Geothermal Resources In China Research Articles

Deep geothermal resources in China: Potential, distribution, exploitation, and utilization

Deep geothermal resources mainly refer to the thermal energy stored in subsurface rocks and fluids therein at a depth of 3–10 km, which is a kind of renewable and sustainable clean energy unaffected by weather and seasonal changes. Large scale exploitation of the deep geothermal resources is of great significance to ensuring national energy security and achieving the “Carbon Peak and Carbon Neutrality”. Based on the latest terrestrial heat flow data, this paper estimated the potential of deep geothermal resources in the terrestrial areas of China, and the results show that the total amount of geothermal resources within 3–10 km under the Earth's surface in the terrestrial areas of China is 24.6 × 1015 GJ. In line with climate zones categorized, the geothermal resource proportion is 43.81% for severe cold regions, 29.19% for cold regions, 6.92% for mild regions, 13.82% for hot summer and cold winter regions, and 6.26% for hot summer and warm winter regions. Statistics according to the burial depth range reveal that the resources within depth ranges of 3–5 km, 5–7 km and 7–10 km under the Earth's surface are 4.3119 × 1015 GJ, 6.37674 × 1015 GJ and 13.89594 × 1015 GJ respectively, showing an increasing trend of geothermal potential with increasing burial depth. The deep geothermal resources are mainly of medium-to-high temperature reserves, and the energy supply strategy can be optimized by combining the climate conditions and population distribution, as well as considering power generation. In regions of cold or severe cold climate, the geothermal resources may be applied to geothermal power generation and district heating in combination; in regions of hot summer and cold winter or mild climates, the resources can be used for geothermal power generation combined with cooling and heating; in regions of hot summer and warm winter climates, the resources may be applied to geothermal power generation combined with cooling and industrial and agricultural utilization. Exploitation of deep geothermal resources also can be combined with carbon dioxide sequestration, multi-mineral resources extraction and energy storage to realize comprehensive exploitation and utilization of various energy resources. It is suggested that theoretical technology research should be combined with pilot tests and field demonstrations, and large-scale economic exploitation of deep geothermal resources should be arranged in a coordinated manner, following the principles of overall planning and step-by-step implementation.

A Study on the Acquisition Technology for Weak Seismic Signals from Deep Geothermal Reservoirs

There are rich geothermal resources in China and they are widely distributed. After years of continuous exploration and production, most of the shallow geothermal resources have been explored and the current exploration mainly focuses on deep ones. Among a great many geophysical exploration methods, seismic survey is the most effective means of geothermal resource exploration and production, but its weak seismic reflection signal, low S/N ratio and poor imaging of thermal reservoirs due to the seismic geological conditions restrict the production and utilization of deep geothermal resources. It considers through the analysis of the geophysical characteristics of the thermal reservoir that the main causes for the weak seismic reflection signals from deep thermal reservoirs are (1) the shielding effect of the strong wave impedance interface between the thermal reservoir and the caprocks; (2) the small reflection coefficient inside the thermal reservoir; and (3) the serious absorption and attenuation of high-temperature fluids such as hydrothermal fluids and steam in the thermal reservoirs by seismic waves. Accordingly, a series of seismic data acquisition technologies are proposed based on the high-precision vibroseis low-frequency shooting, high-sensitivity geophones long-spread receiving and small bin size highfold technologies, and their application in the seismic acquisition of dry-hot rocks (HDR) in Gonghe Basin, Qinghai, shows a very good application effect.

3-D Inversion of Gravity Data of the Central and Eastern Gonghe Basin for Geothermal Exploration

The Gonghe Basin is one of the most important regions for the exploration and development of hot dry rock geothermal resources in China. However, there is still some controversy about the main heat source of hot dry rock geothermal resources in the Gonghe Basin. Combined with previous research results including three-dimensional magnetotelluric imaging and linear inversion of Rayleigh wave group and phase velocity result, we obtained a high-resolution underground spatial density distribution model of the Gonghe Basin based on satellite gravity data by using 3-D gravity focusing inversion method. According to the results, there are widely distributed low density anomalies relative to surrounding rock in the middle crust of the study area. The low-density layer is speculated to be a low-velocity, high-conductivity partial melting layer in the crust of the Gonghe Basin. The inversion result confirms for the first time the existence of a partial melt layer from the gravity point of view, and this high temperature melt layer may be the main heat source of the hot dry rock geothermal resources in the Gonghe Basin. It can provide a new basis for further research on the genesis of the hot dry rock geothermal system in the Gonghe Basin.

