Numerical Simulation for Hot Dry Rock Geothermal Well Temperature Field

Study on temperature distribution simulation during cementing of hot dry rock (HDR) geothermal well is rare. It has important guiding significance to simulate the construction process of temperature distribution of hot dry rock on site construction. Based on numerical simulation of HDR considering heat-fluid-solid coupling, the influence of temperature distribution on well cementing is analyzed when the drilling fluid cycles and reaches stable state, respectively, and when the cement slurry is injected during the cementing process. It is found that the seepage at the well bottom accelerates the flow velocity of wellbore;the stable temperature change is less than the cyclic temperature change;and the upper and lower temperature variation of the stratum is greater when the cement slurry is injected. Therefore, as to cement retarder involved, the influence of temperature variation on concretion should be considered during cementing of the hot dry rock geothermal well.

Numerical analyses of coupled thermo-mechanical behaviors of cement sheath in geothermal wells

The stability of cement sheath under high temperature and high pressure is one of the most critical issues for the durability of geother-mal well systems.In this study,a two-dimensional plane-strain finite element code was developed to investigate the coupled thermo-mechanical behaviors of the casing-cement-formation system.Different from previous linear elastic analyses,a thermoelasto-plastic con-stitutive model based on the thermodynamic theory was adopted for the cement sheath.It is shown that the finite element simulations using the proposed model provide a more accurate and realistic prediction of stress–strain responses of the cement sheath under high temperature.The results demonstrate that the radial stress concentration and the tensile strain concentration occur at both the cement–casing interface and the cement–formation interface,where the cement sheath is most likely to fail.High strength and low stiff-ness in the cement sheath and the formation are preferred for the integrity of the system.Both large thermal cycles and large differences between the internal fluid pressure and the external pressure should be avoided during operation.The new code is an alternative tool for guiding the geothermal well design.The finite element framework described herein is universal for other thermo-mechanical applications,such as energy foundations and energy tunnels.

Simulation of thermal breakthrough factors affecting carbonate geothermalto-well systems

Fractures play a pivotal role in carbonate thermal storage systems,serving as primary hydraulic conductivity channels that significantly influence thermal breakthrough times and heat extraction efficiency in geothermal-to-well systems.Their impact is critical for well placement and system life prediction.This paper focuses on a geothermal-to-well system within the carbonate reservoir of the Wumishan formation in the Rongcheng geothermal field,Xiong'an new area.It employs a combination of field tests and numerical simulations to determine the permeability of the reservoir and the evolution of fractures between wells.It also examines the influence of fracture width and roughness coefficient on the seepage and temperature fields under various injection scenarios and predicts thermal breakthrough times for production wells.The results show:Higher permeability is observed near well D16 compared to well D22 within the studied geothermal-to-well systems.Wider fractures between wells result in faster temperature decline in production wells.Lower injection flow rates lead to slower temperature reduction in injection wells.The use of roughness coefficients minimizes temperature variations in production wells.This study not only offers guidance for the development and utilization of the geothermal well system,but also contributes to a deeper understanding of the groundwater seepage and heat transfer process influenced by fractures.

Geochemical and Isotopic Techniques Constraints on the Origin,Evolution,and Residence Time of Low-enthalpy Geothermal Water in Western Wugongshan,SE China

