Exploitation Of Geothermal Energy Research Articles

Aridisols in the Southern Permian Basin of Lithuania: a key to understanding clay cement distribution

The change from fossil to geothermal energy supply includes the necessity to re-evaluate gas reservoirs in the Southern Permian Basin of NW Europe, as higher permeability reservoirs are needed for the exploitation of geothermal energy than natural gas. A key reservoir risk in Permian sandstones in the Southern Permian Basin is the presence of clay cement. The distribution of the clay cement is not properly understood. The negative effect can be attributed to complex grain coatings formed by tangential clay directly around the detrital grains followed by authigenic clay rim cement, both being genetically related. This study presents new results on the origin of the tangential and the authigenic clay. The Southern Permian Basin in Lithuania was a marginal area of the basin with low accommodation rates and extensive aridisol development. Here, sandstones of the Perloja Formation contain abundant clayey matrix in the form of grain and void coatings. The limited burial depth of a few hundreds of metres ensured that the original internal fabric and mineralogy of the clay coatings remained well preserved. Thin section microscopy revealed that the clay coatings are cutans that formed by post-depositional mechanical infiltration (illuviation) of suspensions of clay minerals, iron hydroxides and some clay to silt-sized quartz. Other pedogenic features are the development of nodular calcrete, rootlets, and of infiltrated clay. Aridisols were recurrently eroded by fluvial or aeolian activity causing wide-scale dispersion of siliciclastic grains with more or less complete clay cutans and also carbonate (calcrete) clasts in certain stratigraphic intervals.

Analyzing the heave of an entire city: Modeling of swelling processes in clay-sulfate rocks

Ground source heat pump (GSHP) systems play a key role in the exploitation of shallow geothermal energy as a renewable energy source. In clay-sulfate rocks, however, rock swelling is a major threat to the success of GSHP projects that may require extensive and costly countermeasures to mitigate the effects. Swelling is in these cases triggered by water ingress into expansive anhydrite bearing rock layers, followed by the chemical transformation of the sulfate mineral anhydrite to gypsum upon contact with water. Thus, assessing, understanding and quantifying coupled hydraulic and geochemical changes in the swelling zone is essential for selecting effective countermeasures. The present study examines these processes for a study site in Staufen, Germany, where an improper borehole heat exchanger (BHE) installation has allowed ingress of water into the clay-sulfate bearing strata of the Gipskeuper, followed by swelling and substantial heave of the land surface. A reactive transport model was employed to isolate the key processes and to evaluate a range of mitigation scenarios. The model simulations allowed for the assessment of (i) water inflow into the swelling zone, (ii) water availability for the transformation of anhydrite into gypsum within the swelling zone, and (iii) the potential for future swelling for each of the considered scenarios. Our results indicate that even with incomplete BHE sealing, water flow into the swelling zone and thus the swelling process can be arrested through appropriate hydraulic countermeasures. In contrast, our worst case scenario simulation predicts a further 10 cm of heave at the ground surface by 2025. The results illustrate the importance of integrating geological, hydraulic and geochemical information when assessing and predicting the efficiency of site-specific mitigation measures.

Numerical simulation of heat release performance of filling body under condition of heat extracted by fluid flowing in buried tube

It is the basic requirement of the synergetic exploitation of deep mineral resources and geothermal resources to arrange the heat transfer tube in filling body. The heat release performance of filling body directly impacts on the exploiting efficiency of geothermal energy. Based on heat transfer theory, a three-dimensional unsteady heat transfer model of filling body is established by using FLUENT simulation software. Taking the horizontal U-shaped buried pipe as research object, the variation of temperature field in filling body around buried pipe is analyzed during the heat release process of filling body; the initial temperature of filling body, the diameter of buried pipe, the inlet temperature and inlet velocity of heat transfer fluid influencing of coupling heat transfer, which exists between heat transfer fluid and surrounding filling body within a certain axial distance of buried tube, and influencing of temperature difference between inlet and outlet of heat transfer fluid and on heat transfer performance of filling body are also discussed. It not only lays a theoretical foundation for the synergetic exploitation of mineral resources and geothermal energy in deep mines, but also provides a reference basis for the arrangement of buried pipes in filling body as well as the selection of working conditions for heat transfer fluid.

