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Time-lapse Analysis of Borehole and Surface Seismic Data, and Reservoir Characterization of the Ketzin CO2 Storage Site, Germany
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The CO2SINK (and CO2MAN) project is the first onshore CO2 storage project in Europe. The research site is located near the town of Ketzin, close to Potsdam in Germany. Injection started in June 2008, with a planned injection target of 100,000 tonnes of CO2. In February 2011, around 45, 000 tons of CO2 had been injected into the saline aquifer at an approximate depth of 630 m. This thesis focuses on time-lapse analysis of borehole seismic data, surface seismic data and reservoir characterization at the Ketzin site.

Baseline Moving Source Profiling (MSP) data were acquired in the borehole Ketzin 202/2007 (OW2), along seven lines in 2007. The zero-offset Vertical Seismic Profile (VSP) data were acquired in the same borehole. The main objective of the VSP and MSP survey was to generate high-resolution seismic images around the borehole. After modeling and data processing, the sandy layers within the Stuttgart Formation can potentially be imaged in the VSP and MSP data whereas reflections from these layers are not as clearly observed in the 3D surface seismic data.

2D and pseudo-3D time-lapse seismic surveys were conducted at the Ketzin site. Interpretation of 2D baseline and repeat stacks shows that no CO2 leakage related time lapse signature is observable where the 2D lines allow monitoring of the reservoir. This is consistent with the time-lapse results of the 3D surveys showing an increase in reflection amplitude just centered around the injection well. The results from the pseudo-3D surveys are also consistent with the 3D seismic time-lapse studies and show that the sparse pseudo-3D geometry can be used to qualitatively map the CO2 in the reservoir with significantly less effect than the full 3D surveying. The 2nd pseudo-3D repeat survey indicates preferential migration of the CO2 to the west. There are no indications of migration into the caprock on either of the repeat surveys.

Amplitude Versus Offset (AVO) analysis was performed on both 2D and 3D repeat surveys. A Class 3 AVO anomaly is clearly observed on the 3D repeat data and matches the synthetic modeling well. No AVO anomaly was observed on the 2D repeat data, which was anticipated, but the result shows signs of a pressure response at the reservoir level in the data. Reflection coefficients were calculated using surface seismic data (3D and pseudo-3D) at the site. Pre-injection calculations agree well with calculations from logging data. Post-injection calculations are in general agreement with the seismic modeling, but generally show higher amplitudes than those expected. The full 3D data show a better image of the reflection coefficients before and after injection than the pseudo-3D data and can potentially be used to make quantitative calculations of CO2 volumes. The pseudo-3D data only provide qualitative information.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2012. , 70 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 887
Keyword [en]
Amplitude anomaly, AVO analysis, Carbon dioxide storage, Moving source profile survey, Reflection coefficient, Reservoir characterization, Static correction, Time-lapse analysis
National Category
Geophysics
Research subject
Geophysics with specialization in Seismology
Identifiers
URN: urn:nbn:se:uu:diva-163013ISBN: 978-91-554-8241-1 (print)OAI: oai:DiVA.org:uu-163013DiVA: diva2:462458
Public defence
2012-02-03, Axel Hambergsalen, Geocentrum, Villavagen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2012-01-11 Created: 2011-12-07 Last updated: 2012-01-16
List of papers
1. Moving source profile data processing, modelling and comparison with 3D surface seismic data at the CO2SINK project site, Ketzin, Germany
Open this publication in new window or tab >>Moving source profile data processing, modelling and comparison with 3D surface seismic data at the CO2SINK project site, Ketzin, Germany
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2010 (English)In: Near Surface Geophysics, ISSN 1569-4445, E-ISSN 1873-0604, ISSN 1569-4445, Vol. 8, no 6, 601-610 p.Article in journal (Refereed) Published
Abstract [en]

Baseline moving source profiling data were acquired in borehole Ketzin 202/2007 along seven lines at the Ketzin CO2 injection site in 2007. The data were recorded on eight three-component receivers spaced 10 m apart over a depth interval of 470-540 m. The main objective of the moving source profile survey was to generate high-resolution seismic images around the borehole. This was especially important given that the 3D surface seismic data in the area have a low fold at the injection site. Mapping of the sandy layers in the target formation (Stuttgart Formation) at around 630 m, the approximate CO2 injection depth, was another objective of the research. A comparison with repeat moving source profile surveys, during and after the injection, will be done in the future. A processing sequence consisting in hodogram analysis, wavefield separation and prestack migration was applied to the moving source profile data. A median filter was used to separate the downgoing and upgoing wave modes. The data were processed to generate depth migrated images in the vicinity of the borehole that could be compared with the 3D surface seismic data. Both the modelling studies that were carried out and the migrated images, indicate that the sandy layers within the Stuttgart Formation can potentially be imaged in the moving source profile data whereas reflections from these layers are not as clearly observed in the 3D surface seismic data.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-143659 (URN)10.3997/1873-0604.2010022 (DOI)000285399200017 ()
Available from: 2011-01-24 Created: 2011-01-24 Last updated: 2017-12-11Bibliographically approved
2. Enhancing seismic data resolution using the prestack blueing technique: An example from the Ketzin CO2 injection site, Germany
Open this publication in new window or tab >>Enhancing seismic data resolution using the prestack blueing technique: An example from the Ketzin CO2 injection site, Germany
2010 (English)In: Geophysics, ISSN 0016-8033, E-ISSN 1942-2156, Vol. 75, no 6, V101-V110 p.Article in journal (Refereed) Published
Abstract [en]

