Incomplete AVO near salt structures

Geophysics ◽  
1992 ◽  
Vol 57 (4) ◽  
pp. 543-553 ◽  
Author(s):  
Christopher P. Ross
Keyword(s):  
Seismic Profiles ◽  
Spectral Modeling ◽  
Signal Degradation ◽  
Amplitude Versus Offset ◽  
Bright Spots ◽  
Close Proximity ◽  
Pseudo Spectral ◽  
Amplitude Versus ◽  
Structure Class ◽  
Made In

Amplitude versus offset (AVO) measurements for deep hydrocarbon‐bearing sands can be compromised when made in close proximity to a shallow salt piercement structure. Anomalous responses are observed, particularly on low acoustic impedance bright spots. CMP data from key seismic profiles traversing the bright spots do not show the expected Class 3 offset responses. On these CMPs, significant decrease of far trace energy is observed. CMP data from other seismic profiles off‐structure do exhibit the Class 3 offset responses, implying that structural complications may be interfering with the offset response. A synthetic AVO gather was generated using well log data, which supports the off‐structure Class 3 responses, further reinforcing the concept of structurally‐biased AVO responses. Acoustic, pseudo‐spectral modeling of the structure substantiates the misleading AVO response. Pseudo‐spectral modeling results suggest that signal degradation observed on the far offsets is caused by wavefield refraction—a shadow zone, where the known hydrocarbon‐bearing sands are not completely illuminated. Such shadow zones obscure the correct AVO response, which may have bearing on exploration and development.

Incomplete AVO near Salt Structures and Impact for AVO Analysis

1992 ◽  
Vol 10 (4-5) ◽  
pp. 335-353
Author(s):  
C.P. Ross
Keyword(s):  
Well Log ◽  
Seismic Profiles ◽  
Signal Degradation ◽  
Amplitude Versus Offset ◽  
Bright Spots ◽  
Close Proximity ◽  
Pseudo Spectral ◽  
Amplitude Versus ◽  
Structure Class ◽  
Made In

Amplitude versus offset (AVO) measurements for deep hydrocarbon-bearing sands can be compromised when made in close proximity to a shallow salt piercement structure. Anomalous responses are observed, particularly on low acoustic impedance bright spots. Common-midpoint (CMP) data from key seismic profiles traversing the bright spots do not show the expected Class 3 offset responses as defined by Rutherford and Williams (1989). On these CMPs, significant decrease of far trace energy is observed. CMP data from other seismic profiles off-structure do exhibit the Class 3 offset responses, implying that structural complications may be interfering with the offset response. A synthetic AVO gather was generated using well log data, which supports the off-structure Class 3 responses, further reinforcing the concept of structurally-biased AVO responses. Acoustic, pseudo-spectral modelling of the structure substantiates the misleading AVO response. Pseudo-spectral modelling results suggest signal degradation observed on the far offsets is caused by wavefield refraction — a shadow zone, where the known hydrocarbon-bearing sands are not completely illuminated. Such shadow zones obscure the correct AVO response, which may have bearing on exploration and development.

Exploration application of seismic amplitude analysis in the Krishna-Godavari Basin, east coast of India

2014 ◽  
Vol 2 (4) ◽  
pp. SP5-SP20 ◽  
Author(s):  
Ram Janma Singh
Keyword(s):  
Amplitude Analysis ◽  
Seismic Amplitude ◽  
High Impedance ◽  
Data Phase ◽  
Amplitude Versus Offset ◽  
Bright Spots ◽  
Strong Amplitude ◽  
Very High ◽  
Amplitude Versus ◽  
Godavari Basin

Seismic amplitude anomalies are attractive exploration targets in the Krishna-Godavari Basin offshore India. These bright spots mostly have very high amplitudes, so confident interpretations have been possible. We distinguished between hydrocarbon-bearing sands, water-bearing sands, and high-impedance nonreservoir bodies. Also, we mapped channel architecture and accurately predicted reservoir thickness. Strong amplitude anomalies, prospective seismic character based on an understanding of data phase and polarity, flat spots, and amplitude versus offset have all provided valuable evidence.

scholarly journals A Series of Humanly-Fashioned Flints Found in the Cliffs and on the Shore at Mundesley, Norfolk

1920 ◽  
Vol 3 (2) ◽  
pp. 219-243
Author(s):  
J. Reid Moir
Keyword(s):  
Present Author ◽  
The South ◽  
North West ◽  
The North ◽  
Close Proximity ◽  
Made In

When visiting Mundesley, in Norfolk, in September, 1916, the present author found upon the shore, in close proximity to an exposure of clay which he now considers to be referable to the Cromer Forest Bed Series, a very finely-made and large flint flake, of human manufacture. This discovery induced him to again visit Mundesley, and during this year (1919) close upon three weeks have been spent in an examination of the stretch of cliffs and shore lying between Trimingham, to the north-west of Mundesley, and Bacton, which lies to the south-east.The author's researches have been greatly helped by the co-operation of three friends, Professor A. S. Barnes, Mr. Walter B. Nichols, and the Hon. Robert Gathorne-Hardy, who accompanied him to Mundesley, and to whom he offers his warmest thanks. He would, however, wish to make it clear that these gentlemen are in no way responsible for the statements made in this paper. For these the author is solely responsible.

