| 1. |
- Ask, Maria, et al.
(författare)
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Image analysis of acoustic data and interpretation of rock stress orientations for geothermal exploration in Gothenburg borehole GE-1, SW Sweden
- 2024
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Ingår i: Geological Society Special Publication. - 0305-8719. ; 546:1, s. 69-91
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Ask, Maria, et al.
(författare)
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Proposed Drilling into Postglacial Faults : The Pärvie Fault System
- 2021
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Ingår i: Glacially-Triggered Faulting. - Cambridge : Cambridge University Press. - 9781108779906 - 9781108490023 ; , s. 151-174
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Bokkapitel (refereegranskat)abstract
- Postglacial faults in northern Fennoscandia have been investigated through geophysical methods, trenching, and mapping of brittle deformation structures. Very little is known about postglacial faults through direct measurements. A few short, up to 500 m deep, boreholes exist. Plans for a scientific drilling program were initiated in 2010. The drilling target has been identified: The Pärvie Fault system is the longest known postglacial fault in the world and has been proposed to have hosted an M8 earthquake near the end or just after the last glaciation. Further, this fault system is still microseismically active. The drill sites are north of the Arctic Circle, in a sparsely populated area. Existing site survey data, established logistics, and societal relevance through the fault’s proximity to mining and energy operations make this fault system an appropriate target. The International Continental Scientific Drilling Program approved a full drilling proposal in October 2019. This chapter presents an abbreviated version of the approved proposal.
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| 3. |
- Chirindja, Farisse, et al.
(författare)
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Borehole logging and slug tests for evaluating the applicability of electrical resistivity tomography for groundwater exploration in Nampula complex, Mozambique
- 2017
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 9:2
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Tidskriftsartikel (refereegranskat)abstract
- In Nampula province, Mozambique, there is a high number of water wells considered as having failed for having too low a pumping yield. Two Electrical Resistivity Tomography (ERT) measurement campaigns were conducted in the area for evaluating the reasons of failures. However, in some cases it was difficult to verify and interpret the ERT results by only using the inadequate lithological description presented in drilling reports. In this paper the integration of borehole logging and slug testing is presented as a solution to add more information and to enhance the interpretation of ERT models. The borehole logging tool measured resistivity, magnetic susceptibility and natural gamma. The logging results proved that the ERT models are accurate in estimating the resistivity for basement (>1400 Ωm), fractured layer (220-1400 Ωm), semi-weathered layer with clay accumulation (10-220 Ωm), and weathered and leached layer (220-2700 Wm). The slug testing gave results of high hydraulic conductivity (K) values where the ERT indicates well-developed weathered and fractured layers, and low K values where these are less developed. The borehole interpretation can be extrapolated using the ERT model to give a geometric characterization of the aquifer. Therefore, the implementation of the ERT method in groundwater exploration is encouraged.
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| 4. |
- Doughty, Christine, et al.
(författare)
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Flowing fluid electrical conductivity logging of a deep borehole during and following drilling : estimation of transmissivity, water salinity and hydraulic head of conductive zones
- 2017
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Ingår i: Hydrogeology Journal. - : SPRINGER. - 1431-2174 .- 1435-0157. ; 25:2, s. 501-517
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Tidskriftsartikel (refereegranskat)abstract
- Flowing fluid electrical conductivity (FFEC) logging is a hydrogeologic testing method that is usually conducted in an existing borehole. However, for the 2,500-m deep COSC-1 borehole, drilled at re, central Sweden, it was done within the drilling period during a scheduled 1-day break, thus having a negligible impact on the drilling schedule, yet providing important information on depths of hydraulically conductive zones and their transmissivities and salinities. This paper presents a reanalysis of this set of data together with a new FFEC logging data set obtained soon after drilling was completed, also over a period of 1 day, but with a different pumping rate and water-level drawdown. Their joint analysis not only results in better estimates of transmissivity and salinity in the conducting fractures intercepted by the borehole, but also yields the hydraulic head values of these fractures, an important piece of information for the understanding of hydraulic structure of the subsurface. Two additional FFEC logging tests were done about 1 year later, and are used to confirm and refine this analysis. Results show that from 250 to 2,000 m depths, there are seven distinct hydraulically conductive zones with different hydraulic heads and low transmissivity values. For the final test, conducted with a much smaller water-level drawdown, inflow ceased from some of the conductive zones, confirming that their hydraulic heads are below the hydraulic head measured in the wellbore under non-pumped conditions. The challenges accompanying 1-day FFEC logging are summarized, along with lessons learned in addressing them.
