Utilization Of Geothermal Resources Research Articles

A Method for Determining Target Areas of Hot Dry Rock Resources: A Case Study in Continental China

Geothermal resources have been recognized as important sources of clean renewable energy. The exploration, development, and utilization of geothermal resources, especially hot dry rock (HDR) resources, are highly important for achieving peak carbon and carbon neutrality. However, there is no comprehensive evaluation method for determining HDR target areas, and the evaluation scale and application disciplines are relatively simplistic. In this paper, we sought to optimize the identification of HDR target areas through a multiscale and multidisciplinary method and formed a set of generalized and demonstrative processes to guide the exploration of HDR resources. Through practical application to the Gonghe Basin and the Zhangzhou Basin, it was found that the comprehensive geothermal conditions of the Gonghe Basin are superior to those of the Zhangzhou Basin, and the geothermal reservoir depth, geothermal reservoir temperature, geothermal gradient, and heat flow are the four most important factors affecting hot dry rock geothermal resources. Using this method, the prioritization of target areas changes from a qualitative study to a quantitative and semiquantitative study, increasing the specificity and reliability of the decision-making process.

Geothermal resource evaluation in the Sichuan Basin and suggestions for the development and utilization of abandoned oil and gas wells

In this paper, the potential seven sets of geothermal resources in the Sichuan Basin were evaluated by using a method for rapidly calculating geothermal resources in the sedimentary basins by multi data fusion, and suggestions on geothermal development and utilization are made based on the basic characteristics of abandoned wells in the oil and gas fields. The results show that the Sichuan Basin is rich in geothermal resources. The total resources of 7 sets of thermal reservoirs reach 4.26 × 1013 GJ, of which the Qixia-Maokou Formation has the largest potential geothermal resources, reaching 1.36 × 1013 GJ. The Permian Qixia-Maokou Formation in southern Sichuan Basin has the conditions to prioritize the development of geothermal resources and has the characteristics of the highest temperature of formation water and the largest current and cumulative water production. At the same time, according to the formation temperature of abandoned oil and gas wells, they are divided into two types of wells, and different geothermal resource utilization methods are proposed. The research results can provide a model for the evaluation of geothermal resources in sedimentary basins and a resource basis for the development of geothermal resources in the Sichuan Basin.

Analytical Study of Permeability Properties of Loose Sandstone Based on Thermal-Hydraulic-Mechanical (THM) Coupling

The permeability of reservoirs is a key factor affecting the exploitation and utilization of geothermal resources. This test used a core flow meter and other advanced experimental devices to investigate the evolution of the permeability characteristics of loose sandstone samples (with a diameter of 25 mm and a length of 50 mm) in the Zijiao Town area under various temperatures, confining pressures, injection rates, and cyclic loading and unloading conditions. The results show that (1) as the temperature increases, the overall trend of rock permeability decreases, which is mainly related to the thermal expansion of rock particles. In addition, the higher the temperature, the greater the gravel outflow. (2) The critical pressure for pore closure in the unconsolidated sandstone in the region is approximately 15 MPa. (3) The permeability change of loose sandstone under low injection rate conditions is relatively small and can be neglected. However, there is reason to believe that under high-flow injection conditions, the permeability of this type of rock mass will undergo significant changes. (4) Under the condition of loading and unloading, the permeability ratio curve of the unloading stage at three temperatures is almost a straight line. The higher the temperature, the smaller the slope, and the permeability at 20 °C with the highest recovery degree is only about 50% of the initial one.

Magnesium Oxychloride and Magnesium Oxysulfate Cements as Temporary Plugging Agents in Geothermal Drilling.

