Groundwater Convection Research Articles

Thermal performance enhancement of borehole heat exchanger by thermally induced groundwater convection in fractured rock

Thermal performance enhancement of Borehole Heat Exchanger (BHE) was a key to sustain the high effectiveness of this technology. Many measures have been taken to improve heat transfer efficiency of BHE in the past decades. However, all these changes leaded to slight thermal improvement due to restriction of heat conduction dominated heat transfer process in subsurface. To achieve an alternatively higher heat transfer mode of BHE, this study proposes a novel approach to induce groundwater thermal convection in fractured rock. A borehole was backfilled by gravels to sustain free groundwater flow in fracture network. A series of Thermal Response Tests (TRTs) show the fluid temperature of a gravel-filled BHE is 2.0–––2.4 °C lower than a sand-bentonite mixture grouted BHE, indicating the higher cooling efficiency. Two main factors including fracture dip angle and aperture, determine the flow behavior of a fracture network. The flow speed increases linearly with enlarging dip angle and shows a cubic polynomial relation with fracture aperture. Physical model tests show that the BHE induces groundwater convection flow by forming a circuit which couples with heat convection, mitigates the thermal stagnation around a borehole. As a result, thermal performance of a BHE was improved effectively.

Super-long gravity heat pipe geothermal space heating system: A practical case in Taiyuan, China

Using super-long gravity heat pipes (SLGHPs) to exploit deep-earth geothermal energy has indicated its technical superiority and viability; yet there is no practical application so far. The present work reports an SLGHP geothermal space heating system constructed in Taiyuan, China, which has two SLGHPs (2020 m and 2180 m long, respectively) in combination with a single heat pump. The two wells are located only ∼30 m apart, and the well-log temperature at 2000 m depth is around 63 °C for both. Temperatures measured by the optical fiber arranged along the SLGHP outer wall show remarkable uniformity, indicating the good performance of SLGHPs. Testing with the SLGHP system finds that the slightly longer SLGHP extracts 70 % more heat than the other one. Analyses reveal that the heat transfer in the geothermal formations surrounding the shorter SLGHP approximately follows the heat conduction regime while the convection of groundwater contributes less; the high yield of the slightly longer SLGHP is due to an interesting downhole heat transfer enhancement mechanism arising from the interlayer crossflow of groundwater. Further, a numerical model is developed to predict the SLGHP geothermal system's performance in 120-days’ operation. It is found that this system can output 1 MW of heat, sufficing space heating of ∼25,000 m2 buildings. The simulated 20-years’ operation indicates the thermal output degradation is 20.4 % for the shorter SLGHP, whereas it is only 6.8 % for the slightly longer SLGHP; the downhole groundwater crossflow lowers the SLGHP system degradation rate.

Forecast of 241Am Migration from a System of Deep Horizontal Boreholes

Highly radioactive materials classified as high-level nuclear waste (HLW) of atomic power engineering should be disposed of deeply underground in special geological disposal facilities (GDFs), which can be of either shaft or borehole type. The advantages of borehole-type GDFs result from smaller volumes of mining operations, a simpler construction technology, shorter construction time and cost. This allows us to consider them as an alternative to shaft-type GDFs. The parts of the boreholes in which waste containers should be placed can be both vertical and horizontal. Computer simulation of the migration of radionuclides from a group of parallel horizontal boreholes into the biosphere made it possible to conclude that horizontal GDF boreholes have significant advantages over vertical ones. We determined a forecast of 241Am migration by a method of mathematical modelling of 241Am release from vitrified HLW disposed of in several horizontal drillholes. The maximum concentrations of americium in the near-surface groundwater above the repository are calculated depending on the number of boreholes, the depth of their location and the distance between them, the permeability of rocks and the time of waste storage prior to disposal. Influence of different conditions on the safety of a GDF of borehole type is estimated. Calculations show that the heat generated by HLW causes a weaker groundwater convection near horizontal boreholes compared to vertical boreholes of the same capacity. In addition to that, at an equal thickness of the rock layer separating the HLW from the surface, the geothermal temperature of the host rocks in the near field of a horizontal borehole will be lower than the average geothermal temperature near a vertical borehole. As a result, the rate of radionuclides leaching from the waste forms by groundwaters will also be lower in the case of horizontal boreholes.

