Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling

Quan Gan, Derek Elsworth

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

In this work, a stimulation then heat production optimization strategy is presented for prototypical EGS geothermal reservoirs by comparing conventional stimulation-then-production scenarios against revised stimulation schedules. A generic reservoir is selected with an initial permeability in the range of 10-17-10-16 m2, fracture density of ~0.09 m-1 and fractures oriented such that either none, one, or both sets of fractures are critically stressed. For a given reservoir with a pre-existing fracture network, two parallel manifolds are stimulated that are analogous to horizontal wells that allow a uniform sweep of fluids between the zones. The enhanced connectivity that develops between the injection zone and the production zone significantly enhances the heat sweep efficiency, while simultaneously increasing the fluid flux rate at the production well. For a 10 m deep section of reservoir the resulting electric power production reaches a maximum of 14.5 MWe and is maintained over 10 years yielding cumulative energy recoveries that are a factor of 1.9 higher than for standard stimulation. Sensitivity analyses for varied fracture orientations and stimulation directions reveal that the direction of such manifolds used in the stimulation should be aligned closely with the orientation of the major principal stress, in order to create the maximum connectivity. When the fractures are less prone to fail, the output electric power is reduced by a decrease in the fluid flux rate to the production well.

Original languageEnglish (US)
Pages (from-to)131-142
Number of pages12
JournalGeothermics
Volume62
DOIs
StatePublished - Jul 1 2016

Fingerprint

fracture network
well
modeling
fluid
connectivity
fracture orientation
Fluids
heat production
Fluxes
Horizontal wells
permeability
Recovery
rate
electric power

All Science Journal Classification (ASJC) codes

  • Renewable Energy, Sustainability and the Environment
  • Geotechnical Engineering and Engineering Geology
  • Geology

Cite this

@article{2bf200a0cf8c4804bf3c99a1cb337111,
title = "Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling",
abstract = "In this work, a stimulation then heat production optimization strategy is presented for prototypical EGS geothermal reservoirs by comparing conventional stimulation-then-production scenarios against revised stimulation schedules. A generic reservoir is selected with an initial permeability in the range of 10-17-10-16 m2, fracture density of ~0.09 m-1 and fractures oriented such that either none, one, or both sets of fractures are critically stressed. For a given reservoir with a pre-existing fracture network, two parallel manifolds are stimulated that are analogous to horizontal wells that allow a uniform sweep of fluids between the zones. The enhanced connectivity that develops between the injection zone and the production zone significantly enhances the heat sweep efficiency, while simultaneously increasing the fluid flux rate at the production well. For a 10 m deep section of reservoir the resulting electric power production reaches a maximum of 14.5 MWe and is maintained over 10 years yielding cumulative energy recoveries that are a factor of 1.9 higher than for standard stimulation. Sensitivity analyses for varied fracture orientations and stimulation directions reveal that the direction of such manifolds used in the stimulation should be aligned closely with the orientation of the major principal stress, in order to create the maximum connectivity. When the fractures are less prone to fail, the output electric power is reduced by a decrease in the fluid flux rate to the production well.",
author = "Quan Gan and Derek Elsworth",
year = "2016",
month = "7",
day = "1",
doi = "10.1016/j.geothermics.2016.04.009",
language = "English (US)",
volume = "62",
pages = "131--142",
journal = "Geothermics",
issn = "0375-6505",
publisher = "Elsevier Limited",

}

Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling. / Gan, Quan; Elsworth, Derek.

In: Geothermics, Vol. 62, 01.07.2016, p. 131-142.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Production optimization in fractured geothermal reservoirs by coupled discrete fracture network modeling

AU - Gan, Quan

AU - Elsworth, Derek

PY - 2016/7/1

Y1 - 2016/7/1

N2 - In this work, a stimulation then heat production optimization strategy is presented for prototypical EGS geothermal reservoirs by comparing conventional stimulation-then-production scenarios against revised stimulation schedules. A generic reservoir is selected with an initial permeability in the range of 10-17-10-16 m2, fracture density of ~0.09 m-1 and fractures oriented such that either none, one, or both sets of fractures are critically stressed. For a given reservoir with a pre-existing fracture network, two parallel manifolds are stimulated that are analogous to horizontal wells that allow a uniform sweep of fluids between the zones. The enhanced connectivity that develops between the injection zone and the production zone significantly enhances the heat sweep efficiency, while simultaneously increasing the fluid flux rate at the production well. For a 10 m deep section of reservoir the resulting electric power production reaches a maximum of 14.5 MWe and is maintained over 10 years yielding cumulative energy recoveries that are a factor of 1.9 higher than for standard stimulation. Sensitivity analyses for varied fracture orientations and stimulation directions reveal that the direction of such manifolds used in the stimulation should be aligned closely with the orientation of the major principal stress, in order to create the maximum connectivity. When the fractures are less prone to fail, the output electric power is reduced by a decrease in the fluid flux rate to the production well.

AB - In this work, a stimulation then heat production optimization strategy is presented for prototypical EGS geothermal reservoirs by comparing conventional stimulation-then-production scenarios against revised stimulation schedules. A generic reservoir is selected with an initial permeability in the range of 10-17-10-16 m2, fracture density of ~0.09 m-1 and fractures oriented such that either none, one, or both sets of fractures are critically stressed. For a given reservoir with a pre-existing fracture network, two parallel manifolds are stimulated that are analogous to horizontal wells that allow a uniform sweep of fluids between the zones. The enhanced connectivity that develops between the injection zone and the production zone significantly enhances the heat sweep efficiency, while simultaneously increasing the fluid flux rate at the production well. For a 10 m deep section of reservoir the resulting electric power production reaches a maximum of 14.5 MWe and is maintained over 10 years yielding cumulative energy recoveries that are a factor of 1.9 higher than for standard stimulation. Sensitivity analyses for varied fracture orientations and stimulation directions reveal that the direction of such manifolds used in the stimulation should be aligned closely with the orientation of the major principal stress, in order to create the maximum connectivity. When the fractures are less prone to fail, the output electric power is reduced by a decrease in the fluid flux rate to the production well.

UR - http://www.scopus.com/inward/record.url?scp=84973131596&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84973131596&partnerID=8YFLogxK

U2 - 10.1016/j.geothermics.2016.04.009

DO - 10.1016/j.geothermics.2016.04.009

M3 - Article

AN - SCOPUS:84973131596

VL - 62

SP - 131

EP - 142

JO - Geothermics

JF - Geothermics

SN - 0375-6505

ER -