The CO2 SINK Boreholes for Geological Storage Testing

Europe’s first onshore scientific carbon dioxide storage testing project CO2SINK (CO2 Storage by Injection into a Natural saline aquifer at Ketzin) is performed in a saline aquifer in NE Germany. The major objectives of CO2SINK are the advancement of the science and practical processes for underground storage of carbon dioxide, and the provision of operational field results to aid in the development of standards for CO2 geological storage. Three boreholes (one injection well and two observation wells) have been drilled in2007, each to a depth of about 800 m. The wells are completed as “smart” wells containing a variety of permanent downhole sensing equipment, which has proven its functionality during its baseline surveys. The injection of CO2 is scheduled for spring 2008 and is intended to last up to two years to allow for monitoring of migration and fate of the injected gas through a combination of downhole monitoring with surface geophysical surveys. This report summarizeswell design, drilling, coring, and completion operations

Temperature dependent characterization of optical fibres for distributed temperature sensing in hot geothermal wells

This study was performed in order to select a proper fibre for the application of a distributed temperature sensing system within a hot geothermal well in Iceland. Commercially available high temperature graded index fibres have been tested under in-situ temperature conditions. Experiments have been performed with four different polyimide coated fibres, a fibre with an aluminum coating and a fibre with a gold coating. To select a fibre, the relationship between attenuation, temperature, and time has been analyzed together with SEM micrographs. On the basis of these experiments, polyimide fibres have been chosen for utilisation. Further tests in ambient and inert atmosphere have been conducted with two polyimide coated fibres to set an operating temperature limit for these fibres. SEM micrographs, together with coating colour changes have been used to characterize the high temperature performance of the fibres. A novel cable design has been developed, a deployment strategy has been worked out and a suitable well for deployment has been selected.Comment: PACS: 42.81.Pa, 93.85.Fg, 47.80.Fg, 91.35.Dc, 07.20.Dt, 07.60.V

Thermal properties of gas hydrate bearing sediments and effects of phase transitions on the transport of heat deduced from temperature logging at Mallik, NWT, Canada

In vielen Gebieten des Norddeutschen Beckens (NEGB Northeast German Basin) tritt Salzwasser oberflächennah auf oder erreicht sogar die Oberfläche. Obwohl dieses Phänomen bereits seit zwei Jahrhunderten beobachtet wird, sind der Ursprung und die Mechanismen des Salzwasserflusses im Aquifer des NEGB nicht vollständig verstanden. Die Antriebskräfte in einem geothermischen System wie einem Becken können intrinsisch sein, zum Beispiel thermische Gradienten, und/oder extern sein, zum Beispiel der hydraulische Druckhöhe. Um die Mechanismen des Salzwassertransports innerhalb des Beckens zu klären, wurden für das NEGB thermohaline Simulationen in 2D- und 3D-Szenarios durchgeführt. Basierend auf einer umfangreichen Datensammlung wurde zu diesem Zweck ein hydrogeologisches Modell des NEGB entwickelt, das die stratigraphischen und hydrogeologischen Haupteinheiten vom Oberen Perm bis zum Quartär beinhaltet. Im Gegensatz zu herkömmlichen Grundwassermodellen für Frischwasser erfordern großmaßstäbliche Simulationen des gekoppelten Fluidflusses, Massen- und Wärmetransfers ein angepasstes Fluiddichtemodell. Feldmessungen des Fluidporendrucks und der Fluidtemperaturen sowie Laborexperimente zu Lösungsgehalten liefern die in das Modell eingehenden Dichtedaten. Die Salzwasserschichtung ist im tieferen Untergrund instabil, was darauf hinweist, dass das Auftreten konvektiver Ströme sehr wahrscheinlich ist.Die Gleichungen des dichtegesteuerten Fluidflusses wurden mithilfe der Finite-Elemente-Software FEFLOW 5 ® gelöst. Der numerische Ansatz der thermohalinen Simulation umfasst Tests verschiedener Gitterauflösungen. Das 2D-Modell erlaubt die Quantifizierung der Interaktionen zwischen diffusem Lösungstransport und thermisch sowie druckhöhegesteuertem Fluidfluss (gezwungene versus freie Konvektion) ...thesi

