Deep Drilling Project Research Articles

Technological challenges to understanding the microbial ecology of deep subsurface ecosystems.

Terrestrial subsurface geomicrobiology is a new frontier in environmental microbiology. It seeks to determine whether life can be sustained in the absence of solar radiation. Subsurface ecosystems are also intriguing astrobiological models useful in the re-creation of life in early Earth scenarios or ascertaining its possible exist- ence on other planetary bodies. Although Darwin pre- Scanning electron microscopy allows the presence of diverse mineral substrates to be correlated with identified biological structures through elemental analysis (EDAX) and morphology, but the metabolic status and the type of functional metabolism of these biological structures cannot be determined using these techniques. The adap- tation of rRN-targeted FISH (rRNA-FISH) to the study the microorganisms associated to semisolid substrates (cata- lysed reporter deposition-FISH (CARD-FISH)) was an important breakthrough in the microbial ecology study of sediments. Even though this technique has not been used intensively in the identification and quantification of micro- organisms in continental drilling projects, it is obvious that in the near future, it will play a significant role in clarifying the ambiguous results generated by more conventional techniques such as comparative sequence analysis, which, as mentioned earlier, require sample sizes and preparation methodologies that average or destroy compartmentalization. Fluorescent oligonucleotide probes were originally designed to target rRNA for identification of microorgan- isms in environmental studies. Recently, a wide range of FISH procedures have been developed targeting not only rRNA, but also mRNA or single genes (Moraru et al., 2010). It is easy to foresee that these procedures will be

Investigating ultra high-enthalpy geothermal systems: a collaborative initiative to promote scientific opportunities

Abstract. Scientists, engineers, and policy makers gathered at a workshop in the San Bernardino Mountains of southern California in October 2013 to discuss the science and technology involved in developing high-enthalpy geothermal fields. A typical high-enthalpy geothermal well between 2000 and 3000 m deep produces a mixture of hot water and steam at 200–300 °C that can be used to generate about 5–10 MWe of electric power. The theme of the workshop was to explore the feasibility and economic potential of increasing the power output of geothermal wells by an order of magnitude by drilling deeper to reach much higher pressures and temperatures. Development of higher enthalpy geothermal systems for power production has obvious advantages; specifically higher temperatures yield higher power outputs per well so that fewer wells are needed, leading to smaller environmental footprints for a given size of power plant. Plans for resource assessment and drilling in such higher enthalpy areas are already underway in Iceland, New Zealand, and Japan. There is considerable potential for similar developments in other countries that already have a large production of electricity from geothermal steam, such as Mexico, the Philippines, Indonesia, Italy, and the USA. However drilling deeper involves technical and economic challenges. One approach to mitigating the cost issue is to form a consortium of industry, government and academia to share the costs and broaden the scope of investigation. An excellent example of such collaboration is the Iceland Deep Drilling Project (IDDP), which is investigating the economic feasibility of producing electricity from supercritical geothermal reservoirs, and this approach could serve as model for future developments elsewhere. A planning committee was formed to explore creating a similar initiative in the USA.

Lake Van deep drilling project PALEOVAN

A complete succession of the lacustrine sediment sequence deposited during the last ∼600,000 years in Lake Van, Eastern Anatolia (Turkey) was drilled in 2010 supported by the International Continental Scientific Drilling Program (ICDP). Based on a detailed seismic site survey, two sites at a water depth of up to 360 m were drilled in summer 2010, and cores were retrieved from sub-lake-floor depths of 140 m (Northern Basin) and 220 m (Ahlat Ridge). To obtain a complete sedimentary section, the two sites were multiple cored in order to investigate the paleoclimate history of a sensitive semi-arid region between the Black, Caspian, and Mediterranean seas. This introductory paper provides background information of the deep drilling project and an overview of the studies presented in this special volume by the PALEOVAN science team dealing with chronology, paleomagnetism, paleoenvironmental proxies, geophysical and petrophysical investigations as well as pore-water and fluid transport.

