Geothermal Energy

Graduate Students Master's Thesis 2009 The reports are not to be duplicated or printed without written consent by the author and RES. Aluminum Alloy Drill Pipe in Geothermal Drilling [PDF] Technical and Economical Opportunities © Erin Rebecca Anderson (Geothermal Energy Specialization) Abstract The purpose of this investigation is to determine the application opportunities of aluminum alloy drill pipe (ADP) in geothermal drilling environments. The Geothermal Energy industry is at the tipping point of the global energy mix. Geothermal offers the benefits of other clean, sustainable energies such as low emissions but also boasts a small environmental footprint, base-load power, and widespread distribution as related to EGS applications. Additionally, with the improved development into ultra high energy extraction regions, the geothermal drilling industry is under high demand and is being tested to drill deeper, faster, and at reduced costs in order to make geothermal competitive economically and to satisfy energy demands. The achievement of greater drilling depths requires the advancement of the drilling industry to address limitations in the weight capacity of the drill rigs and the temperature limitations of the drilling components. Aluminum alloy drill pipes (ADP), sometimes referred to as Lightweight Aluminum Drill pipes (LADP) have been used in the drilling industry in Russia for many years. Due to ADP’s lightweight and high strength to weight ratio there are several advantages over conventional steel pipe. These advantages include the use of larger diameter drill pipe with thicker walls which increase annular flow; reduced pressure loss inside the drill pipe, resulting in smaller pump requirements; reduced derrick loads and hook loads due to reduced weight per length compared to steel and increased buoyancy effects in drilling fluids, resulting in smaller rigs or greater depth penetrations with current rigs; and reduced stresses in a number of drilling design parameters. The application ranges of ADP utilization will be studied in regards to temperature limitations, critical buckling loads and strength of materials, geothermal fluid chemistry, drilling fluid pressure losses and hydraulics, load comparisons, tool joint bonding, and economical cost analysis. Exploration of Geothermal Systems with Petrel Modeling Software [PDF] © Dorottya Bartucz (Geothermal Energy Specialization) Abstract In this thesis work an area located in Hungary was examined in order to localize the most promising site for geothermal water extraction for use in electricity production or in direct heat utilization systems. Hungary is located in the central part of the Pannonian Basin. The geological evolution of the basin was favorable for the formation of low- and medium-enthalpy geothermal reservoirs throughout the country. These resources are already used in the balneology and agriculture sector. The utilization of the natural hot water in district heating systems and for domestic hot water supply has been developing fast in the recent years, while electricity generation from geothermal water is still in research phase. A three-dimensional (3D) digital geological model of the area was created to support the localization of the best prospective site in the area of interest. For the model’s construction, eighteen two-dimensional (2D) seismic sections were used as input data. The Petrel geological modeling software, which was developed by Schlumberger Co, was used for data processing. Three promising sites were designated in the studied area. Those sites were selected where the old deep and young shallower fractured zones cross each other by creating a locally extensional stress field. Due to the difficulties of the interpretation process the presence of the before mentioned requirements are very likely, but not certain, in the designated areas. Further exploration is crucial. A comparison made between the computer supported analysis and the manual interpretation of hard copies of the seismic sections revealed that computer aided interpretation process lead to the recognition of more detailed tectonic structures in a relatively shorter time interval. 