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| Titel |
The Green River natural analogue as a field laboratory to study the long-term fate of CO2 in the subsurface |
| VerfasserIn |
Andreas Busch, Niko Kampman, Suzanne Hangx, Pieter Bertier, Mike Bickle, Jon Harrington |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250106159
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| Publikation (Nr.) |
 EGU/EGU2015-5812.pdf |
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| Zusammenfassung |
| Understanding the long-term response of CO2 injected into porous reservoirs is one of the
most important aspects to demonstrate safe and permanent storage. At the same time this is
one of the least understood aspects of CCS in general. The reasons are that “long-term”, in
the sense of hundreds to thousands of years, is impractical from a laboratory and
rather idealised from a reservoir modelling perspective. However understanding the
coupled long-term hydro-chemical-mechanical response of a reservoir-seal pair
following CO2 injection is highly desirable to improve confidence and trust from a
regulator and societal perspective, as well as to improve risk assessment and risk
reduction.
In order to provide one building block to advance understanding of this subject, in July 2012
Shell recovered some 300m of core from a scientific drill hole through a natural
CO2 field near Green River, Utah. This core transected two sandstone formations
(Entrada and Navajo) and one intervening seal layer, composed of interbedded
marine clay-/silt and sandstones (Carmel Fm.). Fluid samples and core material were
taken adjacent to the Little Grand Wash Fault (LGW), along which CO2-charged
fluids traverse from depth to the surface and which is believed to be the migration
pathway for CO2 inflow into the reservoirs. In-situ pH, CO2 concentrations, and
fluid element and isotope geochemistry were determined from wireline downhole
sampling of pressurized fluids taken from the Navajo reservoirs. The fluid geochemistry
provides important constraints on reservoir filling by flow of CO2 –charged brines
through the LGW fault damage zone, macro-scale fluid flow in the reservoirs and the
state of fluid-mineral thermodynamic disequilibrium, from which the nature of the
fluid-mineral reactions can be interpreted. In addition to core samples, we obtained
control samples from stratigraphically equivalent outcrop locations and drill holes
that were not subject to alterations by CO2 -charged fluids and served as a direct
comparison to the altered samples. We obtained geomechanical, mineralogical,
geochemical and petrophysical laboratory data along the entire length of the core
and from the control samples. Furthermore, we performed more detailed studies
through portions of the caprock in direct contact with the CO2-charged reservoirs.
This was done to constrain the nature and penetration depths of the CO2-promoted
fluid-mineral reaction fronts. These reactions have taken place in the last ~100,000 years,
which has been set as an upper limit for the onset of CO2 influx into the formations.
This data has been used as input for reactive (transport) modeling. In addition, we
compared geomechanical data from the CO2 –exposed core and the unreacted control
samples to assess the mechanical stability of reservoir and seal rocks in a CO2
storage complex following mineral dissolution and precipitation for thousands of
years. |
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