scholarly journals Analysis of Water Features in Gas Leakage Area

2011 ◽  
Vol 2011 ◽  
pp. 1-10
Author(s):  
Liu Huaishan ◽  
Wang Fengfan ◽  
Tong Siyou ◽  
Li Gaolin ◽  
Zhang Haiyan
Keyword(s):  
Resonance Frequency ◽  
Sound Wave ◽  
Seismic Data ◽  
Gas Content ◽  
Practical Application ◽  
Gas Leakage ◽  
Wave Characteristics ◽  
Leakage Area ◽  
Different Depths ◽  
Sound Features

In a certain frequency range, gas is an effective absorber and scatterer of sound, which changes the compressibility of water, and then changes the speed and frequency of sound. Gas continues rising, deforming, and dissolving. The same bubble of natural gas has different radii at different depths. By analyzing these changes, the resonance frequency of gas bubble, and its impacts on sound wave, characteristics of the influences of gas at different depths on the incident sound wave can be obtained. The main sound features of gas are relevant to the gas size, gas content, velocity, attenuation, resonance frequency, the scattering cross-section, and so forth. Sound models with hydrate and free gas in the water and sediment are established. Through the practical application to actual data, the sound characteristics yielded when the gas (or gas hydrate dissociation) escaped the water of seismic data are very clear.

Wave-equation angle-domain common-image gathers for converted waves

Geophysics ◽  
2008 ◽  
Vol 73 (1) ◽  
pp. S17-S26 ◽  
Author(s):  
Daniel A. Rosales ◽  
Sergey Fomel ◽  
Biondo L. Biondi ◽  
Paul C. Sava
Keyword(s):  
Seismic Data ◽  
Incidence Angle ◽  
Velocity Ratio ◽  
Real Data ◽  
Single Mode ◽  
Practical Application ◽  
Converted Wave ◽  
Reflection Angle ◽  
Wavefield Extrapolation ◽  
Local Image

Wavefield-extrapolation methods can produce angle-domain common-image gathers (ADCIGs). To obtain ADCIGs for converted-wave seismic data, information about the image dip and the P-to-S velocity ratio must be included in the computation of angle gathers. These ADCIGs are a function of the half-aperture angle, i.e., the average between the incidence angle and the reflection angle. We have developed a method that exploits the robustness of computing 2D isotropic single-mode ADCIGs and incorporates both the converted-wave velocity ratio [Formula: see text] and the local image dip field. It also maps the final converted-wave ADCIGs into two ADCIGs, one a function of the P-incidence angle and the other a function of the S-reflection angle. Results with both synthetic and real data show the practical application for converted-wave ADCIGs. The proposed approach is valid in any situation as long as the migration algorithm is based on wavefield downward continuation and the final prestack image is a function of the horizontal subsurface offset.

Case study: The importance of gas leakage in interpreting amplitude‐versus‐offset (AVO) analysis

Geophysics ◽  
1991 ◽  
Vol 56 (11) ◽  
pp. 1886-1895 ◽  
Author(s):  
M. K. Sengupta ◽  
C. A. Rendleman
Keyword(s):  
Seismic Energy ◽  
Gas Content ◽  
Bright Spot ◽  
Seismic Section ◽  
Gas Leakage ◽  
Hydrocarbon Reservoir ◽  
Reflection Amplitude ◽  
Amplitude Versus Offset ◽  
Amplitude Anomaly ◽  
Amplitude Versus

The amplitude‐versus‐offset (AVO) method has been shown to indicate the presence of gas sands if the reflection amplitude from the seal/reservoir‐sand interface, measured in a common midpoint (CMP) gather, increases rapidly with increasing shot‐to‐geophone distance (or offset). However, in a few instances, it has been observed that the seismic reflection amplitude does not increase with offset and may even decrease if there is widespread gas leakage above the hydrocarbon reservoir causing partial gas saturation in the overburden sediments. Gas‐charged sediments are known to attenuate seismic energy. Depending on the size and shape of this gas leakage zone, there may be higher attenuation of seismic amplitudes with increasing offset. We present one such case that involves a prominent “bright‐spot” amplitude anomaly corresponding to a 56‐ft‐thick (17 m‐thick) gas sand in the Gulf of Mexico slope. The reflection amplitude for the sand top was found to decrease with increasing offset. There is also evidence of gas leakage into the sediments above the reservoir. Color amplitude displays of the seismic section show a low‐amplitude diffused zone above the bright‐spot amplitude anomaly, which suggests gas leakage. Further evidence of gas leakage can be inferred from the significant gas content (including heavier hydrocarbons) observed in the mud log. Gas leakage is also confirmed by gather modeling in which the effects of leakage‐caused attenuation are accounted for in matching the variation of seismic amplitude with offset.

