1) Cased hole seismic uses geophones lowered down wellbores to record seismic signals, providing higher resolution data than surface seismic alone.
2) A vertical seismic profile involves recording seismic signals from a surface source using downhole geophones, yielding improved resolution around the borehole.
3) Cased hole seismic tools include arrays of geophones inside tool housings that can be lowered down cased or open wellbores to record seismic waves traveling into and back out of the formations surrounding the borehole.
This document provides an overview of sub-bottom profiling and 2D high-resolution seismic techniques for geohazard investigation. It discusses the history and types of sub-bottom profilers, how they work, their resolution capabilities. Pinger, chirp, boomer and sparkers are some common sub-bottom profiler systems. 2D seismic uses streamers and air guns to obtain high resolution subsurface images down to 1 second two-way travel time. Together, these geophysical methods are used to map seabed and subsurface features that could pose geohazards, like shallow gas pockets, channels or faults, to better inform offshore engineering projects.
The document describes seismic interpretation workflows, including conventional and unconventional techniques. Conventional techniques involve horizon interpretations, fault picking, and tying seismic data to well logs to understand subsurface geology. Unconventional techniques analyze seismic attribute variations like amplitudes to identify hydrocarbon indicators. The workflow includes generating synthetics from well logs, interpreting horizons on seismic sections, identifying structures like faults and gas chimneys, and determining direct hydrocarbon indicators.
The document discusses Seascape Technical Resources, which provides marine geoscience and seafloor engineering services including multidiscipline surveys using geophysical, geotechnical and hydrographic equipment. It focuses on techniques for pipeline depth of cover surveys using subbottom profilers, echosounders, sidescan sonar, magnetometers and optionally gradiometer arrays to determine pipeline location and depth below the seafloor.
This document provides an introduction to seismic interpretation. It begins with an overview of seismic acquisition methods both onshore and offshore. It then discusses key concepts in seismic data such as common depth points, floating datum, two-way time, and the relationship between time and depth. The document also covers seismic resolution, reflection coefficients, and examples of calculating tuning thickness. Finally, it discusses important steps for seismic interpretation including checking the line scale and orientation and interpreting major reflectors and geometries.
This document describes the Wide Aperture Reflection and Refraction Profiling (WARRP) seismic method. WARRP utilizes both refracted and wide-angle reflected seismic waves to develop a detailed velocity-depth model with precisely defined velocities and interface geometries. It allows the construction of very long seismic arrays on land or offshore using autonomous recording units. This provides high-resolution travel time data and penetration to greater depths than conventional methods. The document outlines the WARRP data acquisition, processing, velocity modeling, dynamic modeling, and migration techniques to obtain accurate subsurface images.
The document discusses the methods and equipment used for near-surface seismic refraction surveying. It describes how a typical refraction survey is conducted using a seismograph, geophones in a spread, and a hammer source. The key steps covered are survey geometry, data acquisition parameters, first break picking, analysis using travel time curves, and layered velocity modeling to determine subsurface layer velocities.
The document discusses parameters for designing 2D and 3D seismic surveys. It explains that survey design aims to achieve geophysical objectives cost-effectively within time constraints. Key factors in design include target depth, resolution needs, and noise levels. Parameters that can be set include fold, offsets, bin size, and record length. The design must satisfy criteria like resolving the target, avoiding interference, and allowing for processing steps. Proper parameter selection depends on the exploration problem and existing seismic data.
The Value Proposition of 3D and 4D Marine Seismic DataTaylor Goss
An explanation of what 3D/4D Seismic is and why it is valuable for the Oil & Gas industry. How it helps to reduce risk in exploration, and helps to monitor the reservoir.
This document provides an overview of sub-bottom profiling and 2D high-resolution seismic techniques for geohazard investigation. It discusses the history and types of sub-bottom profilers, how they work, their resolution capabilities. Pinger, chirp, boomer and sparkers are some common sub-bottom profiler systems. 2D seismic uses streamers and air guns to obtain high resolution subsurface images down to 1 second two-way travel time. Together, these geophysical methods are used to map seabed and subsurface features that could pose geohazards, like shallow gas pockets, channels or faults, to better inform offshore engineering projects.
The document describes seismic interpretation workflows, including conventional and unconventional techniques. Conventional techniques involve horizon interpretations, fault picking, and tying seismic data to well logs to understand subsurface geology. Unconventional techniques analyze seismic attribute variations like amplitudes to identify hydrocarbon indicators. The workflow includes generating synthetics from well logs, interpreting horizons on seismic sections, identifying structures like faults and gas chimneys, and determining direct hydrocarbon indicators.
The document discusses Seascape Technical Resources, which provides marine geoscience and seafloor engineering services including multidiscipline surveys using geophysical, geotechnical and hydrographic equipment. It focuses on techniques for pipeline depth of cover surveys using subbottom profilers, echosounders, sidescan sonar, magnetometers and optionally gradiometer arrays to determine pipeline location and depth below the seafloor.
This document provides an introduction to seismic interpretation. It begins with an overview of seismic acquisition methods both onshore and offshore. It then discusses key concepts in seismic data such as common depth points, floating datum, two-way time, and the relationship between time and depth. The document also covers seismic resolution, reflection coefficients, and examples of calculating tuning thickness. Finally, it discusses important steps for seismic interpretation including checking the line scale and orientation and interpreting major reflectors and geometries.
This document describes the Wide Aperture Reflection and Refraction Profiling (WARRP) seismic method. WARRP utilizes both refracted and wide-angle reflected seismic waves to develop a detailed velocity-depth model with precisely defined velocities and interface geometries. It allows the construction of very long seismic arrays on land or offshore using autonomous recording units. This provides high-resolution travel time data and penetration to greater depths than conventional methods. The document outlines the WARRP data acquisition, processing, velocity modeling, dynamic modeling, and migration techniques to obtain accurate subsurface images.
The document discusses the methods and equipment used for near-surface seismic refraction surveying. It describes how a typical refraction survey is conducted using a seismograph, geophones in a spread, and a hammer source. The key steps covered are survey geometry, data acquisition parameters, first break picking, analysis using travel time curves, and layered velocity modeling to determine subsurface layer velocities.
The document discusses parameters for designing 2D and 3D seismic surveys. It explains that survey design aims to achieve geophysical objectives cost-effectively within time constraints. Key factors in design include target depth, resolution needs, and noise levels. Parameters that can be set include fold, offsets, bin size, and record length. The design must satisfy criteria like resolving the target, avoiding interference, and allowing for processing steps. Proper parameter selection depends on the exploration problem and existing seismic data.
The Value Proposition of 3D and 4D Marine Seismic DataTaylor Goss
An explanation of what 3D/4D Seismic is and why it is valuable for the Oil & Gas industry. How it helps to reduce risk in exploration, and helps to monitor the reservoir.
Many seismic sources have been developed to satisfy conflicting demands of resolution, penetration, repeatability, efficiency and cost. The Betsy seismic shotgun was developed in the late 1970s as a portable, inexpensive source for shallow reflection or refraction surveys. Field tests of the shotgun near Mymam, Alberta evaluated penetration depth, effects of acquisition parameters, and environmental effects on quality. Useful reflection data was obtained between 3-7 seconds subsurface (300-700m), with reflections at 1 second and refracted arrivals visible to 600m offsets under good conditions. Record quality depended on soil conditions, with energy coupling inversely related to soil rigidity and wind degrading quality.
This document discusses the development of an innovative logging while drilling (LWD) system using underground georadar (UGR) technology. It aims to improve navigation and maximize oil recovery from directional drilling. Key challenges include developing compact antenna designs that can operate in harsh downhole conditions and suppress leakage between antennas. The proposed system uses stepped frequency continuous wave radar with two receiving antennas to differentiate between leakage and boundary reflections. A prototype has been developed with antennas placed inside stabilizer blades to displace drilling fluid and achieve over 45dB leakage suppression without an antenna spacing. The design provides stable characteristics and anisotropic signals that can detect boundaries within 1-5m and estimate properties like propagation velocity.
The document discusses the methods for near-surface seismic refraction surveying. It describes typical equipment used including seismographs, sensors, spread cables, and sources. It outlines survey geometry considerations for sensor and source placement. It also details typical recording parameters, the analysis process of picking first breaks and inverting travel time curves, and references additional analysis techniques and software.
1) The document presents a method called Vector-acoustic Reverse-time Migration (VARTM) that can perform wavefield separation and imaging of up-going and down-going wavefields from multi-component seismic data without pre-processing for separation.
2) VARTM is applied successfully to a North Sea OBC field dataset from the Volve field, producing images without artifacts from incorrectly propagated wavefields and improving shallow section clarity compared to standard RTM.
