Pub Date : 2024-11-17DOI: 10.1016/j.geothermics.2024.103199
Ozioma Carol Uwakwe , Sylvia Riechelmann , Mathias Mueller , Thomas Reinsch , Martin Balcewicz , Onyedika Anthony Igbokwe , Adrian Immenhauser
Mineral precipitates along thermal fluid pathways (scaling) and clogging by unconsolidated grains inversely affect the efficiency of geothermal systems. An experimental approach is presented to quantify dissolution-precipitation processes in fractured, geologically complex carbonate rocks of Devonian age. The outcome suggests that the dissolution-precipitation processes must be placed in the context of different fluid properties and pressure conditions between the injection and the production well. A geochemical monitoring program documenting the processes in the carbonate aquifer rocks is presented. Experimental work must be combined with field and modelling approaches to unfold its full strength.
{"title":"Scaling in fractured geothermal carbonate reservoir rocks: An experimental approach","authors":"Ozioma Carol Uwakwe , Sylvia Riechelmann , Mathias Mueller , Thomas Reinsch , Martin Balcewicz , Onyedika Anthony Igbokwe , Adrian Immenhauser","doi":"10.1016/j.geothermics.2024.103199","DOIUrl":"10.1016/j.geothermics.2024.103199","url":null,"abstract":"<div><div>Mineral precipitates along thermal fluid pathways (scaling) and clogging by unconsolidated grains inversely affect the efficiency of geothermal systems. An experimental approach is presented to quantify dissolution-precipitation processes in fractured, geologically complex carbonate rocks of Devonian age. The outcome suggests that the dissolution-precipitation processes must be placed in the context of different fluid properties and pressure conditions between the injection and the production well. A geochemical monitoring program documenting the processes in the carbonate aquifer rocks is presented. Experimental work must be combined with field and modelling approaches to unfold its full strength.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103199"},"PeriodicalIF":3.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660303","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 : 2024-11-17DOI: 10.1016/j.geothermics.2024.103204
Haoxin Shi , Yanjun Zhang , Yuxiang Cheng , Jixiang Guo , Jianqiao Zheng , Xin Zhang , Yude Lei , Yongjie Ma , Lin Bai
Accurately assessing geothermal potential is a significant global challenge, and the development of reservoir temperature prediction models is a key aspect of evaluating this potential. Machine learning modeling serves as an effective tool in this process. However, before modeling, the inability to fully screen complex and nonlinear input features, combined with the insufficiency of datasets, often impacts the predictive accuracy of the models. This study collected hydrochemical test data from 65 groundwater samples in the Guide area of Qinghai Province from 2009 to 2016. To address the issue of missing data, we employed the LRTC-TNN method to supplement the dataset. Subsequently, we conducted correlation analysis on the data features using normalization and Pearson correlation coefficients to identify important features. Based on the processed dataset, we constructed XGBoost and LightGBM models and used 5-fold cross-validation and Bayesian optimization model to select the optimal combination of model parameters. In the modeling analysis, we explored the advantages and disadvantages of both models and evaluated their performance in terms of accuracy, robustness, and generalization capability. The results indicate that the model performs best when 80% of the training data is used. The LRTC-TNN model effectively fills in missing data, achieving an accuracy exceeding 95%. When applying the XGBoost and LightGBM models to the training set, test set, and complete dataset, the XGBoost model consistently yielded significant predictive results, specifically an R² value of 98.09%, a RMSE of 0.546, and a MAE of 0.396. Robustness analysis showed that the XGBoost model is more robust, while feature importance and sensitivity analysis revealed that chloride ions are the key independent variable affecting reservoir temperature predictions. Furthermore, generalization capability validation indicated that the model can adapt well to different datasets and provide accurate predictive results. In conclusion, the XGBoost model, which considers complementary data, demonstrates excellent generality in reservoir temperature prediction, providing a reliable solution for accurately determining underground reservoir temperatures.