The Heat Source Origin of Geothermal Resources in Xiong’an New Area, North China, in View of the Influence of Igneous Rocks

The Xiong’an new area has abundant geothermal resources, and heat source research plays an important role in the geothermal system. Using the logging curve, we calculated the radioactive heat production of sedimentary layers and igneous rocks in non-sample wells; analyzed the influence of igneous rock distribution, residual heat, and its thermal increment on crust; and clarified the heat source origin of hydrothermal geothermal resources in Xiong’an new area. Sedimentary layers data (5,504) of 20 wells were converted to determine the applicable GR-A empirical relationship, and the radioactive heat production of igneous rocks with different lithologies was estimated. Finite element simulations show that igneous rock intrusions in the study area reach thermal equilibrium with the surrounding rock after 0.5 Ma at most. Upon cooling, the difference in thermal physical properties to the surrounding rock only leads to a higher heat flow of about 3.55 mW/m2 in the partial of the Niutuozhen salient. It is known that the development of igneous facies impacts the heat source. Under the geothermal background of “cold crust-hot mantle,” the mantel heat was the primary source, which the Yanshanian intrusions injected into the central salient, increasing the crustal heat by about 12% and the heat source by about 6%. The measured heat flow becomes higher in the salient (raised about 12.04 mW/m2–29.25 mW/m2) where the deep faults developed due to the groundwater convection. Heat conduction from crust-mantle heat flow and heat convection caused by deep faults are responsible for the current geothermal state in Xiong’an new area.

Numerical analysis of safety of a borehole repository for vitrified high-level nuclear waste

We developed a model and carried out transient 3-D computer simulation of radionuclides migration from an underground repository for vitrified high-level radioactive waste (HLW) with long-lived actinides. The repository represents an array of deep boreholes. Canisters with vitrified HLW are disposed one above another in lower parts of the boreholes. The upper parts of the boreholes are sealed. Radionuclides leached from the disposed waste are carried away by thermal convection of groundwater caused by heat generation in HLW. The computer simulation was carried out with use of a refined technique taking into account significant difference between radionuclides concentration in the groundwater in the loaded parts of the boreholes and at the earth surface, dependence of the groundwater properties on pT-parameters, composition of HLW. Values of leaching rate of the waste forms by groundwater depending on time and temperature, as well as role of colloid facilitated transport of radionuclides were determined from previous experiments with Na–Al–P-glass which was used in Russian Federation for HLW vitrification. The results of the calculations allowed us to conclude that distance between containers with HLW and the ground surface of 240 m and more is sufficient for safe disposal of the considered HLW.

Fracture Characteristics and Heat Accumulation of Jixianian Carbonate Reservoirs in the Rongcheng Geothermal Field, Xiong'an New Area

AbstractGeothermal energy plays an important role in urban construction of the Xiong'an New Area. Geothermal reservoir fracture distribution of the Mesoproterozoic Jixianian Wumishan Formation (Fm.) carbonate reservoir in the Rongcheng geothermal field are evaluated based on FMI log from Wells D19 and D21. The results show carbonate reservoir fracture density of Well D19 is 15.2/100 m, greater than that of Well D21 with a value of 9.2/100 m. Reservoir porosity and permeability of Well D19 are better than that of Well D21, and the water saturation is bimodally distributed. The movable fluid volume ratio (BVM) of Well D19 is 2% to 8% with some zones exceeding 20%, while the value of Well D21 is less than 4%. Therefore, reservoir fractures in Well D19 are more conducive to fluid flow. Reservoir fractures have a similar occurrence to normal faults, indicating that the tensile stress field controlled the formation of such fractures. Developed reservoir fractures provide a good channel for groundwater convection. The circulation of regional groundwater and the heat exchange between water and rock and the multiple heat accumulation patterns form a stable and high potential heat reservoir in the Rongcheng geothermal field.