Chinese First Deep Ice-Core Drilling Project DK-1 at Dome A, Antarctica (2011-2013): progress and performance

AbstractThe Chinese First Deep Ice-Core Drilling Project DK-1 has commenced at Kunlun station in the Dome A region, the highest plateau in Antarctica. During the first season, within the 28th Chinese National Antarctic Research Expedition (CHINARE) 2011/12 the pilot hole was drilled and reamed in order to install a 100 m deep fiberglass casing. In the next season, 29th CHINARE 2012/13, the deep ice-core drilling system was installed, and all the auxiliary equipment was connected and commissioned. After filling the hole with drilling fluid (n-butyl acetate), three runs of ‘wet’ ice-core drilling were carried out and a depth of 131.24 m was reached. Drilling to the bedrock at the target depth of ∼3100 m is planned to be completed during a further four seasons. We describe the work in progress and the status of equipment for the Dome A drilling project.

Drill fluid selection for the SUBGLACIOR probe: a review of silicone oil as a drill fluid

AbstractAs part of the ICE&LASER/SUBGLACIOR projects, an innovative probe called SUBGLACIOR is developed with the aim of perforating the ice sheet down to depths of 3500 m in a single season and continuously measuring in situ the isotopic composition of the meltwater and the methane concentration in trapped gases. Ice chips generated by the electromechanical drilling will be removed from the borehole by circulating a drill fluid. The selection of this drill fluid is important as it will have a major impact on the performance and the environmental evaluation. A literature review of drilling liquids is carried out to select potential fluids for further detailed testing. The selected fluids are varying grades of silicone oils, known as linear polydimethylsiloxanes, and ESTISOL™ 140, an aliphatic ester. The requirements for this project are similar to those for other deep ice-core drilling projects but, due to the embedded analytical system and the speed of drilling, there are some specific considerations. Following extensive testing, we conclude that a silicone fluid with a kinematic viscosity of 3 mm2 s−1 (3 cSt) is ideally suitable and affordable. This evaluation provides new insights into the use of silicone oils as a drill fluid that are of use to the wider ice-core drilling community.

GPS-derived velocity and strain fields around Dome Argus, Antarctica

AbstractKnowledge of the surface topography, velocity field and strain field at an ice-core site is critical to the accurate interpretation of ice-core records. At Dome Argus (Dome A), where a Chinese deep ice-core drilling project is being carried out, we have produced an accurate surface digital elevation model from GPS measurements in January 2013 at 47 sites. We identify two peaks at Dome A, with the northern peak ~7 cm higher than the southern peak. Repeat GPS measurements at 12 sites in 2008 and 2013 provide a surface velocity field around the dome. The surface velocity ranges from 3.1±2.6 to 29.4±1.2 cm a–1, with a mean of 11.1 ~2.4 cm a–1. The surface flow directions are near perpendicular to the surface elevation contours. Velocities from GPS are lower than derived from satellite radar interferometry (InSAR). From GPS velocities, the accuracy of velocity from the existing InSAR velocity field is determined, resulting in a standard deviation of 0.570 m a–1 in speed and 117.5º in direction. This result is consistent with the reported accuracy of InSAR, showing the value of in situ GPS measurements for assessing and correcting remote-sensing results. A surface strain field for the drilling site over Dome A is calculated from 24 strain triangles, showing north–south extension, east– west compression and vertical layer thinning.

RADIX: a minimal-resources rapid-access drilling system

AbstractDetermining the expected age at a potential ice-core drilling site on a polar ice sheet generally depends on a combination of information from remote-sensing methods, estimates of current accumulation and modelling. This poses irreducible uncertainties in retrieving an undisturbed ice core of the desired age. Although recently perfected radar techniques will improve the picture of the ice sheet below future drilling sites, rapid prospective drillings could further increase the success of deep drilling projects. Here we design and explore a drilling system for a minimum-size rapid-access hole. The advantages of a small hole are the low demand for drilling fluid, low overall weight of the equipment, fast installing and de-installing and low costs. We show that, in theory, drilling of a 20 mm hole to a depth of 3000 m is possible in ∼4 days. First concepts have been realized and verified in the field. Both the drill cuttings and the hole itself can be used to characterize the properties of the ice sheet and its potential to provide a trustworthy palaeo-record. A candidate drilling site could be explored in ∼2 weeks, which would enable the characterization of several sites in one summer season.

