Numerical simulation studies of ihe geothermal resource in singapore 2

Chapter Introduction Geothermal energy development in Singapore is more feasible than was apparent a couple of decades ago. In the past, the fact that Singapore is a small island with no recent volcanic activity suggested that development for conventional geothermal energy would be uneconomical. Nevertheless, the presence of natural hot springs and apparent high heat flow in Singapore give rise to a potential for geothermal energy development, most likely with an unconventional method. Present day uncertainty in fossil fuel supply, its price and its negative environmental impacts have made the geothermal energy and other alternatives, like solar and nuclear energy, become more attractive for Singapore. Utilization of solar energy is still costly and it also requires a sufficiently large surface area, which is a challenge for a small island like Singapore. Development of nuclear energy remains uncertain, especially after the incident at Fukushima nuclear power plant in Japan in 2011. 1.1 An Overview of Geothermal Technology Geothermal technology makes use of heat energy generated deep in the earth for power production and other forms of heat-related applications. It uses geothermal energy which is a clean and renewable source of energy. Radioactive decay of various isotopes from the earth’s mantle and core represents the primary source of the exploited geothermal energy [1]. Conventional geothermal resources are often found in locations associated with high volcanic or tectonic activities, such as along the tectonic plate divergent or convergent boundaries. Hydrothermal activities on the surface are good indicators for the nearby subsurface geothermal resources (see Figure 1.1 for worldwide site of hydrothermal activity). Figure 1.1: Plate tectonic map of the world showing locations (1-50) of selected submarine and terrestrial high temperature hydrothermal sites (after [2]) Some examples of the geothermal surface features are geysers, hot pools, fumaroles, hot springs, mud pools, steaming ground, and so on (Figure 1.2). Monitoring of the mass and heat flows, and the fluid chemistry of these surface features are useful for identifying the scale of the potential geothermal resource underground [3]. Figure 1.2: Some examples of geothermal surface features: a. Mud pool near Krafla volcano, Iceland (modified after [4]); b. Steaming ground at Karapiti, New Zealand; c. Strokkur geyser, Iceland (after [5]); d. The biggest fumarole in Da-You-Keng, Taiwan (modified after [6]); e. Black smoker vent at East Pacific Rise 21 ◦ N hydrothermal field (after [2]) Geothermal power plant is a baseload power source, i.e. it can operate continuously at up to 98 % capacity because it has a constant source of fuel (heat) and it requires a very low downtime for maintenance [7]. It has far smaller greenhouse gases emissions per unit of electricity generated compared to a conventional thermal power station, e.g. coal or gas power plant [8]. Some examples of geothermal power plants are shown in Figure 1.3. At medium and high heat content (enthalpy) conventional geothermal resources (generally > 100 ◦ C), highly pressurized fluid from natural geothermal systems is brought to the surface through wells that vary in depth from a few hundred metres to 2.5 kilometres [12]. Hot fluid brought to the surface is separated into steam and Figure 1.3: Examples of geothermal power plants: a. Larderello power station, Italy (after [5]); b. The 47.4 MWe Germencik power plant, Turkey (after [9]); c. The MWe binary ORC power plant at Landau, Germany (after [10]); d. The Geysers, California, USA (after [11]) brine. The steam is used to turn the rotors of turbines, which in turn spin generators to produce electricity. The brine is used to produce more steam (e.g. by flashing) for electricity generation, to supply heat for other relatively low temperature applications, to be reinjected back to the ground through reinjection wells (Figure 1.4), or to be drained away. Injected fluid is useful for maintaining reservoir pressure in the later stages of production [13]. It can also be used as the source of recharge fluid to be restored, reheated and later re-extracted again through the production wells. Low enthalpy conventional geothermal resources are ubiquitous but more suitable for direct uses, like health spas, heating greenhouses, geothermal prawn farming (e.g. on the banks of Waikato River in New Zealand), space conditioning of residential and commercial buildings by installing heat pump systems, cooking, industrial heating, and so on. Electricity can also be generated from this type of resource by using binary plant technology, for example: the 0.21 MWe geothermal power plant in NeustadtGlewe, Germany, uses the Organic Rankine Cycle (ORC) to generate electricity from GEOTHERMAL POWER PLANT Power Plant Production Well Injection Well Magma Figure 1.4: Schematic of geothermal power plant production and injection wells (modified after [14]) 98 ◦ C fluid with a flowrate of 35 L/s [10]. The energy-depleted brine is either drained away or reinjected back to the ground. Current practice is to reinject the brine back to the subsurface geothermal system in order to minimize release of geothermal fluids on to the surface of the earth. The worldwide installed capacity of geothermal plants in 2010 is shown in Figure 1.5, with total installed capacity of 10,898 MWe. The top five countries in terms of installed capacity are: USA (3098 MWe), Philippines (1904 MWe), Indonesia (1197 MWe), Mexico (958 MWe), and Italy (843 MWe). The forecast total worldwide installed capacity for 2015 is 