Hydrogeochemical characteristics and formation of the hot springs occurring in the plunging ends of an anticline in Chongqing, Eastern Sichuan Basin, China

Hot springs occurring in two plunging ends of a very long and narrow anticline is unique. This study focuses on the hydrogeochemical characteristics and formation of the anticline-controlled thermal groundwater which may provide a perspective for geothermal resources potential. The low-to-middle temperature thermal groundwater of the Taozidang anticline in the Sichuan Basin, China, was examined to estimate the temperature of the deep reservoir and identify the main hydrogeochemical processes affecting the composition of hot water during circulation and evolution. The occurrences of thermal groundwater of these springs strongly controlled by anticline are in the two plunging ends of the anticline and differ from that of the more common deep-fault circulation controlled by faults or by faults and anticlines. Incongruent dissolution of the gypsum or anhydrite of the Lower Triassic Jialingjiang and Middle Triassic Leikoupo Groups is affected by the anticline structures and results in hot water of SO4–Ca type. Meteoric water infiltrates through the karst channels and fissures at the outcropping area of carbonates to feed the groundwater. Part of the groundwater flows to depth and circulate along the two flanks of the anticline after heated. It issues in the form of hot springs or wells in the plunging ends of the anticline. Another part of the groundwater undergoing a shallow circulation forms the normal temperature spring near the hot springs. This study of the anticline-controlled thermal groundwater is important for exploitation and utilization of geothermal energy (tourism) and provides a perspective for the anticline-controlled geothermal resources potential.

Distribution of porosity-preserving microquartz coatings in sandstones, Upper Jurassic Danish Central Graben

High porosity is a key factor for good reservoir sandstones for both hydrocarbon and geothermal energy exploitation. The porosity of sandstones generally decreases with increased burial depth due to compaction and cementation. However, some sandstones in the North Sea show higher porosity than expected for their burial depth, due to the presence of micro­quartz coatings (e.g. Aase et al. 1996; Hendry & Trewin 1995; Jahren & Ramm 2000; Maast et al. 2011). Siliceous sponge spicules have been documented to be an internal source of silica that promotes microquartz coatings (e.g. Hendry & Trewin 1995; Aase et al. 1996). Siliceous sponge spicules, the solid ‘skeleton’ of sponges, consist of opal-A and will dissolve when exposed to higher temperatures, thereby causing supersaturation of the formation water with respect to opal-CT and quartz, resulting in nucleation of numerous small (1–5 µm) quartz crystals (Williams et al. 1985; Hendry & Trewin 1995). To predict reservoir quality it is important to understand the distribution of porosity-preserving microquartz in clastic deposits, and yet this is still poorly understood. To address this, our study presents petrographical analyses of cored sandstone sections from wells of various depositional environments, including back-barrier, estuarine, shoreface and gravity flows, as well as various present-day burial depths across the Danish Central Graben. 

Long-term performance and life cycle assessment of energy piles in three different climatic conditions

The main purpose behind the use of energy piles is to enable the exploitation of geothermal energy for meeting the heating/cooling demands of buildings in an efficient and environment-friendly manner. However, the long-term performance of energy piles in different climatic conditions, along with their actual environmental impacts, has not been fully assessed. In this paper, the results of a finite element model taking into consideration the heating and cooling demands of a reference building, and the intermittent operation of a ground source heat pump, are revealed to examine the long-term performance of energy piles. Furthermore, a life cycle assessment model is implemented to compare the environmental performance of energy piles and a group of conventional piles. The environmental enhancement provided by the adoption of a ground source heat pump system is quantified with respect to a conventional heating and cooling system. The obtained results show that (i) the energy pile system can meet the majority of the heating/cooling demands, except during the peak demands, (ii) the geothermal operation results in temperature fluctuations within the energy piles and the soil, (iii) the use of energy piles results in a significant reduction in environmental impacts in the majority of the examined cases.

