Pub Date : 2017-03-10DOI: 10.3997/2352-8265.20140217
Tomoaki Tanaka, H. Mikada, J. Takekawa
For exploring subsurface resources such as oil or natural gas reservoirs, seismic reflection survey has been widely iplementd in order to image subsurface structures. In recent years, utilization of S-wave or converted wave is required for estimating lithology or petrophysical properties of reservoir rock. However, such an analysis of S-wave seismograms had been relatively difficult. On the other hand, equivalent offset migration (EOM) is one of the prestack time migrations and has been found to be effective method for imaging S-wave information on the common scatter point (CSP) gather with recorded horizontal component in our previous study. Furthermore, S-wave AVO effect has also been confirmed by the amplitude reversal of S-wave event on the CSP gathers. Therefore, we propose the procedure of accurate estimation of densities and shear modulus with S-wave source. First, we conduct numerical experiment with a 2D layer model using horizontal point force to obtain horizontal component seismic data, in which we can get higher S/N data about S-wave. Second, we implement EOM with those data to get CSP gather, and calculate each cross-correlated value versus incident angle as observed waveform information. Third, in contrast, we generate calculated waveform information as a function of incident angle and physical properties with geometrical spreading, radiation pattern and S-wave reflection coefficient. Finally, we can estimate the optimal solutions by minimizing the misfit from the both information.
{"title":"AVO analysis using horizontal component of seismic data in equivalent offset migration method","authors":"Tomoaki Tanaka, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140217","DOIUrl":"https://doi.org/10.3997/2352-8265.20140217","url":null,"abstract":"For exploring subsurface resources such as oil or natural gas reservoirs, seismic reflection survey has been widely iplementd in order to image subsurface structures. In recent years, utilization of S-wave or converted wave is required for estimating lithology or petrophysical properties of reservoir rock. However, such an analysis of S-wave seismograms had been relatively difficult. On the other hand, equivalent offset migration (EOM) is one of the prestack time migrations and has been found to be effective method for imaging S-wave information on the common scatter point (CSP) gather with recorded horizontal component in our previous study. Furthermore, S-wave AVO effect has also been confirmed by the amplitude reversal of S-wave event on the CSP gathers. Therefore, we propose the procedure of accurate estimation of densities and shear modulus with S-wave source. First, we conduct numerical experiment with a 2D layer model using horizontal point force to obtain horizontal component seismic data, in which we can get higher S/N data about S-wave. Second, we implement EOM with those data to get CSP gather, and calculate each cross-correlated value versus incident angle as observed waveform information. Third, in contrast, we generate calculated waveform information as a function of incident angle and physical properties with geometrical spreading, radiation pattern and S-wave reflection coefficient. Finally, we can estimate the optimal solutions by minimizing the misfit from the both information.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75402149","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Fukuda, H. Takiguchi, T. Kazama, J. Nishijima, S. Gulyaev, T. Natusch, M. Amos, V. Stagpoole, C. Pearson
{"title":"New Absolute Gravity Measurements in New Zealand","authors":"Y. Fukuda, H. Takiguchi, T. Kazama, J. Nishijima, S. Gulyaev, T. Natusch, M. Amos, V. Stagpoole, C. Pearson","doi":"10.1007/1345_2017_18","DOIUrl":"https://doi.org/10.1007/1345_2017_18","url":null,"abstract":"","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"74 1","pages":"95-101"},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75071547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140200
S. Amani, A. Gholami, H. Kouhi
All of the seismic data include different amounts of seismic random noises, even after doing a comprehensive seismic data processing. This results in lower signal to noise ratio (SNR) or in other word, lower quality of seismic data. Because of the time-consuming processes of methods for doing seismic random noise attenuation, data processing companies don’t perform additional processing for attenuating of random noises after doing conventional methods like stacking and applying some filters. BUT, what about a very fast method which increases SNR both in pre-stacked and post-stacked data, significantly? Here, in this study we introduce an algorithm which is called ‘Fast 3D Block Matching (F3DBM)’ which combines the advantages of non-local and transform-domain denoising methods. This method has superior capability for preserving discontinuities presented in seismic data both qualitatively and quantitatively. We compare the ability of F3DBM with that of the state-of-the-art fast curvelet-based seismic denoising method for random noise attenuation both in pre-stacked and post-stacked data.