19.8 GWe, which is almost double the installed capacity in 2010 (see [15] for more statistical data). Such a high prediction is supported by the advancing technology in binary plants, which enables geothermal power production at sites with low to medium enthalpy geothermal resources. It also improves power production efficiency at high enthalpy geothermal resource sites by allowing further power production for the 100-180 ◦ C geothermal water that otherwise would have been injected back to the system. Figure 1.5: Worldwide geothermal power plants installed capacity in 2010 (after [15]) 1.2 1.2.1 A Brief History of Geothermal Energy Conventional geothermal resource The use of geothermal heat can be traced back to very early times when it was used for direct-use applications, like therapeutic bath and cooking. In the wild, naturally occurring hot pools are used by some monkeys (Figure 1.6b) for survival against the winter cold temperature. The first human use of geothermal heat in North America occurred more than 10,000 years ago with the settlement of Paleo-Indians at hot springs [16]. In the Roman times, steam and hot water springs were used for hot water and bathing (Figure 1.6a). In modern times, geothermal energy was first exploited by Prince Piero Ginori Conti for a power generation demonstration by using emerging steam to drive a small Figure 1.6: Use of geothermal heat: a. Roman bath at Bath, England (after [5]) ; b. Snow monkeys soak in hot pools in Japan (after [17]) turbine to provide electricity for five incandescent light bulbs in Larderello, Southern Tuscany, Italy, in 1904 [18]. Nine years later the first geothermal power plant producing 250 kWe was constructed at Larderello. In 1958, the second geothermal power plant was built in Wairakei, New Zealand. In 1960, the third geothermal power plant producing 11 MW electricity was in operation in the Geysers, USA. The world total installed capacity has been increasing since then (Figure 1.7). Installed Capacity (MW) 20,000 15,000 10,000 5,000 1950 1960 1970 1980 1990 2000 2010 2020 Years Figure 1.7: World geothermal installed capacity from year 1950 to 2010 and a forecast capacity at 2015 (data after [15]) 1.2.2 Overview of EGS Conventional geothermal resources rely mainly on the availability of permeable rock, and a sufficient amount of groundwater as the medium to transport the heat energy. Permeable rock combined with groundwater and a relatively shallow heat source results in hydrothermal a system. Such systems are mainly found at the locations shown in Figure 1.1. At locations far away from the tectonic or volcanic activities, either the rock is not permeable enough, the groundwater is scarce, or the heat source is too deep for economical exploitation. However, in some areas like the caprock or the margins of hydrothermal systems [19], the heat source is close enough to the surface, but the rock is not permeable enough. Fracturing the rock (via hydraulic, thermal, and/or chemical stimulations) increases its permeability, and pumping of water from the surface through these artificial fracture networks allow for heat extraction from the relatively shallow and hot dry rock. This technique enhances the reservoir, and hence the name Enhanced Geothermal System (EGS), also known earlier as Hot Dry Rock (HDR) system. The general concept is shown in Figure 1.8, where cold water is pumped via an injection well to flow through the artificially fractured rock. As it flows, heat is transferred from the hot rock to heat up the flowing water. The heated water is then extracted through the production well and used for power generation. In 1977, Los Alamos established the first operational HDR circulation loop at Fenton Hill. A series of experiments were carried out but the HDR system failed to produce power at a commercial scale. Nevertheless, the experiments included the first generation of electricity from a HDR system, a modest 60 kW of electricity using a binary turbine-generator [21]. Since then, many other experiments with HDR systems have been carried out at other places (Figure 1.9), like Rosemanowes, Hijiori, Soultz, Cooper Basin, and so on (see [20] for more). A general lesson from these experiments Figure 1.8: Schematic of two-well EGS in a low-permeability crystalline basement formation (modified after [20]) Figure 1.9: Evolution of global EGS projects with estimated electrical power output per production well (after [20]) is that in order to minimize runaway water losses and short-circuiting when creating the stimulated reservoir rock, the use of low-pressure stimulation (hydroshearing) is preferred to high-pressure hydraulic fracturing [21]. A MIT study sponsored by the U.S. Department of Energy in 2006 [20] concluded that EGS in the United States could provide 100,000 MWe or more in 50 years. The projection was based on a review of past EGS projects and realization of performance criteria that include a thermal drawdown in the production well of no more than 10 ◦C over 30 years, and a flow of 50 kg/s. The U.S. Department of Energy (USDE), Ormat and GeothermEx recently (April 2013) announced that they have successfully produced 1.7 MWe from EGS technology, which marked the first EGS project to be connected to the US electricity grid [22]. 