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| 5. |
- Gómez, Etzar, et al.
(författare)
-
Alluvial aquifer thickness and bedrock structure delineation by electromagnetic methods in the highlands of Bolivia
- 2019
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Ingår i: Environmental Earth Sciences. - : Springer Science and Business Media LLC. - 1866-6280 .- 1866-6299. ; 78:3
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Tidskriftsartikel (refereegranskat)abstract
- The porous aquifers in the area called Challapampa are the most important groundwater reservoirs that supply drinking water to Oruro city in the highlands of Bolivia. They consist of unconsolidated fluvial–lacustrine deposits, resting on a complex sedimentary bedrock and covered by a thin surficial clay layer. The settings of these geological units and the structures governing the flow patterns have barely been investigated, despite this reservoir having been utilized during the last 50 years. This study applied transient electromagnetic (TEM) soundings and electrical resistivity tomography (ERT) in the middle part of the alluvial fan of River Paria to investigate the thickness of the porous aquifer and detect the relief of the bedrock. Likewise, some results expressed as resistivity models indicate the possible existence of geological structures below the unconsolidated sediments. The average depth of investigation reached in this study is between 200 and 250 m below the surface, for both the applied methods. The geological structures inferred have similar directions as the major faults in the vicinity, from southeast to northwest, which in turn are assumed as part of fractured aquifers underlying the porous aquifers. The geo-electrical techniques were successfully tested in the study area and the resistivity models from TEM complement very well those obtained from ERT. Therefore, extended investigations using the same techniques would help to develop a more complete description of the hydrogeological settings of the aquifer system.
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| 6. |
- Gómez, Etzar, et al.
(författare)
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Tracking of geological structures and detection of hydrothermal intrusion by geo-electrical methods in the highlands of Bolivia
- 2019
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Ingår i: Journal of South American Earth Sciences. - : Elsevier BV. - 0895-9811. ; 91, s. 214-226
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Tidskriftsartikel (refereegranskat)abstract
- Oruro city in the Bolivian highlands depends solely on groundwater to supply domestic consumption and irrigation. The top porous aquifer currently exploited is not fully understood in aspects like geometry, hydrogeological properties and interaction with other aquifers in the region. Recent studies detected traces of fractures in the bedrock beneath the porous aquifer; these geological structures seem to be part of a fractured aquifer in contact with thermal sources. The present study aims to fill the gap between those recently detected fractures and the well-mapped fault system to the east of the study area and identify hydrothermal flows by using geo-electrical methods like Electrical Resistivity Tomography and Transient Electromagnetic soundings. Thirteen tomographic lines, placed transversely to the direction of three main faults, were meant to identify prolongations of those structures by tracking distinctive low resistivity in sectors where saline water saturates the subsoil. This type of water is also present in some hot springs near Capachos, where hydrothermal flows discharge under artesian conditions. Two of the investigated faults seem extending to the northwest, in agreement with the expected linkage towards the recently detected fractures. These two faults appear to reach a volcanic formation since the hydrothermal flows, going mainly upwards, align with their strikes. The remaining fault seems not to be connected to any hydrothermal source. The study presents new information, data and interpretations intending to improve the knowledge about the geological structures in a sensitive part of the local aquifer system.
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| 7. |
- Gomez Lopez, Etzar, et al.
(författare)
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Groundwater Origins and Circulation Patterns Based on Isotopes in Challapampa Aquifer, Bolivia
- 2016
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 8:5
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Tidskriftsartikel (refereegranskat)abstract
- Aridity and seasonality of precipitation are characteristics of the highland region in Bolivia. Groundwater becomes an important and safe source of water when surficial bodies are intermittent and affected by natural and anthropogenic contamination. Decades of exploitation of the Challapampa aquifer, combined with lack of information required to understand the groundwater circulation, represent a challenge for reservoir management. This study analyzes isotopic compositions of deuterium and oxygen-18 in different stages in the hydrologic cycle to assess flow patterns in the aquifer, especially in the alluvial fan of River Paria, where records are more extensive in space and time. Interpretations are based on existing and new data. Some implications, such as the age of water, the evaporation effect in groundwater and some thermal intrusions are supported by stable isotopes, tritium, radiocarbon, and electrical conductivity records. New results confirm that modern precipitation over the mountains surrounding the study area is the most important origin of water for shallow aquifers until exploited depths, 100 m below surface. The origin of water in deeper depths, 400 m, seems related to infiltration at higher altitudes and longer residence times.
