Sustainable Design of Energy Systems - The Case of Geothermal Energy

Geothermal energy is one of the renewable energy resources with a vast potential. It is extended spatially in many areas, isolated from urban areas and direct uses, whereas its utilisation when it is not for electricity production is many times hampered due to lack of a proper development framework. In this work we present a design framework for sustainable geothermal systems incorporating modules covering the various aspects of exploration, utilisation, end-use and management. The overall framework consists of the following sub modules: a. geophysical model of the assessment of the geothermal reservoir capacity b. model for the management of the geothermal wells, pumping and re-injection c. model for the distribution network d. model for the various end-uses, e. environmental model for sustainable operation The overall framework incorporates the basic axes of sustainable development, i.e. resources, economy, environment, energy, technology, society. The theoretical framework is applied to an existing geothermal reservoir which at the current is being underutilized, from an energy, environmental and economic perspective. The search for an optimum design includes the formulation of different scenarios and the multi-criteria decision analysis of them.

Montana Bureau of Mines and Geology

The Montana Bureau of Mines and Geology is the principal source of earth science information for the citizens of Montana. The bureau provides extensive advisory, technical, and informational services on geologic, mineral, energy, and water resources in the state of Montana. This includes earthquake studies, environmental assessment, Geographic Information Services (GIS), geology and minerals, groundwater, mines information, coal, state mapping, and more. The publications database contains all Bureau publications as well as U.S. Geological Survey publications related to Montana geology. Educational levels: Graduate or professional, Undergraduate lower division, Undergraduate upper division

The eruptive history and magmatic evolution of Aluto volcano: new insights into silicic peralkaline volcanism in the Ethiopian rift

The silicic peralkaline volcanoes of the East African Rift are some of the least studied volcanoes on Earth. Here we bring together new constraints from fieldwork, remote sensing, geochronology and geochemistry to present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in a densely populated section of the Main Ethiopian Rift. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at 316 ± 19 ka and 306 ± 12 ka developing a ~ 42 km2 collapse structure. After a hiatus of ~ 250 ka, a phase of post-caldera volcanism initiated at 55 ± 19 ka and the most recent eruption of Aluto has a radiocarbon age of 0.40 ± 0.05 cal. ka BP. During this post-caldera phase highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (> 80%) of basalt that is compositionally similar to rift-related basalts found east of the complex. Based on the style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement of localised pumice cones and effusive obsidian coulees of volumes in the range 1–100 × 106 m3

Tracer Applications of Noble Gas Radionuclides in the Geosciences

The noble gas radionuclides, including 81Kr (half-life = 229,000 yr), 85Kr (11 yr), and 39Ar (269 yr), possess nearly ideal chemical and physical properties for studies of earth and environmental processes. Recent advances in Atom Trap Trace Analysis (ATTA), a laser-based atom counting method, have enabled routine measurements of the radiokrypton isotopes, as well as the demonstration of the ability to measure 39Ar in environmental samples. Here we provide an overview of the ATTA technique, and a survey of recent progress made in several laboratories worldwide. We review the application of noble gas radionuclides in the geosciences and discuss how ATTA can help advance these fields, specifically determination of groundwater residence times using 81Kr, 85Kr, and 39Ar; dating old glacial ice using 81Kr; and an 39Ar survey of the main water masses of the oceans, to study circulation pathways and estimate mean residence times. Other scientific questions involving deeper circulation of fluids in the Earth's crust and mantle also are within the scope of future applications. We conclude that the geoscience community would greatly benefit from an ATTA facility dedicated to this field, with instrumentation for routine measurements, as well as for research on further development of ATTA methods

Fluid flow near reservoir lakes inferred from the spatial and temporal analysis of the electric potential

