Geothermal Technologies Office

The Rio Grande Rift Zone is a growing ~30 MY extensional structural split in the SW North American plate running from near Leadville, Colorado, south to northern Mexico. Many mineral deposits, including a new Mo/Cu/Au porphyry prospect in the San Luis Valley, occur along the rift co-located with high heat flow capable of heating geothermal waters. A previous owner of the Climax Mine, AMAX Exploration, did extensive geothermal exploration of the northern rift near the Mt. Princeton Hot Springs area in the Arkansas Valley, Chaffee CO, Colorado, in the mid 1970's. The goal was to find cheaper energy for the Climax mining operation. AMAX sought a steam-based resource typical of the time and was unsuccessful. Mt. Princeton Geothermal LLC began more recent exploration for geothermal energy in the Arkansas Valley in 2008, aided by data from the Colorado School of Mines, the Colorado Geological Survey, and AMAX. Several drill ready or prospective targets near the Mt Princeton Hot Spring Resort area have been developed utilizing a new exploration approach based on structural geology, seismology, magneto-tellurics, airborne magnetics, and remote sensing. This exploration model may apply to several other similar basins in Colorado and south along the rift zone into New Mexico. At present, the current primary target awaits funding for reservoir confirmation drilling. Delays in drilling have been caused by the recent addition of new local and state regulations, industry reluctance to invest in "over regulated and too environmental" Chaffee County / Colorado, and bouts of Nimbyism. The eventual success of this first hydrothermal geothermal energy 10+MW plant in Colorado should lead to additional discoveries south in Chaffee County, the San Luis Valley and into New Mexico along the Rio Grande rift zone.

The Geothermal Technologies Office (GTO) gathered a community of talented researchers and scientists for an in-depth review of GTO-funded research projects that continue to push boundaries and contribute towards the nation’s clean energy future.

Abstract Geothermal energy can provide answers to many of America’s essential energy questions. The United States has tremendous geothermal resources, as illustrated by the results of the DOE GeoVision analysis, but technical and non-technical barriers have historically stood in the way of widespread deployment of geothermal energy. The U.S. Department of Energy’s Geothermal Technologies Office within the Office of Energy Efficiency and Renewable Energy has invested more than $470 million in research and development (R&D) since 2015 to meet its three strategic goals: (1) unlock the potential of enhanced geothermal systems, (2) advance technologies to increase geothermal energy on the U.S. electricity grid, and (3) support R&D to expand geothermal energy opportunities throughout the United States. This paper describes many of those R&D initiatives and outlines future directions in geothermal research.

