Table of contents

3^rd International Geothermal Conference GEOHEAT 2019 organized by Research Geotechnological Center of Far Eastern Branch of the Russian Academy of Sciences of the Ministry of Science and Higher Education of the Russian Federation, Petropavlovsk-Kamchatsky, Russian Federation was held in Petropavlovsk-Kamchatsky 03-06 September, 2019.

139 people attended the conference. There were presented 19 reports, 7 of which were reports of the participants from the Russian Federation. The share of foreign countries participants amounted to 63%. There were offered the presentations from 10 countries: Azerbaijan, Bulgaria, Germany, Indonesia, People's Republic of China (Taiwan), Costa Rica, Mexico, Russia, USA and France. People from Ukraine, Kenya, India, Italy and other countries took part in the conference in absentia. Thus, the participants from all continents excluding Australia and Antarctica participated in the conference. The largest number of reports was submitted by scientists of state research institutes: it is 37%. The second place is accounted for people from industrial enterprises, both public and private: it is 26%. 3 reports were presented by authors from universities, 2 – from government organizations, 2 – from public organizations.

Conferences were preceded by short courses supported by the International Geothermal Association (International Geothermal Association, IGA).

Main topics for talks, posters, and panel discussions were theoretical issues of geothermics and heat flow, geothermal resources in extensional and compressional settings, geosciences, case studies, exploration, field management, electricity generation, drilling and well bore flows, reservoir engineering and numerical simulation, EGS/HDR, geology of geothermal fields, geochemistry of geothermal fields, thermal properties of geothermal fields rocks, low enthalpy systems and direct use, geothermal heat pumps, geothermal hydrogen, magma chambers, economics.

The event contributed to the solution of a number of fundamental problems: the development of theoretical issues of geothermics and heat flow of the Earth; establishment of new features of thermophysical processes in the geothermal water field development with supercritical thermodynamic parameters; the establishment of geothermal parameters of the Earth crust on basis of advanced experimental technologies (continuous thermal core logging technology, instruments for thermal property measurements at formation conditions, accounting of rocks heterogeneity, as well as micro- and macroanisotropy), and on this basis the geothermal resources revaluation, including geothermal resources maps. The organizing committee consisted of 27 persons from 19 countries. The conference proceedings contain the papers presented at the 3^rd International Geothermal Conference GEOHEAT 2019.

Convener, Chair of the Organizing Committee

Roman I. Pashkevich

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Volcanic terrains in general, and arc volcanic belts in particular, have been prime geothermal exploration targets as far back as the first geothermal power generation at Larderello, Italy, in 1904. The popularity of this terrain for geothermal exploration and development is based on the concept of young shallow magma bodies providing an abundance of shallow crustal heat and also on the presence of hot springs and fumaroles observed within these terrains. The success in developing these geothermal resources ranges from spectacular (e.g. Japan, Philippines, Indonesia, New Zealand, Italy, Iceland) to disappointing (e.g. Cascade Range of northwestern North America). The types, shapes and geometries of geothermal resources in volcanic terrain range in size from large broad three-dimensional fractured stockwork systems to narrow geothermal cell conduits. Effective and economic exploration and development of these resources is greatly improved by understanding the varying sizes and geometries of these resources and matching the exploration strategy design specifically for each exploration target rather than applying a single exploration formula and data interpretation model to all settings. Information from the mining industry provides valuable insight into the range in geometry and size of these resources. This body of knowledge should be used by the geothermal community: (1) for more effectively designing exploration programs specific; (2) to each prospect to interpret the body of exploration data in terms of site-specific geology and tectonics; (3) to integrate basic risk management best practices into exploration and development programs.

Russia and Bulgaria have rich resources of thermal waters. They are used for many purposes - for development of electric power, for central heating and cooling, for hot water supply, in agriculture, animal industries, fish culture, in the food, chemical and oil-extracting industries, in balneology and spas, and for the recreational purposes. Involving of these waters in economic activities can promote the decision of some social - economic and environmental problems. The problem of heat supply for town Velingrad (Bulgaria) is investigated.

