Enhanced Geothermal Systems – Promises and Challenges

2021 ◽  
Vol 11 (2) ◽  
pp. 333-346
Author(s):  
Anirbid Sircar ◽  
Krishna Solanki ◽  
Namrata Bist ◽  
Kriti Yadav
Keyword(s):  
Reservoir Characterization ◽  
Control Measures ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Fluid Saturation ◽  
Reservoir Permeability ◽  
Transmission Fluid ◽  
Advanced Drilling ◽  
And Control

Geothermal energy plays a very important role in the energy basket of the world. However, understanding the geothermal hotspots and exploiting the same from deep reservoirs, by using advanced drilling technologies, is a key challenge. This study focuses on reservoirs at a depth greater than 3 km and temperatures more than 150°C. These resources are qualified as Enhanced Geothermal System (EGS). Artificially induced technologies are employed to enhance the reservoir permeability and fluid saturation. The present study concentrates on EGS resources, their types, technologies employed to extract energy and their applications in improving power generation. Studies on fracture stimulation using hydraulic fracturing and hydro shearing are also evaluated. The associated micro-seismic events and control measures for the same are discussed in this study. Various simulators for reservoir characterization and description are also analyzed and presented. Controlled fluid injection and super critical CO2 as heat transmission fluid are described for the benefit of the readers. The advantages of using CO2 over water and its role in reducing the carbon footprint are brought out in this paper for further studies.

Heat Flux to Fluids Within a Rock Fracture in a Geothermal System

2010 ◽  
Author(s):  
Dustin Crandall ◽  
Goodarz Ahmadi ◽  
Grant Bromhal
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Numerical Study ◽  
Rock Fracture ◽  
Working Fluid ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Ct Scanner

Fractures in rocks enable the motion of fluids through the large, hot geologic formations of geothermal reservoirs. The heat transfer from the surrounding rock mass to the fluid flowing through a fracture depends on the geometry of the fracture, the fluid/solid properties, and the flow rate through the fracture. A numerical study was conducted to evaluate the changes in heat transfer to the fluid flowing through a rock fracture with changes in the flow rate. The aperture distribution of the rock fracture, originally created within Berea sandstone and imaged using a CT-scanner, is well described by a Gaussian distribution and has a mean aperture of approximately 0.6 mm. Water was used as the working fluid, enabling an evaluation of the efficiency of heat flux to the fluid along the flow path of a hot dry geothermal system. As the flow through the fracture was increased to a Reynolds number greater than 2300 the effect of channeling through large aperture regions within the fracture were observed to become increasingly important. For the fastest flows modeled the heat flux to the working fluids was reduced due to a shorter residence time of the fluid in the fracture. Understanding what conditions can maximize the amount of energy obtained from fractures within a hot dry geologic field can improve the operation and long-term viability of enhanced geothermal systems.

scholarly journals Analysis of Hydraulic Fracturing and Reservoir Performance in Enhanced Geothermal Systems

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Mengying Li ◽  
Noam Lior
Keyword(s):  
Hydraulic Fracturing ◽  
Flow Direction ◽  
Fractured Reservoirs ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Fracture Width ◽  
Reservoir Performance ◽  
Flow And Heat Transfer ◽  
Engineered Geothermal System

Analyses of fracturing and thermal performance of fractured reservoirs in engineered geothermal system (EGS) are extended from a depth of 5 km to 10 km, and models for flow and heat transfer in EGS are improved. Effects of the geofluid flow direction choice, distance between fractures, fracture width, permeability, radius, and number of fractures, on reservoir heat drawdown time are computed. The number of fractures and fracture radius for desired reservoir thermal drawdown rates are recommended. A simplified model for reservoir hydraulic fracturing energy consumption is developed, indicating it to be 51.8–99.6 MJ per m3 fracture for depths of 5–10 km.

Time-lapse magnetotelluric monitoring of an enhanced geothermal system

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. B121-B130 ◽  
Author(s):  
Jared R. Peacock ◽  
Stephan Thiel ◽  
Graham S. Heinson ◽  
Peter Reid
Keyword(s):  
South Australia ◽  
Time Lapse ◽  
Fault System ◽  
Fluid Distribution ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Hydraulic Stimulation ◽  
Microseismic Data ◽  
Before And After