1.3 1.3.1 Site Examples Conventional geothermal fields: Indonesia Indonesia is situated on the Pacific ‘Ring of Fire’ (see Figure 1.1 point 17-19) and is estimated to have approximately 28,000 MWe of potential conventional geothermal resources (considered to be the largest in the world) [23]. Exploration for hightemperature geothermal resources in Indonesia has been carried out since 1970 [24]. By year 2000, at least geothermal fields had been developed with a total capacity of 800 MWe. In 2010, Indonesia had 1,197 MWe of geothermal generation in operation. During the World Geothermal Conference 2010 in Bali, President Susilo Bambang Yudhoyono said that Indonesia aimed to be the world’s leading geothermal nation by 2025 [25]. Some of the largest geothermal resources in Indonesia are found in Java and Suma- 10 6.9 Technological Progress Using current technology to drill two or more kilometers deep wells and stimulating the reservoir for EGS method in Singapore may be hindered by the cost. However, this may not be the case when new methods (that are currently under research) are commercialized. Some possible developing methods to escalate to commercial scale in the near future are the use of laser drilling, the use of high pulsed power technology, and the use of solar power technology. Laser drilling [98] is a very fast drilling method. At current state, this method can be used to drill rock, but not rock with drilling fluid, because drilling fluid is a significant heat sink. Drilling through rock with drilling fluid requires too much power at present state. High Pulsed Power (HPP) technology [99] can be used for drilling. The idea is to compress energy so that when a relatively low electrical power is released at an extremely brief period of time, an ultra high electrical power is generated. The power is large enough to break rock. Solar power technology allows for direct conversion of heat to electricity. Such direct heat to electricity (DHE technology) has been studied for application in geothermal energy so that heat energy can be directly converted to electricity without going through the mechanical function [100, 101]. The technology use thermoelectric generator or TEG [102] in an equivalent way of how a Photo Voltaic in a solar panel converts solar heat to electricity. Electric voltage is generated when a temperature differential is established between the hot and cold ends of the semiconductor materials used in the TEG (Figure 6.5). The voltage is called Seebeck voltage and is almost proportional to the temperature differential [103]. TEG allows for usage of lower temperature water 149 (may be down to 30 ◦ C [100]). (a) (b) Figure 6.5: Thermoelectric generator: (a) Schematic of the conventional arrangement where Q1 is the supplied heat, P is the generated electrical power, and Q2 is the heat dissipated to the heat sink (after [103]); (b) An experiment of thermoelectric power generation system to light up ten 15W bulbs (after [101]) Another option is to use hybrid geothermal-solar plant as is used in Stillwater project [104]. A study [105] indicates that the use of this hybrid plant for a midrange geothermal reservoir temperature of 150 ◦ C can reduce the cost of electricity production by 20 % if compared to the use of stand-alone EGS method. The study site is in Australia and it uses standard design solar irradiance of 1,000 W/m . Further study is required to determine whether the hybrid method can be utilised in Singapore. 150 Chapter Conclusions This study is aimed to form a good model that can be used to assess the geothermal resource in Singapore through simulation of the groundwater flow interaction with the the heat flow and the physical properties of the rock. The main contributions and findings of the study are summarized into three categories, i.e. input data, natural state modelling, and fracture modelling. 7.1 Input Data The main contributions and findings in this study are: - Heat flow at Singapore has been estimated to be 130 mW/m , which is obtained from literature and the database of a leading geothermal industry company, Chevron. - A modified GHP method has been developed. It allows for thermal conductivity measurement when only limited sample is available (e.g. only one small size sample is available for each measurement). - Thermal conductivities of Singapore rocks have been measured. These values represent the few available data for the rocks in Singapore. 151 - The measured thermal conductivity of Jurong sedimentary is 1.4 W/mK for shallow depth, and 2.0 - 3.6 W/mK for deeper depth (31 to 148.5 m or more). Thermal conductivity of surface rock samples are: granite 1.9 - 3.5 W/mK; Gombak gabbro 2.3 W/mK; Sentosa mudstone 0.8 - 1.6 W/mK; and Murai slate 1.3 W/mK. - The borehole logs from Jurong regions (see Appendix A) represent the few available borehole logs for Singapore rocks at depths more than 40 m and up to 150 m. 7.2 Natural State Modelling The main contributions and findings in this study are: - A two-dimensional numerical model for Singapore geothermal reservoir has been constructed and calibrated to best match the observed and expected natural state conditions, i.e. the observed hot spring location and its properties (e.g. temperature, salinity and flowrate), the observed groundwater level at Bukit Timah hill, and the expected Singapore fresh and saline groundwater profile. The obtained match level can be considered a significant step forward considering the few available data to start with. - During the model calibration process and the study of parameter variations, the model is found to be most sensitive to the rock permeability. This has further strengthened the notion that the main parameter to be calibrated for a natural state model is the rock permeability. - This study shows that variation of rock thermal conductivity has a limited effect on the simulation results. An example is found in Section 4.2.3.3, in which the model is more sensitive to both the ‘queen’ and ‘murai’ rocktypes’ permeabilities than to their thermal conductivities. 