Deep Drilling Project Research Articles

Lithium systematics in the Krafla volcanic system: comparison between surface rhyolites and felsic cuttings from the Iceland deep drilling project -1 (IDDP-1)

The unexpected discovery of felsic magma by the Iceland Deep Drilling Project-1 (IDDP-1) in the Krafla volcanic system (KVS) presents a unique opportunity to investigate pre-eruptive lithium (Li) dynamics and establish a more direct connection between magma reservoirs and volcanic deposits. Our study provides new insights into Li abundances and isotope compositions in bulk-rock, minerals, and groundmass glass from rhyolitic lavas at KVS, encompassing various stages of groundmass crystallisation. Additionally, we examined felsic cuttings retrieved from the IDDP-1 well, comprising crystal-poor obsidian and crystal-bearing to -rich ‘felsite’ particles. Groundmass glasses from surface lavas show limited variability in K/Na, indicating limited secondary hydration of the glasses and that their Li contents seem to not be affected by this post-eruptive process. Lithium inventories in groundmass glasses and minerals within lavas exhibit variations consistent with the cooling history of the deposit, resembling patterns seen in Snake River Plain ignimbrites. Lithium contents of glassy rhyolitic lavas, whether bulk-rock (avg. 27.2 ± 3.1 μg/g) or groundmass glass (average 28.4 ± 4.7 μg/g), and their bulk isotopic compositions (avg. δ7Li =+ 4.4 ± 0.2‰) overlap with those observed in IDDP-1 obsidian cuts (avg. 24.9 μg/g Li in bulk, 28.6 ± 1.5 μg/g in groundmass glass, and δ7Li = 4.5 ± 0.2‰). Glassy lavas lacking spherulites may potentially preserve pristine magmatic Li element and isotope compositions, while areas with extensive groundmass crystallisation reveal Li enrichments in phenocrysts. Plagioclases in slowly cooled parts of the deposit record a two-fold increase in Li contents compared to plagioclase found in glassy counterparts, along with evidence of open-system degassing marked by heavier bulk Li isotope compositions and lower bulk Li contents of the crystallised lava portions (avg. δ7Li = +7.2 ± 0.1‰ and 7 ± 0.8 μg/g Li) relative to bulk glassy lithologies (avg. δ7Li = +4.1 ± 0.1‰ and 28 ± 2 μg/g Li). Partition coefficients derived from IDDP-1 cuts successfully predict Li inventories in vitrophyres of rhyolites on the surface of the KVS. Lithium isotope compositions of the crystal-rich IDDP-1 cuts are significantly heavier (avg. δ7Li = +7.2 ± 0.2‰) than lavas and IDDP-1 obsidian cuts, casting doubt on the notion that the IDDP-1 rhyolitic magma could result from the melting of felsite lenses in the KVS. Lithium contents in groundmass glasses within IDDP-1 crystal-rich cuts show higher Li contents (avg. 55.1–60.7 μg/g), correlating with the higher crystal content and an increase in other incompatible elements (avg. 250 μg/g Rb) relative to obsidian cuttings (avg. 75 μg/g Rb).

In situ probing of the present-day zircon-bearing magma chamber at Krafla, Northeastern Iceland

Active felsic magmatism has been rarely probed in situ by drilling but one recent exception is quenched rhyolite sampled during the 2009 Iceland Deep Drilling Project (IDDP). We report finding of rare zircons of up to ∼100 µm in size in rhyolite glasses from the IDDP-1 well products and the host 1724 AD Viti granophyres. The applied SHRIMP U-Th dating for both the IDDP and the Viti granophyre zircons gives zero-age (±2 kyr), and therefore suggests that the IDDP-1 zircons have crystallized from an active magma intrusion rather than due to the 20–80 ka post-caldera magmatic episodes recorded by nearby domes and ridges. Ti-in-zircon geothermometer for Viti granophyre reveals zircon crystallization temperatures ∼800°C–900°C, whereas IDDP-1 rhyolite zircon cores show Ti content higher than 100 ppm, corresponding to temperatures up to ∼1,100°C according to the Ti-in-zircon thermometer. According to our thermochemical model at such elevated temperatures as 1,100°C, rhyolitic magma cannot be saturated with zircon and zircon crystallization is not possible. We explain this controversy by either kinetic effects or non-ideal Ti incorporation into growing zircons at low pressures that start to grow from nucleus at temperatures ∼930°C. High temperatures recorded by IDDP-1 zircon together with an occurrence of baddeleyite require that the rhyolite magma formed by partial melting of the host granophyre due to basaltic magma intrusion. Zr concentration profiles in glass around zircons are flat, suggesting residence in rhyolitic melt for >4 years. In our thermochemical modeling, three scenarios are considered. The host felsite rocks are intruded by: 1) a basaltic sill, 2) rhyolite magma 3) rhyolite sill connected to a deeper magmatic system. Based on the solution of the heat conduction equation accounting for the release of latent heat and effective thermal conductivity, these data confirm that the rhyolite magma could be produced by felsic crust melting as a result of injection of a basaltic or rhyolite sill during the Krafla Fires eruption (1975 AD).

