COLOR SONAGRAMS: A NEW DIMENSION IN SEISMIC DATA INTERPRETATION

Geophysics ◽  
1971 ◽  
Vol 36 (6) ◽  
pp. 1074-1098 ◽  
Author(s):  
A. H. Balch
Keyword(s):  
Seismic Data ◽  
Computer Graphic ◽  
Data Interpretation ◽  
Seismic Events ◽  
Time Varying ◽  
Light Spectrum ◽  
Seismic Section ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
High Frequencies

We have developed a computer‐graphic‐photographic system which uses color mimicry to display the frequency spectra of seismic events simultaneously with their time‐varying waveforms. Mimicking the visible light spectrum, we have used red for the low frequencies and violet for the highs. The output of our system is a variable‐area‐wiggle‐trace seismic cross‐section. The waveforms are the same as those on a conventional section; however, the variable‐area part of the section appears in color. The color represents the frequency spectrum of the wavelets. Lateral changes in rock attenuation show up as color shifts on this type of display. Faults often stand out as interrupted color bands. Fault diffractions sometimes have a characteristic color signature. The cancellation of high frequencies due to misalignment of events on constant‐velocity stacks can show up in color. Loss of high frequencies due to slight lateral changes in moveout velocity, and consequent trace misalignment, is often indicated by a shift toward red on a color seismic section.

Ground-roll attenuation using curvelet downscaling

Geophysics ◽  
2018 ◽  
Vol 83 (3) ◽  
pp. V185-V195 ◽  
Author(s):  
Mostafa Naghizadeh ◽  
Mauricio Sacchi
Keyword(s):  
Seismic Data ◽  
Curvelet Transform ◽  
Low Frequencies ◽  
High Frequencies ◽  
Seismic Records ◽  
Mask Function ◽  
Ground Roll ◽  
Least Squares Optimization ◽  
Seismic Reflections ◽  
Content Information

We have developed a ground-roll attenuation strategy for seismic records that adopts the curvelet transform. The curvelet transform decomposes the seismic events based on their dip and frequency content information. The curvelet panels that contain only either reflection or ground-roll energy can be used to alter the curvelet panels with mixed reflection and ground-roll energies. We build a curvelet-domain mask function from the ground-roll-free curvelet coefficients (high frequencies) and downscale it to the ground-roll-contaminated curvelet coefficients (low frequencies). The mask function is used inside a least-squares optimization scheme to preserve the seismic reflections and attenuate the ground roll. Synthetic and real seismic data examples show the application of the proposed ground-roll attenuation method.

A fast and simple method of spectral enhancement

Geophysics ◽  
2014 ◽  
Vol 79 (3) ◽  
pp. V75-V80 ◽  
Author(s):  
Muhammad Sajid ◽  
Deva Ghosh
Keyword(s):  
Seismic Data ◽  
Real Data ◽  
Difference Operators ◽  
Frequency Noise ◽  
Simple Method ◽  
Low Frequencies ◽  
High Frequencies ◽  
Algorithm Comparison ◽  
Spectral Enhancement ◽  
Bed Thickness

The ability to resolve seismic thin beds is a function of the bed thickness and the frequency content of the seismic data. To achieve high resolution, the seismic data must have broad frequency bandwidth. We developed an algorithm that improved the bandwidth of the seismic data without greatly boosting high-frequency noise. The algorithm employed a set of three cascaded difference operators to boost high frequencies and combined with a simple smoothing operator to boost low frequencies. The output of these operators was balanced and added to the original signal to produce whitened data. The four convolutional operators were quite short, so the algorithm was highly efficient. Synthetic and real data examples demonstrated the effectiveness of this algorithm. Comparison with a conventional whitening algorithm showed the algorithm to be competitive.

