Geothermal Zone Research Articles

3-D shallow crustal structure and offshore geothermal potential of the Aegean region of Türkiye from ambient noise tomography

The definition of the upper crustal structure is a necessary input in seismic hazard studies or in geothermal exploration projects. In this study, we use ambient noise tomography (ANT) to illuminate the 3-D crustal structure of the Aegean Region of Türkiye. The results allow us to identify tectonic control on seismic velocities and to image the shear-wave velocity (Vs) structure. In addition, our results characterize offshore-onshore geothermal potential in this region. Our data consists of 3-months of continuous ambient noise data recorded by 43 seismometers. The cross-correlation of seismic noise between station pairs was used to estimate Rayleigh wave pulses from which group velocity dispersion curves were derived. The results were used to estimate a group velocity dispersion curve for each cell in a square grid using tomography. Local dispersion curves were inverted to estimate a 1-D Vs profile for each cell. Integration of the results for all cells allowed us to build a 3-D Vs model of the studied region. Our Vs model is reliable for the upper 18 km of the crust. The Vs variations show narrow anticlines and basin-type wide synclines and sedimentary layers that correspond to the shallow crustal structure. An arc-shaped low velocity zone is identified to the west of the study area and is interpreted as a promising offshore geothermal zone. The southern coastal region of the investigated area also presents high hot fluid content in cracks and therefore has significant offshore geothermal potential. Our interpretation is in good agreement with available geophysical results and with the shallow crustal geometry reported in previous studies.

A state‐of‐the‐art review on geothermal energy exploration in Morocco: Current status and prospects

AbstractIn the last few decades, addressing the global challenge of implementation of strategies for renewable energy and energy efficiency has become crucial. Morocco, since 2009, has made a steadfast commitment to sustainability, with a particular focus on advancing the development of renewable energy resources. A comprehensive strategy has been formulated, centering on utilizing the country's energy potential to drive progress in this vital sector. Morocco is considered a country with abundant thermal water, indicating deep reservoirs with significant hydrothermal potential. Geothermal zones were selected based on the abundance of hot springs where water temperatures were high and geothermal gradients were significant. The abundance and importance of hot springs, combined with recent volcanism and ongoing non‐tectonic activity linked to alpine orogeny, strongly suggest that these regions are promising reservoirs for geothermal energy. This great potential also extends to neighboring countries. In northeast and south Morocco, the temperature of thermal water ranges from 26 to 54°C. This study serves as an inclusive review of the geothermal potentialities in Morocco.

Geoelectrical image of the Sabalan geothermal reservoir from magnetotelluric studies

The magnetotelluric (MT) survey of the Sabalan geothermal zone, which includes 22 stations along three traverse profiles across the main prospect zone, was conducted in 2007. The geophysical investigation utilized sharp boundary inversion of processed MT data due to the high contrast of electrical resistivity between embedded layers. This method was preferred to suppress the smeared-out impact of the smooth inversion algorithm on retrieving geological layering. The analysis of MT data led to the use of a 2D inversion algorithm to visualize the geothermal reservoir. Additionally, the geoelectrical strike of the main geothermal target was determined, showing some inconsistency across the profiles. The simulation of synthetic numerical models is conducted to evaluate the effectiveness of sharp boundary inversion compared to a smooth algorithm in sharp gradient mediums, specifically in terms of electrical characteristics, for plausible geothermal scenarios. The Finite Element method (FEM) was employed to construct these models, followed by running the 2D forward and inversion processes. The meshing and initial parameters of the modeling were set based on information obtained from prior geological and geophysical investigations. A sharp boundary inversion can be accurately implemented by introducing layering constraints along each profile surrounding the probable sought geothermal reservoir target. These layering constraints encompass the conductive cap, topsoil, and basement rocks, which are the key components of a plausible geothermal configuration. The results of the comparison indicate that the sharp boundary inversion technique effectively restored the boundary between neighboring layers that had significant differences in electrical resistivity. This was achieved when the smoothing algorithm failed to produce an accurate representation of the layered model. Ultimately, conceptual geological models were developed to illustrate the plausible structures corresponding to each profile, focusing on the sought geothermal reservoir targets. It can be deduced that many misunderstandings in the smoothing inversion algorithm will be omitted if the sharp boundary algorithm is used in highly electrical gradient structures. Based on the outcomes, a trachyandesite, andesite, and altered andesite reservoir exists at an elevation of 1600 to −2000 m. The reservoirs were recovered precisely with sharp and discriminable interfaces. Therefore, accurate interfaces led us to determine the conductive cap, heat source, and topsoil stacking as the main components of the geothermal system.