Geothermal resources are increasingly gaining attention as a competitive,clean energy source to address the energy crisis and mitigate climate change.The Wugongshan area,situated in the southeast coast geothermal belt of China,is a typical geothermal anomaly and contains abundant medium-and low-temperature geothermal resources.This study employed hydrogeochemical and isotopic techniques to explore the cyclic evolution of geothermal water in the western Wugongshan region,encompassing the recharge origin,water-rock interaction mechanisms,and residence time.The results show that the geothermal water in the western region of Wugongshan is weakly alkaline,with low enthalpy and mineralization levels.The hydrochemistry of geothermal waters is dominated by Na-HCO_(3)and Na-SO_(4),while the hydrochemistry types of cold springs are all Na-HCO_(3).The hydrochemistry types of surface waters and rain waters are NaHCO_(3)or Ca-HCO_(3).The δD and δ^(18)O values reveal that the geothermal waters are recharged by atmospheric precipitation at an altitude between 550.0 and 1218.6 m.Molar ratios of maj or solutes and isotopic compositions of^(87)Sr/^(86)Sr underscore the significant role of silicate weathering,dissolution,and cation exchange in controlling geothermal water chemistry.Additionally,geothermal waters experienced varying degrees of mixing with cold water during their ascent.Theδ^(13)C values suggest that the primary sources of carbon in the geothermal waters were biogenic and organic.Theδ^(34)S value suggests that the sulfates in geothermal water originate from sulfide minerals in the surrounding rock.Age dating using 3H and^(14)C isotopes suggests that geothermal waters have a residence time exceeding 1 kaBP and undergo a long-distance cycling process.

Effects of fracture evolution and non-Darcy flow on the thermal performance of enhanced geothermal system in 3D complex fractured rock

In fractured geothermal reservoirs,the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance.In this study,we proposed a non-Darcy rough discrete fracture network(NR-DFN)model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical(THM)coupling processes for heat extraction in geothermal reservoir.We further employed the model on the Habanero enhanced geothermal systems(EGS)project located in Australia.First,our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations,as well as uneven spatial distribution of shear failure in 3D fracture networks.Activated shear failure is mainly concentrated in the first fracture cluster.Secondly,channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses.Moreover,the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature.The NR-DFN model framework and the Habanero EGS's results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.

A combined method using Lattice Boltzmann Method(LBM)and Finite Volume Method(FVM)to simulate geothermal reservoirs in Enhanced Geothermal System(EGS)

With the development of industrial activities,global warming has accelerated due to excessive emission of CO_(2).Enhanced Geothermal System(EGS)utilizes deep geothermal heat for power generation.Although porous medium theory is commonly employed to model geothermal reservoirs in EGS,Hot Dry Rock(HDR)presents a challenge as it consists of impermeable granite with zero porosity,potentially distorting the physical interpretation.To address this,the Lattice Boltzmann Method(LBM)is employed to simulate CO_(2)flow within geothermal reservoirs and the Finite Volume Method(FVM)to solve the energy conservation equation for temperature distribution.This combined method of LBM and FVM is imple-mented using MATLAB.The results showed that the Reynolds numbers(Re)of 3,000 and 8,000 lead to higher heat extraction rates from geothermal reservoirs.However,higher Re values may accelerate thermal breakthrough,posing challenges to EGS operation.Meanwhile,non-equilibrium of density in fractures becomes more pronounced during the system's life cycle,with non-Darcy's law becoming significant at Re values of 3,000 and 8,000.Density stratification due to buoyancy effects significantly impacts temperature distribution within geothermal reservoirs,with buoyancy effects at Re=100 under gravitational influence being noteworthy.Larger Re values(3,000 and 8,000)induce stronger forced convection,leading to more uniform density distribution.The addition of proppant negatively affects heat transfer performance in geothermal reservoirs,especially in single fractures.Practical engineering considerations should determine the quantity of proppant through detailed numerical simulations.

Conventional Geothermal Systems and Unconventional Geothermal Developments: An Overview

