The injection of CO₂at the Ketzin pilot CO₂storage site started in June 2008 and ended in August 2013. During the 62 months of injection, a total amount of about 67 kt of CO₂was injected into a saline aquifer. A third repeat three‐dimensional 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 west–northwest migration of the gaseous CO₂plume 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 CO₂plume 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 CO₂plume distribution suggests that the decrease in the size of the anomaly may be due to multiple factors, such as limited vertical resolution, CO₂dissolution, and CO₂migration into thin layers, in addition to the effects of ambient noise. Four‐dimensional seismic modelling based on dynamic flow simulations indicates that a dynamic balance between the newly injected CO₂after the second repeat survey and the CO₂migrating into thin layers and being dissolved was reached by the time of the first post‐injection survey. In view of the significant uncertainties in CO₂mass estimation, both patchy and non‐patchy saturation models for the Ketzin site were taken into consideration.

Archives across the world contain vast amounts of old or “vintage” seismic reflection data, which are largely inaccessible for geo-scientific research, due to the out-dated media on which they are stored. Despite the age of these data, they often have great potential to be of use in modern day research. It is often the case that seismic reflection data within these archives are only available as a processed stacked section, printed on paper or film. In this study, a method for the conversion (vectorization) of scanned images of stacked reflection seismic data to standard SEG-Y format is presented. The method addresses data displayed with a line denoting the waveform, where areas on one side of the baseline are shaded (i.e. wiggle trace, variable fill). The method provides an improvement on other published methods utilized within currently available academic software. Unlike previous studies, the method used to detect trace baselines and to detect and remove timelines on the seismic image is described in detail. Furthermore, a quantitative analysis of the performance of the method is presented, showing that an average trace-to-trace correlation coefficient of between 0.8 and 0.95 can be achieved for typical plotting styles. Finally, a case study where the method is applied to vectorize over 1700 km of land seismic data from the island of Gotland (Sweden) is presented.

Wind energy is an important field of development for the island of Gotland, Sweden, especially since the island has set targets to generate 100% of its energy from renewable sources by 2025. Due to the variability of wind conditions, energy storage will be an important technology to facilitate the continued development of wind energy on Gotland and ensure a stable and secure supply of electricity. In this study, the feasibility of utilizing the Middle Cambrian Faludden sandstone reservoir on Gotland for Compressed Air Energy Storage (CAES) is assessed. Firstly, a characterization of the sandstone beneath Gotland is presented, which includes detailed maps of reservoir thickness and top reservoir structure. Analysis of this information shows that the properties of the Faludden sandstone and associated cap rock appear favorable for the application of CAES. Seven structural closures are identified below the eastern and southern parts of Gotland, which could potentially be utilized for CAES. Scoping estimates of the energy storage capacity and flow rate for these closures within the Faludden sandstone show that industrial scale CAES could be possible on Gotland.

This work analyses six high-resolution multi-channel seismic profiles across the Klints Bank east of Gotland. The Klints Bank consists of a drop-shaped increase of the Quaternary thickness and is oriented in an approximately north-southern direction with a length of over 50 km, a width of about 15 km and a maximum thickness of 150 m. The glacial origin of the Klints Bank can be verified with the dataset presented in this study. We classify the feature as a (giant) drumlin due to its steep up-ice and tapered down-ice face in combination with an orientation parallel to the ice-flow direction of the Weichselian glaciation. The seismic image of the internal structure of the Quaternary unit shows no uniform stratification or deformation patterns; instead, local sub-parallel reflection patterns interlayered with transparent units are observed. The averaged seismic velocity of this unit is about 2000 m/s, which is interpreted as an autochthonous deposition of glaciogenic sediments. Signs of overprinting are interpreted based on the geometry of the flanks of the structure, which appear mostly in the form of collapse structures and lifted blocks due to compressional thrust faulting. Phase-reversed events within and beneath the Quaternary are perceived as strong evidence of fluid (hydrocarbon) presence within the Klints Bank. Organically enriched Palaeozoic shales in south-easterly direction of the Klints Bank presumably give the origin of these thermogenic hydrocarbons.

Assessing the optimal placement and design of a large-scale high temperature energy storage system in crystalline bedrock is a challenging task. This study applies and evaluates various methods and strategies for pre-site investigation for a potential high temperature borehole thermal energy storage (HT-BTES) system at Linköping in Sweden. The storage is required to shift approximately 70 GWh of excess heat generated from a waste incineration plant during the summer to the winter season. Ideally, the site for the HT-BTES system should be able to accommodate up to 1400 wells to 300 m depth. The presence of major fracture zones, high groundwater flow, anisotropic thermal properties, and thick Quaternary overburden are all factors that play an important role in the performance of an HT-BTES system. Inadequate input data to the modeling and design increases the risk of unsatisfactory performance, unwanted thermal impact on the surroundings, and suboptimal placement of the HT-BTES system, especially in a complex crystalline bedrock setting. Hence, it is crucial that the subsurface geological conditions and associated thermal properties are suitably characterized as part of pre-investigation work. In this study, we utilize a range of methods for pre-site investigation in the greater Distorp area, in the vicinity of Linköping. Ground geophysical methods, including magnetic and Very Low-Frequency (VLF) measurements, are collected across the study area together with outcrop observations and lab analysis on rock samples. Borehole investigations are conducted, including Thermal Response Test (TRT) and Distributed Thermal Response Test (DTRT) measurements, as well as geophysical wireline logging. Drone-based photogrammetry is also applied to characterize the fracture distribution and orientation in outcrops. In the case of the Distorp site, these methods have proven to give useful information to optimize the placement of the HT-BTES system and to inform design and modeling work. Furthermore, many of the methods applied in the study have proven to require only a fraction of the resources required to drill a single well, and hence, can be considered relatively efficient.

Carbon capture and storage (CCS) is a strategy that can be employed to reducing human impact on climate change In the 21st century. Geological storage has been currently considered the most promising strategy. It is reported that there is a large theoretical capacity to store CO2 in the Precambrian sedimentary succession of the Baltic Basin. To aid in surveying and evaluating the potential storage reservoirs in the Baltic Sea, a seismic survey was performed over similar geology in the Sudret area of Gotland. Part of the survey consisted of 14-hours passive data, recorded along a 2.8 km profile with 10m receiver spacing and 1ms sample rate using 329 5Hz SmartSolo nodal units in the vicinity of two boreholes that had been drilled earlier. We retrieved body wave and surface wave virtual shot gathers after applying signal separation and cross correlation calculations. For the body waves, conventional seismic data processing was conducted to obtain a stacked profile; for the surface waves, we could determine the dispersion curve in the frequency range 0.5 to 5.5 Hz and inverted these curves to obtain a velocity model from the ground surface down to c. 1500m depth. Both the body waves and surface waves provide a high quality and high resolution image of the top of the Ordovician formation and have a good consistency with active seismic data in the same location. Moreover, they revealed some reliable deep geological information which active data cannot provide because of the limited source energy. Compared with active seismic exploration, passive seismic is friendly to the environment and cost effective. In some cases, it is an important complementary or alternative method to active seismic for CO2 storage and monitoring.