Geothermal Resource Assessment Research Articles

A robust assessment method of recoverable geothermal energy considering optimal development parameters

It is known that development parameters such as injection and production rate, injection temperature, and well location and spacing play an important role in determining the recoverable geothermal energy in a licensed region during the exploitation stage, but they are seldomly considered in geothermal resource assessment. In this study, a robust assessment method of recoverable geothermal energy considering the optimal development parameters is developed. To maximize the recoverable geothermal energy whilst avoid environmental disasters including reservoir pressure declining, thermal breakthrough and surface subsidence, an efficient approach of optimizing development parameters is proposed using the fully coupled thermo-hydro-mechanical reservoir model, experimental design and proxy model, and multiple response optimization method. Based on the case study of two doublets in the Tongzhou district, China, the robustness and reasonability of the developed assessment method are demonstrated. The results show that the optimal development parameters can significantly increase the recoverable geothermal energy, but the optimal development parameters for different doublets are different due to the complexity in geological structures and the heterogeneity in reservoir parameters. Therefore, it is highly recommended to maximize the recoverable geothermal energy by selecting the optimal development parameters.

Assessment of geothermal resources in the west area of Taikang town in Dumeng geothermal field, NE China

Combined with geothermal drilling, well logging, geological and geophysical investigations, this study established a conceptual model of the Dumeng geothermal field, Songliao Basin, and evaluated the potential of the geothermal resources of western Taikang town, an area under concentrated development in the geothermal field, based on transient groundwater flow equation. The results show that the Dumeng geothermal field is part of a conductive type geothermal system. The evaluated heat reserve is 8.76×1017 J, the storage of thermal water is 4.94×109 m3, the recoverable reserve of the thermal water is 9.85×105 m3/a, which is equivalent to an outpower of 5.59 MW, and is comparable to a small geothermal field. This study provides a basis for scientific management of the further exploration and utilization of the geothermal resources and application of the mining rights.

Geothermal resources assessment using temperature–depth relationships in the fault-controlled hydrothermal system of Aristino-Traianoupolis area, Northern Greece

Aristino-Traianoupolis area hosts one of the most significant water-dominated low-temperature geothermal fields in Greece. It is located on the southwestern uplifted margin of the Tertiary Evros Delta molassic basin, 10 km east of the town of Alexandroupolis (Thrace, NE Greece). The upper hydrothermal system of the Aristino Geothermal Field (AGF), one of the most promising in continental Greece, contains fluids with temperatures ranging from 51 to 99 °C, within a series of overlapping aquifers at very low depths (100–430 m). The main geothermal anomaly for temperatures higher than 90 °C covers an area of 6 km2, to a maximum prospected depth of 500 m below ground surface. The scattered regional anomaly exceeds 50 km2 and is characterized by excessively high and abruptly changing thermal gradient (42 to 450 °C/km) and heat flow (80–800 mW/m2), that are both typical of a fault-controlled hydrothermal system. Since 1993, the AGF has undergone non-systematic geothermal investigation, with emphasis on low-depth (100–500 m) drilling. This paper provides, for the first time, a synthetic and detailed evaluation of all available temperature data gathered in the last 25 years. The steady-state temperature logs reveal the dominant role of conduction for the upper geothermal system, accompanied, in most cases, by rapidly changing and abnormally high thermal gradients (100–450 °C/km), triggered, most probably, by a deeper system of higher temperature. This hypothesis is also supported by the applied chemical geothermometers, which suggest initial fluid temperatures at 140–150 °C, the hydrochemical characteristics of the fluids hosted in the deeper and most promising investigated reservoir (ignimbrite) of the upper system, and the extrapolated temperatures from the conductive temperature–depth profiles. The lower widespread medium enthalpy hydrothermal system should extend at depths 500–1000 m within volcanics and the expected Eocene limestones and basal clastic series of the Tertiary sequence that have filled the basin. Nevertheless, these assumptions need to be verified by appropriate investigations and new drillings at depths greater than 600–700 m, which would confirm the presence of a productive medium enthalpy reservoir.

