Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data

We use Matlab 3D finite element fluid flow/transport modelling to simulate localized wellbore temperature events of order 0.05–0.1 °C logged in Fennoscandia basement rock at ~1.5 km depths. The temperature events are approximated as steady-state heat transport due to fluid draining from the crust in...

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Main Authors: Peter Leary, Peter Malin, Tero Saarno, Ilmo Kukkonen
Format: Article
Language:English
Published: MDPI AG 2017-11-01
Series:Energies
Subjects:
Online Access:https://www.mdpi.com/1996-1073/10/12/1979
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spelling doaj-95de350a6d4447759e923a31eb6f30c72020-11-25T00:17:04ZengMDPI AGEnergies1996-10732017-11-011012197910.3390/en10121979en10121979Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature DataPeter Leary0Peter Malin1Tero Saarno2Ilmo Kukkonen3Advanced Seismic Instrument & Research, 1311 Waterside, Dallas, TX 75218-4475, USAAdvanced Seismic Instrument & Research, 1311 Waterside, Dallas, TX 75218-4475, USASt1 Deep Heat Oy, Purotie 1/PL 100, 00381 Helsinki, FinlandDepartment of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, FinlandWe use Matlab 3D finite element fluid flow/transport modelling to simulate localized wellbore temperature events of order 0.05–0.1 °C logged in Fennoscandia basement rock at ~1.5 km depths. The temperature events are approximated as steady-state heat transport due to fluid draining from the crust into the wellbore via naturally occurring fracture-connectivity structures. Flow simulation is based on the empirics of spatially-correlated fracture-connectivity fluid flow widely attested by well-log, well-core, and well-production data. Matching model wellbore-centric radial temperature profiles to a 2D analytic expression for steady-state radial heat transport with Peclet number Pe ≡ r0φv0/D (r0 = wellbore radius, v0 = Darcy velocity at r0, φ = ambient porosity, D = rock-water thermal diffusivity), gives Pe ~ 10–15 for fracture-connectivity flow intersecting the well, and Pe ~ 0 for ambient crust. Darcy flow for model Pe ~ 10 at radius ~10 m from the wellbore gives permeability estimate κ ~ 0.02 Darcy for flow driven by differential fluid pressure between least principal crustal stress pore pressure and hydrostatic wellbore pressure. Model temperature event flow permeability κm ~ 0.02 Darcy is related to well-core ambient permeability κ ~ 1 µDarcy by empirical poroperm relation κm ~ κ exp(αmφ) for φ ~ 0.01 and αm ~ 1000. Our modelling of OTN1 wellbore temperature events helps assess the prospect of reactivating fossilized fracture-connectivity flow for EGS permeability stimulation of basement rock.https://www.mdpi.com/1996-1073/10/12/1979enhanced geothermal systems (EGS)crustal permeabilityfinite element flow modellingcrustal wellbore temperatureswellbore injectionwell logswell core
collection DOAJ
language English
format Article
sources DOAJ
author Peter Leary
Peter Malin
Tero Saarno
Ilmo Kukkonen
spellingShingle Peter Leary
Peter Malin
Tero Saarno
Ilmo Kukkonen
Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
Energies
enhanced geothermal systems (EGS)
crustal permeability
finite element flow modelling
crustal wellbore temperatures
wellbore injection
well logs
well core
author_facet Peter Leary
Peter Malin
Tero Saarno
Ilmo Kukkonen
author_sort Peter Leary
title Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
title_short Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
title_full Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
title_fullStr Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
title_full_unstemmed Prospects for Assessing Enhanced Geothermal System (EGS) Basement Rock Flow Stimulation by Wellbore Temperature Data
title_sort prospects for assessing enhanced geothermal system (egs) basement rock flow stimulation by wellbore temperature data
publisher MDPI AG
series Energies
issn 1996-1073
publishDate 2017-11-01
description We use Matlab 3D finite element fluid flow/transport modelling to simulate localized wellbore temperature events of order 0.05–0.1 °C logged in Fennoscandia basement rock at ~1.5 km depths. The temperature events are approximated as steady-state heat transport due to fluid draining from the crust into the wellbore via naturally occurring fracture-connectivity structures. Flow simulation is based on the empirics of spatially-correlated fracture-connectivity fluid flow widely attested by well-log, well-core, and well-production data. Matching model wellbore-centric radial temperature profiles to a 2D analytic expression for steady-state radial heat transport with Peclet number Pe ≡ r0φv0/D (r0 = wellbore radius, v0 = Darcy velocity at r0, φ = ambient porosity, D = rock-water thermal diffusivity), gives Pe ~ 10–15 for fracture-connectivity flow intersecting the well, and Pe ~ 0 for ambient crust. Darcy flow for model Pe ~ 10 at radius ~10 m from the wellbore gives permeability estimate κ ~ 0.02 Darcy for flow driven by differential fluid pressure between least principal crustal stress pore pressure and hydrostatic wellbore pressure. Model temperature event flow permeability κm ~ 0.02 Darcy is related to well-core ambient permeability κ ~ 1 µDarcy by empirical poroperm relation κm ~ κ exp(αmφ) for φ ~ 0.01 and αm ~ 1000. Our modelling of OTN1 wellbore temperature events helps assess the prospect of reactivating fossilized fracture-connectivity flow for EGS permeability stimulation of basement rock.
topic enhanced geothermal systems (EGS)
crustal permeability
finite element flow modelling
crustal wellbore temperatures
wellbore injection
well logs
well core
url https://www.mdpi.com/1996-1073/10/12/1979
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