scholarly journals Assessing the repeatability of reflection seismic data in the presence of complex near-surface conditions CO2CRC Otway Project, Victoria, Australia

2009 ◽  
Vol 2009 (1) ◽  
pp. 1
Author(s):  
Y. Al Jabri ◽  
M. Urposevic ◽  
A. Kepic ◽  
B. Evans
Keyword(s):  
Seismic Data ◽  
Near Surface ◽  
Surface Conditions ◽  
Reflection Seismic

Multidisciplinary study of the hanging wall of the Kiirunavaara iron ore deposit, northern Sweden

Geophysics ◽  
2012 ◽  
Vol 77 (6) ◽  
pp. B269-B285 ◽  
Author(s):  
Mai-Britt Jensen ◽  
Artem Kashubin ◽  
Christopher Juhlin ◽  
Sten-Åke Elming
Keyword(s):  
Seismic Data ◽  
Hanging Wall ◽  
Low Velocity ◽  
Contact Zones ◽  
Near Surface ◽  
Reflection Seismic ◽  
Imaging Results ◽  
Fracture Development ◽  
Weakness Zones ◽  
The Town

Potential weakness zones due to mining-related fracture development under the town of Kiruna, Sweden, have been investigated by integration of seismic, gravity, and petrophysical data. Reflection seismic data were acquired along two subparallel 2D profiles within the residential area of the town. The profiles of [Formula: see text], each oriented approximately east–west, nearly perpendicular to the general strike of the local geology, crossed several contact zones between quartz-bearing porphyries, a sequence of interchanging sedimentary rocks (siltstone, sandstone, conglomerate, and agglomerate), and metabasalt. The resulting reflection seismic sections revealed a strong east-dipping reflectivity that is imaged down to approximately 1.5 km. The location and orientation of major features agree well between the profiles and with the surface geology and known contact zones between the different rock types. Our imaging results, supported by traveltime modelling, indicate that the contact zones dip 40°–50° to the east. The deepest and the weakest reflections are associated with a [Formula: see text] dipping structure that is presumably related to the Kiirunavaara iron mineralization. Tomographic inversion of refracted arrivals revealed a more detailed image of the velocity distribution in the upper 100–200 m along the profiles, enabling us to identify near-surface low velocity zones. These could be possible weakness zones developed along the lithological contacts and within the geologic units. The structural image obtained from the seismic data was used to constrain data inversion along a 28 km long east–northeast to west–southwest-oriented gravity profile. The resulting density model indicates that the quartz-bearing porphyry in the hanging wall of the Kiirunavaara mineralization can be separated into two blocks oriented parallel to the ore body. One block has an unexpected low density, which could be an indication of extensive fracturing and deformation.

The SEAM Barrett model: strengths and weaknesses

Geophysics ◽  
2021 ◽  
pp. 1-31
Author(s):  
Heloise Lynn ◽  
Colin M. Sayers ◽  
Benjamin Roure
Keyword(s):  
Seismic Data ◽  
Fractured Reservoirs ◽  
Unconventional Reservoirs ◽  
Velocity Variation ◽  
Permian Basin ◽  
Amplitude Variation ◽  
Near Surface ◽  
Reflection Seismic ◽  
The North ◽  
Shale Reservoirs

The SEAM Barrett model was designed to model typical land basins found in the North American mid-continent that host unconventional reservoirs, such as fractured shale reservoirs. This model was used recently in several studies to assess whether shale bodies could be resolved using azimuthal 3D P-P reflection seismic data. In one study it was claimed that near-surface complexity prevents the identification of the shale bodies using azimuthal analysis and concluded that VVAz (Velocity Variation with Azimuth) and AVAz (Amplitude Variation with Azimuth) are not worth running in the Permian basin. However, another study by different authors applied a different seismic processing sequence to successfully resolve the reservoir geobodies and showed promising AVAz and VVAz results. This paper focuses on the SEAM Barrett model itself. Despite some advantages, the limitations of the Barrett model prevent conclusions to be drawn about the usefulness of VVAz and AVAz to characterize fractured reservoirs in other situations, such as the Permian Basin.

scholarly journals Near-surface structure of the Sodankylä area in Finland, obtained by passive seismic interferometry

Solid Earth ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 1563-1579
Author(s):  
Nikita Afonin ◽  
Elena Kozlovskaya ◽  
Suvi Heinonen ◽  
Stefan Buske
Keyword(s):  
Seismic Data ◽  
Seismic Interferometry ◽  
Near Surface ◽  
Reflection Seismic ◽  
Velocity Models ◽  
Registration Period ◽  
Empirical Green Function ◽  
Geological Conditions ◽  
Passive Seismic ◽  
Passive Data