The development and utilization of geothermal resources are effective ways to alleviate the current haze situation, adjust the energy structure, and achieve energy conservation and emission reduction. Geothermal formations typically contain extensive fracture networks, with fracture openings. These fracture networks can result in substantial losses of the drilling fluid and increased costs for geothermal drilling. Temporary plugging cements are used to solve the problem of lost circulation due to their high strength and high acid solubility. In this paper, two types of temporary plugging materials, magnesium oxysulfate (MOS) cement and magnesium oxychloride (MOC) cement, were prepared. The influence of the plugging agent on the flow field and the force exerted on the solid under the action of the fluid was analyzed using fluid-solid coupling software. The simulation results show that when subjected to a flow rate of 10 m/s, the edge of the cement experiences a significant force, while the stress is not widely transmitted to the middle and rear of the cement. This indicates that the cement has a strong resistance to the fluid flow. The fundamental characteristics of MOC cement and MOS cement, such as compressive strength and setting time, were investigated. The test results show that adjusting the molar ratio of the two types of cements can shorten the setting time by 60% and increase the compressive strength to up to 23 MPa. In addition, the acid solubility of the cement with different ratios of raw materials is above 95%. The plugging performance of these two cements as loss circulation materials was evaluated by using a physical simulation device. The pressure bearing capacity of the MOC cement with different MgO/MgCl2·6H2O/H2O molar ratios ranged between 13.4 and 23.6 MPa. The maximum bearing capacity of the MOS cement can reach up to 18.6 MPa. The results showed that both cements possess excellent plugging and pressure bearing capacity.

Application of WFEM in Geothermal Resource Exploration

Geothermal resources are a kind of ecological energy with great market potential. In order to promote the development and utilization of geothermal resources in Dunhua area and promote economic and social development, the advanced WFEM is used to delineate the hidden fault zone and fracture zone, determine the basement depth and the spatial distribution of hidden faults, find out the geological conditions of geothermal resources in this area, and make a preliminary evaluation of geothermal resources, analyze the exploitation potential of geothermal resources.

A Comprehensive Study on the Hydrogeochemical and Isotope Characteristics and Genetic Mechanism of Geothermal Water in the Northern Jinan Region

Geothermal water (GW) resources are highly valued as clean, renewable energy sources. In this study, a comprehensive analysis of water chemistry and isotope data from 25 GW samples was conducted to gain insights into the hydrochemical characteristics and formation mechanisms of the GW in the northern Jinan region (NJR). Statistical analysis and hydrochemical methods were employed for relevant analysis. The findings reveal that the GW in the NJR exhibits high salinity, with an average total dissolved solids (TDS) concentration of 9009.00 mg/L. The major ions identified are Na+ and Cl−, with mean concentrations of 2829.73 mg/L and 4425.77 mg/L, respectively, resulting in a hydrochemical type of Cl−Na. The analysis of δ2H and δ18O isotopes indicates that the GW originates from atmospheric precipitation that undergoes deep cycling and interaction with older groundwater. The composition of 3H suggests that the GW in the NJR is a mixture of waters, while radiocarbon dating (14C) suggests that the recharge of the GW may have occurred in the late Pleistocene era. The GW in the NJR is classified as partially equilibrated waters. The temperature range of geothermal reservoirs is 57.13 to 99.74 °C. The hydrochemical components primarily result from water–rock interactions, including silicate weathering, cation exchange, as well as carbonate weathering and the dissolution of halite and gypsum. Moreover, taking into account the hydrogeological conditions, hydrochemistry, and isotope analysis, a conceptual model of the geothermal reservoir in the NJR was developed. The research findings serve as a valuable reference and foundation for the development and utilization of geothermal resources in the Jinan region. These originate from the Taiyi mountains in the south or the Taihang mountains in the west, and experience deep circulation and long runoff times. This study provides a reference for the sustainable development and utilization of regional geothermal resources.

Water–Rock Interactions, Genesis Mechanism, and Mineral Scaling of Geothermal Waters in Northwestern Sichuan, SW China

Geothermal resources are the vital renewable energy for resolving energy crisis and environmental deterioration. Understanding hydrogeochemical processes, genesis mechanisms and scaling trends is crucial for securing the sustainable utilization of geothermal resources. In this study, fourteen geothermal waters were collected for hydrochemical and δ2H–δ18O isotopic analyses in northwestern Sichuan, SW China to clarify hydrogeochemical processes, genesis mechanisms, and scaling trends. Geothermal waters were recharged via atmospheric precipitation. Three different types of geothermal waters were identified using a piper diagram. Class 1 geothermal water with HCO3–Na and HCO3–SO4–Na types formed in the contact zone with Yanshanian intrusions and heated by residual radioactive heat. The hydrochemical processes were sodium/potassium silicate dissolution and positive cation–exchange. Class 2 geothermal water with HCO3–Ca and HCO3–Ca–Mg type was carbonate–type and heated by geothermal gradient. The dissolution of carbonate minerals dominated the hydrochemical process. Class 3 geothermal water with the SO4–Ca–Mg type was determined within deep faults. The dissolution of carbonatite and gypsum minerals and the oxidation of sulfides played a vital role in the hydrochemical process. The reservoir temperatures of geothermal waters followed the orders of Class 1 (74.9–137.6 °C) > Class 3 (85.9–100 °C) > Class 2 (38.7–93.5 °C). Calcium carbonate scaling should be paid attention to in Class1 and Class 3 geothermal water, and calcium sulfate scaling merely occurs in Class 3 geothermal water. This study provides vital information for geothermal exploitation in western Sichuan and other similar areas.

