Geothermal Energy Development Research Articles

New Advances in Oil, Gas, and Geothermal Reservoirs

The most significant geo-energy sources in the world today continue to be oil, gas, and geothermal reservoirs. To increase oil and gas reserves and production, new theories are constantly being developed in the laboratory and new technologies are being applied in the oilfield. This Special Issue compiles recent research focusing on cutting-edge ideas and technology in oil, gas, and geothermal reservoirs, covering the fields of well drilling, cementing, hydraulic fracturing, improved oil recovery, conformance control, and geothermal energy development.

Current status and issues of development of geothermal and geo-heat energy

Current status and issues of development of geothermal and geo-heat energy

Characteristics And Development Status of Geothermal Resources in Iceland

As Global warming is becoming increasingly severe, decarbonization has become the primary trend in the world. One way to achieve this trend is to use renewable energy resources. Among many kinds of renewable energy, geothermal energy is very neat, and its abundant storage capacity. Also, geothermal resources play a significant role in the energy supply of Iceland. They are utilized both for electricity generation and direct heat application. To this end, this article explains why geothermal energy is abundant in Iceland, and the example of utilization, some advanced technology like drilling technology and power generation technology. In addition, this article introduces the management of geothermal energy like some crucial policies. On this basis, the report concludes Iceland’s experience of a successful transition from using traditional fossil fuels to fully utilizing renewable energy. And the report describes the limitation and future development of geothermal energy.

Numerical Simulation of Geothermal Reservoir Reconstruction and Heat Extraction System Productivity Evaluation

The key to ensuring the economic feasibility of EGS mainly includes two points. On the one hand, it is necessary to ensure the connectivity of the artificial fracture network; on the other hand, it is necessary to determine the most efficient geothermal energy exploitation mode. Most previous studies have only focused on one of the points. To restitute the entire geothermal energy development process, the two parts should be combined to conduct research. In this study, a random fractured medium model was established based on the TOUGH2-BIOT simulation program and the whole process of reservoir stimulation was analyzed. According to the results of reservoir stimulation, different geothermal energy exploitation schemes are set up, and the heat transfer efficiency of the conventional double vertical wells, the horizontal wells, and the double-pipe heat exchange system are comparatively analyzed. The results show that reservoir reconstruction is mainly divided into three stages: In the first stage, the hydraulic aperture of the conducting fractures reaches the maximum value; in the second stage, the non-conductive fractures overcome the in situ stress and become conducting fractures; in the third stage, the rock in the reservoir undergoes shear failure, the fractures expand and connect, and finally, a fracture network is formed. After each stage, the volume of the enhanced permeability area is approximately 10,000, 21,000, and 33,000 m3, respectively. After 30 years of exploitation, the outlet temperature and thermal power output of conventional double vertical wells are the highest, while the horizontal wells have the highest heat extraction ratio. The temperature of a production well in the conventional double vertical wells model, horizontal wells, and double-pipe heat exchange system is 101 °C, 93.4 °C, and 91.6 °C, a decrease of 41.2%, 45.7%, and 46.7%, respectively. The thermal power output is 6.67 MW, 6.31 MW, and 6.1 MW, a decrease of 39.4%, 42.6%, and 44.5%, respectively. The heat extraction ratio of the horizontal wells is 2% higher than the double-pipe heat exchange system and 6.5% higher than the conventional double vertical wells.

Context and mitigation of lost circulation during geothermal drilling in diverse geologic settings

Lost circulation is one of the most common and expensive problems facing geothermal energy development, representing up to 30% of drilling costs. We examined drilling records from four geothermal fields—McGinness Hills in central Nevada, Don A. Campbell and Steamboat Hills in western Nevada, and Puna Geothermal Venture on the Big Island of Hawai'i— to identify geologies most prone to lost circulation, as well as common mitigation strategies. Depths of lost circulation events varied, but their frequency often increased in the production interval. Lost circulation commonly occurred near fault intersections, and heavily faulted fields like McGinness Hills and Don A. Campbell showed secondary mineralization within approximately 100 m (328 ft) or less of where circulation was lost. Lost circulation mitigation strategies included using locally available materials (e.g., cotton seed hulls) as well as more expensive proprietary lost circulation materials, cement plugs above the reservoir, and drilling blind with aerated, polymer-based mud in the production zone. Addressing lost circulation using a well thought out decision-making approach and materials above the reservoir will save time and cost, and provide needed well integrity. Mitigation often requires a series of steps, typically applied from perceived least expensive to most, and are dependent on the severity and location in the well where circulation was lost and availability of materials. Placing cement plugs can cure lost circulation events, however these plugs are often expensive, time-consuming, and may not be successful.

