CO2 Storage Pilot Site Research Articles

Performance and outlook for the SADAR array network at the Newell County facility

Since installation in November 2021, a sparse network of SADAR compact volumetric arrays has been continuously and persistently acquiring data for passive microseismic monitoring of the Newell County Facility (NCF) CO2 storage pilot site. This report summarises several fundamental results from a year of continuous monitoring of the NCF using the SADAR permanent array network, including an updated seismic velocity model determined from ground truth calibration events, the observed seismicity derived from the curated year-long bulletin, and quantified estimates of system performance. In particular, the bulletin includes more than 560 analyst-verified located events excluding those at the surface, with at least 200 considered to be well-located. We have documented noise reduction provided by coherent processing of SADAR array data in excess of 30 dB compared to surface sensors and signal-to-noise ratio (SNR) improvements up to 20 dB compared to single channels. Combining the bulletin information and performance measurements, we estimate magnitude of completeness Mc ≈ −2.5 Mw, and an event-to-receiver range for locatable events of at least 600 m from individual arrays. We conclude with a look at continuing and planned projects using the SADAR network at the NCF including tests of active source acquisition.

Assessment of Trans-Boundary Effects at LBr-1 CO2 Storage Pilot Site and Regulatory Solutions

The paper evaluates possible trans-boundary issues related to planned CO2 injection and storage at LBr-1, a candidate structure for a future geological storage pilot. LBr-1 is an abandoned hydrocarbon field situated in the Czech part of the Vienna Basin, close to the Czech-Slovak border. At first, currently valid national legislations relevant to CO2 geological storage in the Czech Republic and Slovakia were examined. In the second step, implications of the current legislation and regulatory regimes on the LBr-1 site itself were studied. The most important finding is that both the storage site and storage complex are located entirely on the territory of the Czech Republic. However, several trans-boundary issues were identified, especially those that are related to possible (even if unlikely) leakage of CO2 from the storage complex. Four possible types of trans-boundary issues were examined in detail – pressure build-up, possible leakage through boreholes, possible leakage through faults and possible migration of fluids out of the reservoir due to exceeding spill points for three scenarios – limited CO2 storage, full storage and CO2-EOR scenario. While pressure build-up and leakage through faults do not appear to cause trans-boundary issues, the other two phenomena need to be carefully considered. In case CO2 leakage appears either through abandoned wells or due to exceeding the southern spill point, the analysis of possible leakage pathways shows that the CO2 could migrate into the territory of Slovakia. These findings mean that a cooperation of regulatory authorities from both Czech and Slovak Republics will be necessary to prepare and operate the storage site. This is a significant complicating factor for possible injection of CO2 at LBr-1. Despite of this, the realization of a CO2 storage project on the site is considered viable, especially in the basic pilot storage scenario. This case avoids the spill-point related concerns (because of the limited extent of CO2 plume) and involves only a limited number of abandoned wells that need to be taken care of concerning their abandonment status.

Impact of SO2 on Alteration of Reservoir Rock with Ca-Deficient Conditions and Poor Buffering Capacity under a CO2 Geologic Storage Condition

The objective of this study is to evaluate the impact of SO2-CO2-water-rock interaction on the alteration of a reservoir rock having Ca-deficient conditions and little buffering capacity and its implication for porosity change near the injection well from a CO2 storage pilot site, Republic of Korea. For our study, three cases of experimental and geochemical modeling were carried out (pure CO2, 0.1% SO2 in CO2, and 1% SO2 in CO2, resp.) under realistic geologic storage conditions. Our results show that SO2 accelerated water-rock interactions by lowering the pH. In the 1% SO2 case, pH remained less than 2 during the experiments because of insufficient buffering capacity. Sulfate minerals were not precipitated because of an insufficient supply of Ca. Because the total volume of precipitated secondary minerals was less than that of the dissolved primary minerals, the porosity of rock increased in all cases. Chlorite largely contributed to the decrease in total rock volume although it formed only 4.8 wt.% of the rock. Our study shows that the coinjection of a certain amount of SO2 at CO2 storage reservoirs without carbonate and Ca-rich minerals can significantly increase the porosity by enhancing water-rock interactions. This procedure can be beneficial to CO2 injection under some conditions.