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| 8. |
- Gomez Lopez, Etzar, et al.
(författare)
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Quantitative estimations of aquifer properties from resistivity in the Bolivian highlands
- 2019
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Ingår i: H2Open Journal. - : IWA Publishing. - 2616-6518. ; 2:1, s. 113-124
-
Tidskriftsartikel (refereegranskat)abstract
- Resistivity data constitute the largest part of the available information to assess the hydrogeological characteristics of the aquifer system near Oruro, in the central part of the Bolivian Altiplano. Two aquifers are part of this system; top unconsolidated sediments storing fresh water in their granular voids, overlying fractured hard rock formations where saline water was detected in connection to some faults. This study proposes an indirect and cost-effective way to estimate aquifer hydraulic properties for the groundwater management in the region. Hydraulic conductivity and transmissivity in the top aquifer were estimated using an empirical linear relationship between hydraulic conductivity and resistivity. This latter parameter, as well as the aquifer thickness, were obtained from the inverted models corresponding to the geoelectrical tests performed in the study area (electrical resistivity tomography, transient electromagnetic soundings and vertical electrical soundings). The highest estimated transmissivity values are ∼4.0 × 10−2 m2/s located in the centre of the study area, the lowest values are ∼3.4 × 10−3 m2/s, located around thermal intrusions to the south and where the top of the bedrock is shallow (∼20 m depth) to the west. The methodology presented in this study makes wider use of resistivity measurements to identify promising groundwater production sites.
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| 9. |
- Gonzales, Andrés, et al.
(författare)
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Electrical resistivity tomography and induced polarization for mapping the subsurface of alluvial fans : A case study in Punata (Bolivia)
- 2016
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Ingår i: Geosciences (Switzerland). - : MDPI AG. - 2076-3263. ; 6:4
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Tidskriftsartikel (refereegranskat)abstract
- Conceptual models of aquifer systems can be refined and complemented with geophysical data, and they can assist in understanding hydrogeological properties such as groundwater storage capacity. This research attempts to use geoelectrical methods, Electrical Resistivity Tomography and Induced Polarization parameters, for mapping the subsurface in alluvial fans and to demonstrate its applicability; the Punata alluvial fan was used as a case study. The resistivity measurements proved to be a good tool for mapping the subsurface in the fan, especially when used in combination with Induced Polarization parameters (i.e., Normalized Chargeability). The Punata alluvial fan characterization indicated that the top part of the subsurface is composed of boulders in a matrix of finer particles and that the grain size decreases with depth; the electrical resistivity of these deposits ranged from 200 to 1000 Ωm, while the values of normalized chargeability were lower than 0.05 mS/m. The bottom of the aquifer system consisted of a layer with high clay content, and the resistivity ranged from 10 to 100 Ωm, while the normalized chargeability is higher than 0.07 mS/m. With the integration of these results and lithological information, a refined conceptual model is proposed; this model gives a more detailed description of the local aquifer system. It can be concluded that geoelectrical methods are useful for mapping aquifer systems in alluvial fans.
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| 10. |
- Guglielmi, Yves, et al.
(författare)
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Crystalline Disposal R&D at LBNL : FY20 Progress Report
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Within the Spent Fuel & Waste Science and Technology (SFWST) Program, research work continues further with the goal to better understand long-term performance of disposal systems in three main geologic rock types: clay/shale, salt, and crystalline rock. This report documents LBNL’s research activities related to investigations of crystalline host rock according to the scope of two work packages: SF-20LB01030207 “Crystalline International Collaborations – LBNL,” and SF-20LB01030203 “Crystalline Disposal R&D – LBNL.” These research activities correspond are related to key Features, Events, and Processes (FEPs), ranked in importance from medium to high, as listed in Table 7 of the Used Fuel Disposition Campaign Disposal Research and Development Roadmap (FCR&D-USED-2011-000065 REV0) (Nutt, 2011). Specifically, these research activities address FEP 2.2.01, Excavation Disturbed Zone (EZD). The results of these research activities provide important insights into understanding and predicting flow and transport processes that could occur in low-permeability crystalline rocks, in which fractures might serve as main conduits for fluid flow and radionuclide transport. The evolution of the EDZ during the excavation of the tunnel as well as the evolution of microcrack growth within the EDZ after the emplacement of backfill are critical for predicting the long- term behavior of the EDZ. A number of factors including stress, temperature, water activity, capillary pressure, chemistry, and mineralogy can affect the rock evolution, which require advanced experimental tools to study it.
