scholarly journals 3D reflection seismic imaging of the iron-oxide deposits in the Ludvika mining area (Sweden) using a focusing pre-stack depth migration approach

2021 ◽  
Author(s):  
Felix Hloušek ◽  
Michal Malinowski ◽  
Lena Bräunig ◽  
Stefan Buske ◽  
Alireza Malehmir ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Seismic Imaging ◽  
Mine Planning ◽  
Seismic Exploration ◽  
Depth Imaging ◽  
Mining Site ◽  
Depth Migration ◽  
Reflection Seismic ◽  
Imaging Results

Abstract. We present the pre-stack depth imaging results for a case study of 3D reflection seismic exploration at the Blötberget iron-oxide mining site belonging to the Bergslagen mineral district in central Sweden. The goal of this case study is to directly image the ore-bearing units and to map its possible extension down to greater depths than known from existing boreholes. Therefore, we applied a tailored pre-processing workflow as well as two different seismic imaging approaches, Kirchhoff pre-stack depth migration and Fresnel Volume Migration (FVM). Both imaging techniques deliver a well resolved 3D image of the deposit and its host rock, where the FVM image yields a significantly better image quality compared to the KPSDM image. We were able to unravel distinct reflection horizons, which are linked to known mineralisation and provide insights on lateral and depth extent of the deposits beyond their known extension from borehole data. A comparison of the known mineralization and the image show a good agreement of the position and the shape of the imaged reflectors caused by the mineralization. Furthermore, the images show a reflector, which is interpreted to be a fault intersecting the mineralisation and which can be linked to the surface geology. The depth imaging results can serve as the basis for further investigations, drillings and follow-up mine planning at the Blötberget mining site.

Deep reflection seismic imaging of iron‐oxide deposits in the Ludvika mining area of central Sweden

2019 ◽  
Vol 68 (1) ◽  
pp. 7-23 ◽  
Author(s):  
Magdalena Markovic ◽  
Georgiana Maries ◽  
Alireza Malehmir ◽  
Julius Ketelhodt ◽  
Emma Bäckström ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Seismic Imaging ◽  
Mining Area ◽  
Reflection Seismic

Seismic imaging and velocity analysis for an Alberta Foothills seismic survey

Geophysics ◽  
2001 ◽  
Vol 66 (3) ◽  
pp. 721-732 ◽  
Author(s):  
Lanlan Yan ◽  
Larry R. Lines
Keyword(s):  
Seismic Imaging ◽  
Migration Velocity ◽  
Surface Velocity ◽  
Seismic Survey ◽  
Velocity Analysis ◽  
Prestack Depth Migration ◽  
Near Surface ◽  
Depth Migration ◽  
Migration Velocity Analysis ◽  
Imaging Results

Seismic imaging of complex structures from the western Canadian Foothills can be achieved by applying the closely coupled processes of velocity analysis and depth migration. For the purposes of defining these structures in the Shaw Basing area of western Alberta, we performed a series of tests on both synthetic and real data to find optimum imaging procedures for handling large topographic relief, near‐surface velocity variations, and the complex structural geology of steeply dipping formations. To better understand the seismic processing problems, we constructed a typical foothills geological model that included thrust faults and duplex structures, computed the model responses, and then compared the performance of different migration algorithms, including the explicit finite difference (f-x) and Kirchhoff integral methods. When the correct velocity was used in the migration tests, the f-x method was the most effective in migration from topography. In cases where the velocity model was not assumed known, we determined a macrovelocity model by performing migration/velocity analysis by using smiles and frowns in common image gathers and by using depth‐focusing analysis. In applying depth imaging to the seismic survey from the Shaw Basing area, we found that imaging problems were caused partly by near‐surface velocity problems, which were not anticipated in the modeling study. Several comparisons of different migration approaches for these data indicated that prestack depth migration from topography provided the best imaging results when near‐surface velocity information was incorporated. Through iterative and interpretive migration/velocity analysis, we built a macrovelocity model for the final prestack depth migration.

