• Title/Summary/Keyword: 진폭구배

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Amplitude Variation Analysis for Deep Sea Seismic Data in the Ulleung Basin, East Sea (동해 울릉분지 심해 탄성파 탐사자료 진폭변화분석)

  • Cheong, Snons;Kim, Youngjun;Kim, Byungyup;Koo, NamHyung;Lee, Ho-Young
    • Geophysics and Geophysical Exploration
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    • v.16 no.3
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    • pp.163-170
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    • 2013
  • The amplitude variation with offset of seismic data can detect fluids in the sediment and resolve the petrophysical properties of hydrocarbons in the subsurface. We analyzed and described the amplitude variation in deep sea seismic data obtained from the Ulleung Basin, East Sea. By inspecting seismic CDP-offset and CDP-angle gathers which show a bright reflection event, we decided a target zone for amplitude variation analysis. From the seismic angle gather at the middle of Ulleung Basin, we recognized amplitude increase or decrease versus offset on the intercept-gradient curve. Using the product attribute and Poisson's ratio change attribute computed in terms of intercept with gradient, the top and the base of gas saturated sediments were described. The area of amplitude variation suggestive of the presence of gas saturated sediments is shown at the depth of 3 s traveltime. Anomalous features of seismic amplitude in the Ulleung Basin were classified by the crossplot of intercept and gradient. The background trend of crossplot between intercept and gradient shows an inverse proportional relation that is common for wet sediments. Anomalous amplitudes of Class III fall into the first and the third quadrants on crossplots. We inferred regional gas/water saturated area with the horizontal dimension of 150 m in the Ulleung Basin by cross-section with respect to cross-plot anomaly.

Identification of high-dip faults utilizing the GRM technique of seismic refraction method(Ⅱ) -Application to real data- (굴절파 GRM 해석방법을 응용한 고경사 단층 인지 (Ⅱ) -실제 자료 적용-)

  • Kim, Gi Yeong;U, Nam Cheol
    • Journal of the Korean Geophysical Society
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    • v.2 no.1
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    • pp.65-74
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    • 1999
  • From refraction data along four seismic profiles near Eonyang which the Yangsan fault passes through, the Slope Variation Indicators (SVI) are computed and interpreted in terms of fault distribution. The average velocities of 2,250-2,870 m/s are estimated using velocity-analysis functions for the target boundary along those profiles. The average velocity for Line 1 is approximately 600 m/s lower than ones for the other lines. The SVI's with amplitude greater than or equal to 0.5 ms/m are turned out to be located near faults shown on the high-resolution reflection section, as closely as one station spacing (3 m). Large amplitude SVI's are densely distributed near National Road 35, and the fault having the largest vertical slip is indicated to be located approximately 930 m west of the inferred fault on the published geologic map.

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Aquifer Characterization Using Seismic Data on the Aquistore CCS Project, Canada (캐나다 아퀴스토어 탄성파자료를 통한 이산화탄소 지중저장 연구지역 대수층 특성화)

  • Cheong, Snons;Kim, Byoung-Yeop;Shinn, Young Jae;Lee, Ho-Yong;Park, Myung-Ho
    • Economic and Environmental Geology
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    • v.47 no.6
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    • pp.625-633
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    • 2014
  • The Aquistore project is the world's first commercial capture, transportation, utilization and storage project of post-combustion $CO_2$ from a coal-fired thermo electric power plant, and the proposed storage is a saline aquifer at a depth of about 3,500 m. Deep saline aquifer, compared to hydrocarbon reservoir, provides the great volumetric potential for storage of $CO_2$ anywhere in the world, therefore the research results from the project may be exported globally to other sites. Geological $CO_2$ storage characterization for saline aquifer instead of hydrocarbon reservoir needs to estimate the geophysical properties of subsurface geology. This study calculated the geophysical property of water-saturated formation by applying amplitude variation analysis developed from oil and gas exploration. We correlated horizon tops at the well logs to seismic traveltime of 1,815 and 1,857 ms as Winnipeg and Deadwood formations. Gradient analysis from seismic traces showed correlation coefficient of 45 - 81 % on amplitude variation with respect to incident angle. Crossplot of intercept and gradient shows the inverse proportional trend which represents typical water saturated sediments. Product attribute of intercept and gradient described the base of wet sediment. Poisson's ratio change attribute increased at the top of target area satisfying with wet sediment and decreased at the top of basement in a dry rock bed.