3) In addition to imaging the up-going wavefield, VARTM can also image the down-going wavefield (mirror VARTM) without needing additional finite difference modeling.
The oxford dictionary defines an attribute as, “a quality ascribed to any person or thing”. We have extended this definition to: “seismic attributes are all the information obtained from seismic data, either by direct measurements or by logical or experience based reasoning
In reflection seismology : aseismic attributes is a quality extracted or derived from seismic data that can be analyzed in order to enhance information that might be more subtle in a traditional seismic image , leading to a better geological or geophysical interpretation of the data
Over the past decades, we have witnessed attribute developments track breakthroughs in reflector acquisition and mapping, fault identification, bright spot identification, frequency loss, thin bed tuning, seismic stratigraphy.
1) Offset refers to the horizontal distance between a seismic source and receiver. It causes a delay in the arrival time of reflections that can be corrected before stacking seismic traces.
2) Acoustic impedance is the product of density and seismic velocity, which varies between rock layers and affects the reflection coefficient at layer boundaries.
3) A seismogram contains traces recorded from a single shot point, and multiple seismograms make up a seismic section.
The analysis of all of the significant processes that formed a basin and deformed its sedimentary fill from basin-scale processes (e.g., plate tectonics)
to centimeter-scale processes (e.g., fracturing)
A Fully Automated System for Monitoring Pit Wall DisplacementsJOSE ESPEJO VASQUEZ
ABSTRACTO.
El Monitoreo automatizado de taludes empinados, excavaciones y terraplenes altos; permite la detección temprana de la inestabilidad y se puede utilizar para evitar o mitigar las posibles fallas de taludes.
Los sistemas que utilizan múltiples y diferentes tipos de sensores se han desarrollado y probado con éxito en la Mina Highland Valley Copper en la Columbia Británica. Estos sistemas utilizan estaciones totales robóticas (RTS) como principales sensores de medición, con levantamientos repetidas en intervalos predefinidos seleccionados para optimizar la eficiencia operativa.
Esta metodología ha sido desarrollada para mejorar el sistema de exactitud y fiabilidad mediante la reducción de los efectos de errores sistemáticos creados por la refracción atmosférica e instrumento inestable y posiciones de punto de referencia. La inclusión de sensores GPS para monitorear las posiciones RTS crea flexibilidad operativa adicional y mantiene la integridad del sistema cuando las estaciones de referencia disponibles son insuficientes.
This document summarizes research on developing probabilistic quantitative precipitation forecasts (PQPF) for tropical cyclone rainfall using an advection-based nowcasting system called SWIRLS. SWIRLS generates ensemble rainfall nowcasts by perturbing motion vectors estimated from radar echoes. The PQPF products include rainfall intensity contour maps showing exceedance probabilities and probability contour maps for intensity thresholds. Verification against radar data indicates the ensemble PQPFs provide fairly reliable forecasts for light to moderate rainfall and some skill in distinguishing rain from no rain. Further verification is needed for other seasons and landfalling tropical cyclones.
E & P Company DGPC hired a seismic survey company to conduct a seismic survey for a concession license. The document describes the various crews and equipment used in a land seismic data acquisition project. It details the roles of the survey, drilling, loading, layout, recording, shooting, LVL, and safety crews. It also explains the use of GPS, batteries, receivers, survey controllers, jackhammers, drilling rigs, dynamite, detonators, geophones, cables, recording trucks, monitors, recorders, and other equipment used to shoot seismic sources, record the seismic data, and ensure crew safety.
This document discusses seismic data processing concepts and computer systems used for digital filtering. It explains that seismic data recorded in the field is processed using computer programs to transform it into a usable geological record section. The processing involves steps like demultiplexing, applying static and normal moveout corrections, filtering, stacking, and other analyses to improve data quality and clarity for geological interpretation. Digital computers allow complex processing techniques to be applied to enhance seismic data and better reveal subsurface structures.
Filtering in seismic data processing? How filtering help to suppress noises. Haseeb Ahmed
To enhance the signal-Noise ratio different techniques are used to remove the noises.
Types of Seismic Filtering:
1- Frequency Filtering.
2- Inverse Filtering (Deconvolution).
3- Velocity Filtering.
This document discusses the role of seismic surveys in establishing oil and gas fields. It describes the various steps involved in seismic data acquisition, including planning, preparation, field operations such as drilling shot holes or operating vibrators, recording seismic data, and processing the data. The objectives of seismic surveys are listed as regional exploration, prospect delineation, and field development. Key factors in planning a survey include the targeted geological features, available budgets and data, and parameter selection for recording seismic signals.
The document discusses seismic instrumentation used for gathering seismic data. It describes the main components - seismic sources, sensors, and acquisition systems. For seismic data acquisition, an elastic wavefield is emitted by a source and measured by receivers along lines or on a grid. The data is then processed and interpreted. The chapter focuses on the hardware used for seismic measurements, including discussions of airgun arrays as marine sources, vibroseis and dynamite for land sources, and geophones and hydrophones as sensors. It provides an overview of how the different components contribute to the recorded seismic data.
This document outlines a simple seismic data processing workflow. It begins with acquiring field data and updating the geometry. Next steps include trace editing, amplitude recovery, and noise attenuation. Velocity analysis and normal moveout correction are then applied. Deconvolution and multiple attenuation are performed before migration. Post-migration involves stacking, filtering and amplitude scaling to produce the final processed seismic section. The goal of seismic processing is to produce high quality seismic data for geological interpretation and hydrocarbon exploration.
This document provides an introduction to seismic surveys, seismic data processing, and seismic interpretation. It discusses how seismic data is acquired onshore using vibrator trucks, explosives, or hammers, and offshore using ships that emit compressed air or other sounds. It outlines several key steps in seismic data processing to eliminate noise and reveal the subsurface, including demultiplexing, filtering, gain recovery, and stacking. The document contrasts conventional seismic interpretation, which relies on an interpreter's experience, with unconventional interpretation using attributes like amplitude, phase, and frequency to identify geobodies, structures, and direct hydrocarbon indicators.
This is for student of geophysics who want to know about basic of multi component seismic. For further detail or any query you can drop me mail, my mail id id bprasad461@gmail.com
Seismic data Interpretation On Dhodak field PakistanJamal Ahmad
I (Jamal Ahmad) presented this on 21 Feb, 2009 to defend my M.Phil dissertation in Geophysics at QAU, Islamabad, Pakistan. For more information about this, you may contact me directly at jamal.qau@gmail.com.
This document provides an overview of principles of seismic data processing. It discusses key concepts like seismic generation, data processing steps, velocity analysis, noise attenuation techniques, and common processing flows. The document is divided into multiple chapters that cover topics such as wave propagation, reflection coefficients, deconvolution, F-K transforms, and factors that affect seismic amplitudes. Specific noise types like swell noise are also explained and methods to attenuate them, such as using band-pass filters or amplitude/frequency filters, are described.
This document summarizes research on using SAR-derived sea surface winds around the Korean peninsula and their relationship to air-sea interaction. SAR imagery provides high-resolution wind data but has noise issues. The study found low winds near shore compared to offshore, supporting hypotheses about coastal meteorology. It also found evidence that land orography intensifies winds through gaps, seen in characteristic Ekman pumping structures. While noise remains a problem, SAR winds still provide meaningful ocean signals and insight into land-sea-air coupling when interpreted carefully.
This document discusses seismic reflection methods and their application to shallow subsurface exploration problems. It provides an overview of seismic reflection fundamentals, including how reflections are generated at acoustic impedance contrasts and how common depth point (CDP) processing works to enhance reflection signals. The document also discusses data acquisition parameters and challenges of shallow seismic reflection, and gives examples of applications such as mapping geologic layers, faults, and cavities.
Este documento resume Jumpshot, una herramienta para visualizar el rendimiento de programas paralelos basada en registros de bitácoras. Explica que Jumpshot permite el análisis post mortem mediante la visualización de líneas de tiempo y histogramas generados a partir de archivos de registro CLOG. También describe los requisitos para sistemas de visualización, la historia de herramientas similares y las ventajas e inconvenientes del uso de Java para implementar Jumpshot.
Many seismic sources have been developed to satisfy conflicting demands of resolution, penetration, repeatability, efficiency and cost. The Betsy seismic shotgun was developed in the late 1970s as a portable, inexpensive source for shallow reflection or refraction surveys. Field tests of the shotgun near Mymam, Alberta evaluated penetration depth, effects of acquisition parameters, and environmental effects on quality. Useful reflection data was obtained between 3-7 seconds subsurface (300-700m), with reflections at 1 second and refracted arrivals visible to 600m offsets under good conditions. Record quality depended on soil conditions, with energy coupling inversely related to soil rigidity and wind degrading quality.