Cultural sustainability thresholds to measure the mauri of Indigenous Māori values impacted by geothermal engineering projects

Aotearoa New Zealand's current geothermal laws require that any engineering utilisation of geothermal resources includes an assessment of how Māori values are impacted, being the values held by the country's Indigenous Peoples. A series of wānanga (Māori-based workshops) were conducted with Māori participants to develop a list of Māori values pertinent to geothermal development, followed by a companion list of corresponding sustainability indicators that defined measurable parameters as quantitative representations of these Māori values. For each indicator, sustainability thresholds were developed, which described three possible impacted indicator states that constituted denigrated, neutral, and enhanced levels of mauri respectively, where mauri was a proposed measure of wellbeing. The information contained in the thresholds provided a means to numerically assess the extent to which an engineering project in Aotearoa would sustain the wellbeing of the listed indicators, and in turn the listed Māori values. The insights within the thresholds may be used by other researchers to develop thresholds specific to other indigenous cultures around the world and empower such cultures in their countries' own geothermal industries.

Application of Acid Fracturing Technology to Improve Water Yield of Deep Carbonate Geothermal Wells

To achieve the “carbon peak” goal, green and low-carbon energy development is the key. The development and utilization of geothermal resources and the development of deep carbonate geothermal wells in China are analyzed. Based on the principle of chemical reaction between hydrochloric acid and the main components of carbonate rock, four rock samples from geothermal wells were dissolved with 15% and 20% hydrochloric acid, respectively. The comparison showed that 15% hydrochloric acid was more economical and effective. The percolation capacity of acid dissolution fractures was tested through percolation capacity experiments, and the optimal amount of acid solution was determined to be 2-8 PV. It was verified that acid dissolution helps improve fracture percolation capacity. Through the on-site testing of acid fracturing technology in the Xiong’an New Area, it has been verified that the on-site implementation of multi-stage acid fracturing has a significant effect on increasing production. Finally, conclusions are drawn. The method of using acid solution dissolution to increase the water yield of deep carbonate geothermal wells is feasible, and the multi-stage acid fracturing technology is suitable for deep wells and can increase the water output of geothermal wells, which has good promotion value.

Influencing parameters of recharge efficiency and well types optimization in middle-deep sandstone geothermal reservoir

ABSTRACT Recharge efficiency is of importance to ensure the sustainable utilization of geothermal resources. However, there are still challenges for reinjection work of porous sandstone in North China. The present work aims at optimizing reinjection parameters and well types based on the high recharge efficiency, and it was studied by establishing a numerical model of geothermal production-reinjection and designing an indoor reinjection experiment. It is observed that the effects of skin coefficient, daily reinjection amount, well diameter, well inclination angle, and water layer thickness ratio on the recharge efficiency are decreased in turn. In order to ensure the high efficiency of reinjection work, the mode of two reinjectors and one producer should be selected, preferentially considering around 60° directional well or horizontal well. The skin coefficient should be controlled about 1, the well diameter is greater than 81/2 in, the daily reinjection amount is greater than 2320 m3, and the water layer thickness ratio is about 1:3. The present results can provide helpful references for optimal selection of reinjection parameters and well types of Sandstone Geothermal Reservoir.