6D phase-difference attributes for wide-azimuth seismic data interpretation

Geophysics ◽  
2020 ◽  
Vol 85 (6) ◽  
pp. IM37-IM49 ◽  
Author(s):  
Sanyi Yuan ◽  
Jinghan Wang ◽  
Tao Liu ◽  
Tao Xie ◽  
Shangxu Wang
Keyword(s):  
Phase Difference ◽  
Seismic Data ◽  
Seismic Anisotropy ◽  
Data Interpretation ◽  
Data Sets ◽  
Q Value ◽  
Frequency Spectra ◽  
Karst Caves ◽  
Common Depth Point ◽  
Value Decomposition

Phase information of seismic signals is sensitive to subsurface discontinuities. However, 1D phase attributes are not robust when dealing with noisy data. In addition, variations of seismic phase attributes with azimuth are seldom explored. To address these issues, we have developed 6D phase-difference attributes (PDAs) derived from azimuthal phase-frequency spectra. For the seismic volume of a certain azimuth and frequency, we first construct stacked phase traces at each common-depth point along a certain decomposed trending direction. Then, the 6D PDA is extracted by calculating the complex-valued covariance at a 6D phase space. The proposed method enables characterization of the subsurface discontinuities and indicates seismic anisotropy. Moreover, we provide one q-value attribute obtained by singular value decomposition to describe the variation intensity of PDA along different azimuths. Simulated and field wide-azimuth seismic data sets are used to illustrate the performance of the proposed 6D PDA and the derived q-value attribute. The results show that PDA at different frequencies can image various geologic features, including faults, fracture groups, and karst caves. Our field data example shows that PDA is able to discern the connectivity of karst caves using large-azimuth data. In addition, PDA along different azimuths and the q-value attribute provide a measurement of azimuthal variations, as well as the anisotropy. Our 6D PDA method can be used as a potential tool for wide-azimuth seismic data interpretation.

Pre-Stall Waves: Precursors to Stall Inception in a Contra-Rotating Axial Fan

2020 ◽  
Author(s):  
Manas Madasseri Payyappalli ◽  
A. M. Pradeep
Keyword(s):  
Low Frequency ◽  
Intermediate Frequency ◽  
Axial Fan ◽  
Frequency Spectra ◽  
Low Frequencies ◽  
Stall Inception ◽  
High Frequencies ◽  
Inflow Condition ◽  
Design Speed ◽  
High Frequency Waves

Abstract Stall in a compressor or a fan is often associated with pre-stall waves, that could act as precursors. The present study aims to understand in detail the pre-stall waves leading to instabilities in a low aspect ratio, low hub-tip ratio contra-rotating axial fan. Apart from a clean inflow condition, experiments on the contra-rotating fan are also carried out for two radial distortion conditions, namely, hub-radial and tip-radial distortions, and three circumferential distortion conditions, namely, simple-circumferential, hub-complex-circumferential and tip-complex-circumferential distortions. The results primarily concluded that operating rotor-2 at a speed higher than the design speed could possibly suppress the pre-stall disturbances. Towards the fully developed stall, the waves that are associated with low frequencies speed up and thus these waves become intermediate frequency waves. The fluid phenomena that trigger the stall are associated with high frequencies and these subsequently stretch to low frequencies at the onset of fully developed stall. The low-frequency waves and high frequency waves compromise to reach an intermediate frequency range during the fully developed stall. Further, it is observed that disturbances associated with low frequencies as well as high frequencies co-exist during the fully developed stall regime. There is also a region in the frequency spectra where no disturbances are excited and this region appears to be a “no excitation zone”. This paper thus concludes that there possibly exists a mechanism through which the energy is transferred between different frequencies during the pre-stall and fully developed stall regimes.

scholarly journals Virtual resolution enhancement: A new enhancement tool for seismic data

2020 ◽  
Vol 12 (1) ◽  
pp. 363-375
Author(s):  
Mohamed A. Rashed ◽  
Ali H. Atef
Keyword(s):  
Seismic Data ◽  
Resolution Enhancement ◽  
Computational Time ◽  
Seismic Events ◽  
Seismic Section ◽  
Mathematical Rule ◽  
Different Types ◽  
Seismic Sections ◽  
Data Acquisition And Processing ◽  
Near Future