Investigation of the synergy potential of oil and geothermal energy from a fluvial oil reservoir

Geothermal projects, as renewable energy projects, are not economically attractive in most places of the world at the current state of development; for this reason, subsidies are required by energy and environmental authorities in order to increase the interest in such projects. In this paper, we assess and model strategies for integration of geothermal energy with oil productions of the Moerkapelle oil field in the Netherlands. To do so, numerical simulations have been employed to analyse the feasibility of a fluvial oil reservoir for the synergy potential of oil and geothermal energy exploitation. In order to implement the simulation studies, single phase and two-phase non-isothermal fluid flow modelling are utilized for the geothermal well doublet system and for water flooding in an oil reservoir (including facies heterogeneity), respectively. A series of simulations have been conducted to investigate how hot water from a geothermal reservoir beneath a heavy oil reservoir in the fluvial sedimentary system of the West Netherlands Basin can be used for Thermal Enhanced Oil Recovery (TEOR) and geothermal energy production.This study finds that the high degree of heterogeneity in fluvial oil reservoirs could significantly affect oil recovery improvement and hence the synergy strategy. High values of a) Net to gross (N/G) b) Bottom Hole Pressure (BHP) and c) horizontal wellbore length are favourable for oil recovery. In contrast, wide horizontal wellbore spacing and high oil viscosity have an adverse effect on oil recovery enhancement. Furthermore, the results display that the enhanced oil production helps to reduce the required subsidy for a single doublet geothermal project up to 100%. Consequently, the extra amount of oil produced by utilising the geothermal energy, could make the geothermal business case independent and profitable.

Experimental Study on Temperature Change and Crack Expansion of High Temperature Granite under Different Cooling Shock Treatments

It is valuable to observe the influence of different cooling methods on the exploitation of geothermal energy and breaking hard rocks in deep geo-engineering. In this work, the effects of different cooling shock treatments on high temperature granite are discussed. First, perforated 100-mm-side cubic biotite adamellite samples were heated to four targeted temperatures (150 °C, 350 °C, 550 °C, and 750 °C). Then, anti-freeze solutions were compounded to produce the different cooling shock effects (20 °C, 0 °C, and −30 °C) by adjusting the calcium chloride solution concentration, and these anti-freeze solutions were injected rapidly into the holes to reflect the rapid cooling shock of high-temperature granite. Finally, the temperature variations and crack expansions of high-temperature granite under different cooling shock treatments were analyzed and the cooling shock cracking mechanism is discussed briefly. The main results can be summarized as: (1) The high temperature granite exposed to the cooling shock exhibited a "rapid cooling + rapid heating" change during the first 5 min. Due to the cooling shock, the total temperature was significantly lower than the natural cooling until 120 min later. (2) Below 350 °C, the macrocracking effect was not significant, and the sample reflected a certain range of uniform microcracks around the injection hole, while the macrocracks tended to be obvious above 550 °C. Moreover, as the refrigerant temperature decreased, the local distribution characteristics of the macrocracking became more obvious. (3) Based on the analysis of the dynamic heat balance, the undulation and width of the cracks around the heat balance zone were stable, but the numbers and widths of cracks near the hole wall and the side of the sample were visibly increased. This study extends our understanding of the influence of cooling shock on granite cracking.

