Geothermics最新文献_第4页

Study of the brittleness properties of granites under thermal and mechanical action through a new brittleness evaluation method

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-24 DOI: 10.1016/j.geothermics.2024.103235

Huijun Lu , Ru Zhang , Li Ren , Anlin Zhang , Zidong Fan , Kun Xiao , Wei Liu , Tao Huang

The brittleness of rock is important for guiding hydraulic fracturing methods for geothermal development. Existing brittleness evaluation methods (BEMs) have been summarized and analyzed. Nevertheless, there is no consensus thus far as to which criteria are the most reliable or appropriate. Energy distribution and plastic deformation are crucial factors in determining the scale of the brittleness from the analysis of the complete stress-strain curve. Moreover, the proposed BEM comprehensively considers the mechanical properties in the pre-peak and post-peak stages while also considering both energy distribution and plastic deformation. The brittleness indices (BIs) of materials with ideal plastic, ideal elastic-plastic, and super brittleness properties are evaluated as 0, 0.5, and 1, respectively, accurately reflecting the range of brittleness properties, from ideal plastic deformation to super brittle fracture. According to the sensitivity analysis of BI, the BIs of granite increase and then decrease for the change of water molecule content and microstructure with increasing temperature. The maximum and minimum BIs are 0.579 at 300 °C and 0.344 at 750 °C, respectively. The BIs of granite decreases substantially from 0.714 to 0.408 as the confining pressure increases from 0 to 40 MPa. These findings indicate that the brittleness of granite is strongly influenced by low confining pressures and high temperatures. Furthermore, the results are compared with those obtained using other widely used BEMs, confirming the superior predictive ability of the new BEM. This attribute is critical to enhancing the evaluation of brittleness in geothermal systems.

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引用次数: 0

Reliability of 3D finite-element and finite-difference inversion of magnetotelluric data including topography for geothermal exploration: Case study in Okuaizu geothermal field

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-24 DOI: 10.1016/j.geothermics.2024.103213

Toshihiro Uchida, Yusuke Yamaya

To investigate the performance of the three-dimensional (3D) inversion of magnetotelluric (MT) data for geothermal exploration (where accurate numerical modeling is essential for addressing rough topographies), we utilized two inversion codes (FEMTIC and WSINV3DMT) for the 3D inversion of MT data obtained from the Okuaizu geothermal area, northern Japan. FEMTIC is a finite-element (FEM) inversion code. It can incorporate tetrahedral elements (Tetra) or deformed nonconforming hexahedral elements (DHexa) to construct a 3D mesh. Meanwhile, WSINV3DMT is a finite-difference (FDM) inversion code. It uses rectangular cells to discretize the 3D domain. We prepared an identical subset of the MT data and set an identical noise floor to run the Tetra, DHexa, and WSINV3DMT inversions. The three inversions yielded similar 3D models. These displayed resistivity anomalies related to the cap rock and geothermal reservoir in the area. However, there are several significant differences in the model details, particularly between the FEMTIC and WSINV3DMT inversions. Numerical experiments on 3D synthetic data based on the inversion results of the field data were then conducted for DHexa and WSINV3DMT to examine the factors causing these differences. We set two low-resistivity anomalies (shallow and deep) embedded in a homogeneous earth with real topography. The experiments revealed that the DHexa inversion effectively recovered the two anomalies. However, the WSINV3DMT inversion may have failed to recover these. In particular, the deep anomaly was reconstructed ineffectively owing to numerical errors when we included a rough topographic variation in the model. Therefore, we considered that the inversion results of field data using an FDM code may have unreliable anomalies for an MT dataset obtained in a rough terrain environment. The inverted models of the field data in Okuaizu by Tetra and DHexa showed good agreement with existing borehole logging data and the geothermal conceptual model of the area.

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引用次数: 0

Crustal structure and deep geotherm of the Pearl River Delta in South China: Insights from gravity and thermal modeling

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-24 DOI: 10.1016/j.geothermics.2024.103245