This paper provides an overview of conventional geothermal systems and unconventional geothermal developments as a common reference is needed for discussions between energy professionals. Conventional geothermal systems have the heat, permeability and fluid, requiring only drilling down to °C, normal heat flow or decaying radiogenic granite as heat sources, and used in district heating. Medium-temperature (MT) 100°C - 190°C, and high-temperature (HT) 190°C - 374°C resources are mostly at plate boundaries, with volcanic intrusive heat source, used mostly for electricity generation. Single well capacities are °C - 500°C) and a range of depths (1 m to 20 Km), but lack permeability or fluid, thus requiring stimulations for heat extraction by conduction. HVAC is 1 - 2 m deep and shallow geothermal down to 500 m in wells, both capturing °C, with °C are either advanced by geothermal developers at <7 Km depth (Enhanced Geothermal Systems (EGS), drilling below brittle-ductile transition zones and under geothermal fields), or by the Oil & Gas industry (Advanced Geothermal Systems, heat recovery from hydrocarbon wells or reservoirs, Superhot Rock Geothermal, and millimeter-wave drilling down to 20 Km). Their primary aim is electricity generation, relying on closed-loops, but EGS uses fractures for heat exchange with earthquake risks during fracking. Unconventional approaches could be everywhere, with shallow geothermal already functional. The deeper and hotter unconventional alternatives are still experimental, overcoming costs and technological challenges to become fully commercial. Meanwhile, the conventional geothermal resources remain the most proven opportunities for investments and development.

Structural Controls Analysis and Its Correlation with Geothermal Occurrence at Barrier Volcanic Complex (BVC), Turkana, Kenya

Geothermal is a clean energy source that is freely available in the subsurface. The exploitation of this vital resource needs intensive exploration in order to identify and quantify its occurrence. The three parameters considered when assessing the viability of a geothermal system include;heat source, fractures and fluids. Geological structures are important in transportation of fluids to and from the heat source aiding in recharge of the geothermal system and enhancing productivity. Remote sensing method was applied in mapping the structures at Barrier Volcanic Complex (BVC) by using hill shading technique which utilized four illumination angles of the sun (azimuth) i.e. 45°, 90°, 150°, and 315°, constant elevation of 45° and exaggeration of 10. The data used was Shuttle Radar Topographic Mission (SRTM) Satellite Imagery. ArcGIS Software was used for lineaments delineation and density mapping, PCI Geomatica was used to generate major faults, while Georose and Rockworks 17 were used to generate the rose diagrams. Geological structural analysis was done by delineating lineaments, determining the density distribution of lineaments and finally determining the structural trends of lineaments. The generated major faults in the area and the location of the occurrence of surface manifestations were compared with the generated lineaments. A total of 260 lineaments were generated whereby at 45° there was a total of 60 lineaments, at 90° 95 lineaments, at 150° 61 lineaments, and at 315° 44 lineaments. The results of structural analysis in the area as shown by the rose diagrams indicate an NNE-SSW and N-S trending of structures. In conclusion, the study area is highly fractured as indicated by the presence of numerous lineaments. These lineaments provide good recharge to the geothermal system and enhance the geothermal reservoir in the area.

Exploring Heat Sources Using Gravimetric Data: A Case Study of Magadi Geothermal Prospect, Kenya

Understanding the location of the subsurface heat sources is crucial for efficient geothermal resource exploration and exploitation. This study aimed to investigate the faults and the depth to heat sources for a geothermal system in Magadi, southern Rift Valley, through the integration of gravity mapping, 3D Euler deconvolution, and spectral analysis. Gravity mapping is a powerful geophysical method widely used to infer subsurface density variations, which are indicative of geological structures and volcanic intrusions that can be potential heat sources. The Volcano-Tectonic and Fluvial-Deltaic Sedimentation process of the Kenyan rift which encompasses the Magadi basin are responsible for geomorphic and geologic processes in the area. Alkali lava sheets of Magadi plateau trachytes covered with lacustrine sediments characterize 80% of the area. Deeper is the Tanzanian craton basement, overlain by Pliocene to Miocene volcanic and sedimentary rocks. A gravity survey with a data density of 2.375 stations/km2 produced high-resolution anomaly and total horizontal derivative maps showing gravity highs between −180 mGals to −174 mGals along the eastern zone of the study area. A buried major fault trending N-S was delineated in the mid-upper region of the area by Euler solutions at an average depth of 350 meters. Deeper features associated with possible volcanic dykes and sills gave Euler depth ranges of 0.7 km to 2.2 km. Radial average spectral analysis showed depth to the top of shallow and deep features at 2.4694 km and 5.827 km respectively. The correlation between gravity anomalies, geological structures, and present hot springs supports the hypothesis that volcanic processes have played a significant role in the development of the geothermal system in the study area.