Realization of enhanced geothermal systems (EGSs) prescribes the need for novel methods to monitor subsurface fracture connectivity and fluid distribution. Magnetotellurics (MT) is a passive electromagnetic (EM) method sensitive to electrical conductivity contrasts as a function of depth, specifically hot saline fluids in a resistive porous media. In July 2011, an EGS fluid injection at 3.6-km depth near Paralana, South Australia, was monitored by comparing repeated MT surveys before and after hydraulic stimulation. An observable coherent change above measurement error in the MT response was present and causal, in that variations in phase predict variations in apparent resistivity. Phase tensor residuals proved the most useful representation for characterizing alterations in subsurface resistivity structure, whereas resistivity tensor residuals aided in determining the sign and amplitude of resistivity variations. These two tensor representations of the residual MT response suggested fluids migrated toward the northeast of the injection well along an existing fault system trending north-northeast. Forward modeling and concurrent microseismic data support these results, although microseismic data suggest fractures opened along two existing fracture networks trending north-northeast and northeast. This exemplifies the need to use EM methods for monitoring fluid injections due to their sensitivity to conductivity contrasts.

scholarly journals A Semi-Analytical Method for Three-Dimensional Heat Transfer in Multi-Fracture Enhanced Geothermal Systems

Energies ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1211 ◽  
Author(s):  
Dongdong Liu ◽  
Yanyong Xiang
Keyword(s):  
Analytical Method ◽  
Three Dimensional ◽  
Heat Extraction ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Rock Matrix ◽  
Multiple Fractures ◽  
One Dimensional ◽  
Production Temperature

Multiple fractures have been proposed for improving the heat extracted from an enhanced geothermal system (EGS). For calculating the production temperature of a multi-fracture EGS, previous analytical or semi-analytical methods have all been based on an infinite scale of fractures and one-dimensional conduction in the rock matrix. Here, a temporal semi-analytical method is presented in which finite-scale fractures and three-dimensional conduction in the rock matrix are both considered. Firstly, the developed model was validated by comparing it with the analytical solution, which only considers one-dimensional conduction in the rock matrix. Then, the temporal semi-analytical method was used to predict the production temperature in order to investigate the effects of fracture spacing and fracture number on the response of an EGS with a constant total injection rate. The results demonstrate that enlarging the spacing between fractures and increasing the number of fractures can both improve the heat extraction; however, the latter approach is much more effective than the former. In addition, the temporal semi-analytical method is applicable for optimizing the design of an EGS with multiple fractures located equidistantly or non-equidistantly.

scholarly journals Thermo-Poroelastic Analysis of Induced Seismicity at the Basel Enhanced Geothermal System

2019 ◽  
Vol 11 (24) ◽  
pp. 6904 ◽  
Author(s):  
Sandro Andrés ◽  
David Santillán ◽  
Juan Carlos Mosquera ◽  
Luis Cueto-Felgueroso
Keyword(s):  
Rock Fracture ◽  
Green Energy ◽  
Fault Reactivation ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Earthquake Triggering ◽  
Hydraulic Stimulation ◽  
Frictional Contacts ◽  
Stimulation Of

Geothermal energy has emerged as an alternative to ensure a green energy supply while tackling climate change. Geothermal systems extract the heat stored in the Earth’s crust by warming up water, but the low rock permeability at exploitation depths may require the hydraulic stimulation of the rock fracture network. Enhanced Geothermal Systems (EGS) employ techniques such as hydro-shearing and hydro-fracturing for that purpose, but their use promotes anthropogenic earthquakes induced by the injection or extraction of fluids. This work addresses this problem through developing a computational 3D model to explore fault reactivation and evaluating the potential for earthquake triggering at preexisting geological faults. These are included in the model as frictional contacts that allow the relative displacement between both of its sides, governed by rate-and-state friction laws and fully coupled with thermo-hydro-mechanical equations. We apply our methodology to the Basel project, employing the on-site parameters and conditions. Our results demonstrate that earthquakes which occurred in December 2006 in Basel (Switzerland) are compatible with the geomechanical and frictional consequences of the hydraulic stimulation of the rock mass. The application of our model also shows that it can be useful for predicting fault reactivation and engineering injection protocols for managing the safe and sustainable operation of EGS.

scholarly journals Evaluation of CO2-Fluid-Rock Interaction in Enhanced Geothermal Systems: Field-Scale Geochemical Simulations

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Feng Pan ◽  
Brian J. McPherson ◽  
John Kaszuba
Keyword(s):  
High Pressures ◽  
Mineral Dissolution ◽  
Heat Extraction ◽  
Working Fluid ◽  
Enhanced Geothermal Systems ◽  
Geochemical Processes ◽  
Geothermal Systems ◽  
Rock Interaction ◽  
Transmission Fluid ◽  
Dissolution And Precipitation

