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Modellering af opvarmning ved dampinjektion (Modi)
Steam injection is an innovative in situ remediation technology, which can be used to
remediate sites contaminated by e.g. chlorinated solvents or oil products both above and
below the groundwater table. The key issue in steam injection is the heating of the soil
and consequently it is important to be able to predict and assess this heating. For this
purpose mathematical models can be used. These models can be divided into simple energy
balance models and advanced multiphase flow models. The energy balance models assume a
certain geometry of the steam zone, which is rarely the case in remediations close to the
soil surface. The multiphase models are more flexible and they are able to simulate
processes in addition to the heating of the soil, however, they are complicated to use. In
this project a new model has been developed, which is more general than the energy balance
models but still simple to use. The model describes the radial heating of soil by steam
injection in a single well. The soil can be divided into layers with different
permeabilities and steam can be injected both above and below the groundwater table. The
model is based on an energy balance coupled with a gas flow equation that describes the
flow of steam in the steam zone towards the steam front. Verification of the model has
been made against analytical solutions to simple problems and simulations with the
multiphase flow model T2VOC. It has not been possible to perform a validation of the model
against experimental data since a sufficiently controlled set of data was not found.
The most important input parameters are permeabilities of the soil layers and the steam
injection rate and pressure. Additionally, the presence of a water table has a large
impact on the shape of the steam zone.
The model has been incorporated in a user-friendly Excel spreadsheet where all input
data can be set and where the results can be visualized in various ways. Furthermore
figures showing a vertical section of the heated area can be automatically generated in
Surfer.
Three examples of simulations of actual Danish clean-up operations with steam injection
have been made. These examples show how the model is used and the results it can provide.
For all the examples uncertainty about the geology makes it difficult to compare the model
results with observed data.
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