Heat Flow Correction for the High-Permeability Formation: A Case Study for Xiong’an New Area

Abstract The Xiong’an New Area is located at the western Bohai Bay Basin, 150 km south of Beijing, China. The area has tremendous high heat flow value within the sedimentary layer, and the average value can reach 90 mW·m-2 within the Niutuozhen Uplift. However, combining the basal heat flow at the top of the metamorphic layer with the heat flow value which was contributed by the radiogenic heat production from the overlying formation, the surface heat flow value was only 65.1 mW·m-2 in this area. Thus, the heat flow value within the sedimentary layer was greatly influenced by other factors. In this study, based on the continuous temperature measurements data from 4 boreholes, thermos-physical parameters (conductivity, radioactive heat production, density, and heat capacity) from 90 rock sample measurements, and the regional stratigraphic development, a two-dimensional thermal-hydraulic modelling was carried out to study the influence of the heat refraction and groundwater convection on the heat flow value. According to calculation results, the heat flow disturbance caused by heat refraction was 10 mW·m-2, and the disturbance value was 20 mW·m-2 for the groundwater convection. Furthermore, when the high-permeability layer thickness was a certain value, with the increasing high-permeability layer buried depth, the influence of the groundwater convection on the temperature field which was used for the heat flow calculation became weak. While when the high-permeability layer buried depth was set up, the influence of the groundwater convection on the above temperature field became stronger with the increasing high-permeability layer thickness.

Hydrogeological research in the Tuyajto Lake at the Flamingo National Reserve (Atacama, Chile)

The Tuyajto Lake is a saline lake located in the Andean Altiplano of northern Chile, at the foot of the volcano of the same name. It is fed by springs located on its eastern and northern boundaries. These springs discharge groundwater from a volcanic aquifer. Arid conditions dominate in the area, with an average precipitation of less than 200 mm/year. The tritium content in some groundwater samples shows the contribution of modern recharge to the total groundwater flow. Recharge occurs by infiltration of snowmelt in the austral winter months and to a lesser extent by short but intense precipitation events during the summer. According to the vertical gradients of precipitation and its rainfall isotopic content (δ18O, δ2H), the recharge zone of the springs is located at the northern area of the lake, above 4,900 m a.s.l., along the slopes of the Tuyajto volcano, whereas the recharge to the springs discharging on the eastern area of the lake originates in the adjacent basins of Pampa Colorada and Pampa Las Tecas, at altitudes of between 4,400 and 4,700 m a.s.l. The water of these springs may contain measurable tritium. The chemical composition of groundwater is the result of meteoric water evaporation processes, high temperature water-rock interaction and the dissolution of buried old salt flat deposits. The groundwater flow is shallow, due to the presence of a regional low permeability ignimbrite formation, which precludes the formation of deep convective groundwater flow cells due to the high density. At the local scale, the Laguna Tuyajto behaves as a flow-through system compared to the regional groundwater flow. The persistence of the springs is essential for the existence of the brine sheet and maintaining the ecological conditions for the waterfowl.

Elastic and Thermoelastic Effects on Thermal Water Convection in Fracture Zones

AbstractNatural groundwater convection in fractures is an important mechanism of mass and heat transfer in the subsurface, locally altering temperature by several tens of degrees. The thermoelastic stresses resulting from these thermal anomalies induce thermal strains, which in turn alter the transmissivity (permeability times thickness) of the fracture and, therefore, the convective flow within. We investigate the effect of thermal strains on fracture convection patterns using a three‐dimensional thermo‐hydraulic‐mechanical numerical model, implementing the Barton‐Bandis relationship between fracture transmissivity and effective normal stress, which results in a downward‐narrowing of the fractures. When thermoelasticity is not taken into account, convection forms narrow upflow zones and wide downflow zones. Decreasing fracture stiffness results in similar upflow/downflow patterns, but restricted to the shallow portions of the fracture, creating relatively minor thermal changes. When thermo‐elasticity is included in the model, thermal strains induced by cool downflow zones create narrow high‐transmissivity channels within the fracture, allowing convective flow to reach greater depths and significantly reducing the geothermal gradient near the fracture. Fracture stiffness is a key parameter in determining convection depth and thermal perturbation strength for a given set of host rock mechanical properties. When fracture stiffness is below some threshold, subsequent contractive thermoelastic strains were found to induce tensile failure of the host rock below the fracture, propagating and deepening the fracture into the host rock. This observation provides support to the previously proposed concept of convective downward migration.