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| 11. |
- Hedin, Peter, 1981-, et al.
(författare)
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3D reflection seismic imaging at the 2.5 km deep COSC-1 scientific borehole, central Scandinavian Caledonides
- 2016
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Ingår i: Tectonophysics. - : Elsevier. - 0040-1951 .- 1879-3266. ; 689, s. 40-55
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Tidskriftsartikel (refereegranskat)abstract
- The 2.5 km deep scientific COSC-1 borehole (ICDP 5054-1-A) was successfully drilled with nearly complete core recovery during spring and summer of 2014. Downhole and on-core measurements through the targeted Lower Seve Nappe provide a comprehensive data set. An observed gradual increase in strain below 1700 m, with mica schists and intermittent mylonites increasing in frequency and thickness, is here interpreted as the basal thrust zone of the Lower Seve Nappe. This high strain zone was not fully penetrated at the total drilled depth and is thus greater than 800 m in thickness.To allow extrapolation of the results from downhole logging, core analysis and other experiments into the surrounding rock and to link these with the regional tectonic setting and evolution, three post-drilling high-resolution seismic experiments were conducted in and around the borehole. One of these, the first 3D seismic reflection land survey to target the nappe structures of the Scandinavian Caledonides, is presented here. It provides new information on the 3D geometry of structures both within the drilled Lower Seve Nappe and underlying rocks down to at least 9 km.The observed reflectivity correlates well with results from the core analysis and downhole logging, despite challenges in processing. Reflections from the uppermost part of the Lower Seve Nappe have limited lateral extent and varying dips, possibly related to mafic lenses or boudins of variable character within felsic rock. Reflections occurring within the high strain zone, however, are laterally continuous over distances of a kilometer or more and dip 10–15° towards the southeast. Reflections from structures beneath the high strain unit and the COSC-1 borehole can be followed through most of the seismic volume down to at least 9 km and have dips of varying degree, mainly in the east–west thrust direction of the orogen.
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| 12. |
- Juhlin, Christopher, 1956-, et al.
(författare)
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Seismic reflectivity, fracturing and stress field data from the FFC-1 exploratory geothermal project in SW Skåne, Sweden
- 2022
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Ingår i: Geothermics. - : Elsevier BV. - 0375-6505 .- 1879-3576. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- Enhanced geothermal systems (EGS) are a potential heat source in many parts of the world, even in locations where the temperature gradient is relatively low. We present here an integrated study of reflection seismic data, borehole logs and seismicity analysis performed in conjunction with a geothermal exploratory project operated by E.ON in Malmö, Sweden. In 2020, the pre-existing 2.1 km deep FFC-1 borehole through the sedimentary cover was deepened into the crystalline basement to about 3.1 km vertical depth. Combined interpretation of the reflection seismic data and geophysical wireline logs show that most of the reflectivity in the Precambrian basement is likely generated by lenses of mafic amphibolite embedded in a felsic gneissic matrix. The general structural bedding and foliation is gently dipping to sub-horizontal, similar to other locations in southwest Sweden. Fracture frequency is relatively high in the crystalline rock mass, with heavy fracturing in the uppermost part of the crystalline basement, obscuring a clear reflection from the top of the Precambrian. Highly fractured and hydraulically conductive intervals are also found between 2,562 and 2,695 m based on a temperature drop and the interpretation of the geophysical data. Open fractures, both natural and induced, have a clear N–S orientation, contrasting with the expected NW–SE direction based on the orientation of the Sorgenfrei-Tornquist Zone and earthquake fault plane solutions to the north. This difference may be partly explained by local variations in the stress field near the FFC-1 borehole and vairations in the stress field with depth. Despite this, the data from the FFC-1 well provide novel and unique information on the complex physical state of the crystalline basement on the margin of the Fennoscandian Shield, which further addresses the need for obtaining in-situ stress data to fully understand the local stress field prior to any stimulation. A temperature of 84°C measured at 3 km depth indicates that a desired EGS temperature of 120–140°C may be reached at 5–6 km depth, assuming a temperature gradient of about 20°C. If the relatively high fracture frequency and occurrence of fracture zones down to 3.1 km are also present at these target depths, then the FFC-1 location may be suitable for heat extraction if the rock mass is properly characterized before stimulation.