The impact of hydrothermal alteration on the physiochemical characteristics of reservoir rocks: the case of the Los Humeros geothermal field (Mexico)

Hydrothermal alteration is a common process in active geothermal systems and can significantly change the physiochemical properties of rocks. To improve reservoir assessment and modeling of high-temperature geothermal resources linked to active volcanic settings, a detailed understanding of the reservoir is needed. The Los Humeros Volcanic Complex, hosting the third largest exploited geothermal field in Mexico, represents a natural laboratory to investigate the impact of hydrothermal processes on the rock properties through andesitic reservoir cores and outcropping analogs. Complementary petrographic and chemical analyses were used to characterize the intensities and facies of hydrothermal alteration. The alteration varies from argillic and propylitic facies characterized by no significant changes of the REE budget indicating an inert behavior to silicic facies and skarn instead showing highly variable REE contents. Unaltered outcrop samples predominantly feature low matrix permeabilities (< 10–17 m2) as well as low to intermediate matrix porosities (< 5–15%), thermal conductivities (0.89–1.49 W m−1 K−1), thermal diffusivities (~ 0.83 10–6 m2 s−1), and sonic wave velocities (VP: ~ 2800–4100 m s−1, VS: ~ 1600–2400 m s−1). Average magnetic susceptibility and specific heat capacity range between 2.4–7.0 10–3 SI and 752–772 J kg−1 K−1, respectively. In contrast, the hydrothermally altered reservoir samples show enhanced porosities (~ 7–23%), permeabilities (10–17–10–14 m2), and thermal properties (> 1.67 W m−1 K−1; > 0.91 10–6 m2 s−1), but a significant loss of magnetic susceptibility (10–3–10–6 SI). In particular, this latter characteristic appears to be a suitable indicator during geophysical survey for the identification of hydrothermalized domains and possible pathways for fluids. The lack of clear trends between alteration facies, alteration intensity, and chemical indices in the studied samples is interpreted as the response to multiple and/or repeated hydrothermal events. Finally, the proposed integrated field-based approach shows the capability to unravel the complexity of geothermal reservoir rocks in active volcanic settings.

Probabilistic geothermal resource assessment in Maichen Sag, south China

It is crucial for financial providers, investment groups, resource developers, and exploration companies to rate new geothermal projects in terms of resources and reserves. In general, the existing volumetric method is constrained by limited information when projects are at the early stage of development. The main objective of this study is to estimate the probabilistic potential thermal energy of the M research area in the Maichen Sag, a geothermal prospect in South China, through stochastic methodologies. The probabilistic assessment methodology provides a way to embody the uncertainty and risk in geothermal projects and to quantify the power potential in a probable range. In this study, proxy numerical models were built by combining the Experimental Design (ED) and Response Surface Methodology (RSM) with the Monte Carlo Simulation technique. An improved workflow for combined ED-RSM that uses two-level Full Factorial and Box–Behnken designs was proposed. For comparative analysis, the typical volumetric technique was also implemented in this study. The ED-RSM results show that the M area has P10, P50, and P90 reserves of 5.7 × 1014 J, 5.3 × 1014 J, and 5 × 1014 J, respectively, and these numbers from the typical volumetric method are 1.5 × 1015 J, 9 × 1014 J, and 5.1 × 1014 J, respectively. In this study, the operability, applicability, and accessibility of ED-RSM in the assessment of geothermal potential and its ability to provide a reliable output are demonstrated.