Drilling of the well IDDP-1

The first well of three proposed by the Iceland Deep Drilling Project (IDDP) was drilled in the Krafla Geothermal Field in 2008–2009 by Landsvirkjun, the National Power Company of Iceland. The well was designed to reach supercritical conditions at 4500m, temperatures above 374°C and pressures above 22MPa. Drilling progress was as planned down to around 2000m when drilling became quite challenging, including becoming stuck at 2094 and 2095m depth, followed by twist offs and subsequent side tracking. Finally, drilling came to an end at 2096m depth in the third leg when cuttings of fresh glass indicated the presence of a magma body at the bottom. As the well had such a rigorous well design, the steering committee of the IDDP decided to complete and flow test the well, rather than abandoning it. The well was very powerful and the project has proved to be a valuable experience for drilling supercritical wells in the future and what happens when magma is encountered. Most importantly, it has been proven that it is possible to drill and complete a well in a very hot zone and produce fluid from an environment near a magma body. If sustained long term production proves possible, the drilling of well IDDP-1 will mark a new era in power production in Krafla.

A plan for a 5 km-deep borehole at Reykjanes, Iceland, into the root zone of a black smoker on land

Abstract. A summary workshop report describing the progress made so far by the Iceland Deep Drilling Project (IDDP) is presented below. The report provides recommendations concerning technical aspects related to deep drilling, and invites international participation in both the engineering and the scientific activities of the next phase of the IDDP. No issues were identified at the workshop that should rule out attempting the drilling, sampling and testing of the proposed IDDP-2 well. Although technically challenging, the consensus of the workshop was that the drilling of such a hot deep well, and producing potentially hostile fluids, is possible but requires careful contingency planning. The future well will be explored for supercritical fluid and/or superheated steam beneath the current production zone of the Reykjanes geothermal field in SW Iceland. This deep borehole will provide the first opportunity worldwide to directly investigate the root zone of a magma-hydrothermal system which is likely to be similar to those beneath the black smokers on the world-encircling mid-ocean rift systems.

Well design for the Iceland Deep Drilling Project (IDDP)

The aim of the Iceland Deep Drilling Projects (IDDP) was to drill to a depth of 4–5km in known high-temperature areas to investigate their roots. The paper describes the design of the “generic” IDDP well and what the plans were. The challenges are to drill a large well with five cemented casing strings to 4500m into a reservoir which can have a temperature of 400–600°C. In 2009 well IDDP-1 was drilled according to these plans but could not reach below 2100m due to the intersection of magma, as will be described in other papers in this special issue of Geothermics. The paper is thus for the historical record of the original design premises and intentions.

Utilization of the chloride bearing, superheated steam from IDDP-1

When a dry steam containing volatile chloride cools to saturation temperature, the compound dissolves in the condensate and forms hydrochloric acid. This can have tremendous consequences for equipment as hydrochloric acid aggressively attacks steel and other metals, causing severe pitting corrosion, crystalline corrosion and stress corrosion cracking of stainless steel components. The Icelandic Deep Drilling Project is dealing with extreme circumstances with high enthalpy, superheated steam possibly containing hydrogen chloride. Successful corrosion mitigation is essential for the feasibility of the development. The goal of this work is to examine different technologies to utilize such a steam, with regard to exergy conservation.

High temperature instruments and methods developed for supercritical geothermal reservoir characterisation and exploitation—The HiTI project

During the early years of the Iceland Deep Drilling Project (IDDP), development of three distinctive technological and scientific approaches were formalised and then carried out until 2010 within a European funded project called HiTI (high temperature instruments for supercritical geothermal reservoir characterisation and exploitation). These approaches were: (1) development of several downhole instruments allowing them to function up to 300°C and 400°C, (2) identification of two new Na/Li cation ratio geothermometric relationships valid at very high temperature, (3) tracer testing with high temperature tolerant organic isomers and finally and (4) basalt rock deformation and petrophysical properties laboratory investigations at high temperature and pressure conditions.

Deep drilling in central Antarctica and penetration into subglacial Lake Vostok

A remarkable event occurred in February 2012: the Vostok deep drilling project was complete at the Vostok station in Antarctica. Russian scientists were the first in the world to penetrate deep into the famous subglacial lake located there. The lake is unique because it has been in isolation from external impacts for a long time. The authors describe everything that has been done to reach the lake’s surface and present the findings.