Simulation Study on Seepage Patterns of Geothermal Reinjection in Carbonate Thermal Reservoir and Geothermal Doublet Well Patterns in Xiong’an New Area

The karst fissures of the carbonate thermal reservoir in Xiong’an New Area have developed, and they have the advantages of a concentrated distribution, shallow burial, large water volume, and easy recharge, which are conducive to the development and utilization of geothermal resources. This paper took the carbonate thermal reservoir in Xiong’an New Area as the research object and studied the characteristics of the seepage patterns and temperature distribution in thermal storage with different well arrangements and recharge methods by laser etching the micromodel of the carbonate thermal reservoir and simulating the recharge methods. The paper established a numerical model of the resettlement area of Xiong’an New Area based on the production data and the current recharge well pattern, and it proposed a plan for a geothermal doublet well arrangement. The results showed that the injection speed and angle significantly influenced the seepage of injected water in the fractured reservoir. The injection speed correlated with the breakthrough time and swept area. The breakthrough time plummeted as the injection speed increased, and the swept area crept up as the injection-fracture dip increased. The well arrangements also impacted the seepage patterns. The well pattern of two injectors and three producers was relatively suitable for geothermal reinjection, and it was more appropriate to choose the maximum injection-fracture dip because of the largest swept area. Factors that affected the sustainable development and utilization of geothermal fields included the well pattern arrangement, well spacing, injection and production volumes, and the temperature of the injected water. Based on the modeling, it is recommended that the well spacing be greater than 500 m, and the injection and production volumes less than 110 m3/h in the resettlement area of Xiong’an New Area. Moreover, a vertical fracture well is recommended to reduce thermal breakthroughs.

Generalized model for predicting the thermal conductivity of fine-grained soils

As a renewable energy, geothermal is considered as one of the important approaches to mitigate the energy crisis and climate change. The thermal conductivity of soils is a key parameter required in the utilization of geothermal resources, and it plays an important role in engineering, environmental science, earth science, and agriculture. Generally, the existing models that predict the thermal conductivity of soil are limited to specific types of soil and specific conditions. As a result, it is difficult to apply these models to engineering practice. Therefore, a simple, efficient, and generalized model capable of predicting the thermal conductivity of soils is necessary. In this work, a generalized model for calculating the thermal conductivity of fine-grained soils is established. This model considers the initial dry density, initial water content, temperature, and mineral composition. The proposed generalized model is based on a large amount of measured data from different countries and regions. Its validity is verified after being cross-validated with a back-propagation artificial neural network (BP-ANN) model. Compared with two existing models, the proposed model achieves the best thermal conductivity estimation of fine-grained soils. Additionally, it has a wide range of applications, requires only a few parameters, and does not need recalibration.

Distribution, exploitation, and utilization of intermediate-to-deep geothermal resources in eastern China

The part of China, east of the Hu Huanyong Line, is commonly referred to as eastern China. It is characterized by a high population density and a well-developed economy; it also has huge energy demands. This study assesses and promotes the large-scale development of geothermal resources in eastern China by analyzing deep geological structures, geothermal regimes, and typical geothermal systems. These analyses are based on data collected from geotectology, deep geophysics, geothermics, structural geology, and petrology. Determining the distribution patterns of intermediate-to-deep geothermal resources in the region helps develop prospects for their exploitation and utilization. Eastern China hosts superimposed layers of rocks from three major, global tectonic domains— namely Paleo-Asian, Circum-Pacific, and Tethyan rocks. The structure of its crust and mantle exhibits a special flyover pattern, with basins and mountains as well as well-spaced uplifts and depressions alternatively on top. The lithosphere in Northeast China and North China is characterized by a thin, low density crust and mantle, whereas the lithosphere in South China has a thin, low density crust and a thick, high density mantle. The middle and upper crust contain geobodies with high conductivity and low velocity, with varying degrees of development that create favorable conditions for the formation and enrichment of geothermal resources. Moderate-to-high temperature geothermal resources are distributed in the Mesozoic–Cenozoic basins in eastern China, although moderate temperature geothermal resources with low abundance dominate. Porous sandstone reservoirs, karstified fractured-vuggy carbonate reservoirs, and fissured granite reservoirs are the main types of geothermal reservoirs in this region. Under the currently available technical conditions, the exploitation and utilization of geothermal resources in eastern China favor direct utilization over large-scale geothermal power generation. In Northeast China and North China, geothermal resources could be applied for large-scale geothermal heating purposes; geothermal heating could be applied during winter along parts of the Yangtze River while geothermal cooling would be more suitable for summer there; geothermal cooling could also be applied to much of South China. Geothermal resources can also be applied to high value-added industries, to aid agricultural practices, and for tourism.