Elemental assay of the fumarolic microecology of the Los Azufres (México) volcanic complex using nuclear analytical techniques

The elemental composition of the mantle is a key factor for the understanding of the science of the earth’s interior. However, the direct sampling of the mantle is a difficult and involved task. Fumarolic vapours carry a certain imprint of the mantle composition but are also relatively difficult to sample directly given their high temperature and acidity. Many terrestrial fu- marolic vents are colonized by extremophilic mosses that absorb the vapours and become repositories of the mantle elements brought up by the vapours. The elemental composition of the niche ecology of the fumarole therefore may serve as a near “proxy” for the deep-earth elemental profile of the region. Our study concerns the elemental composition of fumarolic plants, their rhizospheric soil, hydrothermal sediment and volcanic substrate collected from three geothermal microecological sites of the Los Azufres volcanic complex of Mexico. This work presents the results for the heavy elements (HE) Cd, Hg, Pb, Th and U that have been determined using the nuclear analytical techniques of Polarized Energy Dispersive Xray Fluorescence (PEDXRF) spectrometry, Instrumental Neutron Activation Analysis (INAA) as well as Inductively Coupled Plasma Mass spectrometry (ICPMS). The distributions of these HE in the aforesaid biogeochemical matrices are examined and rationalized with respect to possible mechanisms of their deposition. Comparisons with literature reports of the HE composition of fumarolic sulphur deposits and fumarolic vapours of the volcanoes of the Kuril Islands and geothermal aquifers of Iceland, are made. The HE composition is found to vary considerably by the geographic location of the fumarole. However, the trend of the concentrations of these 5 HE is found to be approximately the same for the fumarolic plants of Los Azufres as with the fumarolic vapours of the Kuril volcanoes the displacement being only in the magnitudes. Consequently, the concentrations of these 5 HE in the fumarolic plants are direct qualitative analogues of the vapours of those particular fumaroles of Los Azufres and thereby of the deep-earth geochemistry of that particular geothermal zone.

Shallow and deep geothermal water sources identification in Unai geothermal field, Gujarat, India with applications of Magnetotelluric (MT)

The aim of this study is to conduct and examine the results of a Magnetotelluric (MT) survey in Unai, Gujarat, India for geothermal prospect identification. At Unai, the data was acquired, processed, and interpreted in the form of 2D and 3D MT surveys. Data were acquired at 56 stations in uniformly spaced profiles along the ENE-WSE direction (geological strike direction) with a station spacing of 2 km. Qualitative and quantitative data understanding has been done for geothermal prospect identification. Deep and shallow 1D and 2D models of electrical resistivity were made, which suggests the presence of a geothermal aquifer. This is corroborated by polar and skew tipper diagrams. The one-dimensional Occam models and two-dimensional conjugate gradient models confirm the presence of a low resistivity anomaly near the surface ranging from the depth of 100–700 m. This suggests the presence of a shallow geothermal zone. Apart from the shallow geothermal prospect, this study also delineates a deep conductive body which may be attributed to a matured geothermal reservoir. For a better understanding of the prospect geoelectrical cross sections are analysed from a depth of 10 m to 15 km. The MT cross-sections show the presence of geological features such as a series of faults. These faults form horst and graben in nature and may act as a good trap for the shallow reservoirs.

Uji aktivitas antibakteri ekstrak daun jamblang dari kawasan geotermal: Kadar Hambat Minimum (KHM) dan Kadar Bunuh Minimum (KBM)