Stable isotopes of hydrothermal minerals as tracers for geothermal fluids in Iceland

The Reykjanes and Krafla geothermal systems, located within the active rift zone of Iceland, are both potential venues for exploitation of deep supercritical fluids by the Iceland Deep Drilling Project (IDDP). An essential aspect of properly characterizing geochemical and hydrologic processes occurring at supercritical depths is establishing the source, composition and evolution of geothermal fluids. Traditionally, hydrogen isotopes of thermal fluids are used to determine their source. We show that for these, and likely many other Icelandic geothermal systems, analyzing fluid dD is not sufficient alone. Rather, d18O and dD of hydrothermal minerals in conjunction with geochemical characteristics of extant geothermal fluids are necessary to characterize the source and geologic evolution of geothermal reservoir fluids. Here we review results from existing drill holes in the Reykjanes and Krafla geothermal systems to depths of =3km, and explore the utility of using stable isotopes in alteration minerals such as epidote to assess the hydrogeology of extinct volcano-hydrothermal systems by presenting new data from the Geitafell fossil hydrothermal system in southeast Iceland.

Drilling into magma and the implications of the Iceland Deep Drilling Project (IDDP) for high-temperature geothermal systems worldwide

Drilling deeper in high-temperature geothermal systems by the IDDP is aimed at increasing the power output of shallower high-temperature geothermal fields by an order of magnitude without increasing their environmental footprints. The main thrust of the IDDP is to develop deep supercritical systems, but an unexpected encounter with a shallow body of magma demonstrated that very high power outputs are also possible from the contact zone of an intrusion. In the future it may be feasible to produce energy directly from magma. Favorable environments to implement these concepts are likely worldwide wherever active volcanoes and young volcanic rocks occur.

Evolution of low-18O Icelandic crust

The Krafla central volcano in the neovolcanic zone of Iceland hosts a chemically diverse suite of magmas characterized by anomalously low δ18O values. A rhyolite magma intercepted by the Iceland Deep Drilling Project (IDDP) exploratory well at 2.1km depth provided a unique opportunity to investigate the origins of an unerupted rhyolite melt in the primarily basaltic central volcano at Krafla. Here we compare whole rock hydrogen and oxygen isotopes of this melt to those of lavas within and near the caldera of the Krafla central volcano ranging from recent fissure eruptions to Plio--Pleistocene age (including analyses of 18 new samples, plus previously published values) in order to evaluate the petrogenesis of low-18O magmas within the neovolcanic zone of Iceland.Oxygen isotope values of the IDDP-1 melt (δ18O=+3.2±0.2‰) are within the range of Krafla eruptives that have a bimodal composition of olivine-tholeiite and rhyolite (δ18O=+1.6‰ to +4.5‰). Lavas show significantly more variability in hydrogen isotope values (δD=−161‰ to −92‰) than the IDDP-1 melt (−121±2‰), whose δD is comparable to local hydrothermal epidote (−127 to −108‰), and show significantly lower water contents than IDDP-1 (0.1–1.1wt%, in contrast to ~1.8wt%). Basaltic to dacitic lavas from the proximal Heidarspordur ridge volcanic zone have δ18O between +3.4‰ and +4.2‰ and δD between −105‰ and −99‰.Uniformity of oxygen isotopes in the Heidarspordur ridge lavas suggests that their magmatic compositional variations are a consequence of fractional crystallization. The δD of the glass sampled by IDDP-1 unequivocally identifies the source of silicic low-18O melts like those erupted from within the caldera of the Krafla volcano as anatexis of meteoric-hydrothermally altered basalts resulting from the intrusion of mantle-derived basaltic magma. Finally, mantle-derived basalts in both the Krafla central volcano and Heidarspordur ridge (MgO>5wt%) have δ18O values lower than the typical MORB. There is convincing evidence favoring low-18O compositions in primitive Icelandic basalts as also being the result of assimilating meteoric hydrothermally altered Icelandic crust, particularly in the roots of central volcanic complexes, where high-level intrusions develop. Here hydrothermally altered basalts have a high probability of undergoing partial melting. If this is the case, we hypothesize that there should be a notable secular variation in the δ18O values of upper crustal igneous products of the Iceland mantle plume over the sub-aerial extrusive geologic history of Iceland, in which progressively younger lavas exhibit decreasing δ18O values. Synthesis of published oxygen isotope analyses of unaltered whole rock and mineral separates of lavas from Tertiary age to present lends support to this hypothesis.