Current Situation, Challenges and Prospects of Geothermal Energy Development in China

Based on the geothermal resource conditions, the current situation of China's geothermal energy utilization in heating (cooling), power generation, hot spring bathing, high-end seed breeding, and hot dry rock exploration and development are explained. The development trend of geothermal energy in the fields of resource discovery, exploration, development and utilization technology, utilization scale, macro policies, and market participants are predicted in the context of the goal of "carbon peak and carbon neutral". Finally, suggestions on the management of China's geothermal industry is proposed.

Numerical simulation of thermo–hydraulic coupling processes in fractured karst geothermal reservoirs

Fractured karst geothermal reservoir is a kind of typical geothermal reservoirs with the advantages of abundant storage water and easy reinjection of tail water during the period of geothermal utilization. Such geothermal system is also one of the geothermal reservoirs with the greatest potential for the development and utilization of geothermal energy in China. However, its geological structures are diverse (e.g. pore, fracture and vug), exhibiting complex characteristics of multiple scales, strong heterogeneity and various flow regimes. Therefore, the fluid-heat transfer processes and geothermal production performance of fractured karst geothermal reservoirs are not clarified. In this paper, a numerical model considering thermo–hydraulic coupling processes based on the discrete fracture–vug network approach is put forward, according to the characteristics of fractured–vuggy geothermal reservoirs. In addition, the accuracy of the numerical model is verified. The results obtained from this research are as follows. First, the numerical model considering the thermo–hydraulic coupling process is put forward, in which the Darcy's law is used to describe the flow zone of porous medium, the Navier–Stokes equation is used to illustrate the free flow zone of vugs, and the Beavers–Joseph–Saffman boundary condition is used to couple the fluid flow between these two zones. Second, the connectivity of fracture network is the key parameter to control and evaluate the flow and heat transfer effects in fractured vuggy geothermal reservoirs. The existence of vugs plays an important role in the fluid flow and heat transfer in geothermal reservoirs. Third, the thermo–hydraulic coupling model based on the discrete fracture–vug network can effectively describe the fluid flow and heat transfer processes in fractured vuggy geothermal reservoirs. The connectivity of fracture networks controls the thermo–hydraulic coupling processes in fractured vuggy geothermal reservoirs. Fourth, the existence of vugs seriously impacts the thermo–hydraulic coupling processes in geothermal reservoirs. For instance, on the one hand, it increases the number of high-speed flow channels spanning across the system and even makes the system get connected. On the other hand, it increases the speed of local flow channels inside the system. In conclusion, this proposed method is of great significance for studying the development characteristics and optimizing their geothermal production performance of fractured vuggy geothermal reservoirs.

Assessment of the Thermal Power of Groundwater Intakes in the Kielce District

Abstract The purpose of the article was to estimate the thermal power of groundwater intakes of the Kielce district within the sheets of hydrogeological maps with the serial numbers MHP 813-817, MHP 850-851, and to indicate in this area prospective areas for the development of low-temperature geothermal energy supported by water/water heat pumps. Based on the calculations on the basis of 147 groundwater intakes, it was determined that the estimated values of thermal power resources are in the range of 3.47 kW to 5757.34 kW. The created map of the low-temperature geothermal potential for groundwater intakes indicates the towns of Bodzentyn, Morawica and the villages of Piekoszów, Wolica and the area around the village of Górno as prospective areas.

The situation analysis of hot dry rock geothermal energy development in China-based on structural equation modeling

In order to combat climate change, China proposed a dual carbon target in 2020. (China's 2030 and 2060 Goals). If the goals can be achieved as scheduled, it will help the world achieve the carbon neutrality goal earlier and improve the increasingly serious global climate. Reducing the utilization of fossil fuels and increasing the share of clean energy in primary energy are major ways to achieve China's 2030 and 2060 Goals. As a geothermal resource with large reserves, high energy storage, clean and pollution-free, dry hot rocks can effectively contribute to the goals. To promote the utilization of dry hot rock, this paper quantitatively studies the factors affecting the development and utilization of dry hot rock, and first summarizes five major influencing factors, namely, resources, environment, market, exploration and development technology, and effective use of technology. Then questionnaire survey based on these five factors was designed and distributed by email to geothermal energy experts in universities (China University of Geosciences, etc.) and research institutions (Chinese Academy of Sciences, etc.). Finally, the questionnaires are subjected to a reliability credibility test and validity analysis to remove the non-conforming items, and the structural equation model was constructed to analyze the data. The results show that environment, market and exploration and development technology have significant effects on dry hot rocks, while resources and effective use of technology have insignificant effects on dry hot rocks. Finally, some suggestions to promote the development of dry hot rocks in China are proposed.