{"title":"A novel machine learning approach for reservoir temperature prediction","authors":"Haoxin Shi , Yanjun Zhang , Yuxiang Cheng , Jixiang Guo , Jianqiao Zheng , Xin Zhang , Yude Lei , Yongjie Ma , Lin Bai","doi":"10.1016/j.geothermics.2024.103204","DOIUrl":"10.1016/j.geothermics.2024.103204","url":null,"abstract":"<div><div>Accurately assessing geothermal potential is a significant global challenge, and the development of reservoir temperature prediction models is a key aspect of evaluating this potential. Machine learning modeling serves as an effective tool in this process. However, before modeling, the inability to fully screen complex and nonlinear input features, combined with the insufficiency of datasets, often impacts the predictive accuracy of the models. This study collected hydrochemical test data from 65 groundwater samples in the Guide area of Qinghai Province from 2009 to 2016. To address the issue of missing data, we employed the LRTC-TNN method to supplement the dataset. Subsequently, we conducted correlation analysis on the data features using normalization and Pearson correlation coefficients to identify important features. Based on the processed dataset, we constructed XGBoost and LightGBM models and used 5-fold cross-validation and Bayesian optimization model to select the optimal combination of model parameters. In the modeling analysis, we explored the advantages and disadvantages of both models and evaluated their performance in terms of accuracy, robustness, and generalization capability. The results indicate that the model performs best when 80% of the training data is used. The LRTC-TNN model effectively fills in missing data, achieving an accuracy exceeding 95%. When applying the XGBoost and LightGBM models to the training set, test set, and complete dataset, the XGBoost model consistently yielded significant predictive results, specifically an R² value of 98.09%, a RMSE of 0.546, and a MAE of 0.396. Robustness analysis showed that the XGBoost model is more robust, while feature importance and sensitivity analysis revealed that chloride ions are the key independent variable affecting reservoir temperature predictions. Furthermore, generalization capability validation indicated that the model can adapt well to different datasets and provide accurate predictive results. In conclusion, the XGBoost model, which considers complementary data, demonstrates excellent generality in reservoir temperature prediction, providing a reliable solution for accurately determining underground reservoir temperatures.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103204"},"PeriodicalIF":3.5,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660293","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 : 2024-11-16DOI: 10.1016/j.geothermics.2024.103200
Yaoshun Yuan, Juan Du, Pingli Liu, Ming Wang, Jinming Liu, Xiang Chen
Geothermal tailwater recharge is an inevitable way to achieve sustainable and efficient development of geothermal resources and water resource recycling. However, as the recharge time of sandstone geothermal recharge wells increases, the recharge rate decreases, severely restricting the development and utilization of geothermal resources. The mechanism of water injection damage and the process of enhancing permeability have not been comprehensively studied, and effective measures to improve the efficiency and permeability of sandstone geothermal reservoirs are lacking. This study takes three reservoir rock samples from the Zhangjiapo Group, Lantian-Bahe Group, and Gaolingqun Group in the Xianyang geothermal field as the research objects. The ``micro+macro'' analysis method was used to study the reservoir characteristics. Water injection damage simulation experiments and scaling trend prediction were conducted. The mechanism of geothermal well damage is clarified from multiple aspects. Four acid systems including mud acid, fluoroboric acid, multi-hydro acid, and solid acid were used to conduct core flooding experiments, revealing the mechanism of permeability enhancement and simulating the acidification stimulation effect indoors. The results show that three layers of the Xianyang geothermal field are composed mainly of sandy mudstone, and fine and medium-fine sandstone, with strong heterogeneity. During the process of tailwater recharge, blockage damage must occur, and environmental conditions such as pressure and temperature changes can easily cause scaling damage. Mud acid causes severe dissolution of the rock core end face, and cannot achieve deep unblocking. The ability of multi-hydro acid stimulation is good, and the permeability increases by 3.18–15.47 times. Multi-hydro acid formed a single acid channel in the core of the Zhangjiapo Group, effectively removing blockages in deep layers. Solid acid can effectively protect the integrity of rock cores. After solid acid stimulation, the core structures of the three layers were intact, and the permeability has increased by 1.66–3.17 times. For loosely cemented reservoirs, solid acids can be used for acid stimulation. This study examined the effectiveness of chemical stimulation with four types of acid in sandstone geothermal reservoirs, demonstrated the feasibility of acidizing sandstone geothermal wells, and provided a scientific reference for improving the permeability and recharge rate of sandstone geothermal reservoirs.
{"title":"Research on acidizing blockage removal and perfusion enhancement technology for sandstone geothermal reservoir recharge wells","authors":"Yaoshun Yuan, Juan Du, Pingli Liu, Ming Wang, Jinming Liu, Xiang Chen","doi":"10.1016/j.geothermics.2024.103200","DOIUrl":"10.1016/j.geothermics.2024.103200","url":null,"abstract":"<div><div>Geothermal tailwater recharge is an inevitable way to achieve sustainable and efficient development of geothermal resources and water resource recycling. However, as the recharge time of sandstone geothermal recharge wells increases, the recharge rate decreases, severely restricting the development and utilization of geothermal resources. The mechanism of water injection damage and the process of enhancing permeability have not been comprehensively studied, and effective measures to improve the efficiency and permeability of sandstone geothermal reservoirs are lacking. This study takes three reservoir rock samples from the Zhangjiapo Group, Lantian-Bahe Group, and Gaolingqun Group in the Xianyang geothermal field as the research objects. The ``micro+macro'' analysis method was used to study the reservoir characteristics. Water injection damage simulation experiments and scaling trend prediction were conducted. The mechanism of geothermal well damage is clarified from multiple aspects. Four acid systems including mud acid, fluoroboric acid, multi-hydro acid, and solid acid were used to conduct core flooding experiments, revealing the mechanism of permeability enhancement and simulating the acidification stimulation effect indoors. The results show that three