Subducted remnant slabs play an important role in the geodynamics and evolution of the Earth, but their behaviour in the mantle is not well understood. Terrestrial heat flow and thermal lithosphere ...structure provide crucial constraints on lithospheric dynamics. Based on whole‐well steady‐state temperature logs and conductivity measurements of core samples from a scientific borehole, we obtained a new high‐quality terrestrial heat flow values for East Asia. The heat flow was calculated at 60.6 ± 16.0 mW/m2 with a high crust/mantle heat flow ratio of 1.41, suggesting a hot‐crust‐cold‐mantle lithospheric structure. The thermal lithospheric thickness of eastern Fujian is estimated to be 152–166 km, indicating a thick and cold lithosphere. We demonstrate that the cooling of the lithosphere is caused by a remnant palaeo‐slab of the Palaeo‐Pacific plate subducted beneath SE China. The remnant slab blocked heat convection into the bottom of the lithosphere of the Eurasian Plate.
•Development of a comprehensive methodology to assess the risk of earthquakes induced by hot dry rock mining.•Build DFN and hydro-thermal coupled numerical models.•The magnitude of earthquakes during ...hydraulic fracturing is generally less than 2.0.•The maximum earthquake magnitude during a 30-year development period is less than 1.28.
Earthquakes induced during hot dry rock (HDR) geothermal development have attracted extensive attention and constrained the further exploitation of HDR resources. Seismic risk evaluation of HDR projects is essential. The first HDR demonstration project in China is located in the Gonghe Basin in Qinghai. The EGS (enhanced geothermal systems) site is located near Gonghe County and is very seismically sensitive. The seismic risk induced by hydraulic fracturing and long-term cycling during the HDR development process was evaluated using a multi-field coupling method based on analysis of the geothermal geological conditions, ground stress, and natural fracture characteristics. During hydraulic fracturing, the predicted magnitude of earthquake events is generally below 2.0, with a range of 0.7–1.3. During a 30-year development period, the predicted maximum earthquake magnitude is less than 1.28. The HDR development will not have an impact on the local geological safety. Considering the uncertainty of the geology, a further discussion of measures to reduce the risk of earthquakes is presented. An entire induced seismic risk evaluation process method is developed, which can provide a reference for related research.
Southeastern China (SE China) is located in the Pacific tectonic domain and has experienced a series of tectonomagmatic events induced by the subduction of the Paleo‐Pacific Plate since the late ...Mesozoic. The subduction formed a series of NE‐NNE oriented faults under a NW–SE regional stress field, along which a number of thermal springs occur. Previous studies have focused on the genesis mechanism of specific geothermal fields in SE China, but the general characteristics of hydrothermal systems in SE China remains unclear. In this study, we investigate the correlation between geothermal activity, hydrochemical type and regional faults by studying the distribution of hydrothermal activity and geochemical properties of typical hydrothermal systems in SE China. The hydrothermal systems in SE China have a crustal thermally‐dominated structural origin unique to the specific geological and tectonic conditions of the Eurasian Plate margin. The upwelling of the asthenosphere and the widespread granitoids with high radiogenic heat production in SE China provide major heat sources for regional geothermal anomalies. The NE‐oriented crustal thermally‐dominated faults are critical for the formation of geothermal anomalies and NW‐oriented extensional faults have created favorable conditions for meteoric water infiltration, transportation and the formation of thermal springs.
Clogging is one of the most important factors that restricts the development and popularization of artificial groundwater recharge technology. Gas clogging is an important but often overlooked form ...of clogging. In this study, a high-speed image acquisition system was used to obtain high-resolution images of the migration of water and gas in the pore. The bypass flow, trapped bubbles in the H-shaped pore channel, blind end, and corner of the pore were directly observed and their clogging mechanisms were analyzed. The influences of the pore structure and gas content on the degree of gas clogging were quantified. The pore–throat size has a certain controlling effect on the movement of the gas and liquid phases. As the diameter of the pore–throat increases, the clogging effect of the gas decreases, and the relative permeability of the water (krw) increases. The pore–throat ratio exhibits a negative correlation with the relative permeability of the liquid phase, and the pore–throat sorting coefficient exhibits a positive correlation with krw. As the gas content increases, the degree of gas clogging increases, and the effect is more significant at low gas-to-liquid ratios (<1:2). These results provide theoretical support for the scientific quantitative evaluation and prediction of the occurrence of gas clogging in groundwater recharge projects.
To determine the main hydrogeochemical processes affecting the migration and enrichment of arsenic in the high arsenic geothermal water in the Batang area of Sichuan Province, the hydrogeochemistry ...and whole rock geochemistry of groundwater and aquifer sediments were studied. The results show that the groundwater has an arsenic concentration of 3.1 to 80.8 μg L − 1, which is mainly present in the form of arsenate. The arsenic concentration in this groundwater system is correlated with the presence of fluoride ions and the temperature. The thermal storage temperature and cycling depth are significantly correlated with the arsenic concentration. The thermal storage temperature in the Batang area is relatively high (220 °C to 260 °C). When cold water mixing takes place, the temperature falls to 76.56–177.51 °C, the proportion of cold water mixing ranges from 67% to 79%, and the circulation depth reaches 1318.11 to 3443.37 m. The temperature of the groundwater, the competitive adsorption of HCO3−, and the pH level also affect the arsenic concentration. The above results indicate that the alkaline reducing environment in the Batang area of Western Sichuan is beneficial to the enrichment of arsenic in the groundwater. The desorption of the arsenic adsorbed on the surface of Fe oxide/hydroxide minerals is the main route by which arsenic enters the geothermal water. These results provide guidance for the exploitation and utilization of geothermal water in the Batang area.
•Dear editor,•This is the highlight of my article.•Batang area in Western Sichuan is rich in geothermal resources, but the arsenic content of geothermal water exposed on the surface is high. This paper takes arsenic as the breakthrough point, analyzes the cause of formation of high arsenic geothermal water in Batang area of Western Sichuan from the cause of formation of arsenic in geothermal water, and comprehensively discusses the cause of formation of high arsenic geothermal water from the aspects of hydrochemical characteristics, sediment characteristics, heat storage temperature, circulation depth and cold water mixing in the study area, and finally obtains the geothermal genetic model of Batang area of Western Sichuan.•Best Regards.
There are abundant geothermal resources in the Xiong’an New Area, China. Drilling has revealed a greater potential in the deep Gaoyuzhuang geothermal reservoir. However, the reservoir required ...acidification to increase its water production. In this study, three types of core samples with different mineral compositions from different depths in the target boreholes were selected for acid rock reaction experiments at the temperature of 40 °C, 60 °C, 80 °C and 100 °C, and pressure of 30 MPa. The kinetics of the acid rock reaction of the major minerals were modeled based on the transitional state theory. The kinetic parameters were obtained by comparing the modelling and experimental results. The results show that the lithology of the Gaoyuzhuang reservoir is primarily dolomite. The dissolution ratio for 15 wt.% HCl reached 84.1% on average for the rock fragments. Temperature has a significant effect on the dissolution rate of the minerals. In the presence of HCl (acidic mechanism), the reaction rate constants of the dolomite, calcite and illite reached 2.4 × 10−4 mol/m2/s, 5.3 × 10−1 mol/m2/s and 9.5 × 10−2 mol/m2/s, respectively. The results of this study provide the basic parameters for the design and evaluation of field acidizing.
CO
2
is now considered as a novel heat transmission fluid to extract geothermal energy. It can achieve the goal of energy exploitation and CO
2
geological sequestration. Taking Zhacanggou as research ...area, a “Three-spot” well pattern (one injection with two production), “wellbore–reservoir” coupled model is built, and a constant injection rate is set up. A fully coupled wellbore–reservoir simulator—T2Well—is introduced to study the flow mechanism of CO
2
working as heat transmission fluid, the variance pattern of each physical field, the influence of CO
2
injection rate on heat extraction and the potential and sustainability of heat resource in Guide region. The density profile variance resulting from temperature differences of two wells can help the system achieve “self-circulation” by siphon phenomenon, which is more significant in higher injection rate cases. The density of CO
2
is under the effect of both pressure and temperature; moreover, it has a counter effect on temperature and pressure. The feedback makes the flow process in wellbore more complex. In low injection rate scenarios, the temperature has a dominating impact on the fluid density, while in high rate scenario, pressure plays a more important role. In most scenarios, it basically keeps stable during 30-year operation. The decline of production temperature is <5 °C. However, for some high injection rate cases (75 and 100 kg/s), due to the heat depletion in reservoir, there is a dramatic decline for production temperature and heat extraction rate. Therefore, a 50-kg/s CO
2
injection rate is more suitable for “Three-spot” well pattern in Guide region.
•Revealing the fractionation characteristics of rare earth elements in geothermal fluids.•The effect of temperature on rare earth elements during the deep circulation of geothermal fluids was ...studied.•The indicative significance of rare earth elements in geothermal systems was explored.
Geothermal resource development and utilization is one of the major energy issue worldwide. Many researches have been carried out about the geochemical characteristics and geological characteristics of high arsenic(As) geothermal fluids, but the content of rare earth elements(REEs) in high As geothermal fluids, there are still some questions that deserve to be discussed. For example, the content, fractionation characteristics, geochemical processes and indication of REEs in high As geothermal fluids are not well understood, which limits further research on chemical characteristics such as enrichment of REEs in geothermal fluids. In this study, based on field tests and laboratory analysis in the Batang area of western Sichuan, it was found that the overall content of REEs in high As geothermal fluids in the study area was low. After normalized the REEs in geothermal fluids with chondrite, it was found that the geothermal fluids were enriched in light REEs and depleted in heavy REEs. Meanwhile, the cold water mixing, pH, TDS, temperature and HCO3− concentration of the geothermal fluid extremely affect of ree partitioning on the rare earth element partitioning characteristics of the geothermal fluid, and both Ce and Eu show positive anomalies in the normalized model of REEs of the geothermal fluid. It is worth noting that the As concentration in the geothermal fluid gradually decreases as the Eu/Eu* value increases, and the As concentration in the geothermal fluid is more enriched when the Ce/Ce* value is in the range of 2–3. And it was found that the changes in pH, TDS, temperature, HCO3−, and redox environment in the geothermal fluid due to 67%∼79% cold water mixingunder the condition of the large cold water mixing ratio had a large impact on the fractionation characteristics of REEs. Therefore, the characteristic changes of Ce and Eu in a reduced geothermal fluid system may be indicative of As enrichment in geothermal fluids.
There are abundant geothermal resources in the Xiong’an New Area, China. However, the thermal state and geothermal energy accumulation mechanism are not clear. Based on the geological conditions and ...the characteristics of the present geothermal field, a 2D model was established to analyze the process of mantle-derived heat conduction and to predict the distribution of the deep geothermal field. We calculated the terrestrial heat flow for the Rongcheng uplift and Niutuozhen uplift to be 64 and 75 mW/m², respectively. The geothermal resources in this area are controlled by a four-element model comprising heat conduction, structural uplift, large deep fractures, and convection within the reservoir.
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