Multi-objective balanced method of optimizing the heat extraction performance for hot dry rock

Geothermal energy, a kind of clean and environmentally friendly energy source, is an important object of future natural resource development and utilization, among which, hot dry rock is one of the important deep geothermal resources. In the current multi-objective optimization of heat extraction performance, reservoir production models are less considered and the effects of different optimization ideas are not compared comprehensively. To improve the heat extraction efficiency and prolong the exploitation life of geothermal reservoirs, this paper determines the appropriate operating parameters of geothermal system (injection temperature, injection rate, production pressure and injection-production well spacing) based on the coupled thermal-hydraulic-mechanical model of hot dry rock exploitation in the Gonghe area of Qinghai and three heat extraction optimization methods. In addition, the heat extraction performances of different schemes are comparatively evaluated. And the following research results are obtained. First, the sensitivity analysis of injection and production parameters shows that power generation and recovery factor are in a reverse relation with injection-production pressure difference, which is the direct reason for the adoption of multi-objective optimization. Second, the optimization scheme prepared on the basis of parametric study indicates that the shortest life of a geothermal reservoir is 10 years, the injection-production pressure difference is up to 67 MPa, there is a significant thermal breakthrough phenomenon and the reservoir safety faces challenges. Third, by virtue of multi-objective optimization and decision making integration, the optimal operation parameter combination of hot dry rock system is determined, the life of geothermal reservoirs can exceed 20 years and balanced optimization is achieved. In conclusion, the idea of multi-objective optimization is feasible and applicable to geothermal energy exploitation and this method provides a reference for the efficient geothermal energy development and utilization and is helpful to the realization of “double carbon” goal in China.

Technological Advancements and Challenges of Geothermal Energy Systems: A Comprehensive Review

Geothermal is a renewable energy source, but this is not as often seen as other renewable energy sources, such as solar, wind, hydro, etc. Several applications could be implemented through geothermal energy, and heating & cooling systems are one of them. Because of the limits of technology, it is hard to improve cooling systems as an application. To address long-term sustainable space heating and cooling, it is imperative to develop geothermal technology. It is known as the oldest, most flexible, most adaptable, and most prevalent approach toward using renewable energy. Therefore, this review has reviewed the global development and challenges of geothermal energy for cooling systems. There are large reserves of geothermal energy available around the world, and numerous scholars have emphasized its importance, but due to a lack of knowledge, no operational work has been done in using these systems for cooling up to this point. This review paper examines globally available geothermal energy sources and technologies for environmentally friendly and sustainable cooling supplies. Finally, the benefits and challenges of geothermal systems for cooling are outlined to promote local, regional, and global investment in utilizing these resources for cooling.

Propagating Hydraulic Fractures from Wellbores: Effects of In-Situ Stress and Near-Wellbore Stress Redistribution

Summary As a mature technology to enhance the permeability of geological formations, hydraulic fracturing has widely been used in geothermal energy development and in the petroleum industry. Due to its effectiveness in practical applications, it attracts many research efforts. Because of the complexity of hydraulic fracturing itself and the complex distribution of stresses around wellbores, accurately describing the behaviors of hydraulic fractures is still a challenging task. In this study, a numerical model is developed to simulate curved propagation of hydraulic fractures from a wellbore, and emphases are placed on influence of in-situ stress and near wellbore stress redistribution. In the developed hydromechanical model, special considerations are given to its ability to simulate curved propagation of hydraulic fractures. The propagation of fractures is modeled through the phase-field method. Several cases on hydraulic fracture initiation and propagation from horizontal wellbores are studied through the proposed model. The model has been successfully verified through analytical solutions. The influence of stress redistribution caused by wellbore pressurization on hydraulic fracture initiation from wellbores is analyzed. Under different in-situ stress configurations and initial fracture orientations (perforation or flaws around wellbores are represented by the initial fractures), several patterns of hydraulic fracture propagation around the wellbores are recognized. It is found that the stress redistribution in the close vicinity of wellbores has great influences on the fracture initiation and propagation, and it makes hydraulic fractures propagate in nonplanar, complex manners. As hydraulic fractures propagate away from the stress redistribution regions around the wellbores, in-situ stress then determines the directions of fracture propagation; the curvature of fracture growth paths is mainly determined by the difference in in-situ stress, for example, σv − σhmin in this study. It has also been demonstrated that, when analyzing fracture propagation from wellbores, the wellbore stability or nonlinear deformation of a wellbore should be considered together with the fracture propagation conditions.