AbstractVirtual resolution enhancement (VRE) is a new poststack cosmetic tool that can be applied to different types of seismic data. VRE emphasizes major reflections, enhances temporal resolution of seismic events, and suppresses reverberation noise, leading to better visualization of the entire seismic data. VRE is based on simple mathematical rule, and its parameters can be tweaked to suite the vast variety of seismic data available today. Although VRE does not reveal new or hidden features on seismic section, it significantly enhances the existing ones, which improves the interpretation and assists automatic horizon picking process. The only disadvantage of VRE is the long computational time. However, given the giant advances in the computational power and speed expected in the near future, this problem should be negligible. Tests conducted on seismic sections, collected from different regions in the world and went through different data acquisition and processing routines, prove the effectiveness of the VRE procedure.

A Novel Workflow to Invert Broadband Seismic Data: A Case Study from Onshore Fields in Abu Dhabi

2021 ◽  
Author(s):  
M. Afia ◽  
A. Mukherjee ◽  
A. Glushchenko ◽  
R. Elsayed ◽  
M. Paydayesh ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Seismic Data ◽  
Full Range ◽  
Low Frequency ◽  
Seismic Inversion ◽  
Well Log ◽  
Well Test ◽  
Low Frequencies ◽  
High Frequencies ◽  
Successful Recovery

Abstract Broadband seismic data has several benefits for quantitative seismic reservoir characterization. It is characterized by a significant increase of seismic frequency bandwidth on both the low and high sides of the frequency spectra. This work presents a novel seismic inversion approach to exploit the full value out of broadband seismic data. The average wavelet from broadband seismic data is limited in high and low frequencies due to the short duration of the well log and the misalignment of the seismic data with the well-log synthetic at high frequencies. Limitation of the extracted wavelet and optimization can generate band-limited inversion results that do not capture the full range of frequencies. An alternate approach of dividing the data into three frequency bands resulted in extracted wavelets that capture the spectrum of each band, and in turn produced a reliable broadband inversion result honoring the full range of frequencies present in the data. Inversion results gave a superior match of the estimated synthetic with the data spectra (Figure 1), and the reservoir was better calibrated at all the well locations. Successful recovery of the ultra-low frequencies enabled us to maximize the value of the broadband data. The workflow also pushed the frequency of the inverted properties to 80 Hz which helped in turn to characterize some of the relatively thinner layers, which were otherwise getting averaged out. Building a low frequency model for AVO seismic inversion using ultra-low frequency information leads to a significant improvement of predictability away from wells. As a prior model, a geologically constrained (4 Hz) low frequency filter was applied. Review of the broadband AVO seismic inversion results clearly indicate a better match between the inverted traces and well log properties at the studied wells. Also, the blind well test results at four wells indicate an excellent match to the blind well logs, which adds a high degree of confidence on the inverted elastic properties. Also, the synthetic spectra of the ultra-low and ultra-high frequencies is captured and maintained in the inverted broadband seismic data. The novelty of the new workflow is in the ability to effectively invert the broad frequency band of seismic data. Successful recovery of the ultra-low and ultra-high frequencies enabled us to maximize the value of the broadband data. Subsequently, the high frequency elastic properties helped in successful characterization of thinner reservoirs and will help in better optimization of the future field development initiatives.

