Geothermics最新文献

Geothermal energy could play a pivotal role in decarbonisation as it can provide clean, constant base-load energy which is weather independent. With a growing demand for clean energy and improved energy security, geothermal resources must be quantified to reduce exploration risk. This study aims to quantify the untapped resource-potential of the Cornubian Batholith as a geothermal resource for power generation and direct heat use. Recent field work, laboratory measurements and petrophysical characterization provides a newly compiled dataset which is inclusive of subsurface samples taken from the production well of the United Downs Deep Geothermal Power Project. Deterministic and probabilistic calculations are undertaken to evaluate the: total heat in place, recoverable resource, technical potential and potential carbon savings. The Cornubian Batholith is considered a petrothermal system which may require stimulation as an enhanced geothermal system. This study shows the batholith has significant heat stored of 8988 EJ (P50), corresponding to 366 EJ recoverable and a technical potential of 556 GW_th. When evaluating the potential for power generation (i.e., electricity) the P50 is 31 GW_e. The total carbon savings when generating electricity (P50) equates to 106 Mt.

The intense investment demand in the geothermal sector in Afyonkarahisar province in recent years has enabled the utilization of geothermal waters such as district heating and greenhouse heating, electricity generation, and spa facilities and accelerated the exploration of new geothermal areas in the region. In this study, the Salar (Afyonkarahisar) region's geothermal potential was investigated using the mineralogy and geochemistry of hydrothermal alteration, hydrogeochemistry, and resistivity models obtained from magnetotelluric data. The Salar region is located within the Afyon-Akşehir Graben (AAG) and 10 km south of Afyonkarahisar province. The most important manifestations of the geothermal system are the geothermal water at temperatures of 25 °C and 31 °C obtained from the boreholes and hydrothermal alteration in Salar. Afyon volcanoclastics are reservoir rocks. Smectite and illite are the most important clay minerals in the hydrothermal alteration zones. The transformation from volcanic glass and alkali feldspar to smectite and illite reflects neutral-alkaline alteration conditions in felsic rocks. The clay minerals' stable isotopes (δ_D and δ18O) indicate hypogene conditions. Discharge temperature, electrical conductivity and pH of Salar region geothermal waters vary from 25 to 31 °C, 320–357 µs/cm, and 6.8, respectively. The Salar geothermal waters are Ca-(Na)-HCO₃ type chemically. The electric resistivity models reveal shallow low resistivity (10 < ρ < 80 Ωm) layer related to the alluvium, Gebeceler formation, and Afyon volcanoclastics and deeper high resistivity (80 <ρ < 200 Ωm and ρ > 200 Ωm) layer based on Deresinek and Değirmendere formation respectively. The difference in electrical resistivity arises from the geothermal waters and hydrothermal alteration zones, influenced by the AAG tectonics.

The stable isotopes (δ_D and δ18O) and alpha cristobalite geothermometer calculations indicate that the condition of the temperature in the active and fossil geothermal systems in the Salar does not change, and the condition of the temperature is between 44 °C and 112 °C.

Most of the literature concerning geothermal energy in Saudi Arabia has focused on power generation applications. This paper investigates the potential of utilizing ground-source heat pump (GSHP) with vertical borehole heat exchangers in residential buildings in the various climate zones and subsurface geologies of Saudi Arabia. Thermal loads of a typical residential building in Saudi Arabia were generated using eQuest software, then used in a model of GSHP system in TRNSYS. The performance and economics of the GSHP system was evaluated and compared with a typical air-source heat pump (ASHP) system for each location. The total borehole lengths in all zones were determined using the cooling load (the dominant load). The potential for employing GSHP systems was found to be not uniform across Saudi Arabia. The required length of the GHE ranged between 12 and 148 m/kW of cooling. The annual energy saving when employing GSHP instead of ASHP systems varied between 3 % to 19 %, and the building's electricity peak demand could be reduced between 5 % to 43 %. Although GSHPs reduced electrical and maintenance costs, their high drilling cost makes them economically unattractive under the present electric utility charge in Saudi Arabia.

This study focuses on the Pannonian Basin, specifically in Szentes, Hungary a region of significant geothermal potential, with particular emphasis on the Dunántúl Group; a collective name for the Zagyva and Újfalu formations, which consists of slightly consolidated delta-front sandstone sediments. This research is pivotal in understanding the challenges associated with clogging in geothermal wells, a problem that has led to the premature shutdown of injection wells in the region. Our approach integrates classical petrophysical and mineralogical methods with advanced techniques such as micro-Computed X-Ray Tomography imaging, 3D image analysis, and digital rock simulations. Our findings indicate that the target geothermal rock formations within the Dunántúl Group exhibit high porosity (27–31 %) and variable permeability (60–400 mD), dependent on the location and specific characteristics of the formation. Our micro-CT analyses further identified that the presence of fine-grained materials in smaller pores and generally weak cementation of grains substantially contributes to these challenges.

