Journal of Groundwater Science and Engineering

Hydrogeochemical characteristics of hot springs exposed from fault zones in western Guangdong and their 14C age correction

WANG Hua, MAO Xu-mei, WANG Tao, FENG Liang, LIANG Li-li, ZHU Dong-bo, YANG Kai-ming

2019, 7(1): 1-14.

Abstract(657) PDF(384)

Abstract:
Hot springs are natural exposed points of the hydrothermal system. The hydro-geochemistry of hot springs can be used to interpret the formation of the hydrothermal system; and the 14C dating can be used to evaluate the renewability of the hydrothermal system. The hot springs exposed from fault zones in western Guangdong are classified as granite fissure water and clastic rock fissure water, which are sampled and tested. The results of water chemistry analysis show that hot spring water is mainly HCO3-Na type in the beginning, while the mixing of seawater leads to the increase of Cl-. Hydrogen and oxygen isotopes indicate that these hot springs mainly come from atmospheric precipitation, and water-rock interactions produce oxygen isotope exchange reactions, where a significant “oxygen drift” phenomenon can be observed. The relationship between δ13C and HCO3- indicates that there is a deep source of CO2 “dead carbon” in hot spring water. This systematic error is not considered in the existing 14C dating correction models. The 14C age of the deep source “dead carbon” correction proposed in this paper is close to the 14C age of the reverse chemical simulation correction, the Gonfiantinie model, and the Mook model. The deep source “dead carbon” correction method can improve the systematic error. Therefore, the 14C age corrected by the deep source “dead carbon” may be more representative in terms of the actual age of geothermal water.

Causes of geothermal fields and characteristics of ground temperature fields in China

MAO Xiao-ping, LI Ke-wen, WANG Xin-wei

2019, 7(1): 15-28.

Abstract(579) PDF(373)

Abstract:
There are many arguments on energy sources and main controlling factors of geothermal fields, so a systematic study on the distribution of ground temperature fields shall be necessary. In this paper the thermal conduction forward method of geothermal field is used to simulate cooling rate of abnormal heat sources and heat transfer of the paleo-uplift model. Combined with a large number of geothermal field exploration cases and oil exploration well temperature curves of domestic and foreign, the following conclusions are drawn: (1) According to the magmatic activity time, the magmatism activities are divided into two categories: Magma active areas (activity time < 500 000 years) and weak/magma inactive areas (activity time > 500 000 years). The latter has a fast cooling rate (the cooling time of the magma pocket buried around 10 km is less than 200 000 years) after it has intruded into the shallow layer and it has no direct contribution to modern geothermal fields; (2) China belongs to a weak/magma inactive area such as Tengchong region and Qinghai-Tibet region because the chronological data of these regions show that its magma activity time is more than 500 000 years; (3) The temperature of most geothermal fields can be obviously divided into three segments in the vertical direction: A high geothermal gradient segment (Segment H) at the surface, then a low geothermal gradient segment (Segment L) at a secondary depth, and finally a lower temperature segment (Segment D) at a deeper depth. The temperature isoline presents a mirror reflection relation on the temperature profile, indicating that geothermal field is dominated by heat conduction, rather than having an abnormally high temperature “heat source” to provide heat; (4) Near-surface (0-5 km) materials’ lateral heterogeneity caused by tectonic movement shall probably be the main controlling factor of ground temperature fields.

Discussion on evaluation methodology of hydrothermal geothermal reservoir

FENG Jian-yun, ZHANG Ying, HE Zhi-liang, SUN Zi-ming, LUO Jun

2019, 7(1): 29-41.

Abstract(469) PDF(247)

Abstract:
Geothermal reservoir are the vehicle of geothermal resources and their occurrence as well as the storage mass. Precise description and evaluation of geothermal reservoir serves to be the cornerstone of geothermal resource exploration and exploitation. Based on the principles and basic train of geothermal reservoir evaluation, in this work, the content of geothermal reservoir evaluation was determined and the value range of geothermal reservoir evaluation parameters was discussed in combination with the actual production data of two types of geothermal reservoir in North China: The Neogene Guantao Formation sandstone pore-type geothermal reservoir, and the Cambrian-Ordovician and Middle Proterozoic Jixian carbonate karst-fissure-type geothermal reservoir. An evaluation method for the sandstone pore-type and the carbonate karst-fissure-type geothermal reservoir is finally established based on the analysis of the production data, i.e. the values of geothermal reservoir temperature, geothermal fluid production, reinjection, physical properties and other parameters are assigned, and the geometric average value of the assigned values for the above-mentioned parameters is taken as the overall evaluation index of geothermal reservoir. From large to small, this index categorizes geothermal reservoir into three grades: I, II and III, which corresponds to advantageous, moderate advantageous and disadvantageous geothermal reservoir respectively. The geothermal reservoir of the same grade are further classified in light of the index value, thus realizing the comprehensive evaluation of geothermal reservoir.

Research on basic characteristics of 2H, 18O and 14C in geothermal fluid in Guangdong Province, China

ZENG Tu-rong

2019, 7(1): 42-52.

Abstract(680) PDF(236)

Abstract:
In general, previous geothermal geochemical studies in Guangdong Province mainly involves single method to cover limited aspects and areas. In that way, various methods available cannot actually provide more convincing results of geothermal fluid’s circulation system and evolution process from different dimensions, especially in terms of isotope. As a result, more comprehensive researches remain to be done on geochemistry of geothermal fluid, in particular, the space-time law of isotope’s evolution pattern as well as recharge cycle. Based on data of environmental isotopes (2H and 18O) and the isotope of radiometric dating (14C), geothermal geology, characteristics of groundwater flow field and types of goethermal reservior in Guangdong Province are taken into account in this paper, so as to analyze numerical rule and spatial distribution features of isotopes. Thus, corresponding main causes, mechanism and hydrogeological significance can be revealed to further study the potential of geothermal fluid to renew and recharge in the long run, which is conducive to enrich geothermal theories and solve existing hydrogeological problems.