Magmatic fluid input controlling the geochemical and isotopic characteristics of geothermal waters along the Yadong-Gulu rift, southern Tibetan Plateau

Geothermal resources, regarded as sustainable green energy, are attracting increasing attention. The southern Tibetan Plateau possesses the most abundant intermediate-high geothermal resources in China and has enormous potential for geothermal exploration. Geothermal waters from the Yadong-Gulu Rift (YGR), which is considered as the most active geothermal belt of the plateau, are studied based on hydrochemical and isotopic characteristics to understand the spatial variations of fluid origin, evolution, and circulation mechanism as well as heat sources. The hydrochemical characteristics of cold springs and surface waters are consistently characterized by Ca-HCO3 dominated (Ca-HCO3 and Ca-HCO3·SO4) waters while those of geothermal springs present extensive variability with Na-Cl dominated (Na-Cl·HCO3, Na-HCO3·Cl, Na·Ca-Cl·HCO3) and Na-HCO3 waters. The main geochemical processes controlling the geothermal springs are combinations of silicate weathering, carbonate dissolution, and cation exchange. The characteristics of trace alkali metals and B indicate they undergone common/similar deep process and the potential input of magmatic degassing. The δD and δ18O values suggest that cold springs and surface waters are recharged by meteoric water, and geothermal springs are replenished by meteoric water, snow-melt, and magmatic fluid. The mass balance model reveal that dominant carbon sources for geothermal waters can be deeply derived CO2 (i.e., magmatic source and metamorphic source), contributing from 77% to 99%. Based on empirical chemical geothermometers, Si-Enthalpy mixing model, and geothermometrical modelling, the calculated reservoir temperatures are highly variable (137-312 °C). The circulation depths of geothermal waters are 2.45-6.85 km. A conceptual model is proposed to reveal the deep groundwater circulation.

Characteristics of Radiogenic Heat Production of Widely Distributed Granitoids in Western Sichuan, Southeast Tibetan Plateau

Abstract Investigating the genesis of geothermal resources requires a thorough understanding of the heat source mechanism, which is also a vital basis for the efficient exploration and utilization of geothermal resources. Situated in the eastern Himalayan syntax, western Sichuan is considered to be one of the main concentration regions of high-temperature geothermal resources in China. To date, various studies have been carried out to reveal the heat source and genesis of the abundant high-temperature resources in this area; however, studies on the contribution of the radioactive heat generated by the widely distributed granitoids to the high-temperature geothermal resources remain scarce. In order to resolve this knowledge gap, we attempted to obtain evidence from the geochemical data published in the literature in the past few decades. A total of 548 radiogenic heat production rate data were determined. The statistical data indicate that the average concentrations of the heat-producing elements U, Th, and K are 6.09±5.22 ppm, 26.74±16.78 ppm, and 3.51±0.82%, respectively. The calculated heat production values of the granitoids vary from 0.52 to 10.86 μW/m3, yielding an arithmetic average value of 3.74±2.15 μW/m3, which is higher than that of global Mesozoic–Cenozoic granites (3.09±1.62 μW/m3). Based on the heat production values, the capacity of the granitic batholiths to store heat was assessed, and the Dongcuo pluton was found to be the largest heat reservoir (382.88×1013 J/a). The distribution of the crustal heat flow was examined using the calculated heat production data and the stratigraphic structure obtained via deep seismic sounding in the study area. The results indicate that the crustal heat flow is 48.3–56.2 mW/m2, which is mainly contributed by the radioactive decay in the granitoids in the upper crust. The fact that it accounts for nearly half of the regional background heat flow indicates that the radiogenic heat from the granitoids is an important heat source for the formation of the thermal anomaly and the high-temperature geothermal resources in the study area. Thus, the results obtained in this study highlight the importance of the widely distributed granitoids to high-temperature geothermal resources in western Sichuan.