Curie point Depth and Heat Flow Analyses over Part of Bida Basin, North Central Nigeria using Aeromagnetic Data

This study attempt to estimate the Curie point depth (CPD) and heat flow using high resolution aeromagnetic data over part of Bida basin bounded with longitude 5o00’E – 6o30’E and Latitude 8o30’N – 9o30’N with an estimated total area of 18,150 km2. We subjected the total magnetic intensity field of the study area to regional/residual separation using polynomial fitting. We divided the residual map into sixteen overlapping spectral blocks. We obtained centroid depths (Zo) and depth to top of basement (Zt)got from the plot of log of power spectrum against wave number; the centroid depth ranges from 6.61 km to 20.30 km while the depth to top of basement ranges from 1.59 km to 6.38 km. input parameter to calculate the curie depth (Zo). The CPD range from 10.88 km to 35.51 km with an average value of 23.22km. The CPD is deeper at the centre of the southern and eastern part of the study area which correspond to part of Pategi and part of Baro; and shallow at the northeastern and Northwestern part of the study area correspond to part of Mokwa and part of Bida. The geothermal gradients for the sixteen blocks range from 16.33 oCkm-1 at the centre of the southern region of the area to 53.30 oCkm-1 at the northeastern and north western region of the study area with an average of 28.98 oCkm-1. While the heat flow to range from 40.99 mWm-1 to 133.80 mWm-1 with an average value of 76.19 mWm-2. It can therefore be deduced from this study that the Southeastern, southwestern, and the northwestern part of the study area might be a good indicator of geothermal energy potential with minimum CPD, maximum geothermal gradient and heat flow since demagnetized rocks confirm a hot rock quantity in the crust that can be harnessed for geothermal energy exploitation.

Numerical simulation of simultaneous exploitation of geothermal energy and natural gas hydrates by water injection into a geothermal heat exchange well

A new geothermal energy-assisted natural gas hydrate recovery method (GEAN) that can simultaneously exploit geothermal energy and natural gas hydrates (NGHs) by injecting water into a geothermal heat exchange well was proposed in this paper. GEAN involves no hydraulic fracturing in the geothermal reservoir and, thus, avoids the fracturing cost and decreases the damage to the geothermal reservoir. Moreover, compared with conventional thermal stimulation methods, no surface fluid heating is required. Thus, GEAN produces less carbon emissions and is more environmentally friendly. A numerical simulation model was then built to investigate the heat mining rate, the along-well water temperature, and the development performance of the hydrate-bearing layer (HBL). Finally, factors that affect the heat exchange performance were analyzed. With a geothermal reservoir temperature of 135 °C and an 1800-m-long horizontal wellbore through the geothermal reservoir, it was found that the injected water, which originally had an ambient temperature of 20 °C, returns to the HBL with a temperature of up to 89.4 °C after being heated by the geothermal heat exchange well. Moreover, the heat mining rate is over 0.3 MW throughout the production process. Therefore, the feasibility of using geothermal energy to recover NGHs by the GEAN method was proven. Compared with the depressurization method, GEAN achieved an increment cumulative gas production of 63.9%. The HBL candidate with a higher geothermal gradient is preferred due to the corresponding higher temperature of the geothermal reservoir and better heat exchange performance. The optimal water injection rate and horizontal wellbore length in the geothermal reservoir are 150 m3/d and 1800 m, respectively. Performances of the heat exchange well and HBLs could be more effectively improved by properly raising the insulation level.

Towards optimisation of geothermal heat recovery: An example from the West Netherlands Basin

The Netherlands experienced the fastest European expansion of geothermal energy exploitation in the past decade. The first Dutch geothermal sites proved that Hot Sedimentary Aquifers exploitation can play an important role in a future low-carbon energy mix. In this study, we estimate that with the expansion rate of the past four years, geothermal heat production from Lower Cretaceous Hot Sedimentary Aquifers could cover up to 20% of the heat demand in the province of Zuid-Holland by 2050. Although this is a significant amount, we show in this study that only 1% of the potentially recoverable heat will be recovered by 2050. This is because of inefficient doublet deployment on a ‘first-come, first served’ basis with operational parameters that focus on objectives of small decentralised heat grid demands. Instead, similar to the common-practise approach in the hydrocarbon industry, a regional coordinated ‘masterplan’ approach could be used to increase heat recovery. Utilising numerical simulations for flow and heat transfer in the subsurface, we showed that the heat recovery efficiency could be increased by tens of percentages with such coordinated doublet deployment. Based on calculations of the Levelized Costs Of Heat for both deployment strategies, we also show that current financial support schemes do not favour heat recovery optimisation. This study emphasises that although Hot Sedimentary Aquifer resources have the potential to cover a significant part of our energy demand, a radical change in financial support schemes and legislation are required to unlock their true potential.