The Ancient Cart-tracks of Malta

Antiquity ◽  
1954 ◽  
Vol 28 (110) ◽  
pp. 91-98 ◽  
Author(s):  
H. S. Gracie
Keyword(s):  
Agricultural Soil ◽  
Field Work ◽  
Present Writer ◽  
Small Scale ◽  
Far North ◽  
South Eastern ◽  
Close Proximity ◽  
Made In

The barren hill-tops of Malta are scored in many places by ancient ruts cut deeply into the rock. They can be seen also on the slopes and on the lower plains, but less frequently because these areas are normally under agricultural soil. They always occur in pairs from 52 to 58 inches apart and were quite clearly used by vehicles. They have been discussed in print for 300 years but no agreement has been reached on how, when or why they were made or what vehicles used them. In fact, there are as many theories as there are authors. Of these writers only Captain E. G. Fenton and Professor Sir T. Zammit appear to have done any serious field work, and none has published a map. The present writer, therefore, decided to attempt the laborious task of plotting them, making such other observations and measurements as he could. Zammit, in the paper cited, reproduced some excellent photographs from both the ground and the air, to which the reader is referred.Time did not permit an examination of the whole island and few observations were made in the low-lying south-eastern part. A fairly intensive survey was made of the high ground as far north as the Baida Ridge, which joins the northern shores of Ghain Tuffieha Bay and St. Paul’s Bay. Two portions of the map are reproduced here. Where there are a number of parallel tracks in close proximity they are shown on the map as one on account of the necessarily small scale used. The gaps in the routes are mainly due to cultivated patches, and no attempt has been made to bridge them by conjecture.

scholarly journals Crosswell Seismic Amplitude-Versus-Offset for Detailed Imaging of Facies and Fluid Distribution within Carbonate Oil Reservoirs

2008 ◽  
Author(s):  
Wayne Pennington ◽  
Mohamed Ibrahim ◽  
Roger Turpening ◽  
Sean Trisch ◽  
Josh Richardson ◽  
...  
Keyword(s):  
Oil Reservoirs ◽  
Fluid Distribution ◽  
Seismic Amplitude ◽  
Amplitude Versus Offset ◽  
Detailed Imaging ◽  
Amplitude Versus

scholarly journals QVOA Techniques for Estimation of Fracture Directions

2018 ◽  
Vol 2018 ◽  
pp. 1-11
Author(s):  
Vladimir Sabinin
Keyword(s):  
Quality Factor ◽  
Symmetry Axis ◽  
Factor Versus ◽  
Synthetic Data ◽  
Computational Techniques ◽  
High Quality ◽  
Amplitude Versus Offset ◽  
Target Layer ◽  
Analysis Quality ◽  
Amplitude Versus

Some new computational techniques are suggested for estimating symmetry axis azimuth of fractures in the viscoelastic anisotropic target layer in the framework of QVOA analysis (Quality factor Versus Offset and Azimuth). The different QVOA techniques are compared using synthetic viscoelastic surface reflected data with and without noise. I calculated errors for these techniques which depend on different sets of azimuths and intervals of offsets. Superiority of the high-order “enhanced general” and “cubic” techniques is shown. The high-quality QVOA techniques are compared with one of the high-quality AVOA techniques (Amplitude Versus Offset and Azimuth) in the synthetic data with noise and attenuation. Results are comparable.

High-resolution seismic velocity analysis by sign-based weighted semblance

Geophysics ◽  
2021 ◽  
pp. 1-35
Author(s):  
M. Javad Khoshnavaz
Keyword(s):  
Seismic Velocity ◽  
Resolution Enhancement ◽  
Synthetic Data ◽  
Correlation Coefficients ◽  
Velocity Model ◽  
Seismic Attenuation ◽  
Velocity Analysis ◽  
Velocity Models ◽  
Amplitude Versus Offset ◽  
Amplitude Versus

Building an accurate velocity model plays a vital role in routine seismic imaging workflows. Normal-moveout-based seismic velocity analysis is a popular method to make the velocity models. However, traditional velocity analysis methodologies are not generally capable of handling amplitude variations across moveout curves, specifically polarity reversals caused by amplitude-versus-offset anomalies. I present a normal-moveout-based velocity analysis approach that circumvents this shortcoming by modifying the conventional semblance function to include polarity and amplitude correction terms computed using correlation coefficients of seismic traces in the velocity analysis scanning window with a reference trace. Thus, the proposed workflow is suitable for any class of amplitude-versus-offset effects. The approach is demonstrated to four synthetic data examples of different conditions and a field data consisting a common-midpoint gather. Lateral resolution enhancement using the proposed workflow is evaluated by comparison between the results from the workflow and the results obtained by the application of conventional semblance and three semblance-based velocity analysis algorithms developed to circumvent the challenges associated with amplitude variations across moveout curves, caused by seismic attenuation and class II amplitude-versus-offset anomalies. According to the obtained results, the proposed workflow is superior to all the presented workflows in handling such anomalies.

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