layers of the Xianyang geothermal field are composed mainly of sandy mudstone, and fine and medium-fine sandstone, with strong heterogeneity. During the process of tailwater recharge, blockage damage must occur, and environmental conditions such as pressure and temperature changes can easily cause scaling damage. Mud acid causes severe dissolution of the rock core end face, and cannot achieve deep unblocking. The ability of multi-hydro acid stimulation is good, and the permeability increases by 3.18–15.47 times. Multi-hydro acid formed a single acid channel in the core of the Zhangjiapo Group, effectively removing blockages in deep layers. Solid acid can effectively protect the integrity of rock cores. After solid acid stimulation, the core structures of the three layers were intact, and the permeability has increased by 1.66–3.17 times. For loosely cemented reservoirs, solid acids can be used for acid stimulation. This study examined the effectiveness of chemical stimulation with four types of acid in sandstone geothermal reservoirs, demonstrated the feasibility of acidizing sandstone geothermal wells, and provided a scientific reference for improving the permeability and recharge rate of sandstone geothermal reservoirs.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103200"},"PeriodicalIF":3.5,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660302","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 : 2024-11-15DOI: 10.1016/j.geothermics.2024.103198
Kai Qi , Zhanli Ren , Junping Cui , Qiang Yu , Fenfei Bai , Xinshe Liu , Zhipeng Chen , Guangyuan Xing
The Ordos Basin, a pivotal large-scale superimposed basin in China, boasts substantial oil and gas reserves. This article employs steady-state temperature (SST) from 42 wells and oil testing temperature (OTT) data from over 400 wells to conduct a comprehensive analysis of the present-day geothermal gradient, thermal properties, heat flow, and deep temperature (4 000 m, 6 000 m, and the top surface of the Proterozoic and Ordovician) in the Ordos Basin. Furthermore, the thermal lithospheric thickness (TLT), Moho temperature, and heat flow ratio of crustal to mantle are calculated. The findings reveal that the geothermal gradient within the basin mainly distributed between 22-31 °C/km, averaging at 28 °C/km. The surface heat flow, ranging from 46 to 71 mW/m2, with a mean of 62 mW/m2, positions the basin as a medium-temperature. Temperatures at 4 000 m and 6 000 m depths vary from 105-155 °C and 150-230 °C respectively, exhibiting a "high in the east and south and low in the west and north" pattern. Temperature at the top surface of the Ordovician ranges from 60 to 130 °C and exceeds 145 °C in the Proterozoic. The present-day TLT in the basin varies between 80 and 160 km, gradually increasing towards the west. Intriguingly, heat flow ratio of crustal to mantle in the west is significantly greater than 1, indicating a lithospheric structure of "hot crust and cold mantle". The present-day geothermal field in the basin is primarily influenced by deep thermal structures and rock thermal properties. This study contributes to the deep oil and gas exploration and basin dynamics in the Ordos Basin.
{"title":"Present-day deep geothermal field and lithospheric thermal structure in the Ordos Basin","authors":"Kai Qi , Zhanli Ren , Junping Cui , Qiang Yu , Fenfei Bai , Xinshe Liu , Zhipeng Chen , Guangyuan Xing","doi":"10.1016/j.geothermics.2024.103198","DOIUrl":"10.1016/j.geothermics.2024.103198","url":null,"abstract":"<div><div>The Ordos Basin, a pivotal large-scale superimposed basin in China, boasts substantial oil and gas reserves. This article employs steady-state temperature (SST) from 42 wells and oil testing temperature (OTT) data from over 400 wells to conduct a comprehensive analysis of the present-day geothermal gradient, thermal properties, heat flow, and deep temperature (4 000 m, 6 000 m, and the top surface of the Proterozoic and Ordovician) in the Ordos Basin. Furthermore, the thermal lithospheric thickness (TLT), Moho temperature, and heat flow ratio of crustal to mantle are calculated. The findings reveal that the geothermal gradient within the basin mainly distributed between 22-31 °C/km, averaging at 28 °C/km. The surface heat flow, ranging from 46 to 71 mW/m<sup>2</sup>, with a mean of 62 mW/m<sup>2</sup>, positions the basin as a medium-temperature. Temperatures at 4 000 m and 6 000 m depths vary from 105-155 °C and 150-230 °C respectively, exhibiting a \"high in the east and south and low in the west and north\" pattern. Temperature at the top surface of the Ordovician ranges from 60 to 130 °C and exceeds 145 °C in the Proterozoic. The present-day TLT in the basin varies between 80 and 160 km, gradually increasing towards the west. Intriguingly, heat flow ratio of crustal to mantle in the west is significantly greater than 1, indicating a lithospheric structure of \"hot crust and cold mantle\". The present-day geothermal field in the basin is primarily influenced by deep thermal structures and rock thermal properties. This study contributes to the deep oil and gas exploration and basin dynamics in the Ordos Basin.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103198"},"PeriodicalIF":3.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660300","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 : 2024-11-15DOI: 10.1016/j.geothermics.2024.103196
Sarah E. Gelman, Erick R. Burns
<div><div>As part of U.S. Geological Survey's (USGS) efforts to identify and assess geothermal energy resources of the US, a three-dimensional (3D) geologic and thermal model has been constructed for the Williston Basin, USA. The geologic model consists of all sedimentary units above the Proterozoic and Archean crystalline rock (called basement herein), with a total sedimentary thickness of up to 5 km near the basin center. Twenty-nine geologic units were mapped from interpreted formation tops from 16,465 wells. A 3D temperature model was constructed to a depth of 7 km by constructing a 3D heat flow model for the sedimentary units, followed by estimating underlying temperature using a one-dimensional (1D) analytic solution for heat flow within the underlying crystalline basement. Using the sedimentary basin model, heat flow was simulated in 3D and was calibrated using three temperature datasets: 1) 24 high-confidence static temperature logs (equilibrium thermal profiles), 2) more than15,000 drill stem test (DST) measurements from >7,000 wells, and 3) more than 45,000 bottomhole temperature (BHT) measurements from >14,000 wells. The DST and BHT datasets provide broad spatial coverage, but are lower confidence, primarily because measurements were made prior to attaining thermal equilibrium. DST and BHT measurements were binned regionally to develop representative thermal profiles that generally agree with these lower quality data (hereafter called pseudowell temperature profiles). Layer properties (primarily thermal conductivity and compaction curves) were