This document discusses the development of an innovative logging while drilling (LWD) system using underground georadar (UGR) technology. It aims to improve navigation and maximize oil recovery from directional drilling. Key challenges include developing compact antenna designs that can operate in harsh downhole conditions and suppress leakage between antennas. The proposed system uses stepped frequency continuous wave radar with two receiving antennas to differentiate between leakage and boundary reflections. A prototype has been developed with antennas placed inside stabilizer blades to displace drilling fluid and achieve over 45dB leakage suppression without an antenna spacing. The design provides stable characteristics and anisotropic signals that can detect boundaries within 1-5m and estimate properties like propagation velocity.
The document discusses the methods for near-surface seismic refraction surveying. It describes typical equipment used including seismographs, sensors, spread cables, and sources. It outlines survey geometry considerations for sensor and source placement. It also details typical recording parameters, the analysis process of picking first breaks and inverting travel time curves, and references additional analysis techniques and software.
1) The document presents a method called Vector-acoustic Reverse-time Migration (VARTM) that can perform wavefield separation and imaging of up-going and down-going wavefields from multi-component seismic data without pre-processing for separation.
2) VARTM is applied successfully to a North Sea OBC field dataset from the Volve field, producing images without artifacts from incorrectly propagated wavefields and improving shallow section clarity compared to standard RTM.
3) In addition to imaging the up-going wavefield, VARTM can also image the down-going wavefield (mirror VARTM) without needing additional finite difference modeling.
The oxford dictionary defines an attribute as, “a quality ascribed to any person or thing”. We have extended this definition to: “seismic attributes are all the information obtained from seismic data, either by direct measurements or by logical or experience based reasoning
In reflection seismology : aseismic attributes is a quality extracted or derived from seismic data that can be analyzed in order to enhance information that might be more subtle in a traditional seismic image , leading to a better geological or geophysical interpretation of the data
Over the past decades, we have witnessed attribute developments track breakthroughs in reflector acquisition and mapping, fault identification, bright spot identification, frequency loss, thin bed tuning, seismic stratigraphy.
1) Offset refers to the horizontal distance between a seismic source and receiver. It causes a delay in the arrival time of reflections that can be corrected before stacking seismic traces.
2) Acoustic impedance is the product of density and seismic velocity, which varies between rock layers and affects the reflection coefficient at layer boundaries.
3) A seismogram contains traces recorded from a single shot point, and multiple seismograms make up a seismic section.
The analysis of all of the significant processes that formed a basin and deformed its sedimentary fill from basin-scale processes (e.g., plate tectonics)
to centimeter-scale processes (e.g., fracturing)
A Fully Automated System for Monitoring Pit Wall DisplacementsJOSE ESPEJO VASQUEZ
ABSTRACTO.
El Monitoreo automatizado de taludes empinados, excavaciones y terraplenes altos; permite la detección temprana de la inestabilidad y se puede utilizar para evitar o mitigar las posibles fallas de taludes.
Los sistemas que utilizan múltiples y diferentes tipos de sensores se han desarrollado y probado con éxito en la Mina Highland Valley Copper en la Columbia Británica. Estos sistemas utilizan estaciones totales robóticas (RTS) como principales sensores de medición, con levantamientos repetidas en intervalos predefinidos seleccionados para optimizar la eficiencia operativa.
Esta metodología ha sido desarrollada para mejorar el sistema de exactitud y fiabilidad mediante la reducción de los efectos de errores sistemáticos creados por la refracción atmosférica e instrumento inestable y posiciones de punto de referencia. La inclusión de sensores GPS para monitorear las posiciones RTS crea flexibilidad operativa adicional y mantiene la integridad del sistema cuando las estaciones de referencia disponibles son insuficientes.
This document summarizes research on developing probabilistic quantitative precipitation forecasts (PQPF) for tropical cyclone rainfall using an advection-based nowcasting system called SWIRLS. SWIRLS generates ensemble rainfall nowcasts by perturbing motion vectors estimated from radar echoes. The PQPF products include rainfall intensity contour maps showing exceedance probabilities and probability contour maps for intensity thresholds. Verification against radar data indicates the ensemble PQPFs provide fairly reliable forecasts for light to moderate rainfall and some skill in distinguishing rain from no rain. Further verification is needed for other seasons and landfalling tropical cyclones.
E & P Company DGPC hired a seismic survey company to conduct a seismic survey for a concession license. The document describes the various crews and equipment used in a land seismic data acquisition project. It details the roles of the survey, drilling, loading, layout, recording, shooting, LVL, and safety crews. It also explains the use of GPS, batteries, receivers, survey controllers, jackhammers, drilling rigs, dynamite, detonators, geophones, cables, recording trucks, monitors, recorders, and other equipment used to shoot seismic sources, record the seismic data, and ensure crew safety.
This document discusses seismic data processing concepts and computer systems used for digital filtering. It explains that seismic data recorded in the field is processed using computer programs to transform it into a usable geological record section. The processing involves steps like demultiplexing, applying static and normal moveout corrections, filtering, stacking, and other analyses to improve data quality and clarity for geological interpretation. Digital computers allow complex processing techniques to be applied to enhance seismic data and better reveal subsurface structures.
Filtering in seismic data processing? How filtering help to suppress noises. Haseeb Ahmed
To enhance the signal-Noise ratio different techniques are used to remove the noises.
Types of Seismic Filtering:
1- Frequency Filtering.
2- Inverse Filtering (Deconvolution).
3- Velocity Filtering.
This document discusses the role of seismic surveys in establishing oil and gas fields. It describes the various steps involved in seismic data acquisition, including planning, preparation, field operations such as drilling shot holes or operating vibrators, recording seismic data, and processing the data. The objectives of seismic surveys are listed as regional exploration, prospect delineation, and field development. Key factors in planning a survey include the targeted geological features, available budgets and data, and parameter selection for recording seismic signals.
The document discusses seismic instrumentation used for gathering seismic data. It describes the main components - seismic sources, sensors, and acquisition systems. For seismic data acquisition, an elastic wavefield is emitted by a source and measured by receivers along lines or on a grid. The data is then processed and interpreted. The chapter focuses on the hardware used for seismic measurements, including discussions of airgun arrays as marine sources, vibroseis and dynamite for land sources, and geophones and hydrophones as sensors. It provides an overview of how the different components contribute to the recorded seismic data.
This document outlines a simple seismic data processing workflow. It begins with acquiring field data and updating the geometry. Next steps include trace editing, amplitude recovery, and noise attenuation. Velocity analysis and normal moveout correction are then applied. Deconvolution and multiple attenuation are performed before migration. Post-migration involves stacking, filtering and amplitude scaling to produce the final processed seismic section. The goal of seismic processing is to produce high quality seismic data for geological interpretation and hydrocarbon exploration.
This document provides an introduction to seismic surveys, seismic data processing, and seismic interpretation. It discusses how seismic data is acquired onshore using vibrator trucks, explosives, or hammers, and offshore using ships that emit compressed air or other sounds. It outlines several key steps in seismic data processing to eliminate noise and reveal the subsurface, including demultiplexing, filtering, gain recovery, and stacking. The document contrasts conventional seismic interpretation, which relies on an interpreter's experience, with unconventional interpretation using attributes like amplitude, phase, and frequency to identify geobodies, structures, and direct hydrocarbon indicators.
This is for student of geophysics who want to know about basic of multi component seismic. For further detail or any query you can drop me mail, my mail id id bprasad461@gmail.com
Seismic data Interpretation On Dhodak field PakistanJamal Ahmad
I (Jamal Ahmad) presented this on 21 Feb, 2009 to defend my M.Phil dissertation in Geophysics at QAU, Islamabad, Pakistan. For more information about this, you may contact me directly at jamal.qau@gmail.com.
This document provides an overview of principles of seismic data processing. It discusses key concepts like seismic generation, data processing steps, velocity analysis, noise attenuation techniques, and common processing flows. The document is divided into multiple chapters that cover topics such as wave propagation, reflection coefficients, deconvolution, F-K transforms, and factors that affect seismic amplitudes. Specific noise types like swell noise are also explained and methods to attenuate them, such as using band-pass filters or amplitude/frequency filters, are described.
This document summarizes research on using SAR-derived sea surface winds around the Korean peninsula and their relationship to air-sea interaction. SAR imagery provides high-resolution wind data but has noise issues. The study found low winds near shore compared to offshore, supporting hypotheses about coastal meteorology. It also found evidence that land orography intensifies winds through gaps, seen in characteristic Ekman pumping structures. While noise remains a problem, SAR winds still provide meaningful ocean signals and insight into land-sea-air coupling when interpreted carefully.
