Impact of fracture shear dilation on long-term heat extraction in Enhanced Geothermal Systems: Insights from a fully-coupled thermo-hydro-mechanical simulation

Geothermics ◽  
2021 ◽  
Vol 96 ◽  
pp. 102216
Author(s):  
Xu Zhang ◽  
Zhaoqin Huang ◽  
Qinghua Lei ◽  
Jun Yao ◽  
Liang Gong ◽  
...  
2020 ◽  
Author(s):  
Dejian Zhou ◽  
Alexandru Tatomir ◽  
Martin Sauter

<p>Enhanced Geothermal Systems (EGS) are widely used in the development and application of geothermal energy. They usually consist of two parallel deep boreholes, where cold water is injected into one borehole and abstracted at the second one after being heated when passing through the fractured network system. Recently, simple analytical solutions have been proposed to estimate the water pressure at the output. Nevertheless, these methods do not take into account the influences of the coupled thermal and mechanical processes. In this research study we build a fully coupled Thermal – Hydro-mechanical model (THM model) to simulate the processes of heat extraction, deformation and water flow in the nearby fractured rock formations. The influences of single thermal – hydraulic and mechanical – hydraulic effects were compared with the fully coupled and decoupled results, showing that temperature influences mostly the water pressure in the second borehole, compared with temperature. The mechanical effect alone has little influences on the water pressure. A sensitive analysis was also conducted to study which parameters affect the simulation results the most. It was shown that the initial permeability and temperature are playing the main roles in this simulation.</p>


Energy ◽  
2016 ◽  
Vol 115 ◽  
pp. 274-288 ◽  
Author(s):  
Wen-Long Cheng ◽  
Chang-Long Wang ◽  
Yong-Le Nian ◽  
Bing-Bing Han ◽  
Jian Liu

Energy ◽  
2018 ◽  
Vol 142 ◽  
pp. 157-167 ◽  
Author(s):  
Chang-Long Wang ◽  
Wen-Long Cheng ◽  
Yong-Le Nian ◽  
Lei Yang ◽  
Bing-Bing Han ◽  
...  

2017 ◽  
Vol 105 ◽  
pp. 232-247 ◽  
Author(s):  
Yidong Xia ◽  
Mitchell Plummer ◽  
Earl Mattson ◽  
Robert Podgorney ◽  
Ahmad Ghassemi

2021 ◽  
Vol 54 ◽  
pp. 229-240
Author(s):  
Dejian Zhou ◽  
Alexandru Tatomir ◽  
Martin Sauter

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.


Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 63
Author(s):  
Zuo ◽  
Weijermars

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.


2021 ◽  
Vol 40 (4) ◽  
pp. 245-253
Author(s):  
Margariete Malenda ◽  
Tiziana Vanorio ◽  
Saied Mighani ◽  
Jihui Ding ◽  
Jaehong Chung

The transition to a low-carbon future involves every component of our productive life — from the energy we use, to the buildings we construct, to the materials we use in our daily lives. Realistically, the shift onto a low-carbon path cannot happen instantly but requires adopting short- and long-term solutions while assessing whether the solutions work in the physical world in which we live. In the short term, incremental technological improvements, such as transitioning to energy sources like natural gas, have the potential to yield immediate benefit to air quality and pollution. In the mid and long term, however, more far-reaching decarbonization technologies must be pursued to achieve game-changing outcomes. In the geosciences realm, leading technologies span from cleaner energy solutions to exploring alternative earth-inspired materials and processes. These include CO2 storage in geologic disposal sites along with its reuse for material manufacturing, the development of enhanced geothermal systems expanding the use of geothermal energy, and adapting subsurface processes to engineer greener processes and materials through geomimicry. In this landscape, experimentation and rock physics are at the crux of understanding rock-fluid processes and are the premise and foundation of decarbonizing our future. All of these applications require experimentation for wider public acceptance to avoid hasty solutions that are counterproductive. The cross-disciplinary nature of each endeavor is pivotal in assessing how processes induced by fluids, their chemistry, and thermal capacity affect the physical and mechanical properties of treated environments. This paper provides an account of the role that rock physics will play in leveraging knowledge across the nanosciences to underpin our path to a decarbonized future through chemical and thermal stimulation practices, solid-CO2 reactions, and engineering processes that manipulate geology to produce materials with functional properties.


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