set to best estimate values, then the heat flow model was calibrated to fit pseudowell and static temperature logs primarily by adjusting basal heat flow to approximate the overall temperature profile. Minor adjustments to thermal conductivity allowed adjusting changes in slope at lithologic contacts. Resulting maps include 3D temperature and basal (bottom of sedimentary units) heat flow estimates, which are used as input for the temperature model of the basement. The crystalline basement temperature model uses an analytic 1D solution to the heat flow equation that requires estimates of heat flow and temperature at the upper boundary (i.e., the sediment/basement contact), radiogenic heat production within the crystalline basement, and reference thermal conductivity (i.e., uncorrected for temperature). Two regions of high heat flow are identified: 1) in western North Dakota along the North American Central Plains Conductivity Anomaly and 2) in eastern Montana near the Poplar dome. Within the sedimentary column in the center of the basin of the basin, an area of approximately 100,000 km<sup>2</sup> is predicted to have moderate- to high-temperature geothermal resources (>90 °C) under the thickest sequences of sediments. Where thick insulation and high heat flow coincide, electric-grade resources can be less than 4 km deep. Assuming a maximum feasible drilling depth of 7 km, temperatures ar
{"title":"Three-dimensional temperature maps of the Williston Basin, USA: Implications for deep hot sedimentary and enhanced geothermal resources","authors":"Sarah E. Gelman, Erick R. Burns","doi":"10.1016/j.geothermics.2024.103196","DOIUrl":"10.1016/j.geothermics.2024.103196","url":null,"abstract":"<div><div>As part of U.S. Geological Survey's (USGS) efforts to identify and assess geothermal energy resources of the US, a three-dimensional (3D) geologic and thermal model has been constructed for the Williston Basin, USA. The geologic model consists of all sedimentary units above the Proterozoic and Archean crystalline rock (called basement herein), with a total sedimentary thickness of up to 5 km near the basin center. Twenty-nine geologic units were mapped from interpreted formation tops from 16,465 wells. A 3D temperature model was constructed to a depth of 7 km by constructing a 3D heat flow model for the sedimentary units, followed by estimating underlying temperature using a one-dimensional (1D) analytic solution for heat flow within the underlying crystalline basement. Using the sedimentary basin model, heat flow was simulated in 3D and was calibrated using three temperature datasets: 1) 24 high-confidence static temperature logs (equilibrium thermal profiles), 2) more than15,000 drill stem test (DST) measurements from >7,000 wells, and 3) more than 45,000 bottomhole temperature (BHT) measurements from >14,000 wells. The DST and BHT datasets provide broad spatial coverage, but are lower confidence, primarily because measurements were made prior to attaining thermal equilibrium. DST and BHT measurements were binned regionally to develop representative thermal profiles that generally agree with these lower quality data (hereafter called pseudowell temperature profiles). Layer properties (primarily thermal conductivity and compaction curves) were set to best estimate values, then the heat flow model was calibrated to fit pseudowell and static temperature logs primarily by adjusting basal heat flow to approximate the overall temperature profile. Minor adjustments to thermal conductivity allowed adjusting changes in slope at lithologic contacts. Resulting maps include 3D temperature and basal (bottom of sedimentary units) heat flow estimates, which are used as input for the temperature model of the basement. The crystalline basement temperature model uses an analytic 1D solution to the heat flow equation that requires estimates of heat flow and temperature at the upper boundary (i.e., the sediment/basement contact), radiogenic heat production within the crystalline basement, and reference thermal conductivity (i.e., uncorrected for temperature). Two regions of high heat flow are identified: 1) in western North Dakota along the North American Central Plains Conductivity Anomaly and 2) in eastern Montana near the Poplar dome. Within the sedimentary column in the center of the basin of the basin, an area of approximately 100,000 km<sup>2</sup> is predicted to have moderate- to high-temperature geothermal resources (>90 °C) under the thickest sequences of sediments. Where thick insulation and high heat flow coincide, electric-grade resources can be less than 4 km deep. Assuming a maximum feasible drilling depth of 7 km, temperatures ar","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103196"},"PeriodicalIF":3.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660301","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 : 2024-11-15DOI: 10.1016/j.geothermics.2024.103201
Ricardo Caires Formigari, Cristina de Hollanda Cavalcanti Tsuha
Energy piles are a type of geothermal exchanger, used in ground source heat pump systems, to provide heating or cooling energy for thermal comfort purposes, due to their cost advantages compared to deep borehole heat exchangers. This type of technology is still not used in Brazil, where the hot dominating weather and space-cooling demand predominate, and soils in unsaturated condition cover a significant part of the land surface. In this case of unbalanced heat transfer to the ground, this system may cause the increase of pile and ground temperatures over time, reducing its efficiency. Additionally, in unsaturated soils the ground thermal conductivity is normally inferior compared to saturated soils, and for this reason the increase of pile and ground temperatures with time may be more significant. Moreover, the positive impact of a groundwater flow on the heat transfer performance does not occur. Therefore, the current work investigates the thermal performance of energy piles with three different heat exchanger pipe configurations, in a typical Brazilian unsaturated tropical soil, with the aim of providing fundamental guidance for future application of this sustainable technology for the challenging combination of predominant cooling demand and unsaturated soil condition. For this study, asymmetrical and spiral pipe configurations and different operation modes were evaluated by field experiments to verify if these variables can influence the energy pile performance. Thermal performance tests were carried out on bored energy piles installed at a site of unsaturated soil in São Carlos city, Brazil. The energy pile of asymmetrical W-pipe configuration under intermittent operation mode presented a better heat transfer performance, and a lower increase of the average pile temperature compared to the spiral configuration case. These aspects can be advantageous for energy pile groups and also for the heat transfer performance and thermo-mechanical behaviour of a single energy pile.
