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| Titel |
Single-well tracer push-pull test sensitivity w. r. to fracture aperture and spacing |
| VerfasserIn |
I. Ghergut, H. Behrens, S. Karmakar, M. Sauter |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250062241
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| Zusammenfassung |
| Dealing with a parallel-fracture system of infinite lateral extension, four characteristic
regimes of tracer signal sensitivity w. r. to fracture aperture and w. r. to fracture spacing s
(whose reciprocal defines fracture density, or the fluid-rock interface area per volume) can
be identified during the pull phase of a single-well push-pull test, also depending
upon the ratio between push-phase duration Tpush and a characteristic time scale
Ts (defined by s2 / D = Ts , with D denoting the tracer’s effective diffusion
coefficient):
early-time regime: tracer signals are sensitive w. r. to fracture aperture, but
insensitive w. r. to fracture spacing; sensitivity w. r. to fracture aperture first
increases, then decreases with Tpush / Ts (thus there will be an optimum in
terms of to Tpush / Ts , at early pull times);
mid-time regime: tracer signals are sensitive w. r. to fracture spacing, but
insensitive w. r. to fracture aperture; sensitivity w. r. to fracture spacing
increases with Tpush / Ts ;
late-time regime: with increasing pull duration, tracer signals become
increasingly insensitive w. r. to fracture spacing, while regaining sensitivity w. r.
to fracture aperture;
‘very late’-time regime: sensitivity w. r. to fracture aperture becomes
independent upon Tpush / Ts .
From these different regimes, some recommendations can be derived regarding the design and
dimensioning of dual-tracer single-well push-pull tests for the specific purposes
of geothermal reservoir characterization, using conservative solutes and heat as
tracers.
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Acknowledgement: This study is funded by MWK Niedersachsen (Lower-Saxony’s
Science and Culture Ministry) and by Baker Hughes (Celle) within task unit ‘G6’ of the
Collaborative Research Project ‘gebo’ (Geothermal Energy and High-Performance Drilling). |
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