Background: Jamblang is one of the plants that have the potential to be an antibacterial agent. Jamblang plants can grow in the geothermal area of Ie Seum Aceh Besar. This area has higher soil temperature and pH compared to areas outside of geothermal zones. Environmental conditions influence the chemical composition and pharmacological activities of a plant. Jamblang leaves contain several chemical compounds, including polyphenols, flavonoids, triterpenoids, saponins, and tannins, which function as antibacterials.Objectives: This research aims to determine the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of jamblang leaf extract obtained from the geothermal area of Ie Seum Aceh Besar against Staphylococcus aureus.Methods: The MIC and MBC testing will be conducted using the dilution method with extract concentrations of 1,56%, 3,12%, 6,25%, 12,5%, 25%, 50%, and 100%. The negative control will use distilled water, while the positive control will use amoxicillin. The medium used in this research is Mueller Hinton Agar (MHA).Results: The results indicate that the Minimum Inhibitory Concentration (MIC) of the Jamblang leaf extract grown in the Ie Seum Aceh Besar geothermal area is 50%. In comparison, the Minimum Bactericidal Concentration (MBC) is 100%.Conclusion: The ethanolic extract of jamblang leaves from the geothermal area of Ie Seum Aceh Besar, at a concentration of 50%, inhibited the growth of Staphylococcus aureus. In comparison, at a concentration of 100%, it killed the Staphylococcus aureus.

Ambient noise tomography of the Aegean region of Türkiye from Rayleigh wave group velocity

We have studied Rayleigh wave group velocities beneath the Aegean region of Türkiye using ambient noise tomography. Noise data were gathered from 43 broadband seismic stations belonging to three permanent broad-band arrays. The cross-correlation method was used to estimate empirical Green’s functions. Group velocities of the fundamental mode Rayleigh waves were determined using multiple filter technique. We measured dispersion for each station pair in a period range of 2–12 s and computed maps of group velocity distribution using the fast marching surface tomography method. The group velocity maps correlate well with the geological and tectonic features of the region, displaying low velocities for the Quaternary alluvial basins, moderate velocities for Cretaceous rocks, and high velocities for the regions where gneiss and granitoid rocks outcrop. Low velocity anomalies may be associated with the grabens and horsts formed by faulting and to deep mantle flow. We detect potential offshore geothermal zones in Izmir and Candarli Bay. The information from broad-band networks improves the resolution of crustal surface wave velocity structures, particularly for shallow depths. This improvement will support the assessment of seismic hazard, as the shallow layers of the crust contribute significantly to seismic activity.

Expert-driven play Fairway Analysis applied to the Azufral Volcano Geothermal Area in southwestern Colombia

The Azufral Volcano is a polygenetic volcanic structure formed by Pliocene-Pleistocene andesites, and upper Pleistocene-Holocene lava domes and pyroclastic deposits. Warm and hot springs, fumaroles, hydrothermal eruption craters, and hydrothermal alteration zones are identified at Azufral Volcano and its surroundings. The area around Azufral Volcano has been affected by two potentially active fault systems (striking SW-NE and NW-SE) and shallow (< 21 km depth), low magnitude seismicity (< M3.3). For this study, an expert-driven Play Fairway Analysis at the Azufral Volcano Geothermal Area was conducted (∼ 520 km2). This Play Fairway Analysis was performed using existing data collected by the Colombian Geological Survey (Servicio Geológico Colombiano) for previous exploration efforts in the area, such as geologic, geophysical, and geochemical datasets. The results of our work include 2D permeability, heat, and geothermal favorability models. These results highlight that the area with the most potential to host geothermal fluids is centered underneath the volcanic edifice (∼ 8 km2): an elongated area that coincides with the intersection of the regional Cali-Patía and local Río Guabo and Azufral-Sapuyes fault zones. The results also suggest that the area with the most geothermal favorability is likely related to the potential upflow of the geothermal system, and the warm springs surrounding the volcano are likely related to the structurally controlled outflow. Finally, our results illustrate the value of applying the Play Fairway Analysis approach at a local scale to integrate different types of data and to identify areas with the most potential to host geothermal resources in geothermal zones.

Geochemical and H–O–Sr–B isotope signatures of Yangyi geothermal fields: implications for the evolution of thermal fluids in fracture-controlled type geothermal system, Tibet, China