The hydrothermal manifestations of Bouillante area (Guadeloupe, Lesser Antilles) motivated a geothermal survey in the sixties. Nevertheless, the heat source of the Bouillante hydrothermal system is still debated: (i) local magma body, (ii) magmatic source beneath the centre of the island or (iii) result from the deep circulation.

Several arguments support the first hypothesis and the definition of a specific volcanic series, the « Bouillante chain », according to the following characteristics:

➢ location: small monogenic volcanoes are scattered along the Caribbean coastline, on- and off-shore;

➢ structural control: volcanic centres have developed at the junction of two regional tectonic systems, the NNW-SSE trending Montserrat - Les Saintes fault and the sub-E-W trending Marie-Galante's grabens system;

➢ dynamics: their products often result from a magma - water interaction between, either in an external or internal hydromagmatism;

➢ petrology: specific magmatic trend reached an extreme (rhyolitic) level by crystal fractionation.

The links between the Bouillante chain and contemporary / neighbouring other Guadeloupe volcanic formations (Les Mamelles domes, Axial chain, Caraïbes mountains, Grande Découverte volcano) are discussed but partly remain to be specified.

The process of extracting lithium ions from the separated liquid of the Pauzhetskaya Geothermal Power Plant by modified zeolites of the Yagodninsky deposit of Kamchatka region has been experimentally studied. The four most characteristic reflexes at 2θ, deg.: 25.68, 27.11, 27.43 and 27.68 were singled out on the basis of the study of the solid phase composition of the modified sorbent on the X-ray diffractometer RIGAKU Ultima-IV (Japan). It has been established that there occurs displacement of the position of the reflexes with a change in the interplanar distance and a change of the peak width value at the semi-height (FWHM) in the process of modification. The predominant mechanism is the ion exchange H⁺→Me⁺: the calcium and magnesium ions that have been preserved in the zeolite structure during acidic treatment are exchanged for sodium and potassium ions Me²⁺→2Me⁺. The total sorption capacity of the modified sorbent during sorption from an technogenic solution under dynamic conditions is 0.31 mmol/g.

The obtaining of models of surface temperature by means of Shallow Surface Temperature - SST, shows a first approach to surface temperature anomalies in the exploration stage of a geothermal area of interest in a fast, portable and economic way. In the Colombian Geological Service - SGC, the SST materializes at depths between 20 cm and 150 cm deep, taking into account the normalization of data to eliminate the influence of solar radiation, thermal diffusivity, albedo, slopes, relief, the effect of climatic seasons. As a method parallel to the estimation of models of temperature of the terrestrial surface, the Remote Sensing - RS are integrated that have satellite images of terrestrial observation in the thermal infrared. Based on the ground truth established by the SST, the degree of positive or negative correlation is calculated with the temperature models estimated by RS, reaching a method of validation between remote sensing techniques and ground truth. Within the proposed methodology, the processing of a temperature model from RS images is proposed, specifically the processing of images with bands in the thermal infrared (such as Landsat 8 TIRS) of the geothermal area. The validation of the model achieved through the DIP - Digital Image Processing, is performed against the ground truth (SST) through qualitative and quantitative analysis with variables such as vegetation indexes or anomalies of elements such as Uranium - U, Thorium - Th and Potassium - K by gamma ray spectrometry, according to the availability of information in each geothermal area. In order to establish a positive or negative correlation between the temperature anomalies estimated from different techniques (SST vs RS), parametric correlation tests were performed pixel by pixel (Pearson coefficient).

Bulgaria is the third country in the world by number of mineral springs after Japan and Iceland. The Bulgarian-Russian collaboration in geological, environmental and landscape conservation provided a new development of the methodology for identification, evaluation and characterization of geodiversity including their geotermal resources. Individual approach to the concepts of the national geoparks stressed on their scientific and geodiversity features, environmental conditions and economic premises by defining one major geopark theme and many minor topics. Regardless of their radically different themes, the geothermal activity in geoparks is the common feature, which provides them with a great balneological potential. The concept of Geopark "Iskar Canyon" is based on the remarkable geodiversity of the Iskar River Canyon with a number of wonderful landscapes and scenic outcrops of various rock types ranging from Precambrian to Quaternary. The concept of Geopark "Belogradchik Rocks" lies on the famous Lower Triassic sandstone pinnacles. Geopark "Rila" is based on its remarkable glacial landscapes - glacier valleys, cirques, moraines, arêtes and horns. The major theme of Geopark "Burgas Lakes" is related with the ancient sea-level changes and balneo-healing properties of their humus mud. The unifying theme of these geoparks is the high spa potential of their thermal springs that have been used since the Roman Age.

