Papers by Mikael Erlström
Scientific core drilling of the Lower Palaeozoic succession in the Swedish sector of the Baltic Sea – investigation of the CO2 storage potential
Passive seismic imaging for CO2 geological storage in the Sudret area of Gotland, Sweden
Enigmatic sphaeromorph mass occurrences associated with the end-Triassic event in the Danish Basin
Abstract The end-Triassic mass extinction event is estimated to have caused the disappearance of ... more Abstract The end-Triassic mass extinction event is estimated to have caused the disappearance of several marine families (23%) and genera (50%) on a global scale (Hallam and Wignall, 1999; van de Schootbrugge et al. 2007). In the terrestrial realm ...
Physical- and geochemical properties of core samples from the Swedish part of the southern Baltic Sea: Implications for CO2 storage
EGU General Assembly Conference Abstracts, Apr 1, 2016

Distribution and characteristics of glaciokarst on the island of Gotland, Baltic Sea - its role on groundwater recharge and sensitive wetland ecosystems
Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and... more Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and limestone pavements are the most common karst features. Although, less well documented, caves and subsurface channels also contribute to the complex hydrogeology in the bedrock. The karst is interpreted to have been formed, primarily, before the Pleistocene when the landscape was covered with acidic organic soils. Glacial erosion and postglacial karstification have also played significant roles in sculpturing the epikarst morphology we see today. The study presents quantitative and qualitative characterization of karst within several pilot areas on the island of Gotland. High resolution aerial photographs were acquired over the pilot areas using a drone. These images were then analysed in GIS-software to provide a statistical evaluation of length, width, and relative area with karst. As well as providing a statistical understanding of the occurrence and geometry of karst, the results also help to clarify the impact of karst on the sensitive and limited groundwater resources on Gotland. Since a large part of the carbonate bedrock surface is barren or covered by thin quaternary deposits the epikarst provides important pathways for the percolation of meteoric water and recharge to the groundwater. It also locally provides guided pathways for surface runoff. Furthermore, the study demonstrates that the presence of karst often is in conjunction with sensitive ecosystems such as temporary wetlands. Extensive development of grikes and limestone pavements also provide conditions for periodically hanging aquifers, which not only promotes groundwater recharge but also the formation of unique habitats for a variety of often threatened ecosystems. This study, which includes both biologists and earth scientists highlights the importance of the identification of catchment areas and mapping of karst. It also emphasises that investigations into the hydrogeology (including aspects such as groundwater recharge, surface runoff and subsurface transport pathways) is essential for a better understanding of wetland dynamics and their protection. The presence of karst and spreading of contaminations in the ground is also discussed. The work summarizes early results from a collaboration between authorities working with Natura 2000 karst habitats and geological classification and mapping of karst.
Characterization of the Lower Cambrian sandstone aquifer in the Swedish Baltic Sea area - assessment regarding its potential suitability for storage of CO2
EGUGA, Apr 1, 2012

Tectonophysics, Apr 1, 2016
We present five interpreted regional seismic profiles, describing the full sedimentary sequence a... more We present five interpreted regional seismic profiles, describing the full sedimentary sequence across the Swedish sector of the Baltic Sea. The data for the study are part of an extensive and largely unpublished 2D seismic dataset acquired between 1970 and 1990 by the Swedish Oil Prospecting Company (OPAB). The Baltic Basin is an intracratonic basin located in northern Europe. Most of the Swedish sector of the basin constitutes the NW flank of a broad synclinal depression, the Baltic Basin. In the SW of the Swedish sector lies the Hanö Bay Basin, formed by subsidence associated with inversion of the Tornquist Zone during the Late Cretaceous. The geological history presented here is broadly consistent with previously published works. We observe an area between the Hanö Bay and the Baltic Basin where the Palaeozoic strata has been affected by transpression and subsequent inversion, associated with the Tornquist Zone during the late Carboniferous-Early Permian and Late Cretaceous, respectively. We propose that the Christiansø High was a structural low during the Late Jurassic, which was later inverted in the Late Cretaceous. We suggest that a fan shaped feature in the seismic data, adjacent to the Christiansø Fault within the Hanö Bay Basin, represents rapidly deposited, coarse-grained sediments eroded from the inverted Christiansø High during the Late Cretaceous. We identify a number of faults within the deeper part of the Baltic Basin, which we also interpret to be transpressional in nature, formed during the Caledonian Orogeny in the Late Silurian-Early Devonian. East of Gotland a number of sedimentary structures consisting of Silurian carbonate reefs and Ordovician carbonate mounds, as well as a large Quaternary glacial feature are observed. Finally, we use the seismic interpretation to infer the structural and stratigraphic history of the Baltic and Hanö Bay basins within the Swedish sector.
Zenodo (CERN European Organization for Nuclear Research), Dec 15, 2022