High-temperature hydrothermal systems are mainly distributed in the north–south graben systems of southern Tibet as an important part of the Mediterranean–Tethys Himalayan geothermal belt in mainland China. As the largest unit capacity and second stable operating geothermal power station in China, Yangyi is the fracture-controlled type geothermal field in the center of Yadong–Gulu Graben. In this paper, hydrogeological and hydrochemical characteristics, isotope composition (δD and δ18O, 87Sr/86Sr and δ11B) of borehole water, hot springs, and surface river samples were analyzed. From the conservative elements (such as Cl− and Li+) and δD and δ18O values, the geothermal water of the Yangyi high-temperature geothermal field is estimated to be of meteoric origin with the contributions of chemical components of the magmatic fluid, which is provided by partially molten granite as a shallow magmatic heat source. According to logging data, the geothermal gradient and terrestrial heat flow value of the Yangyi high-temperature geothermal field are 6.48 ℃/100 m and 158.37 mW m−2, respectively. Combining the hydrothermal tracer experiment, 87Sr/86Sr and δ11B ratios obtained with gradually decreasing reservoir temperatures from the Bujiemu stream geothermal zone to Qialagai stream geothermal zone, we suggested the deep geothermal waters were mixed with local cold groundwater and then flow northeastward, forming the shallow reservoir within the crushed zone and intersect spot of faults in the Himalayan granitoid. Furthermore, in the process of ascent, the geothermal water is enriched in K+, Na+, and HCO3− during the interaction with underlying Himalayan granitoid and pyroclastic rocks that occur as wall rocks. The detailed description and extensive discussion are of great significance for the further exploitation and utilization of north–south trending geothermal belts in Tibet.

Origin and evolution of Li-rich geothermal waters from the Kawu geothermal system, Himalayas: based on hydrochemistry and H-O, Li isotopes

ABSTRACT There are 25 Li-rich geothermal fields (>15 mg/L) are displayed throughout nine geothermal zones in Tibet. The Kawu geothermal system is one of the representative high-enthalpy and Li-rich geothermal systems and is located in the Skaya dome, the Himalayas. Their boiling and hot and cold waters are Cl-HCO3-Na and HCO3-Ca types, respectively. The parent geothermal fluids are characterized by high Na, Cl, B, Si, As, Li, Rb+, Cs+ and F, and the Cl− concentration and enthalpy of the parent geothermal liquid are 515 mg/L and 1,485 J/g, respectively (corresponding to a temperature of 323.5°C). The stable oxygen and hydrogen isotopic compositions of geothermal fluids range from −19.7 to −23.4‰ and −155 to −181.2‰, indicating that the ratio of magmatic water mixed into geothermal fluid is between 11.7% and 19.5%. The lithium content in the geothermal system is high (13.04 to 20.8 ppm), but the δ7Li is relatively low (1.06 to 1.72‰). The high Cl, Li and B contents, constant Cl/Li and Cl/B ratios and low δ7Li indicate that they mainly originate from magmatic fluid, rather than from water rock reaction with the leucogranite and gneiss. While ascending from the reservoirs to the surface, the parent geothermal fluids gradually mixed with the meteoric waters infiltrated via brittle tensional small-scale faults, in turn forming four cooling processes upwelling patterns, i.e. conductive cooling, adiabatic cooling, mixing with cold water, and the combination of these processes.

Characterizing the Size Distribution of Silver Nanoparticles Biofabricated Using Calotropis gigantea from Geothermal Zone

This research aims to synthesize silver nanoparticles (AgNPs) using an aqueous leaf extract of Calotropis gigantea obtained from the geothermal manifestation Ie Seu-Um, Aceh Besar, Aceh Province, Indonesia. The C. gigantea leaf extract was mixed with AgNO3 solutions at concentrations of 2, 5, and 9 mM, respectively. The mixture was stirred at 80 rpm by a magnetic stirrer for 48 hours in the dark. The change in solution color indicated the reduction of Ag+ to Ag0. The resulting AgNPs synthesized using C. gigantea leaf extract (AgNPs-LCg) exhibited cloudy grey, reddish dark brown, and light brown colors when synthesized with AgNO3 concentrations of 2, 5, and 9 mM, respectively. The particle sizes of AgNPs-LCg had maximum frequencies at 246.98 nm (synthesized using AgNO3 2 mM), 93.02 nm (synthesized using AgNO3 5 mM), and 171.25 nm (synthesized using AgNO3 9 mM). The zeta potential values of AgNPs-LCg using 2, 5, and 9 mM AgNO3 were -41.9, -40.1, and -31.4 mV, respectively. Based on the solution color, nanoparticle size, and stability value of AgNPs, it can be concluded that the use of AgNO3 at 5 mM is optimal for the green synthesis process of AgNPs-LCg.