Novel strategies for complex foothills seismic imaging — Part 1: Mega-near-surface velocity estimation

2020 ◽  
Vol 8 (3) ◽  
pp. T651-T665
Author(s):  
Yalin Li ◽  
Xianhuai Zhu ◽  
Gengxin Peng ◽  
Liansheng Liu ◽  
Wensheng Duan
Keyword(s):  
Seismic Imaging ◽  
Velocity Model ◽  
Velocity Estimation ◽  
Innovative Approach ◽  
Surface Velocity ◽  
Near Surface ◽  
Depth Migration ◽  
Static Corrections ◽  
Over Time

Seismic imaging in foothills areas is challenging because of the complexity of the near-surface and subsurface structures. Single seismic surveys often are not adequate in a foothill-exploration area, and multiple phases with different acquisition designs within the same block are required over time to get desired sampling in space and azimuths for optimizing noise attenuation, velocity estimation, and migration. This is partly because of economic concerns, and it is partly because technology is progressing over time, creating the need for unified criteria in processing workflows and parameters at different blocks in a study area. Each block is defined as a function of not only location but also the acquisition and processing phase. An innovative idea for complex foothills seismic imaging is presented to solve a matrix of blocks and tasks. For each task, such as near-surface velocity estimation and static corrections, signal processing, prestack time migration, velocity-model building, and prestack depth migration, one or two best service companies are selected to work on all blocks. We have implemented streamlined processing efficiently so that Task-1 to Task-n progressed with good coordination. Application of this innovative approach to a mega-project containing 16 3D surveys covering more than [Formula: see text] in the Kelasu foothills, northwestern China, has demonstrated that this innovative approach is a current best practice in complex foothills imaging. To date, this is the largest foothills imaging project in the world. The case study in Kelasu successfully has delivered near-surface velocity models using first arrivals picked up to 3500 m offset for static corrections and 9000 m offset for prestack depth migration from topography. Most importantly, the present megaproject is a merge of several 3D surveys, with the merge performed in a coordinated, systematic fashion in contrast to most land megaprojects. The benefits of this approach and the strategies used in processing data from the various subsurveys are significant. The main achievement from the case study is that the depth images, after the application of the near-surface velocity model estimated from the megasurveys, are more continuous and geologically plausible, leading to more accurate seismic interpretation.

A case study for azimuthally anisotropic prestack depth imaging of an onshore Alaska prospect

Geophysics ◽  
2010 ◽  
Vol 75 (4) ◽  
pp. B177-B186 ◽  
Author(s):  
Jinming Zhu ◽  
John Mathewson ◽  
Gail Liebelt
Keyword(s):  
Model Building ◽  
Velocity Model ◽  
Image Point ◽  
Depth Imaging ◽  
Depth Migration ◽  
Isotropic Media ◽  
Well Data ◽  
Reflection Tomography ◽  
Very High

In a study of the Sterling-Triangle area of Alaska, U.S.A., we initiated prestack depth migration (PSDM) to improve imaging on a prospect initially identified on a prestack time-migrated (PSTM) volume. Under the isotropic media assumption, the first few iterations of the reflection tomography had difficulty in converging to the proper velocity model. Upon further investigation, a very-high-velocity conglomerate layer was identified in the middle of the section across the whole survey area. We adopted the salt-flood practice, routine in depth-imaging salt provinces such as the Gulf of Mexico. The strategy was to focus on the shallow section above the conglomerate first, followed by a constant-velocity flood for picking the conglomerate base. The finalisotropic PSDM result showed that significant residual moveout differences existed on gathers along different azimuths. The net anisotropic effect on the isotropic PSDM was a degraded final PSDM volume. In the subsequent anisotropic PSDM work, azimuthally variant horizontal velocities were allowed in the model building. Common-image-point (CIP) gathers were created along different azimuths using sectored input gathers. Residuals picked on the sectored CIP gathers were used in joint tomography to invert different horizontal velocities. Incorporating significant well information, we built an anisotropic velocity model such that the azimuthal moveout on the butterfly gathers was essentially flat. The resulting anisotropic PSDM was consistent with well data and could be interpreted with much higher confidence.

scholarly journals Sparse 3D reflection seismic survey for deep-targeting iron oxide deposits and their host rocks, Ludvika Mines, Sweden