Study on the international competitiveness of geothermal energy products in regional comprehensive economic partnership (RCEP) agreement countries

Renewable energy usage has entered a research boom, and the exceptional use of geothermal energy in urban heating and power generation has garnered the interest of an increasing number of nations. Regional Comprehensive Economic Partnership Agreement (RCEP) countries have launched new cooperation to promote the green recovery of the regional economy, which has prompted new demands for the integration and upgrade of existing environmental resource cooperation platforms in the region, and the development of geothermal energy has greater strategic significance for RCEP nations. Using the constant market share model and innovative revealed comparative advantage index method, this article measures and analyzes the changing trend of international competitiveness of geothermal energy products in RCEP nations. The findings of this study indicate that (1) the comparative advantages of geothermal energy products in RCEP countries are insufficient; (2) structural effects have negative effects on export growth; (3) competitiveness is an important factor in promoting export trade; and (4) second-order effects have a greater impact on exports. Based on the aforementioned research findings, this article proposes appropriate countermeasures.

Pemetaan potensi geothermal Seulawah Agam berdasarkan data DEMNAS dan Landsat 8

<p>Seulawah Agam is one of the volcanoes for geothermal energy development with an estimated 150 Mwe. At the exploration stage, thermal and multispectral image analysis is needed for surface temperature calculations, subsurface temperature modeling, and geothermal potential mapping of volcanoes. In this study, we used Landsat 8 and DEMNAS data to analyze the distribution of potential geothermal areas in the Seulawah Agam. Based on analysis of Fault Fracture Density (FFD) from DEMNAS, three classifications reflect the distance of the fault, namely low level (0 - 0.30 km/km2), medium (0.30-0.60 km/km2), and high (0.60-0.90 km/km2), where the distribution of geothermal potential is at medium and high-density levels. Meanwhile, the NDVI, NDWI data analysis shows dense vegetation areas on volcanoes and relatively rare in some manifestations. It can also be confirmed well by the high-temperature distribution in some craters between 34.63 C to 46.59 C. Based on observational data. It shows that DEMNAS and Landsat 8 data are very potential to be used as an initial method of analyzing the distribution of geothermal potential on the Seulawah Agam volcano.</p>

Power from Geothermal Resources as a Co-product of the Oil and Gas Industry: A Review.

The increase in the global demand for energy and fossil fuel dependency is hindering efforts to reduce greenhouse gas (GHG) emissions. Geothermal resources supplement this increase in energy demand with reduced emissions because of their availability, base-load production profile, and climatic independence. Despite these advantages, the development of geothermal energy is limited because of different reasons such as subsurface exploration risk and high upfront capital cost for drilling and facility construction. However, similarities in infrastructure and operations between the oil and gas industry and the geothermal industry can optimize expense and development when exploiting geothermal resources. Thus, in this review, we present recent advances and applications of geothermal power systems in the oil and gas industry starting from the fundamentals and basic principles of geothermal energy and the organic Rankine cycle (ORC). These applications include the use of geothermal resources via abandoned wells, active wells, and paired thermal enhanced oil recovery processes with injection for fluid heating and energy production. Abandoned wells are alternatives that reduce costs in geothermal energy-use projects. The use of geothermal resources via active wells allows the valorization of a resource, such as the production of water, which is considered a byproduct of production activities in an oilfield. The use of thermally enhanced oil recovery processes enhances the energy conditions of fluids produced in the field, improving geothermal systems with fluids at higher temperatures. Finally, an overview is presented of the challenges and opportunities of geothermal energy in the oil industry where the requirement to improve the usage of technologies, such as the ORCs, with the working fluids used in the cycles, is highlighted. Furthermore, the importance of environmental studies and use of novel tools, such as nanotechnology, to improve the efficiency of geothermal energy usage is highlighted.

Research on goaf treatment and geothermal comprehensive utilization technology in coal mining subsidence area

Goaf treatment and comprehensive utilization of geothermal energy are great significance to the restoration of land resources and sustainable development of energy in coal mining subsidence areas. In this paper, goaf treatment technology and geothermal energy development technology are reviewed in detail. Among them, the goaf treatment technology mainly includes: caving treatment method, filling treatment method, support method, closed isolation method and joint treatment method. Geothermal development technology mainly includes: shallow ground source heat pump technology, coaxial casing development technology, pumping and reinjection technology, directional drilling technology, U-type precision docking drilling technology. The systematic idea of filling treatment and geothermal comprehensive utilization in coal mining subsidence area is proposed, and the technology is described in detail through three cases. The research results can provide innovative inspiration for subsidence control and comprehensive utilization of geothermal energy in coal mining subsidence area, and has broad application prospects.