Development of a Quality Index to Evaluate the Impact of Abiotic Stress in Saline Soils in the Geothermal Zone of Los Negritos, Michoacán, Mexico

In recent years, salinity-induced soil quality impairment and the misuse of management practices have led to the reduced productivity of agroecosystems. This has prompted a search for simple and effective agricultural management strategies that improve the sustainability of agricultural production through soil quality assessments. In this context, the objective of this study was to establish an integrated soil quality index (SQI) by assessing the influence of different types of abiotic stress in two different seasons, using physical, chemical and biological indicators at three sites in the geothermal zone of “Los Negritos”, Michoacán, Mexico. Thirty-nine indicators related to soil fertility attributes and C, N, P, and S cycling—identified as the total dataset (TDS)—were evaluated. Principal component analysis (PCA) and the Spearman correlation matrix (r2 ≥ 0.6) were used to calculate the SQI using an integrated quality index (IQI) equation, with the indicators total nitrogen (TN), cation exchange capacity (CEC), lithium (Li), and zinc (Zn) identified as the minimum dataset (MDS). Significantly higher SQI values related to the better performance of soil functions were detected during the rainy season.

Gas Production Potential in Geothermal-Energy-Enhanced CH4–CO2 Swapping Processes

Carbon capture and storage has become a practice to reduce the greenhouse effect of carbon dioxide (CO2) on the global climate. Recent studies have generated increasing concerns about CO2 leakage from underground structures. This has called for more research on CH4–CO2 swapping in natural gas hydrate (NGH) reservoirs to lock CO2 in a solid state in underground structures. Because the CH4–CO2 swapping is too slow to be efficient, this study proposes to use geothermal energy to accelerate the process. This paper presents a technical feasibility analysis of using geothermal energy to assist CH4–CO2 swapping for simultaneously storing CO2 in NGH reservoirs and producing the dissociated natural gas. Mathematical models were developed to compute heat transfer from geothermal zones to NGH reservoirs. A case study was carried out using the data from an NGH reservoir in the Shenhu area, Northern South China Sea. The result of the case study indicates that heat conduction dictates the heat transfer process when the heat convection flow rate is less than 0.01 m3/s over a heat-releasing borehole length of 2,000 m. Heat convection can significantly accelerate the heat transfer inside the gas hydrate reservoir. The 15°C (designed gas hydrate dissociation temperature in the studied case) heat front will propagate to the upper and lower boundaries of the gas hydrate reservoir (39 ft or 12 m) in 220 days by heat conduction only. This time can be shortened to 140 days with the aid of a fluid convection rate of 0.005 m3/s. Geothermal heating can significantly increase the initial productivity of wells in heated gas hydrate reservoirs in CO2 swapping processes. When the gas hydrate reservoir is heated from 6 to 16°C, the fold of increase is expected to exceed five in the studied case. This study shows that CH4–CO2 swapping process using geothermal stimulation is a promising method for producing natural gas and locking CO2 permanently in NGH reservoirs. Further studies should first focus on investigations of the effect of CO2-hydrate formation on the CO2 mass transfer inside reservoirs.

Surface geochemical anomaly pattern of medium-to-high temperature geothermal systems in South China and its application

The existence of thermal storage will correspondingly increase the temperature of surrounding strata and promote the continuous expansion, volatilization, upward migration, and loss of gas in the strata. As a result, a low-concentration gas field will be formed in the strata above geothermal reservoirs. Geothermal reservoirs could in turn heat formation water and increase the solubility of soluble inorganic salts in the surrounding rocks and the total dissolved solids (TDS) content in the formation water. Since water can strongly wet and permeate strata, the dissolved inorganic salts migrate into upper strata along with water, giving rise to the formation of a high-concentration inorganic salt field in the strata above geothermal reservoirs. A higher geothermal reservoir temperature corresponds to more significant characteristics mentioned above. Therefore, a medium-to-high temperature geothermal system has a surface geochemical anomaly pattern of high inorganic salt concentrations and low gas concentrations (also referred to as the high-salt and low-gas pattern). This pattern is applied to the surface geochemical exploration of the two geothermal fields in Guangdong Province, i.e., the Huangshadong geothermal field in Huizhou City and the Xinzhou geothermal field in Yangjiang City, revealing low-concentration gas fields above both. The application results also show that the exposed thermal spring water in both geological fields has higher concentration of dissolved inorganic salt than the surface water and nearby seawater, forming high-amplitude anomalies on the surface above geothermal reservoirs. These characteristics, as well as the measured temperature at known geothermal wells, verify the validity of the high-salt and low-gas pattern of medium-to-high temperature geothermal systems proposed in this study. Moreover, the high-salt and low-gas pattern proposed predicts three favorable medium-to-high temperature geothermal zones in the surface geochemical exploration of the Shiba Basin near the Huangshadong geothermal field.