Results from twelve years of continuous monitoring of the soil CO2 flux at the Ketzin CO2 storage pilot site, Germany

The complete cycle of specific processes related to the geological storage of CO2 is investigated in detail at Ketzin since 2004. The scientific monitoring program targets different depths of the involved area and addresses the safety and reliability of the storage. The surface monitoring comprises long-term soil CO2 flux measurements and soil gas analyses. Annual mean values of soil CO2 fluxes ranged from 2.4 to 3.4 µmol m-2 s-1 before the injection started (2005-2008) and from 2.3 to 3.5 µmol m-2 s-1 during and after CO2 injection (2009-2016) and thus do not indicate an upward migration of the injected CO2.

Comparison of the microbial community composition of pristine rock cores and technical influenced well fluids from the Ketzin pilot site for CO2 storage

Two geological formations at the CO2 storage pilot site in Ketzin (Germany) were geochemically and microbiologically characterized to further evaluate changes resulting from CO2 injection. Well fluids were collected from both Stuttgart (storage formation, ~650 m depth) and Exter Formations (~400 m depth, overlying the caprock) either through pump tests or downhole samplings. Rock samples were retrieved during a deep drilling into the Exter Formation and primarily comprised quartz, ferrous dolomite or ankerite, calcite, analcime, plagioclase and clay minerals, as determined through X-ray diffraction analyses. In the rocks, the total organic carbon (TOC), which potentially contributes to microbial growth, was mostly below 1000 mg kg−1. The geochemical characterization of fluids revealed significant differences in the ionic composition between both formations. The microbial characterization was performed through fluorescence in situ hybridization and 16S rRNA gene fingerprinting. In the fluids obtained from the Stuttgart Formation, the microbial activity was affected by the relatively high TOC, introduced by the organic drill mud. The total cell counts were approximately 106 cells mL−1. The microbial community was characteristic of a saline deep biosphere environment enriched through increased carbon availability, with sulfate-reducing bacteria as the most abundant microorganisms (up to 60 % of total cells). Species belonging to halophilic/halotolerant Proteobacteria and Firmicutes were primarily detected. In Exter Formation rocks, Proteobacteria and Actinobacteria were detected. These data provide an explicit reference to further evaluate environmental changes and community shifts in the reservoir during CO2 storage and provide information for evaluating the storage efficiency and reliability.

An integrated core-based analysis for the characterization of flow, transport and mineralogical parameters of the Heletz pilot CO2 storage site reservoir

Heletz, Israel is the location for an onshore deep saline CO2 storage pilot site. The ‘Heletz sandstone’ is the building unit of the deep saline reservoir. Based on core samples of sandstone and caprock taken from the newly drilled injection (H18A) and monitoring wells (H18B), this article examines and reports the petrophysical properties of the Heletz Formation reservoir important for the short and long term trapping of CO2. A suite of laboratory and pore-scale CT-based modeling techniques are employed to determine the flow and transport parameters used by the continuum-scale numerical simulators and the mineral composition necessary for the understanding of mineral trapping processes.The effect of diagenesis on the reservoir parameters was determined in the laboratory using sedimentological, petrological, and petrophysical analyses. Variations in 87Sr/86Sr isotope composition and fluid inclusion analysis bring additional information about the diagenetic development and define the status quo of fluid–mineral reactions before CO2 injection. Cathodoluminescence microscopy and SEM/XRD revealed the amounts of minerals in the sandstone samples and caprock and explained the poor binding of the sandstone which may lead to mobilized material during injection. Digital image analysis on thin sections, cathodoluminescence, and SEM were integrated with attributes derived from mercury intrusion porosimetry, steady state gas permeametry or nuclear magnetic resonance to form an essential outline for the Heletz Formation reservoir. This relates storage space, injectivity and storage efficiency to features such as grain size, pore size distribution, effective porosity, intrinsic permeability, or tortuosity. Furthermore, the laboratory and numerical CT-based investigation techniques are compared and discussed. The benefit of combining experimental methods and numerical simulations on pore-scale models is the increase in confidence of the parameter accuracy, fundamental for the success of the planned activities at Heletz.