能源桩是一种地热交换器，用于地源热泵系统，为热舒适目的提供供暖或制冷能源，与深井热交换器相比具有成本优势。这种技术在巴西仍未得到应用，因为巴西天气炎热，空间冷却需求占主导地位，非饱和状态的土壤覆盖了很大一部分地表。在这种向地面传热不平衡的情况下，该系统可能会随着时间的推移导致桩体和地面温度升高，从而降低其效率。此外，在非饱和土壤中，地面导热性通常不如饱和土壤，因此随着时间的推移，桩基和地面温度的升高可能会更加明显。此外，地下水流不会对传热性能产生积极影响。因此，目前的工作研究了在巴西典型的非饱和热带土壤中，采用三种不同热交换器管道配置的能源桩的热性能，目的是为未来应用这种可持续技术提供基本指导，以应对主要冷却需求和非饱和土壤条件的挑战性组合。在这项研究中，通过现场实验评估了非对称和螺旋管配置以及不同的运行模式，以验证这些变量是否会影响能量堆的性能。在巴西圣卡洛斯市的一个非饱和土壤场地安装的钻孔能源桩上进行了热性能测试。在间歇运行模式下，非对称 W 型管结构的能源桩具有更好的传热性能，与螺旋结构的能源桩相比，平均桩温的上升幅度较低。这些方面对于能源桩群以及单个能源桩的传热性能和热机械性能都是有利的。
{"title":"Experimental investigation on the impact of the asymmetrical heat exchange and operation modes on the thermal performance of a bored energy pile in unsaturated soil: A case study in Brazil","authors":"Ricardo Caires Formigari, Cristina de Hollanda Cavalcanti Tsuha","doi":"10.1016/j.geothermics.2024.103201","DOIUrl":"10.1016/j.geothermics.2024.103201","url":null,"abstract":"<div><div>Energy piles are a type of geothermal exchanger, used in ground source heat pump systems, to provide heating or cooling energy for thermal comfort purposes, due to their cost advantages compared to deep borehole heat exchangers. This type of technology is still not used in Brazil, where the hot dominating weather and space-cooling demand predominate, and soils in unsaturated condition cover a significant part of the land surface. In this case of unbalanced heat transfer to the ground, this system may cause the increase of pile and ground temperatures over time, reducing its efficiency. Additionally, in unsaturated soils the ground thermal conductivity is normally inferior compared to saturated soils, and for this reason the increase of pile and ground temperatures with time may be more significant. Moreover, the positive impact of a groundwater flow on the heat transfer performance does not occur. Therefore, the current work investigates the thermal performance of energy piles with three different heat exchanger pipe configurations, in a typical Brazilian unsaturated tropical soil, with the aim of providing fundamental guidance for future application of this sustainable technology for the challenging combination of predominant cooling demand and unsaturated soil condition. For this study, asymmetrical and spiral pipe configurations and different operation modes were evaluated by field experiments to verify if these variables can influence the energy pile performance. Thermal performance tests were carried out on bored energy piles installed at a site of unsaturated soil in São Carlos city, Brazil. The energy pile of asymmetrical W-pipe configuration under intermittent operation mode presented a better heat transfer performance, and a lower increase of the average pile temperature compared to the spiral configuration case. These aspects can be advantageous for energy pile groups and also for the heat transfer performance and thermo-mechanical behaviour of a single energy pile.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103201"},"PeriodicalIF":3.5,"publicationDate":"2024-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660294","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 : 2024-11-13DOI: 10.1016/j.geothermics.2024.103189
Xin Tang , Yingchun Wang , Haoxin Jia , Guangzheng Jiang , Yinhui Zuo , Rongcai Song
The behavior of fault belt is related to temperature, pressure, rock characteristics and fluid activity while the heat transfer processes play crucial role on the dynamic behavior of the fault. However, the thermal characteristic of large strike-slip fault in activity orogenic belt is still unclear. This study constructed a thermal budget model of the Xianshuihe Fault Zone by using four elements model—pure conduction, rainfall infiltration, groundwater discharge, and frictional heating—the different heat fluxes at various depths in the study area were calculated. The spatial characteristics and variations of heat flux with depth were analyzed. The results show that the surface heat flux in the study area is approximately 22 W/m² which is consistent with the soil heat flux measurement. Among the heat flux models, rainfall convection and groundwater discharge are the primary controls of heat transfer which contributing 9.84 W/m² and 8.67 W/m², respectively. These two parts account for over 80 % of the surface heat flux at shallow depths (1–3 km). The pure conduction contributes around 0.16 W/m² approximately 1 % of the total while the frictional heating model provides a surface heat flux of 3.13 W/m², accounting for about 14 % of the total. At depths exceeding 9 km, the frictional heating increasing and contribution exceeds 95 % that is the primary controls of heat transfer in the deeper parts. Our thermal budget results are therefore crucial to understanding the heat accumulation processes and earthquake regime on the fault zone.