Keyan Liao , Nansheng Qiu , Qianqian Feng , Chuanqing Zhu , Qiang Jiang

Granite-basin geothermal systems show promise as renewable resources for heat and potential electricity production. Nevertheless, a deeper understanding of their structural relationships and heat accumulation patterns is crucial for enhancing the exploration and evaluation of their energy potential. The intricate granite-basin structure evident on the surface of the Pearl River Delta (PRD) in South China poses significant challenges and uncertainties for deep geothermal exploration. To offer a deeper understanding, we introduce a comprehensive three-dimensional (3-D) lithospheric-scale structural model of the PRD, leveraging gravity anomaly and other geophysical data. Subsequently, utilizing this model as a foundation, we successfully derived the three-dimensional steady-state conductive thermal field of the crust through numerical simulation techniques. Our findings reveal that the deep fault zones control the morphology of basins and intrusions. The model indicates that the granite has an average thickness of approximately 3.5 km, whereas the region proximate to Hong Kong and Macau exhibits the greatest thickness (∼12 km). In forward modeling, the presence of significant gravity anomalies that cause challenges in accurately fitting within the Sanshui Basin and littoral region are attributed to basaltic intrusions located within the lower crust. The measured data reveals that the granites in the PRD have a high radiogenic heat production rate (average > 5 μW/m³). The thermal simulation result shows that the subsurface high-temperature areas are predominantly concentrated within the Sanshui Basin, Xinhui Basin, and Yunkai Massif. Notably, the surface heat flow exhibits considerable fluctuations, ranging from 68 and 122 mW/m², with granitic intrusions contributing as much as 48%. This study reveals that mantle heat serves as the primary controlling factor in the thermal field. Moreover, over half of the regions examined possess the capability to generate high-temperature geothermal resources.

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引用次数: 0

Geothermal heat pump solutions for frost heave control in railway subgrades

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-24 DOI: 10.1016/j.geothermics.2024.103244

Tianfei Hu , Liqi Zhao , Tengfei Wang , Zurun Yue , Yifei Yuan , Yimin Zhang

Frost heaving in railway subgrades presents persistent challenges for rail operations in cold regions, causing significant track deformation and maintenance demands. This study introduces and evaluates a distributed heating system driven by geothermal heat pumps (GHP-DH system) to sustainably mitigate frost heaving in a 20-meter-long section of a heavy-haul railway during seasonal freeze-thaw cycles. Field measurements were conducted to analyze key parameters, including the temperatures of the GHP-DH heat exchangers, subgrade soil temperature fields (T_S), the depth of the freezing front (d_FF), and track deformation due to frost heaving (D_T). The results demonstrated that the GHP-DH system maintained a stable heat supply above 50 °C, effectively reducing the frozen domain and extreme T_S fluctuations within the subgrade. The system reduced the maximum d_FF from 197 cm to 88 cm, ensuring the freezing front remained above the shallowest depth for groundwater migration through capillary action. Additionally, inclining the heat-supply pipes at a 3° angle minimized the transverse d_FF difference from 49 cm (unheated section) to 13 cm, significantly reducing horizontal track irregularities. Spacing the heat-supply pipes at 2.5 m further limited longitudinal d_FF differences to within 20 cm, preventing shortwave vertical track irregularities. In the unheated section, maximum D_T exceeded 9.4 mm, whereas the heated section maintained D_T fluctuations between –3 mm and +3 mm, well within the specified maintenance standards. These findings confirm that the GHP-DH system is a highly effective and sustainable solution for frost heave mitigation in railway subgrades, offering significant potential for improving track stability and reducing maintenance demands in cold climates.

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引用次数: 0

Investigation on the breakdown characteristic and crack extension mechanism of heat-treated granite under cycle hydraulic fracturing

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-24 DOI: 10.1016/j.geothermics.2024.103247

Hao Dai, Tubing Yin, You Wu, Jiexin Ma, Yongjun Chen, Xibing Li

To address the lack of research on breakdown characteristics of heat-treated rock under cyclic hydraulic fracturing (CHF). In this study, the breakdown mechanism and crack characteristics of heat-treated granite under CHF are investigated using a combination of experimental research and numerical simulation methods. CHF induces specimen fatigue and increases the number of hydraulic fracture branches on specimen surfaces compared to traditional hydraulic fracturing (THF). With the elevation of heat treatment temperature, the hydraulic fracture network on the surface of CHF samples becomes increasingly intricate, accompanied by a rise in hydraulic surface micro-cracks and roughness. CHF effectively reduces accumulated AE energy during the fracturing process by converting high-energy AE events into numerous smaller, low-energy events compared to THF at the same heat treatment temperature. Under CHF, both peak AE amplitude and cumulative AE energy decrease with increasing heat treatment temperature. The rupture of heat-treated granite under CHF is influenced by the coupled effects of thermal stress and alternating pore pressure.

