Given the rapidly increasing demand for rechargeable batteries and the EU's net-zero targets, lithium is an important building block for the future energy economy, but resources in Germany are limited to unconventional deposits with unknown quantities. Here, we focus on lithium resources in northern Germany and assess their potential using a probabilistic volume approach. The estimated capacity across all target horizons is 4.73 Mt with a possible range of 0. 39 to 26.51 Mt of lithium metal. However, the most promising resources lie in the low-permeability Permian deposits and require new frontier play concepts.
{"title":"Lithium prospectivity and capacity assessment in Northern Germany","authors":"Katharina Alms , Manfred Heinelt , Alicia Groeneweg","doi":"10.1016/j.geothermics.2024.103207","DOIUrl":"10.1016/j.geothermics.2024.103207","url":null,"abstract":"<div><div>Given the rapidly increasing demand for rechargeable batteries and the EU's net-zero targets, lithium is an important building block for the future energy economy, but resources in Germany are limited to unconventional deposits with unknown quantities. Here, we focus on lithium resources in northern Germany and assess their potential using a probabilistic volume approach. The estimated capacity across all target horizons is 4.73 Mt with a possible range of 0. 39 to 26.51 Mt of lithium metal. However, the most promising resources lie in the low-permeability Permian deposits and require new frontier play concepts.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103207"},"PeriodicalIF":3.5,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-12DOI: 10.1016/j.geothermics.2024.103212
S. Namie, M. Alamooti
The Williston Basin, a vast intracratonic sedimentary basin extending across eastern Montana, western North Dakota, South Dakota, and southern Saskatchewan, holds significant potential for geothermal energy exploration. Within this basin lies the Deadwood Formation, a sedimentary layer of the Sauk Sequence, dating from the Upper Cambrian to Lower Ordovician epochs. The Deadwood Formation's substantial thickness, complex lithology, elevated temperatures, and unique geochemical properties make it a promising target for Enhanced Geothermal Systems (EGS). This study addresses critical challenges in EGS design by refining bottom-hole temperature (BHT) correction methods and conducting comprehensive geochemical analyses specific to the Deadwood Formation.
We developed new BHT correction models tailored to the Formation's unique thermal characteristics using polynomial regression on well-log data. Our results show that traditional BHT correction methods, developed for other sedimentary basins, lack accuracy when applied to the Williston Basin. The new correction framework significantly improves temperature estimations, allowing for a more reliable geothermal assessment. Additionally, the geochemical analysis of Deadwood Formation brines revealed high total dissolved solids (TDS) and a Na-Cl-dominated ionic composition, with varying pH and redox conditions that present challenges for geothermal energy production, such as scaling and corrosion. Mineral saturation indices and Geothermometry techniques further indicate reservoir temperatures ranging from 150 °C to 225 °C, suggesting favorable conditions for geothermal extraction.
This study's novel integration of refined BHT corrections with in-depth geochemical characterization provides a robust foundation for optimizing EGS design in the Deadwood Formation. It also offers a reference framework for geothermal resource development in similar sedimentary basins.
