Anisotropic AVO: Implications for reservoir characterization

Asaka, Michinori

doi:10.1190/tle37120916.1

Cited by 18 publications

(5 citation statements)

References 13 publications

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“…Since the CIGs produced from the RTM partial images are ideal for studying the AVO effect relative to the CIG locations (Yan and Xie, 2012), future studies should exploit this potential for better scrutinizing and extracting physical property information from seismic data. Additionally, crystalline environments with a high degree of metamorphism may even show a strong anisotropic AVO response (Asaka, 2018). Utilizing the isotropic or anisotropic AVO analysis as a supplementary tool to characterize various rocks and mineral deposits from the seismic data is ideal in mineral exploration (Harrison and Urosevic, 2012).…”

Section: Discussionmentioning

confidence: 99%

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

Ding

Malehmir

2021

Solid Earth

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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 preferred for imaging the targets at great depth. One major goal for seismic methods is to produce a reliable image of the reflectors underground given the typical discontinuous geology in crystalline environments with low signal-to-noise ratios. In this study, we investigate the usefulness of the reverse time migration (RTM) imaging algorithm in hardrock environments by applying it to a 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. In order to obtain a reliable RTM image, we performed a detailed data pre-processing flow to deal with random noise, near-surface effects, and irregular receiver and source spacing, which can downgrade the final image if ignored. Exemplified with the Ludvika data, the resultant RTM image not only delineates the iron oxide deposits down to 1200 m depth as shown from previous studies, but also provides a better inferred ending of sheet-like mineralization. Additionally, the RTM image provides much-improved reflection of the dike and crosscutting features relative to the mineralized sheets when compared to the images produced by Kirchhoff migration in the previous studies. Two of the imaged crosscutting features are considered to be crucial when interpreting large-scale geological structures at the site and the likely disappearance of mineralization at depth. Using a field dataset acquired in hardrock environment, we demonstrate the usefulness of RTM imaging workflows for deep targeting mineral deposits.

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Section: Discussionmentioning

confidence: 99%

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

Ding

Malehmir

2021

Solid Earth

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“…Additionally, crystalline environment with high degree of metamorphism may even show strong anisotropy to cause anisotropic AVO response (Asaka, 2018). Utilizing the isotropic/anisotropic AVO analysis as a supplementary tool to characterise various rocks and mineral deposits from the seismic data is ideal in mineral exploration (Harrison and Urosevic, 2012).…”

Section: Discussionmentioning

confidence: 99%

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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“…Accounting for anisotropy has strong implication for reservoir characterization, because its presence might cause significant problems in the interpretation of active seismic data and therefore on the properties of investigated depth structures (e.g. Asaka ). We have seen that RFs can provide important information on the subsurface location and character of seismic anisotropy from passively recorded data.…”

Section: Discussionmentioning

confidence: 99%

Probing crustal anisotropy by receiver functions at the deep continental drilling site KTB in Southern Germany

Bianchi

Bokelmann

2019

Geophysical Prospecting

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Seismic anisotropy is a unique observational tool for remotely studying deformation and stress within the Earth. Effects of anisotropy can be seen in seismic data; they are due to mineral alignment, fractures or layering. Seismic anisotropy is linked to local stress and strain, allowing modern geophysics to derive geomechanical properties from seismic data for supporting well planning and fracking. For unravelling anisotropic properties of the crust, the teleseismic receiver functions methodology has started to be widely applied recently due to its ability in retrieving the three‐dimensional characteristics of the media sampled by the waves. The applicability of this technique is tested here by a field test carried out around the Kontinental Tiefbohrung site in southeastern Germany. We compare our results to previous investigations of the metamorphic rock pile of the Zone Erbendorf‐Vohenstrauss, drilled down to 9 km depth, which sampled an alternating sequence of paragneiss and amphibolite, in which a strong foliation has been produced by ductile deformation. The application of the receiver functions reveals the presence of two distinct anisotropic layers within the metamorphic rock pile at 0–4 km and below 6 km depth, with up to 8% anisotropy; the depth of these two layers corresponds to the location of mica‐rich paragneiss which show intense foliation, and finally proves the relation between the signal in the receiver functions, rock texture and presence of cracks. We have now the capability of providing insights from passive seismic data on geomechanical properties of the rocks, useful for geological exploration and engineering purposes, which will help influencing expensive drilling decisions thanks to future application of this seismic technique.

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Anisotropic AVO: Implications for reservoir characterization

Cited by 18 publications

References 13 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

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

Probing crustal anisotropy by receiver functions at the deep continental drilling site KTB in Southern Germany

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