Geothermal Geological Characteristics and Genetic Model of the Shunping Area along Eastern Taihang Mountain

Knowledge about subsurface geological characteristics and a geothermic genetic model plays an essential role in geothermal exploration and resource assessment. To solve the problem in the Shunping area along eastern Taihang Mountain, geothermal geological conditions were analyzed by geophysical, geochemical, and geological methods, such as magnetotelluric, gas geochemistry, and structural analysis. The geothermic genetic model was developed by analyzing the characteristics of the heat source, water source, migration channel, reservoir, and cap rock of the geothermal geological conditions. Favorable deep thermal conduction conditions and sufficient atmospheric precipitation in the study area provide an original heat source and water supply for geothermal formation. The faults and unconformities of different scales have become effective channels for the migration of underground hot water. The thermal reservoir formed by marine carbonate rocks with karst fissure development provides suitable space for the storage of underground hot water. Although the Cenozoic strata have good thermal insulation and water insulation function, the thermal insulation and water insulation effect is not ideal because of the shallow coverage in the Shunping area and the damage by tectonic action, which affected thermal insulation and water insulation to some extent, restricting the practical preservation of underground heat energy in the Shunping area. The bedrock geothermal resource in the Shunping area is original from the combined action of multiple indexes of source, transport, reservoir, and cap. The geothermal geologic conditions of source and reservoir in the Shunping area are very similar to those in the Xiongan new area, and have obvious advantages in hydrodynamic conditions. Although limited by the cap’s effectiveness, the geothermal resources in the Shunping area can provide some clean energy support for local production and life, thereby satisfying economic development conditions and encouraging further geological exploration.

Low - medium enthalpy geothermal resource assessment in deep reservoirs of the Llanos Basin - Colombia

The exploration and exploitation of hydrocarbons in sedimentary basins such as the Llanos Basin of Colombia, have enabled the acquisition of large volumes of surface and subsurface data, for assessing the geothermal potential of deep aquifers. The integrated analysis of geothermal play elements such as temperature, reservoir - fluid properties, and their depth in the basin, with the available hydrogeological-chemical data, allow us to define three regional plays as follows: Play A, characterized by naturally fractured reservoirs, in crystalline basement rocks - Paleozoic, with temperatures above 150 ºC, semi-confined aquifers; b) Play B, composed by Mesozoic quartz sandstone reservoirs, with primary porosity greater than 10%, temperatures between 75 ºC to 150 ºC, semi-confined aquifers, near to high hydraulic head zones with 500 m difference ranges in the regional piezometric surface; c) Play C, composed by Mesozoic quartz sandstones, high primary porosity, temperatures below 100 ºC, confined aquifers. Available well and Oil and Gas production data suggests that Play A is speculative, Play B is hypothetical, and Play C is known.

Regional geothermal resource assessment of hot dry rocks in Northern England using 3D geological and thermal models

This study assesses the geothermal potential in Northern England for hot dry rocks, with specific focus to the North Pennine and Lake District Batholiths. The heat in place was estimated using an adapted volume method, which considers a 3D geological and thermal model of the subsurface. Using deterministic methods, the total heat in place was calculated at 2639.9 EJ and the recoverable heat at 52.8 EJ. When considering heat available for electricity generation only, the heat in place was calculated as 1856.1 EJ and recoverable heat as 37.1 EJ. Probabilistic methods were also used to determine uncertainty, but provided similar P50 values to the deterministic average values listed above. The uncertainty range for the total heat in place was determined by the P90-P50-P10 estimates which corresponded to 2572 EJ - 3104 EJ - 3637 EJ. Results from this study offer encouragement that the successful development of hot dry rock prospects can be produced in Northern England where a significant geothermal resource is constrained.

Assessment of geothermal power potential in the Gediz Basin, Turkey

By the end of 2020, the installed geothermal power capacity in Turkey reached 1643 MWe. Approximately one-fifth of the capacity of the installed power plants is located at the Gediz graben, which is geologically the second largest structure of the Menderes Massif. The Gediz graben has several geothermal surface manifestations and geothermal resources that have been discovered. When considering the structural/geological similarities between the Buyuk Menderes and the Gediz graben, both regions can be assessed as geothermal basins.The scope of this study is to estimate the geothermal power potential of the Gediz graben. To achieve this, a different stochastic approach is used rather than the conventional geothermal resource assessment. This approach involves using temperature depended volume distributions obtained from drilled wells, which lead to improved and solid results. Three hot anomalies that are identified from temperature dependent volumes are evaluated using the Monte Carlo Simulation technique. In these simulations, distribution data of other parameters are used along with data obtained from the drilled wells in the region.The power potential (MWe) values for three identified anomalies in terms of P10, P50 and P90 values are estimated to be 825, 1157 and 1524 MWe, respectively. Furthermore, additional geothermal potential discovery is predicted in the graben, provided that extensive efforts are exerted.