Recent studies suggest that using supercritical CO2 (scCO2) instead of water as a heat transmission fluid in Enhanced Geothermal Systems (EGS) may improve energy extraction. While CO2-fluid-rock interactions at “typical” temperatures and pressures of subsurface reservoirs are fairly well known, such understanding for the elevated conditions of EGS is relatively unresolved. Geochemical impacts of CO2 as a working fluid (“CO2-EGS”) compared to those for water as a working fluid (H2O-EGS) are needed. The primary objectives of this study are (1) constraining geochemical processes associated with CO2-fluid-rock interactions under the high pressures and temperatures of a typical CO2-EGS site and (2) comparing geochemical impacts of CO2-EGS to geochemical impacts of H2O-EGS. The St. John’s Dome CO2-EGS research site in Arizona was adopted as a case study. A 3D model of the site was developed. Net heat extraction and mass flow production rates for CO2-EGS were larger compared to H2O-EGS, suggesting that using scCO2 as a working fluid may enhance EGS heat extraction. More aqueous CO2 accumulates within upper- and lower-lying layers than in the injection/production layers, reducing pH values and leading to increased dissolution and precipitation of minerals in those upper and lower layers. Dissolution of oligoclase for water as a working fluid shows smaller magnitude in rates and different distributions in profile than those for scCO2 as a working fluid. It indicates that geochemical processes of scCO2-rock interaction have significant effects on mineral dissolution and precipitation in magnitudes and distributions.

Fluid Flow Through Branched Channels in a Fracture Plane in an Enhanced Geothermal System

2012 ◽  
Author(s):  
Rosemarie Mohais ◽  
Chaoshui Xu ◽  
Peter A. Dowd
Keyword(s):  
Fluid Flow ◽  
Fractal Theory ◽  
Maximum Flow ◽  
Constructal Theory ◽  
Fracture Plane ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Simple Relationship ◽  
Geothermal Systems ◽  
Heterogeneous Rock

Fluid flow in Enhanced Geothermal Systems (EGS) occurs primarily through fractures which are embedded in an almost impermeable granite rock matrix. Experimental and numerical studies have shown that flow in fractures exhibits channeling effects; this means that flow occurs along preferred pathways, most likely the paths of least resistance. There has been evidence to date of dendritic and star-like patterns in granite and as a result, authors have used fractal theory in order to address flow phenomena in these patterns. The application of Bejan’s Constructal theory to this problem however has never been attempted. We base our model on dendritic patterns of flow paths in heterogeneous rock fractures. Flow enters into a main channel which bifurcates into daughter channels of unique dimensions of length and height. We study these parameters for consecutive channels in the flow path and show that for minimization of resistance to flow within a plane using area and volume constraints for a T-shaped channel, a simple relationship holds for the ratios of lengths and heights which will enable maximum flow for this configuration.

scholarly journals A Reference Thermal-Hydrologic-Mechanical Native State Model of the Utah FORGE Enhanced Geothermal Site

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4758
Author(s):  
Robert Podgorney ◽  
Aleta Finnila ◽  
Stuart Simmons ◽  
John McLennan
Keyword(s):  
Great Basin ◽  
Scientific Discovery ◽  
Critical Role ◽  
Department Of Energy ◽  
State Model ◽  
Reservoir Rock ◽  
Geothermal System ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Native State

The Frontier Observatory for Research in Geothermal Energy (FORGE) site is a multi-year initiative funded by the U.S. Department of Energy for enhanced geothermal system research and development. The site is located on the margin of the Great Basin near the town of Milford, Utah. Work has so far resulted in the compilation of a large amount of subsurface data which have been used to improve the geologic understanding of the site. Based on the compiled data, a three-dimensional geologic model describing the structure, composition, permeability, and temperature at the Utah FORGE site was developed. A deep exploratory well (Well 58-32) and numerous tests conducted therein provide information on reservoir rock type, temperature, stress, permeability, etc. Modeling and simulation will play a critical role at the site and need to be considered as a general scientific discovery tool to elucidate the behavior of enhanced geothermal systems and as a deterministic (or stochastic) tool to plan and predict specific activities. This paper will present the development of a reference native state model and the calibration of the model to the reservoir pressure, temperature, and stress measured in Well 58-32.

Knowledge and Awareness of Dengue Fever

2018 ◽  
pp. 219-222
Author(s):  
Y. Arockia Suganthi ◽  
Chitra K. ◽  
J. Magelin Mary
Keyword(s):  
Dengue Fever ◽  
Prevention And Control ◽  
Control Measures ◽  
Infection Transmission ◽  
Standard Guideline ◽  
The World ◽  
Different Types ◽  
Prevention And Control Measures ◽  
Dengue Prevention ◽  
And Control

Dengue fever is a painful mosquito-borne infection caused by different types of virus in various localities of the world. There is no particular medicine or vaccine to treat person suffering from dengue fever. Dengue viruses are transmitted by the bite of female Aedes (Ae) mosquitoes. Dengue fever viruses are mainly transmitted by Aedes which can be active in tropical or subtropical climates. Aedes Aegypti is the key step to avoid infection transmission to save millions of people in all over the world. This paper provides a standard guideline in the planning of dengue prevention and control measures. At the same time gives the priorities including clinical management and hospitalized dengue patients have to address essentially.

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