The concept of the Iceland deep drilling project

Calculations discussed in the Iceland Deep Drilling Project feasibility study in 2003 indicated that, for same volumetric flow rate of steam, a geothermal well producing from natural supercritical fluid would have the potential to generate power outputs an order of magnitude greater than from conventional high-temperature wells (240–340°C). To reach supercritical hydrous fluid conditions in natural geothermal systems requires deep drilling to a minimum depth of some 3.5–5km were temperature conditions can be expected to range between 400 and 600°C in reasonably active high-temperature fields. Three geothermal fields in Iceland, Reykjanes, Hengill and Krafla, were selected as suitable locations for deep drilling to test this concept in search of natural supercritical geothermal fluid systems.

日本における湖沼掘削

The author reviews scientific drilling projects investigating lacustrine sediments in Japan. The lake sediments are excellent archives for paleoenvironments and tectonic movements, and are especially useful when sediments have sequences of annual bands. The earliest deep drilling projects, namely 200 m and 1,400 m drillings, were performed at Lake Biwa in 1971 and 1982-1983, respectively. The results revealed detailed climate changes and tectonic movements of the Omi basin over the past 1.6 Ma. Sediment cores from Lake Suigetsu provide an excellent chronological key based on annual bands for the past 50 ka or more. Furthermore, studies on sediment cores from Lake Nojiri and the lacustrine Takano Formation provided high time resolution data on paleoclimate for the past 160 ka: these data are based on the total organic carbon content and pollen composition of the sediment cores. The impregnation method to make a thin section of lake sediment is essential for counting annual layers to avoid miscounting varves. Lacustrine sediments exposed on land may also be useful archives of the Pleistocene as shown by case studies on Takano and Yoshino Formations. Sample storage systems and sub-sampling method such as double-L channel are useful for systematic research on sediments.

火山体掘削の科学的成果と今後の展望

Drilling into volcanoes is important to obtain an understanding of subterranean three-dimensional geometrical and thermal structures. Even shallow drilling in volcanic areas provides various information including the eruption histories of the volcanoes. The magmatic system and conditions at eruption sites together with eruption and development histories are important to understand magma processes in the upper crust, forecast future eruptions, and mitigate volcanic disasters. Using the holes drilled as observation wells is an additional advantage for monitoring the volcanic activity in-situ. Volcano and magma development histories have been revealed by deep drilling at Mauna Kea volcano (Hawaii), Unzen volcano, Fuji volcano, etc. Drillings was carried out into a hot basalt lava lake and a volcanic conduit of a recently erupted Kilauea volcano (Hawaii) and Unzen volcano, respectively. During geothermal drilling at Kakkonda and in Iceland, a solidifying magma chamber and rhyolite magma, respectively, were accidentally drilled. Three-D subsurface structures under caldera volcanoes have been understood by carrying out geothermal drillings at Long Valley, Aso, and Nigorikawa calderas. In addition, some projects to drill at caldera volcanoes have been undertaken or are being prepared as ICDP projects. Recently, national economic problems have made it difficult for researchers to propose deep drilling projects at volcanoes and calderas as an ICDP project. Under this situation, close international cooperation among researchers related to these projects or participation in geothermal exploration drilling projects may be better solutions.

わが国におけるICDP以前の陸上学術ボーリング計画検討の歴史

Continental scientific drilling projects were promoted actively around the world in the latter part of the 20th century. The super deep drilling projects developed drilling technologies, and highlighted a lack of understanding of the Earth's interior. The International Continental Scientific Drilling Program was initiated to promote continental scientific drilling projects globally and international cooperation. Geology needs to be taken into consideration more and technology for preventing bore-hole break-outs needs to be developed in continental drilling projects. More work is required to take a fresh look at the Earth based on the facts obtained from the surface. Continental scientific drilling is a potentially important tool for undertaking this study of the Earth in areas such as the subsiding atoll concept and ocean floor spreading. Because accretion and arc magmatism accompanying subduction of the ocean floor are important in the formation of continental crust, continental scientific drill projects on the Japanese Islands will play an important role in geology and human society.