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The first post-injection seismic monitor survey at the Ketzin pilot CO2 storage site: results from time-lapse analysis
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.ORCID iD: 0000-0002-9755-3941
GFZ German Research Centre for Geosciences.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
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 1365-2478, GP-2016-2250Article in journal (Refereed) Submitted
Abstract [en]

The injection of CO2 at the Ketzin pilot CO2 storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO2 was injected into a saline aquifer. A third repeat 3D seismic survey, serving as the first post-injection survey was acquired in 2015, aiming to investigate the recent movement of the injected CO2. Consistent with the previous two time-lapse surveys, a predominantly WNW migration of the gaseous CO2 plume in the up-dip direction within the reservoir is inferred in this first post-injection survey. No systematic anomalies are detected through the reservoir overburden. The extent of the CO2 plume west of the injection site is almost identical to that found in the 2012 second repeat survey (after injection of 61 kt), however there is a significant decrease in its size east of the injection site. Assessment of the CO2 plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO2 dissolution and CO2 diffusion, in addition to the effects of ambient noise. 4D seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO2 after the second repeat survey and the CO2 being dissolved and diffused was reached by the time of the first post-injection survey. Considering the considerable uncertainties in CO2 mass estimation, both patchy and non-patchy saturation models for the Ketzin site were taken into consideration.

Keyword [en]
Seismic processing, Monitoring, 3D time-lapse (4D), CO2 sequestration
National Category
URN: urn:nbn:se:uu:diva-301005OAI: oai:DiVA.org:uu-301005DiVA: diva2:953165
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
National Category
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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