High-temperature aquifer thermal energy storage (HT-ATES) systems can store renewable-based or waste heat in the subsurface on a seasonal scale and may thus reduce the carbon footprint of future heat supply systems. Thermal recovery, i.e. the ratio of extracted to injected heat over one cycle, is required in a pre-application assessment because it determines the operational and economic viability of a HT-ATES system. The induced temperature changes in the subsurface are required to obtain the legal permits and are of interest for the design of a monitoring network. However, uncertainty in our knowledge on subsurface hydraulic and thermal parameters translates into uncertainties of the expected thermal recovery and the temperature changes induced during HT-ATES operation. In order to address these uncertainties for a case study in Hamburg, Germany, we use numerical modeling of the coupled thermo-hydraulic processes during the design stage of a HT-ATES system, based on a realistic load curve and the local geological setting of the storage aquifer. An ensemble of 50 scenarios was parameterized based on site-specific parameter uncertainties using Latin hypercube sampling to reflect the global parameter distributions, and the HT-ATES operation was simulated over a period of 26 years in each case. Most of the scenarios show high thermal recoveries with a median of 89 % in the 26th year, with thermal recovery most sensitive to the vertical hydraulic conductivity. The expected temperature distribution is well defined by the ensemble of model simulations, with far-field temperature changes reaching for hundreds of meters and showing greater variability between scenarios than those in the near-field region of the warm HT-ATES well on the tens of meters scale. Locations with large temperature differences between scenarios are identified as suitable for the placement of temperature monitoring wells. The presented work thus contributes directly to the design and permitting of HT-ATES systems and can also be used for uncertainty assessment of future HT-ATES plants and the identification of suitable monitoring setups.

Hydrogeochemical characteristics can reflect important information on the circulation processes of geothermal fluids, reservoir temperatures, etc., which are essential for exploring geothermal field evolution and the rational development of geothermal resources. 23 sets of water samples were collected from Huangshadong and adjacent geothermal fields. Major cations and anions, hydrogen and oxygen isotopes, and ${}^{14}C$ activities were analyzed to investigate the hydrogeochemical characteristics of geothermal fluids and their formation mechanisms. Hydrogen and oxygen isotope analysis and major element chemistry indicate that the geothermal waters in the study area are mainly recharged by meteoric water. The chemical facies of the geothermal waters are mainly $Na-HC{O}_3$ and $Ca-HC{O}_3$, and most of the geothermal waters have high $N{a}^{+}$ contents, which are attributed to the involvement of albite in water-rock interaction and the replacement of $N{a}^{+}$ in rocks by $C{a}^{2+}$ or $M{g}^{2+}$ in water. Geothermometry of geothermal waters suggests that the reservoir temperatures are between 140-150 ℃, and the geothermal water circulation depths range from 2.0 to 4.3 km. The residence time of up to 17.3ka for geothermal water likely suggests the earliest precipitation recharge during the Late Pleistocene. Major element chemistry and hydrogen and oxygen isotope systematics indicate essential information on the origins of geothermal waters and water-rock interaction processes and provide a more comprehensive understanding of the geothermal system in Huangshadong and adjacent areas of Guangdong province.

The EGS Collab project acquired continuous active-source seismic monitoring (CASSM) data before, during, and after hydraulic stimulations at the first testbed at the depth of 4850 ft (1478 m) at the Sanford Underground Research Facility in Lead, South Dakota, for monitoring fracture creation and evolution. CASSM acquisition was conducted using 24 hydrophones, 18 accelerometers, and 17 piezoelectric sources within four fracture-parallel wells and two orthogonal wells. 3D anisotropic traveltime tomography and anisotropic elastic-waveform inversion of the campaign cross-borehole seismic data show that the rock within the stimulation region is a heterogeneous horizontal transverse isotropic medium. We use these inversion results as the initial models and apply 3D anisotropic first-arrival traveltime tomography and 3D anisotropic elastic-waveform inversion to the CASSM data acquired after each stimulation in May, 2018 and December, 2018. We observe the spatiotemporal evolution of seismic velocities and anisotropic parameters caused by hydraulic fracture stimulations, showing the regions of rock alternation caused by hydraulic fracture stimulation.