<p>A primary goal of this thesis was to obtain kinetic data on the breakdown and isomerisation reactions of naphthalene disulfonate (NDS) and naphthalene sulfonate (NSA) compounds under geothermal conditions. A secondary aim of this study was to investigate NDS/NSA isomerisation transformations as well as to study their kinetics and identify products of thermal disproportionation. Because of their apparent thermal stability, naphthalene disulfonate solutions have been frequently injected into active geothermal reservoirs and their subsequent detection (“recovery”) in nearby wells/bore holes used as an indicator of well connectivity and local permeability. The results obtained in this thesis will enable a more insightful interpretation of field injection results and fluid flow in active geothermal reservoirs. The studies presented in this thesis were designed to determine the thermal stability of aqueous NDS and NSA at high temperatures from 100 to 400°C in pure water and different salt solutions (i.e. NaCl +/- Na2SO4 and Na2S) at saturated vapour pressure. The stabilities and isomerisation transformations of NDS and NSA were also studied in the presence of solid materials (i.e. quartz, greywacke, pumice) which may occur in the host geological environment of hydrothermal/geothermal reservoirs in the Earth’s crust. Dilute aqueous solutions of NDS and NSA were contained in sealed silica glass ampoules (purged of atmospheric oxygen) and placed in stainless steel pressure vessels and heated for varying times to the desired high temperatures. Additional experiments were also conducted in which dilute NDS and NSA solutions were pumped from a de-oxygenated reservoir container through a flow-through autoclave containing different rock and mineral phases at temperatures up 400°C. The resulting NDS and NSA isomers were then analysed using HPLC and GC-MS methodologies. The 1,5-naphthalene disulfonate isomer (1,5-NDS) was found to be the least stable at pHt = 3 - 8 and readily transformed to 1-naphthalene sulfonate (1-NSA) at t ≥ 200°C. The 2-NSA was found to be the most stable isomer but disappeared at t ≥ 300°. The experimental data indicated that the stabilities of all the NDS and NSA studied as a function of temperature, pH and salt (NaCl) concentration were in the sequence: 1,5-NDS < 1,6-NDS < 2,6-NDS ≈ 2,7-NDS < 2-NSA. The presence of dissolved salts was shown to slow down the decomposition rates. Results from flow-through autoclave experiments suggest that between 100 and 250°C, the stabilities of 2,6-NDS, 2,7-NDS, 1,5-NDS and 1,6-NDS are mainly controlled by solution pH, while at t ≥ 300°C, temperature is the main stability controlling factor. Additionally, no adsorption of NDS/NSA on the surface of minerals was observed. A new high-performance liquid chromatography (HPLC) method combined with solid-phase extraction (SPE) was developed to enable detection of NDS/NSA breakdown products at t ≥ 300°C. In hydrothermal solutions at temperatures greater than 300°C, all the naphthalene sulfonate isomers become unstable with the formation naphthalene (NAP) and the two naphthol isomers, 1-naphthol (1-NAP) and 2-naphthol (2-NAP), as confirmed by both the new HPLC/SPE method and GC-MS (gas chromatography–mass spectroscopy). In addition, 1-chloronaphthalene was also detected (using GC-MS) as a high temperature reaction product NDS/NSA disproportionation in 0.05 m NaCl solutions. The results of the experiments carried out during this thesis indicate that the stabilities the naphthalene mono- and disulfonates are a function of temperature, pH and salt concentration. The naphthalene sulfonates transform to different isomers and the kinetics of these isomerisation reactions have been determined. At temperatures ≥ 300°C, the NDS and NSA compounds disproportionate to the naphthalene “backbone” molecule as well as to the two stable naphthols and 1-chloronaphthalene (in chloride containing solutions). The application of naphthalene sulfonates to determine well connectivity and local permeabilities in active geothermal reservoirs is thus rather more complicated than previously appreciated. An understanding of the various isomer transformations and their kinetics is required. Furthermore, naphthalene sulfonates injected into high temperature geothermal reservoirs are unstable and breakdown to naphthalene, naphthols and probable halogenated naphthalene compounds, none of which have been considered in the interpretation of NDS/NSA recovery data in active geothermal reservoirs. The thermal stabilities of NAP, 1- and 2-NAP and 1-chloronaphthalene indicate that these compounds may also be employed as connectivity tracers in high temperature (t ≥ 300°C) systems.</p>

Did you know that, deep down, the Earth is really hot and that this heat can generate energy? This energy, called geothermal energy, can create electricity all over the world! It all starts with water. Water is found inside rocks nearly everywhere, even very deep beneath the Earth’s surface where it is very hot. The water inside hot rocks is very hot as well, and when this fluid comes to the Earth’s surface, it can generate electricity that can turn on a lightbulb, charge your phone, and even power your car! Geothermal energy is green energy! It does not release carbon dioxide into the atmosphere, is nearly inexhaustible, and available 24/7, because the interior of the Earth is always hot. In the future, scientists hope to expand geothermal energy use with technology improvements, bringing this powerful, fascinating energy into even more cities and towns.

This report tabulates an extensive geochemical database on waters, gases, scales, rocks, and hot-spring deposits from the Dixie Valley region, Nevada. The samples from which the data were obtained were collected and analyzed during 1996 to 1999. These data provide useful information for ongoing and future investigations on geothermal energy, volcanism, ore deposits, environmental issues, and groundwater quality in this region.

At the request of the U.S. Department of Energy, Office of Geothermal Technologies, Sandia National Laboratories convened a group of drilling experts in Berkeley, CA, on April 15-16, 1997, to discuss advanced geothermal drilling systems. The objective of the workshop was to develop one or more conceptual designs for an advanced geothermal drilling system that meets all of the criteria necessary to drill a model geothermal well. The drilling process was divided into ten essential functions. Each function was examined, and discussions were held on the conventional methods used to accomplish each function and the problems commonly encountered. Alternative methods of performing each function were then listed and evaluated by the group. Alternative methods considered feasible or at least worth further investigation were identified, while methods considered impractical or not potentially cost-saving were eliminated from further discussion. This report summarizes the recommendations of the workshop participants. For each of the ten functions, the conventional methods, common problems, and recommended alternative technologies and methods are listed. Each recommended alternative is discussed, and a description is given of the process by which this information will be used by the U.S. DOE to develop an advanced geothermal drilling research program.