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引用次数: 0

Geochemical study of fluid origin and caprock formation with carbonate mineral precipitation in the Okuaizu geothermal area

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-19 DOI: 10.1016/j.geothermics.2024.103242

Dongyang Mao , Jing Zhang , Yukiko Hoshino , Sakurako Satake , Heejun Yang , Hideki Kuramitz , Akira Ueda , Amane Terai

To elucidate the origin and mechanism of carbonate mineral precipitation controlling fluid movement in geothermal active areas, analyses were conducted in the Okuaizu geothermal area (with a maximum temperature of 340 °C). Carbon and oxygen isotopes and chemical compositions were analyzed for carbonate minerals in rocks from four newly drilled geothermal wells and one existing well. Carbon content in the rocks increased gradually from 200 to 500 m above sea level (mASL; above sea level), sharply increasing to a maximum of 3 wt% near the study area's center. Stable isotope composition data were combined with well temperature data to compute oxygen and carbon isotope compositions of the fluids. Results suggest that the fluids precipitating carbonate minerals originate from a mixture of meteoric water, fossil seawater, and magmatic fluids at depths <−500 mASL. Carbon primarily originates from shallow organic matter sources and deep magmatic CO₂. The caprock formation in the Okuaizu geothermal area occurs at shallow depths, with temperatures ranging from 100 °C to 150 °C, and comprises carbonate and clay minerals. This indicates that conditions conducive to CO₂ interaction with rocks and subsequent fixation as carbonate minerals in the formation develop at relatively low temperatures and shallow depths.

{"title":"Geochemical study of fluid origin and caprock formation with carbonate mineral precipitation in the Okuaizu geothermal area","authors":"Dongyang Mao , Jing Zhang , Yukiko Hoshino , Sakurako Satake , Heejun Yang , Hideki Kuramitz , Akira Ueda , Amane Terai","doi":"10.1016/j.geothermics.2024.103242","DOIUrl":"10.1016/j.geothermics.2024.103242","url":null,"abstract":"<div><div>To elucidate the origin and mechanism of carbonate mineral precipitation controlling fluid movement in geothermal active areas, analyses were conducted in the Okuaizu geothermal area (with a maximum temperature of 340 °C). Carbon and oxygen isotopes and chemical compositions were analyzed for carbonate minerals in rocks from four newly drilled geothermal wells and one existing well. Carbon content in the rocks increased gradually from 200 to 500 m above sea level (mASL; above sea level), sharply increasing to a maximum of 3 wt% near the study area's center. Stable isotope composition data were combined with well temperature data to compute oxygen and carbon isotope compositions of the fluids. Results suggest that the fluids precipitating carbonate minerals originate from a mixture of meteoric water, fossil seawater, and magmatic fluids at depths <−500 mASL. Carbon primarily originates from shallow organic matter sources and deep magmatic CO<sub>2</sub>. The caprock formation in the Okuaizu geothermal area occurs at shallow depths, with temperatures ranging from 100 °C to 150 °C, and comprises carbonate and clay minerals. This indicates that conditions conducive to CO<sub>2</sub> interaction with rocks and subsequent fixation as carbonate minerals in the formation develop at relatively low temperatures and shallow depths.</div></div>","PeriodicalId":55095,"journal":{"name":"Geothermics","volume":"127 ","pages":"Article 103242"},"PeriodicalIF":3.5,"publicationDate":"2024-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143148212","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}

引用次数: 0

Geothermal energy application for greenhouse microclimate management: A review

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-18 DOI: 10.1016/j.geothermics.2024.103209

T.M. Abir Ahsan , Md. Sazan Rahman , Md. Shamim Ahamed

Greenhouses offer an effective approach to enhance food production by extending growing seasons and optimizing plant conditions, yet their dependency on fossil fuels presents sustainability challenges. Geothermal energy provides a viable alternative for greenhouse climate control, with technologies utilizing both shallow and deep-ground resources to meet heating and cooling demands sustainably. This study comprehensively explores the applications and benefits of geothermal energy application in greenhouse climate management. It has been observed that deep geothermal sources present an efficient and eco-friendly solution, reducing fuel costs by up to 80%. Shallow systems, such as Earth-to-Air Heat Exchangers (EAHE), efficiently regulate temperatures in moderate climates while consuming only 8%–20% of the supplied thermal energy. Integrating EAHE with solar PV systems has shown potential for near self-sufficiency. For high-tech greenhouses, Ground Source Heat Pumps (GSHPs) achieve substantial energy savings (21%–40%) over traditional systems and reduce

{CO}_{2}

emissions by up to 50%. However, challenges persist, particularly with high capital cost and ground thermal imbalance. Finally, this study identifies key areas for future research, addressing these challenges to further geothermal technology development and close existing knowledge gaps, advancing sustainable greenhouse practices worldwide.

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引用次数: 0

Optimizing inhibitor injection in geothermal wells with electrical submersible pump

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-18 DOI: 10.1016/j.geothermics.2024.103238

Hakki Aydin , Seray Işık Tezel , Selcuk Erol

Electrical submersible pump (ESP) is a reliable artificial lift method to extend productive lifespan of geothermal wells. In the geothermal industry a common practice involves installing ESPs below the well's flashing depth. This placement approach aims to mitigate the risk of mineral precipitation, which can occur when hot geothermal fluids transition to a two-phase state (liquid and vapor) as pressure decreases. Positioning the pump below the flashing depth also prevents pump's underloading and gas cavitation. The inhibitor injection line usually integrated around the ESP string and installed downstream of the ESP motor. However, this standard practice introduces a challenge regarding inhibitor performance. While this placement ensures effective distribution of inhibitors throughout the production flow, the extended travel time from the surface to the point of application at the ESP can diminish inhibitor effectiveness due to continuous exposure to high temperatures throughout the wellbore. This study proposes relocating the inhibitor injection point within the production tubing closer to the flashing depth. This reduces inhibitor travel time from 108 min to 48 min and has the potential to significantly improve inhibitor effectiveness. Consequently, the implementation of capillary tubing is anticipated to yield annual cost savings per wellbore of approximately USD 10,000, coupled with the mitigation of mineral deposits within the studied well equipped with ESP. To evaluate this approach, a wellbore simulation tool and PHREEQC were employed to dynamically model the pressure and temperature profiles alongside the geochemical evolution of the produced fluids in the wellbore. This modeling approach offers significant value by potentially enabling the optimization of inhibitor usage and reducing the length of required inhibitor injection line.

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引用次数: 0

A shallow machine learning method based on geothermal drilling data: A case study of well 58–32 at the U.S. FORGE site

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-16 DOI: 10.1016/j.geothermics.2024.103239

Wangyuyang Zhai , Bo Feng , Suzhe Liu , Zilong Jia , Zhenjiao Jiang , Zheng Liu , Jichu Zhao , Xiaofei Duan

Enhanced geothermal system (EGS) development relies on efficient drilling methods. Traditional physics-driven numerical simulation models, while effective, are computationally demanding due to the complexity of deep reservoir conditions. In contrast, data-driven models offer a simpler approach by deriving statistical features from training data to create predictive models. This study utilizes diagnostic drilling data from the U.S. FORGE site to train Back Propagation neural network (BPNN) and Random Forest regressor models. The Random Forest model, with a training time of 4.981 s, achieves a test R2 of 0.9995, surpassing the BPNN in computational efficiency by 91.82 % and accuracy by 1.04 %. By effectively explaining 99.95 % of drilling depth values using features such as maximum rate of penetration (ROP), pump pressure, torque, and flow in, the model demonstrates the potential of shallow machine learning on extensive datasets in geothermal energy development. This research not only validates the efficacy of data-driven models in optimizing drilling performance but also highlights their role in cost reduction for future drilling projects. The findings present valuable insights for the geothermal industry, paving the way for enhanced drilling strategies and improved resource management.

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引用次数: 0

A pilot borehole heat exchanger field in Egypt: Subsoil investigation, thermal response tests and sensitivity analysis

IF 3.5 2区工程技术 Q3 ENERGY & FUELS

Geothermics

Pub Date : 2024-12-14 DOI: 10.1016/j.geothermics.2024.103241

Khaled Abdelghafar , Francesco Tinti , Mohamed Ismael , Hany Helal , Mohamed Elkarmoty

Information regarding the shallow geothermal energy potential is lacking in Egypt. Few studies were conducted to study the applicability of shallow geothermal energy in such hot and dry areas. In Cairo, a site investigation was carried out to provide insight into using shallow geothermal energy for cooling, for the first time in Egypt by collecting the ground's geological and thermal properties. A 40-m deep exploratory borehole (piezometer) was drilled at Cairo University- Faculty of Engineering (CUFE), Egypt. A shallow geothermal pilot plant at CUFE was designed and installed with the aid of data gathered during this initial phase. Second, three borehole heat exchangers (BHEs) underwent thermal response tests (TRT) to obtain the equivalent thermal properties of the ground. Data collected from both phases were compared to assess the importance of carrying out TRT and its effect on the accuracy of BHE sizing. TRT resulted in 20.47 % and 4.15 % higher values of the ground thermal conductivity and the undisturbed ground temperature (UGT) respectively. A sensitivity analysis was carried out to test the most effective factors on borehole sizing. UGT, building thermal load, BHE configuration, and ground thermal conductivity had the greatest effect. The results of the sensitivity analysis were significantly impacted by the project scale with increasing thermal loads. Several parameters had a greater impact at larger-scale projects. According to the results, using TRT to accurately determine the ground thermal properties saved several drilling depths.

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引用次数: 0