Who Lives in the Hot Heart of the Cold Sea? A New Species of Provanna (Caenogastropoda: Provannidae) from the Hydrothermal Zone of Piip Volcano, Northwestern Pacific

The benthic macrofauna of Arctic and subarctic seas is mainly represented by widespread species and is generally devoid of endemics. The exceptions are reduced habitats, such as cold seeps, hydrothermal areas, and wood falls, which include endemics of at least the species level. A detailed study and analysis of such endemics allows us to understand the mechanisms of colonization and to assess the age of the fauna of high-latitude marine regions. Here, the new species Provanna annae sp. nov. is described from the geothermal zone of the Piip volcano in the Bering Sea (subarctic Pacific) based on the morphological and molecular phylogenetic data. The new species appears to be the northernmost and one of the most shallow-water species among the known representatives of the family and is suggested to be endemic to the region. The new species is related to a group of Provanna species from reducing habitats off Japan. Composition of the gut content indicates that the new species bottom sediments. Bacteria are found on the gills of the mollusc and are probably symbionts that also provide nutrition. This type of mixotrophic feeding is rare in gastropods and may be a unique feature among Caenogastropoda.

A novel sustainable cooling system in a tunnel with high geotemperature: Concept and thermal performance

An increasing number of tunnels pass through the anomaly geothermal zones and inevitably encounter thermal engineering geological problems during tunnel operation. In order to efficiently eliminate the thermal damage, an efficient and energy-saving cooling system composed of borehole heat exchangers (BHEs) and thermal insulation layer in a high geotemperature tunnel is proposed. Taking Sangzhuling tunnel as an example, a 3D numerical model is established for analyzing the thermal performance of the cooling system, and is validated by the field measured data. The cooling effect of the cooling system in the high-geotemperature tunnels is proved to be remarkable in comparison with the tunnel having thermal insulation layer. Moreover, the effects of design parameters on the thermal performance are revealed during a 180-day heat extraction. The results show that a lower inlet temperature contributes to a shorter drop to the target tunnel ambient temperature. The effect of the cooling system is significantly improved as the borehole depth increases within a limited extent because the cooling effect cannot be infinitely improved by increasing the borehole depth. The thermal insulation layer plays a beneficial role in reducing the maximum ambient temperature and an adverse effect on the temperature reduction rate. These findings contribute to preliminary thermal performance estimation of the BHE cooling system in high-geotemperature tunnels without large-scale simulation.

Analysis of Seismicity in Elbasani Geothermal Zone during Five Last Decades

During the last five decades since 1968, the Elbasani zone in Albania is dominated by low seismicity. This fault zone has evidenced some seismological phenomena. It is a transversal active fault zone with normal and strike-slip faults characterized by low-velocity layers. From instrumental seismicity in this area have been located 1831 seismic events, with magnitude ML &gt; 1.1 Richter and 3 of them with magnitude ML &gt; 5.0. Recently on May 19, 2014, a moderate earthquake ML5.2 occurred in the Elbasani seismogenic zone. This earthquake was located 6 km southeast of Belshi town and 18 km south of Elbasani town and was felt over Albania. The analysis of seismicity during the period of time 968-2022 years indicates that most earthquakes were located in the upper and middle earth crust and very few in the uppermost mantle. The focal mechanisms solution of some earthquakes indicates an extensional regime in this fault zone. The parameters of focal mechanisms indicate the predominance of normal fault motion and strike-slip fault motion is compatible with the present-day extension regime. The Elbasan zone has a complex geological structure with a significant number of geothermal water resources and some features of seismicity. The analysis of the features of seismicity during the five last decades provides us with correct interpretations of seismotectonic, low velocity lowers and understanding of geodynamic phenomena of the Earth's crust. The area of active faults of Elbasan presents a threat to the city of Elbasan and to the curative and tourist area of Llinxha-Hidrat.

