Model-based amplitude versus offset and azimuth inversion for estimating fracture parameters and fluid content

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. M1-M17 ◽  
Author(s):  
Jiao Xue ◽  
Hanming Gu ◽  
Chengguo Cai
Keyword(s):  
Seismic Data ◽  
Shear Fracture ◽  
Influencing Factor ◽  
Fractured Reservoirs ◽  
Fracture Density ◽  
Inversion Algorithm ◽  
Fluid Content ◽  
Fracture Parameters ◽  
Amplitude Versus Offset ◽  
Amplitude Versus

The normal-to-shear fracture compliance ratio is commonly used as a fluid indicator. In the seismic frequency range, the fluid indicator lies between the values for isolated fluid-filled fractures and dry fractures, and it is not easy to discriminate the fluid content. Assuming that the fracture surfaces are smooth, we use [Formula: see text], with [Formula: see text] and [Formula: see text] representing the normal fracture weakness of the saturated and dry rock, to indicate fluid types, and to define a fluid influencing factor. The fluid influencing factor is sensitive to the fluid properties, the aspect ratio of the fractures, and the frequency. Conventionally, the amplitude versus offset and azimuth (AVOA) inversion is formulated in terms of the contrasts of the fracture weaknesses across the interface, assuming that the fractures are vertical with the same symmetry axis. We consider fractures with arbitrary azimuths, and develop a method to estimate fracture parameters from wide-azimuth seismic data. The proposed AVOA inversion algorithm is tested on real 3D prestack seismic data from the Tarim Basin, China, and the inverted fracture density show good agreement with well log data, except that there are some discrepancies for one of the fractured reservoir sections. The discrepancies can be ascribed to neglect of the dip angle for the tilted fractures and the conjugate fracture sets, and to the validity of the linear-slip model. The fractured reservoirs are expected to be liquid saturated, under the assumption of smooth fractures. Overall, the inverted fracture density and fluid influencing factor can be potentially used for better well planning in fractured reservoirs and quantitatively estimating the fluid effects.

Effects of fractures on NMO velocities and P‐wave azimuthal AVO response

Geophysics ◽  
2002 ◽  
Vol 67 (3) ◽  
pp. 711-726 ◽  
Author(s):  
Feng Shen ◽  
Xiang Zhu ◽  
M. Nafi Toksöz
Keyword(s):  
Aspect Ratio ◽  
Fractured Reservoirs ◽  
Crack Density ◽  
P Wave ◽  
Fractured Reservoir ◽  
Fracture Density ◽  
Fracture Detection ◽  
Fluid Content ◽  
Fracture Parameters ◽  
Fractured Medium

This paper attempts to explain the relationships between fractured medium properties and seismic signatures and distortions induced by geology‐related influences on azimuthal AVO responses. In the presence of vertically aligned fractures, the relationships between fracture parameters (fracture density, fracture aspect ratio, and saturated fluid content) and their seismic signatures are linked with rock physics models of fractured media. The P‐wave seismic signatures studied in this paper include anisotropic parameters (δ(v), (v), and γ(v)), NMO velocities, and azimuthal AVO responses, where δ(v) is responsible for near‐vertical P‐wave velocity variations, (v) defines P‐wave anisotropy, and γ(v) governs the degree of shearwave splitting. The results show that in gas‐saturated fractures, anisotropic parameters δ(v) and (v) vary with fracture density alone. However, in water‐saturated fractures δ(v) and (v) depend on fracture density and crack aspect ratio and are also related to Vp/VS and Vp of background rocks, respectively. Differing from δ(v) and (v), γ(v) is the parameter most related to crack density. It is insensitive to the saturated fluid content and crack aspect ratio. The P‐wave NMO velocities in horizontally layered media are a function of δ(v), and their properties are comparable with those of δ(v). Results from 3‐D finite‐difference modeling show that P‐wave azimuthal AVO variations do not necessarily correlate with the magnitude of fracture density. Our studies reveal that, in addition to Poisson's ratio, other elastic properties of background rocks have an effect on P‐wave azimuthal AVO variations. Varying the saturated fluid content of fractures can lead to azimuthal AVO variations and may greatly change azimuthal AVO responses. For a thin fractured reservoir, a tuning effect related to seismic wavelength and reservoir thickness can result in variations in AVO gradients and in azimuthal AVO variations. Results from instantaneous frequency and instantaneous bandwidth indicate that tuning can also lead to azimuthal variations in the rates of changes of the phase and amplitude of seismic waves. For very thin fractured reservoirs, the effect of tuning could become dominant. Our numerical results show that AVO gradients may be significantly distorted in the presence of overburden anisotropy, which suggests that the inversion of fracture parameters based on an individual AVO response would be biased unless this influence were corrected. Though P‐wave azimuthal AVO variations could be useful for fracture detection, the combination of other types of data is more beneficial than using P‐wave amplitude signatures alone, especially for the quantitative characterization of a fractured reservoir.