This document discusses seismic reflection methods and their application to shallow subsurface exploration problems. It provides an overview of seismic reflection fundamentals, including how reflections are generated at acoustic impedance contrasts and how common depth point (CDP) processing works to enhance reflection signals. The document also discusses data acquisition parameters and challenges of shallow seismic reflection, and gives examples of applications such as mapping geologic layers, faults, and cavities.
Este documento resume Jumpshot, una herramienta para visualizar el rendimiento de programas paralelos basada en registros de bitácoras. Explica que Jumpshot permite el análisis post mortem mediante la visualización de líneas de tiempo y histogramas generados a partir de archivos de registro CLOG. También describe los requisitos para sistemas de visualización, la historia de herramientas similares y las ventajas e inconvenientes del uso de Java para implementar Jumpshot.
El documento describe técnicas para mejorar el algoritmo de eliminación gaussiana (GE) para resolver sistemas de ecuaciones lineales densos. Explica cómo optimizar GE mediante el uso de operaciones de matrices (BLAS) en lugar de bucles anidados, almacenando factores de multiplicación en lugar de recalcularlos, y aplicando pivotaje parcial para mejorar la estabilidad numérica. También describe cómo GE en realidad calcula una factorización LU de la matriz y cómo esta factorización puede usarse para resolver el sistema de ecuaciones.
Este documento presenta un resumen de los conceptos fundamentales del método numérico Multigrid para resolver ecuaciones diferenciales parciales discretizadas. Explica que Multigrid divide y resuelve recursivamente el problema en mallas más gruesas para mover la información más rápido a través de la malla. Describe los operadores clave de restricción, interpolación y solución, y cómo se usan en un ciclo V y el algoritmo Full Multigrid para lograr convergencia constante independiente del tamaño de la malla.
Este documento describe el uso de computación paralela y distribuida a través de una red de computadoras conocida como Grid. Explica cómo herramientas como MPI y el Globus Toolkit permiten ejecutar aplicaciones paralelas en múltiples máquinas de forma coordinada. También presenta ejemplos de cómo programar aplicaciones MPI para usar los servicios del Globus Toolkit y ejecutar en una red Grid.
Este documento describe varios métodos numéricos para calcular integrales definidas, incluyendo las reglas de la trapezoidal, Simpson y Monte Carlo. Explica cómo aplicar estos métodos de forma paralela usando múltiples procesadores, donde cada procesador calcula una porción de la integral total. También discute cómo mejorar la precisión del método de Monte Carlo usando una distribución de muestreo no uniforme guiada por la función a integrar.
Este documento resume las operaciones paralelas con matrices densas y el algoritmo de Cannon para la multiplicación de matrices. En 3 oraciones o menos:
El documento describe diferentes particiones de datos para operaciones paralelas con matrices densas, incluidas particiones de bloques y cíclicas de filas y columnas. También explica el algoritmo de Cannon para la multiplicación paralela de matrices, el cual mueve bloques de las matrices A y B para alinear los datos y permitir la multiplicación en paralelo de todos los procesadores.
Este documento resume los conceptos clave de la simulación paralela. Explica que los sistemas de eventos discretos, partículas y variables agregadas que siguen ecuaciones diferenciales ordinarias son comunes en simulaciones y pueden ser paralelizados. Describe cómo identificar dependencias de datos y flujo para determinar qué partes de un problema se pueden computar en paralelo, y métodos como la descomposición de dominio espacial para lograr paralelismo y localidad en la comunicación.
Este documento presenta varios métodos para resolver sistemas de ecuaciones diferenciales parciales, como la ecuación de Poisson. Revisa el método de Jacobi, el método SOR rojo y negro, el gradiente conjugado y la transformada rápida de Fourier. Luego explica cómo estos métodos pueden ser paralelizados para resolver sistemas de ecuaciones a gran escala de manera más eficiente.
Este documento presenta un resumen de diferentes modelos de programación y computación paralela. Describe modelos de memoria compartida y distribuida, así como el uso de hilos para la programación paralela. También analiza problemas como las carreras de datos y el falso compartir de memoria al escalar arquitecturas de memoria compartida.
Este documento introduce el concepto de computación paralela de alto rendimiento y sus aplicaciones. Explica que la simulación por computadora se ha convertido en el tercer pilar de la ciencia junto con la teoría y el experimento. Detalla algunos problemas computacionalmente intensivos como la simulación del clima global y la dinámica de agujeros negros binarios. Finalmente, señala que las tendencias de miniaturización hacen que los microprocesadores sean cada vez más paralelos para aprovechar el aumento exponencial en el número de transistores.
Approach of signature_hole_vibration_monitoring_and_modeling_for_quarry_vibra...Jordán López Ortiz
An integrated approach of signature hole vibration monitoring and modeling was used to control blast vibrations at a quarry near an urban boundary. Signature holes were monitored to determine ground properties including sonic velocity and resonant frequency. Production blast vibrations were also monitored. This data was used in a multiple seed waveform vibration model to optimize blast design parameters like charge weight per delay. The optimized blast designs effectively managed vibrations below limits while maintaining productivity. Model predictions matched well with field measurements, demonstrating the effectiveness of the integrated monitoring and modeling approach.
Seismic Modeling ASEG 082001 Andrew LongAndrew Long
This document discusses tools for modeling elastic wave propagation to aid in seismic survey planning. It summarizes three main modeling techniques: recursive reflectivity methods, ray tracing methods, and full wavefield methods using finite-differencing. Ray tracing is useful for optimizing survey geometry but not reflectivity studies, while reflectivity and finite-difference methods model full wavefields and are better for amplitude studies like AVO. Integrating these modeling tools with real data and rock physics analysis allows comprehensive understanding of wave propagation for effective survey planning addressing all acquisition parameters and seismic phenomena.
GeoStreamer PESA News 042009 Andrew LongAndrew Long
This document discusses dual-sensor streamer technology innovations. It summarizes that:
1) Dual-sensor streamers, which record both pressure and velocity data, allow streamers to be towed much deeper (15-25m) without compromising data quality or frequency content. This provides greater operational flexibility and noise reduction.
2) By properly combining pressure and velocity recordings, dual-sensor processing can perfectly remove receiver "ghost" reflections across all frequencies and angles of incidence. This improves temporal resolution over conventional streamers.
3) Field tests in Australia found dual-sensor data contained stronger amplitudes at both high and low frequencies. It provided cleaner, higher resolution images in shallow waters and enhanced continuity,
TGS's proprietary Clari-Fi technique enables the generation of broadband pre-stack seismic data from conventionally acquired marine seismic data using streamers. It is a three-step process that first suppresses ghosts and boosts low frequencies. It then solves for the earth's attenuation by accurately measuring effective Q. Finally, it performs multi-domain noise attenuation to broaden the signal spectrum without broadening noise. This results in seismic images with increased bandwidth, resolution, and clarity of geological features compared to standard processing.
This document compares methods for determining subsurface shear-wave velocity, which is important for seismic hazard assessment. It analyzes data from seismic cone penetration tests (SCPT), spectral analysis of surface waves (SASW), continuous surface wave system (CSWS), and microtremors in the Victoria, Canada area. The peak frequencies determined from SCPT measurements generally agree well with microtremor measurements, as both sample to similar depths. Surface wave methods like SASW and CSWS have more limited depth penetration and thus microtremor frequencies are sometimes lower. Combining microtremors with invasive or active non-invasive methods provides the best characterization of site response.
Time-Frequency Attenuation of Swell Noise on Seismic Data from Offshore Centr...iosrjce
Diversity of noise types with different characteristics makesseparation of signal and noise a
challenging process.Swell noiseusually contaminates tracesand it is characterized by high amplitude and low
frequencies and affects only a limited band offrequencies.This work presents how FX projection filter (FXEDIT
code) processing approach was used to attenuate swell noise on dataset from a marine seismic survey
offshoreCentral Niger-Delta, Nigeria, which shows as an effective amplitude preserving and robust tool that
gives better results compared to many other conventional filtering algorithms.With this processing approach
and working side-by-side with the shot gather and the RMS windows; the results achieved are reliable and
satisfactory by giving clearer images for reservoir characterization. The level of swell noise attenuation after
this approach greatly increased the confidence to use the data for subsequent processing steps.
This document summarizes the results of field tests comparing different geophone configurations for onshore seismic data acquisition using cable-free nodal recording systems. The tests found that:
1) Fully burying the nodal recording systems significantly improved data quality over partially burying or leaving nodes on the surface.
2) Data quality from fully buried nodes was similar to that from nodes connected to a single external geophone.
3) While geophone arrays reduced noise, point receiver nodes provided equivalent signal quality after simple stacking, showing arrays are not necessary with nodal systems.
4) Bunched arrays of multiple geophones connected to nodes performed similarly to fully buried nodes alone.
