Rock Properties Seismic Modeling And 3c Seismic Analysis In The Bakken Shale North Dakota PDF Download

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Rock Properties, Seismic Modeling, and 3C Seismic Analysis in the Bakken Shale, North Dakota

Rock Properties, Seismic Modeling, and 3C Seismic Analysis in the Bakken Shale, North Dakota
Author: Andrea Gloreinaldy Paris Castellano
Publisher:
Total Pages:
Release: 2017
Genre: Geophysics
ISBN:
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A solid understanding of the factors that affect the seismic velocity and the amplitude variation with offset (AVO) is imperative for a reliable interpretation of seismic data and related prospect de‐risking. To understand the relationship between rock properties and their elastic response (i.e. velocity and density), petrophysical properties, rock‐physics, seismic modeling, and fluid substitution are analyzed. Seismic inversions and statistical predictions of rock properties are integrated to delimit prospective intervals and areas with high total organic carbon (TOC) content within the Bakken Formation, North Dakota. The shale intervals can be recognized by cross‐plotting well logs velocities versus density. The hydrocarbon potential is observed on logs as low densities, high gamma‐ray response, low P and S‐wave velocities, and high neutron porosities. Organicrich intervals with TOC content higher than 10 wt. % deviate from the ones that have lower TOC in the density domain, and exhibit slightly lower velocities, lower densities ( 2.3 g/cc), and a generally higher shale content ( 40%). Within the study area, Well V‐1 shows the highest TOC content, especially at the Upper Bakken depths with approximately 50% of clay volume. TOC is considered to be the principal factor affecting changes in density and P and S‐wave velocities in the Bakken shales. Vp/Vs ranges between 1.65 and 1.75. Synthetic seismic data are generated using the anisotropic version of Zoeppritz equations including estimated Thomsen parameters. For the tops of Upper and Lower Bakken, the amplitude becomes less negative with offset showing a negative intercept and a positive gradient which correspond to an AVO Class IV. A comparison between PP and PP‐PS joint inversions shows that the P‐impedance error decreases by 14% when incorporating the converted‐wave information in the inversion process. A statistical approach using multi‐attribute analysis and neural networks allows to delimit the zones of interest in terms of P‐impedance, density, TOC content, and brittleness. The inverted and predicted results show fair correlations with the original well logs. The integration between well‐log analysis, rock‐physics, seismic modeling, constrained inversions and statistical predictions contribute in identifying the vertical distribution of good reservoir quality areas within the Bakken Formation.

Rock-physics and 3C-3D Seismic Analysis for Reservoir Characterization

Rock-physics and 3C-3D Seismic Analysis for Reservoir Characterization
Author: Fabiola Del Valle Ruiz Pelayo
Publisher:
Total Pages:
Release: 2016
Genre: Geophysics
ISBN:
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The elastic properties (density and velocity) of organic shales are largely controlled by kerogen content, porosity, clay content, and e ective pressure. Since surface-seismic measurements can have a complicated dependence on rock properties, it is essential to understand the relationship between the elastic response and variations in rock properties to correctly assess the target reservoir. In this sense, a combination of rock-physics and seismic modeling is applied to relate variations in key properties, such as kerogen content and porosity, to di erences in the elastic response of a 3C-3D seismic volume in the Marcellus Shale (Bradford County, Pennsylvania). Well log analysis and rock physics modeling indicate that density is more sensitive to kerogen content than Vp/Vs or P impedance. Organic-rich intervals (kerogen content > 6 wt. %) are characterized by densities lower than 2.5 g/cc. Vp/Vs and P-impedance are more sensitive to variations in clay content than density; Vp/Vs values lower than 1.6 are attached to clay content lower than 25 %. The interplay between mineralogy and kerogen content causes an increase in velocity in the organic-rich interval, where the e ect of kerogen on the elastic moduli seems to be masked by a decrease in clay content and increase in quartz and calcite. Elastic AVA modeling shows that the sensitivity to the presence of the organic-rich facies increases with angle for both PP and PS (converted-wave) reflections. Additionally, the compressibility seems to be more sensitive to the organic-rich facies than the rigidity. A comparison between PP and PP-PS inversions show that the addition of PS data decreases the P-impedance, S-impedance and density estimation errors by 58, 80, and 17 %, respectively. We used this procedure to create 3D-density maps to indicate promising reservoir quality. These predictions suggest good reservoirs where two gas wells (not used in the analysis) are producing.

