Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden
This study contributes to geothermal exploration in 1660–1520 Ma old, reworked bedrock in Sweden. Our primary objectives are to constrain the orientation of horizontal stresses, and to discuss implications for geothermal exploration. High-resolution acoustic televiewer image data reveal the downhole...
Published in: | Geological Society, London, Special Publications |
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Online Access: | https://gfzpublic.gfz-potsdam.de/pubman/item/item_5025917 |
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ftgfzpotsdam:oai:gfzpublic.gfz-potsdam.de:item_5025917 2024-06-23T07:52:43+00:00 Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden Ask, M. Pierdominici, S. Rosberg, J. 2024 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5025917 unknown info:eu-repo/semantics/altIdentifier/doi/10.1144/SP546-2023-36 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5025917 Characterization, Prediction and Modelling of Crustal Present-Day In-Situ Stresses Geological Society special publication info:eu-repo/semantics/bookPart 2024 ftgfzpotsdam https://doi.org/10.1144/SP546-2023-36 2024-06-05T00:58:20Z This study contributes to geothermal exploration in 1660–1520 Ma old, reworked bedrock in Sweden. Our primary objectives are to constrain the orientation of horizontal stresses, and to discuss implications for geothermal exploration. High-resolution acoustic televiewer image data reveal the downhole distribution of stress indicators (borehole breakouts, drilling-induced fractures and petal centreline fractures) and pre-existing structures (natural fractures, foliation). About 135 m of stress indicators are measured from 0.2–1.0 km. The results suggest a uniform NNW–SSE mean maximum horizontal stress orientation. A total of 1525 pre-existing structures (natural fractures, foliation) are mapped in borehole GE-1. The prevailing stress regime controls whether natural fractures and foliation are well-oriented for stimulation. For strike-slip and normal faulting stress regimes, well-oriented fractures steeply dip towards the WSW. For a reverse faulting stress regime, shallow dipping fractures are well-oriented for stimulation. The downhole distribution of stress indicators and other stress measurements in the region and other parts of Fennoscandia tentatively suggest a strike-slip stress regime, but additional studies are needed to constrain the complete stress field at study depth and towards engineered geothermal systems reservoir target depths. Our secondary objective is to highlight that interpretation of high-resolution acoustic data, particularly in metamorphic crystalline rocks, is subjective and that more guidelines for data interpretation are needed. The interactive interpretation of the images is based on visual analyses of complex pre-existing structures and stress indicators with highly variable shapes. The application of three methods for data analyses in the GE-1 borehole proposes that drilling-induced fractures are little influenced by the method applied. Interpretations on individual borehole breakout azimuths may, however, result in over 10° differences in orientation. Book Part Fennoscandia GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) Geological Society, London, Special Publications 546 1 |
institution |
Open Polar |
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GFZpublic (German Research Centre for Geosciences, Helmholtz-Zentrum Potsdam) |
op_collection_id |
ftgfzpotsdam |
language |
unknown |
description |
This study contributes to geothermal exploration in 1660–1520 Ma old, reworked bedrock in Sweden. Our primary objectives are to constrain the orientation of horizontal stresses, and to discuss implications for geothermal exploration. High-resolution acoustic televiewer image data reveal the downhole distribution of stress indicators (borehole breakouts, drilling-induced fractures and petal centreline fractures) and pre-existing structures (natural fractures, foliation). About 135 m of stress indicators are measured from 0.2–1.0 km. The results suggest a uniform NNW–SSE mean maximum horizontal stress orientation. A total of 1525 pre-existing structures (natural fractures, foliation) are mapped in borehole GE-1. The prevailing stress regime controls whether natural fractures and foliation are well-oriented for stimulation. For strike-slip and normal faulting stress regimes, well-oriented fractures steeply dip towards the WSW. For a reverse faulting stress regime, shallow dipping fractures are well-oriented for stimulation. The downhole distribution of stress indicators and other stress measurements in the region and other parts of Fennoscandia tentatively suggest a strike-slip stress regime, but additional studies are needed to constrain the complete stress field at study depth and towards engineered geothermal systems reservoir target depths. Our secondary objective is to highlight that interpretation of high-resolution acoustic data, particularly in metamorphic crystalline rocks, is subjective and that more guidelines for data interpretation are needed. The interactive interpretation of the images is based on visual analyses of complex pre-existing structures and stress indicators with highly variable shapes. The application of three methods for data analyses in the GE-1 borehole proposes that drilling-induced fractures are little influenced by the method applied. Interpretations on individual borehole breakout azimuths may, however, result in over 10° differences in orientation. |
format |
Book Part |
author |
Ask, M. Pierdominici, S. Rosberg, J. |
spellingShingle |
Ask, M. Pierdominici, S. Rosberg, J. Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
author_facet |
Ask, M. Pierdominici, S. Rosberg, J. |
author_sort |
Ask, M. |
title |
Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
title_short |
Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
title_full |
Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
title_fullStr |
Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
title_full_unstemmed |
Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden |
title_sort |
image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in gothenburg borehole ge-1, sw sweden |
publishDate |
2024 |
url |
https://gfzpublic.gfz-potsdam.de/pubman/item/item_5025917 |
genre |
Fennoscandia |
genre_facet |
Fennoscandia |
op_source |
Characterization, Prediction and Modelling of Crustal Present-Day In-Situ Stresses Geological Society special publication |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1144/SP546-2023-36 https://gfzpublic.gfz-potsdam.de/pubman/item/item_5025917 |
op_doi |
https://doi.org/10.1144/SP546-2023-36 |
container_title |
Geological Society, London, Special Publications |
container_volume |
546 |
container_issue |
1 |
_version_ |
1802644091555545088 |