Geophysical monitoring at the Ketzin pilot site for CO2 storage: New insights into the plume evolution

To date, 3D time-lapse seismic monitoring at the Ketzin CO2 storage pilot site comprised a baseline survey conducted in 2005 and two repeat surveys conducted in 2009 and 2012. At the time of the first repeat survey (22–25kt of CO2), the CO2 plume was found to be concentrated around the injection well with a maximum lateral extent of approximately 300–400m and a thickness of 5–20m. Data from the 2012 survey (61kt of CO2), show further growth and migration of the amplitude anomaly interpreted to be induced by the CO2 injection. The anomaly is similar in shape to that obtained from the 2009 survey, but significantly stronger and larger by ∼150m in the N–S direction and by ∼200m in the E–W direction. In agreement with the 2009 survey, the new data show a westward propagation of the plume, a trend governed by the complex structure of the reservoir. No evidence of systematic changes in the seismic signature within the overburden is observed. A quantitative assessment of the plume reveals a 15% discrepancy with the injected amount, which could be attributed to the ongoing dissolution processes. However, the estimated quantity also contains significant uncertainty.

Zero-Offset VSP Monitoring of CO2Storage: Impedance Inversion and Wedge Modelling at the Ketzin Pilot Site

At the CO2storage pilot site near the town of Ketzin (35 km west of Berlin, Germany) the sandstone reservoir at 630 m–650 m depth is thin and heterogeneous. The time-lapse analysis of zero-offset VSP measurements shows that CO2-induced amplitude changes can be observed on near-well corridor stacks. Further, we investigate whether CO2-induced amplitude changes in the monitoring data can be used to derive geometrical and petrophysical parameters governing the migration of CO2within a brine saturated sandstone aquifer. 2D seismic-elastic modelling is done to test the processing workflow and to perform a wedge modelling study for estimation of the vertical expansion of the CO2plume. When using the NRMS error as a measure for the similarity between the modelled and recorded repeat traces, the best match is achieved for a plume thickness of 6-7 m within the reservoir sandstone of 8 m thickness. With band limited impedance inversion a velocity reduction at the top of the reservoir of 30%, influenced by casing reverberations as well as CO2injection, is found. The relation of seismic amplitude to CO2saturated layer thickness and CO2-induced changes in P-wave velocities are important parameters for the quantification of the injected CO2volume.

Four Years of Experience with a Permanent Seismic Monitoring Array at the Ketzin CO2 Storage Pilot Site

CO2 was injected into a saline aquifer near the town of Ketzin in Germany from July 2008 to August 2013. To monitor CO2- migration close to the injection well, TNO installed a fixed 2D seismic array of 120 meters length in 2009, with 3- component (3- C) geophones at the surface, 4-component receivers at 50 meters depth and a central vertical array of 4-component receivers. The test-bed is used both for the recording of high-quality active time-lapse seismic data as well as for continuous passive seismic data recording. Here we focus on the latest results obtained from active source experiments, micro-seismic data analysis and ambient noise seismic interferometry (ANSI) of passive seismic data. Data from two experiments with a source driven by linear motors (permanent) and an impact hammer source (semipermanent) were evaluated in order to assess the repeatability of the two source types.The repeatability of the first source was relatively high compared to the second source. After the stop of injection in August 2013, active seismic shots were acquired repeatedly on a daily basis. These data did not show significant impedance changes at reservoir level. Microseismic event analysis of passive seismic data detected a few local events originating from reservoir depth. In order to quantify these events the seismic array was successfully calibrated by using independent earthquake recording. This yielded estimates of the local magnitude for local events within the range [-2.5,0.5]. Recent work on ANSI focused on the application of this method on both synthetic and field data. The resulting reflection response shows a strong resemblance with outcomes from active shot reflection profiles, and the key reflectors at reservoir level have comparable characteristics

Geomechanical integrity verification and mineral trapping quantification for the Ketzin CO2 storage pilot site by coupled numerical simulations

Abstract Long-term integrated site behavior assessment with high spatial resolution on the reservoir scale requires a sophisticated workflow to represent the relevant processes. In our coupling concept we consider the time-dependent occurrence and significance of multi-phase flow, mechanical effects and geochemical reactions. Our numerical simulations for the pilot site Ketzin demonstrate that mechanical reservoir, caprock and fault integrity are maintained during the time of operation and that after 10,000 years CO 2 dissolution is the dominating trapping mechanism and mineralization occurs on the order of 10% to 25% with negligible changes to porosity and permeability.

Impact of DMO Processing on 3D Seismic Imaging at Ketzin, Germany

The goal of the dip-moveout correction (DMO) is to eliminate velocity bias when stacking. DMO processing is tested in order to account for variable dips at the Ketzin CO2 storage pilot site. In this study, 3D Squeezing DMO is applied to seismic data to study the impact of DMO on seismic imaging and to investigate if it enhances the CO2 seismic monitoring technique. We compare the data with and without DMO processing by utilizing quantitative and qualitative analysis. Our results indicate its effectiveness with applications to the 3D seismic data at the Ketzin site.