Hydrochemical Characteristics and Genetic Mechanism of Geothermal Springs in the Aba Area, Western Sichuan Province, China

Geothermal resources have been a source of significant clean energy in the world. The Sichuan Province is famous for its abundant geothermal resources in China, especially in western Sichuan. The Aba area is a significant minority region in northwestern Sichuan with abundant geothermal resources. In this study, hydrochemical and D-O analyses were conducted on the eight collected geothermal springs to investigate the genetic mechanism of the geothermal resource in the Aba area. The exposed temperatures and pH values of the geothermal springs ranged from 23 °C to 48 °C and from 6.6 to 9.5, respectively. Based on the hydrochemical characteristics, the eight geothermal springs were classified into two types: class A and class B. The class A geothermal springs belonged to the hydrochemical type of Ca-Mg-HCO3-SO4 and Ca-Mg-HCO3 and were affected by the weathering and dissolution of carbonate and silicate. The class B hydrochemical type of geothermal spring was Na-HCO3, which was determined by the weathering and dissolution of evaporite and silicate. A Na-K-Mg triangle diagram revealed that the geothermal springs belonged to immature water. A chalcedony geothermometer indicated that the temperature of the class A shallow geothermal reservoir in the Aba area was 59.70–73.00 °C and 70.65–120.91 °C for class B. Silicon enthalpy approaches showed that the initial reservoir temperature for class A was 181.36–203.07 °C (mixed by 85.76–89.44% cold water) and 271.74–295.58 °C (mixed by 87.39–87.54% cold water) for class B. The recharge elevation of the geothermal spring was 3415–3495 m as calculated by the D-O isotopes. We have proposed these genetic models of the two typical geothermal springs. The achievements provide a vital reference for the further development of geothermal water and the sustainable utilization of geothermal resources in the Aba area.

Research on wellbore temperature control and heat extraction methods while drilling in high-temperature wells

During the drilling process, the downhole high-temperature problem has considerably limited the exploration and development of deep oil and gas reservoirs and geothermal resources in China. The aim of its oil and gas exploration and development has gradually shifted to deeper formations. In this study, a transient heat transfer model for high-temperature wells during the drilling process is built. Both heat sources and variations of thermophysical properties of drilling fluids and tubular string with temperature and pressure are considered. An iterative method is used to calculate annular temperature distributions by considering fluid composition, complex casing programs combination, and well structure. Based on the model in this study, a heat extraction-while-drilling technology approach is proposed by combining insulated pipe string and the phase-change heat storage drilling liquid. The results show that this method effectively reduces the bottom-hole temperature while using the geothermal energy of high-temperature wells. The study's results provide a theoretical foundation and technical support for resolving downhole high-temperature complications in deep oil and gas, as well as geothermal well drilling. The results will be a helpful supplement for the petroleum industry in achieving the national energy aim of carbon neutrality and peak carbon dioxide emissions.

Application status and development trend of geothermal energy heating technology

With the rapid development of economy, people have higher and higher requirements for the quality of life. The traditional heating mode has serious pollution, uneven temperature, inconvenient installation, poor comfort, large energy consumption and low social benefits. It has been unable to meet people's pursuit of modern quality of life and the construction needs of environment-friendly and resource-saving society. The northern part of China is cold in winter, so it needs indoor heating. As the traditional heating mode has the problems of high energy consumption and environmental pollution, it needs to be updated and optimized. Based on the classification of geothermal energy heating technology, this paper expounds in detail the basic concepts, development and application status of shallow ground source heat pump technology, hydrothermal heating technology and middle-deep buried pipe heating technology. The emergence of geothermal energy heating technology has effectively solved a series of problems existing in traditional heating and has been widely used. In order to explore the heating potential of geothermal resources and its value in the "dual carbon" goal, the endowment and distribution characteristics of geothermal resources in China are briefly described, and the applicable geothermal energy supply models in different regions are given. By summarizing the existing reported research directions and related achievements of geothermal energy heating technology, from the perspective of operation mechanism and application practice, the technology development in this field is prospected.