A project to identify and prioritize geoscience-related research needs that would be of significant benefit in the assessment, exploration, and development of US geothermal energy resources is described. The federal research needs as identified by the Panel are summarized. The research needs are organized into specific research needs for four technology areas and a group of generic research needs which relate to all of the technology areas. Arranged in order of overall need for research, these technology areas are: reservoir engineering; resource exploration and reservoir definition; well drilling, completion, and stimulation; and environmental monitoring and control. The generic research needs are: geoscience case studies, scientific drilling, information and technology transfer, and improved research coordination. (MHR)

Summary This paper describes the reservoir simulation model developed for East Mesa field properties and summarizes the reservoir engineering evaluation of the reserves and field performance. Geothermal reservoirs should be evaluated in terms of efficient "energy mining" rather than fluid recovery. The results indicate the behavior of the field under various scenarios of development designed to operate a 64-MW electric power plant. Introduction The East Mesa geothermal field is in an area of anomalously high heat flow on the east flank of the Salton Trough at the southeast corner of the Imperial Valley in California. Twenty-four wells have been drilled thus far, including 10 by Republic Geothermal Inc. in the northern portion, five by the U.S. Bureau of Reclamation in the central area, and eight by Magma Power Co. to the south (Fig. 1). Because of the already extensive investigations, a great deal is known about the East Mesa reservoir and its properties. Republic now is proceeding with commercial development at the northern end of the field, starting with a 64-MW power plant project.Geothermal resource development differs most significantly from petroleum resource exploitation in that an additional factor is involvedie., the recovery of thermal energy. The problems of fluid flow in a porous media are, of course, similar to the petroleum industry problems, but the ultimate recovery is measured in terms of energy mining efficiency. The produced fluid acts only as a transport mechanism and may be cycled through the reservoir to extract heat from the rock as many times as is economically feasible.This paper presents the reservoir model developed for Republic's East Mesa properties and summarizes the reservoir simulation study performed to optimize the exploitation of this resource. Reservoir Properties Petrophysical Properties Logs, ditch cuttings, and cores show that the upper 10,000 ft (3048 m) of stratigraphic section at East Mesa is a sequence of deltaic clastic sediments that includes abundant amounts of fine- to medium-grained sandstones, fine- to coarse-grained siltstones, and lesser amounts of mudstones. Mineralogically, the sands are compositionally equivalent to Colorado River delta sands, being mostly quartz (70%), lithic fragments (20%), and feldspars (10%). Post-depositional alterations are principally the addition of authigenic carbonate and quartz as overgrowths and veinlets and the conversion of the detrital phyllosilicates to illite and chlorite.The basic petrophysical properties of sand/shale discrimination, porosity (phi), and permeability (k) employed in the model were obtained from log analyses for eight existing wells in the Republic area (i.e., Producers 16–29, 16–30, 38–30, 58–30, and 78–30/78-30RD and Injectors 18–28 and 52–29). Table 1 summarizes net sand thickness (h), average sand porosity (phi) weighted for the presence of shales, and geometric mean sand permeability (k) for four depth-interval groupings. The data show good sand development in the wells between 2,500 and 7,000 ft (762 and 2134 m). Although the properties vary considerably between wells, they generally improve away from the center of the temperature anomaly, show a gradual decline with increasing depth, and exhibit rapid deterioration below 7,000 ft (2134 m). JPT P. 735^

San Diego Gas and Electric (SDG and E) believes that the binary-cycle offers an improved method of converting moderate temperature geothermal resources into electric power. The process, shown schematically in figure 1-1, has significant advantages over existing methods of geothermal power generation. The advantages of the binary process are that greater amounts of power can be generated from a given resource, fewer wells are needed to support a given power output, and the binary-cycle is expected to be more economical than the flash process for this type of resource. Another advantage is that the binary-cycle is a closed process and thus enhances environmental acceptability. In addition, this process is applicable to a larger range of the nations geothermal reservoirs. It is estimated that 80% of the nation's hydrothermal resources can be classified as moderate temperature (300 to 410 F) resources. The flash process, commonly used to convert high temperature geothermal resources to electric power, is technically feasible for moderate temperature resources. However, when compared to the binary process for moderate temperature applications, the flash process conversion efficiency is lower, environmental impacts may require abatement, and power production costs may not be commercially competitive.