3D Modeling of Geothermal Reservoirs [PDF] Case Study from Subtatric Basin in Western Carpathians, Slovakia © Lucia Hlavácová (Geothermal Energy Specialization) Geothermal energy is a potential renewable energy source that should be taken into account by the Slovak government. To aid geothermal exploration, 3D modeling is a very useful tool. The objective of this project was to model Poprad basin and the northern part of Hornad basin, in the Inner Carpathian system in Slovakia, to assess future prospective geothermal areas. These two are considered active geothermal areas. The main aquifers are built by Triassic carbonates – dolomites and limestones of Choc and Krizna nappe. In the central part of the Poprad basin, on the basis of seismic interpretation, Choc nappe thicknesses from 200 to 1100 m were obtained. Larger nappe thicknesses from 1200 to 1500 m were obtained on the east and southeast part of the studied area. The average value of the temperature gradient reaches 32.6 – 34.5° C/km and the average value of the heat flow density was estimated on 67mW/m2. Temperatures on the top of the Pre-Paleogene basement reach 50 – 85° C. In this work the geologic structure of the Gerlachov area, which is situated in the northwestern part of Poprad Basin, was also interpreted. From a geothermal point of view the formations with the most potential are Mesozoic units represented by Choc and Krizna Nappes underlying Paleogene rocks. Based on the geologic composition of Choc Nappe, the existence of very good conditions for a geothermal water reservoir can be expected. Krizna Nappe has less positive conditions for geothermal waters exploitation. General discharge of groundwater in Choc Nappe should be more than 22 l.s-1. The temperature in Choc Nappe is between 35 and 45° C. Risk Management and Contingency Planning for Well IDDP-1 [PDF] © Sebastian Homuth (Geothermal Energy Specialization) Abstract The Icelandic Deep Drilling Project (IDDP) is a research program designed to evaluate improvements in the efficiency and economics of geothermal energy systems by harnessing Deep Unconventional Geothermal Resources (DUGR). The goal is to generate electricity from natural supercritical hydrous geofluids from depths of around 3.5 to 5 km and temperatures of 450-600°C. At that depth, the pressure and temperature of pure water exceed the critical point of 374.15°C and 221.2 bars, which means that only a single phase fluid exists. In order to drill into the target zone of supercritical geofluids, one of the main challenges is to deal with high temperatures and pressures during the drilling and well completion processes. Because of the great uncertainties in this project a detailed risk assessment and contingency plan is necessary. This thesis describes major geological and technical problems, in terms of drilling, in such a high temperature and pressure environment, with emphasis on the geo-engineering part of the drilling process and well completion. The natural geological risks arising from volcanic and seismic activity, as well as meeting sufficient permeable zones, are considered to be relatively minor factors when compared to the well completion process due to their low probability. The main risks are assessed in the hazard of underground pressure blowouts, meeting circulation loss zones and material failures due to the high temperature environment. In addition borehole failure, formation fracturing, cement and casing failure as well as problems during coring operations are deemed to be likely, but by applying the appropriate techniques as well as mitigation and counteractive measures, discussed in this thesis, most of these risks can be reduced or prevented. Þeistareykir high-temperature geothermal field, North-East Iceland [PDF] Estimation of reservoir conditions and evaluation of pressure interference between wells © Júlía Úlfdís Jóhannsson (Geothermal Energy Specialization) Abstract The Þeistareykir high-temperature geothermal field is located in northern Iceland. Seven deep boreholes have been drilled there since 2002. Temperature and pressure logs, measured during different operational stages of the wells, were analyzed to estimate formation temperature and initial pressure, as well as the possible location of feed zones in the wells. A new interpretation supports the hypothesis of an up-flow around well ÞG-1. It is possible that the up-flow does not spread as far to the west as was previously assumed. The highest temperatures measured in the new wells ÞG-5B and ÞG-6 were 300°C and 311°C, respectively. The discharge enthalpy for well ÞG-5B is higher than it is for well ÞG-5. Discharge from well ÞG-6 will possibly have similar characteristics as the discharge from wells ÞG-1 and ÞG-3, i.e. high temperature steam. Pressure recovery measurements in wells, which were shut in during the summer of 2008, have been evaluated using conventional well test analysis methods. The results obtained were compared with results of the interpretation of step-rate injection test data. Transmissivities evaluated in this work for wells ÞG-1 and ÞG-3 are lower than previous estimates while skin factor estimates have become more negative. Transmissivity, estimated by the analysis of injection test data for well ÞG-5B is close to the transmissivity estimated for well ÞG-5, or in the order of 7x10-8 m3/Pa-s; transmissivity, estimated for well ÞG-6 is close to the transmissivity for well ÞG-3, and in the order of 1.3 x10-8 m3/Pa-s. There are indications of interference between well ÞG-2 and wells ÞG-3, ÞG-5, ÞG-5B, and ÞG-6, as well as between ÞG-3 and ÞG-5. Well ÞG-1 has a limited communication with wells ÞG-2 and ÞG-3, however. 