{"title":"A fast non-local transform-domain method for seismic random noise attenuation","authors":"S. Amani, A. Gholami, H. Kouhi","doi":"10.3997/2352-8265.20140200","DOIUrl":"https://doi.org/10.3997/2352-8265.20140200","url":null,"abstract":"All of the seismic data include different amounts of seismic random noises, even after doing a comprehensive seismic data processing. This results in lower signal to noise ratio (SNR) or in other word, lower quality of seismic data. Because of the time-consuming processes of methods for doing seismic random noise attenuation, data processing companies don’t perform additional processing for attenuating of random noises after doing conventional methods like stacking and applying some filters. BUT, what about a very fast method which increases SNR both in pre-stacked and post-stacked data, significantly? Here, in this study we introduce an algorithm which is called ‘Fast 3D Block Matching (F3DBM)’ which combines the advantages of non-local and transform-domain denoising methods. This method has superior capability for preserving discontinuities presented in seismic data both qualitatively and quantitatively. We compare the ability of F3DBM with that of the state-of-the-art fast curvelet-based seismic denoising method for random noise attenuation both in pre-stacked and post-stacked data.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"3 1","pages":"1-5"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74004075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140212
T. Kimura, H. Mikada, E. Araki, Y. Machida
Subduction zones where a tectonic plate subducting beneath the other plate, megathrust or interplate earthquakes could be generated repeatedly. Because of the nature of interplate earthquakes, the process of plate subduction governs the distribution, mechanics, and style of slip along the interplate fault. At the Nankai Trough subduction zone, located beneath the Pacific Ocean off the southeast coast of Japan, we have installed a seismic observation system, named DONET (Dense Oceanfloor Network system for Earthquake and Tsunamis), which is composed of twenty seafloor broadband seismometers and a borehole vertical seismic array to monitor the seismic activity and the process of earthquake generation including the stress accumulation. To elucidate earthquake generation and preparation process, it is necessary to investigate how the stress could be accumulated not only in deeper part but also in the shallow sediments, what the role of interstitial fluid could be in the stress accumulation processes, etc. There are some conventional methods to measure these physical properties, such as borehole strainmeter, borehole breakouts or borehole dynamic tests. However, these methods have some difficulties from the viewpoints of technical and/or cost. For example, borehole breakouts and dynamic tests can be conducted only while drilling and/or immediately after that. Therefore we need to have some other methods to see the state and variation of the stress in the subseafloor. In this study, we applied seismic interferometry technique to ambient noise records observed by horizontal components of DONET KMD13 seafloor seismometer to obtain time dependent S-wave velocity and its anisotropy as a proxy of stress state below the DONET observatory. We first calculated cross-diploe 4-C pseudo shot records from every 1 hour ambient noise records observed by horizontal components of the DONET seismometer for three years. In obtained 4-C shot records, clear phases, which should be caused by S-wave anisotropy, are visible. Alford rotation method was then applied to the 4-C shot records to obtain S-wave anisotropy parameters, directions of fast S-wave and time lag between fast and slow S-wave velocities below the DONET observatory. We expected that our method could be a simple tool to monitor stress state in the Nankai Trough seismogenic zone.
一个构造板块俯冲到另一个板块之下的俯冲带，大型逆冲断层或板块间地震可以反复发生。由于板块间地震的性质，板块俯冲过程决定了板块间断层的滑动分布、力学和样式。在日本东南沿海太平洋下的南开海槽俯冲带，我们安装了一个由20个海底宽带地震仪和一个井内垂直地震阵列组成的地震观测系统DONET (Dense Oceanfloor Network system for Earthquake and tsunami)，用于监测地震活动和包括应力积累在内的地震发生过程。为了阐明地震的发生和准备过程，有必要研究深部和浅部沉积物的应力如何积聚，间隙流体在应力积聚过程中可能发挥的作用等。有一些常规的方法来测量这些物理性质，如钻孔应变仪、钻孔突破或钻孔动态试验。然而，从技术和成本的角度来看，这些方法存在一些困难。例如，钻孔突破和动态测试只能在钻井时和/或钻井后立即进行。因此，我们需要一些其他的方法来观察海底应力的状态和变化。本研究采用地震干涉测量技术，对DONET KMD13海底地震仪水平分量观测到的环境噪声记录进行分析，获得了随时间变化的横波速度及其各向异性，作为DONET观测台下应力状态的代表。我们首先从DONET地震仪水平分量观测到的每1小时的环境噪声记录中计算了3年的交叉偶极4-C伪射击记录。在得到的4-C射击记录中，可以看到明显的相位，这应该是由s波各向异性引起的。然后将Alford旋转方法应用于4-C射孔记录，得到DONET观测台下方的s波各向异性参数、快s波方向和快、慢s波速度的时间差。本方法有望成为监测南开海槽发震带应力状态的简便工具。
{"title":"Seismic Velocity Monitoring Using Ambient Noise Observed by DONET Seismometers in the Nankai Trough, Japan","authors":"T. Kimura, H. Mikada, E. Araki, Y. Machida","doi":"10.3997/2352-8265.20140212","DOIUrl":"https://doi.org/10.3997/2352-8265.20140212","url":null,"abstract":"Subduction zones where a tectonic plate subducting beneath the other plate, megathrust or interplate earthquakes could be generated repeatedly. Because of the nature of interplate earthquakes, the process of plate subduction governs the distribution, mechanics, and style of slip along the interplate fault. At the Nankai Trough subduction zone, located beneath the Pacific Ocean off the southeast coast of Japan, we have installed a seismic observation system, named DONET (Dense Oceanfloor Network system for Earthquake and Tsunamis), which is composed of twenty seafloor broadband seismometers and a borehole vertical seismic array to monitor the seismic activity and the process of earthquake generation including the stress accumulation. To elucidate earthquake generation and preparation process, it is necessary to investigate how the stress could be accumulated not only in deeper part but also in the shallow sediments, what the role of interstitial fluid could be in the stress accumulation processes, etc. There are some conventional methods to measure these physical properties, such as borehole strainmeter, borehole breakouts or borehole dynamic tests. However, these methods have some difficulties from the viewpoints of technical and/or cost. For example, borehole breakouts and dynamic tests can be conducted only while drilling and/or immediately after that. Therefore we need to have some other methods to see the state and variation of the stress in the subseafloor. In this study, we applied seismic interferometry technique to ambient noise records observed by horizontal components of DONET KMD13 seafloor seismometer to obtain time dependent S-wave velocity and its anisotropy as a proxy of stress state below the DONET observatory. We first calculated cross-diploe 4-C pseudo shot records from every 1 hour ambient noise records observed by horizontal components of the DONET seismometer for three years. In obtained 4-C shot records, clear phases, which should be caused by S-wave anisotropy, are visible. Alford rotation method was then applied to the 4-C shot records to obtain S-wave anisotropy parameters, directions of fast S-wave and time lag between fast and slow S-wave velocities below the DONET observatory. We expected that our method could be a simple tool to monitor stress state in the Nankai Trough seismogenic zone.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90573465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140203
N. Tanimoto, H. Mikada, J. Takekawa
Recent years, sanding phenomenon makes some problems in resource engineering field. One of the characteristic problems is that small sand particles flow in accumulating layer and close pores of the layer. When the pore closed, sand particles prevent fluids from flowing the pore. Because of that, fluid velocity and permeability decrease. This is big problem for efficient produce of resource, so it is wanted to understand the mechanism for solve the problem. In this paper, we researched the mechanism using simulation by Smoothed Particle Hydrodynamics (SPH) method. As a result, we caught a phenomenon that sand particles close a big pore and fluid velocity decreased dynamically. We simulated in four models which has a difference of shape distribution of sand particles. We found that there is visible difference between permeability changing of these models and shape of sand particles is effective for permeability changing.