Diabatically Induced Secondary Flows in Tropical Cyclones. Part II: Periodic Forcing

2009 ◽  
Vol 137 (3) ◽  
pp. 822-835 ◽  
Author(s):  
Hugh E. Willoughby
Keyword(s):  
Tropical Cyclones ◽  
Partial Derivative ◽  
Secondary Flows ◽  
Wave Radiation ◽  
Time Varying ◽  
Axially Symmetric ◽  
Periodic Forcing ◽  
Low Frequencies ◽  
High Frequencies ◽  
Steady Solutions

Abstract The linearized equation for the time-varying, axially symmetric circumferential component of the vorticity in a hurricane-like vortex closely resembles the classical Sawyer–Eliassen equation for the quasi-steady, diabatically induced secondary-flow streamfunction. The salient difference lies in the coefficients of the second partial derivatives with respect to radius and height. In the Sawyer–Eliassen equation, they are the squares of the buoyancy and isobaric local inertia frequencies; in the circumferential vorticity equation they are the differences between these quantities and the square of the frequency with which the imposed forcing varies. The coefficient of the mixed partial derivative with respect to radius and height is the same in both equations. Thus, for low frequencies the response to periodic forcing is a slowly varying analog to steady Sawyer–Eliassen solutions. For high frequencies, the solutions are radially propagating inertia-buoyancy waves. Since the local inertia frequency, which approximately defines the boundary between quasi-steady and propagating solutions, decreases with radius, quasi-steady solutions in the vortex core transform into radiating ones far from the center. Periodic forcing will always lead to some wave radiation to the storm environment unless the period of the forcing is longer than a half-pendulum day.

Effect of Blowing Agent on Cell Morphology and Acoustic Absorption of Natural Rubber Foam

2015 ◽  
Vol 804 ◽  
pp. 25-29 ◽  
Author(s):  
Wanlop Harnnarongchai ◽  
Kantima Chaochanchaikul
Keyword(s):  
Natural Rubber ◽  
Cell Size ◽  
Cell Morphology ◽  
Foam Cell ◽  
Adsorption Coefficient ◽  
Low Frequencies ◽  
Potassium Oleate ◽  
High Frequencies ◽  
Blowing Agent ◽  
Open Cell Foam

The sound absorbing efficiency of natural rubber (NR) foam is affected by the cell morphology of foam. Potassium oleate (K-oleate) and sodium bicarbonate (NaHCO3) were used as blowing agents to create open-cell foam. Amounts of the blowing agent were varied from 0.5 to 8.0 part per hundred of rubber (phr) to evaluate cell size and number of foam cell as well as sound adsorption coefficient of NR foam. The NR foam specimens were prepared using mould and air-circulating oven for vulcanizing and foaming processes. The results indicated that K-oleate at 2.0 phr and NaHCO3 at 0.5 phr led to form NR foam with the smallest cell size and the largest number of foam cell. At low frequencies, the optimum sound adsorption coefficient of NR foam was caused by filling K-oleate 2 phr. However, that of NR foam at high frequencies was provided by 0.5 phr-NaHCO3 addition.

Hearing loss in diabetics

1993 ◽  
Vol 107 (3) ◽  
pp. 179-182 ◽  
Author(s):  
J. R. Cullen ◽  
M. J. Cinnamond
Keyword(s):  
Hearing Loss ◽  
Sensorineural Deafness ◽  
Insulin Dosage ◽  
Speech Discrimination ◽  
Low Frequencies ◽  
High Frequencies ◽  
History Of ◽  
Insulin Dependent ◽  
Stapedial Reflex ◽  
The Relationship

The relationship between diabetes and senbsorineural hearing loss has been disputed. This study compares 44 insulin-dependent diabetics with 38 age and sex matched controls. All had pure tone and speech audiometry performed, with any diabetics showing sensorineural deafness undergoing stapedial reflecx decat tests. In 14 diabetics stapedial reflex tests showed no tone decay in any patient, but seven showed evidence of recruitment. Analysis of vaiance showed the diabetics to be significantly deafer than the control population.The hearing loss affected high frequencies in both sexes, but also low frequencies in the male. Speech discrimination scores showed no differences. Further analysis by sex showed the males to account for most of the differences. Analysys of the audiograms showered mostly a high tone loss. Finally duration of disbetes, insulin dosage and family history of diabtes were not found to have a significant effect on threshold.

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