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| 13. |
- Liu, Fang, 1975, et al.
(författare)
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Cyclic oxidation of two FeCrAlRE foils at 1100 oC - The influence of the concentration of minor alloying elements on scale microstructure
- 2008
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 595-598, s. 707-716
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Konferensbidrag (refereegranskat)abstract
- Two FeCrAlRE alloys, a commercial, 0C404, and a model alloy in the form of thin foils,with different Mn, Nb, Mo and Ti concentrations were subjected to cyclic oxidation in lab air at1100°C. The oxidized samples were studied by gravimetry, Grazing-Incidence X-ray Diffraction(GI-XRD), Scanning Transmission Electron Microscopy (STEM), and Energy Dispersive X-ray(EDX) analysis. The two FeCrAl alloys exhibit different oxidation kinetics; however, both alloyshave the same weight gain after 500 hours exposure. During the early stages the scale consistsmainly of α-Al2O3 together with some oxide particles containing Mn, Al, Fe and Cr formed on thealloys. After 500 hours the 0C404 scale locally also consists of larger polycrystalline regions ofMn-Cr-Al spinel. In addition, Si-rich oxide, chromia and Al-Cr oxide could be observed at themetal/oxide interface.
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| 14. |
- Lorenz, Henning, Dr. 1972-, et al.
(författare)
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COSC-2 – drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia
- 2022
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Ingår i: Scientific Drilling. - Göttingen : Copernicus Publications. - 1816-8957 .- 1816-3459. ; 30, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- Abstract.The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project aims to characterise the structure and orogenic processes involved in a major collisional mountain belt by multidisciplinary geoscientific research. Located in western central Sweden, the project has drilled two fully cored deep boreholes into the bedrock of the deeply eroded Early Paleozoic Caledonide Orogen. COSC-1 (2014) drilled a subduction-related allochthon and the associated thrust zone. COSC-2 (2020, this paper) extends this section deeper through the underlying nappes (Lower Allochthon), the main Caledonian décollement, and the upper kilometre of basement rocks. COSC-2 targets include the characterisation of orogen-scale detachments, the impact of orogenesis on the basement below the detachment, and the Early Paleozoic palaeoenvironment on the outer margin of palaeocontinent Baltica. This is complemented by research on heat flow, groundwater flow, and the characterisation of the microbial community in the present hard rock environment of the relict mountain belt. COSC-2 successfully, and within budget, recovered a continuous drill core to 2276 m depth. The retrieved geological section is partially different from the expected geological section with respect to the depth to the main décollement and the expected rock types. Although the intensity of synsedimentary deformation in the rocks in the upper part of the drill core might impede the analysis of the Early Paleozoic palaeoenvironment, the superb quality of the drill core and the borehole will facilitate research on the remaining targets and beyond. Protocols for sampling in the hard rock environment and subsequent sample preservation were established for geomicrobiological research and rock mechanical testing. For the former, a sparse sample series along the entire drill core was taken, while the target of the latter was the décollement. COSC-2 was surveyed by a comprehensive post-drilling downhole logging campaign and a combined borehole/land seismic survey in autumn 2021. This paper provides an overview of the COSC-2 (International Continental Scientific Drilling Project – ICDP 5054_2_A and 5054_2_B boreholes) operations and preliminary results. It will be complemented by a detailed operational report and data publication.
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| 15. |
- Rosberg, Jan Erik, et al.
(författare)
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Evaluation of deep geothermal exploration drillings in the crystalline basement of the Fennoscandian Shield Border Zone in south Sweden
- 2021
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Ingår i: Geothermal Energy. - : Springer Science and Business Media LLC. - 2195-9706. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- 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/m2 and the average heat production is 3.0 µW/m3. 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/m3. 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 m2/m3. 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.
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| 16. |
- Rosberg, Jan Erik, et al.
