Seismic inversion for organic richness and fracture gradient in unconventional reservoirs: Eagle Ford Shale, Texas

Hu, Robert; Vernik, Lev; Nayvelt, Lev; Alfred, Dicman

doi:10.1190/tle34010080.1

Cited by 46 publications

(7 citation statements)

References 5 publications

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“…The first part of this study is devoted to rock-physics screening of selected wells from the Norwegian Sea and North Sea. We will compare well-log data from the Kimmeridge Shale equivalent on the Norwegian Shelf with the wet-shale and hot-shale reference trends based on Khadeeva and Vernik (2014) and Hu et al (2015), respectively. Furthermore, we will try to explore for trends in the data and interpret those in terms of geologic parameters such as burial, composition, and maturation level.…”

Section: Rock-physics Screening and Burial-trend Analysismentioning

confidence: 99%

“…Løseth et al (2011) show that TOC content in source rocks can be quantified from acoustic impedance. Hu et al (2015) map organic richness of the Eagle Ford Shale from inversion data of acoustic impedance and shear impedance combined, based on rock-physics models. Bandyopadhyay et al (2012) demonstrate the ambiguities and uncertainties when characterizing organicrich shales, and they also include V P /V S and anisotropy to better quantify TOC from rock-physics models.…”

Section: Introductionmentioning

confidence: 99%

“…The inorganic shale trend represents conventional shale as defined by Vernik and Kachanov (2010) and was used by Khadeeva and Vernik (2014) as a reference trend. The organic-rich shale trend is based on the theory of Vernik and Milovac (2011) and was presented by Hu et al (2015), representing a shale with 7.5% TOC.…”

Section: Introductionmentioning

confidence: 99%

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Rock-physics analysis of clay-rich source rocks on the Norwegian Shelf

Avseth¹,

Carcione

2015

The Leading Edge

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Rock-physics trends and properties of clay-rich source rocks are investigated in selected wells in the North Sea and Norwegian Sea. Properties can vary significantly because of burial compaction, composition, diagenesis, organic richness, and maturation. The many competing effects can be difficult to disentangle in traditional rock-physics crossplots. However, nearly all the sourcerock data in the study are bounded nicely by linear trends that are based on rock-physics models, in acoustic-impedance (AI) versus shear-impedance (SI) crossplots. These reference models serve as a nice screening tool for organic richness and/or maturation level (i.e., hydrocarbon generation and expulsion), regardless of burial depth. The use of rock-physics templates for the early mature to mature stage of clay-rich source rocks is demonstrated by combining a simple basin-modeling approach with a rock-physics model using Backus average in which the organic-rich shale is represented by a transverse isotropic mixture of clays, kerogen, and hydrocarbons. The resulting templates are bounded nicely by reference trends and explain some of the observed trends in the data. However, the local presence of carbonaceous material and diagenesis within the source rock, which have not been accounted for in the rock-physics modeling, might explain why some of the data points have higher impedances and lower V P /V S than the template models. Finally, source rocks with hydrocarbon saturation can cause AVO signatures similar to hydrocarbon-filled sands and therefore represent false positives in exploration.

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Section: Rock-physics Screening and Burial-trend Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Rock-physics analysis of clay-rich source rocks on the Norwegian Shelf

Avseth¹,

Carcione

2015

The Leading Edge

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“…The general approach for estimating shear-wave velocity in conventional reservoir rocks and seals (e.g., Greenberg and Castagna, 1992;Vernik and Kachanov, 2010) is hardly capable of meaningful V S prediction in organic shales because it does not incorporate kerogen volume as an input variable. Hu et al (2015) suggest that in the Eagle Ford Shale, shearwave velocity logs can be empirically computed based on the separation between the loci of organic-rich marls and nonorganic encasing shales and carbonates in the V P /V S and acoustic versus shear-impedance spaces. Khadeeva and Vernik (2014) show that hydrocarbon fluid effect is secondary to kerogen content in determining the position of organic shales in AI-SI space.…”