Experimental investigation of water-rock reaction for the reinjection of sandstone geothermal reservoirs: A case from Neogene Guantao Formation in Tianjin

Reinjection is of importance to ensure the sustainable utilization of geothermal resources. However, there are still challenges for achieving complete reinjection of pore-type sandstone reservoirs. Taking Neogene sandstone in Tianjin as an example, water-rock reaction experiments under four reinjection fluids at 60 °C and 15 MPa were designed and performed. From the point of view of inner pores and permeability, the variations of pH, TDS and mineral compositions were compared, and their influences on the reinjection were analyzed. Responses of hydrogen and oxygen isotopes to water-rock reactions were obtained. Further, the statistical method including principal component analysis, cluster analysis and Pearson relevance analysis revealed the intrinsic correlations among 9 major hydrochemical compositions, 41 trace elements and 6 mineral compositions during the water-rock reactions. Test results showed that nanofiltration treatment water had more advantages as an alternative reinjection fluid, and the municipal tap water was not recommended. It was found that specific trace elements (e.g. Cu, Pb, Ni, Co, Rb) can be used as potential indicators of dissolution or precipitation of sandstone minerals (e.g. quartz, calcite, ankerite, clay minerals). The present results can provide helpful references for optimal selection of reinjection fluids as well as monitoring and evaluation of geothermal reservoirs.

Mechanical Properties of High-Temperature Granite under Liquid Nitrogen Cooling

The cooling characteristics of liquid nitrogen can effectively weaken the mechanical properties of dry hot rock reservoirs, improve the porosity and permeability of dry hot rock, and thus improve the development and utilization of geothermal resources. In order to explore the weakening effect of liquid nitrogen cooling characteristics on high-temperature reservoir rocks, uniaxial compression tests, Brazil splitting tests, and three-point bending tests were conducted on high-temperature granite, and synchronous acoustic emission tests were conducted to monitor the damage evolution of rocks. It is found that under the action of liquid nitrogen, the elastic modulus, peak strength, fracture toughness, and other mechanical properties of granite decrease to varying degrees. At different initial temperatures, the damage degree of liquid nitrogen to granite is different. The higher the initial temperature of granite, the greater the damage effect of liquid nitrogen on granite. The low-temperature characteristics of liquid nitrogen not only have the effect of cracking damage on granite but also have the effect of thermal stress on granite. If the temperature difference between the two is large, the heat released in the combination process will be higher. The greater the temperature difference, the greater the damage to granite. Under the action of liquid nitrogen, the acoustic emission characteristics of granite also show different evolution laws, and the ringing count of rock increases significantly, which indicates that liquid nitrogen aggravates the internal damage of granite, making the rock more fractured during fracturing. The research results can provide some scientific guidance for the development and utilization of geothermal energy.

Preface

ITB International Geothermal Workshop 2022 was an event organized by ITB Geothermal Master Program which was held on August 2 – 4, 2022 on an online basis through a live virtual workshop (Webinar) via Zoom and YouTube. Followed by over 2200 participants from many different aspects of the geothermal community, such as academia, industries, and government. This year’s theme is “Geothermal Competitiveness in Supporting Net-Zero Emission: From Technical to Business Model”, which focuses more on the Prospecting and Utilization of Geothermal Energy and collaborating Indonesia Geothermal Stakeholders by inviting speakers from various aspects in geothermal energy.The 11th ITB International Geothermal Workshop is expected to become a melting pot for sharing knowledge, experiences and solving technical and non-technical geothermal issues in Indonesia. For this year’s event, the focus of discussions would be the development and innovation of technology for the exploration, exploitation, and utilization of geothermal resources, socio-economics, green investment, and competitive business models.List of Conference Details, Committee are available in this Pdf.