Assessment of Deep and Shallow Geothermal Resources and Measurement of Waste Heat Potentials from Industrial Processes for Supplying Renewable Heat for Industry and Urban Quarters

Deep geothermal resources for heat supply and waste heat potentials were assessed and measured for a high-temperature dairy plant. For the industrial waste heat, a borehole heat exchanger (BHE) seasonal storage was configured and simulated after an extensive investigation of shallow geothermal resources. We developed a concept for the subsequent use of the residual and waste heat from the plant in a low-temperature heating and cooling (LTHC) grid for the neighbouring former military camp “Martinek-Kaserne” with a future use as mixed-use urban quarter were investigated in two projects. The modelling of the deep geothermal resources showed that of the three potential reservoirs one is most feasible for geothermal heat supply with temperatures between 129 and 146 °C, which could be used with a high-temperature heat pump for process heat. The waste heat in all sub-processes of the dairy plant were measured over 18 months to identify the most suitable waste heat streams with regard to temperature and continuity. The results showed that 25 % of the waste heat from a sub-process of the plant (fresh products logistics) is sufficient to provide heat for the adjacent LTHC grid with a total energy demand of 3428 MWh per year. The simulation of the BHE field resulted in 96 BHE with 180 m depth for a dis-/charging capacity of 643.7 MWh and 20 decentral heat pumps in the buildings. The BHE field operates quite balanced with only 12.8 MWh of difference in the annual balance. The results of the feasibility study for deep and shallow geothermal resources, and the assessment of the industrial waste heat show that the whole cascade of high-temperature heat for industry to low-temperature heat for the LTHC grid could be realized at the investigated site.

Probabilistic geothermal resource assessment using experimental design and response surface methodology: The Leyte geothermal production field

Estimating power potential (MWe) with higher accuracy remains a necessity and a challenge confronting the geothermal industry. Reservoir models can predict MWe capacity probabilistically for resource management and decision-making use, but the process remains laborious to implement. This work involves applying the Experimental Design (ED) and Response Surface Methodology (RSM) framework to a calibrated natural-state reservoir model for predicting MWe probabilistically, quantifying uncertainties in the prediction and identifying the key driving factors.This study has chosen six uncertain parameters and implemented the Plackett-Burman design to build twelve versions of the Leyte reservoir model for uncertainty quantification. These uncertain parameters are permeability in the x, y and z-direction, porosity, reinjection enthalpy (RI Enthalpy), and the fraction of reinjection (% RI). Results revealed that all of these parameters except RI Enthalpy are significant predictors of MWe and that the Leyte Geothermal Production Field (LGPF) has an indicative capacity of 670 MWe (P90), 730 MWe (P50) and 790 MWe (P10) if it operates for 50 years.

Probabilistic Resource Assessment of The Ulumbu Geothermal Field, East Nusa Tenggara, Indonesia

DOI:10.17014/ijog.9.2.183-193A resource assessment of the Ulumbu Geothermal Field, East Nusa Tenggara, Indonesia, is proposed here. The fundamental issue of reserve estimation is determining the optimum capacity to be installed (field size) that affects the decision-making in geothermal projects. The reservoir numerical model and heat stored method are the most appropriate tools for geothermal resource assessment. Therefore, the hybrid numerical simulation and heat stored methods, coupled with the probabilistic approach, are applied to Ulumbu. Based on the calibrated numerical model, the estimation of the reservoir is divided into the steam zone and liquid reservoir. The energy reserve of the Ulumbu is estimated by Monte Carlo simulation with the results P10-P50-P90 are 71 MWe, 95 MWe, and 127 MWe, respectively