Seismic Reservoir Characterization of the Haynesville Shale

Seismic Reservoir Characterization of the Haynesville Shale
Author: Meijuan Jiang
Publisher:
Total Pages: 0
Release: 2014
Genre:
ISBN:
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This dissertation focuses on interpreting the spatial variations of seismic amplitude data as a function of rock properties for the Haynesville Shale. To achieve this goal, I investigate the relationships between the rock properties and elastic properties, and calibrate rock-physics models by constraining both P- and S-wave velocities from well log data. I build a workflow to estimate the rock properties along with uncertainties from the P- and S-wave information. I correlate the estimated rock properties with the seismic amplitude data quantitatively. The rock properties, such as porosity, pore shape and composition, provide very useful information in determining locations with relatively high porosities and large fractions of brittle components favorable for hydraulic fracturing. Here the brittle components will have the fractures remain opened for longer time than the other components. Porosity helps to determine gas capacity and the estimated ultimate recovery (EUR); composition contributes to understand the brittle/ductile strength of shales, and pore shape provides additional information to determine the brittle/ductile strength of the shale. I use effective medium models to constrain P- and S-wave information. The rock-physics model includes an isotropic and an anisotropic effective medium model. The isotropic effective medium model provides a porous rock matrix with multiple mineral phases and pores with different aspect ratios. The anisotropic effective medium model provides frequency- and pore-pressure-dependent anisotropy. I estimate the rock properties with uncertainties using grid searching, conditioned by the calibrated rock-physics models. At well locations, I use the sonic log as input in the rock-physics models. At areas away from the well locations, I use the prestack seismic inverted P- and S-impedances as input in the rock-physics models. The estimated rock properties are correlated with the seismic amplitude data and help to interpret the spatial variations observed from seismic data. I check the accuracy of the estimated rock properties by comparing the elastic properties from seismic inversion and the ones derived from estimated rock properties. Furthermore, I link the estimated rock properties to the microstructure images and interpret the modeling results using observations from microstructure images. The characterization contributes to understand what causes the seismic amplitude variations for the Haynesville Shale. The same seismic reservoir characterization procedure could be applied to other unconventional gas shales.

3-D Seismic Interpretation

3-D Seismic Interpretation
Author: M. Bacon
Publisher: Cambridge University Press
Total Pages: 228
Release: 2003-08-21
Genre: Science
ISBN: 9780521792035
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Table of contents

Seismic and Rockphysics Diagnostics of Multiscale Reservoir Textures

Seismic and Rockphysics Diagnostics of Multiscale Reservoir Textures
Author:
Publisher:
Total Pages:
Release: 2004
Genre:
ISBN:
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As part of our study on ''Relationships between seismic properties and rock microstructure'', we have continued our work on analyzing shale textures from scanning acoustic microscope images. Our analysis is now extended to over 280 images of shales, giving us better statistics. The shales cover a range of depths and maturity. We estimate different statistical measures for characterizing heterogeneity and textures from scanning acoustic microscope (SAM) images of shale microstructures. Characterizing and understanding the microgeometry, their textures, scales, and textural anisotropy is important for better understanding the role of microgeometry on effective elastic properties. We analyzed SAM images from Bakken shale, Bazhenov shale, and Woodford shale. We observed quantifiable and consistent patterns linking texture, shale maturity, and elastic P-wave impedance. The textural heterogeneity and P-wave impedance increase with increasing maturity (decreasing kerogen content), while there is a general decrease in textural anisotropy with maturity. We also found a reasonably good match between elastic impedance estimated from SAM images and impedance computed from ultrasonic measurements.

Multicomponent 3D Seismic Interpretation of the Marcellus Shale Bradford County, Pennsylvania

Multicomponent 3D Seismic Interpretation of the Marcellus Shale Bradford County, Pennsylvania
Author: Mouna Gargouri
Publisher:
Total Pages:
Release: 2012
Genre: Geophysics
ISBN:
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High spatial variability of petrophysical and petrochemical properties of the Marcellus formation was reported by Hill et al. (2002). This creates a major challenge in reservoir characterization with conventional seismic data. An investigation into the potential of integrated compressional P-wave and converted-wave seismic interpretation, to help characterize geological properties of the Devonian Marcellus shale, has been conducted based on the 3C-3D data set acquired. Synthetic and real seismic data have been used to conduct this evaluation. Interval Vp/Vs analysis has been performed and the Poisson's ratio was generated to map lateral changes in lithology and rock properties. Sweet spots are interpreted to area with high quartz, an anomalous low Vp/Vs. The Vp/Vs Marcellus map shows the lateral lithological variability and therefore brittle areas. An inversion was run for the compressional P and the converted PS sections to examine the anomalies observed within the Vp/Vs map. The anomalies distinguished within the Vp/Vs map were noticeable in the inversion sections. The inversion was followed by a seismic attribute analysis to understand the distribution of fractures. The curvature and the coherency attributes delivered highly fractured area and major faults. This study documents the results of an integrated workflow of seismic interpretation, seismic inversion and seismic attribute analysis. It illustrates the potential of the Vp/Vs analysis to discriminate between shale-rich and sand-rich material and the ability of the curvature and coherency attribute to potentially highlight zones of intense fracturing.

