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Geological Structure and Time-Lapse Studies of CO2 Injection at the Ketzin Pilot Site, Germany
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

3D seismic time-lapse surveys (“4D seismics”) are an essential tool for large scale reservoir characterization. The target reservoir of the Ketzin pilot project for CO2 storage is a saline aquifer of the heterogeneous Stuttgart Formation (Upper Triassic) in the Northeast German Basin. The focus of this project is on testing and further developing monitoring CO2 storage technologies. For time-lapse seismic monitoring, three seismic surface sources were characterized with respect to S/N (signal to noise) ratios, signal penetration, and frequency content by analysis of raw shot gathers and stacked sections along two lines at the Ketzin site. Differences in reflectivity between these 2D lines reflect the differences in the nature of the sources tested and how they influence the signal bandwidth (resolution) and signal energy. All three sources image the target horizon. The weight drop source was recommended as the primary source for 3D surveys based mainly on logistics and cost. Results of processing, including equalization of a 4D (3D time-lapse) data set from the Ketzin site and cross-correlation, indicate that the injected CO2 can be monitored. The highly irregular amplitude response on the time-lapse data can be attributed to the reservoir heterogeneity. Time-lapse seismic processing, petrophysical measurements on core samples and geophysical logging of CO2 saturation levels allow for an estimate of the total amount of CO2 visible in the seismic data to be made. In spite of some uncertainty, the close agreement between the injected and observed amount is encouraging for quantitative monitoring of a CO2 storage site using seismic methods. By integrating seismic modeling and multiphase fluid flow simulations, the impact of the reservoir temperature on the 4D seismic data from Ketzin was estimated. The modeled time-lapse seismic differences for two temperature scenarios present in the reservoir are minor regarding the qualitative analysis. However, the influence of temperature on the volumetric estimation of the CO2 using the 4D seismic data is significant. Future issues to be considered include expanding the temperature range (34-38°C in this study) to be investigated and the resulting effects on the seismic response, as well as the role of the reservoir heterogeneity. In addition, it would be important to investigate the impact of temperature on the CO2 storage at other sites with favorable P-T conditions in the reservoir. Further seismic modeling using results of petrophysical experiments for estimating the effect of the CO2 injection at the Ketzin site on the AVA/AVO response on time lapse seismic data was performed. Two effects were considered: the CO2-saturation- and the pore-pressure-related effects. The results indicate that it is worth investigating if it is possible to discriminate between these effects on future 3D repeat surveys at the Ketzin site.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , p. 96
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1026
National Category
Geophysics
Identifiers
URN: urn:nbn:se:uu:diva-196127ISBN: 978-91-554-8613-6 (print)OAI: oai:DiVA.org:uu-196127DiVA: diva2:609260
Public defence
2013-04-19, Hambergsalen, Villavagen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2013-03-27 Created: 2013-03-04 Last updated: 2016-07-20Bibliographically approved
List of papers
1. Comparison of surface seismic sources at the CO2SINK site, Ketzin, Germany
Open this publication in new window or tab >>Comparison of surface seismic sources at the CO2SINK site, Ketzin, Germany
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2009 (English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 57, no 1, p. 125-139Article in journal (Refereed) Published
Abstract [en]

In 2004 three seismic surface sources (VIBSIST, accelerated weight drop and MiniVib) were tested in a pilot study at the Ketzin test site, Germany, a study site for geological storage of CO2 (EU project CO2SINK). The main objectives of this pilot study were to 1) evaluate the response of the Ketzin site to reflection seismics, especially at the planned injection depth, 2) test different acquisition parameters and 3) use the results to guide the planning of the 3D survey. As part of these objectives, we emphasize the source performance comparison in this study. The sources were tested along two perpendicular lines of 2.4 km length each. Data were acquired by shooting at all stations (source and receiver spacing of 20 m) on both lines, allowing common-midpoint stacked sections to be produced. The sources' signal characteristics based on signal-to-noise ratio, signal penetration and frequency content of raw shot records were analysed and stacked sections were compared. The results show that all three surface sources are suitable for reflection seismic studies down to a depth of about 1 km and provide enough bandwidth for resolving the geological targets at the site, i.e., the Weser and Stuttgart Formations. Near surface conditions, especially a thick weathering layer present in this particular area, strongly influence the data quality, as indicated by the difference in reflectivity and signal-to-noise ratio of the two common-midpoint lines. The stacked sections of the MiniVib source show the highest frequency signals down to about 500 ms traveltime (approximately 500 m depth) but also the shallowest signal penetration depth. The VIBSIST source generates signals with the highest signal-to-noise ratio and greatest signal penetration depth of the tested sources. In particular, reflections below 900 ms (approximately 1 km depth) are best imaged by the VIBSIST source. The weight drop performance lies in between these two sources and might be recommended as an appropriate source for a 3D survey at this site because of the shorter production time compared to the VIBSIST and MiniVib sources.