scholarly journals A calculation method of gas emission zone in a coal mine considering main controlling factors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yong Chen ◽  
Ronghua Liu ◽  
Pushi Xuan
Keyword(s):  
Numerical Simulation ◽  
Permeability Coefficient ◽  
Field Experiments ◽  
Logistic Function ◽  
Measured Data ◽  
Gas Content ◽  
Coal Seam Gas ◽  
Gas Emission ◽  
Drainage Design ◽  
Different Depths

AbstractThe gas emission zone is an important parameter for the space–time effect of coal excavation and gas emission. In this paper, according to the effect of roadway excavation, a numerical model of gas emission zone based on the evolution of stress and permeability was established to obtain the width of gas emission zone with different pressure and permeability coefficient. Then the numerical simulation results were verified by measuring the gas content at different depths. Through numerical simulation and field measured data, the theoretical calculation formula is established on the basis of comprehensive consideration of the influencing factors of gas emission zone. The results showed that the gas emission zone increases with the increase of coal seam gas pressure and permeability coefficient when the roadway section and exposure time are the same. The measured gas emission zone, when taking gas content as the index with the same logistic function growth curve, matches the measured results with a relative error of 1.3 to 6%. The validity of the model is also verified by field experiments. The results can provide guidance for mine gas emission and gas drainage design.

Acoustic Properties of the Cod Swimbladder

1973 ◽  
Vol 58 (3) ◽  
pp. 797-820 ◽  
Author(s):  
OLAV SAND ◽  
A. D. HAWKINS
Keyword(s):  
Resonance Frequency ◽  
Relative Sensitivity ◽  
Acoustic Properties ◽  
Gas Bubble ◽  
A Value ◽  
Hearing Organ ◽  
Different Depths ◽  
Hearing Range ◽  
The Difference ◽  
Pressure Changes

1. The resonance frequency and damping of the swimbladder were measured for intact living cod at different depths. 2. At adaptation depth, the resonance frequency (fχ) of the organ was much higher than that predicted for an unrestrained gas bubble of similar volume. However, at much greater depths (where the hydrostatic pressure was 2 or more times greater than the adaptation pressure) fχ was only higher than expected by a factor of 1·25, and changed with depth in the manner of a free gas bubble. 3. The elevated values at greater depths can be explained in terms of the difference in shape between the swimbladder and an ideal spherical bubble, together with a clight effect from the surrounding tissues. We have calculated that the shear modulus of these tissues (µ1) has a value of approximately 1·7 x 106 dyne/cm2. However, we have suggested that the much higher elevation of fχ found at the adaptation depth results from a large increase in µ1 (by a factor of between 6 and 120). This increase may be the result of a maintained muscle tonus. 4. There is an immediate drop in fχ as a fish is moved to a new depth, but the elevated values are rapidly restored with time. This process of adjustment is too rapid to be accounted for by the restoration of the swimbladder to its former volume by the secretion or absorption of gas. It is possible that it is achieved by a muscular mechanism which restores µ1 to the former high value. 5. Though the maintenance of fχ at a high value may reflect mechanical processes concerned with the hydrostatic function of the swimbladder, or with the detection of static pressure changes, we suggest that it may also be of some value if the swimbladder is used as an accessory hearing organ. The maintenance of an fχ well above the hearing range of the fish ensures that the relative sensitivity of the animal to different frequencies does not alter with changes in depth.

Influence of sound wave characteristics on fluidization behaviors of ultrafine particles

2006 ◽  
Vol 119 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Qingjie Guo ◽  
Huie Liu ◽  
Wenzhong Shen ◽  
Xianghong Yan ◽  
Rugao Jia
Keyword(s):  
Sound Wave ◽  
Ultrafine Particles ◽  
Wave Characteristics

Analysis of Water Features in Gas Leakage Area

2013 ◽  
pp. 39-64
Author(s):  
Liu Huaishan ◽  
Wang Fengfan ◽  
Tong Siyou ◽  
Li Gaolin ◽  
Zhang Haiyan
Keyword(s):  
Gas Leakage ◽  
Leakage Area

scholarly journals Prediction of sweet spots in shale reservoir based on geophysical well logging and 3D seismic data: A case study of Lower Silurian Longmaxi Formation in W4 block, Sichuan Basin, China