Present status and sustainable utilization of hydrothermal geothermal resources in Tianjin, China: a critical review

<abstract> <p>Tianjin, as one of the pioneering and most prominent cities in China, has a long history of harnessing geothermal energy. The geothermal resource available in Tianjin is primarily characterized as a low- to medium-temperature hydrothermal geothermal resource. This manuscript introduces the ongoing status and potential of geothermal utilization in China, with a particular focus on the characteristics and utilization status of geothermal resources in Tianjin, China. Moreover, the relevant strategies and challenges for cost-efficient sustainable utilization of Tianjin geothermal resources are identified. The formation parameters of heat storage characteristics of Tianjin geothermal resources are also discussed. In addition, the key paths, guidelines and challenges on how to solve the obstacles related to the geothermal resources development in Tianjin are also suggested. The summarized results indicate that the geothermal reservoirs exploited in Tianjin vary greatly, which include sandstone of Neogene Minghuazhen formation, Guantao formation, Ordovician and Cambrian and carbonate of Proterozoic Wumishan formation. Most of the exploitative geothermal resources (146 geothermal wells) in Tianjin have mainly been produced from the Wumishan formation of the Jixian system and the Guantao formation of the Neogene system. The current production capacity has been doubled, and a two-stage cascade utilization system has been established, incorporating geothermal power generation and geothermal heating. The geothermal utilization share in Tianjin is estimated to be 81.66% for heating, 16.6% for domestic hot water and 1.35% for bathing. In conclusion, notwithstanding the diversity of geothermal resources in Tianjin, it is difficult to guarantee the sustainable development and utilization of geothermal resources in Tianjin due to the unreasonable layout of geothermal wells, imbalance of production and reinjection. Hence, the integration of distributed temperature sensing and distributed strain sensing monitoring demonstrates significant promise and effectiveness in tracking water circulation and detecting flow localization problems as dynamic monitoring processes and smart thermal response tests should be recommended and established as a substantial feature required in the future utilization and development of geothermal resources in Tianjin.</p> </abstract>

Research progress and prospect of geothermal resources

The world is reducing the use of fossil energy. Reducing carbon emissions will help protect the atmospheric environment. Because geothermal resources are are green, clean and carbon free energy, these are much accounted of by many countries. This paper explains the geological and geophysical characteristics of geothermal resources, summarizes the research of classification and utilization of geothermal resources, and expounds the technical process and difficult problems in the utilization of geothermal resources. It is concluded that if the key problems of geothermal resources utilization are solved, there will be a broad prospect for the utilization of geothermal resources.

Geothermal geological characteristics and exploitation potential in Nanyang Basin

Based on the geothermal geological conditions and the geothermal resources development and utilization data of Nanyang Basin for many years, the geothermal fields in the basin are divided according to the study of fault structures. According to the pumping test data of geothermal wells, the permeability coefficients of the thermal storage aquifers of the geothermal wells were calculated using the steady-flow Dupuit formula and Kusakin's empirical formula. In this paper, the water conductivity of thermal reservoir is calculated by using the method of line diagram and recovery water level, and the characteristics of thermal reservoir aquifer group, geothermal fluid flow field, and hydrochemistry are described systematically. Based on the analysis method of groundwater exploitation potential index, the development and utilization potential of geothermal resources is studied, which has certain reference significance for the development and utilization of geothermal resources of sedimentary basins.

Multi-mode and exergoeconomic analysis of a novel combined cooling, heating, and power system applied in the geothermal field

The exploitation and utilization of geothermal resources contribute to alleviating energy crisis and reducing environmental pollution caused by the use of fossil fuels. The energy systems driven by low-grade geothermal heat sources also have the potential for energy-saving and emission reduction. Among all kinds of energy systems, multi-mode systems with characteristics of various operation modes and flexible energy output have been widely concerned. In this work, a multi-mode CCHP system with a novel structure is proposed and driven by a closed type of geothermal heat source. The proposed parallel system is composed of a vapor compression heat pump cycle, an organic Rankine cycle, and a vapor compression refrigeration cycle. The exergy efficiency and total product unit cost are selected as objective functions in multi-objective optimization processes to characterize system thermodynamic and exergoeconomic performances, respectively. The proposed system can operate in seven different modes to realize the conversion of power, heating, and cooling capacity output. The effects of main parameters, including evaporation pressure, condensing temperature, split ratio, etc, on system performances were studied. Results found that the coupling evaporator had the highest exergy destruction rate while the component turbine showed the largest capital cost. From the viewpoint of exergoeconomic performance, the turbine and coupling condenser were the most two important components. After that, the multi-objective optimization results revealed the limits of comprehensive system performance under such closed heat source conditions. Finally, the adjustable analysis found the performance range of the proposed system regulating the seven different operation modes. The exergy efficiency and total product unit cost fluctuated in the ranges of 18.68–52.64 % and 9.56–14.93 $/GJ, respectively.