Geothermal Resources of the Asian Continent: A regional Assessment

The present work is an attempt for regional assessment of geothermal resources of the continental region of Asia. It is based on integrated analysis of the results of experimental data on heat transfer by conduction as well as hydrothermal and magmatic processes in the upper crust. The current compilation makes use of geothermal data reported at the website of IHFC but also estimates based on available information on occurrences thermal springs and volcanic events. The resource assessment has been carried out for 11260 sites distributed in 46 countries. A modified method of magmatic heat budget (MHB) has been employed in deriving estimates of geothermal resources in areas of recent volcanic activity. These datasets were reevaluated and spatially gridded using kigrid interpolation to construction of regional distribution maps of geothermal resources and interpreted on the basis of available information on tectonic setting and geological characteristics. According to results obtained the total resource base (RB) is estimated to be 47024 ± 4525 GJ. The mean resource base per unit area (RBUA) is 1765 GJ. The most prominent features in geothermal maps are the significantly high values of resource base of greater than 1000 GJ in countries such as Japan, Indonesia, China, Bhutan, Nepal and Pakistan. In addition, vertical distributions of temperatures were calculated in such areas for depths reaching down to 6 km. The results obtained indicate potential availability of high temperature resources in vast regions of the Asian continent.

Methods for geothermal resource assessment of hot dry rock: A case study in the Gonghe Basin, China

Hot dry rock (HDR) geothermal resources are renewable energy source. Many of the findings of HDR resource evaluations have been used in energy planning and EGS design. However, to assess the amount of HDR resources in different locations, a consistent classification scheme and evaluation methods are still lacking. Considering geological credibility and economic feasibility, HDR resources are separated into three categories: vision, reserve, and exploitable. Vision and reserve are stationary resources that can be evaluated using the volume technique, and the exploitable resources can be evaluated using the numerical simulation approach. The HDR vision resource of the Gonghe Basin is evaluated to be 4.076 × 1022 J, and the reserve resource of the Qiabuqia HDR mass is evaluated to be 2.11 × 1020 J. At the Qiabuqia HDR development site, a discrete fracture network (DFN) model is applied for numerical simulation computations, which is based on the notion of local thermal nonequilibrium. The K1 and K2 wells produce varying amounts of heat due to the heterogeneous features of the fractured medium model, which is primarily due to differences in fracture density, heat exchange area, and fluid migration pattern. The categorization system and assessment technique can be used as a guide for evaluating HDR resources in the future.

Assessing the Geothermal Resource Potential of an Active Oil Field by Integrating a 3D Geological Model With the Hydro-Thermal Coupled Simulation

Assessment of available geothermal resources in the deep oil field is important to the synergy exploitation of oil and geothermal resources. A revised volumetric approach is proposed in this work for evaluating deep geothermal potential in an active oil field by integrating a 3D geological model into a hydrothermal (HT)-coupled numerical model. Based on the analysis of the geological data and geothermal conditions, a 3D geological model is established with respect to the study area, which is discretized into grids or elements represented in the geological model. An HT-coupled numerical model was applied based on the static geological model to approximate the natural-state model of the geothermal reservoir, where the thermal distribution information can be extracted. Then the geothermal resource in each small grid element is calculated using a volumetric method, and the overall geothermal resource of the reservoirs can be obtained by making an integration over each element of the geological model. A further parametric study is carried out to investigate the influence of oil and gas saturations on the overall heat resources. The 3D geological model can provide detailed information on the reservoir volume, while the HT natural-state numerical model addressed the temperature distribution in the reservoir by taking into account complex geological structures and contrast heterogeneity. Therefore, integrating the 3D geological modeling and HT numerical model into the geothermal resource assessment improved its accuracy and helped to identify the distribution map of the available geothermal resources, which indicate optimal locations for further development and utilization of the geothermal resources. The Caofeidian new town Jidong oil field serves as an example to depict the calculation workflow. The simulation results demonstrate in the Caofeidian new town geothermal reservoir that the total amount of geothermal resources, using the proposed calculation method, is found to be 1.23e+18 J, and the total geothermal fluid volume is 8.97e+8 m3. Moreover, this approach clearly identifies the regions with the highest potential for geothermal resources. We believe this approach provides an alternative method for geothermal potential assessment in oil fields, which can be also applied globally.

