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| Titel |
Reactive transport modeling of CO2 injection into storage reservoirs: application to case-studies in The Netherlands |
| VerfasserIn |
Tim Tambach, Mariene Gutierrez-Neri, Mariëlle Koenen, Frank Van Bergen, Henk Kooi, Bert Van der Meer |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056682
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| Zusammenfassung |
| The Netherlands play a key role in Carbon Capture and Storage (CCS) implementation in
northwestern Europe. Here, CO2 sources and storage reservoirs are located at relatively short
mutual distances and pipeline infrastructure is already in place for (cross-border) gas
transport over large distances. Application of CCS within the next 5 years is promoted by the
government, because of strong commitments to reach the emission reductions and maturing
of the oil and gas production. It is expected that many fields will be abandoned in the coming
two decades. After a field is abandoned, it will probably not be economically feasible to
prepare it for CO2 storage. The near-future application of CCS in the Netherlands requires
standardized methodologies for the evaluation of the reservoir for HSE issues and
accountability of the stored amount of CO2, as for example requested by the European
Directive on CCS and mandatory for government policy. The aim of this study is, by using
real field examples, to bring the geochemical assessment of potential reservoirs from an
academic approach to a methodology that can be used by policy-makers to grant
licenses.
Due to the practical limitations involved in experimental observation of the in situ
behavior of CO2 in reservoirs, numerical models are frequently used for evaluating the short-
and long-term effects. In this study reactive transport modeling (TOUGHREACT) is used for
modeling the short- and long-term geochemical effects of CO2 storage in potential reservoirs
of The Netherlands that are selected for near-future storage. First, the composition of the
formation water was defined by equilibrating the reservoir mineralogy with water and gas,
not accounting for transport, at a given temperature and pressure. Then the geochemical
composition was applied to a reservoir grid with cells that are in contact with each other.
Small scale cells were constructed near the well-bore, to take a closer look at near-well
effects.
During the short-term injection phase, dry-out of the near-well zone is observed and salt
precipitation is computed. This occurs due to water uptake by the injected dry CO2, which
then flows into the reservoir. The impact of salt precipitation and the radius of the completely
dried out zone around the well-bore depends on the water saturation, the amount of CO2 that
is injected, the salinity, and the total injection time. This radius is computed to be in the order
of 10 to 100 m. In the dried out zone further dissolution and precipitation of mineral reactions
stop taking place due to the absence of water. Salt precipitation can lead to serious injectivity
problems.
The dissolution of CO2 in the formation water, away from the dried out zone, leads to a
relatively fast decrease in pH, from approximately 6.5 to 3.5. Subsequently, this decrease is
slowly buffered by mineral dissolution throughout the reservoir, as well as mineral
precipitation, porosity changes, and CO2 trapping in several carbonate minerals (e.g.
calcite, dolomite, dawsonite, siderite, and magnesite), thereby immobilizing the
CO2 and increasing storage security. Although quartz is predominantly present and
relatively stable in most reservoirs, the initial composition of the other minerals in the
reservoir is important for the specific mineral reactions that are taking place in the
reservoir. The porosity and permeability changes away from the dried out zone are
computed to be small up to hundreds of years. It is therefore not expected that any
problems will occur with respect to the integrity of the reservoir within this time
frame. Sufficient CPU time or smarter computational techniques are required for
further predicting the long-term stability of CO2 in potential storage reservoirs. |
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