The subsoil as a "thermal reservoir" is a modern concept that is leading to continuous developments of innovative methods of energy production. If volcanic areas have been so far considered suitable for exploitation of medium-to-high enthalpy resources, it is also true that an incredible potential confined to low grade resources is available. The geological background of Sicily makes the island as one of the most suitable contexts of southern Italy where geothermal resources could have great potential to increase their whole usage. Several active volcanic zones or areas at high hydrothermalism offer advantageous exploitation from low to high enthalpy geothermal resources. Here we present a case study from Santa Marina Salina (Aeolian Island Arc) with a detailed field survey providing information on lithostratigraphic features and on hydrogeological conditions of the area. The study is aimed at testing the thermal conductivity distribution at various depths by means of a theoretical model. Such an approach allowed the definition of the most suitable areas and their low-grade geothermal potential through different thematic maps for thermal conductivity in the shallow subsurface (0-150 m). Collected data become crucial for correct sizing of low-enthalpy geothermal installations, leading to optimization of the final planned technical solutions efficiency.

On the basis of literature review and patent investigations methods of cleaning natural and technical waters of toxic compounds are surveyed. The possibility of applying peat from Mitoginskoye deposit of Kamchatka krai for cleaning up spent geothermal heat carrier mediums, which are formed on the geothermal deposits in exploitation, of toxic compounds with the purpose of decreasing environmental impact is assessed.

The article presents an analysis of the main areas of change of the landscape components in the areas of geothermal systems operation, the most significant processes of transformation of the natural-territorial complex were determined.

We examine the problem of efficiency in both air-source and geothermal heat pumps in regions with low ambient air temperature, and the advantage of using a combination of both systems in one equipment. Both geothermal and air heat pumps have their advantages and disadvantages. Geothermal heat pumps are more expensive to install and, in colder climates, experience a progressive decrease in efficiency with constant use during the winter season because of chilling of the ground adjacent to geothermal heat exchangers during heat extraction. Air-source heat pumps are less expensive to install and experience a decrease in efficiency as ambient temperature is getting lower. A numerical model simulation was conducted using the program "INSOLAR.GSHP.12" for a 200 sq.m. house in Moscow. The model tested the efficiency of combined use of a ground heat pump at ambient temperatures below -10°C, and air heat pump for ambient temperatures above -10°C. The results were compared to simulation of using only a geothermal heat pump. The results show a 13.3% reduction in energy consumption using the combined ground and air heat pumps over the energy requirement of using only the geothermal heat pump.

Geothermal power production relies on elevated temperature, high-enthalpy and consistent transmissivity from the tapped geothermal system. The Dixie Valley power plant in north-central Nevada, has been in operation for the last 30 years with sustained fluid production and has experienced negligible temperature decrease. Indicating that the power plant has produced sustainably from the resource in that time. Chemical and isotope analysis does infer that the thermal fluids produced at the power plant are from meteoric sources yet the Dixie Valley hydrologic basin receives only an average total annual recharge of 28 million m³. The average annual fluid production at the power plant is more than 20 million m³, and would amount to a substantial portion of the total yearly aquifer recharge being produced by this facility. Mountain precipitation is suggested as the primary source for thermal fluid recharge. Mountain infiltration into regional aquifers ranges from 3-15% of precipitation and valley surface recharge is negligible due to roughly equivalent precipitation and evapotranspiration. It is unlikely that infiltration from mountain recharge is the primary fluid for this geothermal resource but rather a regional input from the broader subsurface saturated zone that supplies this system.

