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Hydrothermal Numerical Simulation of Injection Operations at United Downs, Cornwall, UK

Mahmoodpour, Saeed ; Singh, Mrityunjay ; Obaje, Christian ; Tangirala, Sri Kalyan ; Reinecker, John ; Bär, Kristian ; Sass, Ingo (2022):
Hydrothermal Numerical Simulation of Injection Operations at United Downs, Cornwall, UK. (Publisher's Version)
In: Geosciences, 12 (8), MDPI, e-ISSN 2076-3263,
DOI: 10.26083/tuprints-00021865,
[Article]

Abstract

The United Downs Deep Geothermal Project (UDDGP) is designed to utilize a presumably permeable steep dipping fault damage zone (constituting the hydrothermal reservoir in a very low permeability granitic host rock) for fluid circulation and heat extraction between an injection well at 2.2 km depth (UD−2) and a production well at 5 km depth (UD−1). Soft hydraulic stimulation was performed to increase the permeability of the reservoir. Numerical simulations are performed to analyze the hydraulic stimulation results and evaluate the increase in permeability of the reservoir. Experimental and field data are used to characterize the initial reservoir static model. The reservoir is highly fractured, and two distinct fracture networks constitute the equivalent porous matrix and fault zone, respectively. Based on experimental and field data, stochastic discrete fracture networks (DFN) are developed to mimic the reservoir permeability behavior. Due to the large number of fractures involved in the stochastic model, equivalent permeability fields are calculated to create a model which is computationally feasible. Hydraulic test and stimulation data from UD−1 are used to modify the equivalent permeability field based on the observed difference between the real fractured reservoir and the stochastic DFN model. Additional hydraulic test and stimulation data from UD−2 are used to validate this modified permeability. Results reveal that the equivalent permeability field model derived from observations made in UD−1 is a good representation of the actual overall reservoir permeability, and it is useful for future studies. The numerical simulation results show the amount of permeability changes due to the soft hydraulic stimulation operation. Based on the validated permeability field, different flow rate scenarios of the petrothermal doublet and their respective pressure evolution are examined. Higher flow rates have a strong impact on the pressure evolution. Simulations are performed in the acidized enhanced permeability region to make a connection between the ongoing laboratory works on the acid injection and field response to the possible acidizing stimulation.

Item Type: Article
Erschienen: 2022
Creators: Mahmoodpour, Saeed ; Singh, Mrityunjay ; Obaje, Christian ; Tangirala, Sri Kalyan ; Reinecker, John ; Bär, Kristian ; Sass, Ingo
Origin: Secondary publication DeepGreen
Status: Publisher's Version
Title: Hydrothermal Numerical Simulation of Injection Operations at United Downs, Cornwall, UK
Language: English
Abstract:

The United Downs Deep Geothermal Project (UDDGP) is designed to utilize a presumably permeable steep dipping fault damage zone (constituting the hydrothermal reservoir in a very low permeability granitic host rock) for fluid circulation and heat extraction between an injection well at 2.2 km depth (UD−2) and a production well at 5 km depth (UD−1). Soft hydraulic stimulation was performed to increase the permeability of the reservoir. Numerical simulations are performed to analyze the hydraulic stimulation results and evaluate the increase in permeability of the reservoir. Experimental and field data are used to characterize the initial reservoir static model. The reservoir is highly fractured, and two distinct fracture networks constitute the equivalent porous matrix and fault zone, respectively. Based on experimental and field data, stochastic discrete fracture networks (DFN) are developed to mimic the reservoir permeability behavior. Due to the large number of fractures involved in the stochastic model, equivalent permeability fields are calculated to create a model which is computationally feasible. Hydraulic test and stimulation data from UD−1 are used to modify the equivalent permeability field based on the observed difference between the real fractured reservoir and the stochastic DFN model. Additional hydraulic test and stimulation data from UD−2 are used to validate this modified permeability. Results reveal that the equivalent permeability field model derived from observations made in UD−1 is a good representation of the actual overall reservoir permeability, and it is useful for future studies. The numerical simulation results show the amount of permeability changes due to the soft hydraulic stimulation operation. Based on the validated permeability field, different flow rate scenarios of the petrothermal doublet and their respective pressure evolution are examined. Higher flow rates have a strong impact on the pressure evolution. Simulations are performed in the acidized enhanced permeability region to make a connection between the ongoing laboratory works on the acid injection and field response to the possible acidizing stimulation.

Journal or Publication Title: Geosciences
Volume of the journal: 12
Issue Number: 8
Place of Publication: Darmstadt
Publisher: MDPI
Collation: 18 Seiten
Uncontrolled Keywords: United Downs, EGS, hydraulic stimulation, equivalent permeability field
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Earth Science
11 Department of Materials and Earth Sciences > Earth Science > Geothermal Science and Technology
Date Deposited: 05 Aug 2022 11:04
DOI: 10.26083/tuprints-00021865
URL / URN: https://tuprints.ulb.tu-darmstadt.de/21865
URN: urn:nbn:de:tuda-tuprints-218651
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