Mapping Bedrock Layering, Fault Zones and Saline Groundwater by Airborne TEM on the Island of Gotland, Sweden
Proceedings, Sep 6, 2015
An airborne transient electromagnetic survey (ATEM) was carried out over four areas on the island... more An airborne transient electromagnetic survey (ATEM) was carried out over four areas on the island of Gotland, Sweden, for groundwater planning purposes. The primary aim of the study was to locate areas with large groundwater capacity and to identify the depth to saline groundwater. The result from the ATEM survey indicates several sites and areas, which have been assessed as favourable for groundwater extraction. The data also reveal new and previously unknown information regarding the layering and structure of the subsurface geology down to approximately 200 m depth. An example from one of the surveyed areas shows that both the thickness of the upper limestone unit as well as the interface to the underlying marlstone and depth to saline groundwater is effectively mapped by the ATEM survey. In the second example a fault zone is clearly visualized, possibly also associated with increased groundwater circulation in a zone with fractured rock.
Chalk Structure Maps of the Central and Eastern North Sea

Geothermal Energy, Aug 6, 2021
The 3.1-and 3.7-km-deep FFC-1 and DGE-1 geothermal explorations wells drilled into the Precambria... more The 3.1-and 3.7-km-deep FFC-1 and DGE-1 geothermal explorations wells drilled into the Precambrian crystalline basement on the southern margin of the Fennoscandian Shield are evaluated regarding experiences from drilling, geological conditions, and thermal properties. Both wells penetrate an approximately 2-km-thick succession of sedimentary strata before entering the crystalline basement, dominated by orthogneiss, metabasite and amphibolite of the (1.1-0.9 Ga) Eastern Interior Sveconorwegian Province. The upper c. 400 m of the basement is in FFC-1 severely fractured and water-bearing which disqualified the use of percussion air drilling and conventional rotary drilling was, therefore, performed for the rest of the borehole. The evaluation of the rotary drillings in FFC-1 and DGE-1 showed that the average bit life was very similar, 62 m and 68 m, respectively. Similarly, the average ROP varied between 2 and 4 m/h without any preferences regarding bit-type (PDC or TCI) or geology. A bottomhole temperature of 84.1 °C was measured in FFC-1 borehole with gradients varying between 17.4 and 23.5 °C/km for the main part of the borehole. The calculated heat flow varies between 51 and 66 mW/m 2 and the average heat production is 3.0 µW/m 3. The basement in FFC-1 is, overall, depleted in uranium and thorium in comparison to DGE-1 where the heat productivity is overall higher with an average of 5.8 µW/m 3. The spatial distribution of fractures was successfully mapped using borehole imaging logs in FFC-1 and shows a dominance of N-S oriented open fractures, a fracture frequency varying between 0.85 and 2.49 frac/m and a fracture volumetric density between 1.68 and 3.39 m 2 /m 3. The evaluation of the two boreholes provides insight and new empirical data on the thermal properties and fracturing of the concealed crystalline basement in the Fennoscandian Shield Border Zone that, previously, had only been assessed by assumptions and modelling. The outcome of the drilling operation has also provided insight regarding the drilling performance in the basement and statistical data on various drill bits used. The knowledge gained is important in feasibility studies of deep geothermal projects in the crystalline basement in south Sweden.
Calcined clays as supplementary cementitious materials: A feasibility study in Sweden

Distribution and characteristics of glaciokarst on the island of Gotland, Baltic Sea - its role on groundwater recharge and sensitive wetland ecosystems
Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and... more Glaciokarst is widespread in the Silurian carbonate bedrock on the Island of Gotland. Grikes and limestone pavements are the most common karst features. Although, less well documented, caves and subsurface channels also contribute to the complex hydrogeology in the bedrock. The karst is interpreted to have been formed, primarily, before the Pleistocene when the landscape was covered with acidic organic soils. Glacial erosion and postglacial karstification have also played significant roles in sculpturing the epikarst morphology we see today. The study presents quantitative and qualitative characterization of karst within several pilot areas on the island of Gotland. High resolution aerial photographs were acquired over the pilot areas using a drone. These images were then analysed in GIS-software to provide a statistical evaluation of length, width, and relative area with karst. As well as providing a statistical understanding of the occurrence and geometry of karst, the results al...
Hydrogeological mapping of the island of Gotland, Sweden, using SkyTEM
AGU Fall Meeting Abstracts, Dec 1, 2016

An Integrated Formation Evaluation Approach Evaluated the Basement Temperature Anomaly
82nd EAGE Annual Conference & Exhibition, 2021
Summary A holistic formation evaluation approach to characterizing the naturally open fractures z... more Summary A holistic formation evaluation approach to characterizing the naturally open fractures zones explained the basement negative temperature anomaly occurrence. For this purpose, using measurements of high resolution dual slim imager, acoustic cross-dipole, density, photoelectric factor, spectral gamma ray and temperature, few formation evaluation techniques were applied, such as structural facies identification, fracture aperture calculation, sonic anisotropy, brittleness index magnitude and polarity, Stoneley fracture identification, which, coupled with mudlogging data offered a conprehensive understanding of the naturally occurring fractured zones over the thermal conductivity anomaly. The presence of fractured facies identified on borehole images, decrease of density values, the occurrence of sonic anisotropy, changes in the brittleness index polarity, increase of the fracture density, increase of the fracture aperture and the presence of Stoneley reflection chevrons were used as arguments of water influx through conjugated open natural fracture system which generated the negative thermal anomaly.