{"title":"Enhancing geothermal assessment: Coupled BHT and hydrogeochemical approach in north dakota's Deadwood Formation","authors":"S. Namie, M. Alamooti","doi":"10.1016/j.geothermics.2024.103212","DOIUrl":"10.1016/j.geothermics.2024.103212","url":null,"abstract":"<div><div>The Williston Basin, a vast intracratonic sedimentary basin extending across eastern Montana, western North Dakota, South Dakota, and southern Saskatchewan, holds significant potential for geothermal energy exploration. Within this basin lies the Deadwood Formation, a sedimentary layer of the Sauk Sequence, dating from the Upper Cambrian to Lower Ordovician epochs. The Deadwood Formation's substantial thickness, complex lithology, elevated temperatures, and unique geochemical properties make it a promising target for Enhanced Geothermal Systems (EGS). This study addresses critical challenges in EGS design by refining bottom-hole temperature (BHT) correction methods and conducting comprehensive geochemical analyses specific to the Deadwood Formation.</div><div>We developed new BHT correction models tailored to the Formation's unique thermal characteristics using polynomial regression on well-log data. Our results show that traditional BHT correction methods, developed for other sedimentary basins, lack accuracy when applied to the Williston Basin. The new correction framework significantly improves temperature estimations, allowing for a more reliable geothermal assessment. Additionally, the geochemical analysis of Deadwood Formation brines revealed high total dissolved solids (TDS) and a Na-Cl-dominated ionic composition, with varying pH and redox conditions that present challenges for geothermal energy production, such as scaling and corrosion. Mineral saturation indices and Geothermometry techniques further indicate reservoir temperatures ranging from 150 °C to 225 °C, suggesting favorable conditions for geothermal extraction.</div><div>This study's novel integration of refined BHT corrections with in-depth geochemical characterization provides a robust foundation for optimizing EGS design in the Deadwood Formation. It also offers a reference framework for geothermal resource development in similar sedimentary basins.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103212"},"PeriodicalIF":3.5,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148038","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-12DOI: 10.1016/j.geothermics.2024.103240
Haoyuan Hu , Gaofeng Ye , Baochun Li , Sheng Jin , Xiangcheng Yi , Haoxiang Yin , Yuchen Hao , Yuancheng Zhao , Yunyun Zhang
The North China Craton has undergone destruction due to westward subduction of the Paleo-Pacific Plate, causing significant thinning of its eastern lithosphere. The thinner lithosphere facilitates easier heat conduction to the shallow crust. The Jizhong Depression is located at the center of the cratonic destruction area, featuring numerous large uplift-type geothermal fields. To investigate the geothermal genesis mechanism of uplift-type geothermal fields in the Jizhong Depression, this study employs 237 magnetotelluric data. It constructs, for the first time, a three-dimensional electrical structure model of the Jizhong Depression and then combines regional data to analyze the geothermal system from the perspectives of caprock, heat source, water channel, and heat reservoir. The shallow part of the Central Uplift Zone exhibits low electrical resistivity, surmising the presence of a sand-mud caprock. In the mid-lower crust, a large-scale low-resistivity body C2 is identified, speculated to be a shear zone formed by the Taihang Mountain Piedmont Fault rather than a magma chamber. The upper mantle contains a low-resistivity body C4, which may be partially melting due to the upwelling of upper mantle material along the tectonically weak zones of the lithosphere since the Meso–Cenozoic. Based on calculations, the water content and melt fraction of the low-resistivity body C4 are estimated as 0.5∼3 wt% and 2∼12 %, respectively. The result indicates that the Central Uplift Zone has a significant burial depth for the sand-mud caprock, and the thicker caprock plays an influential insulating role. The Gaoyang and Niudong–Hexiwu faults are major deep-seated faults that transfer deep heat to the shallow crust through thermal convection. Geothermal energy primarily originates from the mantle, where mantle heat flow is transferred to the shallow layers through thermal conduction and convection without an additional magma chamber for heating.
{"title":"The geothermal field genesis mechanism in the central uplift of the Jizhong depression: A study based on magnetotelluric imaging","authors":"Haoyuan Hu , Gaofeng Ye , Baochun Li , Sheng Jin , Xiangcheng Yi , Haoxiang Yin , Yuchen Hao , Yuancheng Zhao , Yunyun Zhang","doi":"10.1016/j.geothermics.2024.103240","DOIUrl":"10.1016/j.geothermics.2024.103240","url":null,"abstract":"<div><div>The North China Craton has undergone destruction due to westward subduction of the Paleo-Pacific Plate, causing significant thinning of its eastern lithosphere. The thinner lithosphere facilitates easier heat conduction to the shallow crust. The Jizhong Depression is located at the center of the cratonic destruction area, featuring numerous large uplift-type geothermal fields. To investigate the geothermal genesis mechanism of uplift-type geothermal fields in the Jizhong Depression, this study employs 237 magnetotelluric data. It constructs, for the first time, a three-dimensional electrical structure model of the Jizhong Depression and then combines regional data to analyze the geothermal system from the perspectives of caprock, heat source, water channel, and heat reservoir. The shallow part of the Central Uplift Zone exhibits low electrical resistivity, surmising the presence of a sand-mud caprock. In the mid-lower crust, a large-scale low-resistivity body C2 is identified, speculated to be a shear zone formed by the Taihang Mountain Piedmont Fault rather than a magma chamber. The upper mantle contains a low-resistivity body C4, which may be partially melting due to the upwelling of upper mantle material along the tectonically weak zones of the lithosphere since the Meso–Cenozoic. Based on calculations, the water content and melt fraction of the low-resistivity body C4 are estimated as 0.5∼3 wt% and 2∼12 %, respectively. The result indicates that the Central Uplift Zone has a significant burial depth for the sand-mud caprock, and the thicker caprock plays an influential insulating role. The Gaoyang and Niudong–Hexiwu faults are major deep-seated faults that transfer deep heat to the shallow crust through thermal convection. Geothermal energy primarily originates from the mantle, where mantle heat flow is transferred to the shallow layers through thermal conduction and convection without an additional magma chamber for heating.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103240"},"PeriodicalIF":3.5,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-04DOI: 10.1016/j.geothermics.2024.103221