152 - The calibrated natural state model suggests that there is a highly fractured rock structure (resembling a sub-vertical fault) that allows the groundwater to emerge as a hot spring at Sembawang. If field exploration is carried out, more information on the fractured rock (e.g. its spatial extent) can be obtained. This information is useful for site selection, especially for drilling location. - The calibrated natural state model shows that the granite at depth has a permeability of to 1.5 mD (which is a fairly fractured granite), the Jurong sedimentary at depth has a permeability of to 10 mD, the Kallang alluvium and seabed soils have a low permeability of 0.01 to mD, and the surface soil has a high permeability of 25 to 50 mD (due to the tropical climate which promotes extensive rock weathering). - The natural state model shows two high temperature upflows: one towards the Sembawang hot spring (125 to 150 ◦ C at depth to 1.8 km), and another towards the Jurong region (125 to 150 ◦ C at depth to km depth). See Figure 5.5 for the refined grid temperature profile. - The Singapore geothermal reservoir model represents a unique model that can be used as a conceptual blueprint to develop geothermal reservoir model for other location with similar condition, e.g. a small island surrounded by seawater. 7.3 Fracture Modelling The main contributions and findings in this study are: - The fracture modelling for production through EGS method is a developing field in geothermal reservoir modelling. Fracture modelling for Singapore geothermal reservoir is part of that developing study. 153 - Fracture spacing is one of the main parameters in using dual porosity model for EGS production simulation. For the case of Singapore, fracture spacing of 20 m is found to be sufficient for the granite at depth. - In production simulations, the results are found to be sensitive not only to the production mass flowrate, but also to the rock porosity. - In dual porosity modelling for production with EGS method, the stimulated rock is assigned with porosities for both the matrix and the fracture continua. Simulation results show that the production temperature decline increases as the porosity of both matrix and fracture continua increases, but it is more sensitive to matrix porosity increment. - Simulations for production with EGS show that Singapore geothermal resource is likely to have a production temperature decline of about 30 to 40 ◦ C for 25 years with 30 kg/s production rate, and a temperature decline of about 10 to 20 ◦ C for 25 years with 20 kg/s production rate. The initial production temperature is about 155 ◦ C. - Optimum model for production simulation is found to have key parameters of: single fractured zone, production rate of 20 kg/s, dual porosity model with matrix continuum porosity of 0.2 % (represents Bukit Timah granite) and fracture continuum porosity of 20 %. This model is expected to produce 0.67 MW of electricity for 25 years with average production temperature of 150 ◦ C (temperature decline about 10 ◦ C). If production is simulated with three fractured zones model, MW electricity is produced. 154 7.4 Proposed Road Map A broad scale road map can be developed for geothermal study in Singapore based on the studies that have been completed and the studies that are proposed (Figure 7.1). Stage and in the road map have been completed, and Stage to Stage are the proposed stages to reach a milestone of a pilot plant to produce electricity. Figure 7.1: Proposed road map for study of geothermal resource in Singapore The 2D model in this study (Stage 2) suggests that there is an upflow of hot temperature at Sembawang with depth to 1.8 km for 125 to 150 ◦ C. EGS production is simulated with this temperature profile, and the result suggests a potential for generating MW or more electricity with a multi-layer fracturing method in a doublet well system. A series of five doublets could be drilled from a common drilling platform to generate 10 MWe. The model assumes 130 mW/m heat flow for Singapore. To move forward, it is necessary to measure the actual heat flow at Singapore. This is proposed in Stage 3: shallow wells (300 m) ought to be drilled for temperature measurement (hence heat flow), well testing (to obtain rock mechanical properties), 155 geological logging, wire logging and other tests to obtain data that can be used for model improvement (Stage 4), both to improve the 2D model and to construct the 3D model. If both the model and measurement results indicate a good potential at depth, Stage can be carried out by drilling deep wells, followed by reservoir rock stimulation and circulation test. If the drilled wells are found to be connected via the artificial fracture networks, the study can advance to a pilot plant to generate electricity (say MWe) in Stage 6. 156 Bibliography [1] EPRI, “Geothermal power: Issues, technologies, and opportunities for research, development, demonstration, and deployment,” online: http://www.gtherm. net/downloads/EPRI_Geothermal_WhitePaper.pdf, Electric Power Research Institute, California, February 2010. Accessed: June 2013. [2] R. Lowell and P. Rona, “Hydrothermal activity: Tectonics,” in Encyclopedia of Geology (R. C. Selley, L. Robin, M. Cocks, and I. R. Plimer, eds.), pp. 362 – 372, Oxford: Elsevier, 2005. [3] H. P. Heasler, C. Jaworowski, and D. Foley, “Geothermal systems and monitoring hydrothermal features,” The Geological Society of America, pp. 105–140, 2009. [4] A. Zoporowski and S. A. Miller, “Modelling eruption cycles and decay of mud volcanoes,” Marine and Petroleum Geology, vol. 26, no. 9, pp. 1879 – 1887, 2009. [5] G. J. H. McCall, “Geysers and hot springs,” in Encyclopedia of Geology (R. C. Selley, L. Robin, M. Cocks, and I. R. Plimer, eds.), pp. 105 – 117, Oxford: Elsevier, 2005. [6] H.