Corrigendum to Four years of Experience with a Permanent Seismic Monitoring Array at the Ketzin CO2 Storage Pilot Site

The authors regret that Figure 4 of their paper contains a serious error.It appears that the annotations in this figure have been vertically shifted when exchanging our final version of the paper. The annotations within this figure probably were ungrouped upon exchange. In the published version the red arrows in Figs. 4a-d are positioned too low, and in Fig. 4d the horizontal lines (both the green solid and blue dashed ones) are positioned too low as well. In addition, the text annotation along the horizontal axis in Fig. 4a is missing. This may lead to serious confusion upon the reader, since the interpretation of the seismic reflectors as described in the text of the paper, a crucial element of the described study, is not consistent with the figure annotations anymore. Please note that in this new figure I additionally included annotations (trace numbers) along the horizontal axis of Figure 4a.

The use of tracers to assess drill-mud penetration depth into sandstone cores during deep drilling: method development and application

For the utilization of deep saline aquifers in the frame of geotechnical use, such as geological sequestration of CO2, H2 or energy storage, a baseline characterization of pristine reservoir rock cores is required to monitor changes in the indigenous microbial communities and pore fluids, and to study alterations in rock characteristics resulting from interaction with geological storage technologies. However, drilling procedures and technical fluids, particularly drill mud, are sources of core contamination. To measure the penetration of drill mud into the cores, three tracers (fluorescein, microspheres, and 4′,6-diamidino-2-phenylindole stained bacteria) were tested under laboratory conditions. The flow of drill mud into core samples was induced by applying uniaxial pressure differentials to the core, and the penetration depth was microscopically determined for each tracer. Fluorescein was extracted from the rock samples and quantified fluorometrically. The results indicate that all tested tracers are suitable for tracking drill-mud penetration. The actual penetration depth seems to be related to differences in mineral composition and texture as well as microfractures. Among all tested tracers, fluorescein labelling is the simplest, cheapest and most accurate method for analyzing the contamination of rock cores by technical fluids. The application of this tracer was successfully applied during two deep drilling campaigns at the CO2 storage pilot site in Ketzin, Germany. The results highlight that the use of tracers is indispensable to ensure the quality of core samples for microbiological and biogeochemical analysis.

Injection operation and operational pressure–temperature monitoring at the CO2 storage pilot site Ketzin, Germany—Design, results, recommendations

The Ketzin pilot site for geological storage of CO2 in the German Federal State of Brandenburg about 25km west of Berlin is the only German CO2 storage site and has been the first European pilot site for on-shore storage of CO2 in saline aquifers. Continuous injection of CO2 started on June 30th, 2008, and a total of 61,396t of CO2 have been injected by September 2012. The injected CO2 was predominantly food-grade with a purity>99.9%, only from May to June 2011, 1515tCO2 from the Schwarze Pumpe oxyfuel pilot plant with a purity of >99.7% have been injected. The injection is accompanied by a comprehensive operational monitoring program. The program includes continuous measurements of flow rate, fill levels of intermediate storage tanks 1 and 2, outlet pressure and temperature for the injection plant, wellhead pressures (WHP) and casing pressures 1 and 2 for all wells, bottom hole pressure (BHP), bottom hole temperature (BHT) and distributed temperature sensing (DTS) along the injection tubing for the injection well Ktzi 201, BHP for the two observation wells Ktzi 202 (from March 2010 to October 2011) and Ktzi 200 (since October 2011), and above-zone pressure monitoring in shallow observation well P300. This operational pressure–temperature monitoring successfully ensured and proved a safe, smooth and reliable injection operation. A vital part of the operational P–T data comes from the downhole P–T measurements, which are recommended for any CO2 storage site. Without this downhole information, it would not have been possible to provide the complete picture of CO2 injection. The recommended downhole installation design of P–T tools distinguishes CO2 storage from the operational engineering of underground storage of natural gas, where BHP monitoring can be done via WHP recording. The DTS safety monitoring along the injection tubing supported typical operational processes as conditioning of the CO2 and improvement of injection rate and injection temperature and will be beneficial to any CO2 storage project. The above-zone pressure monitoring gives no hints to any hydraulic connection or CO2 leakage through or failure of the cap rock.

Time-lapse analysis of sparse 3D seismic data from the CO2 storage pilot site at Ketzin, Germany

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.