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Feasibility of utilizing wavelet phase to map the CO2 plume at the Ketzin pilot site, Germany
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.ORCID iD: 0000-0002-9755-3941
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
CNOOC Research Institute.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
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(English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478Article in journal (Refereed) In press
Abstract [en]

Spectral decomposition is a powerful tool that can provide geological details dependentupon discrete frequencies. Complex spectral decomposition using inversionstrategies differs from conventional spectral decomposition methods in that it producesnot only frequency information but also wavelet phase information. Thismethod was applied to a time-lapse three-dimensional seismic dataset in order totest the feasibility of using wavelet phase changes to detect and map injected carbondioxide within the reservoir at the Ketzin carbon dioxide storage site, Germany.Simplified zero-offset forward modelling was used to help verify the effectiveness ofthis technique and to better understand the wavelet phase response from the highlyheterogeneous storage reservoir and carbon dioxide plume. Ambient noise and signalto-noise ratios were calculated from the raw data to determine the extracted waveletphase. Strong noise caused by rainfall and the assumed spatial distribution of sandstonechannels in the reservoir could be correlated with phase anomalies. Qualitativeand quantitative results indicate that the wavelet phase extracted by the complexspectral decomposition technique has great potential as a practical and feasible toolfor carbon dioxide detection at the Ketzin pilot site.

Keyword [en]
Time-lapse, Signal processing, Inversion, Modelling, Seismic.
National Category
URN: urn:nbn:se:uu:diva-300994DOI: 10.1111/1365-2478.12383OAI: oai:DiVA.org:uu-300994DiVA: diva2:953158
Available from: 2016-08-17 Created: 2016-08-17 Last updated: 2016-09-02
In thesis
1. 3D Time-lapse Analysis of Seismic Reflection Data to Characterize the Reservoir at the Ketzin CO2 Storage Pilot Site
Open this publication in new window or tab >>3D Time-lapse Analysis of Seismic Reflection Data to Characterize the Reservoir at the Ketzin CO2 Storage Pilot Site
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

3D time-lapse seismics, also known as 4D seismics, have great potential for monitoring the migration of CO2 at underground storage sites. This thesis focuses on time-lapse analysis of 3D seismic reflection data acquired at the Ketzin CO2 geological storage site in order to improve understanding of the reservoir and how CO2 migrates within it.

Four 3D seismic surveys have been acquired to date at the site, one baseline survey in 2005 prior to injection, two repeat surveys in 2009 and 2012 during the injection period, and one post-injection survey in 2015. To accurately simulate time-lapse seismic signatures in the subsurface, detailed 3D seismic property models for the baseline and repeat surveys were constructed by integrating borehole data and the 3D seismic data. Pseudo-boreholes between and beyond well control were built. A zero-offset convolution seismic modeling approach was used to generate synthetic time-lapse seismograms. This allowed simulations to be performed quickly and limited the introduction of artifacts in the seismic responses.

Conventional seismic data have two limitations, uncertainty in detecting the CO2 plume in the reservoir and limited temporal resolution. In order to overcome these limitations, complex spectral decomposition was applied to the 3D time-lapse seismic data. Monochromatic wavelet phase and reflectivity amplitude components were decomposed from the 3D time-lapse seismic data. Wavelet phase anomalies associated with the CO2 plume were observed in the time-lapse data and verified by a series of seismic modeling studies. Tuning frequencies were determined from the balanced amplitude spectra in an attempt to discriminate between pressure effects and CO2 saturation. Quantitative assessment of the reservoir thickness and CO2 mass were performed.

Time-lapse analysis on the post-injection survey was carried out and the results showed a consistent tendency with the previous repeat surveys in the CO2 migration, but with a decrease in the size of the amplitude anomaly. No systematic anomalies above the caprock were detected. Analysis of the signal to noise ratio and seismic simulations using the detailed 3D property models were performed to explain the observations. Estimation of the CO2 mass and uncertainties in it were investigated using two different approaches based on different velocity-saturation models.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 73 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1407
CO2 storage, 3D Time-lapse (4D), Reservoir characterization, Seismic simulation, Spectral decomposition, Wavelet phase, Tuning frequency, Thin-layer thickness, Seismic monitoring, Seismic processing, Quantitative interpretation
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Research subject
Geophysics with specialization in Solid Earth Physics
urn:nbn:se:uu:diva-301003 (URN)978-91-554-9658-6 (ISBN)
External cooperation:
Public defence
2016-09-30, Hambergsalen, Geocentrum, Villavagen 16, Uppsala, 10:00 (English)
Available from: 2016-09-07 Created: 2016-08-17 Last updated: 2016-09-13

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