{"title":"Permeability variation due to sand particles in an infiltration flow using Smoothed Particle Hydrodynamics method","authors":"N. Tanimoto, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140203","DOIUrl":"https://doi.org/10.3997/2352-8265.20140203","url":null,"abstract":"Recent years, sanding phenomenon makes some problems in resource engineering field. One of the characteristic problems is that small sand particles flow in accumulating layer and close pores of the layer. When the pore closed, sand particles prevent fluids from flowing the pore. Because of that, fluid velocity and permeability decrease. This is big problem for efficient produce of resource, so it is wanted to understand the mechanism for solve the problem. In this paper, we researched the mechanism using simulation by Smoothed Particle Hydrodynamics (SPH) method. As a result, we caught a phenomenon that sand particles close a big pore and fluid velocity decreased dynamically. We simulated in four models which has a difference of shape distribution of sand particles. We found that there is visible difference between permeability changing of these models and shape of sand particles is effective for permeability changing.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87684394","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140202
Masaya Nagaso, H. Mikada, J. Takekawa
Hydraulic fracturing is an essential technique for the development of unconventional oil reservoirs. If fracture network formation is evaluated before a real practice of hydraulic fracturing, the permeability of the rock could be optimized after the fracturing. Since a lot of factors are involved in fracture complexity, the mechanism of fracture network formation is not fully revealed. Although the strength heterogeneities of rock mass is known to be one of the factors, strength heterogeneities is rarely taken into consideration because of less understanding of the influence on complex fracture creation. We perform a series of numerical simulation using the discrete element method and investigate the mechanism of fracture network formation, focusing on the strength heterogeneities and brittleness, which is often used as an index of fracture network formation. In heterogeneous models, complex fracture is formed by micro cracks generated around the tip of main fracture and pores with specific shape. On the other hand, in a model with high brittleness, a lot of branches are created by shear failure with main fracture propagation. These results indicate that the mechanism of complex fracture formation due to strength heterogeneities is completely different from that due to brittleness, and that the effect of the strength heterogeneities of rock should be considered as a key factor of the complication of fracture networks.
{"title":"Mechanism of complex fracure creation in hydraulic fracturing","authors":"Masaya Nagaso, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140202","DOIUrl":"https://doi.org/10.3997/2352-8265.20140202","url":null,"abstract":"Hydraulic fracturing is an essential technique for the development of unconventional oil reservoirs. If fracture network formation is evaluated before a real practice of hydraulic fracturing, the permeability of the rock could be optimized after the fracturing. Since a lot of factors are involved in fracture complexity, the mechanism of fracture network formation is not fully revealed. Although the strength heterogeneities of rock mass is known to be one of the factors, strength heterogeneities is rarely taken into consideration because of less understanding of the influence on complex fracture creation. We perform a series of numerical simulation using the discrete element method and investigate the mechanism of fracture network formation, focusing on the strength heterogeneities and brittleness, which is often used as an index of fracture network formation. In heterogeneous models, complex fracture is formed by micro cracks generated around the tip of main fracture and pores with specific shape. On the other hand, in a model with high brittleness, a lot of branches are created by shear failure with main fracture propagation. These results indicate that the mechanism of complex fracture formation due to strength heterogeneities is completely different from that due to brittleness, and that the effect of the strength heterogeneities of rock should be considered as a key factor of the complication of fracture networks.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"14 1","pages":"6"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81811126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140201
K. Okamoto, S. Tsuno
Shallow S-wave velocity structures are estimated from dispersion curves of phase velocity, H/V spectral ratios, etc., using microtremor exploration technique. However the estimation is originally based on the assumption that layers of media are horizontally stratified. So, if layers of media incline or are discontinued, the estimated structures have errors to some extent. In this study, we tested a procedure of microtremor exploration for a dipping structure and examined the influence of the horizontal stratification assumption on the estimated structure. The followings are brief description of our procedure. At first, we determined S-wave velocity structures apart from the dipping area as references using the SPatial Auto Correlation (SPAC) method. The corresponding fundamental peak frequency of Rayleigh wave ellipticity was also obtained. Using the information from the reference structures, the dipping structure was determined by the H/V spectral ratios which were obtained along the dipping structure under the assumption of the horizontal stratification. We found that the fundamental peak frequency shifts toward lower frequency smoothly as the structure becomes deeper. Using the determined structure, we numerically calculated influence range of the dip on the wave filed. As a result, it was revealed that the structure within one wavelength likely gives effect on the wave field and disturbs the H/V spectral ratios.