National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-97518 (URN)10.1111/j.1365-2478.2008.00737.x (DOI)000261447600010 ()
Available from: 2008-09-05 Created: 2008-09-05 Last updated: 2017-12-14Bibliographically approved
2. Monitoring and volumetric estimation of injected CO2 using 4D seismic, petrophysical data, core measurements and well logging: a case study at Ketzin, Germany
Open this publication in new window or tab >>Monitoring and volumetric estimation of injected CO2 using 4D seismic, petrophysical data, core measurements and well logging: a case study at Ketzin, Germany
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2012 (English)In: Geophysical Prospecting, ISSN 0016-8025, E-ISSN 1365-2478, Vol. 60, no 5, p. 957-973Article in journal (Refereed) Published
Abstract [en]

More than 50 000 tons of CO2 have been injected at Ketzin into the Stuttgart Formation, a saline aquifer, at approximately 620 m depth, as of summer 2011. We present here results from the 1st repeat 3D seismic survey that was performed at the site in autumn 2009, after about 22 000 tons of CO2 had been injected. We show here that rather complex time-lapse signatures of this CO2 can be clearly observed within a radius of about 300 m from the injection well. The highly irregular amplitude response within this radius is attributed to the heterogeneity of the injection reservoir. Time delays to a reflection below the injection level are also observed. Petrophysical measurements on core samples and geophysical logging of CO2 saturation levels allow an estimate of the total amount of CO2 visible in the seismic data to be made. These estimates are somewhat lower than the actual amount of CO2 injected at the time of the survey and they are dependent upon the choice of a number of parameters. In spite of some uncertainty, the close agreement between the amount injected and the amount observed is encouraging for quantitative monitoring of a CO2 storage site using seismic methods.

Keyword
Data processing, Monitoring, Rock Physics, Seismics, Time lapse
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-182008 (URN)10.1111/j.1365-2478.2012.01045.x (DOI)000307899000009 ()
Available from: 2012-10-08 Created: 2012-10-02 Last updated: 2017-12-07Bibliographically approved
3. Impact of temperature on CO2 storage at the Ketzin site based on fluid flow simulations and seismic data
Open this publication in new window or tab >>Impact of temperature on CO2 storage at the Ketzin site based on fluid flow simulations and seismic data
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2013 (English)In: International Journal of Greenhouse Gas Control, ISSN 1750-5836, E-ISSN 1878-0148, Vol. 19, p. 775-784Article in journal (Refereed) Published
Abstract [en]

Temperature is one of the main parameters influencing the properties of CO2 during storage in saline aquifers since it along with pressure and co-constituents controls the phase behavior of the CO2/brine mixture. When the CO2 replaces brine as a free gas it is well known to affect the elastic properties of porous media considerably. In order to track the migration of geologically stored CO2 at the Ketzin site, 3D time-lapse seismic data were acquired by means of a baseline (pre-injection) survey in autumn 2005 and a first monitor survey in autumn 2009. During this period the temperature in the storage reservoir near the injection well was observed to have increased from 34 °C to 38 °C.

This temperature increase led us to investigate the potential impact of temperature on the seismic response to the CO2 injection and on the CO2 mass estimations based on the Ketzin 4D seismic data. Two temperature scenarios in the reservoir (34 °C and 38 °C) were studied using multiphase fluid flow modeling. The simulations show that the impact of temperature on the seismic response is minor, but that the impact of the temperature on the CO2 mass estimations is significant and can, with the help of the multiphase fluid flow simulations, be explained mostly by the impact on the density of the CO2.

National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-196121 (URN)10.1016/j.ijggc.2013.05.001 (DOI)000332396700014 ()
Available from: 2013-03-04 Created: 2013-03-04 Last updated: 2017-12-06Bibliographically approved
4. Seismic modeling of the AVO/AVA response to CO2 injection at the Ketzin site, Germany
Open this publication in new window or tab >>Seismic modeling of the AVO/AVA response to CO2 injection at the Ketzin site, Germany
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2013 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Over 64 kilotons of CO2 have been injected (May, 2013) into a heterogeneous sandstone reservoir (saline aquifer) at 630-650 m depth. 4D seismics have been applied to monitor CO2 at the Ketzin site. However, the obtained time-lapse seismic signals have been so far interpreted as being caused by fluid saturation changes only. Modeling of the AVO/AVA response allows us to study two kinds of effects: CO2-saturation- and pore-pressure-related effects. Our results indicate that it is rather infeasible to discriminate between both these effects at the Ketzin site dealing with the real seismic data with limited signal/noise ratios.

Series
Energy Procedia, ISSN 1876-6102 ; 40
Keyword
CO2 storage, seismic monitoring, AVA/AVO, petrophysics, pore pressure, fluid saturation
National Category
Geophysics
Identifiers
urn:nbn:se:uu:diva-210139 (URN)10.1016/j.egypro.2013.08.056 (DOI)000345364200056 ()
Conference
General Assembly of the Division-on-Energy-Resources-and-the-Environment of European-Geosciences-Union
Available from: 2013-11-01 Created: 2013-11-01 Last updated: 2017-01-25Bibliographically approved

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