Maria Gracia C. Padrique , Mark Jeremy G. Narag , Allan Gil S. Fernando , Maricor N. Soriano
The qualitative assessment of a geothermal reservoir using petrography is often conducted during drilling to assess the permeability, porosity, and mineral geothermometry of the reservoir rocks especially when little is known about the subsurface during the exploration stage. The petrographic analysis includes visually estimating pore and vein fractions, identifying rock textures, describing the degree of alteration, recognizing the hydrothermal alteration minerals and indicated temperature, and noting the presence of shearing and various porosity types. This traditional method of visual estimation and assessment is prone to errors when averaging fields of view and can be labor-intensive, especially during time-sensitive drilling operations when a geologist must analyze hundreds of thin sections per well under a polarizing light microscope. In this study, indicated porosity levels were assigned to 103 geothermal core thin sections based on the grouping of the rock parameters as observed under a polarizing light microscope. To enhance the traditional visual assessment in petrography, this study trained and validated convolutional neural networks (CNNs) in the automatic rating of porosity based on these parameters and in the detection of epidote, a key production marker in high-temperature magmatic-intrusive geothermal systems. Photomicrographs of the geothermal well core thin sections were utilized as input data for training and validating the ResNet, AlexNet, and VGGNet architectures. The three CNN architectures achieved porosity classification precision ranging from 0.74 to 0.84, and epidote detection precision between 0.90 and 1.0 in plane-polarized light (PPL) photomicrographs. The results demonstrate that CNNs can significantly augment traditional petrography in evaluating geothermal well samples.
{"title":"Enhancing geothermal petrography with convolutional neural networks","authors":"Maria Gracia C. Padrique , Mark Jeremy G. Narag , Allan Gil S. Fernando , Maricor N. Soriano","doi":"10.1016/j.geothermics.2024.103221","DOIUrl":"10.1016/j.geothermics.2024.103221","url":null,"abstract":"<div><div>The qualitative assessment of a geothermal reservoir using petrography is often conducted during drilling to assess the permeability, porosity, and mineral geothermometry of the reservoir rocks especially when little is known about the subsurface during the exploration stage. The petrographic analysis includes visually estimating pore and vein fractions, identifying rock textures, describing the degree of alteration, recognizing the hydrothermal alteration minerals and indicated temperature, and noting the presence of shearing and various porosity types. This traditional method of visual estimation and assessment is prone to errors when averaging fields of view and can be labor-intensive, especially during time-sensitive drilling operations when a geologist must analyze hundreds of thin sections per well under a polarizing light microscope. In this study, indicated porosity levels were assigned to 103 geothermal core thin sections based on the grouping of the rock parameters as observed under a polarizing light microscope. To enhance the traditional visual assessment in petrography, this study trained and validated convolutional neural networks (CNNs) in the automatic rating of porosity based on these parameters and in the detection of epidote, a key production marker in high-temperature magmatic-intrusive geothermal systems. Photomicrographs of the geothermal well core thin sections were utilized as input data for training and validating the ResNet, AlexNet, and VGGNet architectures. The three CNN architectures achieved porosity classification precision ranging from 0.74 to 0.84, and epidote detection precision between 0.90 and 1.0 in plane-polarized light (PPL) photomicrographs. The results demonstrate that CNNs can significantly augment traditional petrography in evaluating geothermal well samples.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103221"},"PeriodicalIF":3.5,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148041","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-04DOI: 10.1016/j.geothermics.2024.103211
C. Esteve , Y. Lu , J.M. Gosselin , R. Kramer , Y. Aiman , G. Bokelmann
The Schwechat depression, in the Vienna Basin (VB) is currently the main target area for deep geothermal exploration in eastern Austria. Knowledge of the subsurface heavily relies on active seismic reflection profiling experiments that are expensive and logistically demanding. Affordable geophysical prospecting methods are needed to reduce subsurface uncertainty over large spatial areas. Over recent years, seismic ambient noise tomography (ANT) has proven to be a cost-effective and environment-friendly exploration technique fulfilling this need. Here, we present an ANT study of the central Vienna Basin revealing the shear-wave velocity, and shear-wave radial anisotropy structure down to 5 km beneath the surface. We deployed an array of 100 seismic nodal instruments during 5 weeks over summer 2023. We measured fundamental-mode Rayleigh and Love-wave group velocity dispersion from seismic noise correlations, and employed transdimensional Bayesian tomography to invert for isotropic Rayleigh and Love group velocity maps at periods ranging from 0.8 to 5.5 s. We then extracted Rayleigh and Love group velocity dispersion curves from the maps at all locations, and jointly inverted them for shear-wave velocity and radial anisotropy as a function of depth using a transdimensional Bayesian framework.