Modeling the flow of carbon dioxide during the drilling of oil, gas, and geothermal energy

Using carbon dioxide as a resource for enhancing the exploitation of fossil energy and geothermal energy, while realizing the geological storage of carbon dioxide, is an important direction in carbon dioxide capture, utilization, and storage studies. A carbon dioxide wellbore flow model is developed by considering the wellbore heat transmission, fluid dynamics, potential energy, and viscous friction heat. The flow characteristics of carbon dioxide and the controllable influence factors of the bottom hole pressure under different geothermal gradients are analyzed. The results indicate that the liquid carbon dioxide pumped into the drill-string enters the supercritical state at a depth of 454.8 m, and returns to the liquid state at a depth of 439.8 m in the annulus under the conditions stated here. The geothermal gradient has a significant influence on the density, pressure, and state of carbon dioxide in both the drill-string and the annulus. A larger choke pressure at the wellhead and a higher flow rate are required to obtain the same target bottom hole pressure under a high geothermal gradient. The injecting temperature has little influence on the pressure profile in the annulus. We herein establish a solid theoretical foundation for drilling technology with carbon dioxide.

Recoverable Resource Prediction of Shallow Geothermal Energy in Small Towns Using the Finite Volume Method: Taking the Central Urban Area of Danyang City, Jiangsu Province, as an Example

The ground-coupled ground-source heat pump (GSHP) system is a common method for shallow geothermal energy exploitation and utilization. GSHP has a great heat exchange rate and wide application range. In order to effectively exploit shallow geothermal energy in the central urban area of Danyang City, Jiangsu Province, based on finite volume method, it is adopted to simulate the amount of recoverable shallow geothermal energy in the study area through ground-coupled heat exchange. The simulation is conducted on the development trend of thermal transport and thermal balance in the study area from early June 2015 to the end of May 2025 to obtain the temperature distribution at different times. Under the presupposed working conditions, with the operation of a ground-coupled GSHP, thermal accumulation occurs in parts of the study area. To mitigate the problem of thermal accumulation, two schemes are proposed: (1) adding auxiliary cooling towers and (2) increasing the amount heated domestic water in spring and autumn. Both schemes mitigate thermal accumulation. For Scheme 1, the total heat supply for shallow geothermal energy in the central urban area of Danyang City in winter is 2.91 × 106 kW, and the total heat release in summer is 3.53 × 106 kW. For Scheme 2, the total heat release in summer is 3.52 × 106 kW and the total heat supply in winter is 2.90 × 106 kW. A ground-coupled GSHP system has significant applicability in the central urban area of Danyang City, where shallow geothermal energy has good exploitation prospects.

Determine In-Situ Stress and Characterize Complex Fractures in Naturally Fractured Reservoirs from Diagnostic Fracture Injection Tests

Estimation of in-situ stresses has significant applications in earth sciences and subsurface engineering, such as fault zone studies, underground CO2 sequestration, nuclear waste repositories, oil and gas reservoir development, and geothermal energy exploitation. Over the past few decades, Diagnostic Fracture Injection Tests (DFIT), which have also been referred to as Injection-Falloff Tests, Fracture Calibration Tests, and Mini-Frac Tests, have evolved into a commonly used and reliable technique to obtain in-situ stress. Simplifying assumptions used in traditional methods often lead to inaccurate estimation of the in-situ stress, even for a planar fracture geometry. When a DFIT is conducted in naturally fractured reservoirs, the stimulated natural fractures can either alter the effective reservoir permeability within the distance of investigation or interact with the hydraulic fracture to form a complex fracture geometry, this further complicates stress estimation. In this study, we present a new pressure transient model for DFIT analysis in naturally fractured reservoirs. By analyzing synthetic, laboratory and field cases, we found that fracture complexity and permeability evolution can be detected from DFIT data. Most importantly, it is shown that using established methods to pick minimum in-situ stress often lead to over or underestimates, regardless of whether the reservoir is heavily fractured or sparsely fractured. Our proposed “variable compliance method” gives a much more accurate and reliable estimation of in-situ stress in both homogenous and naturally fractured reservoirs. By combining the unique pressure signatures associated with the closure of natural fractures, a lower bound on the horizontal stress anisotropy can be estimated.