Thermische Eigenschaften Gashydratführender Sedimente und Einflüsse von Phasenübergängen auf den Wärmetransport Abgeleitet Anhand von Bohrlochtemperaturmessungen in Mallik, NWT, Kanada

Um Prozesse im Zusammenhang mit der Bildung und der Zersetzung von Gashydraten in der Natur quantifizieren zu können, ist eine detaillierte Kenntnis der thermischen Eigenschaften von gashydratführenden Gesteinen notwendig. Diese Arbeit untersucht den Einfluss von Methanhydrat auf den Wärmetransport in porösen Gesteinen. Sowohl die Wärmeleitfähigkeit gashydratführender Sedimente als auch der Einfluss von Phasenübergängen wird untersucht. Im Rahmen des Mallik 2002 Forschungsbohrprogramms wurden drei Bohrungen, die ein kontinentales Gashydratvorkommen unter Permafrost durchteufen, erfolgreich mit faseroptischen Messkabeln zur ortsverteilten Temperaturmessung ausgestattet. Über einen Zeitraum von 21 Monaten nach der Fertigstellung der Bohrungen wurden Temperaturmessungen durchgeführt. Die Auswertung der durch den Bohrprozess verursachten Temperaturstörungen zeigt einen starken Einfluss von Phasenübergängen auf Temperaturänderungen. Erstmals wurden die Auswirkungen einer künstlich induzierten Temperaturänderung innerhalb eines natürlichen Gashydratvorkommens in situ beobachtet. Die hierdurch verursachten Anomalien des Temperaturgradienten wurden erfolgreich zur Bestimmung der Basis der Gashydratvor-kommen und des Permafrosts herangezogen, die jeweils bei rund 1103-1104±3.5 m, bzw. 599-604±3.5 m unterhalb der Geländeoberkante liegen. Am Ende des 21-monatigen Beobachtungszeitraumes hat sich die Bohrlochtemperatur weitgehend der Formationstemperatur angeglichen. An der Basis der Gashydratvorkommen wurde eine Temperatur von 12.3 °C bestimmt. Dieser Wert liegt rund 0.7 °C unter der von thermodynamischen Berechnungen vorhergesagten Stabilitätstemperatur, wenn man von ei-nem Druckgradienten von 10.12 kPa/m und einer Salinität des Porenwassers von 35 ppt ausgeht. Unter den angegebenen Bedingungen liegt die Grenze des Stabilitätsbereichs von Methanhydrat bei ungefähr 1140 m unter Gelände. Profile der Wärmeleitfähigkeit wurden sowohl aus geothermischen Daten als auch aus einem petrophysikalischen Modell, welches aus den vorliegenden Bohrlochmessdaten abgeleitet wurde, und der Anwendung von Mischungsgesetzmodellen berechnet. Die Ergebnisse weisen darauf hin, dass Veränderungen der Wärmeleitfähigkeit im Wesentlichen durch litho-logische Wechsel verursacht werden. Der Einfluss der Hydratsättigung ist nur von untergeordneter Bedeutung für die effektive Wärmeleitfähigkeit des Gesteins. Die Ergebnisse des geometrischen Mittel Modells stimmen am besten mit den Wärmeleitfähigkeitsprofilen, die aus geothermischen Daten abgeleitet wurden, überein. Mittlere Werte der Wärmeleitfähigkeit der hydratführenden Intervalle liegen zwischen 2.35 W/m*K und 2.77 W/m*K. Ein vereinfachtes numerisches Modell für konduktiven Wärmetransport wurde eingesetzt, um den Temperatureffekt von Phasenübergängen in den gashydrathaltigen Schichten zu berechnen. Das Modell beinhaltet die Umsetzung latenter Wärme während des Phasenübergangs (Enthalpie-Methode); Weiterhin wurden die Stabilitätsbedingungen für Methanhydrat in Mallik (Druck, Temperatur, Zusammensetzung des Porenwassers und der Gasphase) und der Ein-fluss der Zersetzung von Hydrat auf die thermischen Gesteinseigenschaften berücksichtigt. Die Modellergebnisse deuten darauf hin, dass die Neubildung von Hydrat nach Wiedererlan-gen der Stabilitätsbedingungen gehemmt ist.Detailed knowledge about the thermal properties of rocks containing gas hydrate is required in order to quantify processes involving the formation and decomposition of gas hydrate in nature. This work investigates the influence of methane hydrate on the transport of heat in hydrate-bearing rocks. Both the thermal conductivity of gas-hydrate bearing sediments and the thermal effects of phase transitions are analyzed. In the framework of the Mallik 2002 program three wells penetrating a continental gas hydrate occurrence under permafrost were successfully equipped with permanent fiber-optic distributed temperature sensing cables. Temperature data were collected over a period of 21 months after completion of the wells. The analysis of the disturbed well temperatures after drilling revealed a strong effect of phase transitions on temperature changes. For the first time, the effects of induced temperature changes within a gas hydrate deposit were monitored in-situ. The resulting temperature gradient anomalies could be successfully utilized to determine the base of the gas hydrate occurrences and the permafrost layer at about 1103-1104±3.5 m and 599-604±3.5 m below ground level respectively. At the end of the 21-month observation period, the well temperature returned close to equilibrium with the formation temperature. At the base of the gas hydrate occurrences a temperature of 12.3 °C was measured, which is about 0.7 K below the stability temperature predicted by thermodynamic calculations considering a pressure gradient of 10.12 kPa/m and a sea-water salinity of 35 ppt. Under the stated conditions, the base of the stability zone of methane hydrate at Mallik would lie at about 1140 m below ground level. Thermal conductivity profiles were calculated from the geothermal data as well as from a petrophysical model derived from the available logging data and application of mixing-law models. The results indicate, that variations of thermal conductivity are mainly lithologically controlled with a minor influence from hydrate saturation. The results of the geometric mean model showed the best agreement to the thermal conductivity profiles derived from geothermal data. Average thermal conductivity values of the hydrate-bearing intervals range between 2.35 W/m*K and 2.77 W/m*K. A simplified numerical model of conductive heat flow was set up in order to assess the temperature effect of phase transitions within the gas hydrate bearing strata. Within the model the mobilization of latent heat during the phase transition was considered (enthalpy method), taking into account the stability conditions for methane hydrate at Mallik (pressure, temperature, pore fluid and gas phase composition) as well as effects of hydrate decomposition on the thermal rock properties. The modelling results indicate, that the regeneration of hydrate after the recovery of stability conditions is inhibited

