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.

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.

scholarly journals Geothermal Sustainability or Heat Mining?

2021 ◽  
Vol 4 (1) ◽  
pp. 15-25
Author(s):  
Ladislaus Rybach
Keyword(s):  
Heat Flow ◽  
Heat Pumps ◽  
Mineral Deposit ◽  
Sustainable Production ◽  
Production Level ◽  
Heat Extraction ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Geothermal Heat ◽  
Geothermal Resources

Heat mining” is, in fact a complete deceptive misnomer. When a mineral deposit (e.g. copper) is mined and the ore has been taken out, it will be gone forever. Not so with geothermal resources: The heat and the fluid are coming back! Namely, the heat and fluid extraction create heat sinks and hydraulic minima; around these, strong temperature and pressure gradients develop. Along the gradients, natural inflow of heat and fluid arises to replenish the deficits. The inflow from the surroundings can be strong: around borehole heat exchangers, heat flow densities of several W/m2 result, whereas terrestrial heat flow amounts only to about 50 – 100 mW/m2. The regeneration of geothermal resources after production, in other words, extraction of fluid and/or heat) is a process that runs over different timescales, depending on the kind and size of the utilization system, the production rate, and the resource characteristics. The resource renewal depends directly on the heat/fluid backflow rate. Heat, respectively fluid production from geothermal resources can be accomplished with different withdrawal rates. Although forced production is more attractive financially (with quick payback), it can nevertheless degrade the resource permanently. The longevity of the resource (and thus the sustainability of production) can be ensured by moderate production rates. The sustainable geothermal production level depends on the utilization technology as well as on the local geologic conditions. The stipulation of the sustainable production level requires specific clarifications, especially by numerical modelling, based on long-term production strategies. In general, resource regeneration proceeds asymptotically: strong at the beginning and slowing down subsequently, reaching the original conditions only after infinite time. However, regeneration to 95 % can be achieved much earlier, e.g. within the lifetime of the extraction/production system. In other words, geothermal resources may under certain circumstances may be considered as having potential regrowth, like biomass. Concerning the requirements for such sustainable production, it is convenient to consider four resource types and utilization schemes. These may be treated by numerical model simulations that consider heat extraction by geothermal heat pumps, hydrothermal aquifer, used by a doublet system for space heating, high enthalpy two-phase reservoir, tapped to generate electricity, and enhanced Geothermal Systems (EGS).

scholarly journals Conjugated Numerical Approach for Modelling DBHE in High Geothermal Gradient Environments

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6107
Author(s):  
Theo Renaud ◽  
Patrick G. Verdin ◽  
Gioia Falcone
Keyword(s):  
Heat Transfer ◽  
Geothermal Gradient ◽  
Numerical Approach ◽  
Heat Extraction ◽  
Working Fluid ◽  
Return Flow ◽  
Geothermal Systems ◽  
Cfd Modelling ◽  
Geothermal Heat ◽  
High Geothermal Gradient

Geothermal is a renewable energy source that can be untapped through various subsurface technologies. Closed geothermal well solutions, such as deep geothermal heat exchangers (DBHEs), consist of circulating a working fluid to recover the available heat, with less dependency on the local geological settings than conventional geothermal systems. This paper emphasizes a double numerical method to strengthen the assessment of DBHE performances. A computational fluid dynamics (CFD) commercial software and the 1D coupled wellbore-reservoir geothermal simulator T2Well have been used to investigate the heat transfer and fluid flow in a vertical DBHE in high geothermal gradient environments. The use of constant water properties to investigate the energy produced from DBHEs can lead to underestimating the overall heat transfer at high temperature and low mass flow rate. 2D axisymmetric CFD modelling improves the understanding of the return flow at the bottom of the DBHE, readjusting and better estimating the pressures losses commonly obtained with 1D modelling. This paper highlights the existence of convective cells located at the bottom of the DBHE internal tubing, with no significant effects due to the increase of injected water flow. Both codes are shown to constrain the numerical limitations to access the true potential of geothermal heat extraction from DBHEs in high geothermal gradient environments and demonstrate that they can be used for geothermal energy engineering applications.

Enhanced Geothermal Systems Projects and its Potential for Carbon Storage

2013 ◽  
Vol 732-733 ◽  
pp. 109-115 ◽  
Author(s):  
Chao Yin Feng
Keyword(s):  
Carbon Dioxide ◽  
Power Plants ◽  
Subsurface Water ◽  
Working Fluid ◽  
Low Permeability ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Geothermal Fields ◽  
Geological Conditions ◽  
Geothermal Wells

Enhanced Geothermal Systems represent a series of technology, which use engineering methods to improve the performance of geothermal power plant. In some geothermal fields, the rocks are in high temperature but a low permeability, or the subsurface water is scarce. In these geological conditions, cool water was injected into the geothermal wells to fracture the tight rock and create man-made reservoir for thermal exploitation. Furthermore, these engineering methods can be utilized to improve the productivity of pre-existing hydrothermal power plants. To save water and treat the global warming, using carbon dioxide instead of water as working fluid was proposed. Numerical simulation reveals that the carbon dioxide has numerous advantages over water as working fluid in the heat mining process. The precipitation caused by carbon dioxide will restore part of carbon dioxide in the rock and reduce the micro-seismicity risk.

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

Numerical investigations of CO2 and N2 miscible flow as the working fluid in enhanced geothermal systems

Energy ◽  
2020 ◽  
Vol 206 ◽  
pp. 118062
Author(s):  
Jiawei Li ◽  
Wanju Yuan ◽  
Yin Zhang ◽  
Claudia Cherubini ◽  
Alexander Scheuermann ◽  
...  
Keyword(s):  
Working Fluid ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Numerical Investigations ◽  
Miscible Flow

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

Fully coupled wellbore-reservoir modeling of geothermal heat extraction using CO 2 as the working fluid

Geothermics ◽  
2015 ◽  
Vol 53 ◽  
pp. 100-113 ◽  
Author(s):  
Lehua Pan ◽  
Barry Freifeld ◽  
Christine Doughty ◽  
Steven Zakem ◽  
Ming Sheu ◽  
...  
Keyword(s):  
Heat Extraction ◽  
Reservoir Modeling ◽  
Working Fluid ◽  
Geothermal Heat ◽  
Fully Coupled

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
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