(författare)
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Evaluation of the Lund deep geothermal exploration project in the Romeleåsen Fault Zone, South Sweden : a case study
- 2019
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Ingår i: Geothermal Energy. - : Springer Science and Business Media LLC. - 2195-9706. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- The bedrock of Skåne, the southernmost province of Sweden, has been targeted for geothermal feasibility studies since the late 1970s. An exploration project concerning the geothermal potential in the Romeleåsen Fault Zone was launched outside the town of Lund in 2001. Besides geophysical imaging of the thrust fault zone, the investigations included drilling and investigations of a 3701.8-m-deep exploration well, DGE-1, with the aim to find > 100 °C warm and hydraulically conductive fractured crystalline bedrock associated to the fault zone. The well penetrates a heavily thrusted and predominantly strongly inclined sedimentary succession in hanging rock blocks along the main fault before entering the fractured crystalline basement at 1946 m, primarily composed of gneiss, granite, and metabasite. This paper represents the first comprehensive description and evaluation of the geological, physical, and hydrological properties of the bedrock at these depths in the Romeleåsen Fault Zone coupled to a geothermal assessment. In addition, the applicability of the four drilling methods used in the crystalline basement section is discussed. The outcome of the DGE-1 well shows significant fracturing in the crystalline bedrock at target depth. The investigations show an average thermal gradient of 22 °C/km, an average heat flow of 58 mW/m 2 , and an average heat production of 5.8 µW/m 3 . The values are relatively high in comparison to thermal conditions noted in other deep wells in the Fennoscandian Shield. However, a bottomhole temperature of around 85 °C and insufficient fluid production rate made a commercial geothermal system unviable. Despite this, the experiences from drilling and investigations of the crystalline bedrock at several kilometers depth constitute important proxies for assessing the geothermal potential in similar geological settings and for engineered geothermal systems in the crystalline bedrock of south Sweden.
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| 17. |
- Rosberg, Jan-Erik
(författare)
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Pneumatic slug testing in large-diameter wells
- 2010
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 18:5, s. 1291-1300
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for an alternative method to conventional pumping tests that is logistically easier and faster to use and which can be handled by only one person. The well known slug test fulfils those requirements if the equipment is properly designed. The applicability of small-diameter slug-test equipment using pneumatic initiation in large-diameter wells, up to 12aEuro(3) (0.3 m), is discussed. In wells with 36 times greater cross-sectional area than the slug-test equipment, it will take a long time for casing depressurization after slug initiation. The casing-depressurization time was measured for each slug test and is presented as a part of the results. The small-diameter equipment was found to be applicable and the long casing-depressurization times did not generally affect the transmissivity estimates. The series of slug tests yielded transmissivity estimates that were in good agreement with each other and also when compared with estimates from pumping tests. However, the slug-test results from wells completed in more permeable formations were harder to interpret, and may be an effect of long casing-depressurization times; further investigations are needed. There is a description of the design of several airtight couplings between the slug-test equipment and the casing.
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| 18. |
- Rosberg, Jan-Erik, et al.
(författare)
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Re-injection of groundwater by pressurizing a segmental tunnel lining with permeable backfill
- 2010
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Ingår i: Tunnelling and Underground Space Technology. - : Elsevier BV. - 1878-4364 .- 0886-7798. ; 25:2, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- Recently, within a tunneling project, a method for reinjecting discharged groundwater at tunnel level has been investigated. The method was performed by pressurizing a long section of the lining With ungrouted pea gravel as backfill, in a rock mass with low hydraulic conductivity. Water was reinjected through watertight lining into a section where un-grouted pea gravel was used as backfill. The pressure response was measured both behind the lining and in the rock mass, the latter by means of several observation wells drilled from ground level. Reinjecting water into a rock mass by pressurizing a lining with a permeable backfill (Such as un-grouted pea gravel) was found to be possible and feasible. Well testing methods developed for vertically drilled wells, such as a step injection test and constant head/pressure tests, Were used and found to be applicable, even for testing at tunnel level. It was also found that well known analytical Solutions, developed for vertically drilled wells, can be used for interpretation, e.g. transmissivity from tests performed at tunnel level and from the pressure response in two of the observation wells. (c) 2009 Elsevier Ltd. All rights reserved.
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| 19. |
- Rosberg, Jan-Erik, et al.
(författare)
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Well Development by Jetting Using Coiled Tubing and Simultaneous Pumping.