Our shear-wave velocity model reveals a basin-like low-velocity feature, interpreted as the seismic signature of the Schwechat depression. Another low-velocity feature is observed beneath the city of Vienna, which could be of great interest for geothermal exploration. The shear-wave velocity radial anisotropy structure indicates a thin negative anisotropy layer in the top 150 meters, likely associated with water-saturated open cracks. Between 150 meters and 1.5 km depth, we observe widespread positive radial anisotropy across the entire study area, corresponding to sub-horizontal layering within the Neogene basin. At greater depths, the Schwechat depression is characterized by positive radial anisotropy, while the edges of the Schwechat depression exhibit negative radial anisotropy due to steeply dipping strata and normal faults responsible for the formation of this major depocenter in the Vienna Basin.
{"title":"The seismic signature and geothermal potential of the Schwechat Depression in the Vienna Basin, Austria, from ambient noise tomography","authors":"C. Esteve , Y. Lu , J.M. Gosselin , R. Kramer , Y. Aiman , G. Bokelmann","doi":"10.1016/j.geothermics.2024.103211","DOIUrl":"10.1016/j.geothermics.2024.103211","url":null,"abstract":"<div><div>The Schwechat depression, in the Vienna Basin (VB) is currently the main target area for deep geothermal exploration in eastern Austria. Knowledge of the subsurface heavily relies on active seismic reflection profiling experiments that are expensive and logistically demanding. Affordable geophysical prospecting methods are needed to reduce subsurface uncertainty over large spatial areas. Over recent years, seismic ambient noise tomography (ANT) has proven to be a cost-effective and environment-friendly exploration technique fulfilling this need. Here, we present an ANT study of the central Vienna Basin revealing the shear-wave velocity, and shear-wave radial anisotropy structure down to 5 km beneath the surface. We deployed an array of 100 seismic nodal instruments during 5 weeks over summer 2023. We measured fundamental-mode Rayleigh and Love-wave group velocity dispersion from seismic noise correlations, and employed transdimensional Bayesian tomography to invert for isotropic Rayleigh and Love group velocity maps at periods ranging from 0.8 to 5.5 s. We then extracted Rayleigh and Love group velocity dispersion curves from the maps at all locations, and jointly inverted them for shear-wave velocity and radial anisotropy as a function of depth using a transdimensional Bayesian framework.</div><div>Our shear-wave velocity model reveals a basin-like low-velocity feature, interpreted as the seismic signature of the Schwechat depression. Another low-velocity feature is observed beneath the city of Vienna, which could be of great interest for geothermal exploration. The shear-wave velocity radial anisotropy structure indicates a thin negative anisotropy layer in the top 150 meters, likely associated with water-saturated open cracks. Between 150 meters and 1.5 km depth, we observe widespread positive radial anisotropy across the entire study area, corresponding to sub-horizontal layering within the Neogene basin. At greater depths, the Schwechat depression is characterized by positive radial anisotropy, while the edges of the Schwechat depression exhibit negative radial anisotropy due to steeply dipping strata and normal faults responsible for the formation of this major depocenter in the Vienna Basin.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103211"},"PeriodicalIF":3.5,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-03DOI: 10.1016/j.geothermics.2024.103208
Heru Berian Pratama , Katsuaki Koike , Angga Bakti Pratama , Brenda Ariesty Kusumasari , Ali Ashat , Sutopo , Tubagus Ahmad Fauzi Soelaiman
Geothermal energy is a crucial renewable resource that can generate large power continuously but requires integrated and accurate assessments of its development and utilization for long-term and sustainable exploitation. Accordingly, this study develops an assessment framework considering all the influential factors for power generation: the potential capacity; silica scaling; type of power generation system; and temporal changes in the pressure, temperature, and fluid saturation in the reservoir. The applicability and effectiveness of the proposed method are demonstrated via a case study of the Bedugul geothermal two-phase system on Bali Island, Indonesia, using a calibrated numerical model and a stochastic resource assessment. The numerical model is a combination of wellbore, silica scaling, and thermodynamic power generation models. On the basis of the wellbore model by the Hagedorn and Brown pressure drop correlation, the calculated means of the production capacity and enthalpy from the liquid reservoir are 