Bulletin of the Geological Society of Denmark, 2018
The Øresund Basin in the transnational area between Sweden and Denmark forms a marginal part of t... more The Øresund Basin in the transnational area between Sweden and Denmark forms a marginal part of the Danish Basin. The structural outline and stratigraphy of the Mesozoic succession is described, and a novel interpretation and description of the subsurface geology and geothermal potential in the North Sjælland Half-graben is presented. The subsurface bedrock in the basin includes several Mesozoic intervals with potential geothermal sandstone reservoirs. Parts of the succession fulfill specific geological requirements with regard to distribution, composition and quality of the sandstones. A characterisation of these is presently of great interest in the attempt to identify geothermal reservoirs suitable for district heating purposes. The results presented in this paper include for the first time a comprehensive description of the stratigraphic intervals as well as the characteristics of the potential Mesozoic geothermal reservoirs in the Øresund region, including their distribution, c...

Palaeogeography, Palaeoclimatology, Palaeoecology, 2019
Carbonate mud mounds developed within the Baltoscandian Basin, an epicratonic basin on the Baltic... more Carbonate mud mounds developed within the Baltoscandian Basin, an epicratonic basin on the Baltica palaeocontinent, during the Ordovician. In the Upper Ordovician succession of the Baltoscandian Basin, a large number of mud mounds are present at three stratigraphic levels namely, the Kullsbergs mounds (late Sandbianearly Katian), Nabala and Rakvere mounds (middle Katian), and the Boda mounds (late Katian). These formed in a subtropical-tropical carbonate platform environment, covered by a shallow epicontinental sea. The mud mounds at these stratigraphic levels beneath and around Gotland have been characterized using a comprehensive seismic and well dataset acquired during a period of hydrocarbon exploration and exploitation which began more than 30 years ago. Interpretation of the largely unpublished seismic data in this study provides details on the distribution of mound complexes in the basin and constraints on the geometry of the mounds. Detailed structure contour maps of the top and the base of the Ordovician succession beneath Gotland based on the seismic interpretation are presented. The results give a comprehensive characterization of carbonate mud mound generation on Gotland which may help in understanding the distribution patterns of similar mound complexes in other parts of the Ordovician world formed in similar environments.
Characterization of the Lower Cambrian sandstone aquifer in the Swedish Baltic Sea area - assessment regarding its potential suitability for storage of CO2

Tectonophysics, 2016
We present five interpreted regional seismic profiles, describing the full sedimentary sequence a... more We present five interpreted regional seismic profiles, describing the full sedimentary sequence across the Swedish sector of the Baltic Sea. The data for the study are part of an extensive and largely unpublished 2D seismic dataset acquired between 1970 and 1990 by the Swedish Oil Prospecting Company (OPAB). The Baltic Basin is an intracratonic basin located in northern Europe. Most of the Swedish sector of the basin constitutes the NW flank of a broad synclinal depression, the Baltic Basin. In the SW of the Swedish sector lies the Hanö Bay Basin, formed by subsidence associated with inversion of the Tornquist Zone during the Late Cretaceous. The geological history presented here is broadly consistent with previously published works. We observe an area between the Hanö Bay and the Baltic Basin where the Palaeozoic strata has been affected by transpression and subsequent inversion, associated with the Tornquist Zone during the late Carboniferous-Early Permian and Late Cretaceous, respectively. We propose that the Christiansø High was a structural low during the Late Jurassic, which was later inverted in the Late Cretaceous. We suggest that a fan shaped feature in the seismic data, adjacent to the Christiansø Fault within the Hanö Bay Basin, represents rapidly deposited, coarse-grained sediments eroded from the inverted Christiansø High during the Late Cretaceous. We identify a number of faults within the deeper part of the Baltic Basin, which we also interpret to be transpressional in nature, formed during the Caledonian Orogeny in the Late Silurian-Early Devonian. East of Gotland a number of sedimentary structures consisting of Silurian carbonate reefs and Ordovician carbonate mounds, as well as a large Quaternary glacial feature are observed. Finally, we use the seismic interpretation to infer the structural and stratigraphic history of the Baltic and Hanö Bay basins within the Swedish sector.
Erratum to “The late Rhaetian transgression in southern Sweden: Regional (and global) recognition and relation to the Triassic–Jurassic boundary” [Palaeogeography, Palaeoclimatology, Palaeoecology 241/3–4 (2006) 339–372]
Palaeogeography, Palaeoclimatology, Palaeoecology, 2007
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Papers by Mikael Erlström