Experimental and numerical study of a vertical earth-to-air heat exchanger system integrated with annular phase change material

Vertical earth-to-air heat exchanger (VEAHE) systems have smaller land occupation and more efficient usage of geothermal energy than conventional earth-to-air heat exchanger (EAHE) systems. However, a large fluctuation in its outlet air temperature subject to ambient air temperature variations may occur, preventing it from meeting the indoor thermal comfort requirements. To address this issue, a novel VEAHE system integrated with annular phase change material (PCM) was proposed. The PCM can reduce the outlet air temperature fluctuation due to its ability to store and release energy. To evaluate its thermal performance, a numerical model was developed and validated by experimental data. The results showed a good agreement between the simulated and monitored data, with a maximum absolute relative error of 1.59% and 1.34% for the outlet air and PCM temperature, respectively. Then the validated model was applied to investigate the effects of PCM and its parameters on the system's thermal performance. Results showed that the annular PCM can decrease the outlet air temperature fluctuation of the system without PCM by 31% and 29% under air velocities of 1 m/s and 2 m/s respectively, enabling more stable outlet air temperatures to be achieved. The effect of PCM thermal conductivity depended heavily on the PCM thickness. Improving the system's thermal performance by simply increasing PCM thermal conductivity may not be an effective method, particularly when the PCM thickness was relatively small. As the PCM thickness exceeded 5 mm, an increase in the PCM thickness had a relatively small effect on the variation of outlet air temperatures. The outlet air temperature range decreased with the increase of PCM lengths, while a downward trend in the fluctuation decrease can be observed. In addition, an economic analysis of the proposed system was conducted, indicating that its static payback period was 20.8 years.

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

As the energy efficiency demands for future buildings become increasingly stringent, preliminary assessments of energy consumption are mandatory. These are possible only through numerical simulations, whose reliability crucially depends on boundary conditions. We therefore investigate their role in numerical estimates for the usage of geothermal energy, performing annual simulations of transient heat transfer for a building employing a geothermal heat pump plant and energy piles. Starting from actual measurements, we solve the heat equations in 2D and 3D using COMSOL Multiphysics and IDA-ICE, discovering a negligible impact of the multiregional ground surface boundary conditions. Moreover, we verify that the thermal mass of the soil medium induces a small vertical temperature gradient on the piles surface. We also find a roughly constant temperature on each horizontal cross-section, with nearly identical average values when either integrated over the full plane or evaluated at one single point. Calculating the yearly heating need for an entire building, we then show that the chosen upper boundary condition affects the energy balance dramatically. Using directly the pipes’ outlet temperature induces a 54% overestimation of the heat flux, while the exact ground surface temperature above the piles reduces the error to 0.03%.