Petrological and geochemical constraints on the petrogenesis of granitoids in the Gonghe geothermal basin, western Qinling (China)

The Gonghe geothermal basin is situated in the westernmost part of the western Qinling orogen and possesses the supreme potentials to explore and develop hot dry rock (HDR) geothermal resources in China. The basal rock of HDR reservoir in Gonghe basin is composed of granitoids. In this contribution, in order to constrain the formation mechanism of the Gonghe HDR, granitic samples from outcropping have been collected and drilling core samples data from the archives also been compiled. The studied results show that the obtained zircon U–Pb ages of 255.1 ± 1.9 Ma and 253.9 ± 2.6 Ma for granodiorite and monzogranite, respectively. All granitoids from both outcropping and drilling core have the similar rock associations and their major and trace elements possess the consistent evolved patterns, such as relative enrichment of LILEs (e.g., K, Rb), depletion of HFSEs (e.g., Nb, Ti), and negative Eu anomalies (0.32–0.66), indicating that they share the same magma sources and evolutional processes. And they have the affinity of I-type granites. They were derived from the mixture of partial melting of metabasaltic rocks in the lower crust and a small amount of mantle-derived magma and formed in a subduction-related setting relative to the southward subduction of the Zongwulong oceanic crust beneath the west Qinling terrane. The heat production values of rocks around the Gonghe basin were calculated and all basal granitic rocks ranges from 0.35 to 8.51 μW/m3, yielding an arithmetic mean value of 1.97 μW/m3, indicating that the radioactive heat generation capacity of granitoids in the Gonghe basin is slightly lower. The HDR reservoir in the Gonghe basin was probably due to an allied thermal effect of the radiogenic heat production in the thickening continental crust and the heat contributed by a deep magma chamber below the basin. The early Triassic granitoids with a higher thermal conductivity serve as the conductive medium of the geothermal heat; whilst the sedimentary rocks marked by lower thermal conductivity above the granitic batholiths act as the reservoir cap. This contribution provides a relatively rational understanding for the mechanism of the HDR reservoir in Gonghe geothermal basin from the petrological and geochemical perspectives, which is conducive to the geothermal potential assessment and estimation, and to-be implementation of the Enhanced Geothermal System demonstration project in China.

Geochemical evidence for the nonexistence of supercritical geothermal fluids at the Yangbajing geothermal field, southern Tibet

Exploring and exploiting high-temperature (even supercritical) geothermal resources are significant to meet energy demands and reduce carbon emissions. The Yangbajing geothermal field is the most exploited in China, with the currently highest temperature (329.8 °C) measured in a geothermal well. However, whether there are supercritical geothermal fluids beneath the deep parts of this geothermal field is under controversy. In this paper, the water isotope, chemical compositions, and C–He isotopes of gas samples were collected and analyzed. The geothermal water originated from the mixing of meteoric water and magmatic water (25%). The sources of CO2 in the geothermal field were dominated by the thermogenic degassing of carbonates and metasediments in the crust while the radioactive decay of U and Th in granite is the dominated source of He. The temperatures of three different reservoirs are 150 ± 15 °C, 250 ± 10 °C, and ∼320 °C (with a depth of ∼8 km), respectively. These were obtained using dissolved gas, soil CO2 flux, and noble gas geothermometers. Unlike other supercritical geothermal fields worldwide with larger, shallower, basaltic magma chambers, the Yangbajing geothermal field has a deep-seated, small-scale, granitic magma chamber. Thus, its geological conditions are not conducive for gestating supercritical fluids. These results are of great significance for exploring and developing high-temperature (even ultra-high-temperature) geothermal resources in China.

Building a geothermal formation model using microtremor array measurement

A comprehensive understanding of the internal structure and construction of a geomechanical formation model play an important role in developing and using geothermal resources. Formation models help in identifying the channel and cycling modes of the heat flow. Due to urban sprawl and development, constructing a formation model of geothermal resources based on data from traditional geophysical methods is challenging. The microtremor survey method (MSM) is adopted to obtain critical information in Jimo, which is famous for rare seawater geothermal resources in China. Three microtremor survey lines are deployed to identify subsurface structures up to 2 km into the ground. Dispersion curves of Rayleigh waves with frequencies from 0.4 to 10 Hz are extracted using the spatial autocorrelation method. An empirical equation is adopted to obtain the apparent shear wave (S-wave) velocity of each survey point and to plot the apparent S-wave velocity sections. The obtained sections reveal the development of two interacting faults, which form a channel for the heat-flow cycle. Two conceptual models are established to depict the formation and cycling modes of seawater geothermal resources in Jimo, based on the results and analysis. Our model will help verify the geothermal system and scientifically guide the development of unique geothermal resources. Moreover, the developed model verifies that MSM is effective and dependable for identifying fracture zones and strata.