39.0 kg/s and 1340 kJ/kg, respectively. Using double-flash and flash-binary power generation systems over an exploitation period with a two-phase reservoir temperature of 260 °C, a reinjection temperature of 130 °C, and a silica scaling model, the predicted production from the liquid reservoir can sustain a power generation of 60 MWe, which is equivalent to 70 % of the power potential, according to a stochastic resource assessment using the Plackett–Burman design. The double-flash system is found to generate 1.0 MWe more power (a 1.6 % increase relative to the baseline capacity) than the flash-binary system using pentane as working fluid and to extend the lifetime of the make-up wells by 2.5 years. Consequently, it is vital, at an early stage of development, to understand the nature and properties of reservoirs and the thermodynamics of power generation systems via comprehensive research and reliable and accurate assessments of the power production capacity.
{"title":"Numerical simulation–based optimization of an integrated framework for the efficient development and sustainable utilization of geothermal resources: Application to the Bedugul geothermal field","authors":"Heru Berian Pratama , Katsuaki Koike , Angga Bakti Pratama , Brenda Ariesty Kusumasari , Ali Ashat , Sutopo , Tubagus Ahmad Fauzi Soelaiman","doi":"10.1016/j.geothermics.2024.103208","DOIUrl":"10.1016/j.geothermics.2024.103208","url":null,"abstract":"<div><div>Geothermal energy is a crucial renewable resource that can generate large power continuously but requires integrated and accurate assessments of its development and utilization for long-term and sustainable exploitation. Accordingly, this study develops an assessment framework considering all the influential factors for power generation: the potential capacity; silica scaling; type of power generation system; and temporal changes in the pressure, temperature, and fluid saturation in the reservoir. The applicability and effectiveness of the proposed method are demonstrated via a case study of the Bedugul geothermal two-phase system on Bali Island, Indonesia, using a calibrated numerical model and a stochastic resource assessment. The numerical model is a combination of wellbore, silica scaling, and thermodynamic power generation models. On the basis of the wellbore model by the Hagedorn and Brown pressure drop correlation, the calculated means of the production capacity and enthalpy from the liquid reservoir are 39.0 kg/s and 1340 kJ/kg, respectively. Using double-flash and flash-binary power generation systems over an exploitation period with a two-phase reservoir temperature of 260 °C, a reinjection temperature of 130 °C, and a silica scaling model, the predicted production from the liquid reservoir can sustain a power generation of 60 MWe, which is equivalent to 70 % of the power potential, according to a stochastic resource assessment using the Plackett–Burman design. The double-flash system is found to generate 1.0 MWe more power (a 1.6 % increase relative to the baseline capacity) than the flash-binary system using pentane as working fluid and to extend the lifetime of the make-up wells by 2.5 years. Consequently, it is vital, at an early stage of development, to understand the nature and properties of reservoirs and the thermodynamics of power generation systems via comprehensive research and reliable and accurate assessments of the power production capacity.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103208"},"PeriodicalIF":3.5,"publicationDate":"2024-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148036","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-30DOI: 10.1016/j.geothermics.2024.103210
Shu Zhu , Jinhai Zheng , Luming Zhou , Bei Han , Yue Tong , Junyu Wu
Understanding the alteration in rock mechanics post heating and cyclic cooling is crucial for hot dry rock geothermal energy extraction projects. Against this backdrop, a constitutive model adept at delineating rock behavior under cyclic heating-cooling scenarios is introduced. The model presumes rock micro-element failure to adhere to the Weibull distribution and is constructed upon an octahedral shear stress strength criterion, integrating thermal and mechanical damage statistics. Model parameters were derived via the peak point method. The model's validity was ascertained through heating-cycle cooling-uniaxial compression experiments on hot dry granite. The experimental outcomes substantiate the model's efficacy. Within the model, the parameters r and S are not only of practical physical significance but also serve as indices to quantify rock brittleness and peak strength, respectively. The findings of this study are expected to contribute theoretical insights for deep geotechnical engineering applications, including geothermal resource extraction.