A creep model for ultra-deep salt rock considering thermal-mechanical damage under triaxial stress conditions

To investigate the specific creep behavior of ultra-deep buried salt during oil and gas exploitation, a set of triaxial creep experiments was conducted at elevated temperatures with constant axial pressure and unloading confining pressure conditions. Experimental results show that the salt sample deforms more significantly with the increase of applied temperature and deviatoric loading. The accelerated creep phase is not occurring until the applied temperature reaches 130 °C, and higher temperature is beneficial to the occurrence of accelerated creep. To describe the specific creep behavior, a novel three-dimensional (3D) creep constitutive model is developed that incorporates the thermal and mechanical variables into mechanical elements. Subsequently, the standard particle swarm optimization (SPSO) method is adopted to fit the experimental data, and the sensibility of key model parameters is analyzed to further illustrate the model function. As a result, the model can accurately predict the creep behavior of salt under the coupled thermo-mechanical effect in deep-buried condition. Based on the research results, the creep mechanical behavior of wellbore shrinkage is predicted in deep drilling projects crossing salt layer, which has practical implications for deep rock mechanics problems.

2022 Joint Barringer Medal for Kai Wünnemann and Gareth S. Collins

2022 Joint Barringer Medal for Kai Wünnemann and Gareth S. Collins

E&P Notes (November 2022)

E&P Notes (November 2022)

Heat mining from super-hot horizons of the Larderello geothermal field, Italy

Super-hot rock geothermal is an emerging source of renewable and carbon-free energy. This paper is the first attempt to explore fluid and heat flow dynamics in the reservoir-wellbore coupled system, to assess the power generation performance of a super-hot (>450 °C) enhanced geothermal system (EGS). We developed a high-performance code and built a 3-D wellbore-reservoir coupled model based on data from a recently completed deep-drilling project at Larderello, Italy. The general pattern of the super-hot EGS is characterized by a significant temperature plummet (>60 °C), after which the production fluid evolves from steam to a two-phase mixture till the end of the operation period. Reservoir pressure emerges as a key parameter to determine the temperature of the two-phase mixture. By realistically capturing phase transitions driven by coupled thermo-hydraulic processes during operations, our numerical model predicts a lower power generation efficiency compared to previous attempts based on ultra-simplified models. Although finalized at assessing the thermodynamic viability of a specific system, this modeling approach provides general information on fundamental thermo-hydraulic processes in the Earth crust that might be applied for the design of similar EGS projects elsewhere.

Thermal History of Lithosphere Formed Beneath Fast Spreading Ridges: Constraints From the Mantle Transition Zone of the East Pacific Rise at Hess Deep and Oman Drilling Project, Wadi Zeeb, Samail Ophiolite

AbstractWe investigate the cooling histories of peridotites and gabbros from localities that expose oceanic lithosphere formed beneath two fast seafloor spreading centers: Hess Deep as recovered from IODP Expedition 345 and ODP Leg 147, and the Oman Ophiolite as sampled by the Oman Drilling Project, ICDP Expedition 5057 (OmanDP). At these locations, relict crust‐mantle transition zones are directly sampled, enabling characterization of the thermal history of the crust‐mantle transition, and by inference, the depth extent of hydrothermal circulation beneath spreading centers. We measured major and trace element abundances in crustal gabbros and mantle peridotites from Hess Deep and OmanDP, and applied major and trace element‐based thermometers. Geospeedometric interpretation of the temperatures suggests similar cooling histories at both locations; cooling rates ranged from 0.02 to 2.6 °C/y from peak temperatures up to 1,350°C. The rates are consistent on either side of the paleo‐Moho (i.e., in the crust and mantle). Models for conductive cooling of the lower oceanic crust predict rates more than two orders of magnitude slower at the crust‐mantle transition zone, while thermal models that invoke deep and efficient hydrothermal circulation throughout the entire crustal section predict rates consistent with our observations. We infer that hydrothermal cooling extended to or near the petrologic Moho beneath the East Pacific Rise and the OmanDP paleo‐spreading center, consistent with the Sheeted Sills model for crustal accretion. Comparison with previously published rates recalculated using the methods we employed suggests the oceanic lower crust is cooled hydrothermally in some places and by conduction at others.