2016 ◽  
Vol 35 (2) ◽  
pp. 147-171 ◽  
Author(s):  
Sheng Chen ◽  
Wenzhi Zhao ◽  
Yonglin Ouyang ◽  
Qingcai Zeng ◽  
Qing Yang ◽  
...  
Keyword(s):  
Seismic Data ◽  
Rock Physics ◽  
Gas Content ◽  
3D Seismic ◽  
Elastic Parameters ◽  
Longmaxi Formation ◽  
Shale Reservoir ◽  
3D Seismic Data ◽  
Evaluation Parameters ◽  
Sweet Spots

W4 block of Sichuan Basin is a pioneer in shale gas exploration and development in China. But geophysical prospecting is just at its beginning and thus has not provided enough information about how sweet spots distribute for the deployment of horizontal well. This paper predicted sweet spots based on logging and 3D seismic data. Well logging interpretation method was used to get the key evaluation parameters of shale reservoir and determine the distribution of sweet spots in vertical direction. Rock physics analysis technology was used to define the elastic parameters that were sensitive to the key evaluation parameters, such as TOC and gas content of shale gas reservoir. At the same time the quantitative relationships between them were established. Based on the result of seismic rock physics analysis, prestack inversion was carried out to predict the transverse plane distribution of the key evaluation parameters of shale reservoir. These research results are integrated to determine the distribution of sweet spots. The results show that sweet spots in this area were characterized by high TOC content, high gas content, high GR, high Young’s modulus, low Poisson’s ratio, low density, and low P-wave velocity. Density was the most sensitive elastic parameters to TOC of the reservoir. The optimal combination for predicting the gas content is composed of six parameters include density, Poisson’s ratio, and so on. Sweet spots in this block vertically concentrate within 30 m above the bottom of Longmaxi Formation. Two classes of sweet spots have been predicted in this area, class I sweet spots are recommended to be prioritized for development. This study effectively predicted the spatial distribution of sweet spots, which provide important guidance for the development of the area.

Source deghosting by depth apparition

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. P89-P107 ◽  
Author(s):  
Johan O. A. Robertsson ◽  
Dirk-Jan van Manen ◽  
Fredrik Andersson ◽  
Lasse Amundsen ◽  
Kurt Eggenberger
Keyword(s):  
Seismic Data ◽  
Sea Surface ◽  
New Method ◽  
Original Signal ◽  
Receiver Side ◽  
Simple Method ◽  
Different Depths ◽  
Marine Seismic ◽  
3D Applications ◽  
Spatial Source

Marine seismic data are distorted by ghosts as waves propagating upward reflect downward from the sea surface. Ghosts appear on the source side and the receiver side. However, whereas the receiver-side ghost problem has been studied in detail, and many different solutions have been proposed and implemented commercially, the source-side ghost problem has remained largely unsolved with few satisfactory solutions available. We have developed a new and simple method to remove sea-surface ghosts that is related to the recently introduced concept of signal apparition. As opposed to the temporal/spatial source signature modulation functions used in the original signal apparition theory, our source deghosting method relies on using sources at different depths but not at the same lateral positions. The new method promises to be particularly suitable for 3D applications on sparse or incomplete acquisition geometries.

Structural Features Controls of Coalbed Methane (CBM) Accumulation in the Weibei CBM Field, Southeastern Ordos Basin

2014 ◽  
Vol 962-965 ◽  
pp. 79-82 ◽  
Author(s):  
Ya Dong Bai ◽  
Tao Tao Yan ◽  
Jian Guo Wu ◽  
Yong Luo
Keyword(s):  
Theoretical Analysis ◽  
Seismic Data ◽  
Coalbed Methane ◽  
Ordos Basin ◽  
Structural Features ◽  
Gas Content ◽  
Normal Faults ◽  
Distribution Characteristics ◽  
Structural Interpretation ◽  
High Consistency

Based on the structural interpretation of seismic data, we analyzed the gas controlling effects of folds and faults on CBM accumulation qualitatively. Meanwhile, we discussed the lateral sealing ability of the major overthrust faults quantificationally by bringing in “Shale Gouge Ratio (SGR)”, which is proved to be applicable in analyzing the gas controlling effects of faults. The results of the theoretical analysis show that overthrust faults have better sealing effects than normal faults, and synclines are more conducive to CBM accumulation than anticlines. The SGR computed results show a high consistency with the distribution characteristics of the CBM gas content. In all, the folds have little controlling on CBM accumulation, and the faults play a major role in the gas controlling on CBM accumulation in the Weibei CBM field.

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