Downhole physical property logging for iron-oxide exploration, rock quality, and mining: An example from central Sweden

Maries, Georgiana; Malehmir, Alireza; Bäckström, Emma; Schön, Monika; Marsden, P.

doi:10.1016/j.oregeorev.2017.10.012

Cited by 30 publications

(33 citation statements)

References 39 publications

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“…Second, two inferred 3D fault planes have recently been imaged and picked from the recent 3D survey (Malehmir et al, 2020b). Third, one borehole (BB-14004) near the seismic acquisition line has both the density and sonic logging data (Figure 7a & 7b) (Maries et al, 2017).…”

Section: Rtm Results and Their Interpretationsmentioning

confidence: 99%

“…The ore deposits are primarily magnetite and hematite as sheet-like bodies. At the Blötberget site where this study focuses, the sheet-like mineral horizons show a moderate dip (around 30 − 45 ) towards the south-southwest based on the core logging data (Maries et al, 2017) and a recent 3D reflection survey in the area ( Malehmir et al, 2020b).…”

Section: Background Of the Study Areamentioning

confidence: 98%

“…However, because of recent feasibility studies and improved resources, as well as the growing iron ore market, Nordic Iron Ore (NIO) plans to reopen the mine and exploit the deposits at depth level of 400-420 m in the near future. Relevant to this study is the work by Maries et al (2017) on downhole logging study of the iron-oxide deposits at the site. As shown in the logging data, the strong density contrast between the iron-oxide deposits (~ 4500 kg.…”

Section: Background Of the Study Areamentioning

confidence: 99%

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Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

Ding¹,

Malehmir²

2020

Preprint

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Abstract. To discover or delineate mineral deposits and other geological features such as faults and lithological boundaries in their host rocks, seismic methods are a qualified choice, given their resolution power at depth. One major goal for seismic methods is to produce a reliable image of the subsurface given the typical discontinuous geology in crystalline environment with low signal-to-noise ratio. In this study, we investigate the usefulness of reverse time migration (RTM) imaging algorithm in hardrock environment by applying it to a legacy 2D dataset, which was acquired in the Ludvika mining area of central Sweden. We provide a how-to solution for applications of RTM in future and similar datasets. When using the RTM imaging technique properly, it is possible to obtain high-fidelity seismic images of the subsurface. Due to good amplitude preservation in the RTM image, the imaged reflectors provide indications to infer their geological origin. Aside from the chosen seismic imaging algorithm, we illustrate that two other important factors for successful RTM imaging workflows are the suitable acquisition and careful data pre-processing. Exemplified with the Ludvika legacy data, the RTM method allows imaging the iron-oxide deposits at a great level of detail down to 1200 m depth as shown from previous studies. It also provides much-improved images of the lithological contacts and crosscutting features relative to the mineralized sheets. Some of the imaged crosscutting features are considered to be crucial when interpreting large-scale geological structures of the site and the likely disappearance of mineralization at depth. The RTM imaging workflows have the potential to be used on hardrock seismic data and for deep targeting mineral deposits, a key message we would like to deliver in this article.

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Section: Rtm Results and Their Interpretationsmentioning

confidence: 99%

Section: Background Of the Study Areamentioning

confidence: 98%

Section: Background Of the Study Areamentioning

confidence: 99%

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Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

Ding¹,

Malehmir²

2020

Preprint

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“…A good understanding of reflection seismic response is better possible when physical properties are studied in-situ using downhole logging methods (Salisbury et al, 2000). Through years 2015-2016, six boreholes (400-550 m deep) were downhole logged using various probes; relevant for this study is the full-waveform triple sonic (Maries et al, 2017). Density measurements could only be done on core samples at 1 m interval.…”

Section: Physical Properties Of Iron-oxide Depositsmentioning

confidence: 99%

“…The Blötberget mining area ( Fig. 1) in central Sweden within the so-called Ludvika Mines was the target of an experimental sparse 3D reflection survey given a wealth of several earlier 2D seismic lines (e.g., Malehmir et al, 2017a;Balentrini et al, 2020;Bräunig et al, 2020;Maries et al, 2020;Markovic et al, 2020;Papadopoulou et al, 2020), downhole logging data (Maries et al, 2017) and publicly available high-resolution aeromagnetic data in the area. The seismic survey had two main objectives: (1) to delineate depth and lateral continuation of iron-oxide deposits and (2) to unravel important structures that may be relevant for deep mining and how the deposits are currently configured and extended at depth.…”

Section: Introductionmentioning

confidence: 99%

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

Malehmir¹,

Markovic²,

Marsden³

et al. 2020

Preprint

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Abstract. Many metallic mineral deposits have sufficient contrasts, particularly density, to be detectable using seismic methods. These deposits are sometimes significant for our society, 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 32t vibrator generating 1056 shot points in a fixed geometry setup. A linear sweep ranging from 10–160 Hz and 20 s long was generated three times per shot point. Shots were fired at every 10 m where possible and receivers placed at every 10–20 m. Notable quality data were acquired although the area is dominated by swampy places as well as by built-up roads and historical tailings. The data processing had to overcome these challenges in particular for the static corrections and strong surface-waves. A tailored for hardrock-setting-processing workflow was developed for handling such a dataset, where the use of mixed 2D and 3D refraction static corrections were relevant. The resulting seismic volume is rich in terms of reflectivity with clear southeast dipping reflections originated from iron-oxide deposits extending vertically and laterally at least 300 m beyond what was known from boreholes. We estimate potential additional resources from the 3D reflection seismic experiment on the order of 10 Mt worth drilling for detailed assessments. The mineralization is crosscut by at least two major sets of northwest dipping reflections interpreted to be dominantly normal faults and 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. The sparse 3D survey illustrates that performing cost-effective reflection surveys for mineral exploration is achievable if they are conducted and planned carefully, systematically and based on earlier experiences.

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Modelling 3D elastodynamic wave scattering due to density and Lamé parameter contrasts of near‐surface scatterers

Harmankaya

Kaslilar

2022

Near Surface Geophysics

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Investigating the near-surface structure of the Earth through geophysical methods is a crucial aspect in many areas of study in geotechnical engineering, environmental science and exploration. Among several geophysical methods, seismic-based ones are widely used for characterizing near-surface features that are distinguished by contrasts in elastic parameters. In this paper, we model 3D elastodynamic wave propagation and scattering using a method based on domain-type integral representation with Born approximation. We calculate the scattered wavefield by considering the first-order perturbations in density and Lamé parameter contrasts of scatterers. Contrasts in Lamé parameters can be useful for determining the material properties of subsurface structures in cases of weak contrasts in velocities accompanying considerable Lamé parameter variations. We examine the effects of each parameter contrast on a series of models involving a subsurface scatterer. We also compare the seismograms obtained from our method with those from a 3D finite-difference wavefield modelling program, where we observe good agreement between the modelling results. Sensitivity of the wavefield to the perturbation in each model parameter is also examined by calculating and analysing the Fréchet derivatives. In general, the method discussed here can provide a solid foundation for prospective imaging studies involving density and Lamé parameters simultaneously.

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Downhole physical property logging for iron-oxide exploration, rock quality, and mining: An example from central Sweden

Cited by 30 publications

References 39 publications

Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden

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

Modelling 3D elastodynamic wave scattering due to density and Lamé parameter contrasts of near‐surface scatterers

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