{"title":"Thermal budget of hydrothermal systems for the Xianshuihe fault belt in the SE Tibetan Plateau: Insights to the geothermal accumulation processes","authors":"Xin Tang , Yingchun Wang , Haoxin Jia , Guangzheng Jiang , Yinhui Zuo , Rongcai Song","doi":"10.1016/j.geothermics.2024.103189","DOIUrl":"10.1016/j.geothermics.2024.103189","url":null,"abstract":"<div><div>The behavior of fault belt is related to temperature, pressure, rock characteristics and fluid activity while the heat transfer processes play crucial role on the dynamic behavior of the fault. However, the thermal characteristic of large strike-slip fault in activity orogenic belt is still unclear. This study constructed a thermal budget model of the Xianshuihe Fault Zone by using four elements model—pure conduction, rainfall infiltration, groundwater discharge, and frictional heating—the different heat fluxes at various depths in the study area were calculated. The spatial characteristics and variations of heat flux with depth were analyzed. The results show that the surface heat flux in the study area is approximately 22 W/m² which is consistent with the soil heat flux measurement. Among the heat flux models, rainfall convection and groundwater discharge are the primary controls of heat transfer which contributing 9.84 W/m² and 8.67 W/m², respectively. These two parts account for over 80 % of the surface heat flux at shallow depths (1–3 km). The pure conduction contributes around 0.16 W/m² approximately 1 % of the total while the frictional heating model provides a surface heat flux of 3.13 W/m², accounting for about 14 % of the total. At depths exceeding 9 km, the frictional heating increasing and contribution exceeds 95 % that is the primary controls of heat transfer in the deeper parts. Our thermal budget results are therefore crucial to understanding the heat accumulation processes and earthquake regime on the fault zone.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103189"},"PeriodicalIF":3.5,"publicationDate":"2024-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142660289","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 : 2024-11-11DOI: 10.1016/j.geothermics.2024.103193
Shimin Wang , Pengtao Wang , Jian'an Wang , Rui Liang , Jie Zhang , Ke Zhang , Jian Liu , Xingchen Lu , Shaoqiang Sui , Shengshan Bi
The medium-deep coaxial borehole heat exchanger (MDCBHE) utilizes mid-deep geothermal energy for building heating via a heat transfer process. The heat extraction performance of MDCBHE is influenced by multiple factors. Previous studies mainly analyzed the short-term influence of major affecting factors on a single evaluation parameter. Long-term effect of multiple factors on multiple evaluation parameters has not been well investigated. Therefore, this study constructed a full-scale three-dimensional model to study the heat extraction characteristic of MDCBHE for a geothermal energy heating system. The Taguchi method was employed to analyze the influence degree and contribution rate of 9 influencing factors on 4 assessment indexes including heat exchange per meter (QL−5a), heat pump unit performance coefficient (COP−5a), rock temperature decay rate (Dsoil−5a) and buried pipe heat transfer attenuation rate (Rd−5a). The results show that the inlet water temperature has the most significant effect on QL−5a and COP−5a, with a contribution rate of 35.27 % and 53.70 %, respectively. Rock and soil density and the thermal conductivity have the greatest influence on Dsoil−5a and Rd−5, with a contribution rate of 43.48 % and 39.58 %, respectively. Finally, the matrix method was used for multi-index optimization to determine the influencing factors on the total contribution rate of the four evaluation parameters. The study results can provide guidance for the location and system design of MDCBHE.