The GEMex project is a binational endeavour developed by a Mexican and a European consortium coordinated by a common executive board. Each consortium is financed by their own resources, which are approximately 10 million euros for each part. The project is focused on two geothermal areas, Los Humeros and Acoculco, and was started two years ago. In January 2019 it reached its half point for the Mexican partners, and from the Mexican viewpoint the main results up to then can be summarized as follows. There is a new volcano-tectonic framework and characterization that has been rising from the geoscientific work developed, integrated and modelled by the project, which in the case of the Los Humeros geothermal field is profiling the most promising areas where the superhot geothermal fluids could be found. In the case of Acoculco, the integration model has provided the current stress field that can be used to develop an EGS project in the area, which still needs to be completed with the interpretation of the remaining seismic data, and that is planned to be tested at the final stages of the project with a stimulation test. The expected outcomes can be used by the CFE (Comisión Federal de Electricidad), which is the public utility that has the proper permits to explore and develop both geothermal areas.

The results of numerical thermo-hydrodynamic simulation of Koshelev geothermal system are presented. The question of the possibility of the existence of a shallow geothermal reservoir at the Lower-Koshelev thermal field is briefly investigated. The simulation results refute the assumption of the existence of a near-surface geothermal reservoir. It is more likely that in this part of the geothermal system there is a region of permeable rock that is relatively narrow in cross section and which performs the function of a conduit. The size and shape of the apical part of the steam zone under the Lower-Koshelev thermal field are controlled by the diameter of the conduit. Results of simulations with a conduit diameter of 1200 and 500 m are presented. The latter is more likely, since it best matches the field data.

A new analytic model is introduced to describe rock deformation produced by fluid injection / extraction in geothermal reservoirs. This model is fully coupled under isothermal conditions and thermally uncoupled if local thermal non-equilibrium (LTNE) is considered. The model describes both fluid flow with conductive-convective heat transfer and rock deformation in cylindrical coordinates. There are 13 unknowns in the model: fluid pressure, fluid content variation, solid skeleton displacement, radial, tangential and volumetric strains, two stresses, porosity, solid deformation velocity, fluid velocity, rock and fluid temperatures. Considering LTNE, there is an effective heat transfer between the solid skeleton and the liquid. The porosity is estimated as a function of fluid pressure and temperature. The solid radial deformation is an irrotational vector field, thus the fluid content variation, is proportional to pore pressure, which is calculated using the classical Theis solution. Therefore, the solid radial displacement can be obtained in analytical form. Once the fluid velocity is computed, the fluid temperature is deduced from a new analytical solution of the diffusion-convection equation. This model is didactic, useful and simple. It allows to explore different options for both the fluid and the poroelastic parameters, with different boundary conditions. Graphic results illustrate practical cases with fluid extraction/injection into a reservoir using real data.

The structure of the Earth's crust and upper mantle has been estimated by using geologic-geophysical cross-sections developed along two orthogonal geophysical profiles in the area of the Tolmachevsky active magmatic center. Comprehensive geophysical data have revealed the existence of an intrusive massif of predominantly intermediate-medium-felsic composition whose formation is accounted for by the presence of powerful heat flows and local melting sites. A swarm of small earthquakes reported in 1987-1988 was triggered by the advance of magma in the zone of the assumed eruptive fissure. Meteoric waters interact with the high-temperature media through the infiltration zone, which results in intense hydrothermal activity including the formation of steam-hydrothermal occurrences. The area of the proposed intrusive body is a promising zone for a high-temperature geothermal reservoir.

Thermal power potential assessments of Avacha geothermal system performed by different authors of the works and the methods adopted for evaluation are presented. A significant variation of the predicted thermal and electric power values was established. In order to obtain a more reliable heat and power potential assessment in the present work the authors have developed the thermo-hydrodynamic model of Avacha geothermal system based on the complex of available geological and geophysical data. According to the numerical simulation results, the lower assessment of the system resources is 35 MW, the upper one is 302 MW of thermal power.

A set of advanced methods and instruments was developed to improve essentially quality of experimental data on reservoir thermal properties (thermal conductivity, thermal diffusivity, volumetric heat capacity, coefficient of linear thermal expansion) at atmospheric and reservoir thermobaric conditions. The new thermal core logging technique provides continuous high-resolution profiling rock thermal properties along wells accounting for rock anisotropy and multi-scale heterogeneity. Integration of the technique application results with standard well logging data leads to possibilities of high resolution profiling porosity, rock matrix thermal properties, elastic wave velocities and modulus, rock density, etc. New approaches are described that allow indirect determination of the reservoir thermal properties from standard petrophysical logging data accounting for formation anisotropy. A new laser optical scanning instrument, enhanced theoretical modeling of effective thermal properties and special workflow opened a way to determination of combination for rock thermal properties on rock cuttings at formation temperatures. The new experimental basis improves reliability of data on physical properties of reservoirs, results of specific heat flow determination and reservoir thermal regime modeling within prospecting, exploration and development of geothermal energy fields.