The document summarizes research on using seismic methods to detect and characterize a sinkhole in Doha, Qatar. A seismic survey was conducted along the edge of the sinkhole opening. The recorded seismic data revealed a distinct resonance peak at 70 Hz above the sinkhole. Numerical modeling showed that this peak is indicative of a karst side wall separating rock, karst border, and roof. The data were inverted in the frequency domain and fit using a model with low velocity and density parameters in the sinkhole layer, representing the complex geometry of karst.
This document summarizes a technique called structure-oriented, frequency-dependent (SOFD) filtering that can significantly increase the usable bandwidth of seismic data. The technique uses structure tensors computed from a stack to guide frequency-dependent filtering of individual frequency bands. This preserves structural features while improving signal-to-noise. The technique is demonstrated on land seismic data, improving signal quality at low and high frequencies. Well ties show the enhanced bandwidth data matches well logs, extending usable frequencies without degrading tie quality. The technique can be applied to pre-stack data by filtering offset volumes separately.
2D MASW ANALYSIS FOR GEOTECHNICAL ENGINEERINGAli Osman Öncel
This document describes a study that used seismic refraction and multi-channel analysis of surface waves (MASW) to investigate near-surface shear wave velocities at a site in Egypt. Seismic refraction was used to determine P-wave velocities down to depths of 30 m. MASW was used to determine 1D and 2D shear wave velocity profiles by analyzing Rayleigh surface wave dispersion. Shear wave velocities obtained from MASW were used to evaluate site response and classify the site according to standard site classifications. The study area consists of Quaternary deposits overlying Tertiary sedimentary rocks. P-wave and MASW surveys were conducted along multiple profiles using geophones and a seismograph to
This document discusses and compares different technologies for modern land seismic recording systems, including geophone arrays versus point receivers, cable-based versus cable-less systems, and 1C versus 3C sensors. It finds that while point receivers and cable-less systems can provide benefits at coarse spatial sampling, geophone arrays and cable-based systems have advantages at finer sampling intervals, including improved signal-to-noise ratio and quality control. The optimal technology depends on the specific survey needs and parameters. Weight analysis shows cable-based systems have lower weight at sampling intervals under around 50 meters.
Delineating faults using multi-trace seismic attributes: Example from offshor...iosrjce
1) The document describes a workflow for delineating faults in a 3D seismic dataset from offshore Niger Delta using multi-trace seismic attributes.
2) Dip-steering and multi-trace similarity attributes were computed to highlight discontinuities and improve fault detection. This revealed a major NE-SW trending strike-slip fault separating compressional deformation to the north and extensional deformation to the south.
3) Vertical cross-sections show faults and fault zones are more clearly resolved when computing multi-trace similarity along structural dips using dip-steering, rather than directly from seismic reflectivity alone.
02 chapter: Earthquake: Strong Motion and Estimation of Seismic HazardPriodeep Chowdhury
This document discusses strong ground motion from earthquakes and methods for measuring and analyzing it. It describes how modern accelerographs can record ground acceleration digitally up to 100 Hz. Parameters derived from ground motion records are used to analyze earthquake and site characteristics and their impact on structures. Evaluating seismic hazard requires understanding characteristics controlling ground motion as well as the seismicity and tectonics of the surrounding region, using either deterministic or probabilistic approaches.
This document describes how multichannel analysis of surface waves (MASW) was used to map variations in bedrock and detect potential fractures at a site in Olathe, Kansas where industrial contaminants may have leaked. MASW data was acquired along linear profiles using standard seismic acquisition techniques. Analysis of surface wave dispersion characteristics generated a 2D shear wave velocity model that accurately mapped the bedrock surface between 6-23 feet deep and identified potential fracture zones in the bedrock. The high resolution shear wave velocity model provided essential information for characterizing subsurface fluid flow at the contaminated site.
Modern seismic data processing techniques can provide accurate pore pressure prediction in areas lacking well data. In a case study from the Caspian Sea, prestack depth migration was used to generate a detailed velocity model which was calibrated to existing well data and used to predict pore pressure in an undrilled area 36 miles away. The velocity model was filtered, converted to interval velocities, and further calibrated through cross-plotting and kriging with well data before being used to calculate pore pressure volumes through established methods. The predicted pore pressures compared well to measurements from new wells drilled, demonstrating the ability of advanced seismic analysis to characterize subsurface conditions in frontier areas.
Quantitative and Qualitative Seismic Interpretation of Seismic Data Haseeb Ahmed
This document discusses quantitative and qualitative seismic interpretation techniques used to analyze seismic data and map subsurface geology. It compares traditional qualitative techniques to more modern quantitative techniques. It then focuses on unconventional seismic interpretation techniques used for unconventional reservoirs with low permeability, including AVO analysis, seismic inversion, seismic attributes, and forward seismic modeling. These techniques can help identify tight gas, shale gas, and gas hydrate reservoirs that conventional methods cannot easily detect. The document provides details on how each technique works and its advantages.
This document provides an introduction to analyzing seismic records and extracting parameters for data exchange and research. It discusses analyzing analog and digital records from single stations and networks to identify phases, determine onset times, amplitudes, periods, and other parameters. These procedures are now often automated but traditionally involved manual analysis. The document outlines challenges like noise, dispersion, and differences between body and surface waves. It emphasizes the importance of understanding seismic wave propagation and record characteristics for accurate interpretation.
AirSwot is an airborne radar system called KaSPAR that will be used to calibrate and validate the SWOT satellite mission. KaSPAR will make high-accuracy elevation maps with a 5km swath from an altitude of 35,000 feet to replicate SWOT's measurements over various terrain. It will also gather additional data on water temporal correlation, elevation, backscatter, and vegetation attenuation to help classify landscapes and predict SWOT's performance. The system draws on heritage from previous airborne radars and will fly on the NASA King Air to begin engineering flights in 2012 for SWOT calibration prior to its launch.
Echosounding ,shallow seismic reflection and underwater sonographic investiga...Sabna Thilakan
The document discusses various geophysical techniques used for construction of offshore structures, including echo sounding, side scan sonar, and high resolution seismic reflection methods. It provides details on echo sounding methodology, including sound propagation in water, acoustic parameters of echo sounders, and processing and presentation of bathymetry data. It also describes the working principles, components, and data processing of side scan sonar systems, and factors that affect the interpretation of sonar images. The objective is to understand the fundamentals and applications of these techniques for studying seabed and sub-seabed features in near offshore regions.
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1. CasedHole Seismic
In the early stagesof planning exploration anddevelopment
in a new area, surfaceseismicsurveysare usedextensively
to delineateprospectivestructural or stratigraphictraps. Re-
cent improvementsin digital filtering and processingtech-
niqueshaveled to high-quality resultsunder favorablecon-
ditions. The resolutionof surfaceseismicsurveys,however,
is still fundamentallylimited by low operating frequencies.
When wells aredrilled, opportunitiesexistto improve this
situation through the use of well logs. After editing and
calibrating againstcheck shots, openholesonicand density
logscanbeusedto generatesyntheticseismograms.If open-
hole dataare not available, in many instancesa casedhole
sonic log canbe recordedfor this purpose(seeChapter 3).
Thesesyntheticsare extremely valuablein verifying reflec-
tion eventsin a seismicsectionandrelating seismicfeatures
to geologicalstructures.Velocity anomalies,whichmaycause
exploration wellsto bedrilled off-structure, canberesolved.
A more recentgeophysicalapplicationof wireline logging
measurementsinvolves thepreparationof a vertical seismic
profile (VSP). In this technique,anair gunvibroseis,or other
seismicsourceon the surfacegeneratesthe input signalthat
is detectedby a downhole geophone.As the soundenergy
travels only oncethrough the weatheredsurfacelayers, the
resultantprofile hasmuch better resolution thanthe surface
seismic around the borehole, and, in favorable cases,can
identify reflectors far below the total depth of the well.
Unlike many wireline services, openholeand casedhole
seismicresultsare similar sincethecasingtypically doesnot
affect the seismicsignal. In fact, casedholeseliminate some
of the openholeoperational problems associatedwith poor
hole conditionsandhighly deviatedwells. Also, specialmul-
tisensorarray tools for VSP acquisitioncanbeusedin cased
holes that are not practical for openholeoperations.
CASED HOLE SEISMIC EQUIPMENT
Theequipmentshownin Fig. 9-l consistsof adownholetool
with geophones,the CSU surfacerecording system,offset
shooting equipment, and an air gun system.