{"title":"Multi-factor optimization of coaxial borehole heat exchanger based on Taguchi and matrix method","authors":"Shimin Wang , Pengtao Wang , Jian'an Wang , Rui Liang , Jie Zhang , Ke Zhang , Jian Liu , Xingchen Lu , Shaoqiang Sui , Shengshan Bi","doi":"10.1016/j.geothermics.2024.103193","DOIUrl":"10.1016/j.geothermics.2024.103193","url":null,"abstract":"<div><div>The medium-deep coaxial borehole heat exchanger (MDCBHE) utilizes mid-deep geothermal energy for building heating via a heat transfer process. The heat extraction performance of MDCBHE is influenced by multiple factors. Previous studies mainly analyzed the short-term influence of major affecting factors on a single evaluation parameter. Long-term effect of multiple factors on multiple evaluation parameters has not been well investigated. Therefore, this study constructed a full-scale three-dimensional model to study the heat extraction characteristic of MDCBHE for a geothermal energy heating system. The Taguchi method was employed to analyze the influence degree and contribution rate of 9 influencing factors on 4 assessment indexes including heat exchange per meter (<em>Q</em><sub>L−5a</sub>), heat pump unit performance coefficient (<em>COP<sub>−</sub></em><sub>5a</sub>), rock temperature decay rate (<em>D</em><sub>soil−5a</sub>) and buried pipe heat transfer attenuation rate (<em>R</em><sub>d−5a</sub>). The results show that the inlet water temperature has the most significant effect on <em>Q</em><sub>L−5a</sub> and <em>COP<sub>−</sub></em><sub>5a</sub>, with a contribution rate of 35.27 % and 53.70 %, respectively. Rock and soil density and the thermal conductivity have the greatest influence on <em>D</em><sub>soil−5a</sub> and <em>R</em><sub>d−5</sub>, with a contribution rate of 43.48 % and 39.58 %, respectively. Finally, the matrix method was used for multi-index optimization to determine the influencing factors on the total contribution rate of the four evaluation parameters. The study results can provide guidance for the location and system design of MDCBHE.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103193"},"PeriodicalIF":3.5,"publicationDate":"2024-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659717","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 : 2024-11-10DOI: 10.1016/j.geothermics.2024.103195
Eugene G. Pashuk , Ada E. Ramazanova , Ilmutdin M. Abdulagatov
The effect of pressure on thermal conductivity is an important for understanding the heat transfer processes in modeling applications in geothermal reservoirs and for optimization of the technology of geothermal energy extraction processes. The primary factors affecting the economics of any geothermal energy recovery process are the amount of heat present in the geothermal reservoir and rate of heat extraction, which strongly depend on the thermal properties of the reservoir rocks, which are functions of both temperature and pressure. The present paper aims to study the variation of thermal conductivity of five sandstone samples from the Germany Geothermal Field with various total (open and close) porosities of (6.8, 13.0, 15.44, 21.3, and 21.5%) with pressure up to 203 MPa, to overcome the existing lack of thermal conductivity data for the geothermal reservoir modeling. The improved steady-state heat-flow technique (contact method) was used to precisely (with an uncertainty of 4%) measure the thermal conductivity of the sandstone samples. Unlike previous studies, in the present work the effect of the contact thermal resistance on the measured values of thermal conductivity has been taken into account using a calibration procedure to increase the accuracy and reliability of the measured data. The results show that with the increase of the pressure at a fixed temperature of 293.15 K, the thermal conductivity of sandstone is linearly increasing with pressure from 0.52 to 1.73 GPa−1 depending on sandstone structural and mineralogical composition, porosity, and other characteristics, which falls in the same range reported by other authors for rock samples from different geothermal fields. The derived values of the thermal conductivity pressure coefficient are crucial for geothermal studies in order to effectively use the geothermal resources of the region, and are useful for scientific applications such as the development and testing of the accuracy, reliability, and predictive capability of existing thermal models of geothermal reservoirs. Based on the present experimental results, statistical analysis (correlation analysis) was revealed between the measured thermal conductivity of sandstone samples and open and close porosities. The role of closed and open porosities on the pressure dependence of thermal conductivity and elastic moduli is discussed. For the first time, we experimentally observed the difference of the influence of the open and closed porosities on the thermal conductivity and elastic properties of sandstones. It was experimentally confirmed that the effect of closed porosity on the thermal conductivity of sandstones is significantly greater than that of open porosity by 15 to 20%. The obtained results show that it is of great importance to study the changes in the thermal properties of the sandstones under pressure at realistic reservoir conditions for geothermal studies.