3D Modeling of a Geothermal Reservoir in the Central Part of Kosice Basin in the Eastern Slovakia [PDF] © Katarína Kamenská (Geothermal Energy Specialization) Abstract The question of energy needed for enhancing human comfort has recently become very popular and geothermal energy, as one of the most promising renewable energy sources, has started to be utilized not only for recreation purposes, but also for heating and probably electricity generation in Slovakia. Slovakia is a country which has proper geological conditions for geothermal source occurrence. Kosice Basin seems to be the most prospective geothermal area – the reservoir rocks are Middle Triassic dolomites with fissure karstic permeability and basal Karpathian clastic rocks at the depth of 2100 – 2600 m, with an average temperature around 135 °C. Seismic data from the central part of Kosice basin enabled the demonstration of position, spatial distribution, morphology and tectonic structure of reservoir rocks and their Neogene overlier as an insulator. Based on a 3D tectonic model, reservoir rocks are segmented into individual blocks which probably do not communicate with surrounding blocks in terms of geothermal water flow. Tectonic and geologic aspects affect the thickness of sedimentary sequences, which is demonstrated by variable thickness in the whole space of the modeled area. The model showed at least one potential geothermal area, but for further evaluation detailed geophysical measurements are needed. Geothermal sources in central Kosice Basin as a home source can reduce dependence on gas and other fossil fuels. Utilization of geothermal sources can secure energy supply for Kosice town and prevent future shortages in energy as happened in January 2008 when Russia cut gas supply to part of Europe, including Slovakia. Geothermal utilization produces much less greenhouse gasses as conventional fossil fuel plants and in the case of reinjection there is no emission to the atmosphere. Probably the biggest disadvantage of geothermal utilization in the area of interest is high capital cost. Feasibility study of binary geothermal power plants in Eastern Slovakia [PDF] Analysis of ORC and Kalina power plants © Martina Kopuničová (Geothermal Energy Specialization) Abstract Slovakia is among the countries of the European Union which signed the regulation related to renewable energy source utilization. According to European Union statistics from 2005, Slovakia is number 22 in terms of renewable energy usage, with 6.7% of its energy from renewable sources. The regulation states that by the year 2020, Slovakia must increase its usage to 14%, which means doubling the renewable fraction of total energy consumption. Slovakia is one of the countries in central Europe with high geothermal resources occurrence which are not used sufficiently. The disadvantage of these sources is a low temperature. These low temperature sources can be used directly for district heating or to produce electrical power. For low temperature source utilization the most applicable power generation is using small binary power plants - Organic Rankine Cycle (ORC) or Kalina cycle. The aim of this work is to model the ORC and Kalina cycle using data obtained from East Slovakian sources and to compare these two systems in terms of efficiency, power output, usability in Slovakian conditions and financial feasability. The largest source in Eastern Slovakia is located in a placed near Kosice city – Durkov. (Giese, 1998) Results of the modeled thermodynamical comparison show that the Kalina cycle is more feasible in Durkov area conditions. Looking at the basic investments analysis the decision of which modeled power plant is better is a complicated one to make. A New Geothermal Cooling – Heating System for Buildings [PDF] Geothermal Cooling – Heating for Hot – Humid Climates © Pawel Jan Lech (Geothermal Energy Specialization) Abstract Single stage absorption chillers (water/lithium bromide) can operate using low grade heat, thus single stage absorption chillers can operate using low temperature geothermal resources. An EES computer model was written for a single stage absorption chiller based on overall heat transfer coefficients, mass flows, salt balances, energy balances and other assumptions. The single stage model was calibrated with well known and available data from US and Japanese manufacturers. The system was considered to work in hot and humid climates like those in Abu Dhabi and Shanghai. The results show that when cooling water is 28 °C hot the initial and annual total cost is high. However, as cooling water temperature decreases, the initial and annual total cost