The most commonly usedenergy source offshore is the
air gun. Its safety, reliability, cost, broad spectrum, simple
signature,andtransportability maketheair gunaconvenient
seismic source. An array of synchronized air guns can be
usedif a large power output for deeperpenetrationis need-
ed. The air gun firing chambersmay incorporate a wave-
shapingkit that significantly reducesthe bubble effect and
provides aclean signal. The air compressorandair storage
bottles provide anadequateair supply for fast, uninterrupt-
edoperations.Other soundsources,suchasvibroseisunits,
are routinely usedin the field dependingon specific appli-
cations and local conditions.
When using an impulsive sourcesuchasan air gun, the
source signal is recorded at the surfaceby a hydrophone.
This allows a precise determination of the time break and
permits continuous monitoring of the gun signature. The
recorded source signature is used to enhancethe signals
recorded by the geophonein VSP processing.
The dataare recordeddigitally on magnetictapewith the
CSU system. The seismic waveforms can also be stacked
to improve the signal-to-noise ratio.
The downholetools currently in useare theWell Seismic
Tool (WST*), theSeismicAcquisition Tool (SAT*), andthe
Downhole SeismicArray tool (DSA*). The WST tool has
four uniaxially stackedgeophonesthat are primarily sensi-
tive to movementin thevertical direction. The SAT tool has
three mutually orthogonal geophones(which may also be
gimbal-mountedfor usein deviatedwells) for 3dimensional
operation. This arrangementprovides an x, y, z systemof
referencewhere eacharriving ray can be representedby a
vector. Among other applications, the ability to record and
processsignals in three axes allows the recording and in-
terpretationof shearwaves,saltproximity surveys,andlong-
offset VSP surveys.The DSA tool (Fig. 9-2) useseight sen-
sor packages(shuttles)which are positioned along an insu-
latedmulticonductor bridle cableat intervals of up to 50 ft.
The sensorpackagecontainsa vertical geophonefor signal
acquisition, a magneticclamping deviceto securethe pack-
age to the casing, a shakerelementto generatemechanical
vibrations for reference,andelectronic circuitry to transmit
9-l
3. Fig. 9-e--Schematic of DSA tool in operation
signals to the cartridge. In the cartridge, the signals pass
through antialiasing filters, sample-holdcircuits, and mul-
tiplexers, andare then digitized andtelemeteredto the sur-
face. The tool canbe combinedwith a casingcollar locator
for depth control.
DIGITAL CHECK-SHOT SURVEY
At eachdepth,theinterval velocity of theformationsbetween
the sourceandtheborehole geophoneis measured.With an
air gun source, the hydrophone monitors the signatureand
timing of the source signal, and the downhole geophone
records the direct and reflected arrivals.
Transit time is measuredfrom thefirst breakof thehydro-
phone(surface)recording to the first break of the geophone
(downhole) recording. Severalshotsareusually madeatthe
CASED HOLE SEISMIC
samelevel andstackedin orderto improvethesignal-to-noise
ratio.
If the hole is deviated or if there is a significant source
offset, the transit times obtained must be converted to true
vertical depth (TVD) transit times. Correction to the seis-
mic referencedatum (SRD) is also necessaryif the source
is aboveor below the seismicdatum.The corrected,stacked
magnetictapedatacanthenbeconvertedto a standardSEG-
Y tape format.
TIME-TO-DEPTH CONVERSION AND
VELOCITY PROFILE
Check-shotsurveysareusedto correctthevelocitiesobtained
by theintegration of the sonicinterval transit times. The ad-
justed sonicmay then be usedfor the translation of surface
seismictime into depth and in the calculation of formation
acoustic impedance necessary for the generation of a
Geogram* syntheticseismogramandfor other applications.
Formation velocities obtainedby the integration of sonic
logs may differ from thoseobtainedby surfaceand check-
shot surveys for the following reasons:
l Becauseof velocity dispersionwith frequency,seismicve-
locities (measuredat roughly 50 Hz) may be asmuch as
6% lower than sonicvelocities (measuredat 20,000 Hz).
l Borehole effects, suchas thosecausedby formation al-
teration, may decreasethe apparentsonic log velocities.
l The sonic transit time measurementis fundamentally
different from the surfaceseismicmeasurement.The sonic
log velocity is measuredin a continuousmanner along-
side the borehole, while the seismicwaves reaching the
geophone(s)takethe mostdirect acoustic(shortest)path.
The long-spaced(LSS) or Array-Sonic tools are required
for casedhole logs andprovide betterdatathanBHC sonics
in openholes. However, all recorded sonic logs should be
edited to correct for borehole effects. To adjust a sonic log
correctly, check shotsare required, Check shotsshouldbe
made at the SRD, at the tops of significant formations, at
the top of the sonic log, and spacednot greater than 500 ft
apart.
Seismictime is normally referencedfrom thecheckshots,
and sonic log measurementsare adjustedaccordingly. The
adjustmentconsistsof computingthe raw drift, selectingthe
drift curve, adjustingthe soniclog, andcheckingthe validi-
ty of the result.
Raw drift is defined asthe correct shottime minus the in-
tegratedsonictime. Theselecteddrift curve is derived from
the raw drift values. The kneesof the selecteddrift curve
are usually locatedat changesin lithology , borehole condi-
tions, soniclog character,andthe drift data. The correction
determinedby the selecteddrift curve is distributed to the
sonic transit times over the interval defined by consecutive
9-3
4. CASED HOLE LOG INTERPRETATION PRINCIPLESIAPPLICAT
knees.The checkof the adjustedsonicis madeby ensuring
that the integrated sonic time and the corrected shot time
agreeat eachshooting level within the accuracyof the shot
time. Obviously, themore checkshots,the moreaccurately
this can be done.
A sectionof a sonic calibration log is shown in Fig. 9-3.
The uncalibrated transit time, calibrated transit time, and
gamma ray curve are displayed along with bulk density,
spontaneouspotential,anddifferential caliperdatafrom open-
holelogs. In theleft track, vertical depth,shotnumbers,cor-
rectedshottimes, uncorrectedl-way integratedsonictimes,
and corrected 2-way integratedsonic times are displayed.
In addition to providing data for sonic calibration, check
shotsallow a time-to-depth conversionto bemadewhen no
sonic log hasbeenrecorded. A similar, related application
is the determination of the weathering correction and the
thickness of the weatheredzone.
GEOGRAM PROCESSING
The seismic waveforms propagating through the earth are
affectedby eachlithologic bedboundary.Specifically, at the
interface of two formations of contrasting acoustic im-
pedances,part of the energy will be transmitted acrossthe
interface andsomewill bereflected. The amountof seismic
energytransmittedandreflecteddependson theacousticim-
pedancecontrastbetweenthetwo formationbeds.The acous-
tic impedanceof a formation, Z,, is given as:
z, = PV 9 (Eq. 9-l)
wherep is theformation densityandv is its interval velocity.
The amountof reflectedenergybetweentwo adjacentbeds
dependson the relative impedancesof the two beds. The
reflection coefficient, R, is defined as:
412 - TX1
% = za2 + z ’
a1
(Eq. 9-2)
where Z% andZal are the acousticimpedancesof layers 2
and 1.
The subsurfacecanbe approximatedfor seismicpurposes
by a seriesof layers having specific acoustic impedances,
which can be usedto produce a seriesof reflection coeffi-
cients at the boundaries(Fig. 9-4). Sincea sonic log mea-
suresacousticvelocity andadensity log measuresbulk den-
sity, the sonic and density logs canbe usedto computethe
reflectivity series,which canthenbeconvolvedwith a suita-
ble wavelet. The result is a Geogram display (synthetic
seismogram).
Geogramprocessingproducesanideal seismictraceonly
if the sonic and density logs have beenproperly recorded,
edited, andadjustedto representthesubsurfaceundisturbed
by drilling. Special programs allow the recomputation of
sonic velocities and bulk densities, taking into accountthe
Fig. Q-3-Sonic calibration log
5. CASED HOLE SEISMIC
Fig. 9-4-Ideal seismic record giving position (in time) of
reflector and value (amplitude) of reflection coefficient
effect of the invaded zone; this is particularly important in
gas-bearingformations.Geogramprocessingenablesqualita-
tive correlations aswell asquantitative evaluationsof seis-
mic data to be made.
The Geogramprocessingsequenceis shownin Fig. 9-5.
The first two steps,which involve editing and sonicadjust-
ments,arc normally madeduring thetime-to-depthconver-
sion. Oncethereflectivity seriesandtransmissionlosseshave
beencomputed,the decision must bemadeon what type of
wavelet to usefor convolution. In order to give the bestap-
proximation of theactualsourcesignature,severalwavelets
arcavailable.TheseincludeRicker minimum- or zero-phase,
Klauder, spikewith Butterworth filter, or otheruser-defined
operators.
The Geogramdisplay canbemadewith or without multi-
ples and/or transmission losses,and with any desired fre-
quency or bandof frequencies.A typical Geogramdisplay
is shown in Fig. 9-6.