-F. Lee, T. F. Yang, T. F. Lan, C.-H. Chen, S.-R. Song, and S. Tsao, “Temporal variations of gas compositions of fumaroles in the Tatun Volcano Group, northern Taiwan,” Journal of Volcanology and Geothermal Research, vol. 178, no. 4, pp. 624 – 635, 2008. [7] Clean Energy Association of British Columbia, “Fact sheet: Geothermal power.” Online: http://www.cleanenergybc.org/media/CEBC_FS-Geothermal_web. pdf. Accessed: 22 May 2013. [8] C. Stewart, “Geothermal energy - Effects on the environment,” in Te Ara - the Encyclopedia of New Zealand, July 2012. Online: http://www.teara.govt.nz/ en/geothermal-energy/page-5. [9] M. Unverdi and Y. Cerci, “Performance analysis of Germencik geothermal power plant,” Energy, vol. 52, pp. 192 – 200, 2013. [10] H. Quick, J. Michael, U. Arslan, and H. Huber, “Geothermal application in lowenthalpy regions,” Renewable Energy, vol. 49, pp. 133 – 136, 2013. [11] USGS, “Plate tectonic and people.” Online: http://pubs.usgs.gov/gip/ dynamic/tectonics.html#anchor10912135, May 1999. Accessed: 10 May 2013. 157 [12] OTP Geothermal, “Origin Energy and Tata Power, together with PT Supraco Indonesia, have been awarded the Sorik Marapi geothermal exploration concession in North Sumatra.” Online: http://www.originenergy.com.au/news/files/ OTPRelease.pdf, September 2010. Accessed: 23 May 2013. [13] E. Kaya, M. J. O’Sullivan, and K. Brockbank, “Reinjection into liquid-dominated two-phase geothermal systems,” in Thirty-Sixth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2011. [14] M. Shibaki and F. Beck, “Geothermal energy for electric power,” online: http://www.repp.org/articles/static/1/binaries/Geothermal_ Issue_Brief.pdf, Renewable Energy Policy Project, Washington, December 2003. Accessed: May 2013. [15] R. Bertani, “Geothermal power generation in the world 2005-2010 update report,” Geothermics, vol. 41, pp. – 29, 2012. [16] USDE, “A history of geothermal energy in the United States.” Online: http:// www1.eere.energy.gov/geothermal/history.html, February 2013. Accessed: May 2013. [17] BBC, “Best science and technology pictures of the week.” Online: http://www. bbc.com/future/story/20121213-most-stunning-images-of-the-week , December 2012. Accessed: May 2013. [18] USDE, “A history of geothermal energy research and development in the United States,” Tech. Rep. Volume 3: Reservoir Engineering, United States Department of Energy, 2010. Online: http://www1.eere.energy.gov/geothermal/pdfs/ geothermal_history_3_engineering.pdf. [19] K. Pruess, “On production behavior of enhanced geothermal systems with CO as working fluid,” Energy Conversion and Management, vol. 49, pp. 1446–1454, 2008. [20] MIT, “The future of geothermal energy,” tech. rep., Massachusetts Institute of Technology, Cambridge, MA, 2006. [21] J. Ziagos, B. R. Phillips, L. Boyd, A. Jelacic, G. Stillman, and E. Hass, “A technology roadmap for strategic development of Enhanced Geothermal Systems,” in Thirty-Eighth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2013. [22] Ormat, “Success with Enhanced Geothermal Systems changing the future of geothermal power in the U.S ” Online: http://www.ormat.com/news/latest-items/ success-enhanced-geothermal-systems-changing-future-geothermal-power-us , April 2013. Accessed: 12 May 2013. [23] Origin, “Origin to explore geothermal opportunities in Indonesia.” Online: http://www.originenergy.com.au/news/article/asxmedia-releases/ 1217, September 2010. Accessed: 17 October 2012. 158 [24] M. P. Hochstein and S. Sudarman, “History of geothermal exploration in Indonesia from 1970 to 2000,” Geothermics, vol. 37, no. 3, pp. 220 – 266, 2008. [25] T. Allard, “Indonesia’s hot terrain set to power its future.” Online: http://www.theage.com.au/environment/ indonesias-hot-terrain-set-to-power-its-future-20100430-tzd2.html , May 2010. Accessed: 11 May 2013. [26] J. A. Acuna, J. Stimac, L. Sirad-Azwar, and R. G. Pasikki, “Reservoir management at Awibengkok geothermal field, West Java, Indonesia,” Geothermics, vol. 37, no. 3, pp. 332 – 346, 2008. [27] M. P. Hochstein and J. N. Moore, “Indonesia: Geothermal prospects and developments,” Geothermics, vol. 37, no. 3, pp. 217 – 219, 2008. [28] A. Genter, X. Goerke, J.-J. Graff, N. Cuenot, G. Krall, M. Schindler, and G. Ravier, “Current status of the EGS Soultz geothermal project (France),” in World Geothermal Congress 2010, (Bali, Indonesia), April 2010. [29] D. Wyborn, “Completion of Habanero closed-loop circulation test,” in Australian Geothermal Energy Conference 2009, 2009. [30] D. Chen and D. Wyborn, “Habanero field test in the Cooper Basin, Australia: A proof-of-concepts for EGS,” GRC Transactions, vol. 33, pp. 159–164, 2009. [31] G. Ward, “Major stimulation completed at Habanero 4.” Online: http://geodynamics.com.au/ getattachment/67cd47d8-4375-4de5-adf3-eeaf812b6503/ Major-stimulation-completed-at-Habanero-4.aspx, December 2012. Accessed: Jul 2013. [32] B. Bendall, C. Huddlestone-Holmes, and B. Goldstein, “The current status of geothermal project in Australia - a national review,” in Thirty-Eighth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2013. [33] L. X. Richter, “Geodynamics successful starts Habanero MWe EGS pilot plant.” Online: http://thinkgeoenergy.com/archives/15382, May 2013. Accessed: Jul 2013. [34] Geodynamics, “Innamincka (EGS) project.” Online: http://www.geodynamics. com.au/Our-Projects/Innamincka-Deeps.aspx, 2013. Accessed: 30 Dec 2013. [35] T. Cladouhos, W. Osborn, S. Petty, D. Bour, J. Iovenitti, O. Callahan, Y. Nordin, D. Perry, and P. Stern, “Newberry volcano EGS demonstration – Phase I results,” in Thirty-Seventh Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2012. [36] AltaRock, “Frequently asked questions about the Newberry EGS demonstration.” Online: http://altarockenergy.com/projectupdates/Newberry_EGS_ FAQ.pdf, March 2012. Accessed: 22 May 2012. 