The fracture-dominated convection heat transfer behavior is commonly involved in the development, utilization and storage of thermal energy in fractured rock engineering. An experimental system assembled by a peristaltic pump drive, a liquid preheater and an electric blast drying oven is developed to quantify the effect of fracture roughness on the convection heat transfer characteristics. The overall heat transfer coefficient (OHTC) and the amount of heat transfer quantity from six fracture samples with different inlet temperatures and flow rates are calculated by the data acquisition at five observation points. In general, the average convective heat transfer efficiency between water and rock decreases gradually with time, and then enters a stage of thermal equilibrium while the temperatures at the five observation points become constant. The increasing flow rate can lead to the gradual increase of the OHTC and the slowdown of its growth rate. The OHTC is negatively correlated with the inlet temperature. With the increase of fracture surface roughness, the dominant flow effect is significantly enhanced, which leads to the weakening of heat transfer characteristics and the gradual reduction of OHTC. Finally, the heat transfer quantity decreases with the increase of roughness, and exists an inflection point with the flow rate.

Geothermal power plants are among the most important renewable energy power plants owing to their high-capacity factors and integrated utilization possibilities. Currently, these power plants utilize geothermal fluid to generate electricity. Although their emissions are lower than those of conventional power plants, gasses such as CO₂ and H₂S are released into the air from the cooling towers, particularly in flash-type geothermal power plants

To reduce the emission of CO₂ gas released from geothermal power plants, reinjection studies have mainly been carried out around the world. These types of studies require extensive analysis of underground fracture systems, detailed geosciences, and the reservoir studies. However, these studies are considered risky and expensive for most plant operators because possible changes in underground fracture systems may affect the productivity of geothermal production zones. In terms of the environmental impact, hydrogen sulfide is a more harmful gas than CO₂. Effective H₂S removal methods cannot be widely used, except in areas with extremely high concentrations, because they commonly incur significant costs for plant operators. Effective H₂S removal methods are not widely available except for geothermal sites with high concentrations. The fact that local limit values can be exceeded in geothermal power plants with relatively low H₂S concentrations, such as geothermal power plants in Türkiye, pushes plant operators to find new low-cost solutions due to high operation costs. For this reason, a treatment method that can be applied at every site and whose cost is not too high has not yet been put forward. However, NaOH is used for this purpose in geothermal fields such as steam-dominated Geyser field to increase the pH values in geothermal wells, which has been producing for a long time.

In this study, field tests were carried out with five different chemicals and pure water to examine the reduction of non-condensable gasses in a geothermal power plant located in the Kızıldere (Denizli, Türkiye) geothermal field, one of the most important geothermal fields in the world. According to this, the capture of these gasses is technically possible using chemical methods, with a performance of up to 70 % observed in CO₂ gas capture.

However, although it is possible to capture 70 % of non-condensable gasses with such chemical methods, the consumable cost of the operation is quite high.

The Borehole Heat Exchanger (BHE) plays a pivotal role in enhancing heat exchange efficiency within Ground Source Heat Pump (GSHP) systems. The accurate prediction of the BHE's outlet fluid temperature is crucial for optimizing GSHP performance, energy storage, and resource conservation. However, conventional machine learning methods encounter challenges in manual feature extraction, learning complex nonlinear relationships, and adapting to real-world scenarios. To address these limitations, this research proposes a crossbreed model integrating Convolutional Neural Network (CNN) and Recurrent Neural Network (RNN) architectures to forecast long-term outlet fluid temperature in BHE systems. The model framework encompasses data preprocessing, utilizing refined data in the CNN module for temporal feature extraction, subsequently passed to the RNN module to capture sequential and temporal patterns from each dataset. Specifically, the advanced CNN-RNN architecture is designed to establish a comprehensive input-output mapping, leveraging essential input features such as inlet fluid, ambient air, and subsurface temperatures at varying depths (0, 10, and 20 m). Performance evaluation metrics, including R², RMSE, MAE, and AARE, are employed to compare and assess prediction accuracy across various models, including LSTM, CNN, and SimpleRNN. The obtained results demonstrate the superior performance of the proposed model, achieving an RSME of 0.818, MAE of 0.642, AARE of 0.0305, and an R² value of 98.75 %. This surpasses the performance of traditional prediction models (LSTM, CNN, and SimpleRNN) by 3.01 %, 5.80 %, and 19.52 %, respectively. Notably, the remarkably low MAE of 0.642 exhibited by a CNN-RNN model underscores its capability to outperform traditional approaches, especially when handling large datasets. These findings emphasize the significance of the developed model in facilitating efficient operation, positioning it as a valuable tool for advancing the long-term sustainability of BHE systems.