Petrographic and mineralogical study of hydrothermal alteration of the Rokko Granite at Hakusui‐kyo and Horai‐kyo along the Arima‐Takatsuki Tectonic Line in western Japan

AbstractField, hand specimen, and microscopic investigations alongside X‐ray diffraction analyses revealed four types of hydrothermal alteration (Type‐A, ‐B, ‐C, and ‐D) based on the mode of occurrence of altered rocks and alteration mineral assemblage at Hakusui‐kyo and Horai‐kyo along the Arima‐Takatsuki Tectonic Line (ATTL) in western Japan. Type‐A alteration locally occurred as gray alteration halos with sulfide minerals. Type‐B and ‐C alterations were confined to fault gouge veins and occurred as greenish‐gray veins and brown veins, respectively. Type‐C alteration crosscut Type‐B alteration. These alterations were associated with a number of granitic fragments including cohesive breccia and micrographic facies. Type‐D alteration occurred locally in brown sediments. Different mineralogical features in the four alterations are summarized as (Type‐A) illite; (Type‐B) chlorite; (Type‐C) limonite (Fe3+ hydroxides and goethite) and calcite; and (Type‐D) limonite. We propose that the alterations can be broadly divided into Paleocene hydrothermal alteration (Type‐A) and post‐Late Miocene hydrothermal alteration (Type‐B, ‐C, and ‐D): Type‐A alteration occurred at approximately 200 °C during hydrothermal activity after a granitic intrusion in Late Cretaceous; Type‐B, ‐C and ‐D alterations occurred under hydrothermal activity accompanying deep fluids with repeated ascents invoked by the seismicity of the ATTL after the Late Miocene. The fluids may have been the “Arima‐type thermal waters” (i.e., mixtures of convective groundwater and Na‐Ca‐Cl‐HCO3‐type fluids). Type‐B alteration occurred in fractures at depths where the temperature was ≥150 °C. Type‐C alteration overprinted Type‐B alteration as a result of mixing of new deep fluids and descending oxidized meteoric water near the surface. Fe3+ hydroxides and calcite precipitated from the fluids due to the oxidation of Fe2+ and the degassing of CO2, respectively, at ambient to near‐boiling temperatures. When the ascending fluids gushed out from the fractures, they generated Type‐D alteration at the surface under similar temperature conditions due to the oxidation of Fe2+.

Comparative Analysis of Geothermal Energy in Korea Based on Closed Borehole and Single- and Two-Well Standing Column Well Geothermal Heat Exchange Systems

In this study, a mobile measuring device was developed and a thermal response test that applied a standing column well-type heat exchanger was conducted to obtain design parameters from field measurements. The main purpose of this study was to investigate the effects of thermal conductivity and geothermal resistance on site, including the flow and effects of natural convection of groundwater in boreholes. We compared, analyzed, and investigated the effective thermal conductivity of a borehole heat exchanger system and the effective thermal conductivity that was not applied when bleeding single-well standing column wells (SCWs), which is called an open-type standing column well geothermal heat exchanger system. We also investigated the heat transfer characteristics during the bleeding of two-well type SCWs, where water is injected from one clearing hole to the returning hole depending on the bleeding rate. Artificial recharging was used to inject the change of thermal conductivity from the bleeding rate of a geothermal heat exchanger into another SCW type. From the comparison results of the thermal conductivity of the multi-well and single-well underground heat exchangers, four times higher efficiency than the single-well was obtained. The reason for this is considered to be energy utilization utilizing groundwater energy.