Imaging high-temperature geothermal reservoirs with ambient seismic noise tomography, a case study of the Hengill geothermal field, SW Iceland

The Hengill volcanic system is located in the Reykjanes Peninsula (Iceland) and hosts two large geothermal power plants: Nesjavellir and Hellisheiði. This area is the next target for the Iceland Deep Drilling Project (IDDP) to search for super-critical fluids. Here, we investigate the potential for ambient seismic noise tomography to be used as a geothermal exploration tool. The results are compared with different geophysical observables, of which resistivity modeling shows an excellent correlation with our results. We also observe a prominent seismic velocity reduction to the south of Hverahlíð, where the most powerful boreholes in the region are located.

Review of Recent Drilling Projects in Unconventional Geothermal Resources at Campi Flegrei Caldera, Cornubian Batholith, and Williston Sedimentary Basin

Unconventional geothermal resource development can contribute to increase power generation from renewable energy sources in countries without conventional hydrothermal reservoirs, which are usually associated with magmatic activity and extensional faulting, as well as to expand the generation in those regions where conventional resources are already used. Three recent drilling experiences focused on the characterization of unconventional resources are described and compared: the Campi Flegrei Deep Drilling Project (CFDDP) in Italy, the United Downs Deep Geothermal Power (UDDGP) project in the United Kingdom, and the DEEP Earth Energy Production in Canada. The main aspects of each project are described (geology, drilling, data collection, communication strategies) and compared to discuss challenges encountered at the tree sites considered, including a scientific drilling project (CFDDP) and two industrial ones (UDDGP and DEEP). The first project, at the first stage of pilot hole, although not reaching deep supercritical targets, showed extremely high, very rare thermal gradients even at shallow depths. Although each project has its own history, as well as social and economic context, the lessons learned at each drilling site can be used to further facilitate geothermal energy development.

Modelling an unconventional closed-loop deep borehole heat exchanger (DBHE): sensitivity analysis on the Newberry volcanic setting

Alternative (unconventional) deep geothermal designs are needed to provide a secure and efficient geothermal energy supply. An in-depth sensitivity analysis was investigated considering a deep borehole closed-loop heat exchanger (DBHE) to overcome the current limitations of deep EGS. A T2Well/EOS1 model previously calibrated on an experimental DBHE in Hawaii was adapted to the current NWG 55-29 well at the Newberry volcano site in Central Oregon. A sensitivity analysis was carried out, including parameters such as the working fluid mass flow rate, the casing and cement thermal properties, and the wellbore radii dimensions. The results conclude the highest energy flow rate to be 1.5 MW, after an annulus radii increase and an imposed mass flow rate of 5 kg/s. At 3 kg/s, the DBHE yielded an energy flow rate a factor of 3.5 lower than the NWG 55-29 conventional design. Despite this loss, the sensitivity analysis allows an assessment of the key thermodynamics within the wellbore and provides a valuable insight into how heat is lost/gained throughout the system. This analysis was performed under the assumption of subcritical conditions, and could aid the development of unconventional designs within future EGS work like the Newberry Deep Drilling Project (NDDP). Requirements for further software development are briefly discussed, which would facilitate the modelling of unconventional geothermal wells in supercritical systems to support EGS projects that could extend to deeper depths.

Geothermal heat flux from measured temperature profiles in deep ice boreholes in Antarctica

Abstract. The temperature at the Antarctic Ice Sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modeling has been used to estimate the geothermal heat flux (GHF) under the ice sheet. During the last 5 decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching or nearly reaching the bed at inland locations in Antarctica. When temperature profiles in these boreholes and steady-state heat flow modeling are combined with estimates of vertical velocity, the heat flow at the ice-sheet base is translated to a geothermal heat flux of 57.9 ± 6.4 mW m−2 at Dome C, 78.9 ± 5.0 mW m−2 at Dome F, and 86.9 ± 16.6 mW m−2 at Kohnen, all higher than the predicted values at these sites. This warm base under the East Antarctic Ice Sheet (EAIS) could be caused by radiogenic heat effects or hydrothermal circulation not accounted for by the models. The GHF at the base of the ice sheet at Vostok has a negative value of −3.6 ± 5.3 mW m−2, indicating that water from Lake Vostok is freezing onto the ice-sheet base. Correlation analyses between modeled and measured depth–age scales at the EAIS sites indicate that all of them can be adequately approximated by a steady-state model. Horizontal velocities and their variation over ice-age cycles are much greater for the West Antarctic Ice Sheet than for the interior EAIS sites; a steady-state model cannot precisely describe the temperature distribution here. Even if the correlation factors for the best fitting age–depth curve are only moderate for the West Antarctic sites, the GHF values estimated here of 88.4 ± 7.6 mW m−2 at Byrd and 113.3 ± 16.9 mW m−2 at WAIS Divide can be used as references before more precise estimates are made on the subject.