159 [37] T. Cladouhos, S. Petty, B. Larson, J. Iovenitti, B. Livesay, and R. Baria, “Toward more efficient heat mining: A planned enhanced geothrmal system demonstration project,” GRC Transactions, vol. 33, pp. 165–170, 2009. [38] AltaRock, “AltaRock Energy announces successful multiple-zone stimulation of well at the Newberry enhanced geothermal systems demonstration.” Online: http://altarockenergy.com/media/AltaRock_Stimulation_Release_ Final_1_21_13.pdf, Januray 2013. Accesssed: 15 May 2013. [39] S. Petty, Y. Nordin, W. Glassley, T. T. Cladouhos, and M. Swyer, “Improving geothermal project economics with multi-zone stimulation: Results from the Newberry volcano EGS demonstration,” in Thirty-Eighth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2013. [40] G. J. H. Oliver, “Geothermal energy concept for Singapore,” SEAPEX Press, vol. 12, no. 57, pp. 48–54, 2009. [41] F. Zulkefli, “Geothermal heat-driven district cooling system in a new housing estate feasibility study,” unpublished dissertation, National University of Singapore, 2011. [42] G. Oliver, A. Palmer, H. Tjiawi, and F. Zulkefli, “Geothermal power for Singapore,” Innovation, vol. 10, no. 2, pp. 26–29, 2011. [43] L. S. Z. Michelle, A. Palmer, G. Oliver, and H. Tjiawi, “Geothermal desalination in Singapore,” The IES Journal Part A: Civil & Structural Engineering, vol. 6, pp. 42–50, Feb 2013. [44] “Thermal conductivity of some common material and gases.” Online: http: //www.engineeringtoolbox.com/thermal-conductivity-d_429.html . Accessed: 12 May 2012. [45] H. K. H. Goh, M. Roach, and A. Reading, “Rock properties of North-Eastern Tasmania: Implications for EGS development,” in World Geothermal Congress 2010, (Bali, Indonesia), April 2010. [46] F. Brigaud and G. Vasseur, “Mineralogy, porosity and fluid control on thermal conductivity of sedimentary rocks,” Geophysical Journal, vol. 98, pp. 525–542, March 1989. [47] “ASTM C177-10: Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by means of the Guarded-Hot-Plate Apparatus,” 2010. [48] Holometrix Micromet, Operation & Maintenance Manual: Holometrix Model GHP-300 Guarded Hot Plate, August 1992. [49] “ASTM C1044-07: Standard Practice for Using a Guarded-Hot-Plate Apparatus of Thin-Heater Apparatus in the Single-Sided Mode,” 2007. 160 [50] C. Clauser and E. Huenges, “Thermal conductivity of rocks and minerals,” American Geophysical Union, vol. 3, pp. 105–126, 1995. [51] M. J. O’Sullivan, K. Pruess, and M. J. Lippmann, “State of the art of geothermal reservoir simulation,” Geothermics, vol. 30, no. 4, pp. 395–429, 2001. [52] J. Bundschuh and M. C. S. Arriaga, Introduction to the Numerical Modeling of Groundwater and Geothermal Systems: Fundamentals of Mass, Energy and Solute Transport in Poroelastic Rocks. CRC Press, 2010. [53] J. S. Sharma, J. Chu, and J. Zhao, “Geological and geotechnical features of Singapore: An overview,” Tunnelling and Underground Space Technology, vol. 14, no. 4, pp. 419–431, 1999. [54] PWD, The Geology of the Republic of Singapore. Singapore: Public Works Department, 1976. [55] J. Zhao, “Construction and utilization of rock caverns in Singapore – Part A: The Bukit Timah granite bedrock resource,” Tunnelling and Underground Space Technology, vol. 11, no. 1, pp. 65–72, 1996. [56] J. Pitts, “A review of geology and engineering geology in Singapore,” Quarterly Journal of Engineering Geology and Hydrogeology, vol. 17, no. 2, pp. 93–101, 1984. [57] G. J. H. Oliver, A. C. Palmer, H. Tjiawi, and F. Zulkefli, “Engineered geothermal power systems for Singapore,” The IES Journal Part A: Civil and Structural Engineering, vol. 4, pp. 245–253, November 2011. [58] J. Zhao, C. N. Chen, and J. G. Cai, “A hydrogeological study of the Sembawang hot spring in Singapore,” Bulletin of Engineering Geology and the Environment, vol. 61, no. 1, pp. 59–71, 2001. [59] C. W. Sum, S. Irawan, and M. T. Fathaddin, “Hot springs in the Malay Peninsula,” in World Geothermal Congress 2010, Bali, Indonesia, April 2010. [60] R. Hall and C. K. Morley, “Sundaland basins,” Geophysical Monograph, vol. 149, pp. 55–85, 2004. [61] H. N. Pollack, S. J. Hurter, and J. R. Johnson, “Heat flow from the Earth’s interior: Analysis of the global data set,” Reviews of Geophysics, vol. 31, no. 3, pp. 267–280, 1993. [62] C. E. Soon, P. Tkalich, K. G. Yew-Hoong, and J. P. Obbard, The Physical Oceanography of Singapore Coastal Waters and Its Implications for Oil Spills, ch. 23, pp. 393–412. Berlin/Heidelberg: Springer-Verlag, 2006. [63] K. W. Lee and W. Zhou, Geology of Singapore. Singapore: Defence Science and Technology Agency, 2nd ed., 2009. [64] C. L. Sien, H. Khan, and C. L. Ming, “The coastal environmental profile of Singapore,” Technical Reports 44688, Worldfish Center, 1988. 