{"title":"Study on the statistical damage constitutive model and experiment of hot dry rock cyclic heating-cooling based on the octahedral strength criterion","authors":"Shu Zhu , Jinhai Zheng , Luming Zhou , Bei Han , Yue Tong , Junyu Wu","doi":"10.1016/j.geothermics.2024.103210","DOIUrl":"10.1016/j.geothermics.2024.103210","url":null,"abstract":"<div><div>Understanding the alteration in rock mechanics post heating and cyclic cooling is crucial for hot dry rock geothermal energy extraction projects. Against this backdrop, a constitutive model adept at delineating rock behavior under cyclic heating-cooling scenarios is introduced. The model presumes rock micro-element failure to adhere to the Weibull distribution and is constructed upon an octahedral shear stress strength criterion, integrating thermal and mechanical damage statistics. Model parameters were derived via the peak point method. The model's validity was ascertained through heating-cycle cooling-uniaxial compression experiments on hot dry granite. The experimental outcomes substantiate the model's efficacy. Within the model, the parameters r and S are not only of practical physical significance but also serve as indices to quantify rock brittleness and peak strength, respectively. The findings of this study are expected to contribute theoretical insights for deep geotechnical engineering applications, including geothermal resource extraction.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"126 ","pages":"Article 103210"},"PeriodicalIF":3.5,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-29DOI: 10.1016/j.geothermics.2024.103203
Rubén Vidal , Maarten W. Saaltink
Geochemistry of groundwater is affected by temperature among other things. We propose a novel method that can be used to develop analytical and semi-analytical solutions for calculating reaction rates for non-isothermal cases, to verify numerical models and give a better understanding of thermo-hydro-chemical (THC) processes. Aqueous and mineral reactions are assumed in equilibrium. The method decouples the chemistry from the thermo-hydraulic (TH) processes. The chemical part of the method consists of batch calculations in which minerals dissolve or precipitate and water chemistry varies as a result of changing temperature. The thermo-hydraulic part consists of calculating temperature and spatial and temporal derivatives of temperature. From this, chemical composition of groundwater and precipitation or dissolution rates of minerals can be calculated straightforwardly. We applied the method to a simple 1D steady state case, for which an analytical solution could be obtained, and to a 2D Aquifer Thermal Energy Storage (ATES) system of the Forsthaus pilot project near Bern (Switzerland), for which we developed a semi-analytical solution. The use of the method for the simulation of this ATES system reduced computational costs seven-fold in comparison with a standard numerical code. Moreover, the method has provided understanding on the dominant reactive transport processes (which we have divided into mixing, heat retardation and heat conduction terms), mineral reaction rates and porosity changes of the two cases. At interfaces with abrupt changes in temperature gradients, reaction rates tend to infinity. A comparison of thermodynamic databases reveals that not only the temperature dependencies of chemical properties are important, but also first and second derivatives with respect to temperature.
