scholarly journals Thermo-hydro-mechanical modelling study of heat extraction and flow processes in enhanced geothermal systems

2021 ◽  
Vol 54 ◽  
pp. 229-240
Author(s):  
Dejian Zhou ◽  
Alexandru Tatomir ◽  
Martin Sauter
Keyword(s):  
Production Rate ◽  
Flow Rate ◽  
Heat Production ◽  
Analytical Solutions ◽  
Pressure Difference ◽  
Heat Extraction ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Fracture Zones ◽  
Heat Production Rate

Abstract. Enhanced Geothermal Systems (EGS) are widely used in the development and application of geothermal energy production. They usually consist of two deep boreholes (well doublet) circulation systems, with hot water being abstracted, passed through a heat exchanger, and reinjected into the geothermal reservoir. Recently, simple analytical solutions have been proposed to estimate water pressure at the abstraction borehole. Nevertheless, these methods do not consider the influence of complex geometrical fracture patterns and the effects of the coupled thermal and mechanical processes. In this study, we implemented a coupled thermo-hydro-mechanical (THM) model to simulate the processes of heat extraction, reservoir deformation, and groundwater flow in the fractured rock reservoir. The THM model is validated with analytical solutions and existing published results. The results from the systems of single fracture zone and multi-fracture zones are investigated and compared. It shows that the growth of the number and spacing of fracture zones can effectively decrease the pore pressure difference between injection and abstraction wells; it also increases the production temperature at the abstraction, the service life-spans, and heat production rate of the geothermal reservoirs. Furthermore, the sensitivity analysis on the flow rate is also implemented. It is observed that a larger flow rate leads to a higher abstraction temperature and heat production rate at the end of the simulation, but the pressure difference may become lower.

Convective heat transfer of water flowing in intersected rock fractures for enhanced geothermal extraction

2021 ◽  
Author(s):  
Yuedu chen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Heat Production ◽  
Three Dimensional ◽  
Heat Extraction ◽  
Rock Fractures ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Dead End

<p>Numerous intersected rock fractures constitute the fracture network in enhanced geothermal systems. The complicated convective heat transfer behavior in intersected fractures is critical to the heat recovery in fractured geothermal reservoirs. A series of three-dimensional intersected fracture models are constructed to perform the flow-through heat transfer simulations. The geometries effects of dead-end fractures on the heat transfer are evaluated in terms of intersected angles, apertures, lengths, and the connectivity. The results indicate that annular streamlines appear in the rough dead-end fracture and cause an ellipsoidal distribution of the cold front. Compared to the steady flow in plate dead-end fractures, the fluid flow formed in the rough dead-end fracture enhances the heat transfer. Both the outlet water temperature T<sub>out</sub> and heat production Q present the largest when the intersected angle is 90°. A larger intersected angle and longer length extension of the intersected dead-end fracture, raising T<sub>out</sub> and Q, are beneficial to the heat production, while increasing the aperture is ineffective. Solely increasing numbers of dead-end fractures poses a little increase on T<sub>out</sub> and Q. More significant heat extraction is obtained through connecting these dead-end fractures with the main flow fracture forming the flow network.</p>

Analysis of influencing factors of heat extraction from enhanced geothermal systems considering water losses

Energy ◽  
2016 ◽  
Vol 115 ◽  
pp. 274-288 ◽  
Author(s):  
Wen-Long Cheng ◽  
Chang-Long Wang ◽  
Yong-Le Nian ◽  
Bing-Bing Han ◽  
Jian Liu
Keyword(s):  
Influencing Factors ◽  
Heat Extraction ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Water Losses

Anthropogenic Heat Release Into the Environment

2012 ◽  
Author(s):  
Kaufui V. Wong ◽  
Yading Dai ◽  
Brian Paul
Keyword(s):  
Climate Change ◽  
Solar Radiation ◽  
Production Rate ◽  
Heat Production ◽  
Domestic Animals ◽  
Anthropogenic Heat ◽  
Net Energy ◽  
The Earth ◽  
Heat Production Rate ◽  
Energy Dissipated