Активность геоморфологических процессов на склонах речных долин в условиях газогидротермальных проявлений (по разновременным снимкам и ЦМР)

In the geothermal zones of modern volcanic areas, geomorphological processes are considerably influenced by numerous gas-hydrothermal outcrops, which may dramatically change rock properties and, consequently, denudation peculiarities and rates. The activity of processes on the slopes of Kamchatka river valleys under conditions of gas-hydrothermal occurrences (Geysernaya river valley) and without them (Shumnaya river valley) has been studied and comparatively analyzed. For the most correct separation and comparison of the valley regions which differ in the conditions of development of the modern slope processes, ArcticDEM digital elevation model and a series of morphometric maps (slope steepness, exposition, elementary watersheds) built on its basis, as well as geological maps, results of thermal survey of different detail level and field observation data were used. Interpretation of high spatial resolution images (0.5–5 m) for the mid-1960s (KeyHole-4 CORONA) and modern images for the period 2016–2021 from different survey systems was carried out. As a result of decoding, quantitative assessments of slope conditions within the selected valley fragments selected on the basis of morphometry were obtained for two time slices separated by 55 years. It is established that under conditions of gas-hydrothermal manifestations development, the share of the total area of the slope’s sections affected by active processes, with other conditions being equal, is significantly higher than the same in the areas without gas-hydrotherms. For 55 years the share of the areas with slope processes activation on the background areas practically has not changed, and on the territories affected by gas-hydrothermal influence has increased by 10–17 %. The conducted studies allow us to conclude that gas-hydrothermal manifestations are the most powerful driver of modern geomorphological processes on slopes in the studied region.

Deliverable Wellhead Temperature—A Feasibility Study of Converting Abandoned Oil/Gas Wells to Geothermal Energy Wells

Many oil/gas wells are abandoned or approaching their end-of-life. Converting them into geothermal wells can significantly improve the economics of oil/gas field operations and reduce carbon emissions. While such conversion has proven viable in some areas, this technology has not yet been considered in many other areas. It is highly desirable to investigate the feasibility of converting abandoned oil/gas wells into geothermal energy production wells in local geological conditions. A new mathematical model was developed in this study for analyzing the feasibility of converting oil/gas wells into geothermal wells. This model predicts the deliverable fluid temperature of a well by simulating the heat transfer from the geothermal zone through the wellbore to the surface wellhead, considering pipe and wellbore insulation. Factors affecting heat transfer efficiency were investigated with the model for a generic data set. Results indicate that without pipe insulation, the temperature of the returning fluid is very close to that of the injected fluid. The use of pipe insulation can significantly increase the temperature of the returning fluid. For a system with a thermal conductivity of insulation pipe Kp = 0.03 W/m-C, the deliverable fluid temperature can be increased from 30 °C to 124 °C. Adding an insulation cement sheath can efficiently further increase the temperature of the returning fluid. For a system with a cement thermal conductivity of 0.20 W/m-C, the deliverable fluid temperature can be further increased from 124 °C to 148 °C. Increasing the length of the horizontal wellbore in the geothermal zone from 2000 m to 8000 m can further increase the temperature of the returning fluid from 148 °C to 159 °C. Merely by increasing the vertical depth of the well from 7000 m to 7800 m, the deliverable fluid temperature can be enhanced from 148 °C to 161 °C. However, vertical depth is limited by the temperature-sensitivity of drilling technologies, such as the thermal stability of drilling fluids and downhole drilling instruments.

Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method

Natural gas production from marine gas hydrate reservoirs has become attractive to the oil and gas industry in recent years. It is still a great challenge to recover natural gas from hydrate reservoirs efficiently mainly due to sand production and wellbore collapse problems associated with the production scheme of depressurization. The thermal recovery method has not been proven economical due to the high cost of energy consumption. This study focuses on using geothermal energy to assist the depressurization process so that well pressure drawdown can be reduced and thus sand production and wellbore collapse problems can be mitigated. The authors investigated the transfer of heat energy from a natural geothermal zone to a marine gas hydrate reservoir and its effect on gas well productivity using analytical models. The result of our investigation shows that the initial well productivity can be significantly improved using geothermal energy more than 10-fold. This work provides engineers with an analytical tool for the feasibility analysis of using geothermal energy to improve well performance in gas hydrate reservoirs. Cited as: Mahmood, M. N., Guo, B. Gas production from marine gas hydrate reservoirs using geothermal-assisted depressurization method. Advances in Geo-Energy Research, 2023, 7(2): 90-98. https://doi.org/10.46690/ager.2023.02.03