Anisotropic Seismic Characterization of the Eagle Ford Shale

Anisotropic Seismic Characterization of the Eagle Ford Shale
Author: Qi Ren
Publisher:
Total Pages: 214
Release: 2016
Genre:
ISBN:
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Quantitative reservoir characterization using integrated seismic data and well log data is important in sweet spot identification, well planning, and reservoir development. The process includes building up the relations between rock properties and elastic properties through rock physics modeling, inverting for elastic properties from seismic data, and inverting for rock properties from both seismic data and rock physics models. Many quantitative reservoir characterization techniques have been developed for conventional reservoirs. However, challenges remain when extending these methods to unconventional reservoirs because of their complexity, such as anisotropy, micro-scale fabric, and thin beds issues. This dissertation focuses on developing anisotropic rock physics modeling method and seismic inversion method that are appliable for unconventional reservoir characterization. The micro-scale fabric, including the complex composition, shape and alignment of clay minerals, pore space, and kerogen, significantly influences the anisotropic elastic properties. I developed a comprehensive three-step rock-physics approach to model the anisotropic elastic properties, accounting for the micro-scale fabric. In addition, my method accounts for the different pressure-dependent behaviors of P-waves and S-waves. The modeling provides anisotropic stiffnesses and pseudo logs of anisotropy parameters. The application of this method on the Upper Eagle Ford Shale shows that the clay content kerogen content and porosity decrease the rock stiffness. The anisotropy increases with kerogen content, but the influence of clay content is more complex. Comparing the anisotropy parameter pseudo logs with clay content shows that clay content increases the anisotropy at small concentrations; however, the anisotropy stays constant, or even slightly decreases, as clay content continues to increase. Thin beds and anisotropy are two important limitation of the application of seismic characterization on unconventional reservoirs. I introduced the geostatistics into stochastic seismic inversion. The geostatistical models, based on well log data, simulate small-scale vertical variations that are beyond seismic resolution. This additional information compensates the seismic data for its band-limited nature. I applied this method on the Eagle Ford Shale, using greedy annealing importance sampling as inversion algorithm. The thin Lower Eagle Ford Formation, which cannot be resolved by conventional inversion method, is clearly resolved in the inverted impedance volume using my method. In addition, because anisotropy is accounted for in the forward modeling, the accuracy of inverted S-impedance is significantly improved.

A Fracture and Texture Analysis of the Bakken Formation, Montana

A Fracture and Texture Analysis of the Bakken Formation, Montana
Author: Eric Joseph Easley
Publisher:
Total Pages: 356
Release: 2014
Genre: Bakken Formation
ISBN:
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The Bakken Formation underlies much of eastern Montana, North Dakota and Saskatchewan, with correlative units extending in the subsurface beyond these regions. It is composed of three informal members: an upper shale member, a middle silty limestone/dolostone member, and a lower shale member. The Bakken petroleum system acts as a conventional and unconventional reservoir within the Williston Basin and fractures that occur naturally within the Bakken petroleum system can either help or hinder reservoir characteristics. Unconventional reservoirs, such as the Bakken Formation, rely heavily on fracture enhancement (hydraulic fracturing) to become producible oil plays. Pre-existing fractures and weaknesses open more readily with fracture stimulation than the creation of new fractures, and have been correlated to increased early production in shale plays. To determine the influence of these fractures on the reservoir in the Bakken Formation and its correlative units, fractures in core and outcrop were examined. Clay-rich shales, such as those within the Bakken Formation, display high intrinsic anisotropy, which can be helpful in interpreting seismic profiles. Despite the importance of shale oil reservoirs, the contribution of preferred orientation of minerals to shales is not well constrained. These constituent clay minerals are phyllosilicates that acquire preferred orientation during sedimentation and early diagenesis. Hard X-rays produced from a synchrotron source are effective at extracting orientation distributions of individual mineral components within a shale. Crystallographic preferred orientation can be determined through synchrotron X-ray diffraction and the interpretation of three-dimensional images by using a Rietveld refinement method. This method incorporates a least squares approach to produce a calculated model of the degree of preferred orientation. Samples of the Bakken shales from wells in North Dakota and Montana, and outcrops from southwestern Montana were investigated. Individual phyllosilicate minerals such as illite, smectite, muscovite, and chlorite yield individual orientation patterns. The elastic properties of each shale sample were determined by averaging the calculated properties of each mineral phase over their orientation distributions. The presence of specific clay minerals and degree of anisotropy is highly variable from well to well. A better understanding of shale anisotropy could help improve exploration and production of unconventional shale oil reservoirs.