Experimental studies on the effect of cyclic thermal shock and cooling methods on the mechanical properties and fracture behavior of prefabricated fissured sandstone

The construction of sandstone thermal storage systems and the evaluation of their long-term stability are of great significance to the development of geothermal energy. In this study, the effect of the number of thermal shocks and cooling methods on the mechanical properties and fracture behavior of sandstone containing a single prefabricated fissure was investigated. The experimental results show that as the number of thermal shocks increases, the peak stress and elastic modulus of the fissured sandstone gradually decrease, and show a very good exponential functional relationship. The first thermal shock weakens the mechanical properties of fissured sandstone most severely, and the deterioration effect of mechanical properties is significantly slowed down when the number of thermal shocks exceeds 4. In addition, compared with water cooling, the reduction of the mechanical properties of fissured sandstone by air cooling is lower. As the cooling water temperature decreases, the thermal shock effect of the fissured sandstone is more severe, resulting in more significant damage. An empirical formula considering the number of thermal shocks and cooling water temperature is proposed to characterize the damage to the fissured sandstone. The crack initiation of fissured sandstone under uniaxial compression subjected to different thermal shocks is dominated by tensile failure (wing crack). As the number of thermal shocks increases and the cooling water temperature decreases, the initial crack modes gradually change from T1 to T2, or a more complex pattern. Subsequently, the thermal shock process of fissured sandstone is simulated in COMSOL Multiphysics. The effect of heat transfer coefficient and cooling water temperature on the temperature field and stress field in fissured sandstone are discussed, and the reasons for the thermal cracking of the fissured sandstone under thermal shock are revealed.

Suitability zoning of buried pipe ground source heat pump and shallow geothermal resource evaluation of Linqu County, Shandong Province, China

In response to the environmental call for energy conservation and emission reduction, the development and utilization of shallow geothermal energy (SGE) buried pipe ground source heat pumps (GSHP) in the urban area of Linqu County has been studied. Based on geological data and water quality analysis data, ground temperature monitoring test and field thermal response test research results, using the analytic hierarchy process, the suitability of buried GSHP in the study area is computed by division, heat capacity calculation and resource potential evaluation. The results show that the development and utilization of GSHP in the study area are mainly in the moderately suitable area. The heat capacity within 120 m depth is 3.52 × 1013 kJ/°C, and the heat capacity of 200 m shallow geothermal energy is 5.84 × 1013 kJ/°C. Considering the land use coefficient, the total available heat transfer power of the buried pipe ground source heat pump is 2.56 × 106 kW. The heat transfer power in summer is greater than the heat transfer power in winter. The resource potential of buried pipe ground source heat pump is mainly in the medium potential area, and the development potential is finer in winter than in summer. Generally, the development and utilization of shallow geothermal energy in the urban area of Linqu County have broad pros.

A Finite Element Model for Investigating Unsteady-State Temperature Distribution and Thermomechanical Behavior of Underground Energy Piles

The underground energy geostructure represented by the energy pile is one of the key paths for the cooperative development of underground space and geothermal energy. Because of its advantages of low cost, high efficiency and no extra occupation of underground space, it has become a feasible alternative to the borehole heat exchanger. The change in the temperature field of the energy pile and its surrounding ground not only affects the geological environment but also influences the thermomechanical performance and the durability of the structure. However, the temporal and spatial unsteady-state temperature distribution of piles and surrounding rock under typical intermittent and unbalanced thermal load conditions is still unclear. In this paper, a finite element model was applied to analyze the unsteady-state temperature distribution, and the thermomechanical behavior of the energy pile group was developed and verified. The temperature field distribution of pile and surrounding rock under typical intermittent working and unbalanced thermal load conditions were determined. Moreover, the thermomechanical behavior characteristics of the energy pile group were investigated. Finally, the influences of pile layout on the thermomechanical behavior of the energy pile group were identified by designing six different scenarios. The results indicate that under typical intermittent operation conditions, the temperature of the energy pile and surrounding ground near the heat exchange pipe varies periodically. For areas with unbalanced cooling and heating loads, long-term operation of energy piles leads to thermal accumulation, and the maximum temperature of energy piles occurs in the first daily cycle. In summer/winter working conditions, the increase/decrease in pile temperature induces axial compression/tensile stress. When the pile group is partially used as the energy pile, the non-energy pile acts as the “anchor pile”, and it generates the added tensile stress.

Editorial: Progress in Exploration, Development and Utilization of Geothermal Energy

Editorial: Progress in Exploration, Development and Utilization of Geothermal Energy