Influence of Wall Motion and Impedance Phase Angle on the Wall Shear Stress in an Elastic Blood Vessel Under Oscillatory Flow Conditions (맥동유동하에 있는 탄성혈관에서 벽면운동과 임피던스 페이즈앵글이 벽면전단응력에 미치는 영향)

  • 최주환;이종선;김찬중
    • Journal of Biomedical Engineering Research
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    • v.21 no.4
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    • pp.363-372
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    • 2000
  • The present study investigated flow dynamics of a straight elastic blood vessel under sinusoidal flow conditions in order to understand influence of wall motion and impedance phase angle(time delay between pressure and flow waveforms) on wall shear stress distribution using computational fluid dynamics. For the straight elastic tube model considered in the our method of computation. The results showed that wall motion induced additional terms in the axial velocity profile and the pressure gradient. These additional terms due to wall motion reduced the amplitude of wall shear stress and also changed the mean wall shear stress. Te trend of the changes was very different depending on the impedance phase angle. As the wall shear stress increased. As the phase angle was reduced from 0$^{\circ}$to -90$^{\circ}$for ${\pm}$4% wall motion case, the mean wall shear stress decreased by 10.5% and the amplitude of wasll shear stress increased by 17.5%. Therefore, for hypertensive patients vulnerable state to atherosclerosis according to low and oscillatory shear stress theory.

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Identification of high-dip faults utilizing the GRM technique of seismic refraction method(Ⅰ) - Computer modeling - (굴절파 GRM 해석방법을 응용한 고경사 단층 인지(Ⅰ) - 컴퓨터 모델링 연구 -)

  • Kim, Gi Yeong
    • Journal of the Korean Geophysical Society
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    • v.2 no.1
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    • pp.57-64
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    • 1999
  • To effectively identify near-surface faults with vertical slips from seismic refraction data, the GRM interpretation technique is tested and investigated in terms of various parameters through computer modeling. A characteristic change in shape of the velocity-analysis function near faults is noticed, and a new strategy of `Slope Variation Indicator (SVI)' is developed and tested in this study. The SVI is defined as a first horizontal derivative of the difference of velocity analysis functions for a large XY value and a small one, respectively. As the dip of refractor decreases and as the difference in XY value increases, the peak value of SVI increases and its duration decreases. Consequently, the SVI indicates accurately the location of buried fault in the test models. The SVI is believed to be an efficient tool in seismic refraction method to investigate location and distribution of shallowly buried faults.

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Response of Ultrafiltration Flux to Periodic Oscillations in Transmembrane Pressure Gradient (압력구배의 주기적 변화에 따른 한외여과 Flux의 변화)

  • 서창우;이은규
    • KSBB Journal
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    • v.14 no.2
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    • pp.230-234
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    • 1999
  • To improve the crossflow untrafiltration flux, we applied periodic oscillations in transmembrane pressure gradient in order to promote fluid turbulence by inducing repeated compression and relaxation of the cake/gel layer. The oscillatory forms used were square-, sine-, triangle-wave, and pumping interruption. The permeate flux profiles were mathematically simulated and compared with the experimental data. The result showed the periodic pumping interruption most effectively improved the overall flux by up to about 32%. Enough pumping off-time, at least on the order of tens of seconds, was needed to allow the solutes in the layer to diffuse back to the bulk phase. It was better to start the oscillations earlier before the layer was fully established. The square-wave oscillation yielded about 11% increase, which was particularly pronounced in the later part of the filtration. Either the amplitude or the period of the oscillations resulted little influence on flux.actate ester, and lactate ester produced in esterification reaction was distilled simultaneously with hydrolysis reaction into lactic acid. When the yields of lactic acid recovered by batch reactive distillations with various alcohols were compared, the yield of lactic acid was increased as the volatility of lactate ester was increased. In this batch reactive distillation, because the mixtures condensed in partial condensor were flown to reboiler through distillation column, the recovery yield of lactic acid was affected by operation temperature of partial condensor. Hydrolysis reaction into lactic acid in distillation column rarelyoccurred because of short retention time of lactate ester and water. Lactate ester was reacted into lactic acid in reboiler.

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Physical Environment Changes in the Keum River Estuary by the Dyke Gate Operation: I. Mean Sea Level and Tide (하구언 수문작동으로 인한 금강 하구역의 물리적 환경변화: I. 평균해수면과 조석)

  • Kwon, Hyo-Keun;Lee, Sang-Ho
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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    • v.4 no.2
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    • pp.93-100
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    • 1999
  • Analyzing the tide data taken at Kunsan inner and Outer ports, non-tidal and mean sea level and harmonic constants of major constituents are investigated to examine the effects of the dyke gate operation on the sea level change in Keum River estuary. Non-tidal and annual mean sea levels decrease at Kunsan Inner and Outer ports after the dyke gate operation, especially showing an abrupt drop of non-tidal sea level at Kunsan Inner port. This non-tidal sea level drop results in the mean sea level gradient change between the inner and outer port, which can be mainly explained in terms of the decrease of river discharge from the dyke. Amplitudes of the $M_2$ and $S_2$ tides at the Inner port increase after the dyke gate operation, showing an abrupt jump, and phases of both tides slightly decrease. Amplitude and phase of the $K_1$ and $O_1$ tides show slight changes after the dyke gate operation. This significant change of semi diurnal tide amplitude is believed as a result of superposition of incident tidal wave and reflected tidal wave from the dyke.