{"title":"Investigation of influence of dipping structures on microtremor exploration from case study research","authors":"K. Okamoto, S. Tsuno","doi":"10.3997/2352-8265.20140201","DOIUrl":"https://doi.org/10.3997/2352-8265.20140201","url":null,"abstract":"Shallow S-wave velocity structures are estimated from dispersion curves of phase velocity, H/V spectral ratios, etc., using microtremor exploration technique. However the estimation is originally based on the assumption that layers of media are horizontally stratified. So, if layers of media incline or are discontinued, the estimated structures have errors to some extent. In this study, we tested a procedure of microtremor exploration for a dipping structure and examined the influence of the horizontal stratification assumption on the estimated structure. The followings are brief description of our procedure. At first, we determined S-wave velocity structures apart from the dipping area as references using the SPatial Auto Correlation (SPAC) method. The corresponding fundamental peak frequency of Rayleigh wave ellipticity was also obtained. Using the information from the reference structures, the dipping structure was determined by the H/V spectral ratios which were obtained along the dipping structure under the assumption of the horizontal stratification. We found that the fundamental peak frequency shifts toward lower frequency smoothly as the structure becomes deeper. Using the determined structure, we numerically calculated influence range of the dip on the wave filed. As a result, it was revealed that the structure within one wavelength likely gives effect on the wave field and disturbs the H/V spectral ratios.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87517325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140197
A. Watanabe, H. Mikada, J. Takekawa
Recent years, seismic emission tomography which utilizes seismic oscillation due to fluid flow inside fractures has drawn more attention. However, the relationship between observed seismic data and fluid behavior in a reservoir has not been revealed yet. In the present study, we conduct numerical experiments for understanding the mechanism of the induced microseismic emission in order to extract more information about fluid behavior from observed seismic data. We simulate fluid flow in a fracture using the lattice Boltzmann method (LBM). We adopt two numerical models, i) parallel plate model, and ii) pore throat model. We calculate stress changes at the fracture wall induced by unsteady flow and multi-phase flow fields. The unsteady flow is generated by cyclic pressure change at the inflow boundary. In this case, inner portion of the fracture is filled only water or oil. In the multi-phase flow, we consider migration of oil droplet in a fracture with a throat filled by water. In the parallel plate model, larger shear stress change can be observed in the case of oil. This stems from more rapid change in fluid velocity close to the fracture wall due to the high viscosity of oil. In the case of the multi-phase flow in the pore throat model, about 8 Pa of shear stress and 28 Pa of normal stress are observed at the fracture wall when an oil droplet whose diameter is 1 mm passes through the pore throat. We estimate where fluid flowing using seismic wave from that stress changes. Our results show that the induced microseismic emission by fluid flow is strongly dependent on the fluid viscosity, geometry of fracture network, etc., which influences the pattern and the flux of the flow.
{"title":"Fundamental study of seismic emission tomography in terms of fluid pressure fluctuations","authors":"A. Watanabe, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140197","DOIUrl":"https://doi.org/10.3997/2352-8265.20140197","url":null,"abstract":"Recent years, seismic emission tomography which utilizes seismic oscillation due to fluid flow inside fractures has drawn more attention. However, the relationship between observed seismic data and fluid behavior in a reservoir has not been revealed yet. In the present study, we conduct numerical experiments for understanding the mechanism of the induced microseismic emission in order to extract more information about fluid behavior from observed seismic data. We simulate fluid flow in a fracture using the lattice Boltzmann method (LBM). We adopt two numerical models, i) parallel plate model, and ii) pore throat model. We calculate stress changes at the fracture wall induced by unsteady flow and multi-phase flow fields. The unsteady flow is generated by cyclic pressure change at the inflow boundary. In this case, inner portion of the fracture is filled only water or oil. In the multi-phase flow, we consider migration of oil droplet in a fracture with a throat filled by water. In the parallel plate model, larger shear stress change can be observed in the case of oil. This stems from more rapid change in fluid velocity close to the fracture wall due to the high viscosity of oil. In the case of the multi-phase flow in the pore throat model, about 8 Pa of shear stress and 28 Pa of normal stress are observed at the fracture wall when an oil droplet whose diameter is 1 mm passes through the pore throat. We estimate where fluid flowing using seismic wave from that stress changes. Our results show that the induced microseismic emission by fluid flow is strongly dependent on the fluid viscosity, geometry of fracture network, etc., which influences the pattern and the flux of the flow.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"302 1","pages":"3"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86345791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140206
Rina Yoneki, H. Mikada, J. Takekawa
We think anisotropic velocity analysis, which is known important for understanding the behavior of hydraulically generated fractures and due to stress surrounded a borehole, would be key to understand the state consolidation of sediments near the surface. There are many studies on seismic wave propagation in transversely isotropic and orthorhombic media. In the most of those studies, the magnitude of anisotropy is assumed to be weak. In addition, there are few studies on seismic wavefields in quite strongly anisotropic media. Therefore, it may not be appropriate to apply their theories directly to strongly anisotropic subsurface media. It is necessary to understand the effects of the anisotropy on the behavior of seismic wave propagation in strongly anisotropic media in the seismic exploration. In this study, we investigate the influence of strong anisotropy on received seismic waveforms using three-dimensional numerical models, and verified capability of detecting subsurface anisotropy. Our numerical models contain an isotropic and an anisotropic (transversely isotropic) layer in an isotropic background subsurface. Since the difference between the two models is only the anisotropy in the vertical propagation velocity, we could observe the influence of anisotropy in the residual wavefield that is the difference in the observed wavefields of two models. The residual waveforms could be exploited to estimate both the order of anisotropy and the thickness of anisotropic layer in subsurface.