Abstract. Controlled-source seismic exploration surveys are not always possible in nature-protected areas. As an alternative, the application of passive seismic techniques in such areas can be proposed. In our study, we show results of passive seismic interferometry application for mapping the uppermost crust in the area of active mineral exploration in northern Finland. We utilize continuous seismic data acquired by the Sercel Unite wireless multichannel recording system along several profiles during XSoDEx (eXperiment of SOdankylä Deep Exploration) multidisciplinary geophysical project. The objective of XSoDEx was to obtain a structural image of the upper crust in the Sodankylä area of northern Finland in order to achieve a better understanding of the mineral system at depth. The key experiment of the project was a high-resolution seismic reflection experiment. In addition, continuous passive seismic data were acquired in parallel with reflection seismic data acquisition. Due to this, the length of passive data suitable for noise cross-correlation was limited from several hours to a couple of days. Analysis of the passive data demonstrated that dominating sources of ambient noise are non-stationary and have different origins across the XSoDEx study area. As the long data registration period and isotropic azimuthal distribution of noise sources are two major conditions for empirical Green function (EGF) extraction under the diffuse field approximation assumption, it was not possible to apply the conventional techniques of passive seismic interferometry. To find the way to obtain EGFs, we used numerical modelling in order to investigate properties of seismic noise originating from sources with different characteristics and propagating inside synthetic heterogeneous Earth models representing real geological conditions in the XSoDEx study area. The modelling demonstrated that scattering of ballistic waves on irregular shape heterogeneities, such as massive sulfides or mafic intrusions, could produce a diffused wavefield composed mainly of scattered surface waves. In our study, we show that this scattered wavefield can be used to retrieve reliable EGFs from short-term and non-stationary data using special techniques. One of the possible solutions is application of “signal-to-noise ratio stacking” (SNRS). The EGFs calculated for the XSoDEx profiles were inverted, in order to obtain S-wave velocity models down to the depth of 300 m. The obtained velocity models agree well with geological data and complement the results of reflection seismic data interpretation.

scholarly journals Local CMP stacking improvement technique for better traceability of separate reflection horizon

2021 ◽  
Author(s):  
А.А. Дробинский ◽  
О.А. Жуковская
Keyword(s):  
Software Development ◽  
Seismic Data ◽  
Model Building ◽  
Synthetic Data ◽  
Signal Amplitude ◽  
Fine Tuning ◽  
Near Surface ◽  
Reflection Seismic ◽  
Geological Situation ◽  
High Flexibility