Section: S Predictionmentioning

confidence: 99%

Constraining seismic rock-property logs in organic shale reservoirs

Yenugu

Vernik²

2015

The Leading Edge

Self Cite

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One of the major challenges of unconventional shale reservoirs is to understand the effects of organic richness (total organic carbon, TOC), mineralogy, microcracks, pore shape, and effective stress on elastic properties. The generation of petrophysical parameters, such as TOC, and quantification of total and organic porosities through a physically consistent petrophysical model are described. Rock-matrix density, which is a key parameter in determining total porosity, is estimated as a function of the amount of TOC and its level of maturity. Then the petrophysical parameters are used as inputs for rock-physics modeling to constrain the beddingnormal compressional-wave velocity as a function of various parameters (e.g., TOC, porosity, mineralogy, pore shapes, and microcrack density) in combination with effective stress. Modeling results on three shale plays from North America show that compressional-wave velocity in these specific formations is controlled mainly by variations in TOC, mineralogy, and pore shape. Shear-wave velocity in organic shales also was refined as a function of compressional-wave velocity and amount of TOC.

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“…Goodway et al (2010) discuss the anisotropy related to minimum closure stress in terms of γ (S) . Later, Hu et al (2015) relate similar concepts of pressure (stress) gradient to ε and δ. However, Thomsen (2013) has emphasized the importance of vertical polar anisotropy (VPA aka VTI) when estimating conventional elastic parameters such as incompressibility K, E and ν, and even the Lamé parameters λ and μ for characterizing frackability or brittleness.…”

Section: Aseg-pesa-aig 2016mentioning

confidence: 99%

P- and PS-wave vector wavefields for anisotropic petrophysics

Gaiser¹

2016

ASEG Extended Abstracts

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SUMMARYPredicting petrophysical properties of lithology, density and fractures using seismic data is an essential part of reservoir evaluation. In addition to lithology characterization, "frackability" has become a very important area of investigation for high-grading locations for drilling and hydraulic fracture stimulation. Most seismic studies that estimate P-and S-wave impedance, density and brittleness or formation strength use conventional P-wave data and isotropic elastic inversion methods. However, converted-wave (PS-wave) joint inversion and S-wave splitting methods have successfully been used to improve determination of seismic properties for shale plays as well as other unconventional resource plays.Anisotropic behaviour related to layered media (VTI), fracture properties, stress direction and the geomechanics of shales are increasingly more important for seismic analysis, imaging and reservoir characterization. Vector wavefields are sensitive to these properties and can help identify optimal drilling and stimulation locations. Also, it has been shown that use of conventional elastic parameters for characterizing "brittleness" should include anisotropic corrections to obtain a more accurate response. Including PSwave seismic data is beneficial for isotropic elastic inversion and should improve anisotropy estimates for identification of potential fracture locations.Elastic inversion of azimuthally anisotropic amplitude variations (AVAz) is also becoming more important. When layered media are fractured, orthorhombic symmetry of P-wave amplitude depends on S-wave birefringence. PS-waves are ideal for determining this Swave splitting information from layerstripping and their reflectivity provides additional equations for joint inversion with P-waves. Two coefficients, a radial R PSV and transverse R PSH reinforce anisotropic signatures similar to P-wave reflectivity R P . Vector wavefields contain all the necessary information for S-wave anisotropy from short wavelength AVAz as well as from long wavelength moveout behaviour.

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Seismic inversion for organic richness and fracture gradient in unconventional reservoirs: Eagle Ford Shale, Texas

Cited by 46 publications

References 5 publications

Rock-physics analysis of clay-rich source rocks on the Norwegian Shelf

Rock-physics analysis of clay-rich source rocks on the Norwegian Shelf

Constraining seismic rock-property logs in organic shale reservoirs

P- and PS-wave vector wavefields for anisotropic petrophysics

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