Fracture mapping from azimuthal velocity analysis using 3D surface seismic data

A horizontal well is most productive in tight reservoirs when it intersects a large number of vertical fractures, yet strata near the borehole remain mechanically stable. Azimuthal velocity analysis and P-wave amplitude versus offset (AVO) using 3D wide-azimuth prestack surface seismic data provide a remote yet detailed way to map a fracture pattern away from well control. We estimate fracture direction and relative fracture intensity from such data at two gas fields in Saudi Arabia. Our results show a small azimuthal variation in P-wave velocity (maximum 5%) and a larger variation in azimuthal AVO at the reservoir (larger than 100%). Computed fracture attributes for field 1 show a consistent east-west fracture direction. However, in field 2, fracture azimuth is variable but generally east-west and north-south, with the strongly anisotropic north-south orientation correlating with faults and areas of large structural curvature in the reservoir. In both fields, azimuthal AVO analysis shows a more consistent estimate of fracture orientation than velocity analysis. These estimates have been instrumental in planning prolific and safe horizontal wells

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Improving The Reliability of Velocity Analysis of Shallow Seismic Data

10.3997/2214-4609.202152103 ◽

2021 ◽

Author(s):

A.G. Yaroslavtsev ◽

M.V. Tarantin ◽

T.V. Baibakova

Keyword(s):

Seismic Data ◽

Velocity Analysis ◽

Shallow Seismic

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Study on the Velocity Analysis Method of Low SNR Seismic Data

Energy and Environment Research ◽

10.5539/eer.v11n1p78 ◽

2021 ◽

Vol 11 (1) ◽

pp. 78

Author(s):

Jianbo He ◽

Zhenyu Wang ◽

Mingdong Zhang

Keyword(s):

Seismic Data ◽

Fresnel Zone ◽

Signal To Noise Ratio ◽

Normal Wave ◽

Curvature Radius ◽

Velocity Spectrum ◽

Velocity Analysis ◽

Signal To Noise ◽

Noise Ratio ◽

Zero Offset

When the signal to noise ratio of seismic data is very low, velocity spectrum focusing will be poor., the velocity model obtained by conventional velocity analysis methods is not accurate enough, which results in inaccurate migration. For the low signal noise ratio (SNR) data, this paper proposes to use partial Common Reflection Surface (CRS) stack to build CRS gathers, making full use of all of the reflection information of the first Fresnel zone, and improves the signal to noise ratio of pre-stack gathers by increasing the number of folds. In consideration of the CRS parameters of the zero-offset rays emitted angle and normal wave front curvature radius are searched on zero offset profile, we use ellipse evolving stacking to improve the zero offset section quality, in order to improve the reliability of CRS parameters. After CRS gathers are obtained, we use principal component analysis (PCA) approach to do velocity analysis, which improves the noise immunity of velocity analysis. Models and actual data results demonstrate the effectiveness of this method.

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Velocity analysis of multicomponent seismic data of the Santos Basin using OBN technology and SWD technique

Far East Hydrocarbons 2016 ◽

10.3997/2214-4609.201602315 ◽

2016 ◽

Author(s):

N.R.C.F. Zuniga

Keyword(s):

Seismic Data ◽

Velocity Analysis ◽

Multicomponent Seismic

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Imaging seismic anisotropy in a shale gas reservoir by combining microseismic and 3D surface reflection seismic data

79th EAGE Conference and Exhibition 2017 - Workshops ◽

10.3997/2214-4609.201701689 ◽

2017 ◽

Author(s):

W. Gajek ◽

J. Verdon ◽

M. Malinowski ◽

J. Trojanowski

Keyword(s):

Shale Gas ◽

Seismic Data ◽

Seismic Anisotropy ◽

Gas Reservoir ◽

Surface Reflection ◽

Reflection Seismic ◽

Shale Gas Reservoir ◽

3D Surface

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New Workflow for Estimating Seismic Wave Attenuation from 3D Surface Seismic Data

10.3997/2214-4609.2019x604036 ◽

2019 ◽

Author(s):

F. Bouchaala ◽

M.Y. Ali ◽

J. Matsushima ◽

Y. Bouzidi ◽

E.M. Takam Takougang ◽

...