Assessment of Energy Production in the Deep Carbonate Geothermal Reservoir by Wellbore-Reservoir Integrated Fluid and Heat Transport Modeling

Geothermal energy is clean and independent to the weather and seasonal changes. In China, the huge demanding of clean energy requires the geothermal energy exploitation in the reservoir with depth larger than 1000 m. Before the exploitation, it is necessary to estimate the potential geothermal energy production from deep reservoirs by numerical modeling, which provides an efficient tool for testing alternative scenarios of exploitation. We here numerically assess the energy production in a liquid-dominated middle-temperature geothermal reservoir in the city of Tianjin, China, where the heat and fluid transport in the heterogeneous reservoir and deep wellbores are calculated. It is concluded that the optimal injection/production rate of the typical geothermal doublet well system is 450 m3/h, with the distance between geothermal doublet wells of 850 m. The outflow temperature and heat extraction rate can reach 112°C and 43.5 MW, respectively. Through decreasing injection/production rate lower than 450 m3/h and optimizing layout of the injection well and production well (avoiding the high permeability zone at the interwell sector), the risk of heat breakthrough can be reduced. If the low permeability zone in the reservoir is around injection well, it usually leads to abnormal high wellhead pressure, which may be solved by stimulation technique to realize stable operation. The methodology employed in this paper can be a reference for a double-well exploitation project with similar conditions.

Fracture-initiation pressure prediction for transversely isotropic formations

Fracture-initiation pressure (FIP) is one of the most important considerations for the exploitation of petroleum and geothermal energy as well as the storage of hydrogen energy, CO2 and hydrocarbon. Wellbore pressures above the FIP maybe lead to formation fracturing, gas leakage and mud lost circulation. The effect of rock anisotropy on FIP is significant, but has not received enough attention. In this paper, the rock mechanical properties were investigated for transverse isotropic rock. Taking into account the anisotropic deformation, modulus, tensile strength and in-situ stress, a FIP prediction model was developed. The FIP models with isotropic situation, anisotropic modulus, anisotropic strength, and fully anisotropic situation were compared. The influence of anisotropic mechanical parameters, horizontal stress ratio (HSR) and pore pressure (PP) on the FIP were also analyzed. The results suggested that the transversely isotropic rock exhibits a distinct anisotropic characteristic. When the anisotropy of rock mechanical parameters was taken into account, the FIP may be higher or lower than that of isotropic model, and the amplitude of variation was about ±10%. Poisson's ratio anisotropy had a slight impact on the maximum and minimum FIPs. While the more significant the tensile strength anisotropy means the lower FIP. In addition, the influence of anisotropy on the FIP becomes increasingly pronounced with larger HSR and higher PP. The present paper can provide effective guidance to improve the drilling and hydraulic fracturing.

Dual hydrocarbon–geothermal energy exploitation: potential synergy between the production of natural gas and warm water from the subsurface

Abstract The decline of domestic natural gas production, increasing dependency on gas imports and lagging development of renewable energy production may pose serious challenges to the current high standards of secure energy supply in the Netherlands. This paper examines synergy between hydrocarbon- and geothermal exploitation as a means to reinforce energy security. The Roden gas field is used as an example to demonstrate potential delay of water breakthrough in the gas well and a resulting increase of recovered gas (up to 19%), by positioning of a geothermal doublet in the water leg of the gas field. The reservoir simulations show that the total increase of gas production primarily depends on the amount of aquifer support. An optimal configuration of gas- and geothermal wells is key to maximise gas recovery and strongly depends on the distribution of reservoir properties. The study also reveals that this option can still be beneficial for gas fields in a late stage of production. Net Present Value calculations show that the added value from the geothermal doublet on total gas production could lead to an early repayment of initial investments in the geothermal project, thereby reducing the overall financial risk. If no subsidies are taken into account, the additional profits can also be used to finance the geothermal project up to break-even level within 15 years. However, this comes with a cost as the additional profits from improved gas recovery are significantly reduced.

Review on Current Global Geothermal Energy Potentials and the Future Prospects

This paper examined the current Global Geothermal Energy Potentials and their future Prospects. The study assessed the globalgeothermal energy resources, their nature, extent of availability, estimated derivable electricity, current level of exploitation, andbusiness opportunities available. The paper presented a historical perspective of geothermal extraction for power generation,industrial process heating and cooling of buildings. In the review, different techniques for converting geothermal energy intoelectrical power had been studied. The paper also reported a summary of the global geothermal energy usage.