Terrestrial heat flow in the baiyinchagan sag, erlian Basin, northern China

The Baiyinchagan Sag of the Erlian Basin is a Mesozoic continental rift basin located in the eastern part of the Central Asian Orogenic Belt between the North China Craton and the Siberian Craton. The sedimentary fill comprises mainly the Cretaceous sandstones and mudstones underlying Cenozoic succession. Knowledge regarding the factors affecting the tectonic evolution of the Baiyinchagan Sag is lacking. The objective of this study is to obtain new terrestrial heat flow measurements in the Baiyinchagan Sag for constraints on its thermotectonic history. We obtained continuous temperature logs from three boreholes, namely Xi24, Xi3-76 and Xi30 with depths of 1230, 1660 and 2160 m, respectively. Additionally, we gauged the thermal conductivity of the lithologic samples of the main sedimentary rocks. Our analysis indicates that subsurface temperatures are affected by the convection of groundwater and subsurface warming. After removing the influence of groundwater and climatic effects, the subsurface temperature gradients of the Cretaceous Duhongmu and Tenggeer Formations range from 40.4 to 42.1 ℃ km−1. We performed water saturation correction for the measured thermal conductivity data. The thermal conductivities of the Saihantala, the Duhongmu, the Tenggeer, and the Aershan Formations were found to be 1.15, 2.13, 1.99, and 2.15 W m-1 K−1, respectively. Vertical Peclet number analysis of the temperature-depth profile of Xi3-76 borehole with a Peclet number of 0.16 indicates that the conductive heat transfer dominates in the component of the vertical heat transfer. The three new heat flow values range from 80.8 to 89.7 mW m-2, with a mean of 84.9 ± 3.4 mW m-2, significantly higher than the global and regional average whereas consistent with its deep thermotectonic regime.

Decompression boiling and natural steam cap formation in high-enthalpy geothermal systems

Many high-enthalpy geothermal systems exhibit vapor-rich boiling zones at shallow depths (<1 km), commonly known as steam caps. While the spatial extent and vapor content of steam caps often increases in response to fluid extraction and subsequent pressure decline, the geologic factors controlling steam cap formation and development are poorly understood. Numerical simulations of groundwater convection driven by a transiently cooling intrusion elucidate a natural mechanism by which steam caps can develop from initially liquid-dominated boiling zones. In the simulations, intensive decompression boiling and steam cap development occurs after the heat of a subsurface magmatic intrusion is exhausted by prolonged hydrothermal convection. A reduction in the strength of the upflow leads to a fluid pressure decrease of 2–4 MPa in boiling zones beneath an impermeable cap rock. As the vertical pressure gradient decreases, approaching vapor-static, zones of liquid-vapor counterflow (i.e., heat pipes) develop at the base of steam caps, efficiently isolating overlying vapor-rich zones from underlying liquid. The reservoir rock permeability and the cap rock thickness are main controls on the enthalpy and spatial extent of steam caps, with thicker and higher enthalpy (potentially superheated) steam caps developing in intermediate permeability reservoir rocks (∼ 10−15 m2). Due to the importance of transient changes in geothermal system structure to steam cap development, the dynamics of natural steam cap formation may not be captured in standard approaches to natural state reservoir modeling, which express the role of the heat source in terms of fixed boundary conditions.

Hydrogeological research in the Tuyajto Lake at the Flamingo National Reserve (Atacama, Chile)