Electric self-potential (SP) variations have been monitored continuously from 1995 to 1998 at 14 points on a ridge separating the Roselend and La Gittaz reservoir lakes in the French Alps. The lakes have level variations of at least 50 m over yearly cycles. Seasonal variations of SP associated with lake-level variations are observed on five points of the array. For three points located on the banks of the lakes, a positive correlation to the lake-level variations is observed with a maximal amplitude of about 180 mV, corresponding to an average response of 2.4 mV per meter of water. For two points located on the bottom of each lake, the correlation is negative, with a maximal magnitude of about −50 mV, corresponding to an average response of −1.1 mV per meter of water. Two independent temporary electrical arrays located on the banks of each lake confirm these measurements and allow a better spatial characterization of the sources associated with the observed SP variations. In particular, near the Roselend lake, the electrical response to lake-level variations is increasing for decreasing altitude. The measured SP variations are proposed to result from the electrokinetic coupling associated with a vertical groundwater flow connecting a constant pore pressure source to the bottom of the lakes. Numerical modeling indicates that the spatial variation of the response and the nonlinear response observed at one point can be explained by leakage currents in the conductive lake water. The values of the streaming potential coefficient (SPC), measured in the laboratory with crushed rock samples from the site, range from 14 to 50 mV/0.1 MPa for an electrolyte resistivity of 40 Ω m and are compatible, to first order, with the magnitude of the observed seasonal SP variations. A detailed quantitative electrokinetic modeling is currently limited mainly by the poor knowledge on the contribution of electrical leakage currents and the local variability of the SPC. This experiment indicates that spatial and temporal variations of the electric potential are promising tools to characterize and monitor shallow groundwater flow and provide practical data for the investigation of groundwater flow associated with volcanic or tectonic activity

Scientific basis for safely shutting in the Macondo Well after the April 20, 2010 Deepwater Horizon blowout

As part of the government response to the Deepwater Horizon blowout, a Well Integrity Team evaluated the geologic hazards of shutting in the Macondo Well at the seafloor and determined the conditions under which it could safely be undertaken. Of particular concern was the possibility that, under the anticipated high shut-in pressures, oil could leak out of the well casing below the seafloor. Such a leak could lead to new geologic pathways for hydrocarbon release to the Gulf of Mexico. Evaluating this hazard required analyses of 2D and 3D seismic surveys, seafloor bathymetry, sediment properties, geophysical well logs, and drilling data to assess the geological, hydrological, and geomechanical conditions around the Macondo Well. After the well was successfully capped and shut in on July 15, 2010, a variety of monitoring activities were used to assess subsurface well integrity. These activities included acquisition of wellhead pressure data, marine multichannel seismic pro- files, seafloor and water-column sonar surveys, and wellhead visual/acoustic monitoring. These data showed that the Macondo Well was not leaking after shut in, and therefore, it could remain safely shut until reservoir pressures were suppressed (killed) with heavy drilling mud and the well was sealed with cement

The 3D Attenuation Structure of Deception Island (Antarctica)

Peer reviewedPostprin

Synthetic aperture in controlled source electromagnetic for the monitoring and exploration of reservoirs on land

Abstract: The following doctoral thesis is composed of five scientific papers, structured in three chapters. Three of these papers are already published in international journals, and two are currently under review. According to the stated objectives in this work, these chapters are grouped into two general sections, namely: Section I. Golden zone of sedimentary basins in the Colombian territory; Section II. Exploration of reservoirs on land using electromagnetic methods.Resumen: La primera parte de esta tesis identifica la Zona Dorada en algunas cuencas sedimentarias de Colombia por medio de anomalías magnéticas. En la segunda parte se realiza modelamientos directos 3D de los métodos de apertura sintética en fuente controlada electromagnética y multitransiente electromagnética para la exploración de reservorios sobre tierra.Doctorad

Advances in the Exploration of Geothermal Resources of the East Africa Rift System (EARS)