161 [65] P. M. Barlow, “Ground water in freshwater-saltwater environments of the Atlantic coast,” Circular 1262, U.S. Geological Survey, 2003. [66] K. L. Ng and N. Sivasothi, “Salinity and the mangroves ecosystem.” Online: http://mangrove.nus.edu.sg/guidebooks/text/1011c.htm, 2001. Accessed: 19 October 2010. [67] AUTOUGH2 Notes, Notes for using AUTOUGH2 (the Auckland University version of TOUGH2), 2002. Last modified 17 October 2002. [68] A. Croucher, PyTOUGH User’s Guide. Department of Engineering Science, University of Auckland, June 2012. [69] K. Pruess, C. Oldenburg, and G. Moridis, “TOUGH2 user’s guide version 2.1,” Report LBNL-43134 (revised), Lawrence Berkeley National Laboratory, California, August 2011. [70] T. N. Narasimhan and P. A. Witherspoon, “An integrated finite difference method for analyzing fluid flow in porous media,” Water Resources Research, vol. 12, no. 1, pp. 57–64, 1976. [71] W. Kissling, S. P. White, M. J. O’Sullivan, D. P. Bullivant, and K. L. Brown, “Modelling chloride and CO chemistry at the Wairakei geothermal field, New Zealand,” in Twenty-First Workshop on Geothermal Reservoir Engineering, (Stanford, California), pp. 217–223, January 1996. [72] J. J. C. Austria, Jr., “Production capacity assessment of the Bacon-Manito geothermal reservoir, Philippines,” Master’s thesis, United Nations University, 2008. [73] Mulyadi and A. Ashat, “Reservoir modeling of the Northern vapor-dominated two-phase zone of the Wayang Windu geothermal field, Java, Indonesia,” in Thirty-Sixth Workshop on Geothermal Reservoir Engineering, (Stanford, California), January 2011. [74] A. Yani, “Numerical modelling of Lahendong geothermal system, Indonesia,” m.Sc. report, The United Nations University, 2006. [75] “12 - Integral Inequalities,” in Table of Integrals, Series, and Products (A. Jeffrey and D. Zwillinger, eds.), pp. 1053 – 1058, San Diego: Academic Press, th ed., 2000. [76] A. E. Croucher and M. J. O’Sullivan, “Approaches to local grid refinement in TOUGH2 models,” in Thirty-Fifth New Zealand Geothermal Workshop, (Rotorua, New Zealand), November 2013. [77] J. G. Cai, “Geology of Singapore.” Online: http://www.srmeg.org.sg/docs/ N13072012_2.pdf, July 2012. Accessed: Jan 2014. [78] J. Zhao, B. Broms, Y. Zhou, and V. Choa, “A study of the weathering of the Bukit Timah granite – Part B: Field and laboratory investigations,” Bulletin of Engineering Geology and the Environment, vol. 50, no. 1, pp. 105–111, 1994. 162 [79] W. J. Cho and S. Kwon, “Estimation of the thermal properties for partially saturated granite,” Engineering Geology, vol. 115, pp. 132–138, 2010. [80] F. S. Spear, Metamorphic Phase Equilibria and Pressure–Temperature–Time Paths. Washington, DC: Mineralogical Society of America, 1993. 799 pp. [81] P. I. Nabelek, M. Liu, and M.-L. Sirbescu, “Thermo-rheological, shear heating model for leucogranite generation, metamorphism, and deformation during the Proterozoic Trans-Hudson orogeny, Black Hills, South Dakota,” Tectonophysics, vol. 342, pp. 371–388, 2001. [82] E. Kaya and M. O’Sullivan, “Modelling of injection into vapour-dominated geothermal systems,” in World Geothermal Congress 2010, (Bali, Indonesia), April 2010. [83] K. H. Coats, “Geothermal reservoir modelling,” in The 52nd SPE Annual Fall Technical Conference and Exhibition, (Denver, Colorado), 1977. [84] R. C. Earlougher, Advances in Well Test Analysis. Monograph (Society of Petroleum Engineers of AIME), Henry L. Doherty Memorial Fund of AIME, 1977. [85] G. Oliver, K. Zaw, M. Hotson, S. Meffre, and T. Manka, “U-Pb zircon geochronology of Early Permian to Late Triassic rocks from Singapore and Johor: A plate tectonic reinterpretation,” Gondwana Research, pp. –, 2013. http://dx.doi.org/10.1016/j.gr.2013.03.019. [86] Thunderhead Engineering, Manhattan, USA, Petrasim User Manual. [87] A. Croucher, “PyTOUGH: A python scripting library for automating TOUGH2 simulations,” in New Zealand Geothermal Workshop 2011 Proceedings, (Auckland, New Zealand), November 2011. [88] J. E. Warren and P. J. Root, “The behavior of naturally fractured reservoirs,” Society of Petroleum Engineers Journal, vol. 3, pp. 245–255, September 1963. [89] S. K. Sanyal and S. J. Butler, “An analysis of power generation prospects from Enhanced Geothermal Systems,” in World Geothermal Congress 2005, (Antalya, Turkey), GeothermEx, April 2005. [90] A. Franco and M. Villani, “Optimal design of binary cycle power plants for water-dominated, medium-temperature geothermal fields,” Geothermics, vol. 38, pp. 379–391, December 2009. [91] M. Grassiani, “Siliceous scaling aspects of geothermal power generation using binary cycle heat recovery,” in World Geothermal Congress 2000, (Kyushu Tohoku, Japan), June 2000. [92] M. A. Grant and S. K. Garg, “Recovery factor for EGS,” in Thirty-Seventh Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2012. 163 [93] K. Pruess, “GMINC - a mesh generator for flow simulations in fractured reservoirs,” Report LBNL-15227, Lawrence Berkeley National Laboratory, Berkeley, CA, March 1983. [94] A. V. Kiryukhin, N. P. Asaulova, T. V. Rychkova, and N. V. Obora, “Modeling the Pauzhetsky geothermal field, Kamchatka, Russia,” GRC Transactions, vol. 30, pp. 819–824, 2006. [95] H. Hole, “Geothermal well completion tests,” in Petroleum Engineering Summer School Workshop 26, (Dubrovnik, Croatia), June 2008. [96] Lidar, “Using LiDAR to better understand volcanoes and geothermal energy.” Online: http://blog.lidarnews.com/ using-lidar-to-better-understand-volcanoes-and-geothermal-energy , July 2013. Accesssed: 15 July 2013. [97] M. O. Haring, U. Schanz, F. Ladner, and B. C. Dyer, “Characterisation of the Basel enhanced geothermal system,” Geothermics, vol. 37, pp. 469–495, 2008. [98] J. Hecht, “Laser drills could relight geothermal energy dreams.” Online: http://www.newscientist.com/article/mg21628955. 