The Tuyajto Lake is a saline lake located in the Andean Altiplano of northern Chile, at the foot of the volcano of the same name. It is fed by springs located on its eastern and northern boundaries. These springs discharge groundwater from a volcanic aquifer. Arid conditions dominate in the area, with average precipitation less than 200 mm/year. The tritium content in some groundwater samples shows the contribution of modern recharge to the total groundwater flow. Recharge occurs by infiltration of snowmelt in the austral winter months and to a lesser extent by short but intense precipitation events during the summer. The vertical gradients of rainfall isotopic content (δ18O, δ2H) and precipitation points to the recharge zone of the springs being located at the northern area of the lake, above 4,900 m a.s.l. along the slopes of the Tuyajto volcano, whereas recharge to the springs discharging on the eastern area of the lake originates in the adjacent basins of Pampa Colorada and Pampa Las Tecas at altitudes between 4,400 and 4,700 m a.s.l. The water of these springs may contain measurable tritium. The chemical composition of groundwater is the result of meteoric water evaporation processes, high temperature water-rock interaction and dissolution of buried old salt flat deposits. The groundwater flow is shallow, due to the presence of a regional low permeability ignimbrite formation that precludes the formation of deep convective groundwater flow cells due to the high density of brines. At a local scale, the Tuyajto lake behaves as a flow-through system with respect to the regional groundwater flow. The persistence of the springs is essential for the existence of the brine sheet and maintaining the ecological conditions for the waterfowl.

The influence of groundwater seepage on the performance of ground source heat pump system with energy pile

Both initial cost and land area can be saved while ground source heat pump (GSHP) system employs energy pile as the ground heat exchanger (GHE), and the energy pile exchanges heat with the surrounding underground medium. Groundwater seepage exerts influence on the heat transfer, and this is because the convection of groundwater alleviates the heat or cold accumulation around pile and then improves the heat transfer effect of energy pile. The existing researches regards the velocity of groundwater seepage as the one-dimensional vector, or the available models are not accurate enough though three-dimensional groundwater seepage is considered. The paper describes the spiral line heat source models with three-dimensional groundwater velocity, and the analytical solutions of temperature response are obtained. Afterwards, the performance of GSHP system is studied based on the proposed models, and the factors that have impacts on the coefficient of performance (COP) of heat pump unit are explored. The differences are explained while every factor employs different cases, but the common results of all cases are that the COP is indeed improved by groundwater seepage, and therefore the advantages of groundwater seepage should be noted. The researches of the paper attach importance to the seepage role, and the findings of the paper are favorable for the further development of GSHP technology.

Study on the effect of groundwater flow on the identification of thermal properties of soils

Thermal properties are very important for the design of ground heat exchangers (GHE). The line source model is typically used to identify these parameters, based on the inlet and outlet water temperature of an in-situ thermal response test (TRT). Since the model is based on thermal conduction, convection of groundwater can affect identification results. In this paper, a three-dimensional numerical simulation model was established to simulate the dynamic heat exchange for GHEs. A series of TRTs were conducted to analyse the effect of groundwater seepage on identification of thermal properties of soils. The equivalent thermal conductivity (ETC) was found to be increased gradually, while the equivalent volume heat capacity (EVHC) and the change rates of both parameters decreased with increases in groundwater velocity. The seepage direction was vital for identification, especially when the velocity was fast. The ETC was larger and the EVHC was smaller when the seepage direction was perpendicular as opposed to parallel to the buried pipe plane. The height of the seepage layer significantly affected identification results, and the greater the seepage velocity was, the more significant the effect was. In addition, the higher height led to the larger ETC and the smaller EVHC. The location of the seepage layer had little influence on results, but the ETC was larger and the EVHC was smaller if the location was closer to the ground surface.

Analysis and interpretation of earthquake-related groundwater response and ground deformation: a case study of May 2006 seismic sequence in the Mexicali Valley, Baja California, Mexico

Anomalous groundwater level and temperature changes are compared with ground deformation recorded before and after an earthquake of MW 5.4 and its foreshocks and aftershocks that occurred during 22–28 May 2006 in the Mexicali Valley, Baja California, Mexico. The coseismic groundwater level changes could be attributed to static volumetric strain changes caused by the mainshock, except for one well, where the groundwater level change may have been affected also by a triggered slip event at a nearby fault. Some of the coseismic temperature changes were attributed to increased convection and mixing of groundwater by seismic shaking. Modeling of groundwater level records allowed the estimation of hydraulic diffusivity. The observed ground tilt and groundwater level anomalies in the area close to the source fault before and after the mainshock and before the aftershocks occurrence are explainable by the dilatancy–diffusion theory, or possibly by assuming the occurrence of a slow slip events and/or fault permeability changes.