{"title":"A novel method for decoupling thermo-hydraulic processes from chemical reactions to understand the effect of heat on chemical reaction","authors":"Rubén Vidal , Maarten W. Saaltink","doi":"10.1016/j.geothermics.2024.103203","DOIUrl":"10.1016/j.geothermics.2024.103203","url":null,"abstract":"<div><div>Geochemistry of groundwater is affected by temperature among other things. We propose a novel method that can be used to develop analytical and semi-analytical solutions for calculating reaction rates for non-isothermal cases, to verify numerical models and give a better understanding of thermo-hydro-chemical (THC) processes. Aqueous and mineral reactions are assumed in equilibrium. The method decouples the chemistry from the thermo-hydraulic (TH) processes. The chemical part of the method consists of batch calculations in which minerals dissolve or precipitate and water chemistry varies as a result of changing temperature. The thermo-hydraulic part consists of calculating temperature and spatial and temporal derivatives of temperature. From this, chemical composition of groundwater and precipitation or dissolution rates of minerals can be calculated straightforwardly. We applied the method to a simple 1D steady state case, for which an analytical solution could be obtained, and to a 2D Aquifer Thermal Energy Storage (ATES) system of the Forsthaus pilot project near Bern (Switzerland), for which we developed a semi-analytical solution. The use of the method for the simulation of this ATES system reduced computational costs seven-fold in comparison with a standard numerical code. Moreover, the method has provided understanding on the dominant reactive transport processes (which we have divided into mixing, heat retardation and heat conduction terms), mineral reaction rates and porosity changes of the two cases. At interfaces with abrupt changes in temperature gradients, reaction rates tend to infinity. A comparison of thermodynamic databases reveals that not only the temperature dependencies of chemical properties are important, but also first and second derivatives with respect to temperature.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"126 ","pages":"Article 103203"},"PeriodicalIF":3.5,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-25DOI: 10.1016/j.geothermics.2024.103206
Yerkezhan Madenova , Luke P. Frash , Wenfeng Li , Meng Meng , Bijay K C , Jesse Hampton , Qiquan Xiong , Hari S. Viswanathan
Seismic risk associated with deep fluid injection is a major holdback for geothermal energy development. Currently adopted mitigation measures include traffic light protocol and cyclic stimulation methods that retroactively limit injection pressures and flowrates based on observed seismic activity to hopefully reduce the likelihood of triggering large seismic events. Fracture caging presents an alternative proactive approach to seismicity mitigation that does not require flow rate or injection pressure limits. The caging concept is to pre-drill boundary wells around injection wells to contain all injected fluid. Prior experimental and numerical work demonstrated successful caging of tensile hydraulic fractures but did not investigate caging in shear faults. To fill this knowledge gap, this study focuses on caging of injection-induced shear fractures in a critically stressed lab-scale shear fault. Experiment variables include mechanical versus hydraulic shearing and cage size by varied well spacing. Acoustic activity was monitored using two calibrated acoustic emission systems, each having a different sensitivity bandwidth. This constitutes what we call Caged Geothermal Systems (CGS) as a modified version of Enhanced Geothermal Systems (EGS), but with CGS using more wells, an accelerated drilling timetable, much higher flow rate limits, and less proppant. We demonstrate successful caging in a lab-scale shear fault with a high recovery of the injected fluid and prevention of large critical rupture events.
{"title":"Fracture caging in a lab fault to prevent seismic rupture during fluid injection","authors":"Yerkezhan Madenova , Luke P. Frash , Wenfeng Li , Meng Meng , Bijay K C , Jesse Hampton , Qiquan Xiong , Hari S. Viswanathan","doi":"10.1016/j.geothermics.2024.103206","DOIUrl":"10.1016/j.geothermics.2024.103206","url":null,"abstract":"<div><div>Seismic risk associated with deep fluid injection is a major holdback for geothermal energy development. Currently adopted mitigation measures include traffic light protocol and cyclic stimulation methods that retroactively limit injection pressures and flowrates based on observed seismic activity to hopefully reduce the likelihood of triggering large seismic events. Fracture caging presents an alternative proactive approach to seismicity mitigation that does not require flow rate or injection pressure limits. The caging concept is to pre-drill boundary wells around injection wells to contain all injected fluid. Prior experimental and numerical work demonstrated successful caging of tensile hydraulic fractures but did not investigate caging in shear faults. To fill this knowledge gap, this study focuses on caging of injection-induced shear fractures in a critically stressed lab-scale shear fault. Experiment variables include mechanical versus hydraulic shearing and cage size by varied well spacing. Acoustic activity was monitored using two calibrated acoustic emission systems, each having a different sensitivity bandwidth. This constitutes what we call Caged Geothermal Systems (CGS) as a modified version of Enhanced Geothermal Systems (EGS), but with CGS using more wells, an accelerated drilling timetable, much higher flow rate limits, and less proppant. We demonstrate successful caging in a lab-scale shear fault with a high recovery of the injected fluid and prevention of large critical rupture events.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"126 ","pages":"Article 103206"},"PeriodicalIF":3.5,"publicationDate":"2024-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-23DOI: 10.1016/j.geothermics.2024.103205
Anya M Seward , Robert R Reeves , Ed Mroczek , Nick Macdonald , Thomas Brakenrig
Assessments of surface heat loss from geothermal systems can provide information and insight into the size and dynamics of the underlying geothermal resource and provide constraints for numerical models. Historically, many different methods have been used to measure heat loss. However different techniques, and assumptions can result in a wide range of estimates with large errors. Surface heat loss is estimated in this paper using a variety of terrestrial based measurements and remote sensing data. Aerial thermal infrared data, calorimetry, temperature-depth profiles and chloride flux measurements were collected at the Waiotapu Geothermal Field, Taupo Volcanic Zone, New Zealand. Terrestrial measurements are integrated to determine a total heat loss for the area using a groundcover (vegetation) map determined from aerial photography.