900-laser-drills-could-relight-geothermal-energy-dreams.html , December 2012. Accesssed: 15 July 2013. [99] iPulse, “Corporate overview: Innovations by I-Pulse are at the heart of new cutting edge capabilities for geophysical surveys, enhanced petroleum recovery, metal manufacturing and mineral ore processing,” December 2011. [100] K. Li, “Comparison of geothermal with solar and wind power generation systems,” in Thirty-Eighth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2013. [101] K. Li, C. Liu, and P. Chen, “Direct power generation from heat without mechanical work,” in Thirty-Eighth Workshop on Geothermal Reservoir Engineering, (Stanford, California), Stanford University, February 2013. [102] E. F. Thacher, B. T. Helenbrook, M. A. Karri, and C. J. Richter, “Testing of an automobile exhaust thermoelectric generator in a light truck,” Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering , vol. 221, no. 1, pp. 95–107, 2007. [103] S. B. Riffat and X. Ma, “Thermoelectrics: A review of present and potential applications,” Applied Thermal Engineering, vol. 23, pp. 913–935, 2013. [104] A. Neville, “Top plant: Stillwater solar-geothermal hybrid plant, churchill county, nevada.” Online: http://www.powermag.com/renewables/solar/5183.html, December 2012. Accessed: 19 Jul 2013. [105] C. Zhou, E. Doroodchi, and B. Moghtaderi, “An in-depth assessment of hybrid solar-geothermal power generation,” Energy Conversion and Management, vol. 74, pp. 88–101, 2013. 164 [...]... much vibration from the cutting machine Wet cutting cannot be used because the sample is easily disintegrated in water Cutting of the sample is therefore performed with a 14 inch diameter diamond coated cutter, with dry cutting The refining cut (smoothing and polishing of flat 28 surfaces) cannot be performed in the lab due to tool limitation in handling the thin sample ( 12 mm thick), and so the samples... EGS plant that exists yet 1.4 The Singapore Context The high heat flow and the existing hot spring suggest that Singapore has a potential geothermal resource In 20 09, Oliver [40] proposed a concept utilising the EGS method to tap heat from the potential subsurface hot rock at depth (e.g 150 ◦ C at 2 km depth) Possible applications of the geothermal energy in Singapore include: electricity generation,... MWe), the combined capacity of these two projects makes Chevron the largest geothermal operator in Indonesia [26 ] Awibengkok is a water-dominated reservoir with temperatures of 23 5 to 310 ◦ C Other developed geothermal projects in Indonesia include [27 ]: Lahendong (20 MWe), Dieng (60 MWe), Wayang-Windu (110 MWe), Kamojang (140 MWe), and a 2- MWe project at Sibayak (at Sumatra Island) 1.3 .2 EGS: Soultz,... back, the three geothermal wells in the middle, and the cooled geothermal loop in the front (after [28 ]) 12 1.3.3 EGS: Cooper Basin, South Australia Geothermal projects in Australia is unique in a way that they are mainly driven by private sector, unlike projects in other countries that are mainly driven by government sector Several private companies that involve in geothermal projects in South Australia... conductivities of Singapore sedimentary and granite rocks are measured with modified GHP method Collection of most of the sedimentary rock samples involved collaboration with the JTC Corporation The heat flow are estimated from existing heat flow map surrounding Singapore and also compared against the data from Chevron’s database of existing wells that are close to Singapore The specific objective of this... groundwater profile, the Sembawang hot spring location, flowrate, temperature and salinity The calibrated model is then used for simulations of production with EGS method The production simulations are carried out with both single and dual porosity models Parametric studies of the rock porosities are also carried out Being the first study of its kind at NUS and in Singapore, the study includes several... the main hot plate The heat from the main hot plate is conducted through the sample and the insulators to the cold plates (see Figure 2. 4) Coolant in The total heat power Coolant out Upper Heat Sink Insulation Upper Cold Plate, T2 Upper insulator + sample T = Temperature Main Heater, T1 T2 > T1 T3 T1 Lower insulator Lower Cold Plate, T3 Insulation Lower Heat Sink Coolant in Coolant out Figure 2. 4: Modified... Energy Cooper Basin in South Australia has substantial oil and gas reserves Oil exploration in this area encountered high-temperature gradients and intersected granitic basement with high abundance of radiogenic elements This information led Geodynamics to drill their first well (injection well Habanero-1) to a depth of 4, 421 m with bottom-hole temperature of 25 0 ◦ C in 20 03 [20 , 21 ] Series of stimulations... seen in Figure 2. 5 The main input power (controls the temperature of the main hot plate) is set through the main controller The temperature of the cold plates and the guard heater plates (see Figure 2. 1) are also set through the main controller The main controller is connected to the GHP assembly box in which the sample is measured (see Figure 2. 4 for the schematic in the assembly box) Cold plates in. .. area of approximately 3 km2 Habanero -2 was later drilled and it encountered fractures at 4, 325 m depth In mid 20 05, flow from Habanero -2 was tested, and a flow rate of 25 kg/s was achieved with a surface temperature of 21 0 ◦ C In 20 08, Habanero-3 was successfully drilled at 560 m NE from Habanero-1 The two wells was successfully connected by a stimulated fracture system located at a depth of 4 ,25 0 . Conference 20 10 in Bali, President Susilo Bambang Yudhoyono said that Indonesia aimed to be the world’s leading geothermal nation by 20 25 [25 ]. Some of the largest geothermal resources in Indonesia. [24 ]. By year 20 00, at least 6 geothermal fields had been developed with a total capacity of 800 MWe. In 20 10, Indonesia had 1,197 MWe of geothermal generation in operation. During the World Geothermal. surface of the earth. The worldwide installed capacity of geothermal plants in 20 10 is shown in Figure 1.5, with total installed capacity of 10,898 MWe. The top five countries in terms of installed