Comparison of radon concentrations in soil gas and indoor environment of Afyonkarahisar Province

It is well known that radon is the main source of natural radiation exposure to the population. Indoor radon concentrations in an area are affected by ascending radon migration following the convection of groundwater and soil gas along fractures and faults in the bedrock sediments. There are various studies showing that positive radon anomalies in the soil gas are found to coincide with the locations of houses showing the highest concentrations. Moreover, soil gas radon levels and soil permeability are important factors in determining the radon potential of an area, because high permeability enables the increased migration of radon from the soil into houses. Since radon in homes originates mainly from soil gas radon, it is of public interest to study the correlation between soil gas radon and indoor radon in different geographic locations. In the present work, a correlation study was carried in conjunction with radon concentrations in soil gas and indoor environment of Afyonkarahisar Province. The provincial center was assumed to be divided into four regions according to the rock types and tectonic structure to show also the geological structure effect on radon concentrations. The indoor radon concentrations were measured in 74 dwellings using CR-39 passive nuclear track detectors, and the radon concentrations in soil gas were determined in 243 drilled holes using AlphaGUARD detector. The correlation coefficient of 0.97 was obtained between radon concentrations in soil gas and indoor environment of Afyonkarahisar Province.

Solute transfer during consolidation based on a solid‐fluid‐solute coupling model

SummaryThe migration of contaminant through soil is usually modeled using the advection‐dispersion equation and assumes that the porous media is stationary without introducing a constitutive equation to represent soil structure. Consequently, time‐dependent deformation induced by soil consolidation or physical remediation is not considered, despite the need to consider these variables during planning for the remediation of contaminated ground, the prediction of contaminated groundwater movement, and the design of engineered landfills. This study focuses on the numerical modeling of solute transfer during consolidation as a first step to resolve some of these issues. We combine a coupling theory‐based mass conservation law for soil‐fluid‐solute phases with finite element modeling to simulate solute transfer during deformation and groundwater convection. We also assessed the sensitivity of solute transfer to the initial boundary conditions. The modeling shows the migration of solute toward the ground surface as a result of ground settlement and the dissipation of excess pore water pressure. The form of solute transport is dependent on the ground conditions, including factors such as the loading schedule, contamination depth, and water content. The results indicate that an understanding of the interaction between coupling phases is essential in predicting solute transfer in ground deformation and could provide an appropriate approach to ground management for soil remediation.

Evaluation of Geothermal Potential in the Vicinity of the Flooded Sierra Almagrera Mines (Almeria, SE Spain)

We evaluated the hydrogeochemical characteristics of water from the old flooded Sierra Almagrera mines to determine the possible origin of its geothermal fluids, to establish a geological–geochemical model of the geothermal system, and evaluate the site’s geothermal potential. The mine water contained high concentrations of chloride (59.6 g/L), Na (28 g/L), K (1.75 g/L), Ca (7.2 g/L), Mg (0.63 g/L), and Li (66 mg/L), especially in water from the old dewatering system. Metal concentrations were especially elevated in the old mine shafts, with high amounts of Fe (1990 mg/L), Mn (600 mg/L), Zn (460 mg/L), Pb (4 mg/L), and Ni (11.4 mg/L). The Cl/Br molar ratios of the water was high, which may indicate the possible leaching of natural halite from the evaporite deposits in the aquifer recharge area. The mine water had the most elevated temperatures and are, possibly, representative of the extent of equilibration in most of the reservoir. The estimated mean temperatures in the geothermal reservoir, based on the triangular (Giggenbach) Na–K–Mg diagram, was 190 °C for equilibrated waters, which may justify the development of this geothermal resource. The geothermal characteristics imply convection of groundwater to 2500–3000 m below sea level, in agreement with the hydrodynamic model proposed.