub-basin, India

Estimation of in situ stresses from PP-wave azimuthal seismic data in fracture-induced anisotropic media

A novel rock-physics model of organic-rich shale considering maturation influence

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