Geothermics最新文献

Subsurface reservoir temperature of a geothermal province is popularly estimated using various geothermometers but it is necessary to examine the suitability of them. Present work studies the performances of five popular geothermometers Na-K, Na-K-Ca, Quartz, Chalcedony and K-Mg to forecast the reservoir temperature of 148 geothermal springs located in different parts of the world. The predicted temperature of the geothermometers have been compared with the bottom whole temperature (BHT) of the wells drilled in those geothermal fields to check the accuracy of the predictions.

The results show that performance of a particular geothermometer is significantly affected by the type of rocks in a geothermal reservoir. Na-K geothermometer provides highest accuracy for the basaltic and sandstone reservoir rocks with average errors 15 % and 11 % respectively. The quartz geothermometer also provides almost equally good prediction for sandstone. The best result for a granitic reservoir rock is obtained by Na-K-Ca with an average error about 15 %. The carbonate reservoir rocks are the most difficult reservoir rock to use any geothermometer as lowest error of prediction using any geothermometer is about 26 %. The chalcedony performed the poorest among all geothermometers and is not recommended for any reservoir rock types under considerations. Thus, the study on global geothermal fields shows that the reservoir rock type must be considered to select a geothermometer else it may cause very high error in prediction of reservoir temperature. However, none of the geothermometer could produce error less than 10 %. It is worth noting that the present study though establishes the suitability of a geothermometer for a particular lithology, it does not explore the rationale for such a suitability.

The Alpehue Hydrothermal Field (AHF) near the Sollipulli Volcano in the Southern Volcanic Zone of Chile shows promise as a significant geothermal resource. A comprehensive geothermal exploration survey was conducted, including the evaluation of hydrothermal gases, geothermometer calculations, and CO₂ flux measurements, to assess the AHF's geothermal potential. Our results indicate that the hydrothermal gasses at the AHF primarily originate from primitive, mantle-derived sources, with some contribution from crustal sediments. Two different CO₂ populations of fluxes were identified. One corresponds to the background emission related to the soil biological activity (mean ∼7.7 g·m⁻²·d⁻¹), and the other, much more significant, emanates from an endogenous source related to the Alpehue hydrothermal reservoir (mean ∼461 g·m⁻²·d⁻¹). Reservoir temperatures were calculated using gas geothermometry yielding average temperatures of 249 °C. The calculated heat flow rate of the AHF is approximately 3.3 MW and the heat flux corresponds to 156 thermal MW⋅km⁻², which could be considered a medium geothermal potential comparable to other systems worldwide. Although further studies are needed to fully address its exploitability, this study presents favorable characteristics of the AHF that make it a promising avenue for further exploration.

Investigating hydrogeochemistry in geothermal fluids is a valuable approach to comprehending the intricate process of deep geothermal water circulation and uncovering the underlying mechanism behind the formation of geothermal systems. The article presents a thorough investigation of the hydrogeochemical and stable isotope characteristics of geothermal fields situated on both the southern and northern sides of the Xi'an depression. This study elucidates the process and progression of deep geothermal water, thereby offering theoretical backing for the exploitation of geothermal resources in the Weihe Basin. The data indicates the following points. The predominant chemical composition of geothermal water consists of SO₄·HCO₃–Na and SO₄·HCO₃·Cl–Na types. The ionic components are mainly impacted by the dissolution of Silicate and evaporite minerals, as well as the alternating adsorption of cations. The geothermal water is replenished by rainfall from the Qinling Mountains, with the recharge elevation varying from 677.94 m to 1,467.65 m. Various techniques are employed to determine the temperature and depth of the reservoir, which helps to understand the behavior of the deep thermal water. Thus, the study determines that the geothermal water in the Xi'an depression originates from laminar-controlled geothermal reservoirs, lateral flow recharge, and an unusual deep thermal structure.

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.