Effect of different exploitation schemes on production performance from the carbonate reservoir: A case study in Xiong'an new area

Operational optimization is the essential factor to maximize the heat production from the thermal reservoir. Well spacing and the arrangement of the production well are the two most pivotal factors for the thermal reservoir which can ensure long-term production at economically acceptable levels. The Xiong'an geothermal area, located in the western margin of the Bohai Bay Basin, is the most developed region of the carbonate stratum and also is one of the areas that have the greatest hydrothermal geothermal resources in China. In this study, based on the temperature data of the carbonate formation and thermosphysical data from the core samples measurement, a three dimensional thermo-hydraulic coupled numerical model was established to assess the geothermal potential of the carbonate reservoir and the effect of different exploitation schemes (mainly involved the injection fluid temperature, injection mass flow rate and lateral well distance) on the thermal reservoir performance was analyzed over a period of 40 years. The effect of permeability heterogeneity on the thermal reservoir performance was also discussed as a case study. The calculation results were then analyzed on the basis of the output temperature decline curves and the cumulative energy production over the entire period from the production well. Among the three important influence factors on the carbonate reservoir performance, the injection temperature has the most significant effect on the energy production rate, followed by the injection mass flow rate and the lateral well spacing.

Performance analysis of shallow depth hydrothermal enhanced geothermal system for electricity generation

There is a large mismatch between potential estimates and developed geothermal resources in China due to high cost and risk for enhanced geothermal system (EGS) and scattered resources and low volume flow rate for hydrothermal system. Here we propose a shallow depth enhanced geothermal system (SDEGS), which can be implemented by fracturing the shallow depth hydrothermal system to create rich fractures in order to enhance permeability and volume flow rate. The mathematical models describing the continuity, momentum and energy equations in the artificial reservoir and surrounding rock, as well as the thermoelectric conversion equations of Organic Rankine cycle (ORC) are developed. From the simulation results we find that the artificial reservoir of SDEGS can provide stable heat output and outlet water temperature of respectively 59499.97 kW and 165℃for almost 23 years. For ORC for generating electricity, the net work output and thermal efficiency are respectively 8053.6 kW and 13.54 %. SDEGS can reduce the hydraulic fracturing risk and cost due to existing rich natural fractures in hydrothermal system, thus broadening the application ranges of EGS.

The status and development trend of geothermal resources in China

The status and development trend of geothermal resources in China

Occurrence of geothermal resources and prospects for exploration and development in China

Under the background of China’s energy structure optimization, environmental protection, energy conservation, and rising pressure of emission reduction, geothermal, as a potential strategic replacement energy, has ushered in new opportunities and challenges. This paper systematically summarizes the domestic achievements in the exploration and development of geothermal resources, analyzes the endowment, distribution, and accumulation mechanism of geothermal resources in China, and points out the main problems existing in the exploration and development of geothermal resources in China. On this basis, it looks forward to China’s urgent geothermal exploration and development work and key technologies to be urgently developed, providing important guidance for China’s geothermal science and technology innovation and rapid industrialization development.

Geothermal power generation in China: Status and prospects

AbstractGeothermal resources provide green, low‐carbon, and renewable clean energy, with abundant reserves and massive potential for application. The in‐depth analysis of geothermal resources in China, including their distribution and breakdown by shallow, hydrothermal, and hot dry rock (HDR) resources, is made in this study. Using the recent economic reports and state‐of‐the‐art technological solutions, this survey outlines the latest trends in the geothermal power generation in China. The application of geothermal power generation in China is still at an early stage, with the total installed capacity of 27.78 MW. The geothermal power generation technologies, such as dry steam technology, flash technology, binary cycle technology, and enhanced geothermal system (EGS), are briefly discussed and linked to their lucrative implementation sites. In particular, Tibet's Yangbajing is considered to be the most lucrative site for the EGS pilot project. The comparative analysis of low‐cost/large‐scale geothermal power generation technologies, such as low‐ to medium‐temperature one, solar‐geothermal hybrid one, and geothermal power generation in mines, was made, whose results strongly indicated the EGS technical and economical advantages. The concentration of 96% of China's population in the area to the east of Hu line affects the perspectives of high‐cost geothermal projects and has to be accounted in the comprehensive analysis of available data. Based on the revealed trends of geothermal resources’ development in China, the following guidelines are strongly recommended: comprehensive incorporation of geothermal energy generation into China's national energy and climate improvement plans, the rapid implementation of HDR technology, as well as comprehensive adaptation of the geothermal‐related projects to the local conditions/biased distribution of power consumers and state‐of‐the‐art challenges of power consumption.