Fault whispers: Transmission distortions on prestack seismic reflection data

Geophysics ◽  
2000 ◽  
Vol 65 (2) ◽  
pp. 377-389 ◽  
Author(s):  
Paul J. Hatchell
Keyword(s):  
Seismic Data ◽  
Seismic Waves ◽  
Shallow Gas ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Amplitude Versus Offset ◽  
Velocity Changes ◽  
Transmission Distortions ◽  
Amplitude Versus ◽  
Buried Faults

Transmission distortions are observed on prestack seismic data at two locations in the Gulf of Mexico. These distortions produce anomalous amplitude versus offset (AVO) signatures. The locations of the distortion zones are determined using acquisition geometry and ray tracing. No obvious reflection events, such as shallow gas zones, are observed at the predicted locations of the distortion zones. Instead, the distortion zones correlate with buried faults and unconformities. It is postulated that the distortions are produced by velocity changes across buried faults and unconformities. The distortions result from an interference pattern resulting from seismic waves arriving from different sides of the faults. A simple model is developed to explain many of the characteristics of the distortion pattern.

Amplitude preservation of Radon-based multiple-removal filters

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. V123-V126 ◽  
Author(s):  
Ethan J. Nowak ◽  
Matthias G. Imhof
Keyword(s):  
Radon Transform ◽  
Seismic Data ◽  
Transform Domain ◽  
Multiple Reflections ◽  
Avo Analysis ◽  
Amplitude Versus Offset ◽  
Amplitude Preservation ◽  
Amplitude Versus

This study examines the effect of filtering in the Radon transform domain on reflection amplitudes. Radon filters are often used for removal of multiple reflections from normal moveout-corrected seismic data. The unweighted solution to the Radon transform reduces reflection amplitudes at both near and far offsets due to a truncation effect. However, the weighted solutions to the transform produce localized events in the transform domain, which minimizes this truncation effect. Synthetic examples suggest that filters designed in the Radon domain based on a weighted solution to the linear, parabolic, or hyperbolic transforms preserve the near- and far-offset reflection amplitudes while removing the multiples; whereas the unweighted solutions diminish reflection amplitudes which may distort subsequent amplitude-versus-offset (AVO) analysis.

scholarly journals Analisis AVO untuk Mengetahui Penyebaran Hidrokarbon Berdasarkan Faktor Fluida (Studi Kasus Lapangan “H” Formasi Talang Akar Cekungan Jawa Barat Utara)

2016 ◽  
Vol 3 (02) ◽  
pp. 209
Author(s):  
Muhammad Nur Handoyo ◽  
Agus Setyawan ◽  
Mualimin Muhammad
Keyword(s):  
Seismic Data ◽  
Class Iii ◽  
Avo Inversion ◽  
Amplitude Versus Offset ◽  
Attribute Analysis ◽  
Fluid Factor ◽  
Inversion Analysis ◽  
Amplitude Versus

<span>Amplitude versus offset (AVO) inversion analysis can be used to determine the spread of <span>hydrocarbons on seismic data. In this study we conducted AVO on reservoir layer Talang <span>Akar’s formation (TAF). AVO inversion results are angle stack, normal incident reflectivity <span>(intercept), gradient and fluid factor. Angle stack attribute analysis showed an AVO anomaly <span>in the reservoir TAF layer, amplitude has increased negative value from near angle stack to far <span>angle stack. The result of crossplot normal incident reflectivity (intercept) with gradient <span>indicates reservoir TAF layer including Class III AVO anomaly. While the analysis of fluid <span>factor attribute has a negative value thus reservoir TAF layer indicates a potential <span>hydrocarbon.</span></span></span></span></span></span></span></span><br /></span>

scholarly journals An integrated petrophysical-based wedge modeling and thin bed AVO analysis for improved reservoir characterization of Zhujiang Formation, Huizhou sub-basin, China: A case study