decreases sharply (when cooling water is at 20°C the reduction is around 35% of the total annual cost). The results show a great influence of cold and hot water on the performance and total annual cost of absorption chillers. The second part of the computer model contains a Total Equivalent Warming Impact (TEWI) analysis. TEWI considers both the direct refrigerant effects and the primary energy impact on equivalent carbon dioxide (CO2) emissions. Competing technologies are vapour–compression and gas cycles. The results show some recommendations for absorption system diversification to reduce the Total Equivalent Warming Impact. The results also show that absorption hot water chillers have the lowest contribution to Global Warming (TEWI). Retrograde Alteration of Basaltic Rocks in the Þeistareykir High-Temperature Geothermal Field, North-Iceland [PDF] © Krisztina Marosvölgyi (Geothermal Energy Specialization) Abstract Hydrothermal alteration of basaltic rocks in a drill core from well ÞR-7 in the geothermal area on Þeistareykir was studied by microscope and X-ray powder diffraction (XRD) methods. Emphasis was laid on the study of clay minerals (sheet silicates) and zeolites formed by hydrothermal alteration. The reservoir rocks in the area are medium to highly hydrothermally altered. The rock forming minerals have been transformed to clay minerals or sheet silicates and several secondary minerals have been precipitated in vugs and factures. Several different clay mineral types were identified in the altered rocks: smectite, chlorite, mixed-layer minerals of of chlorite/smectite, mostly irregular types and irregular chloritic mixed-layer sheet silicates. Smectie/illite mixed-layer minerals were also encountered. The XRD diffraction patterns of the clay mineral samples from well ÞR-7, are quite complex and not easy to interpret, as the minerals are often poorly crystalline and not pure components of any single type of minerals. A regular clay zonation from smectite through mixed layer smectite-chlorite to chlorite, as is common in high-temperature geothermal fields in Iceland, is not observed in the ÞR-7 core. The zeolite types identified in the core are laumontite, yugawaralite, mordenite and wairakite. The zeolite yugawairalite is quite rare and previously only encountered in three localities in Iceland. The higher temperature zeolite wairakite is found in the middle of a zone dominated by the lower temperature zeolite laumontite. Therefore dispersion of the secondary minerals does not show a very clear zonation of the alteration minerals, and correlation to rock temperature is not easily obtained. Some of the clay minerals/sheet silicates encountered suggest a retrograde alteration of previously formed clay minerals at lower temperatures than the original hydrothermal alteration. The occurrence of zeolites in the core implies a similarity to the higher temperature zeolite wairakite that occurs in a laumontite dominant zone. The rock temperature in well ÞR-7 appears to have been higher at earlier times than at present, showing an overprint of lower temperature secondary minerals. Design and Optimization of Standardized Organic Rankine Cycle Power Plant for European Conditions [PDF] © Maciej Lukawski (Geothermal Energy Specialization) Abstract This paper investigates the possibility of introducing universally designed binary power plants into European energy markets. ORC cycles are found to be particularly useful not only for the production of electricity from geothermal water, but also for the recovery of waste heat from engine exhaust gasses, furnaces and drying ovens. In this dissertation, an analysis of market demand and thermodynamic characteristics of different heat sources is performed in order to find an optimal set of design boundary conditions maximizing unit performance for the most promising types of applications. A thermodynamic model of a power plant using a wet mechanical-draft cooling tower is created in EES software and a detailed analysis of component configuration and parameters of working fluids is carried out. Optimal plant configuration and size of components is found by thermoeconomic optimization. Exergy flow rates of all streams in the system as well as rates of exergy destruction and loss are quantified. Detailed economic analysis of the unit is made for four different applications: geothermal plants using water from conventional hydrothermal wells, former oil and gas boreholes, waste heat recovery plants coupled with diesel engines, and a clinker cooler in a cement plant. Finally, a sensitivity analysis shows the impact that changes in heat source characteristics and macroeconomic variables have on levelized cost of power. Akureyri’s District Heating System: An Optimization Study [PDF] Optimization of supply temperature © Michał Pachocki (Geothermal Energy