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| Titel |
A workflow for transferring heterogeneous complex geological models to consistent finite element models and application to a deep geothermal reservoir operation |
| VerfasserIn |
Bo Wang, Sebastian Bauer |
| 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 |
250127676
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| Publikation (Nr.) |
 EGU/EGU2016-7579.pdf |
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| Zusammenfassung |
| Geological models are the prerequisite of exploring possible use of the subsurface and
evaluating induced impacts. Subsurface geological models often show strong complexity in
geometry and hydraulic connectivity because of their heterogeneous nature. In order to model
that complexity, the corner point grid approach has been applied by geologists for decades.
The corner point grid utilizes a set of hexahedral blocks to represent geological formations.
Due to the appearance of eroded geological layers, some edges of those blocks may be
collapsed and the blocks thus degenerate. This leads to the inconsistency and the
impossibility of using the corner point grid directly with a finite element based simulator.
Therefore, in this study, we introduce a workflow for transferring heterogeneous geological
models to consistent finite element models. In the corner point grid, the hexahedral blocks
without collapsed edges are converted to hexahedral elements directly. But if they
degenerate, each block is divided into prism, pyramid and tetrahedral elements
based on individual degenerated situation. This approach consistently converts any
degenerated corner point grid to a consistent hybrid finite element mesh. Along
with the above converting scheme, the corresponding heterogeneous geological
data, e.g. permeability and porosity, can be transferred as well. Moreover, well
trajectories designed in the corner point grid can be resampled to the nodes in the
finite element mesh, which represents the location for source terms along the well
path.
As a proof of concept, we implement the workflow in the framework of transferring
models from Petrel to the finite element OpenGeoSys simulator. As application scenario we
choose a deep geothermal reservoir operation in the North German Basin. A well doublet is
defined in a saline aquifer in the Rhaetian formation, which has a depth of roughly 4000 m.
The geometric model shows all kinds of degenerated blocks due to eroded layers and the
structure determined by salt tectonics. The operation time of the reservoir is set to 20 years,
and in each year, hot water is extracted for 6 months at a rate of 150 m3/h during the heating
season. The injection well is operated at the same rate with a cooled water temperature of 40 ˚
C. The simulation results show that this reservoir can produce water with an average
temperature of 161.5 ˚ C at the designed rate. During the operation, the cold water
front propagates preferentially towards the extraction well. Thus, after 20 years, a
temperature decrease of larger than 5 ˚ C can be observed at a distance of 800
m from the injection well. In addition, due to heat conduction from neighboring
strata, a temperature decrease of about 5 ˚ C can be observed at the injection well. |
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