{"title":"High-pressure thermal conductivity, speed of ultrasonic measurements and derived elastic modulus of sandstones with different porosity","authors":"Eugene G. Pashuk , Ada E. Ramazanova , Ilmutdin M. Abdulagatov","doi":"10.1016/j.geothermics.2024.103195","DOIUrl":"10.1016/j.geothermics.2024.103195","url":null,"abstract":"<div><div>The effect of pressure on thermal conductivity is an important for understanding the heat transfer processes in modeling applications in geothermal reservoirs and for optimization of the technology of geothermal energy extraction processes. The primary factors affecting the economics of any geothermal energy recovery process are the amount of heat present in the geothermal reservoir and rate of heat extraction, which strongly depend on the thermal properties of the reservoir rocks, which are functions of both temperature and pressure. The present paper aims to study the variation of thermal conductivity of five sandstone samples from the Germany Geothermal Field with various total (open and close) porosities of (6.8, 13.0, 15.44, 21.3, and 21.5%) with pressure up to 203 MPa, to overcome the existing lack of thermal conductivity data for the geothermal reservoir modeling. The improved steady-state heat-flow technique (contact method) was used to precisely (with an uncertainty of 4%) measure the thermal conductivity of the sandstone samples. Unlike previous studies, in the present work the effect of the contact thermal resistance on the measured values of thermal conductivity has been taken into account using a calibration procedure to increase the accuracy and reliability of the measured data. The results show that with the increase of the pressure at a fixed temperature of 293.15 K, the thermal conductivity of sandstone is linearly increasing with pressure from 0.52 to 1.73 GPa<sup>−1</sup> depending on sandstone structural and mineralogical composition, porosity, and other characteristics, which falls in the same range reported by other authors for rock samples from different geothermal fields. The derived values of the thermal conductivity pressure coefficient are crucial for geothermal studies in order to effectively use the geothermal resources of the region, and are useful for scientific applications such as the development and testing of the accuracy, reliability, and predictive capability of existing thermal models of geothermal reservoirs. Based on the present experimental results, statistical analysis (correlation analysis) was revealed between the measured thermal conductivity of sandstone samples and open and close porosities. The role of closed and open porosities on the pressure dependence of thermal conductivity and elastic moduli is discussed. For the first time, we experimentally observed the difference of the influence of the open and closed porosities on the thermal conductivity and elastic properties of sandstones. It was experimentally confirmed that the effect of closed porosity on the thermal conductivity of sandstones is significantly greater than that of open porosity by 15 to 20%. The obtained results show that it is of great importance to study the changes in the thermal properties of the sandstones under pressure at realistic reservoir conditions for geothermal studies.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103195"},"PeriodicalIF":3.5,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659716","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}
Geothermal energy represents a large-output, high-capacity, and sustainable energy source for electric power generation, with critical implications for the transition toward a low-carbon society; hence, it is crucial to accurately explore and assess geothermal resources. Many areas rich in geothermal resources are located in non-arid, densely vegetated regions. Therefore, the purpose of this study was to develop a method, applicable at the first stage of regional resource exploration, using hyperspectral remotely-sensed images to detect surface geothermal manifestations with high reliability in densely vegetated areas. The Patuha geothermal field in West Java, Indonesia, was selected as the study area given the availability of accumulated survey data to validate our proposed method. A single satellite image acquired by the Hyperion sensor was used for the case study. Two vegetation indices were defined to detect spectral features of stressed vegetation: a blue shift of the red edge and an increase in shortwave-infrared reflectance. These indices were suitable to detect vegetation stress under soil acidification conditions caused by ascending geothermal water and gases. After normalization to a zero mean and unit standard deviation, these indices were combined into a single vegetation index considering blue shift and shortwave-infrared reflectance (VIBS). The advantage of the VIBS over the normalized difference vegetation index was demonstrated by better correspondence with geothermal manifestations and better consistency along major faults. By further combining the VIBS values (in vegetated areas) with mineral weights calculated by linear spectral unmixing for kaolinite (in non-vegetated areas), we proposed a new index, the geothermal manifestation potential (GMP). General matching between high-GMP zones and geothermal manifestations or fault traces demonstrated the usefulness of this index; this was confirmed by field survey measurements of reflectance spectral features characterizing vegetation under geothermal stress. Additionally, the highest-GMP zones were located near surface water possessing high sulfate concentrations and above a deep vapor-dominated underground reservoir.
{"title":"Combining vegetation index with mineral identification for detection of high-geothermal-potential zones using hyperspectral satellite data","authors":"Taiki Kubo , Hiroaki Gonnokami , Arie Naftali Hawu Hede , Katsuaki Koike","doi":"10.1016/j.geothermics.2024.103194","DOIUrl":"10.1016/j.geothermics.2024.103194","url":null,"abstract":"<div><div>Geothermal energy represents a large-output, high-capacity, and sustainable energy source for electric power generation, with critical implications for the transition toward a low-carbon society; hence, it is crucial to accurately explore and assess geothermal resources. Many areas rich in geothermal resources are located in non-arid, densely vegetated regions. Therefore, the purpose of this study was to develop a method, applicable at the first stage of regional resource exploration, using hyperspectral remotely-sensed images to detect surface geothermal manifestations with high reliability in densely vegetated areas. The Patuha geothermal field in West Java, Indonesia, was selected as the study area given the availability of accumulated survey data to validate our proposed method. A single satellite image acquired by the Hyperion sensor was used for the case study. Two vegetation indices were defined to detect spectral features of stressed vegetation: a blue shift of the red edge and an increase in shortwave-infrared reflectance. These indices were suitable to detect vegetation stress under soil acidification conditions caused by ascending geothermal water and gases. After normalization to a zero mean and unit standard deviation, these indices were combined into a single vegetation index considering blue shift and shortwave-infrared reflectance (VIBS). The advantage of the VIBS over the normalized difference vegetation index was demonstrated by better correspondence with geothermal manifestations and better consistency along major faults. By further combining the VIBS values (in vegetated areas) with mineral weights calculated by linear spectral unmixing for kaolinite (in non-vegetated areas), we proposed a new index, the geothermal manifestation potential (GMP). General matching between high-GMP zones and geothermal manifestations or fault traces demonstrated the usefulness of this index; this was confirmed by field survey measurements of reflectance spectral features characterizing vegetation under geothermal stress. Additionally, the highest-GMP zones were located near surface water possessing high sulfate concentrations and above a deep vapor-dominated underground reservoir.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"125 ","pages":"Article 103194"},"PeriodicalIF":3.5,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142659714","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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