{"title":"Numerical study for anisotropic influences on elastic wavefields near surface","authors":"Rina Yoneki, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140206","DOIUrl":"https://doi.org/10.3997/2352-8265.20140206","url":null,"abstract":"We think anisotropic velocity analysis, which is known important for understanding the behavior of hydraulically generated fractures and due to stress surrounded a borehole, would be key to understand the state consolidation of sediments near the surface. There are many studies on seismic wave propagation in transversely isotropic and orthorhombic media. In the most of those studies, the magnitude of anisotropy is assumed to be weak. In addition, there are few studies on seismic wavefields in quite strongly anisotropic media. Therefore, it may not be appropriate to apply their theories directly to strongly anisotropic subsurface media. It is necessary to understand the effects of the anisotropy on the behavior of seismic wave propagation in strongly anisotropic media in the seismic exploration. In this study, we investigate the influence of strong anisotropy on received seismic waveforms using three-dimensional numerical models, and verified capability of detecting subsurface anisotropy. Our numerical models contain an isotropic and an anisotropic (transversely isotropic) layer in an isotropic background subsurface. Since the difference between the two models is only the anisotropy in the vertical propagation velocity, we could observe the influence of anisotropy in the residual wavefield that is the difference in the observed wavefields of two models. The residual waveforms could be exploited to estimate both the order of anisotropy and the thickness of anisotropic layer in subsurface.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"18 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86811782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-05-24DOI: 10.3997/2352-8265.20140205
Tomoaki Tanaka, H. Mikada, J. Takekawa
Equivalent Offset Migration (EOM) was proposed to have both advantages of the conventional post-stack processing and velocity analysis as an alternative method to partial prestack migration, and draw attention in exploration geophysics for its computational efficiency and imaging accuracy. In the conventional EOM, it is mainly to use the vertical component of received waveforms, not horizontal components. However, it is necessary to get S-wave velocity structure in order to establish the sub-surface model including petrophysical properties. Thus, we conduct numerical experiments to verify the possibility of extracting information about S-wave velocity structure using EOM with the horizontal components. Our numerical results show that EOM based on the horizontal components can increase the amount of information of S-wave velocity whereas some unique difficulties to the horizontal components should be addressed.
{"title":"Elastic imaging of subsurface Structure with Equivalent Offset Migration for multicomponent seismic data","authors":"Tomoaki Tanaka, H. Mikada, J. Takekawa","doi":"10.3997/2352-8265.20140205","DOIUrl":"https://doi.org/10.3997/2352-8265.20140205","url":null,"abstract":"Equivalent Offset Migration (EOM) was proposed to have both advantages of the conventional post-stack processing and velocity analysis as an alternative method to partial prestack migration, and draw attention in exploration geophysics for its computational efficiency and imaging accuracy. In the conventional EOM, it is mainly to use the vertical component of received waveforms, not horizontal components. However, it is necessary to get S-wave velocity structure in order to establish the sub-surface model including petrophysical properties. Thus, we conduct numerical experiments to verify the possibility of extracting information about S-wave velocity structure using EOM with the horizontal components. Our numerical results show that EOM based on the horizontal components can increase the amount of information of S-wave velocity whereas some unique difficulties to the horizontal components should be addressed.","PeriodicalId":14836,"journal":{"name":"Japan Geoscience Union","volume":"132 1","pages":"1"},"PeriodicalIF":0.0,"publicationDate":"2016-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76663854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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