Alexandra Ivanova

A footprint of rainfall on land seismic data repeatability at the CO2 storage pilot site, Ketzin, Germany

Two vintages of land time-lapse seismic data were acquired in 2005 and in 2009 at the Ketzin CO2 storage site in Germany. The datasets showed some differences in frequency content, signal-to-noise ...

The First Post-injection Seismic Monitor Survey at the Ketzin Pilot CO2 Storage Site: Results from Time-lapse Analysis

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 ...

Preliminary Seismic Time-lapse Results from the First Post-injection Survey at the Ketzin Pilot Site

Since the CO2SINK project start in April 2004, different methods involving seismics, geoelectrics andpressure-temperature monitoring have been applied at the Ketzin pilot site to map geological str ...

The relationship of soil-moisture saturation and time-lapse static shifts-An example from the Ketzin pilot site

Changes in the near surface are a major problem for land time-lapse seismic projects. Three seismic surveys at the Ketzin pilot site for CO2 storage in Germany demonstrated the importance of removing the variations in the shallow subsurface by applying spatially variable, relative time shifts to the different vintages prior to 4D interpretation. The main reason for these time shifts is a change in seismic velocities in the ground layer above the water table due to different soil-moisture saturation at the times of acquisition. We compared the variation in precipitation, groundwater level and trace-to-trace time shifts between the baseline and two monitor surveys and revealed that delays in reflected energy are in a qualitative sense, proportional to the moisture content in the soil.

Cross-correlation Time-lapse Static Corrections Versus Refraction Static Corrections on 4D Land Seismic CO2 Monitoring

Difficulties encountered during the processing of the timelapse 3D land-seismic data at the CO2 geological storage site at Ketzin, Germany, were to a large extent attributed to changes in near-surface velocities. Two workflows for processing of the 4D data were tested. The first one included re-calculation of the refraction static corrections based on new information about the near-surface from first breaks. This workflow showed that the near-surface changes could only imperfectly be resolved by new refraction static corrections. The second workflow included cross-correlation of the traces acquired at the same locations but during different campaigns and calculation of the prestack time shifts between the surveys. Both workflows demonstrated their capability to minimize the time-lapse noise and enhance the time-lapse reservoir signature. They provide similar time-lapse results, except that the cross-correlation workflow is quicker, more accurate and displays less time-lapse noise.

Estimation of Changes in the Reservoir Reflection Coefficient Due to CO2 Injection at Ketzin Site, Germany

Seismic amplitude information and data from an injection well (IW) and an observation well (OW2) are used to estimate reflection coefficients. Seismic volumes are extracted near the two boreholes from a baseline and a monitor survey. An anhydrite layer above the reservoir generates a high amplitude reflection and this is used for calibration. The amplitude equation of Ghaderi and Landro (2009) is used to estimate R0 for the reservoir. In the IW it is between 0.1-0.12 and in OW2 it is between 0.1-0.14 for the baseline survey. These values correspond well to logging data, providing confidence in our approach. We use the same method on the monitor survey and find R0 in the IW is now in the range 0.26-0.31 and R0 in OW2 is now 0.13-0.16, indicating lower CO2 saturation in OW2.

Discrimination between Pressure and Fluid Saturation Changes from Time-lapse Seismic Data at a CO2 Storage Site

Capture and geological storage of CO2 are an option to reduce greenhouse gas emissions. At Ketzin (Germany), the first European onshore pilot scale project was initiated in 2004. For this project, 3D time-lapse surveys are an essential tool for high resolution reservoir characterization. A baseline and a smaller repeat survey were acquired in Autumn 2005 before the injection and in Autumn 2009 after 22 kilotons of CO2 had been injected respectively. Seismic differences between the baseline and the monitor survey were previously interpreted as a fluid saturation effect only. However, for some fields undergoing injection both fluid and pressure changes have approximately the same degree of impact on seismic data. Landro (2001) described a method based on AVO analysis to discriminate the both types of changes directly from 3D time-lapse data for an oil-water contact. In this study we apply this method to a case of CO2 injection into a saline aquifer. We were able to detect the CO2 propagation in the reservoir, but currently a low signal-noise ratio prevents a clear discrimination between changes caused by fluid saturation and by pore pressure.

Geophysical Monitoring of Small Scale CO2-injection into a Deep Saline Aquifer - the Ketzin Pilot Site

The first European onshore CO2 storage site has been set up at Ketzin (Germany). It is operated as a small scale pilot site, with a special focus on the validation of various geophysical, geochemical and microbial monitoring technologies. The site has been developed within the EU funded project CO2SINK, coordinated by the GFZ German Research Centre for Geosciences and supported by numerous national and EU initiatives. Injection started in June 2008. Since then, between 1.000 and 2.000 tons of CO2 per month have been injected into sandstone layers of the Triassic Stuttgart Formation at a depth of 620 m to 650 m. The total amount of injected CO2 was 45.000 tons in February 2011. Injection is planned to continue until up to 100.000 tons will have been injected into the Stuttgart Formation. Currently, food grade CO2 is being injected at Ketzin, however, the technical and contractual preparations are underway to inject a limited amount of CO2 from a sequestration pilot facility.