Keyword(s):

Seismic Wave ◽

Seismic Data ◽

Wave Attenuation ◽

Seismic Wave Attenuation ◽

3D Surface

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2-D continuation operators and their applications

Geophysics ◽

10.1190/1.1444100 ◽

1996 ◽

Vol 61 (6) ◽

pp. 1846-1858 ◽

Cited By ~ 31

Author(s):

Claudio Bagaini ◽

Umberto Spagnolini

Keyword(s):

Seismic Data ◽

Real Data ◽

Integral Form ◽

Amplitude Distribution ◽

Velocity Model ◽

Velocity Analysis ◽

Seismic Data Processing ◽

Analysis Method ◽

Standard Tool ◽

Zero Offset

Continuation to zero offset [better known as dip moveout (DMO)] is a standard tool for seismic data processing. In this paper, the concept of DMO is extended by introducing a set of operators: the continuation operators. These operators, which are implemented in integral form with a defined amplitude distribution, perform the mapping between common shot or common offset gathers for a given velocity model. The application of the shot continuation operator for dip‐independent velocity analysis allows a direct implementation in the acquisition domain by exploiting the comparison between real data and data continued in the shot domain. Shot and offset continuation allow the restoration of missing shot or missing offset by using a velocity model provided by common shot velocity analysis or another dip‐independent velocity analysis method.

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Can fracture orientation and intensity be detected from seismic data? Woodford Formation, Anadarko Basin, Oklahoma investigation

The Leading Edge ◽

10.1190/tle38020144.1 ◽

2019 ◽

Vol 38 (2) ◽

pp. 144-150 ◽

Cited By ~ 5

Author(s):

Marianne Rauch-Davies ◽

David Langton ◽

Michael Bradshaw ◽

Allon Bartana ◽

Dan Kosloff ◽

...

Keyword(s):

Seismic Data ◽

Subsurface Layer ◽

Azimuthal Velocity ◽

Natural Fracture ◽

Woodford Shale ◽

Data Set ◽

Anadarko Basin ◽

Fracture Orientation ◽

Anisotropic Elastic ◽

Elastic Simulation

With readily available wide-azimuth, onshore, 3D seismic data, the search for attributes utilizing the azimuthal information is ongoing. Theoretically, in the presence of ordered fracturing, the seismic wavefront shape changes from spherical to nonspherical with the propagation velocity being faster parallel to the fracturing and slower perpendicular to the fracture direction. This concept has been adopted and is used to map fracture direction and density within unconventional reservoirs. More specifically, azimuthal variations in normal moveout velocity or migration velocity are often used to infer natural fracture orientation. Analyses of recent results have called into question whether azimuthal velocity linked to intrinsic azimuthal velocity variations can actually be detected from seismic data. By use of 3D orthorhombic anisotropic elastic simulation, we test whether fracture orientation and intensity can be detected from seismic data. We construct two subsurface models based on interpreted subsurface layer structure of the Anadarko Basin in Oklahoma. For the first model, the material parameters in the layers are constant vertically transverse isotropic (VTI) in all intervals. The second model was constructed the same way as the base model for all layers above the Woodford Shale Formation. For the shale layer, orthorhombic properties were introduced. In addition, a thicker wedge layer was added below the shale layer. Using the constructed model, synthetic seismic data were produced by means of 3D anisotropic elastic simulation resulting in two data sets: VTI and orthorhombic. The simulated data set was depth migrated using the VTI subsurface model. After migration, the residual moveouts on the migrated gathers were analyzed. The analysis of the depth-migrated model data indicates that for the typical layer thicknesses of the Woodford Shale layer in the Anadarko Basin, observed and modeled percentage of anisotropy and target depth, the effect of intrinsic anisotropy is too small to be detected in real seismic data.

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