A variety of methods for calculating heat loss are compared, with each technique providing insight into surface and subsurface heat transfer characteristics. Of note is the vast difference in the amount of heat lost from the transport of geothermal fluid to the surface compared to the amount of heat transferred through the ground compared to other New Zealand geothermal fields. Over 50% of the surface heat loss is emitted through evaporation, convection and conduction processes at the surface of water bodies, and an additional 40% is lost through directly discharging geothermal fluids into the Waiotapu Stream and tributaries. Less than 10% of heat is lost through heat transport from the ground.
Comparisons between heat loss determined from temperature-depth profiles and calorimetry vary drastically. We propose two potential causes for this. Firstly, a sinter deposit is present in the shallow subsurface which is acting as an insulator and preventing heat from reaching the surface, or secondly, the high air temperatures at the time of measurements suppressed the surface heat loss signal.
Aerial thermal infrared data are used to estimate the total heat loss from the ground and pool surfaces, while chloride flux of stream water is used to estimate the mass discharge into stream channels. A total heat loss from the Waiotapu Geothermal Field is estimated to be 456 MW which compares favourably to historically estimated heat loss values, ranging from 410 to 520 MW, using a variety of techniques.
{"title":"Surface heat loss assessment at the Waiotapu Geothermal Field, Taupo Volcanic Zone, New Zealand","authors":"Anya M Seward , Robert R Reeves , Ed Mroczek , Nick Macdonald , Thomas Brakenrig","doi":"10.1016/j.geothermics.2024.103205","DOIUrl":"10.1016/j.geothermics.2024.103205","url":null,"abstract":"<div><div>Assessments of surface heat loss from <span><span>geothermal systems</span><svg><path></path></svg></span> can provide information and insight into the size and dynamics of the underlying <span><span>geothermal resource</span><svg><path></path></svg></span> and provide constraints for numerical models. Historically, many different methods have been used to measure heat loss. However different techniques, and assumptions can result in a wide range of estimates with large errors. Surface heat loss is estimated in this paper using a variety of terrestrial based measurements and remote sensing data. Aerial thermal infrared data, calorimetry, temperature-depth profiles and chloride flux measurements were collected at the Waiotapu Geothermal Field, Taupo Volcanic Zone, New Zealand. Terrestrial measurements are integrated to determine a total heat loss for the area using a groundcover (vegetation) map determined from aerial photography.</div><div>A variety of methods for calculating heat loss are compared, with each technique providing insight into surface and subsurface heat transfer characteristics. Of note is the vast difference in the amount of heat lost from the transport of geothermal fluid to the surface compared to the amount of heat transferred through the ground compared to other New Zealand geothermal fields. Over 50% of the surface heat loss is emitted through evaporation, convection and conduction processes at the surface of water bodies, and an additional 40% is lost through directly discharging geothermal fluids into the Waiotapu Stream and tributaries. Less than 10% of heat is lost through heat transport from the ground.</div><div>Comparisons between heat loss determined from temperature-depth profiles and calorimetry vary drastically. We propose two potential causes for this. Firstly, a sinter deposit is present in the shallow subsurface which is acting as an insulator and preventing heat from reaching the surface, or secondly, the high air temperatures at the time of measurements suppressed the surface heat loss signal.</div><div>Aerial thermal infrared data are used to estimate the total heat loss from the ground and pool surfaces, while chloride flux of stream water is used to estimate the mass discharge into stream channels. A total heat loss from the Waiotapu Geothermal Field is estimated to be 456 MW which compares favourably to historically estimated heat loss values, ranging from 410 to 520 MW, using a variety of techniques.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"126 ","pages":"Article 103205"},"PeriodicalIF":3.5,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142720778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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