Restricted resolution imposes limits on the detection of subsurface geologic features using surface seismic data. Despite great improvements in acquisition and processing techniques in recent years, seismic data still suffer from limited resolution. Detailed subsurface information on the geologic conditions at depth cannot always be attained from conventional surface seismic data. For the area of this study, the carbon dioxide (CO2) storage site at Ketzin, Germany, high seismic resolution is required for mapping the internal structure of the main target reservoir. Processing of the 3D surface seismic data using conventional methods did not provide optimum resolution. The spectral blueing technique attempts to enhance the surface seismic data resolution. Well-log data generally show a blue spectrum with higher-amplitudes at the higher frequencies than the commonly assumed white reflection series. By designing and applying one or several operators to poststack data, it has been possible to better match the reflectivity series and improve resolution. Applying the blueing operator to prestack data was investigated to possibly improve seismic resolution, produce more consistent results, and cause fewer ringing artifacts than when applied to poststack data. Prestack blueing, poststack blueing, and no blueing of the Ketzin 3D seismic data were compared with zero-offset vertical seismic profile (VSP) and synthetic seismograms. The comparison shows that prestack spectral blueing can indeed enhance seismic resolution with fewer artifacts associated with it than the poststack technique. The prestack and poststack spectral blueing approaches improve the well to seismic tie.

Keyword
Seismic resolution, Spectral blueing, CO2SINK Project
National Category
Earth and Related Environmental Sciences
Research subject
Geophysics with specialization in Seismology
Identifiers
urn:nbn:se:uu:diva-104175 (URN)10.1190/1.3483900 (DOI)000285767900055 ()
Projects
CO2SINK Project
Available from: 2009-05-27 Created: 2009-05-27 Last updated: 2017-12-13Bibliographically approved
3. Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO(2) injection site Ketzin (Germany)
Open this publication in new window or tab >>Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO(2) injection site Ketzin (Germany)
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2011 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 75, no 1, 124-139 p.Article in journal (Refereed) Published
Abstract [en]

The Ketzin project provides an experimental pilot test site for the geological storage of CO(2). Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO(2) had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO(2), and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon.

Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey.

Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO(2) related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO(2) signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO(2), as expected, but shows signs of a pressure response in the repeat data.

Keyword
Seismic, Monitoring, Ketzin, Time-lapse, Static Correction, CO(2)
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-160421 (URN)10.1016/j.jappgeo.2011.05.005 (DOI)000295346400012 ()
Available from: 2011-10-24 Created: 2011-10-24 Last updated: 2017-12-08Bibliographically approved
4. Time-lapse analysis of sparse 3D seismic data from the CO2 storage pilot site at Ketzin, Germany
Open this publication in new window or tab >>Time-lapse analysis of sparse 3D seismic data from the CO2 storage pilot site at Ketzin, Germany
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2012 (English)In: Journal of Applied Geophysics, ISSN 0926-9851, E-ISSN 1879-1859, Vol. 84, 14-28 p.Article in journal (Refereed) Published
Abstract [en]

The Ketzin pilot site is the first European on-shore CO2 storage project site. Injection started in June 2008 and until the latest repeat survey in February 2011 around 45,000 t of CO2 had been injected into a saline aquifer at approximately 630 m depth. Seismic monitoring methods that have been applied at the Ketzin site comprise baseline and repeat observations at various scales. We present here time-lapse results from sparse 3D seismic data measurements at Ketzin, which were acquired to link downhole surveys with conventional 3D surface seismic surveys. The results are consistent with the 3D seismic time-lapse studies over the injection site and show that the sparse 3D geometry can be used to map the CO2 in the reservoir at a significantly lower effort than the conventional 3D surveying. The last repeat survey indicates preferential migration of the CO2 to the west. There are no indications of migration into the caprock on either of the repeat surveys.

Keyword
CO2 storage, Monitoring, Seismic acquisition, Time-lapse
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-163001 (URN)10.1016/j.jappgeo.2012.05.010 (DOI)000307613100002 ()
Available from: 2011-12-07 Created: 2011-12-07 Last updated: 2017-12-08Bibliographically approved
5. Estimation of changes in the zero-offset reflection coefficient due to CO2 injection at Ketzin, Germany
Open this publication in new window or tab >>Estimation of changes in the zero-offset reflection coefficient due to CO2 injection at Ketzin, Germany
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(English)Manuscript (preprint) (Other academic)
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-163004 (URN)
Available from: 2011-12-07 Created: 2011-12-07 Last updated: 2015-09-18

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Citation style
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  • Other locale
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Output format
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