Geothermal energy and ore-forming potential of 600 °C mid-ocean-ridge hydrothermal fluids

Abstract The ∼4500-m-deep Iceland Deep Drilling Project (IDDP) borehole IDDP-2 in Iceland penetrated the root of an active seawater-recharged hydrothermal system below the Mid-Atlantic Ridge. As direct sampling of pristine free fluid was impossible, we used fluid inclusions to constrain the in situ conditions and fluid composition at the bottom of the hydrothermal convection cell. The fluid temperature is ∼600 °C, and its pressure is near-hydrostatic (∼45 MPa). The fluid exists as two separate phases: an H2O-rich vapor (with an enthalpy of ∼59.4 kJ/mol) and an Fe-K–rich brine containing 2000 µg/g Cu, 3.5 µg/g Ag, 1.4 µg/g U, and 0.14 µg/g Au. Occasionally, the fluid inclusions coexist with rhyolite melt inclusions. These findings indicate that the borehole intersected high-energy steam, which is valuable for energy production, and discovered a potentially ore-forming brine. We suggest that similar fluids circulate deep beneath mid-ocean ridges worldwide and form volcanogenic massive sulfide Cu-Zn-Au-Ag ore deposits.

Materials investigation of the high temperature IDDP-1 wellhead

The Iceland Deep Drilling Project (IDDP) well IDDP-1 in the Krafla geothermal field in Iceland is the most powerful geothermal well on record, with a maximum wellhead temperature of 452 °C and 140 bar pressures. In the end, the well had to be abandoned and closed permanently due to several casing failures, including a number of collapses and tensile coupling failures of the innermost casing – the production casing. The history of this first IDDP well is discussed in this paper, revealing the conditions the carbon steel was exposed to. The metal samples degrading mechanism was investigated by mechanical testing and microstructure analysis. For the first time, material used in geothermal steam in situ above 400 °C for a long period was investigated and a new alarming cracking mechanism detected. This cracking mechanism due to formation of methane inside the carbon steel structure results in severe cracks and as a result the steel loses its strength and ductility. This study reveals the need for review of material selection for high-temperature geothermal wells.

Stratigraphic correlation and splice generation for sediments recovered from a large-lake drilling project: an example from Lake Junín, Peru

Sediment records from deep-drilling projects such as those carried out by the International Continental Scientific Drilling Program are often tens to hundreds of meters in length. To ensure the complete recovery of a stratigraphic section, a basin is usually cored multiple times in adjacent holes so that gaps between sequential cores, poorly recovered sections, or intervals affected by disturbance can be bridged or replaced with sediments from another hole. Stratigraphic correlation, the alignment of stratigraphically-equivalent horizons in cores from different holes in a common-depth scale, and splice generation, the integration of the most-representative core sections into a composite-stratigraphic section, are essential steps in this process to both evaluate and synthesize the recovered-sediment record and focus the scientific analyses. However, these undertakings can be complex and are inherently subjective, making the need for the development of a single robust stratigraphic section early in the project critical to its success. Despite this, the steps between core recovery and on-splice data generation are rarely published in sufficient detail to allow reconstruction, or refinement, of the composited record at a later date. To increase the transparency of how the composite record is created, and to provide a template for future projects, we detail the step-by-step approaches and decisions involved in generating the composite-depth scale and complete-stratigraphic splice following recovery of sediments from Lake Junin, Peru. We first explain the details and nuances of different drilling-depth scales before describing how we integrated different physical property records to generate the composite-depth scale and complete-stratigraphic splice. Here, we show that due to the complex stratigraphy in the Lake Junin sediments, high-resolution line-scan images of the cores offer millimeter-scale precision for construction of the primary-stratigraphic splice at a resolution not afforded by other physical property data. Finally, through comparison of the spliced record to physical-property records acquired in situ on the borehole, we demonstrate that the stratigraphic splice is an accurate representation of the sediment accumulated in the Lake Junin basin.