Assessment of Geothermal Water and Energy Resources Based on Fewer-Steps Calculating Methods: A Case Study of Reshuiwei Geothermal Field

Assessment of Geothermal Water and Energy Resources Based on Fewer-Steps Calculating Methods: A Case Study of Reshuiwei Geothermal Field

Deep Geothermal Resource Assessment of Early Carboniferous Limestones for Central and Southern Great Britain

Deep Geothermal Resource Assessment of Early Carboniferous Limestones for Central and Southern Great Britain

Integrated assessment and prospectivity mapping of geothermal resources for EGS in Brazil

Studies in Brazil related to geothermal resources have been carried out mainly by the National Observatory. Based on the results vast areas of Brazil have been delimited with a surface heat flow of over 60 mW/m2 and an excess temperature above 100 °C at depths between 3 and 6 km. The nature of the heat source and the mode of heat dissipation in these areas are largely unknown. Geothermal resources that might be associated with these areas can occur in hot sedimentary aquifers (HSA) and units of hot dry rocks (HDR) that are hosted, respectively, in intracratonic sedimentary basins and high heat producing granites (HHPG). The focus of our study is on finding resources of high enthalpy (above 150 °C) in HHPG, which regardless of their hydrological properties (porosity, permeability) could be considered as potential targets for enhanced geothermal systems (EGS). The structural provinces of Tocantins and Borborema were chosen as pilot regions based on both the indication of HDR and the wealth of open access georeferenced information. A comprehensive database was compiled and processed under GIS that includes geology, faults, soil typology, radiogenic heat, heat flow and geothermal gradient from wells, thermal spring locations, airborne gamma-ray spectrometry and magnetic surveys, terrestrial gravimetric surveys, and earthquake locations. In parallel, various critical factors were defined primarily to identify and characterize the most promising HHPG under insulating sedimentary rocks for EGS. These critical factors were grouped into three main categories labelled as: ‘thermal source’, ‘thermal insulation’ and ‘active pathways’. In the absence of exploratory data on existing EGS in Brazil these critical factors were used in this study along three separate work streams to develop a knowledge-driven model based on fuzzy logic for improving the knowledge on the prospectivity of geothermal resources. The developed model was further tested for its validation. The selected approach is expected to be applicable to mapping areas with EGS potential in other regions with similar geology and open access georeferenced databases.

Grey water footprint assessment of geothermal water resources in the southeastern Anatolia region

Grey water footprint assessment of geothermal water resources in the southeastern Anatolia region

Catalog of Enhanced Geothermal Systems based on Heat Sources

AbstractIt is common sense that a deeper well implies higher temperature in the exploration of deep geothermal resources, especially with hot dry rock (HDR) geothermal resources, which are generally exploited in terms of enhanced geothermal systems (EGS). However, temperature is always different even at the same depth in the upper crust due to different heat sources. This paper summarizes the heat sources and classifies them into two types and five sub‐types: crust‐origin (partial melting, non‐magma‐generated tectonic events and radiogenic heat production), and mantle‐origin (magma and heat conducted from the mantle). A review of global EGS sites is presented related to the five sub‐types of heat sources. According to our new catalog, 71% of EGS sites host mantle‐origin heat sources. The temperature logging curves indicate that EGS sites which host mantle‐origin magma heat sources have the highest temperature. Therefore, high heat flow (&gt;100 mW/m2) regions with mantle‐origin magma heat sources should be highlighted for the future exploration of EGS. The principle to identify the heat source is elucidated by applying geophysical and geochemical methods including noble gas isotope geochemistry and lithospheric thermal structure analysis. This analytical work will be helpful for the future exploration and assessment of HDR geothermal resources.