This work focuses on the geological, geophysical and geochemical exploration of the geothermal reservoirs located in the East Africa Rift System (EARS), with particular reference to the characterisation of some geothermal fields located in Ethiopia, Kenya, Tanzania and Malawi. Moreover, this study provides an updated overview of the procedures for the exploration of geothermal resources and can serve therefore as a best-practice guide for future endeavours. Field activities included geological surveys, geophysical investigations (gravity, electromagnetic and seismic measurements) and geochemical survey/analyses. Moreover, stratigraphic data and P&T logs were available at some explored geothermal prospects. An overview of the main investigated geothermal fields was given and three case studies were described in detail as representative examples of geothermal play types of EARS: (i) the Alalobeda field (Ethiopia), located in correspondence of the triple junction Read Sea-Aden Gulf-Main Ethiopian Rift and (ii) the Kiejo-Mbaka field (Tanzania), belonging to EARS\u2019 western branch, both falling in the extensional domain play type, fault controlled or fault-leakage controlled; (iii) the Menengai field (Kenya), the second most important geothermal field in EARS, where a huge quantity of direct data from more than twenty drilled wells is available. The latter can be classified as convection-dominated magmatic play type. Compared to geothermal fields of South-East Asia and Central America, the geothermal of EARS presents some peculiar characters and differences. The plutonic play-type (convection dominated), occurring in fore- or back-arc regions of fold-thrust belts along subduction zones, denotes a well-developed thick and continuous cap rock mainly formed by clay minerals. In the plutonic play of Menengai, the typical impermeable cap rock is practically missing. A \u201czonation\u201d of the play types occurring in EARS can be recognized. The Western Branch is characterised by the presence of fault/fault-leakage controlled play types. In the Eastern Branch, geothermal plays are associated to active or quite recent volcanoes. Due to the foregoing characters, a different approach should be followed in order to characterize properly the geothermal fields present in EARS. In a subduction context, geophysical results from electromagnetic investigations play a fundamental role in the exploration of potential geothermal reservoirs, as in such an environment they are often succesfully used to detect the occurrence of an impermeable cap rock overlying the reservoir (target zone). Therefore, if the resistivity structures inferred in EARS geothermal plays are simply associated with \u201cstandard\u201d resistivity models of cap rock-reservoir formations, the inferred geophysical conceptual model may be grossly incorrect. Wherefore, an accurate and integrated interpretation of all the geoscientific data is essential. In this regard, a detailed structural survey is of primary importance especially in the fault-controlled plays, whereas its importance is often under-estimated in subduction realms. A high-resolution structural survey allows to define a detailed configuration of fractures and faults that may control the fluid upflow from the reservoir. Concerning the application of geochemical methods, in EARS, typical approaches and models developed in the subduction geothermal systems should be re-evaluated. The high-temperature geothermal reservoirs of the Eastern branch (e.g., Olkaria and Menengai in Kenya, and Aluto-Langano in Ethiopia) host not only mature chloride waters, as the geothermal systems situated along subduction zones, but also mature bicarbonate-chloride and mature bicarbonate waters. In volcanic-magmatic regions, deep geothermal liquids are assumed to be produced through neutralization of initially acidic meteoric-magmatic aqueous solutions. The few available data for volcanic gases indicate that subduction zones volcanic gases are enriched in Cl relative to hot-spot and divergent-plate volcanic gases. Therefore, the comparatively small supply of Cl-bearing magmatic gas species (chiefly HCl) in the root of the Eastern EARS geothermal systems might be responsible for the comparatively low Cl contents of related geothermal liquids. The situation might be even more complicated in the western EARS, due to the absence of magmatic systems. Therefore, a more comprehensive approach to water classification is needed to distinguish mature waters from immature ones. In view of the differences with the geothermal systems hosted in subduction zone environments, the future exploration and development of geothermal resources of EARS should thus consider that geothermal resources are rarely due to the presence of a hot magmatic source, but rather to the crustal thinning, which determines thermal anomalies of moderate intensity. Moreover, favorable thermal conditions are not always accompanied by an adequate hydrogeological setting, expecially when they occur in low permeability basalts. In these cases, it is essential to pay attention to the structural setting, in order to design the wells with the highest likelihood of intersecting permeable tectonic structures. Unlike in most Indonesian fields, where permeability tends to be widespread throughout the rock, in the EARS permeability appears in many cases limited to major faults. The planned program of drilling in several prospects of Ethiopia and Tanzania will make available further information improving the overall understanding of the geothermal characteristics of EARS