Numerical simulation of a Deep Borehole Heat Exchanger in the Krafla geothermal system

The geothermal energy sector is facing numerous challenges related to heat recovery efficiency and economic feasibility. Research on superheated/supercritical geothermal systems is progressing in Europe, triggered by the Iceland Deep Drilling project (IDDP) and the DESCRAMBLE project in Italy. In Iceland, the IDDP-1 well, which reached a magma intrusion at a depth of 2100 m, raised new opportunities to untap the geothermal potential near magmatic intrusions. Given their highly corrosive nature, geothermal fluids weaken the wellbores integrity during conventional geothermal production. Closed-loop Deep Borehole Heat Exchangers (DBHE) that do not require fluid exchange between the subsurface and the wells represent a strategic alternative for recovering heat from these unconventional geothermal resources, while minimising the risk of in situ reservoir damage. The thermal influence and heat recovery associated with a hypothetical DBHE drilled into the IDDP geological settings are investigated via Computational Fluid Dynamics (CFD) techniques, simulating 30 years of production. Two wellbore designs are modelled, based on simplified geological properties from the IDDP-1 well description. The results show that, during the first year of production, the output temperature is function of the working fluid velocity before reaching pseudo-steady state conditions. The cooling perturbation near the bottom hole is shown to grow radially from 10 to 40 m between 1 and 10 years of production, and the calculated output power reaches up to 1.2 MWth for a single well. The heat transfer at the bottom well bore is enhanced by extending the inner well deeper into the ground. Subject to full economic analysis to be performed at field scale, the significantly lower technical risks of the closed-loop DBHE could outweigh the lower thermal output per well compared to theoretical expectations from open-loop Enhanced Geothermal Systems (EGS).

Mechanism of rift flank uplift and escarpment formation evidenced by Western Ghats, India

The Western Ghats is one of the largest escarpments on earth, containing Reunion plume derived Deccan Traps, it is an excellent example to probe epeirogenic uplift, extension and subsidence in volcanic continental margins. The most continuous unbiased stratigraphic section of basalt down to the basement within a 1250 m drill hole of the Continental Scientific Deep Drilling Project is a valuable resource to investigate the above aspects. The flows across the entire drill core are geologically subaerial in character with basement exposed ~300 m below the mean sea level; they clearly display more evolved compositions from primary melts of mantle in terms of petrology, and only a single geomagnetic polarity transition in palaeomagnetic data. These results, combined with existing geological and geophysical data, constitute a multi-method approach that demonstrates (a) igneous underplating caused uplift prior to frequently suggested flexural isostasy (b) plume impact and eruption are near-simultaneous and extension/rifting essentially followed soon after volcanism and (c) lithosphere beneath the continental margin, while returning to normal temperatures following the Seychelles-India breakup, experienced thermal collapse and subsidence causing slumping of basalt basement below sea level.

Radar isochronic layer dating for a deep ice core at Kunlun Station, Antarctica

The ages and accumulation rates of ice are important boundary conditions for paleoclimatic ice models. Radar-detected isochronic layers can be used to date the ice column beneath the ice surface and infer past accumulation rates. A Deep Ice-Core Drilling Project has been carried out at Kunlun station in the Dome A region, East Antarctica. Radio echo sounding data are collected during the 2004/2005 Chinese National Research Expedition and the 2007/2008 Dome Connection East Antarctica project of the Alfred Wegener Institute (Germany). Radar isochronic layers from the dataset were linked to compare a new deep ice core site from Kunlun station and the Vostok ice core site. Ten visible layers, accounting for ∼50% ice thickness at the Kunlun station ice core site, were dated based on the Vostok ice core chronology. At 1,640 m depth below surface, an age of ∼160,400 yr was determined, corresponding to a bright layer at Kunlun station. These layers provided geometric information on the past surface of the ice sheet around the ice core site through the Wisconsin glacial stage, Eemian interglacial and Marine Isotope Stage 6. Based on a simple ice flow model and the age-depth relationship, we concluded that the region around the Kunlun ice core site had lower past accumulation rates, consistent with the present pattern. The age-depth relationship would thus be expected to correlate and constrain the chronology of the deep ice core at Kunlun station in the future.

Long-Term Monitoring with Fiber Optics Distributed Temperature Sensing at Campi Flegrei: The Campi Flegrei Deep Drilling Project.