Wireline distributed acoustic sensing allows 4.2 km deep vertical seismic profiling of the Rotliegend 150 °C geothermal reservoir in the North German Basin

We performed so-far-unprecedented deep wireline vertical seismic profiling at the Groß Schönebeck site with the novel method of distributed acoustic sensing (DAS) to gain more detailed information on the structural setting and geometry of the geothermal reservoir, which is comprised of volcanic rocks and sediments of Lower Permian age. During the survey of 4 d only, we acquired data for 61 source positions using hybrid wireline fiber-optic sensor cables deployed in two 4.3 km deep, already existing wells. While most of the recorded data have a very good signal-to-noise ratio, individual sections of the profiles are affected by characteristic coherent noise patterns. This ringing noise results from incomplete coupling of the sensor cable to the borehole wall, and it can be suppressed to a large extent using suitable filtering methods. After conversion to strain rate, the DAS data exhibit a high similarity to the vertical component data of a conventional borehole geophone. We derived accurate time–depth relationships, interval velocities, and corridor stacks from the recorded data. Based on integration with other well data and geological information, we show that the top of a porous and permeable sandstone interval of the geothermal reservoir can be identified by a positive reflection event. Overall, the sequence of reflection events shows a different character for both wells explained by lateral changes in lithology. The top of the volcanic rocks has a somewhat different seismic response in both wells, and no clear reflection event is obvious at the postulated base of the volcanic rocks, so that their thickness cannot be inferred from individual reflection events in the seismic data alone. The DAS method enabled measurements at elevated temperatures up to 150 ∘C over extended periods and led to significant time and cost savings compared to deployment of a conventional borehole geophone string. This wireline approach finally suggests significant implications for observation options in old wells for a variety of purposes.BMWi, 0324065 TIB, Rissdominierte Erschließung eines tiefen geothermischen Reservoirs zur Stromerzeugung im Norddeutschen Becken - seismische Erkundung, Konzeption und bohrtechnische Planung am Standort Groß SchönebeckEC/H2020/691728/EU/Demonstration of soft stimulation treatments of geothermal reservoirs/DESTRESSEC/H2020/676564/EU/EPOS Implementation Phase/EPOS I

Drilling and Abandonment Preparation of CO2 storage wells – Experience from the Ketzin pilot site

AbstractAt Ketzin, located west of Berlin, the GFZ German Centre for Geosciences is operating Europe's largest CO2 research storage site. This pilot site has been developed since 2004 and is comprised of one combined injection/observation well and four monitoring wells. From June 2008 to August 2013, a total of 67 kilotons of CO2 were safely injected into the sandstone units of the Upper Triassic Stuttgart Formation in a depth between 630 to 650 m. The paper discusses the well designs and lessons learned in drilling engineering and operations. The abandonment phase started in Ketzin with the first plug cementation of the observation well Ktzi 202 shortly after shut-in of CO2 injection. The experience with the first CO2 well killing operation will be reviewed

Cable reverberations during wireline distributed acoustic sensing measurements: their nature and methods for elimination

The application of distributed acoustic sensing in borehole measurements allows for the use of fibre optic cables to measure strain. This is more efficient in terms of time and costs compared with the deploying of conventional borehole seismometers. Nevertheless, one known drawback for temporary deployment is represented by the freely hanging wireline cable slapping and ringing inside the casing, which introduces additional coherent coupling noise to the data. The present study proposes an explanation for the mechanism of noise generation and draws an analogy with similar wave propagation processes and phenomena, such as ghost waves in marine seismics. This observation allows to derive a ringing noise filter function, to study its behaviour and to consider known effects of the gauge length filter. After examining existing methods aimed at eliminating ringing noise and results of their application, we propose a two‐step approach: (1) developing a denoising method based on a matching pursuit decomposition with Gabor atoms and (2) subtracting the noise model for imaging improvement. The matching pursuit method focuses on decomposing the original input signal into a weighted sum of Gabor functions. Analysing Gabor atoms properties for frequency, amplitude and position in time provides the opportunity to distinguish parts of the original signal denoting noise caused by the vibrating cable. The matching pursuit decomposition applied to the distributed acoustic sensing‐vertical seismic profiling data at the geothermal test site Groß Schönebeck provides a versatile processing instrument for noise suppression.German Federal Ministry of Economic Affairs and Energ

Reservoir Behaviour and Borehole Processes during EGS Operation: Experiences From Three Years of Production and Injection at the Groß Schönebeck Site