This work is intended to systematically study an inventory of the anthropogenic heat produced. This research strives to present a better estimate of the energy generated by humans and human activities, and compare this estimate to the significant energy quantity with respect to climate change. Because the Top of Atmosphere (TOA) net energy flux was found to be 0.85±0.15 W/m2 the planet is out of energy balance, as studied by the group from NASA in 2005. The Earth is estimated to gain 431 TW from this energy imbalance. This number is the significant heat quantity to consider when studying global climate change, and not the 78,300 TW, the absorbed part of the primary solar radiation reaching the Earth’s surface, as commonly cited and used at present in the literature. Based on energy supplied to the boilers (in the Rankine cycle) of at least 13 TW, body energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 15.26 TW or 3.5% of the energy gain by the Earth. Based on world energy consumption and the energy dissipated by 7 billion people and their domestic animals, the value of the total world anthropogenic heat production rate is 19.7 TW or about 5% of the energy gain by the Earth. These numbers are significantly different from 13 TW. More importantly, the figures are 3.5 to 5% of the net energy gained by the Earth, and hence significant. The quantity is not 0.017% of the absorbed part of the main solar radiation reaching the Earth’s surface and negligible.

Cell metabolic activity in acromegaly: a microcalorimetric study of lymphocyte metabolism

1990 ◽  
Vol 122 (4) ◽  
pp. 422-426 ◽  
Author(s):  
Stig Valdemarsson ◽  
Julie Ikomi-Kumm ◽  
Mario Monti
Keyword(s):  
Growth Hormone ◽  
Production Rate ◽  
Metabolic Activity ◽  
Heat Production ◽  
Disease Process ◽  
Serum Levels ◽  
Clinical Activity ◽  
Clinical Impression ◽  
Cell Metabolic Activity ◽  
Heat Production Rate

Abstract. A discrepancy between the clinical impression of disease activity and basal serum levels of growth hormone is often seen in patients with acromegaly. A slightly better relation has been found to serum levels of IGF-I, but a technique for evaluation of cell metabolic activity in this disease is still missing. For this purpose we used microcalorimetry to determine heat production rate in lymphocytes from 15 patients with acromegaly. The mean heat production rate was 2.90±0.15 pW/cell, significantly higher than in 13 healthy subjects, 2.31±0.12 pW/cell (p<0.01). Heat production rates did not correlate significantly with basal growth hormone levels, but increased, in a statistically significant manner (p<0.001), in parallel with the score index used to evaluate the clinical activity of the disease. Using the technique of microcalorimetry we could thus demonstrate an increased metabolic activity at a cellular level in patients with acromegaly, a finding that is in accordance with the view that an increased cell metabolic activity is a component of the disease process in acromegaly.

Simulation of heat extraction from CO2-based enhanced geothermal systems considering CO2 sequestration

Energy ◽  
2018 ◽  
Vol 142 ◽  
pp. 157-167 ◽  
Author(s):  
Chang-Long Wang ◽  
Wen-Long Cheng ◽  
Yong-Le Nian ◽  
Lei Yang ◽  
Bing-Bing Han ◽  
...  
Keyword(s):  
Co2 Sequestration ◽  
Heat Extraction ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems

scholarly journals Design, modeling, and evaluation of a doublet heat extraction model in enhanced geothermal systems

2017 ◽  
Vol 105 ◽  
pp. 232-247 ◽  
Author(s):  
Yidong Xia ◽  
Mitchell Plummer ◽  
Earl Mattson ◽  
Robert Podgorney ◽  
Ahmad Ghassemi
Keyword(s):  
Heat Extraction ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Extraction Model

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 Longevity of Enhanced Geothermal Systems with Brine Circulation in Hydraulically Fractured Hydrocarbon Wells

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 63
Author(s):  
Zuo ◽  
Weijermars
Keyword(s):  
Limit State ◽  
Extraction Process ◽  
Heat Extraction ◽  
Working Fluid ◽  
Heat Equations ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Geothermal Heat ◽  
Horizontal Fracture ◽  
Rock Temperature

A simple, semi-analytical heat extraction model is presented for hydraulically fractured dry reservoirs containing two subparallel horizontal wells, connected by a horizontal fracture channel, using injected brine as the working fluid. Heat equations are used to quantify the heat conduction between fracture walls and circulating brine. The brine temperature profiles are calculated for different combinations of fracture widths, working fluid circulation rates, and initial fracture wall temperatures. The longevity of the geothermal heat extraction process is assessed for a range of working fluid injection rates. Importantly, dry geothermal reservoirs will not recharge heat by the geothermal flux on the time scale of any commercial heat extraction project. A production plan is proposed, with periodic brine circulation maintained in a diurnal schedule with 8 h active production alternating with 16 h of pump switched off. A quasi-steady state is achieved after both the brine temperature and rock temperature converge to a limit state allowing fracture-wall reheating by conduction from the rock interior in the diurnal production schedule. The results of this study could serve as a fast tool for assisting the planning phase of geothermal reservoir design as well as for operational monitoring and management.

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