uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
3D seismic reflection surveying at the CO2SINK project site, Ketzin, Germany: A study for extracting shallow subsurface information
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
2009 (English)In: Near Surface Geophysics, ISSN 1569-4445, ISSN 1569-4445, Vol. 7, no 2, 75-91 p.Article in journal (Refereed) Published
Abstract [en]

Three-dimensional (3D) reflection seismic data were recorded as part of a pilot scale carbon dioxide (CO2) geological storage project (CO2 SINK) with the aim of mapping the structural geometry of the site and providing a 3D baseline prior to CO2 injection. Standard processing  originally focused on the storage target, a saline aquifer at 500-700 m  depth and successful imaged coherent reflections from 150 ms to 900 ms in the seismic volume. However, the relatively sparse distribution of sources and receivers, the frequency content of the data and artefacts   of the processing resulted in the uppermost 150 ms being poorly   resolved. This depth range contains caprock, shallow faults and an aquifer system. Thus, characterizing the shallow subsurface is important in terms of site delineation of potential leakage paths and monitoring after CO2 injection. In order to study the potential of   mapping the uppermost reflectors and shallow structures associated with  major fault zones, a comprehensive reprocessing effort on a subset of the 3D data was performed. The challenge in imaging shallow reflections is dependent upon the separation of ground roll and refracted energy   from the reflected energy, as well as compensation for time shifts due   to statics. Among the processing sequences, refraction static corrections, careful muting and filtering, velocity analysis and 3D   time migration were key steps for enhancing the resolution and   coherency of shallow seismic reflections. This study images a  previously unmapped horizon, close to the Quaternary-Tertiary boundary, at about 95-120 ms (similar to 65-90 m depth). Correlation of lateral variations in reflectivity along this boundary, lateral velocity   variations in the tomographic image and the seismic signature in   modelling studies suggest an aquifer/aquitard complex and variable   lithology with associated localized silty or clayey sediments,   overlying the Tertiary Rupelton clay unit. In the previous processing   it was not clear if the deeper faults imaged on the 3D seismic survey   extended to shallower levels than the base Tertiary. Thus, a   comprehensive fault detection technique, multi-attributes and neural networks analysis, was employed in this study to allow a more reliable  fault geometry to be interpreted. Tracking of faults in the seismic   image and comparisons with a tomography study indicate that some deeper faults may penetrate into the overlying Tertiary unit. These findings are important for understanding potentially risky areas and can be used as a database for future monitoring programmes at the site.

Place, publisher, year, edition, pages
2009. Vol. 7, no 2, 75-91 p.
Keyword [en]
CO2 STORAGE; DEPTH CHARACTERIZATION; P-WAVE; VELOCITY; AQUIFERS; SLEIPNER; ROCK; ACQUISITION; SEDIMENTS; PHYSICS
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-97521DOI: 10.3997/1873-0604.2008036ISI: 000266452500001OAI: oai:DiVA.org:uu-97521DiVA: diva2:172501
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2017-01-25Bibliographically approved
In thesis
1. 2D and 3D Seismic Surveying at the CO2SINK Project Site, Ketzin, Germany: The Potential for Imaging the Shallow Subsurface
Open this publication in new window or tab >>2D and 3D Seismic Surveying at the CO2SINK Project Site, Ketzin, Germany: The Potential for Imaging the Shallow Subsurface
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Seismic traveltime inversion, traveltime tomography and seismic reflection techniques have been applied for two dimensional (2D) and three dimensional (3D) data acquired in conjunction with site characterization and monitoring aspects at a carbon dioxide (CO2) geological storage site at Ketzin, Germany (the CO2SINK project). Conventional seismic methods that focused on investigating the CO2 storage and caprock formations showed a poor or no image of the upper 150 m. In order to fill this information gap, an effort on imaging the shallow subsurface at a potentially risky area at the site is the principal goal of this thesis.

Beside this objective, a seismic source comparison from a 2D pilot study for acquisition parameter testing at the site found a weight drop source suitable with respect to the signal penetration, frequency content of the data and minimizing time and cost for 3D data acquisition.

For the Ketzin seismic data, the ability to obtain high-quality images is limited by the acquisition geometry, source-generated noise and time shifts due to near-surface effects producing severe distortions in the data. Moreover, these time shifts are comparable to the dominant periods of the reflections and to the size of structures to be imaged. Therefore, a combination of seismic refraction and state-of-the-art processing techniques, including careful static corrections and more accurate velocity analysis, resulted in key improvements of the images and allowed new information to be extracted. The results from these studies together with borehole information, hydrogeologic models and seismic modeling have been combined into an integrated interpretation. The boundary between the Quaternary and Tertiary unit has been mapped. The internal structure of the Quaternary sediments is likely to be complicated due to the shallow aquifer/aquitard complex, whereas the heterogeneity in the Tertiary unit is due to rock alteration associated with fault zones. Some of the major faults appear to project into the Tertiary unit. These findings are important for understanding the potentially risky anticline crest and can be used as a database for the future monitoring program at the site.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2008. 80 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 550
Keyword
Inversion, Traveltime tomography, 3D seismic surveys, Seismic velocity, Seismic source, CO2SINK project
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-9273 (URN)978-91-554-7276-4 (ISBN)
Public defence
2008-10-07, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Opponent
Supervisors
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2016-05-13Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Juhlin, Christopher

Search in DiVA

By author/editor
Juhlin, Christopher
By organisation
Department of Earth Sciences
In the same journal
Near Surface Geophysics
Earth and Related Environmental Sciences

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 544 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf