Analysis of fluid injection-induced fault reactivation and seismic slip in geothermal reservoirs

Quan Gan, Derek Elsworth

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

We explore the issue of fault reactivation induced in enhanced geothermal systems by fluid injection. Specifically, we investigate the role of late stage activation by thermal drawdown. A Thermal-Hydrological-Mechanical simulator incorporating a ubiquitous joint constitutive model is used to systematically simulate the seismic slip of an embedded critically stressed strike-slip fault. We examine the effects of both pore pressure perturbation and thermal shrinkage stress on the magnitude of the resulting events and timing. We analyze the sensitivity of event magnitude and timing to changes in the permeability of the fault and fractured host, fracture spacing, injection temperature, and fault stress obliquity. From this we determine that (1) the fault permeability does not affect the timing of the events nor their size, since fluid transmission and cooling rate are controlled by the permeability of the host formation. (2) When the fractured medium permeability is reduced (from 10-13 to 10 -16 m2), the timing of the event is proportionately delayed (by a corresponding 3 orders of magnitude). (3) Injection temperature only influences the magnitude but not the timing of the secondary thermal event. The larger the temperature differences between that of the injected fluid and the ambient rock, the larger the magnitude of the secondary slip event. (4) For equivalent permeabilities, changing the fracture spacing (10 m-50 m-100 m) primarily influences the rate of heat energy transfer and thermal drawdown within the reservoir. Smaller spacing between fractures results in more rapid thermal recovery but does not significantly influence the timing of the secondary thermal rupture.

Original languageEnglish (US)
Pages (from-to)3340-3353
Number of pages14
JournalJournal of Geophysical Research: Solid Earth
Volume119
Issue number4
DOIs
StatePublished - Apr 2014

Fingerprint

fluid injection
reactivation
slip
time measurement
permeability
Fluids
spacing
drawdown
fractured medium
fluid
injection
temperature
obliquity
strike-slip fault
fluids
pore pressure
Strike-slip faults
simulator
rupture
shrinkage

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

Cite this

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abstract = "We explore the issue of fault reactivation induced in enhanced geothermal systems by fluid injection. Specifically, we investigate the role of late stage activation by thermal drawdown. A Thermal-Hydrological-Mechanical simulator incorporating a ubiquitous joint constitutive model is used to systematically simulate the seismic slip of an embedded critically stressed strike-slip fault. We examine the effects of both pore pressure perturbation and thermal shrinkage stress on the magnitude of the resulting events and timing. We analyze the sensitivity of event magnitude and timing to changes in the permeability of the fault and fractured host, fracture spacing, injection temperature, and fault stress obliquity. From this we determine that (1) the fault permeability does not affect the timing of the events nor their size, since fluid transmission and cooling rate are controlled by the permeability of the host formation. (2) When the fractured medium permeability is reduced (from 10-13 to 10 -16 m2), the timing of the event is proportionately delayed (by a corresponding 3 orders of magnitude). (3) Injection temperature only influences the magnitude but not the timing of the secondary thermal event. The larger the temperature differences between that of the injected fluid and the ambient rock, the larger the magnitude of the secondary slip event. (4) For equivalent permeabilities, changing the fracture spacing (10 m-50 m-100 m) primarily influences the rate of heat energy transfer and thermal drawdown within the reservoir. Smaller spacing between fractures results in more rapid thermal recovery but does not significantly influence the timing of the secondary thermal rupture.",
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Analysis of fluid injection-induced fault reactivation and seismic slip in geothermal reservoirs. / Gan, Quan; Elsworth, Derek.

In: Journal of Geophysical Research: Solid Earth, Vol. 119, No. 4, 04.2014, p. 3340-3353.

Research output: Contribution to journalArticle

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