We have carried out the experiments on coagulation and precipitation of silica from the separate of Verkhne-Mutnovsky geothermal electric power plant (Mutnovskoe hydrothermal field). Silica precipitation from the water solution was conducted in two ways: by adding slaked lime CaO and by electrocoagulation treatment on aluminium electrodes. Silica precipitation with addition of slaked lime was carried out under laboratory conditions at the temperature of 20 and 96 °C. Colloid and monomeric silica concentrations, solution pH, flakes sizes and physical-chemical properties of material precipitated with different quantities of added lime were determined. We also carried out series of experiments on solution treatment of mixed type: addition lime with freshly precipitated flakes, and addition lime with sea water. In the experiments on electric coagulation, current intensity and distance between electrodes were changed. Dependence of silica concentration on treatment duration was studied. Quantities of electric energy and anode aluminium consumed for reducing of silica concentration to a certain level were obtained. The results of our experiments can be used for developing of technological scheme of silica precipitation and utilization optimal for Verkhne-Mutnovsky geothermal electric power plant.

Geological position of two close active volcanoes in Southern Kamchatka – Mutnovsky and Gorely perspective for geotechnological development as sources of energy and raw materials is presented. Multicone ridged volcanoes edifices of a general linear range are localized respectively in front and near rear zones of the Kuril-Kamchatka island arc system in the zone of crust decompression with different depth of their basement. The characteristics of the volcanoes positions are considered as the reasons for the differences of compositions and evolution features of magma feeding them.

Rocks structure and composition and the history of Mutnovsky volcano development which is one of the most favorable objects of geotechnical exploration according to the situation in the infrastructure of Kamchatka and high energy of modern gas-hydrothermal activity are described. Its latest volcanic activity, eruption mechanisms are discussed, the forecast of activity and morphostructural evolution of the volcano is given.

The information about the structure, development and composition of the rocks of long-lived Gorelovsky volcanic center, which modern activity stage is represented by multicone intracaldera Gorely volcano with a developed fracture (rift) zone is shown. The features of magma activity in the conditions of low density of hosting crustal rocks are discussed. The conjugation of the directional evolution of magmatic material and magma-conductive structure of the volcanic centre with the formation of modern near-surface magmatic chamber of Gorely volcano is represented.

Serial belonging and features of rocks evolution of the South-Kamchatka volcanoes Mutnovsky and Gorely occupying different positions in the structure of cross petrochemical zonality of island arc system are discussed. Basalt-riodacite rocks series of the Mutnovsky volcano was formed as a result of differentiation of parent magma of high-aluminous tholeiite composition with rare mixture of its derivatives. The rocks of Gorely volcano with similar range of silica acidity have increased potassium alkalinity and belong to the transition type from tholeiite to calc-alkali. Magma mixture of different stages of differentiation played a significant role to form it. This phenomenon confinedness to specific stages of volcanic systems evolution allows to estimate general energetic orientation of their development, with the increase or decrease of the share of the best heat capacity basalt substance in the material composition erupted by them.

Geothermal is a consistent and reliable source of renewable energy for various scale exploitation. However, harnessing geothermal energy is limited to small-scale direct heat applications in many countries, primarily due to various technical and economic reasons. One among the many reasons is a meager amount of field studies available for the reliable prediction of reservoir potential, especially in India. Assessment of temperature field depends on proper information of subsurface field properties. The assessed temperature field further determines the stored heat energy. The accurate assessment of reservoir potential depends on temperature field. Reasonable reservoir potential information would encourage policymakers to plan developmental works at various scales. Since the information on subsurface characteristics is limited in the absence of deep exploration data, assessment of reservoir potential is associated with uncertainties. In this regard, this study presents a methodology for preliminary assessment of reservoir potential in terms of temperature and thermo-hydro-geological features, which also predicts the stored heat energy. The study considers the geothermal status of India, where the developmental activities and exploration are still at nascent stages, and predicts the temperature and energy distribution of Puga geothermal reservoir based on the available resistivity data.

