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| Titel |
Effect of CO2-induced reactions on the mechanical behaviour of fractured wellbore cement |
| VerfasserIn |
Timotheus Wolterbeek, Suzanne Hangx, Christopher Spiers |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250129983
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| Publikation (Nr.) |
 EGU/EGU2016-10166.pdf |
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| Zusammenfassung |
| Geomechanical damage, such as fracturing of wellbore cement, can severely impact
well integrity in CO2 storage fields. Chemical reactions between the cement and
CO2-bearing fluids may subsequently alter the cement’s mechanical properties, either
enhancing or inhibiting damage accumulation during ongoing changes in wellbore
temperature and stress-state. To evaluate the potential for such effects, we performed
triaxial compression tests on Class G Portland cement, conducted at down-hole
temperature (80 ˚ C) and effective confining pressures ranging from 1 to 25 MPa. After
deformation, samples displaying failure on localised shear fractures were reacted with
CO2-H2O, and then subjected to a second triaxial test to assess changes in mechanical
properties. Using results from the first phase of deformation, baseline yield and failure
criteria were constructed for virgin cement. These delineate stress conditions where
unreacted cement is most prone to dilatational (permeability-enhancing) failure. Once
shear-fractures formed, later reaction with CO2 did not produce further geomechanical
weakening. Instead, after six weeks of reaction, we observed up to 83% recovery of
peak-strength and increased frictional strength (15-40%) in the post-failure regime, due
to calcium carbonate precipitation in the fractures. As such, our results suggest
more or less complete mechanical healing on timescales of the order of months. |
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