В последние годы всё больше объектов сейсморазведочных работ относится к проблемным территориям, характеризующимся неблагоприятными поверхностными условиями и сложной геологической обстановкой. Получение качественных сейсмических изображений при обработке в таких случаях входит в число приоритетных направлений современной сейсморазведки. Одним из путей решения проблем ухудшения прослеживаемости сейсмических горизонтов в сложных условиях является оптимизированное суммирование общей средней точки (ОСТ), учитывающее качество входных сейсмических данных. Цель исследования. Настоящая работа посвящена созданию и тестированию гибкой, универсальной методики оптимизации суммирования ОСТ на конечной стадии полевой или камеральной обработки сейсмических данных метода отражённых волн общей глубинной точки (МОВ-ОГТ 2D/3D) для улучшения прослеживаемости отражающих горизонтов. При создании такой методики важным требованием являлась возможность реализации в существующем программном обеспечении (ПО), в том числе, отечественном. Методы исследования. Для исследования влияния сложных геологических объектов на распределение энергии в выборках ОСТ было выполнено построение иллюминационной модели по целевому горизонту, расположенному под эрозионным врезом. Оценка влияния рассеивающих аномалий верхней части разреза (ВЧР) проводилась с помощью двумерного лучевого моделирования с получение синтетических сейсмограмм ОПВ по горизонтально-слоистому модельному разрезу, содержащему участок палеокарста. Чтобы оценить потенциал применения предлагаемой методики были генерированы синтетические данные, содержащие сильные помехи различной природы, а также зону падения амплитуды полезного сигнала. По этим данным были разными способами получены и оценены суммарные трассы. Предлагаемая методика также была опробована на реальных данных метода общей глубинной точки (МОГТ-2D). Оценка результатов работы различных вариантов суммирования выполнялась визуально, а также количественно (с помощью атрибутного анализа). Результаты работы. Выполненное исследование показало недостаточную эффективность стандартного суммирования ОСТ для сложных сейсмических данных. Польза от применения существующих методик улучшения суммирования ОСТ очевидна, но они имеют недостатки: нарушение естественной динамики волновой картины, невозможность локального применения, необходимость реализации в специальном ПО. Предлагаемая авторами методика оптимизации суммирования даёт высокую гибкость и маневренность работы и позволяет справиться с вышеуказанными проблемами. Свободный выбор критериев взвешивания интервалов трасс на основе анализа пользовательского набора атрибутов открывает широкие возможности тонкой настройки процедуры, вводит интерпретационную составляющую в процесс оптимизации суммирования, делая его более осмысленным в геолого-геофизическом отношении. Предлагаемая методика не требует написания и опробования нового специального ПО и может быть реализована в уже имеющихся сейсмических пакетах, включая и российские программные комплексы Today increasingly more objects of prospecting seismology belong to problem areas characterized by unfavorable surface conditions and complex geological situation. Acquiring of high-quality seismic images by processing in these cases is a part of priority directions of modern prospecting seismology. One of the way to overcome the problem of seismic horizon traceability worsening in hard conditions is optimized CMP stacking, considering the quality of input seismic data. Aim. This work is devoted to generation and examination of flexible universal technique of optimized stacking on the last stage of field or final processing of 2D/3D reflection seismic data for seismic horizon traceability improvement. Creating this technique assumed important condition of embodiment ability in existing software (including Russian). Methods. Illumination model building was performed for target horizon, located beneath the erosive cut for studying of complex geological objects influence on energy distribution in CMP gathers. Scattering superficial anomalies influence was estimated by means of 2D ray tracing and synthetic shot records generation on horizontally layered model sectionconsisting near surface ancient karst spot. Synthetic data with different kinds of noise and signal amplitude decay zone war generated to appreciate implementation potential of introducing technique. Stacked traces were obtained and evaluated on this data with different methods. The introduced technique was tested on real 2D seismic data too. Evaluation of results of different kinds of stacking was performed by sight and with quantitative (attribute) analysis. Results. Performed research showed insufficient efficiency convenience CMP stacking for complex seismic data. The advantages of existing CMP stacking improvement methods are obvious but there are drawbacks too: natural wave field dynamic violation, disability of local implementation, need of special software development. Offered technique of stacking optimization gives high flexibility and mobility in work and allow overcoming the aforementioned problems. Easy choice of trace range weighting criteria based on customer attribute set analysis gives wide opportunities of fine-tuning for this procedure, bringing in interpretation term of stack optimization process and making it more sensible in geological-geophysical relation. This technique need not new software development and testing, it could be embodied in existing seismic software suites, including Russian complexes

Comparison of geophone and surface-deployed distributed acoustic sensing seismic data

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. A25-A29 ◽  
Author(s):  
Kyle T. Spikes ◽  
Nicola Tisato ◽  
Thomas E. Hess ◽  
John W. Holt
Keyword(s):  
Seismic Data ◽  
Fiber Optic ◽  
Single Strand ◽  
Near Surface ◽  
Acoustic Sensing ◽  
Surface Reflection ◽  
Reflection Seismic ◽  
Geophysical Surveys ◽  
Distributed Acoustic Sensing ◽  
High Level

The rapid and nonintrusive deployment of seismic sensors for near-surface geophysical surveys is of interest to make data acquisition efficient and to operate in a wide variety of environmental and surface-terrain conditions. We have developed and compared near-surface data acquired using a traditional vertical geophone array with data acquired using three different fiber optic cables operating in a distributed acoustic sensing (DAS) configuration. The DAS cables included a helically wrapped fiber, a nearly bare single-strand fiber, and an armored single-strand fiber. These three cables are draped on the ground alongside the geophones. Equivalent processing on colocated shot gathers resulted in a high level of similarity, in particular for reflection energy acquired through geophones and the helically wrapped cable. The single-strand fibers indicate much less similarity. Frequency content, however, differs in the raw and processed gathers from the geophones and the fiber optic cables. Nonetheless, results demonstrate that DAS technology can be used successfully to acquire near-surface reflection seismic data by deploying the cables on the surface. Potential applications for this technology include rapid deployment of active and/or passive arrays for near-surface geophysical characterization for various applications at different scales.

Sign in / Sign up

Export Citation Format

Share Document