Numerical simulation of operation performance on production and injection of a double well geothermal system in Kailu Basin, Inner Mongolia

Inner Mongolia is abundant in geothermal resources,but the development and utilization of medium-depth geothermal resources for clean heating in winter is still in the preliminary stage compared with the neighboring provinces.In this paper,a recently developed geothermal heating system using the Mesozoic sandstone reservoirs in Baokang of Kailu Basin,Eastern Inner Mongolia was investigated,a threedimensional geological model of a pair of production and injection well was established,and numerical simulations on the long term operation performance were conducted and verified by pumping test and water level recovery test data.The effects of flow rates,the direction of wells,injection temperature and ratios on the flow field and water level in the thermal reservoir were analyzed.The results show that considering a 30-year operation period and a production rate from 90 m^(3)/h to 110 m^(3)/h,the optimum well spacing can be increased from 225 m to 245 m,with an average value of 235 m.With the decrease of the injection temperature,the cold front of the injection water has an increasing influence on the temperature in the production well.A complete injection or the principle of production according to injection is recommended in order to maintain the long-term operation stability.In addition,the location of the injection well should be arranged in the downstream of the natural flow field.The present results can provide a useful guide for the optimum design and performance prediction of geothermal wells,thus maintaining the production and injection balance and promoting the sustainable development and utilization of medium-depth and deep geothermal resources.

Clogging mechanism in the process of reinjection of used geothermal water: A simulation research on Xianyang No.2 reinjection well in a super-deep and porous geothermal reservoir

In the process of geothermal exploitation and utilization, the reinjection amount of used geothermal water in super-deep and porous reservoir is small and significantly decreases over time. This has been a worldwide problem, which greatly restricts the exploitation and utilization of geothermal resources. Based on a large amount of experiments and researches, the reinjection research on the tail water of Xianyang No.2 well, which is carried out by combining the application of hydrogeochemical simulation, clogging mechanism research and the reinjection experiment, has achieved breakthrough results. The clogging mechanism and indoor simulation experiment results show: Factors affecting the tail water reinjection of Xianyang No.2 well mainly include chemical clogging, suspended solids clogging, gas clogging, microbial clogging and composite clogging, yet the effect of particle migration on clogging has not been found; in the process of reinjection, chemical clogging was mainly caused by carbonates(mainly calcite), silicates(mainly chalcedony), and a small amount of iron minerals, and the clogging aggravated when the temperature rose; suspended solids clogging also aggravated when the temperature rose, which showed that particles formed by chemical reaction had a certain proportion in suspended solids.

An Integrated Framework for Geothermal Energy Storage with CO_(2)Sequestration and Utilization

Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage due to its superior thermal properties.Moreover,the use of CO_(2)plumes for geothermal energy storage mitigates the greenhouse effect by storing CO_(2)in geological bodies.In this work,an integrated framework is proposed for synergistic geothermal energy storage and CO_(2)sequestration and utilization.Within this framework,CO_(2)is first injected into geothermal layers for energy accumulation.The resultant high-energy CO_(2)is then introduced into a target oil reservoir for CO_(2)utilization and geothermal energy storage.As a result,CO_(2)is sequestrated in the geological oil reservoir body.The results show that,as high-energy CO_(2)is injected,the average temperature of the whole target reservoir is greatly increased.With the assistance of geothermal energy,the geological utilization efficiency of CO_(2)is higher,resulting in a 10.1%increase in oil displacement efficiency.According to a storage-potential assessment of the simulated CO_(2)site,110 years after the CO_(2)injection,the utilization efficiency of the geological body will be as high as 91.2%,and the final injection quantity of the CO_(2)in the site will be as high as 9.529×10^(8)t.After 1000 years sequestration,the supercritical phase dominates in CO_(2)sequestration,followed by the liquid phase and then the mineralized phase.In addition,CO_(2)sequestration accounting for dissolution trapping increases significantly due to the presence of residual oil.More importantly,CO_(2)exhibits excellent performance in storing geothermal energy on a large scale;for example,the total energy stored in the studied geological body can provide the yearly energy supply for over 3.5×10^(7) normal households.Application of this integrated approach holds great significance for large-scale geothermal energy storage and the achievement of carbon neutrality.

