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| Titel |
Modeling CO2 distribution in a heterogeneous sandstone reservoir: the Johansen Formation, northern North Sea |
| VerfasserIn |
Anja Sundal, Rohaldin Miri, Johan Petter Nystuen, Henning Dypvik, Per Aagaard |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250084540
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| Zusammenfassung |
| The last few years there has been broad attention towards finding permanent storage options
for CO2. The Norwegian continental margin holds great potential for storage in saline
aquifers. Common for many of these reservoir candidates, however, is that geological data are
sparse relative to thoroughly mapped hydrocarbon reservoirs in the region. Scenario
modeling provides a method for estimating reservoir performances for potential CO2
storage sites and for testing injection strategies. This approach is particularly useful
in the evaluation of uncertainties related to reservoir properties and geometry. In
this study we have tested the effect of geological heterogeneities in the Johansen
Formation, which is a laterally extensive sandstone and saline aquifer at burial
depths of 2 – 4 km, proposed as a suitable candidate for CO2 storage by Norwegian
authorities.
The central parts of the Johansen Formation are underlying the operating hydrocarbon
field Troll. In order not to interfere with ongoing gas production, a potential CO2 injection
well should be located at a safe distance from the gas reservoir, which consequently
implies areas presently without well control. From 3D seismic data, prediction of
spatial extent of sandstone is possible to a certain degree, whereas intra-reservoir
flow baffles such as draping mudstone beds and calcite cemented layers are below
seismic resolution. The number and lateral extent of flow baffles, as well as porosity-
and permeability distributions are dependent of sedimentary facies and diagenesis.
The interpretation of depositional environment and burial history is thus of crucial
importance.
A suite of scenario models was established for a potential injection area south of the Troll
field. The model grids where made in Petrel based on our interpretations of seismic data,
wire line logs, core and cuttings samples. Using Eclipse 300 the distribution of
CO2 is modeled for different geological settings; with and without the presence
of pervasive low permeability draping mudstone layers, and with varying lateral
extent of potential calcite cemented layers in 8 to 15 intra-reservoir depth levels.
The modeled area covers 10 x 15.8 km, with a thickness of 110 m at the injection
point. Simulations were run with an injection phase of 30 years plus 100 years of
migration.
The presence of meso-scale flow baffles causes a reduction in vertical permeability in
addition to the facies related variation on the micro-scale. Scenarios including potential flow
baffles as separate layers in the model grids were compared to scenarios in which the effect of
flow baffles were included using harmonic mean average of vertical permeability.
The subsequent differences in CO2 distribution are important in estimating the
contact area between the plume front and reservoir brine. A heterogeneous reservoir
with internal flow baffles is not necessarily a disadvantage as long as sufficient
injectivity is maintained within individual sandstone bodies. In each scenario we aim
to adapt a suitable injection strategy with respect to utilizing local effects such
as the delimitation of gravitational flow, in order to increase reservoir sweep and
maximize the effect of trapping mechanisms (i.e. residual, stratigraphic, mineral and
dissolution). |
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