New data on the stability of flow in the steam-water geothermal well are presented. There are facts of failures during commissioning of wells, testing which implied a positive result. An explanation of the marked phenomenon is presented in basis of new notions about stability of flow in the steam-water geothermal wells.

Sustainable exploitation strategies of high-enthalpy geothermal reservoirs in a volcanic geothermal play type require an accurate understanding of key geological structures such as faults, cap rock and caldera boundaries. Of same importance is the recognition of possible magmatic body intrusions and their morphology, whether they are tabular like dikes, layered like sills or domes. The relative value of those magmatic bodies, their age, shape and location rely on the role they play as possible local heat sources, hydraulic barriers between reservoir compartments, and their far-reaching effect on the geochemistry and dynamics of fluids. Obtaining detailed knowledge and a more complete understanding at the early stages of exploration through integrated geological, geophysical and geochemical methods is essential to determine promising geothermal drilling targets for optimized production/re-injection schemes and for the development of adequate exploitation programs. Valuable, extensive geophysical data gathered at Las Pailas high-enthalpy geothermal field at northwestern Costa Rica combined with detailed understanding of the geological structures in the underground may represent a sound basis for an in-depth geoscientific discussion on this topic. Currently, the German cooperation for the identification of geothermal resources in Central America, implemented by the Federal Institute for Geosciences and Natural Resources (BGR), supports an international and interdisciplinary effort, driven by the Instituto Costarricense de Electricidad (ICE) with different international and national research institutions, including the Leibniz Institute for Applied Geophysics (LIAG). The discussions and joint studies refer to the optimized utilization of geophysical and geological methods for geothermal exploration in the Central American region, using the example of Las Pailas Geothermal Field. The results should contribute to a better understanding of the most appropriate geothermal exploration concepts for complex volcanic field settings in Central America.

Low-temperature geothermal resources are widely distributed in the sedimentary cover of Western Siberia. In the southern part of the region the aquifer of the Pokur formation (K_1-2), with temperatures up to 47° C at well heads, has the best prospects for direct heating. The energy extracted from this kind of geothermal resources must be used near the reservoir, that's why collocation of the resource and a user is required. A new approach to the issue of using this energy potential is integrated use of existing water wells, drilled for domestic and drinking purposes, for heating of premises (including hot water supply) and water supply at rural communities in the south of Western Siberia. The research was aimed at the estimation of effectiveness of ground-source heat pump (GSHP) systems for extraction of energy from low-temperature groundwater, and their use for space heating of commercial buildings under the climatic conditions of the region. The computations were made by using NIBE AB (Sweden) software. It states that GSHP systems are very competitive with coal boilers, mostly used for hot water supply and space heating at domestic communities. The use of GSHP systems will also improve the ecological situation in the region.

Geothermal resources can be indicated by surface manifestations such as hot springs, hot mud puddles, and geysers. In the Northern Ternate region, in the villages of Tobololo and Sulamadaha, the manisfestation of hot springs is present. Therefore the purpose of this research is to study the geothermal characteristic in the Northern Ternate region, Indonesia, based on interpretation of magnetic anomalies in the hot surface temperature of hot springs. The method employed a fluxgate magnetometer to measure a sample of random temperature. Furthermore it examined for their chemical content to determine their resource type.

The results show that the magnetic anomalies value in the Northern Ternate region is of -3678.63 nT up to 2679.57 nT. The contour map is then developed by indicating three levels of magnetic anomalies; low, medium, and high. This is an indication that the area is of geothermal manifestation and it is classified as a hypothetical resource that could become an unexpected reserve. The temperature is measured at 50 cm depth and it shows of 27-38.50 °C. The result of the temperature anomaly in the Tobololo area is due to the flow of hot springs along the coastline. Meanwhile the Sulamadaha area has a smaller hot spring discharge, which is due to hydrothermal activity below the surface. Based on the the geochemistry assessments, both areas have alkali chloride water type.