Geological characteristics and analysis of hydrothermal genesis in the Suijiang-1 well in Yunnan Province, China

SHU Qin-feng, WEI Liang-shuai, LI Xiao

2019, 7(1): 53-60.

Abstract(335) PDF(249)

Abstract:
The geothermal water hydrochemistry and isotopic characteristics of boreholes in the Suijiang-1 well in Yunnan Province were studied based on the actual drilling geology, regional geological structure and hydrogeological conditions. The analysis results show that the geothermal water is SO4-Ca?Mg type, the recharge elevation is 1 381-1 646 m, the recharge source is atmospheric precipitation, the geothermal reservoir temperature is 42-45 ℃, and the geothermal water is controlled by lithology and geological structure conditions of study area. Atmospheric precipitation enters the groundwater circulation system through the surface karst form of the Wujiaobao anticline, northwest-southeast tensile faults, fissures and karst depression, and geothermal water formed through the rising deep cycle water temperature, then blocked by the double rivers’ fault zone and drilling explosion.

Geothermal resources formation conditions and preferred target areas in a certain county of Western Sichuan,China

LI Jun-ya, WANG Yu-jue, HE Xue-wen, XUE Guo-dong, XU Huan, TIAN Yan-hong, ZHAO Li-li, CUI Qi-hang

2019, 7(1): 61-69.

Abstract(427) PDF(230)

Abstract:
The geothermal resource is a form of “green” and renewable energy with huge development potential in terms of both environmental protection and economy. It was concluded that the exposed hot springs were mostly produced when fluids derived from atmospheric precipitation were heated deep and recurrently under the ground, developed banded geothermal reservoir in the pores of fault damage zones, fissure zones, hornification zones and dikes, and then moved upward with analyzing the geological and hydrogeological data as well as hydrochemical types of the naturally exposed hot springs in the studied region so as to ascertain the accumulation conditions of geothermal resources in a particular county in Western Sichuan and opt for suitable target areas for exploring geothermal resources. Four areas where geothermal resources are potentially located were proposed with analysis of their formation conditions based on this notion, and the “epsilon-shaped” structure in Zhimulin, the “epsilon-shaped” structure in Jiaochang, the vortex structure in Rewugou and the arcuate structure in Shidaguan were analyzed in this paper offering a reference for developing and exploiting the geothermal resources in the region as well as studying the development patterns of other hot springs in this region.

Analysis of occurrence characteristics of geothermal resources and its relation to control structures in Zibo City,China

TAN Xiao-bo, WEI Shan-ming, BO Ben-yu, JIANG Dian-qing

2019, 7(1): 70-76.

Abstract(395) PDF(269)

Abstract:
According to the geothermal geological conditions, the geothermal resources in Zibo can be divided into sedimentary basin type and tectonic basin type. The main thermal reservoirs of sedimentary basin type are the Neogene Guantao Formation and the Paleogene Dongying Formation.The thermal reservoirs of tectonic basin type are mainly the Ordovician Majiagou Group. The characteristics of reservoir, cap, pass and source of thermal resource types in different areas are elaborated. Based on the analysis of the well-forming conditions of the existing geothermal wells in the area, combined with the geothermal anomaly areas and hydrogeochemistry, it was discovered that the fault structures in the area, especially the deep faults such as Yuwangshan fault, Wangmushan fault, Zhangdian fault and Chaomizhuang graben, play an important role in controlling the occurrence and distribution of tectonic basin-type geothermal resources in Zibo City.

Characteristics of shallow geothermal fields in major cities of Tibet Autonomous Region

YANG Hai-jun, DONG Jian-xing, SUN Dong, HUANG Rui

2019, 7(1): 77-85.

Abstract(305) PDF(148)

Abstract:
Based on the project titled “Investigation and evaluation of shallow geothermal energy in major cities of Tibet Autonomous Region”, the distribution characteristics and occurrence conditions of shallow geothermal fields in these cities were introduced in this paper. To this end, relevant data in Lhasa, Shigatse and Nyingchi Cities through vertical thermometry was a focus, so as to analyze groundwater temperature and the distribution law of strata with constant temperature. Then through comprehensive comparisons and analysis of the relationship between groundwater temperature and climate, differences in this aspect of Nagqu City were taken as a typical case to clarify formation of geothermal field and corresponding influence on groundwater temperature, furthermore providing basic data for rational development and utilization of shallow geothermal energy in Tibet Autonomous Region.

Discussion on establishing monitoring networks for temperature fields of shallow thermal energy in Shandong, China

ZHOU Bo, WEI Shan-ming, WANG Tao, NIE Yu-peng, WANG Chuan-qi

2019, 7(1): 86-93.

Abstract(458) PDF(219)

Abstract:
In the recent decade, the construction projects related to shallow geothermal energy engineering have undergone rapid development in Shandong Province. The predominant type of these developments and applications was heat exchange through buried tubes and the main targets were residential and office buildings. However, an overwhelming majority of the completed geothermal heat pump projects lacked monitoring devices so that they were unable to comprehensively reflect the background values for the geothermal fields within the province and few researches were conducted on their influence on the geological environment. In this paper, locations for monitoring shallow geothermal energy and their validity of the monitoring point deployment were studied in view of the development and application status as well as geological background conditions of various projects located in multiple cities providing data support for analyzing the fluctuation trend and influence of large-scale shallow geothermal energy applications on the shallow geothermal and the feasibility and parameter designs of newly built systems in Shandong Province in the future.

2019 Vol. 7, No. 1

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