Simulation study of supercritical carbon dioxide jet fracturing for carbonate geothermal reservoir based on fluid-thermo-mechanical coupling model

Geothermal energy is a kind of renewable,sustainable and clean energy resource.Geothermal energy is abundant in carbonate reservoirs.However,low matrix permeability limits its exploitation.The super-critical carbon dioxide(SC-CO_(2))jet fracturing is expected to efficiently stimulate the carbonate geothermal reservoirs and achieve the storage of CO_(2) simultaneously.In this paper,we established a transient seepage and fluid-thermo-mechanical coupled model to analyze the impact performance of sc-CO_(2) jet fracturing.The mesh-based parallel code coupling interface was employed to couple the fluid and solid domains by exchanging the data through the mesh interface.The physical properties change of sC-CO_(2) with temperature were considered in the numerical model.Results showed that SC-CO_(2) jet frac-turing is superior to water-jet fracturing with respect to jetting velocity,particle trajectory and pene-trability.Besides,stress distribution on the carbonate rock showed that the tensile and shear failure would more easily occur by SC-CO_(2) jet than that by water jet.Moreover,pressure and temperature control the jet field and seepage field of sC-CO_(2) simultaneously.Increasing the jet temperature can effectively enhance the impingement effect and seepage process by decreasing the viscosity and density of SC-CO_(2).The key findings are expected to provide a theoretical basis and design reference for applying SC-CO_(2) jet fracturing in carbonate geothermal reservoirs.

Evaluation of the Factors Controlling Concentration of Non-Condensable Gases and Their Possible Impact on the Performance of Geothermal Systems: Case Study of Olkaria Wells in the Kenyan Rift Valley

The Olkaria geothermal field is located in the Kenyan Rift valley, about 120 km from Nairobi. Development of geothermal resources in the Olkaria area, a high temperature field, started in the early 1950s. In the subsequent years numerous expansions have been carried out with additional power plants being installed in Olkaria. These include a binary plant at Olkaria South West (Olkaria III) in 2000, a condensing plant at Olkaria North East (Olkaria II) in 2003, another binary plant at Olkaria North West (Oserian) in 2004 and finally condensing plants in the year 2014 within East production field (EPF) and Olkaria Domes (OD) areas. The total generation from this field is about 730 Mw. The study considered samples from 4 producing wells from 3 fields of the Olkaria geothermal area (OW-44 from the Olkaria East, OW-724A from the Olkaria North East, and OW-914 and OW-915 from the Olkaria Domes field). The chemical data were first analyzed using SOLVEQ. This helped in the determination of the equilibrium state of the system, the reservoir temperatures and the total moles to be run through CHILLER. The run CHILLER considered the processes that have been proven to be occurring in the Olkaria field i.e., boiling and condensing processes, fluid-fluid mixing rocks and titration resulting from water-rock interaction. The effects on gas evolution were evaluated based on the resulting recalculated gas pressures. The results indicate that the gas species are not in equilibrium with the mineral assemblages. The CHILLER evaluation shows boiling as the major process leading to the evolution of gases. OW-44 had the least gas concentrations, arising from the considered reservoir processes due to degassing, and near surface boiling, besides the removal of NH3, H2 and H2S are through the reaction with steam condensate. The gas breakout is most likely in OW-914 and least in OW-44. The study proposes different reservoir management strategies for the different parts of the Olkaria geothermal field. That is by increasing hot reinjection in the eastern sector around well OW-44. The reservoir around OW-914 is to be managed by operating the wells at a minimum flow rate (or even to close them) or the use of chemical inhibitors to prevent calcite scaling.