- 2009
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Ingår i: Ground Water. - : Wiley. - 0017-467X .- 1745-6584. ; 47:6, s. 806-815
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Tidskriftsartikel (refereegranskat)abstract
- During flow testing of a deep, 1927-m, gravel packed screen completed well, it became apparent that well development was needed to increase productivity. A hydrojetting system using coiled tubing in combination with simultaneous pumping was developed and tested and found to be successful. To verify whether the jetting improved the well, the results of a pumping test conducted before and after the jetting operation are compared. In addition, flowmeter logging and hydraulic properties obtained from pumping tests conducted during the jetting operation were also used to verify the improvements. Hydrojetting in combination with simultaneous pumping proved to be an effective cleaning method. After 100 min of pumping, around 110 m less drawdown and 15 L/s higher average flow rate were obtained compared to the values before the jetting operation. The skin factor was positive before the jetting operation and negative thereafter, thus providing additional evidence of improvements of the well. The flowmeter data also confirmed the improvements and were valuable in optimizing the jetting operation. It was also found, from the short-term pumping tests conducted during the jetting operation, that the Hantush-Jacob method for leaky confined aquifers is a valuable indicator of the well development. The combination of methods used for the well development in this case can easily be applied on other deep well projects to obtain a controlled and time-efficient well development.
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| 20. |
- Rosberg, Jan-Erik
(författare)
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Well Testing, Methods and Applicability
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Well testing is widely used today in water wells, oil and gas wells, for geothermal applications, within civil engineering projects, thermal storage and CO2 storage. The overall testing goal is to verify the productivity from a well and/or for characterization of hydraulic and thermal properties, as well as the spatial limitations of an aquifer. There are three major methods for conducting well testing; slug tests, pumping tests and injection tests. The main objective of this thesis is to compare and evaluate the applicability of the three major well testing methods, using experiences gained by active participation in several well testing operations. Testing of shallow and very deep wells as injection tests using a complete tunnel lining are compared and uniquely presented together in the same work. To compare and evaluate the applicability of the three well testing methods, several conditions which govern the selection of hydraulic testing methods are varied and these include, amongst others, the location, depth and diameter of the well. In addition, technical constraints, such as logistics, water handling and external power supply for conducting the testing are also considered. Certain emphasis is also placed on the use and comparison of pneumatic slug testing with other well testing methods, as pneumatic slug testing often complementary to the more expensive and logistically demanding pumping and injection tests. A small diameter slug test equipment was put together for evaluating the applicability of this method and applied in three different geological environments, namely sedimentary deposits, volcanic deposits and the crystalline basement. It was found that knowledge of the applicability of slug tests, pumping tests and injection tests is essential for selecting the most appropriate method. Two of the methods, namely pumping tests and injection tests, are logistically demanding while the third one, slug tests, is easy to execute. Consequently, it is therefore also an inexpensive test method, which is supported by the fact that several tests can be conducted in different wells during the same day. Slug testing using pneumatic initiation has also been demonstrated as a good alternative to pumping tests, obtaining similar transmissivity estimates. An advantage of slug testing is that the transmissivity is estimated from a series of slug tests and not from one single test, which is often the case for pumping or injection tests. Slug testing using pneumatic initiation is often associated with testing in small diameter wells, but in this work it has been shown applicable in large diameter wells at least up to 12". A major advantage with pneumatic slug testing compared with the other methods is that it can be used for transmissivity mapping, simplified by the method’s easy logistics. It is a useful approach if the wells are distributed over a large area. It is suggested that slug testing using pneumatic initiation should be used as a preinvestigation method for civil engineering projects. Further work needs to be carried out for explaining the observed non-linear characteristics in data obtained from some of the slug tested wells. It has also been demonstrated that well testing methods are not only restricted to drilled wells. The methods can also be applied inside a tunnel with injection through the tunnel lining. The testing was performed as step injection and constant head/pressure tests and, in conjunction, the response from the testing was measured in observation wells drilled from ground level. Analytical solutions developed for vertical wells could be used to interpret hydraulic properties such as transmissivity, using injection tests performed at tunnel level and the pressure response measured in two of the observation wells. Well development was found to be of great importance for any type of well testing and, for deep wells, a hydrojetting system using coiled tubing and simultaneous pumping was found to be applicable, successful and time efficient.
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| 21. |
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| 22. |
- Tsang, Chin-Fu, et al.