Monitoring volcanic phenomena is a key question, for both volcanological research and for civil protection purposes. This is particularly true in densely populated volcanic areas, like the Campi Flegrei caldera, which includes part of the large city of Naples (Italy). Borehole monitoring of volcanoes is the most promising way to improve classical methods of surface monitoring, although not commonly applied yet. Fiber optics technology is the most practical and suitable way to operate in such high temperature and aggressive environmental conditions. In this paper, we describe a fiber optics Distributed Temperature Sensing (DTS) sensor, which has been designed to continuously measure temperature all along a 500 m. deep well drilled in the west side of Naples (Bagnoli area), lying in the Campi Flegrei volcanic area. It has then been installed as part of the international ‘Campi Flegrei Deep Drilling Project’, and is continuously operating, giving insight on the time variation of temperature along the whole borehole depth. Such continuous monitoring of temperature can in turn indicate volcanic processes linked to magma dynamics and/or to changes in the hydrothermal system. The developed monitoring system, working at bottom temperatures higher than 100 °C, demonstrates the feasibility and effectiveness of using DTS for borehole volcanic monitoring.

The Newberry Deep Drilling Project (NDDP) workshop

Abstract. The important scientific questions that will form the basis of a full proposal to drill a deep well to the ductile–brittle transition zone (T>400 ∘C) at Newberry Volcano, central Oregon state, USA, were discussed during an International Continental Drilling Program (ICDP) sponsored workshop held at the Oregon State University-Cascades campus in Bend, Oregon, from 10 to 13 September 2017. Newberry Volcano is one of the largest geothermal heat reservoirs in the USA and has been extensively studied for the last 40 years. The Newberry Deep Drilling Project (NDDP) will be located at an idle geothermal exploration well, NWG 46-16, drilled in 2008, 3500 m deep and 340–374 ∘C at bottom, which will be deepened another 1000 to 1300 m to reach 500 ∘C. The workshop concluded by setting ambitious goals for the NDDP: (1) test the enhanced geothermal system (EGS) above the critical point of water, (2) collect samples of rocks within the brittle–ductile transition, (3) investigate volcanic hazards, (4) study magmatic geomechanics, (5) calibrate geophysical imaging techniques, and (6) test technology for drilling, well completion, and geophysical monitoring in a very high-temperature environment. Based on these recommendations, a full drilling proposal was submitted in January 2018 to the ICDP for deepening an existing well. The next steps will be to continue building a team with project, technology, and investment partners to make the NDDP a reality.

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog

The aim of the Iceland Deep Drilling Project is to drill into supercritical geothermal systems and examine their economic potential. The exploratory well IDDP-2 was drilled in the Reykjanes geothermal field in SW Iceland, on the landward extension of the Mid-Atlantic Ridge. The Reykjanes geothermal field produces from a <300 °C reservoir at 1 to 2.5 km depth and is unusual because it is recharged by seawater. The well was cased to 3000 m depth, and then angled towards the main up-flow zone of the system, to a total slant depth of 4659 m (~4500 m vertical depth). Based on alteration mineral assemblages, joint inversion of wireline logging, and rate of heating measurements, the bottom hole temperature is estimated to be about 535 °C.The major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth. Drilling continued without recovering drill cuttings, consequently spot coring provided the only deep rock samples from the well. These cores are characteristic of a basaltic sheeted dike complex, with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies, hornblende hornfels, and pyroxene hornfels, allowing the opportunity to investigate water-rock interaction in the active roots of an analog of a submarine hydrothermal system. As they have not yet been sampled, the composition of the deep fluids at Reykjanes is unknown at present. Cold water is currently being injected with the aim of enhancing permeability at depth, before allowing the well to heat up prior to flow tests planned for early 2019. The well has at least two fluid feed zones, a dominant one at 3.4 km depth and a second smaller one at 4.5 km.Extensive geophysical surveys of the Reykjanes Peninsula completed recently allow correlation of geophysical signals with rocks properties and in-situ conditions in the subsurface. Earthquake activity monitored with a local seismic network during drilling the IDDP-2 drilling detected abundant small earthquakes (ML ≤ 2) within the depth range of 3–5 km. A zone at 3–5 km depth below the producing geothermal field that was generally aseismic prior to drilling, but became seismically active during the drilling.The drilling of the IDDP-2 has achieved number of scientific and engineering firsts. It is the deepest and hottest drill hole so far sited on an active mid-ocean spreading center. It penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems.