geothermal field
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Geothermics ◽  
2022 ◽  
Vol 100 ◽  
pp. 102323
Author(s):  
Ji Luo ◽  
Yiman Li ◽  
Jiao Tian ◽  
Yuanzhi Cheng ◽  
Zhonghe Pang ◽  
...  

Geothermics ◽  
2022 ◽  
Vol 100 ◽  
pp. 102316
Author(s):  
Kazuya Ishitsuka ◽  
Yusuke Yamaya ◽  
Norihiro Watanabe ◽  
Yosuke Kobayashi ◽  
Toru Mogi ◽  
...  

2022 ◽  
Vol 579 ◽  
pp. 117335
Author(s):  
Wei Wang ◽  
Peter M. Shearer ◽  
John E. Vidale ◽  
Xiaohua Xu ◽  
Daniel T. Trugman ◽  
...  

2022 ◽  
Vol 9 ◽  
Author(s):  
Yifan Fan ◽  
Shikuan Zhang ◽  
Yonghui Huang ◽  
Zhonghe Pang ◽  
Hongyan Li

Recoverable geothermal resources are very important for geothermal development and utilization. Generally, the recovery factor is a measure of available geothermal resources in a geothermal field. However, it has been a pre-determined ratio in practice and sustainable utilization of geothermal resources was not considered in the previous calculation of recoverable resources. In this work, we have attempted to develop a method to calculate recoverable geothermal resources based on a numerical thermo-hydraulic coupled modeling of a geothermal reservoir under exploitation, with an assumption of sustainability. Taking a geothermal reservoir as an example, we demonstrate the effectiveness of the method. The recoverable geothermal resources are 6.85 × 1018 J assuming a lifetime of 100 years in a well doublet pattern for geothermal heating. We further discuss the influence of well spacing on the recoverable resources. It is found that 600 m is the optimal well spacing with maximum extracted energy that conforms to the limit of the pressure drop and no temperature drop in the production well. Under the uniform well distribution pattern for sustainable exploitation, the recovery factor is 26.2%, which is higher than the previous value of 15% when depending only on lithology. The proposed method for calculating the recoverable geothermal resources is instructive for making decisions for sustainable exploitation.


Water ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 97
Author(s):  
Ching-Huei Kuo ◽  
Pi-Yi Li ◽  
Jun-Yi Lin ◽  
Yi-Lin Chen

This paper presents a water circulation model by combing oxygen and hydrogen stable isotopes and mean residence time (MRT) estimation in a high-temperature metamorphic geothermal field, Tuchen, in Yilan, Taiwan. A total of 18 months of oxygen and hydrogen stable isotopes of surface water and thermal water show the same variation pattern, heavier values in summer and lighter values in the rest of the year. A shift of δ18O with a relative constant δD indicates the slow fluid–rock interaction process in the study area. Two adjacent watersheds, the Tianguer River and Duowang River, exhibit different isotopic values and imply different recharge altitudes. The seasonal variation enabled us to use stable isotope to estimate mean residence time of groundwater in the study area. Two wells, 160 m and 2200 m deep, were used to estimate mean residence time of the groundwater. Deep circulation recharges from higher elevations, with lighter isotopic values, 5.9‰ and 64‰ of δ18O and δD, and a longer mean residence time, 1148 days, while the shallow circulation comes from another source with heavier values, 5.7‰ and 54.4‰ of δ18O and δD, and a shorter mean residence time, 150 days. A two-circulation model was established based on temporal and spatial distribution characteristics of stable isotopes and the assistance of MRT. This study demonstrates the usefulness of the combined usage for further understanding water circulation of other various temperatures of metamorphic geothermalfields.


2022 ◽  
Vol 14 (1) ◽  
pp. 185
Author(s):  
Hilary Chang ◽  
Nori Nakata

Distributed acoustic sensing (DAS) has great potential for monitoring natural-resource reservoirs and borehole conditions. However, the large volume of data and complicated wavefield add challenges to processing and interpretation. In this study, we demonstrate that seismic interferometry based on deconvolution is a convenient tool for analyzing this complicated wavefield. We also show the limitation of this technique, in that it still requires good coupling to extract the signal of interest. We extract coherent waves from the observation of a borehole DAS system at the Brady geothermal field in Nevada. The extracted waves are cable or casing ringing that reverberate within a depth interval. These ringing phenomena are frequently observed in the vertical borehole DAS data. The deconvolution method allows us to examine the wavefield at different boundary conditions and separate the direct waves and the multiples. With these benefits, we can interpret the wavefields using a simple 1D string model and monitor its temporal changes. The velocity of this wave varies with depth, observation time, temperature, and pressure. We find the velocity is sensitive to disturbances in the borehole related to increasing operation intensity. The velocity decreases with rising temperature. The reverberation can be decomposed into distinct vibration modes in the spectrum. We find that the wave is dispersive and the fundamental mode propagates with a large velocity. This interferometry method can be useful for monitoring borehole conditions or reservoir property changes using densely-sampled DAS data.


Author(s):  
Hilary Chang ◽  
Nori Nakata

The distributed acoustic sensing (DAS) has great potential for monitoring natural-resource reservoirs and borehole conditions. However, the large volume of data and complicated wavefield add challenges to processing and interpretation. In this study, we demonstrate that seismic interferometry based on deconvolution is a convenient tool for analyzing this complicated wavefield. We extract coherent wave from the observation of a borehole DAS system at the Brady geothermal field in Nevada. Then, we analyze the coherent reverberating waves, which are used for monitoring temporal changes of the system. These reverberations are tirelessly observed in the vertical borehole DAS data due to cable or casing ringing. The deconvolution method allows us to examine the wavefield at different boundary conditions. We interpret the deconvolved wavefields using a simple 1D string model. The velocity of this wave varies with depth, observation time, temperature, and pressure. We find the velocity is sensitive to disturbances in the borehole related to increasing operation intensity. The velocity decreases with rising temperature, which potentially suggests that the DAS cable or the casing are subjected to high temperature. This reverberation can be decomposed into distinct vibration modes in the spectrum. We find that the wave is dispersive, and the the fundamental mode propagate with a large velocity. The method can be useful for monitoring borehole conditions or reservoir property changes. For the later, we need better coupling than through only friction in the vertical borehole to obtain coherent energy from the formation.


2021 ◽  
Vol 9 ◽  
Author(s):  
Yanyan Li ◽  
Ji Dor ◽  
Chengjiang Zhang ◽  
Guiling Wang ◽  
Baojian Zhang ◽  
...  

The Xifeng geothermal field is located in the Yangtze Craton, SW China, and is one of the most representative low-temperature geothermal fields in China. Widespread thermal anomalies, hot springs, and geothermal wells have been reported by previous studies. However, the nature and forming mechanisms of the field remain poorly understood. Element geochemical (ions, rare earth elements) and stable isotopic (D, O) composition of hot springs, geothermal fluids, rivers, and cold springs from different locations of the Xifeng geothermal field were analyzed in this study. The ions studies revealed that most samples featured the Ca-Mg-HCO3 type, except Xifeng hot springs, and which were characterized by the Ca-Mg-HCO3-SO4 type. Based on quartz geothermometers, the estimated reservoir temperature was 77°C. The results of stable isotopes (D, O) manifest that the Xifeng geothermal system was recharged by meteoric water at an elevation of 1,583 m from SW to NE. The research of rare earth elements (REE) revealed that their accumulation characteristics and obvious positive Eu anomaly were inherited from host feldspar-bearing reservoir dolomites through water-rock interactions. Combined with these observations, geological setting, and previous studies, it was concluded that the formation of the Xifeng geothermal field resulted from recharge, deep circulation, and secondary rising of the meteoric water along the faults. First, meteoric water infiltrated to depth through faults and crack zones. Second, the deep-infiltrated water was heated by radioactive heat, deep heat, and tectonic frictional heat. Finally, as the warmed-up waters underwent considerable deep circulation in the reservoir, it rose again along the main faults, and mixed with groundwater near the surface. Taken together, we suggest that the Xifeng geothermal system should be assigned as a faults-controlling, and deeply circulating meteoric water of low-temperature category.


2021 ◽  
Author(s):  
◽  
Gabriel Matson

<p>The high-temperature, fluid-dominated Ngatamariki geothermal field is located in the central Taupo Volcanic Zone, North Island, New Zealand, and is used to generate electricity via an 82 MW power plant. Injection wells have been in operation since June 2012. During June and July 2012, injection well NM8 was injected with with cold water in order to improve reservoir permeability. Geothermal stimulation and production may trigger microearthquakes by fluid flow through the reservoir. Close clustering of microseismic events’ hypocentres relative to the source-receiver distance results in many events having similar waveforms. We capitalize on this relationship by using a matched-filter detection method in which high-quality seismograms corresponding to a well-recorded earthquake (“templates”) are cross-correlated against continuous data to reveal additional earthquakes with similar characteristics. Clustering of the detections’ hypocenters also implies that small variations in travel times between two events corresponds to small differences in hypocentral locations, which is the foundation of the double-difference relocation method.  Using an 11 station seismic network, we detect 863 events via cross-correlation of 110 matched-filter templates during the two months stimulation testing. We locate each of these detections using a double-difference relocation method by which events are relocated based on relative travel times. The locatable seismicity delineates: a northern Ngatamariki cluster, a southern Ngatamariki cluster, and a cluster to the south, at the neighboring Rotokawa field. Seismicity in the northern Ngatamariki cluster (522 events) is of greatest interest for this project due to its proximity to well NM8 and temporal signature relative to injection. The seismicity cluster centers around well NM8 at a depth of 2.1 km below sea level. Events in this cluster extend to up to 2.5 km from the injection well. An increase in seismicity near NM8 lags behind the onset of injection by 4–8 days. In contrast, a seismicity-rate decrease coincides with injection shut-in without any time lag. Local magnitudes in this cluster span the range −0.09 ≤ Ml ≤ 1.66 with a completeness magnitude of 0.25. Seismicity within 200 m of NM8 is induced by thermal stresses caused by the difference in temperature between the injectate and the reservoir. Seismicity further than 200 m, but still within this cluster, from NM8 is induced via pore fluid pressure increases from the injected fluid. The coupled mechanism acts on two different length scales and is known as a thermoporoelastic mechanism. The matched-filter detection of microseismic events allows interpretation of extent of injection well stimulation and the relationship between injection and seismicity.</p>


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