The structural dip, asinterpretedfrom adipmetersurvey,
canbe incorporatedinto the presentationto permit theGeo-
gram resultsto be projectedaway from the well (Fig. 9-7).
A Geogramdisplay canhelp in the qualitative evaluation
of the seismic sectionsby providing the following:
l an ideal seismictraceasa referencefor the surfaceseis-
mic data
. time-to-depth conversions
. detection of multiples
. seismic character correlation
* direct correlation with log intervals.
Seismic modeling can also be enhancedand processing
time decreasedby assuminga realistic model basedon the
Geogram computation. The original log data canbe modi-
fied andusedto generatenew syntheticseismictraces.Other
applicationsareinversemodelingandthedesignof thedecon-
volution operator. Furthermore, any log data, raw data, or
Fig. B-5-Geogram processing chain
processeddatacanbepresentedon a time scalefor correla-
tion with the seismic data.
VERTICAL SEISMIC PROFILE
Vertical seismicprotiling is a techniqueof simultaneously
recording theupgoinganddowngoingwavetrains(Fig. 9-8).
This representsa major advantageover theconventionalsur-
facereflection seismictechnique,which recordsonly theup-
going waves.By recording a sufficient number(50 or more)
of fairly regularly spacedlevels in the well, theupgoing and
downgoingwavefieldscanbeseparatedby computerproccss-
ing. An analysisof theupgoing anddowngoing components
permits the detailed study of the change of the seismic
wavetrain with depth. The acousticproperties of the earth
canthenbedirectly linked to andinterpretedin termsof the
subsurfacelithology. The useof downhole sensorsreduces
the signaldistortion causedby the low-velocity shallow lay-
ers since the signal passesonly once through the surface
layers.
The total wavefield recorded at the detector in the bore-
hole consists of signals arriving from above the tool
6.
7. CASED HOLE SEISMIC
Well
2-Way Time
i 4
0.2 0.2
0.6 0.6
0.8 0.8
1.6 1.6
Well
Fig. 9-7-Dip extrapolation: left part of section and right part of Geogram survey were put together and vice versa
Fig. 9-8-A VSP trace contains upgoing and downgoing waves. Multiples can clearly be seen on the display.
Downgoing Multiple
w Direct Wave , Time .
_-__--_-----_----------
2--------------w-
Geophone Position 1
_-__--_-----_----------
--------------w-
__-___-___-_-----------
_--__-_____-___-------
______--------__------
9-7
8. CASEDHOLE LOG INTlZPRETATlON PRINCIPLES/APPLICATIONS
(downgoing) and the signals arriving from below the tool
(upgoing). The downgoing signalsare the direct (first) ar-
rivals andthedowngoingmultiples. Theupgoingsignalscon-
sist of the direct reflections and the upgoing multiples.
Advantages of the vertical seismic profile technique
include:
l recording a real seismictrace in the borehole rather than
relying on a synthetically generatedseismogram
l measuringthe spectralcontentof the downgoing seismic
signal as a function of depth
l establishmentof a precise link betweenthe surfaceseis-
mic results and well logs, since the VSP is a high-
resolution measurement
l the recording of signalswith animproved high-frequency
content,sincetheycrossthehighly absorptivelow-velocity
layers near the surface only once
l improved seismic resolution of subtle stratigraphic fea-
tures around the well, such as faults or pinchouts
l therecordingof deepreflector signalsthatarenotreceived
at surface; this is particularly useful in structurally com-
plex areas
l an excellent record of the band-limited reflection coeffi-
cient seriesthrough deconvolution of the VSP.
‘--yi%$YI Oow”go,“gupgoing
Fig. O-O-Processing of VSP’s involves three major steps:
data editing for optimized shot quality, upgoing and down-
going wavetrain separation, and deconvolution.
1
VSP PROCESSING
TheVSP processingsequence(Fig. 9-9) usually includes
mostof the following steps:
mshotselectionby ananalystto reject the noisy, poor-
quality shots
l consistencycheck of the surface hydrophone signal
mmedian stacking of shots
l checkof coherencebetweena referencelevel andall
others
B monitoring of phaseshifts andacousticimpedanceat
all levels
l bandpassfiltering to eliminate noise and remove
aliasedfrequencies
l filtering to help eliminate tube waves
l true amplitude recovery by atime-variant function to
compensatefor spherical spreading
l velocity filtering to separatethe upgoing and down-
going componentsof the total wavefield
l autocorrelationof the downgoing waveafter filtering
for selectionof the proper deconvolution parameters
using the downgoing wave field as a deterministic
model
l predictive deconvolution to removesourcesignature
effects and to improve resolution
l time-variantfiltering to matchthesurfaceseismicdata
l corridor stacking: summing all the upgoing waves
recorded in a window following the first break.
A vertical seismicprofile display using datafrom the
Downhole SeismicArray tool is shownin Fig. 9-10. The
corridor stackfrom this presentationis shown superim-
posedon the surface seismic section in Fig. 9-11.
OFFSET VERTICAL SEISMIC PROFILE
A normal VSP survey in a vertical boreholewith horizontal
bedding gives very limited lateral information. However,
with dipping reflectors, a normal VSP survey can provide
someinformation on the updip features (Fig. 9-12).
An offset VSP (Fig. 9-13), however, offers the possibili-
ty of large lateral coverage.Lateral coverageof up to one-
half of thesourceoffsetdistancecanbeachievedin thedirec-
tion of the source.Profiling of a feature canbedoneby us-
ing afixed offsetsourcepositionsomedistancefrom thewell
and moving the geophone(s)in the well, or by having the
geophone(s)fixed and moving the source.
WALKAWAY SURVEYS
A walkaway survey provides a 2-dimensional seismicpic-
ture of the formations on either sideandbelow a well. This
9-8
9. CASEDHOLE SEISMIC
TEXAS GULF COAST EXAMPLE
ZERO PHASE PROCESSING - - NORMAL POLARITY
Fig. QlO-VSP using DSA tool
Fig. 9-I 1-VSP corridor stack from Fig. 9-10 superimposed
on surface seismic section
9-9
10. CASED HOLE LOG INTERPRETATION PRlNClPLESlAPPLlCATlONS
by aboatwith theenergysource,moving ataconstantspeed
anddirection alonga 3 km line that passescloseto the well.
Seismic shotswould be generatedwith an air gun at 30 m
intervalsalongthis line andadownholegeophonewould mo-
nitor the arrivals. Eachpassof the boatwould generate100
seismic wave traces at each geophoneposition. Accurate
navigation fixes are obtained for each shot position along
the survey line by placing navigation equipmentonboth the
rig andboat. The seismicwavepatterncreatedby this multi-
source/singlereceiver arrangementis particularly useful in
investigating complex formations.
The following illustrations show the family of borehole
seismicsurveysandthe developmentof awalkaway survey.
The first illustration (Fig. 9-14) showstheresultsof acheck-
shotsurvey. The impedancelog (sonic x density) hasbeen
correctedwith thecheckshottimestomatchtheseismictimes
and a Geogramdisplay computedfrom the data. Both logs
are superimposedon the surface seismic section to allow
correlation of the log datawith the surface seismicevents.
Figure 9-15 illustrates a ZVSP. In the ZVSP survey, the
eventsbeyondthecheckshot’sfirst arrivals arerecordedand
interpreted, providing a time and depth record of upgoing
reflected events. To obtain quality reflected data, a higher
density of receiver positions is usedthan in the check-shot
survey. A corridor stackof the VSP datais shownsuperim-
posedon the surfaceseismicsectionto allow correlation of
depth and time.
Fig. 412-VSP: stationary source, moving receiver
is achievedby using surveytechniquesdevelopedfrom Zero
Offset VSP (ZVSP) and Offset VSPs (OVSP). Walkaway
surveysare unique, however, in that they always employ a
multiple sourceand single receiver arrangement.
A typical offshore walkaway survey would becarried out
Fig. 9-l 3-Offset VSP: moving source, stationary receiver
11. CASED HOLE SEISMIC
1500 1000 500 A 500 1000 1500 m A
Fig. Q-14-An impedance log and Geogram log are shown superimposed on the surface seismic section
1500 1000 500 , 500 1000 1500 m A
Hg. y-15--c;orrluor stack of the VSP is superimposed on the surface seismic section to allOW correla-
tion of depth and time
The samedata from the previous acquisition has been The OVSP is illustrated in display (a) of Fig. 9-17. In this
processedwith 2-dimensionalmodel datato extendthe off- case,the sourceis substantially offset from the well. This
setposition of reflection points on thedipping horizons(Fig. shifts thereflection points away from the well andproduces
9-16). coverage of an extended area around the well. This is
9-11
12. CASED HOLE LOG INTERPRETATION PRINCIPLES/APPLICATIONS
1500 1000 500 P 500 1000 1500 m
Fig. 416-Same data as Fig. 9-15, processed with 2-dimensional model data to extend the offset
position of reflection points on the dipping horizons
500 1000 1500 500 1000 1500 m,
Fig. 417-The (a) display shows the Offset VSP events superimposed on the surface seismic section. The (b) display shows
the combined results of the OVSP and modeled VSP data.
particularly useful for detectionof faults andformation pin-
chouts. The OVSP eventsare shown superimposedon the
appropriatepart of the surfaceseismicdata.The display (b)
showsthe combinedresultsof the OVSP andmodeledVSP
data.