Geothermal anomalies in the Xianshuihe area: Implications for tunnel construction along the Sichuan-Tibet Railway, China

This study presents a comprehensively analysis of geothermal characteristics in the Xianshuihe geothermal area along the Sichuan-Tibet Railway,using temperature logging,temperature monitoring and thermal conductivity measurement,and regional geothermal geological survey data.The research focuses on the geothermal background,geothermal field,and their potential impact on the surrounding tunnels.The investigation reveals that the average heat flow value in the study area is approximately 73.0 mW/m^(2),significantly higher than the average terrestrial heat flow in China's Mainland(62.5 mW/m^(2)).This high terrestrial heat flow signifies a distinct thermal background in the area.In addition,geothermal anomalies in the area are found to be closely associated with the distribution of hot springs along NW faults,indicating a strong control by the Xianshuihe fault zone.The study concludes that the region's favorable conditions for geothermal resources are attributed to the combination of high terrestrial heatflow background and water-conducting faults.However,these conditions also pose a potential threat of heat damage to the tunnels along the Sichuan-Tibet Railway.To evaluate the risk,the research takes into account the terrestrial heat flow,thermal conductivity of the tunnel surrounding rocks,characteristics of the regional constant temperature layer,as well as the distribution of hot springs and faults.The analysis specifically focuses on the thermal damage risk of Kangding 1# tunnel and 2# tunnel passing through the study area.Based on the findings,it is determined that Kangding 1# tunnel and 2# tunnel have relatively low risk of heat damage,as they have avoided most of the high temperature anomaly areas.However,several sections of the tunnels do traverse zones with low to medium temperatures,where surface rock temperatures can reach up to 45℃.Therefore,these regions should not be neglected during the construction and operation of the tunnel project,and mitigation measures may be necessary to address the potential heat-related challenges in the area.

Spatio-temporal variations of shallow seismic velocity changes in Salton Sea Geothermal Field,California in response to large regional earthquakes and long-term geothermal activities

We measure spatio-temporal variations of seismic velocity changes in Salton Sea Geothermal Field,California based on cross correlations of daily seismic traces recorded by a borehole seismic network from December 2007 to January 2014.We find clear co-seismic velocity reductions during the 2010 M 7.2 El Mayor–Cucapah,Mexico earthquake at~100 km further south,followed by long-term recoveries.The co-seismic reductions are larger with longer post-seismic recoveries in higher frequency bands,indicating that material damage and healing process mostly occurred in the shallow depth.In addition,the co-seismic velocity reductions are larger for ray paths outside the active fluid injection/extraction regions.The ray paths inside injection/extraction regions are associated with smaller co-seismic reductions,but subtle long-term velocity increases.We also build 3D transient water flow models based on monthly injection/extraction rates,and find correlations between several water flow parameters and co-seismic velocity reductions.We interpret the relative lack of co-seismic velocity changes within the geothermal region as unclogging of fracture network due to persistent fluid flows of geothermal production.The long-term velocity increase is likely associated with the ground water depletion and subsidence due to net production.

Emerging the dual string drilling and dual coil tubing drilling technology in a geothermal well applications

The challenges found in geothermal well drilling have forced the industry to develop new significant cost effective,time saver technologies to go for deeper geothermal resources beyond their traditional limits.To overcome these challenges,the new Dual String Drilling(DSD)technology which is based on penetration pathway of drilling fluid and rock cuttings during drilling a well.The principle of DSD employs drilling fluid flows through the annulus of inner and outer string pipe while cutting from the bottom of the well through inner pipe.The paper describes the novel Dual String Drilling(DSD)technology,predicting their occurrence and advantages on drilling of geothermal well.The outcome shows that with DSD approach a lot of time will be saved to circulate the kick out of the well.Additionally,the characteristic response of DSD enables to improve the hole cleaning capacity,to prevent pipe stuck,better well stability,reduction in torque and drag,to remove the dynamic equivalent circulating density gradient in geothermal wells.Moreover,the paper also depicts the system and method for dual coil tubing drilling of horizontal well which follows the same principle as DSD.The comparison of DSD with conventional drilling assesses that the DSD technology is affordable and appropriate for geothermal well drilling.