Solid Earth ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 483-502
Author(s):  
Alireza Malehmir ◽  
Magdalena Markovic ◽  
Paul Marsden ◽  
Alba Gil ◽  
Stefan Buske ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Collaborative Work ◽  
Mine Planning ◽  
Seismic Survey ◽  
Quality Data ◽  
Normal Faults ◽  
3D Seismic ◽  
Near Surface ◽  
Reflection Seismic ◽  
Static Corrections

Abstract. Many metallic mineral deposits have sufficient physical property contrasts, particularly density, to be detectable using seismic methods. These deposits are sometimes significant for our society and economic growth and can help to accelerate the energy transition towards decarbonization. However, their exploration at depth requires high-resolution and sensitive methods. Following a series of 2D seismic trials, a sparse, narrow source–receiver azimuth, 3D seismic survey was conducted in the Blötberget mine, in central Sweden, covering an area of approximately 6 km2 for deep-targeting iron oxide deposits and their host rock structures. The survey benefited from a collaborative work by putting together 1266 seismic recorders and a 32 t vibrator, generating 1056 shot points in a fixed geometry setup. Shots were fired at every 10 m where possible, and receivers were placed at every 10–20 m. Notable quality data were acquired despite the area being dominated by swampy places as well as by built-up roads and historical tailings. The data processing had to overcome these challenges for the static corrections and strong surface waves in particular. A tailored for hardrock setting and processing workflow was developed for handling such a dataset, where the use of mixed 2D and 3D refraction static corrections was relevant. The resulting seismic volume is rich in terms of reflectivity, with clear southeast-dipping reflections originating from the iron oxide deposits extending vertically and laterally at least 300 m beyond what was known from available boreholes. As a result, we estimate potential additional resources from the 3D reflection seismic experiment on the order of 10 Mt to be worth drilling for detailed assessments. The mineralization is crosscut by at least two major sets of northwest-dipping reflections interpreted to dominantly be normal faults and to be responsible for much of the lowland in the Blötberget area. Moreover, these post-mineralization faults likely control the current 3D geometry of the deposits. Curved and submerged reflections interpreted from folds or later intrusions are also observed, showing the geological complexity of the study area. The seismic survey also delineates the near-surface expression of a historical tailing as a by-product of refraction static corrections, demonstrating why 3D seismic data are so valuable for both mineral exploration and mine planning applications.

scholarly journals A Mineralogical Museum as a Geotourism Attraction: A Case Study

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 582
Author(s):  
Magner Turner-Carrión ◽  
Paúl Carrión-Mero ◽  
Israel Turner-Salamea ◽  
Fernando Morante-Carballo ◽  
Maribel Aguilar-Aguilar ◽  
...  
Keyword(s):  
Qualitative Evaluation ◽  
Geological Heritage ◽  
Assessment Model ◽  
Heritage Conservation ◽  
Ex Situ ◽  
Mining District ◽  
Mining Site ◽  
Semiquantitative Evaluation ◽  
Additional Value

The Zaruma-Portovelo mining district in Ecuador, and in particular, Portovelo City, is home to the oldest mining museum in the country. This museum, named Museo Mineralógico Magner Turner (MMMT in Spanish), is a centre that reflects, through its collections, the history and culture of this territory. This work aimed to evaluate the MMMT as a possible geosite by analysing its contributions to the geomining heritage of the Zaruma-Portovelo district, and thus, to enhance it and promote its collections as a geotouristic attraction. The work involved three phases: (i) describing the museum and its surroundings; (ii) a semiquantitative evaluation of the museum using the Brilha method and a geosites assessment model (GAM); and (iii) a qualitative evaluation using the Delphi and SWOT methodologies to define strategies and proposals for museum development. The results obtained by the semiquantitative evaluation of the geosite with the Brilha method reflect high scientific (330/400), educational (380/400) and touristic (365/400) appeal. The applied GAM shows the museum as a geosite with high principal and additional value, placing it in the Z33 field of the global valuation matrix. In addition, the semiquantitative and qualitative evaluation made it possible to describe the importance of the museum and its collections in the development of the area. The study carried out qualified the museum as a mining site with an appropriate valuation, an example of ex-situ geological heritage conservation and a basis for geotourism development.

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