Special Collection: Advances of exploration and utilization technology of geothermal resources in China

Special Collection: Advances of exploration and utilization technology of geothermal resources in China

Development of Geothermal Resources in China: A Review

Geothermal resources in China are distributed throughout the country, with hydrothermal systems of high temperature in the Tibet Autonomous Region, Yunnan Province and Taiwan Island and hydrothermal systems of low-medium temperature mainly in various sedimentary basins. Development and exploration of geothermal energy in China are below expectations. The purpose of this study is to comparatively review the characteristics (geology, hydrogeology, hydrochemistry and geophysical data) of typical hydrothermal fields/areas and suggest development and utilization approaches in the future. Hydrothermal systems formed by mountain lifting contain a considerable amount of energy for geothermal power generation, especially in the Tibet Autonomous Region, Yunnan Province and Taiwan Island. However, geothermal water in the Tatun geothermal field has high TDS (total dissolved solids), an issue that requires more research to resolve this problem for power generation. The large storage of geothermal resources has been investigated in Meso–Cenozoic sedimentary basins; it is basically used for heating, bathing or greenhouse plantation. Moreover, hydrothermal resources of low-medium temperature can also be used in binary power plants. Although the enhanced geothermal systems (EGS) in China are promising, the resources have not yet been commercially exploited, because the emerging technologies (hydraulic fracturing) and concerns over environmental impacts (induced micro-seismicity) lead to slow development. On the contrary, shallow geothermal energy has been directly utilized mainly for heating and cooling buildings. Cities like Beijing, Tianjin and Shenyang have established a series of ground-source heat-pump systems, which has led to a massive reduction of CO2 emission of 19.87×106 t.

Research status of geothermal resources in China

As the representative of the new green energy, geothermal resources are characterized by large reserve, wide distribution, cleanness and environmental protection, good stability, high utilization factor and other advantages. According to the characteristics of exploitation and utilization, they can be divided into high-temperature, medium-temperature and low-temperature geothermal resources. The abundant and widely distributed geothermal resources in China have a broad prospect for development. The medium and low temperature geothermal resources are broadly distributed in the continental crustal uplift and subsidence areas inside the plate, represented by the geothermal belt on the southeast coast, while the high temperature geothermal resources concentrate on Southern Tibet-Western Sichuan-Western Yunnan Geothermal Belt and Taiwan Geothermal Belt. Currently, the geothermal resources in China are mainly used for bathing, recuperation, heating and power generation. It is a country that directly makes maximum use of geothermal energy in the world. However, China’s geothermal power generation, including installed generating capacity and power generation capacity, are far behind those of Western European countries and the USA. Studies on exploitation and development of geothermal resources are still weak.

Exploitation and Utilization of Oilfield Geothermal Resources in China

Geothermal energy is a clean, green renewable resource, which can be utilized for power generation, heating, cooling, and could effectively replace oil, gas, and coal. In recent years, oil companies have put more efforts into exploiting and utilizing geothermal energy with advanced technologies for heat-tracing oil gathering and transportation, central heating, etc., which has not only reduced resource waste, but also improved large-scale and industrial resource utilization levels, and has achieved remarkable economic and social benefits. Based on the analysis of oilfield geothermal energy development status, resource potential, and exploitation and utilization modes, the advantages and disadvantages of harnessing oilfield geothermal resource have been discussed. Oilfield geothermal energy exploitation and utilization have advantages in resources, technical personnel, technology, and a large number of abandoned wells that could be reconstructed and utilized. Due to the high heat demand in oilfields, geothermal energy exploitation and utilization can effectively replace oil, gas, coal, and other fossil fuels, and has bright prospects. The key factors limiting oilfield geothermal energy exploitation and utilization are also pointed out in this paper, including immature technologies, lack of overall planning, lack of standards in resource assessment, and economic assessment, lack of incentive policies, etc.