Specialization) Abstract Iceland is in first place in the world for direct use of geothermal energy per capita. The largest use of low temperature geothermal energy is for space heating in large districts of towns. The water sent to consumers in Akureyri town in north Iceland is a mix of hot geothermal water and water returning from users’ radiators. The goal of this work is to optimize the supply temperature to the district heating distribution network, in order to minimize the amount of water extracted from geothermal fields. First the district heating system in Akureyri is described. Information on utilized geothermal fields, distribution system and equipment such as pumps, storage tanks, pipelines, etc. is presented. It is explained how the system is controlled. The second part is a case study. Operational optimization of Naustahverfi’s district heating system is performed. A running curve for supply water temperature at the pumping station is designed and a mathematical model for this optimization is used. The choice is a macroscopic model that lumps the system into one equivalent user. Data on the supply water temperature and flow as well as outdoor temperature, provided by Norðurorka Company, is used for the simulation. A curve representing the lowest geothermal water consumption is found. The work reveals and addresses the limitations of a macroscopic model. It shows how the problem can be solved in case of unsuitability of part of the data and points out the need to modify the existing theory to include snow melting installations. Well Design & Well Completion under Acidic Conditions [PDF] Mitigation of corrosion of the wells of Krafla © Gabor Rajnai (Geothermal Energy Specialization) Abstract Acidic wells are reported from several high temperature geothermal fields around the world, including the Geysers, Larderello, Miravalles, Los Humeros, Tatun, Taiwan, Saint Lucia, Windward Islands, and the Krafla. General corrosion rates can significantly influence the production, and in the case of well failures can lead to catastrophic consequences. The designer of the well has to choose whether to use expensive but corrosion resistant materials during the well completion, sacrifice the casing and the production liner and choose a cheaper grade steel or try to solve the corrosion problem by chemically treating the well. This work will try to determine the best potential corrosion resistant materials that can be applied during the completion of a geothermal well, review state of the art information about scaling inhibition due to increased iron concentration and calculate the potential dose rate of caustic injection in the case of well KJ-36. Design of a water-CO2 evaporator [PDF] Adoption of a carbon dioxide heat pump to geothermal conditions © Mateusz Tatys (Geothermal Energy Specialization) Abstract In this thesis the utilization of CO2 heat pumps, together with low-enthalpy geothermal waters or energy of waste water, will be discussed and an attempt will be made to convince the reader that those devices can be used in a simple way to save energy and mitigate global warming. Basing on the so-called EcoCute air to water CO2 heat pump, a unit which can make use of low temperature geothermal resources, as the external lower heat source will be designed. To reach this target special attention will be paid to the design of a water to carbon dioxide evaporator. The evaporator type suggested here is of a shell and tube design, with capillary copper tubes which are optimized for incoming water temperatures ranging from 15°C to 40°C and a working fluid pressure of 4MPa. This design will guarantee a small pressure drop on the CO2 side, no leaks, relatively large heat transfer area and will be worth its price. Corrosion in the Kalina cycle [PDF] An investigation into corrosion problems at the Kalina cycle geothermal power plant in Húsavík, Iceland © Peter Whittaker (Geothermal Energy Specialization) Abstract An overview of the utilization of geothermal energy in Húsavík Iceland is given. Corrosion is discussed in a theoretical manner, with references to the literature for examples of different mechanisms of corrosion. Samples taken from the Húsavík power plant were analyzed by SEM and X-ray EDS, the theory behind this method is discussed and the results are given. Ultimately the investigation into why there were corrosion problems was inconclusive but instructive. Hypotheses discussed in the conclusion, with ways to further investigate them, include: dissolution of micro-constituents in the ammonia environment, galvanic corrosion, stray current corrosion and erosion corrosion. Mild steel and aluminum seem to be inappropriate materials for Kalina cycle systems but several stainless steels (304, 316, nitronic 60 and duplex) as well as 6Al-4V titanium do not appear to suffer from corrosion.