Performance Characteristics of Geothermal Single Well for Building Heating

The single well geothermal heating(SWGH)technology has attracted extensive attention.To enhance heat extraction from SWGH,a mathematical model describing heat transfer is set up,and the key influence factor and heat transfer enhancement method are discussed by thermal resistance analysis.The numerical results show that the thermal resistance of rock is far greater than that of well wall and fluid.So,reducing rock thermal resistance is the most effective method for enhancing the heat extraction power.For geothermal well planning to drill:rock thermal resistance can be reduced by increasing well diameter and rock thermal conductivity;the temperature difference between liquid and rock can be raised by increasing well depth.For already existing geothermal well:an insulator with thermal conductivity of 0.2 W/(mK)is sufficient to preserve fluid enthalpy;a decrease in injection water temperature causes the increase of heat extraction power from geothermal well and heat output from heat pump simultaneously;increasing injection velocity causes the increase of pump power consumption and heat extraction power from geothermal well as well as net heat output between them.The entrepreneurs may refer to the above data in actual project.Furthermore,filling composite materials with high thermal conductivity into leakage formation is proposed in order to reduce the thermal resistance of rocks.

Geothermal Investigations in Permafrost Regions—The Duration of Temperature Monitoring after Wellbores Shut-In

The most important data on the thermal regime of the Earth’s interior come from temperature measurements in deep boreholes. The drilling process greatly alters the temperature field of formations surrounding the wellbore. In permafrost regions, due to thawing of the formation surrounding the wellbore during drilling, representative data can be obtained only by repeated observations over a long period of time (up to 10 years). Usually a number of temperature logs (3 - 10) are taken after the well’s shut-in. Significant expenses (manpower, transportation) are required to monitor the temperature regime of deep wells. In this paper we show that in most of the cases (when the time of refreezing formations is less than the shut-in time) two temperature logs are sufficient to predict formations temperatures during shut-in, to determine the geothermal gradients, and to evaluate the thickness of the permafrost zone. Thus the cost of monitoring the temperature regime of deep wells after shut-in can be drastically reduced. A simple method to process field data (for the well sections below and above the permafrost base) is presented. Temperature logs conducted in two wells were used to demonstrate utilization of this method.

Performance Simulation of a Modified Geothermal Grain Dryer Based at Menengai Well 3 in Kenya

Geothermal energy can be effectively utilized for grain drying to reduce carbon emissions and also cut operational costs associated with conventional methods. The main challenges encountered in the use of the geothermal grain dryer, such as in Menengai, Kenya, include uneven grain drying and long throughput times. Grains near the hot air inlet dry at a faster rate compared to those near the exhaust end. Therefore, the grains must be recirculated within the dryer to achieve uniform moisture distribution. Grain recirculation is energy-intensive as it utilizes electricity running the elevator motors in addition to the suction pump. A Computational Fluid Dynamics (CFD) model was developed to study the airflow pattern and its impact on drying of maize. The model was simulated in ANSYS 21 and validated using experimental data. Finite volume discretization method was employed for meshing. Pressure-based segregated solver was used in the Computational Fluid Dynamics (CFD) simulation. Also, K-Omega turbulent model was used for enhancing wall treatment. The findings indicate that non-uniform hot air distribution across the grain buffer section causes uneven drying. Introducing filleted flow-guides results in a relatively uniform velocity, temperature, and turbulence kinetic energy distribution across the dryer. The average velocity and temperature magnitudes in lower compartments increased by 153.3% and 0.25% respectively for the improved dryer. In the upper compartments, the velocity and temperature increase were 176.5% and 0.22% respectively.