2020 ◽  
Vol 12 (1) ◽  
pp. 256-274
Author(s):  
Wasif Saeed ◽  
Hongbing Zhang ◽  
Qiang Guo ◽  
Aamir Ali ◽  
Tahir Azeem ◽  
...  
Keyword(s):  
Seismic Data ◽  
Reservoir Characterization ◽  
Dominant Frequency ◽  
Well Logs ◽  
Amplitude Versus Offset ◽  
Avo Attributes ◽  
Thin Reservoir ◽  
Amplitude Versus

AbstractThe main reservoir in Huizhou sub-basin is Zhujiang Formation of early Miocene age. The petrophysical analysis shows that the Zhujiang Formation contains thin carbonate intervals, which have good hydrocarbon potential. However, the accurate interpretation of thin carbonate intervals is always challenging as conventional seismic interpretation techniques do not provide much success in such cases. In this study, well logs, three-layer forward amplitude versus offset (AVO) model and the wedge model are integrated to analyze the effect of tuning thickness on AVO responses. It is observed that zones having a thickness greater than or equal to 15 m can be delineated with seismic data having a dominant frequency of more than 45 Hz. The results are also successfully verified by analyzing AVO attributes, i.e., intercept and gradient. The study will be helpful to enhance the characterization of thin reservoir intervals and minimize the risk of exploration in the Huizhou sub-basin, China.

Monitoring CO2saturation using time-lapse amplitude versus offset analysis of 3D seismic data from the Ketzin CO2storage pilot site, Germany

2018 ◽  
Vol 66 (8) ◽  
pp. 1568-1585
Author(s):  
Monika Ivandic ◽  
Peter Bergmann ◽  
Juliane Kummerow ◽  
Fei Huang ◽  
Christopher Juhlin ◽  
...  
Keyword(s):  
Seismic Data ◽  
Time Lapse ◽  
3D Seismic ◽  
Pilot Site ◽  
Amplitude Versus Offset ◽  
3D Seismic Data ◽  
Amplitude Versus

The Paleozoic prospectivity of the Browse Basin, Australia

2020 ◽  
Vol 60 (2) ◽  
pp. 685
Author(s):  
Said Amiribesheli ◽  
Joshua Thorp ◽  
Julia Davies
Keyword(s):  
Seismic Data ◽  
Inversion Algorithm ◽  
Reservoir Properties ◽  
Depth Migration ◽  
Canning Basin ◽  
Petroleum Systems ◽  
Amplitude Versus Offset ◽  
Long Offset ◽  
Well Data

Most of the discovered hydrocarbons in the Browse Basin occurred within the Mesozoic intervals, while deeper Paleozoic sequences have been seldom explored. Lack of Paleozoic exploration in the Browse Basin has been attributed to the lack of well penetrations, poor understanding of the petroleum systems and paucity of seismic data. The onshore Canning Basin with several commercial fields and discoveries is the most appropriate analogue for understanding the Paleozoic sequences in the region. With the integration of geophysical data (i.e. gravity, magnetic and seismic), well data and geology, the Paleozoic prospectivity of the Browse Basin can be further enlightened. Modern long offset (8 m) Vampire 2D seismic data were acquired by Searcher to address some of the complex challenges in the Browse Basin. Reservoir quality of the Brewster Formation, volcanic discrimination within the Plover Formation and identification of deeper Triassic and Paleozoic plays are some examples of these challenges in the Browse Basin. Recently Searcher reprocessed this regionally important Vampire 2D seismic dataset that ties to 60 wells. The broadband pre-stack depth migration reprocessed data were inverted to extract three petro-elastic properties of acoustic impedance, Vp/Vs and density by three-term amplitude versus offset inversion algorithm to improve imaging of deeper plays and delineate reservoir properties. This paper discusses how several potential Paleozoic reservoir-seal pairs can be identified in the Browse Basin by utilising the integration of Vampire 2D seismic data, quantitative interpretation products, regional geology and knowledge of the Canning Basin’s fields and discoveries. Previously there was little exploration of Paleozoic plays because they could not be imaged on seismic data. The potential Paleozoic reservoirs identified in this study include Permo-Carboniferous subcrop, Carboniferous-Devonian anticline and Carboniferous-Devonian rollover plays.

scholarly journals Lithology and fluid prediction from amplitude versus offset (AVO) seismic data

Geofluids ◽  
2003 ◽  
Vol 3 (4) ◽  
pp. 219-232 ◽  
Author(s):  
D. J. Davies ◽  
A. Mcinalley ◽  
F. Barclay
Keyword(s):  
Seismic Data ◽  
Amplitude Versus Offset ◽  
Amplitude Versus
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