(författare)
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Hydrologic testing during drilling : application of the flowing fluid electrical conductivity (FFEC) logging method to drilling of a deep borehole
- 2016
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Ingår i: Hydrogeology Journal. - : Springer Science and Business Media LLC. - 1431-2174 .- 1435-0157. ; 24:6, s. 1333-1341
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Tidskriftsartikel (refereegranskat)abstract
- Drilling of a deep borehole does not normally allow for hydrologic testing during the drilling period. It is only done when drilling experiences a large loss (or high return) of drilling fluid due to penetration of a large-transmissivity zone. The paper proposes the possibility of conducting flowing fluid electrical conductivity (FFEC) logging during the drilling period, with negligible impact on the drilling schedule, yet providing important information on depth locations of both high- and low-transmissivity zones and their hydraulic properties. The information can be used to guide downhole fluid sampling and post-drilling detailed testing of the borehole. The method has been applied to the drilling of a 2,500-m borehole at Åre, central Sweden, firstly when the drilling reached 1,600 m, and then when the drilling reached the target depth of 2,500 m. Results unveil eight hydraulically active zones from 300 m down to borehole bottom, with depths determined to within the order of a meter. Further, the first set of data allows the estimation of hydraulic transmissivity values of the six hydraulically conductive zones found from 300 to 1,600 m, which are very low and range over one order of magnitude.
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| 23. |
- Wenning, Quinn C., et al.
(författare)
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Image log analysis of in situ stress orientation, breakout growth, and natural geologic structures to 2.5 km depth in central Scandinavian Caledonides: Results from the COSC-1 borehole
- 2017
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Ingår i: Journal of Geophysical Research - Solid Earth. - : American Geophysical Union (AGU). - 2169-9313 .- 2169-9356. ; 122:5, s. 3999-4019
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Tidskriftsartikel (refereegranskat)abstract
- Stress-induced borehole deformation analysis in the Collisional Orogeny in the Scandinavian Caledonide deep scientific borehole establishes in situ stress orientation in a poorly characterized region in central Sweden. Two acoustic televiewer logging campaigns, with more than 1 year between campaigns, provide detailed images along the full length of the 2.5 km deep borehole for breakout, drilling-induced tensile fracture (DITF), and natural occurring structural analysis. Borehole breakouts occur in 13 distinct zones along total length of 22 m, indicating an average maximum horizontal stress, SHmax, orientation of 127° ± 12°. Infrequent DITFs are constrained within one zone from 786 to 787 m depth (SHmax orientation: 121° ± 07°). These SHmax orientations are in agreement with the general trend in Scandinavia and are in accordance with many mechanisms that generate crustal stress (e.g., ridge push, topographic loading, and mantel driven stresses). The unique acquisition of image logs in two successions allows for analysis of time-dependent borehole deformation, indicating that six breakout zones have crept, both along the borehole axis and radially around the borehole. Strong dynamic moduli measured on core samples and an inferred weak in situ stress anisotropy inhibit the formation of breakouts and DITFs. Natural fracture orientation below 800 m is congruent to extensional or hybrid brittle shear failure along the same trend as the current SHmax. Analysis of foliation in the image logs reinforces the interpretation that the discontinuous seismic reflectors with fluctuating dip observed in seismic profiles are due to recumbent folding and boudinage.
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| 24. |
- Woith, Heiko, et al.
(författare)
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Multi-Level Gas Monitoring : A New Approach in Earthquake Research
- 2020
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Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Fluid anomalies were often considered as possible precursors before earthquakes. However, fluid properties at the surface can change for a variety of reasons, including environmental changes near the surface, the response of the superficial fluid system to loads associated with the mechanical nucleation of earthquake fractures, or as a result of transients in fluid flow from the depths. A key problem is to understand the origin of the anomaly and to distinguish between different causes. We present a new approach to monitor geochemical and geophysical fluid properties along a vertical profile in a set of drillings from a depth of a few hundred meters to the surface. This setup can provide hints on the origin of temporal variations, as the migration direction and speed of properties can be measured. In addition, potential admixtures of fluids from a deep crustal or mantle origin with meteoric fluids can be better quantified. A prototype of a multi-level gas monitoring system comprising flow and pressure probes, as well as monitoring of fluid-geochemical properties and stable isotopes is being implemented in a mofette field with massive CO2 (up to 97 tons per day) degassing. The mofette is believed a gas emission site where CO2 ascends through crustal-scale conduits from as deep as the upper mantle, and may therefore provide a natural window to ongoing magmatic processes at mantle depth. Fluids from three adjacent boreholes—30, 70, and 230 m deep—will be continuously monitored at high sampling rates.
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