ABSTRACT At the Groß Schönebeck site, Germany, an Enhanced Geothermal System (EGS) has been created in Lower Permian (Rotliegend) volcanic and sedimentary rocks. Short-term production tests have shown success of the applied hydraulic stimulation treatments, with an up to 6-fold increase of the initial productivity. Until 2013, extensive circulation tests were carried out with a cumulative production volume of approx. 20.000 m³. A non-linear trend towards lower productivities is observed. Production logging revealed that inflow from the main production zone is variable, explaining short-term changes in productivity. Additionally over time, an obstruction of the well at successively shallower depths was observed. Downhole sampling showed that the well was clogged with scales, mainly comprised of variable amounts of native copper (up to 50 wt%), laurionite and barite. After a partial clean-out of the well the accessible depth of the well could be increased again, allowing for an inspection of the well liner in the perforation interval. Average metal losses in the order of 7-12 % have been observed. This is in accordance with a geochemical model for the formation of the copper scaling, enabling to unmask the original mineralization of the formation fluid. The results up to now clearly show the challenges related to utilization of this potentially vast geothermal resource in Central Europe, and the need for further research: The initial increase of productivity gained through stimulation treatments was not sustainable. As possible mechanisms of permeability reduction, the formation of a free gas phase by degassing of formation fluid, clogging of pores by copper scales, and impairment of the hydraulic fractures were identified. The observed scaling revealed a previously unquantified composition of the geothermal brines of Rotliegend reservoirs in the North-East German Basin, asking for modified well completion or water treatment concepts

CHENILLE : Coupled beHaviour undErstaNdIng of fauLts : from the Laboratory to the fiEld

International audience<p>The understanding of the coupled thermo-hydro-mechanical behaviour of fault zones is of fundamental importance for a variety of societal and economic reasons, such as the sustainable energy transition for the safe use of natural resources (energy storage, nuclear waste disposal or geothermal energy). The overall objective of this inter-disciplinary project is to create a dataset that will allow to highlight the physical processes resulting from a thermal and hydric load on an existing, identified and characterized fault zone.</p><p> </p><p>An in situ experiment will be performed at IRSN’s Tournemire Underground Research Laboratory to evaluate the hydraulic properties and mechanical behaviour of a fault zone in a shale formation due to an increase of gas or water pressure under incremental thermal loading. This fracturing field tests will be conducted using four types of boreholes drilled from the URL : (i) one injection borehole (INJ) with one chamber measuring 10 m in length; (ii) four boreholes (H1 to H4) dedicated to host steel canister electrical heaters, (iii) 5 boreholes (S1 to S5) dedicated to the geophysical monitoring of seismic and aseismic fracturing processes, (iv) two to four boreholes (M1 to M4) to record deformation and estimate fracture location, which will help assess the seismic survey. After an initial saturation phase of the chamber, successive sequences of fluid injection tests are planned. The preliminary injection tests will be done stepwise either at constant flow or at constant pressure rate in order to obtain a steady-state flow regime at normal in situ temperatures. The hydraulic conductivity and permeability of the fault zone will be then inferred. A second stage of hydraulic testing will involve the determination of the main hydraulic parameters during a stepwise increase of temperature within the volume (maximum temperature 150°C). In the meantime, the seismological responses of the injected structures, from the static deformation to the high-frequency (100-kHz) acoustic emissions will be surveyed. The evolution of temperature and deformation will be monitored thanks to fibre optic array. In addition, a controlled seismic experiment is proposed, using coupled magnetostrictive vibrators to investigate the structural environment before and after experiment.</p><p> </p><p>Moreover, to accompany the field study, a series of laboratory experiments will be conducted to understand the chemical and structural evolution occurring within fault zones during the thermal and hydraulic loading. Experiments in climatic chambers exposing the samples to the same heat treatment as that of the in situ experiment will be carried out in order to compare the mineralogical composition evolution of the samples with those taken from the field investigated zone. Finally, a rock mechanical study, from the microscopic to the centimeter scale with monitoring of the acoustic properties will be carried out. This study will include experiments from Scanning Electron Microscope with Energy Dispersive Spectroscopy (SEM-EDS) allowing the identification of the micro-scale mechanisms of deformation localization to which it is planned to add an acoustic measurement system. In order to study the evolution of mechanical behaviour as a function of scale, experiments in triaxial press, again with acoustic monitoring, are planned.</p&gt