Note that there is no reflector coveragebelow total depth
of the well. A particular attraction of walkaway surveys is
thatthey provide bettercontinuity andmore completecover-
age, especially below the bottom of the well.
9-12
13. CASED HOLE SEISMIC
The use of the Downhole Seismic Array tool to acquire
thedatacansignificantly reducethe acquisitiontime andim-
provetheconsistencyof theseismicsignalfrom levelto level
in the well. Figure 9-18 showsa schematicof theoperation-
al setupfor a walkaway VSP job on land. Two vibrators,
in radiocontactwith theloggingunit, wereusedastheenergy
source. The shotpoints were located at 75 m intervals and
were movedout 3 km from the well in eachof the four or-
thogonaldirections. At eachshotposition, eight levelswere
recorded with the DSA tool.
The east-westwalkaway VSP resultsareshownon theleft
in Fig. 9-19. Faults, nearby andintersectingthe well, were
determinedfrom this seismicsection.The north-southwalka-
way section is shown on the right.
DSA TOOL FOR VSP ACQUISITION
The Downhole SeismicArray tool, with its eight single-axis
geophonearray configuration, provides severaladvantages
over single level tools for VSP acquisition in casedholes:
l time savings.Oneobviousadvantageis the savingsin time
sinceeight levels are recordedat eachfiring of the ener-
gy source.
Fig. 9-18-Schematic of operational setup for a walkaway
VSP job on land
West Offset (ft) East North Offset (ft) South
1000 750 500 250 We”
250 500 250 250 500._ .-_- -_, ----
Fig. 9-19-The east-west walkaway VSP results are shown on the left, and the north-south results on the right.
14. CASED HOLE LOG INTERPRETATION PRINCIPLES/APPLICATIONS
reduction in tube-wave effects. The DSA tool provides
someadvantagesin areaswhere strong tube-wavesmay
contaminate the waveform data. The strong clamping
force, the small cross-sectionalarea, andthe streamlined
shapeof theshuttlehelpto reducetheeffectof tube-waves
on the seismic data.
reduction of navigation errors in walkaway VSP opera-
tions. In offshoremultioffsetoperations,theseismicsource
is movedby aboat ata constantspeed.The DSA tool ac-
quires signalsfrom eight levels while the boat is making
asinglepath,reducingnavigationalerrorsoversinglelevel
tools.
reduction of effectsof sourcesignaturechanges.The ef-
fects of source signature changesdue to suchthings as
changesin gunpressure,gun pit alteration, or tide levels,
arereducedbecausetheeightshuttlesreceivesignalswhich
originate from the sameshot.
accuratetransit times betweenlevels. Sincethe DSA ge-
ophonesareequally spacedon acable, potential distance
errors are eliminated.
PRIMARY USES OF THE VSP SURVEY
Theenhancedresolutionof theVSP makesit possibleto veri-
fy or deny the presenceof reflections that are indistinct or
doubtful on seismicsectionsnearthe well. The VSP is par-
ticularly well suitedto determinetheconditions existing be-
low the well’s total depth. Overpressuredzones,gassands,
and deep reflectors can be verified or recognized.
Since the downgoing wavefield is recorded, multiple
reflections canbe identified andremoved. The samedown-
going waveinformation canbeusedto reprocesssurfaceseis-
mic profiles traversing the vicinity of the well.
Perhapsthe most common usefor the VSP is a link be-
tween reflections observedon a surfaceseismicprofile and
specific petrophysical properties measuredin the borehole.
The correlation role of the VSP is important for reservoir
developmentapplications.
Finally, by positioningthe seismicsourceasignificantdis-
tancefrom thewell, structuralandstratigraphicfeaturesfrom
hundredsto thousandsof feet from the well canbedelineat-
ed and verified againstthe surface seismic.
PROXIMITY SURVEY INTERPRETATION
Proximity surveyshavebeenusedfor many yearsto define
the shapeof salt domes.Now a program is available to en-
tirely mechanizethe interpretation process.After awell has
beendrilled on the flank of a salt dome, a downhole sensor
is lowered into the hole and anchoredat numerousdepths.
An energy sourceis positioned directly over the top of the
structure. A travel time is measuredfrom the sourceto each
of thedownhole sensorlocations. From prior knowledgeof
salt velocities, velocities of formations encounteredin the
well, and at least one salt tie point, distancesfrom salt to
sensorpositions canbecalculated, andthe shapeof the salt
flank determined.
Given the layer velocities andthe sourceandreceiver lo-
cations, the transit times to eachreceiver are measuredby
ray tracing. Next, an initial model is generatedon the com-
putercontainingtheknown sourceandreceiverlocationsand
the layer velocities. The program then calculates, for each
source-receiverpair, all the possibletravel pathsthe acous-
tic energy could havetaken with the total time equalto the
measuredtime. A line through all therefraction points con-
tainsall thepossiblelocationsfor the salt interfacecalculat-
ed from one receiver. The resulting oval is called an apla-
natic surface(Gardner, 1949).Thecomputationcanbeper-
formed for combinations of sourceand receiver, and will
result in a seriesof aplanaticsurfaces.The bestfitting line,
tangentto all the ovals, is the final solution for the location
of the interface.
The techniqueis illustrated in a well in the Gulf of Mexi-
co. Using accurate source-receiver travel times and the
source-receiverpositions, the initial model was generated.
The saltwasaknown distancefrom onereceiver,which ena-
bled theuseof the refraction oval techniquefor the determi-
nation of the salt top. The formation velocities adjacentto
the salt were determinedfrom a vertical check shotandthe
aplanatic surfaceswere generated,as shown in Fig. 9-20.
The salt flank was interpreted asthe common tangentline
illustrated in Fig. 9-21.
The mechanizedproximity interpretationgivesresultscon-
sistent with the interpretation madewith wavefront charts,
but is much less time consuming.
REFERENCES
Anstey, N.A.: SeismicInterpretation: l7zePhysicalAspects,IHRDC, Boston
(1977).
Ausbum, B.E.: “Well Log Editing in Supportof DetailedSeismicStudies,”
Trans., 1977 SPWLA Annual Logging Symposium.
Gardner,L.W.: “SeismographDeterminationof SaltDomeBoundaryDeep
on the Dome Flank,” Geophysics(1949) 46, 268-287.
Goetz, J.F., Dupal, L., and Bowler, J.: An Investigation Into Discrepan-
ciesBetweenSonicLog and SeismicCheck-ShotVelocities, Schlumberger
Technical Services(1977).
Landgren,K.M. andDeri, C.P.:A MechanizedProcessfor Proximity Suwey
Interpretation, SchlumbergerOffshore Services(1986).
McCollum, B. and LaRue, W.W.: “Utilization of Existing Wells in Seis-
mograph Work,” Bull., AAPG (1931) 15, 1409-1417.
Miller, D.E.: “Arrival Times and Envelopes- Inverse Modeling for Sub-
surfaceSeismics,” 53rd Annual International SEG Meeting, Sept., 1983,
Las Vegas, ExpandedAbstracts, 449-467.
Mons, F. andBabour,K.: Vertical SeismicProfiling, SAID QuatriemeCol-
loque Annuel de Diagraphies (Oct., 1981).
Musgrave,A.W., Wooley, WC, andGray, H.: “Outlining of SaltMass-
es by Refraction Methods,” Geophysics(1960) 25, 141-167.
9-14
15. CASED HOLE SEISMIC
m
v = 14,900 ftlsec
v =1Ez:
Gv = 7700
Lv=E
L-
ftlsec
/j - g600ftlsec
Fig. O-PO-Proximity Survey interpretation: refraction ovals Fig. 9-21-Proximity Survey interpretation: final solution
Robinson,E.A. andTreitel, S.: GeophysicalSignalAnalysis, Prentice-Hall
Inc., New Jersey(1980).
Schlmberger Middle East WellEvaluation Review “Borehole Seismics“,
Schlumberger Technical Services, Paris (Autumn 1988).
Schlmberger WestAjica WellEvaluation Conference,SchlumbergerTech-
nical Services, Paris (1983).
9-15