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Characteristics of Heat Flux in Intake and Exhaust Valve of Methanol Fueled Engine (메탄올기관과 흡.배기 밸브에서의 열유속 특성)

  • 김문헌;임연기;이종태
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.1
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    • pp.208-217
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    • 1996
  • Instantaneous surface temperature and unsteady heat flux of intake and exhaust valve in methanol fueled engine were investigate as a function of compression ratio and engine speed. To accomplish this purpose, the instantaneous temperature sensor was designed and it was installed into three point of intake and exhaust valve head to measure unsteady temperature. The unsteady heat flux at valves was evaluated using one dimensional heat conduction equation with the valve head temperature and temperature gradient. And also mean heat flux of intake and exhaust valve for each stroke were evaluated as a function of engine speed.

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Maximising the lateral resolution of near-surface seismic refraction methods (천부 탄성파 굴절법 자료의 수평 분해능 최대화 연구)

  • Palmer, Derecke
    • Geophysics and Geophysical Exploration
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    • v.12 no.1
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    • pp.85-98
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    • 2009
  • The tau-p inversion algorithm is widely employed to generate starting models with most computer programs, which implement refraction tomography. This algorithm emphasises the vertical resolution of many layers, and as a result, it frequently fails to detect even large lateral variations in seismic velocities, such as the decreases which are indicative of shear zones. This study demonstrates the failure of the tau-p inversion algorithm to detect or define a major shear zone which is 50m or 10 stations wide. Furthermore, the majority of refraction tomography programs parameterise the seismic velocities within each layer with vertical velocity gradients. By contrast, the Generalized Reciprocal Method (GRM) inversion algorithms emphasise the lateral resolution of individual layers. This study demonstrates the successful detection and definition of the 50m wide shear zone with the GRM inversion algorithms. The existence of the shear zone is confirmed by a 2D analysis of the head wave amplitudes and by numerous closely spaced orthogonal seismic profiles carried out as part of a later 3D refraction investigation. Furthermore, an analysis of the shot record amplitudes indicates that a reversal in the seismic velocities, rather than vertical velocity gradients, occurs in the weathered layers. The major conclusion reached in this study is that while all seismic refraction operations should aim to provide as accurate depth estimates as is practical, those which emphasise the lateral resolution of individual layers generate more useful results for geotechnical and environmental applications. The advantages of the improved lateral resolution are obtained with 2D traverses in which the structural features can be recognised from the magnitudes of the variations in the seismic velocities. Furthermore, the spatial patterns obtained with 3D investigations facilitate the recognition of structural features such as faults which do not display any intrinsic variation or 'signature' in seismic velocities.

A Modeling Study on the AVO and Complex Trace Analyses of the Fracture Bone Reflection (파쇄대 반사에너지의 AVO 및 복소트레이스 분석에 관한 모형연구)

  • Han Soo-Hyung;Kim Ji-Soo;Ha Hee-Sang;Min Dong-Joo
    • Geophysics and Geophysical Exploration
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    • v.2 no.1
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    • pp.33-42
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    • 1999
  • AVO and complex trace analyses mainly used to characterize natural gas reservoir were tested in this paper for a possible application to detection of major geological discontinuities such as fracture zones. The test data used in this study were calculated by utilizing a viscoelastic numerical program which was based on the generalized Maxwell body for a horizontal fracture model. In AVO analysis of a horizontal fracture zone, p-wave reflection appears to be variant depending upon the acoustic-impedence contrast and the offset distance. The fracture zone is also effectively clarified both in gradient stack and range-limited stack in which fracture zone reflection is attenuated with the increasing offset distance. In complex attribute plots (instantaneous amplitude, frequency, and phase), the top and bottom of the fracture Tone are characterized by a zone of strong amplitudes and an event of the same phase. Low frequency characteristics appear at the fracture zone and the underneath. Amplitude attenuation and waveform dispersion are dependent on Q-contrast between the fracture zone and the surrounding media. They were properly compensated by optimum inverse Q-filtering.

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