Case 3 Formation of Turtle Back Structures
Contents
The present 2D bench scale Case 3 comprise multiple pre-existing sand layers above the salt layer and an elastic base layer below the salt. The top of the salt layer includes multiple seed points to promote diapir formation. This bench scale example aims to capture the formation of turtle back structures and salt welds in the salt layer under syn-sedimentary growth in conjunction with extensional and compressional tectonic settings. Three fixed sedimentation horizon layers will be utilized here for the three deposition layers.
A full data description will not be presented here, only key data will be described. The simulation run completes in approximately 2 hours on a 3.6 GHz AMD processor machine.
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Turtle Back Structures (Final Configuration) |
| Problem Description |
The 2D problem consists of a 1500mm long by 40mm high salt layer with five pre-existing overburden sand layers 140mm thick in total and a 10mm elastic base layer. The sand layers are made up of two sand materials with different material strengths in alternating layers. The model side boundaries are subjected to extension/compression via an applied displacement in X. Multiple seed points are located on the salt horizon to promote diapir formation. An initial stage is performed where gravity is activated using a linear ramp curve prior to initiating the extension phase in stage 2. Three different sedimentation stages follow on in stages 3 to 5 in conjunction with the extensional / compressional loadings. In this example, fixed sedimentation horizons are utilized for the three deposition stages. Note that the bounds of the sedimentation horizon geometries extend to at least the full extent of/beyond the side displacement loadings.
Units of the model for stress, length and time are Pa, mm and years respectively.
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The simulation comprises five stages with the timings summarized in the table below :
Stage # |
Description |
Stage duration (hours) |
Time lapse (hours) |
Stage 1 |
Geostatic initialization with gravity |
0.5 |
0 - 0.5 |
Stage 2 |
Extension loading |
3.9 |
0.5 - 4.4 |
Stage 3 |
Extension loading + Sedimentation #1 |
1.1 |
4.4 - 5.5 |
Stage 4 |
Compression loading + Sedimentation #2 |
1.5 |
5.5 - 7.0 |
Stage 5 |
Compression loading + Sedimentation #3 |
1.0 |
7.0 - 8.0 |
| Key Data Description |
The data file for the project is in : Mech_005\Case03\Data.
Following are descriptions of some key data. Note that these data descriptions are not in the same order as they appear in the data file.
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The result files for the project are in directory: Mech_005\Case03\Results.
The figures below show the formation of two salt diapirs and turtle back structures. Primary horizontal salt welds are observed at various locations at the base of the salt and secondary vertical salt weld is seen developing below the right hand side diapir canopy.
Note that the salt welds cannot be pinchout/merged as self-pinchout is currently not permitted in ParaGeo.
Salt Turtle-Back Structures (Final Configuration)
Formation of Salt Turtle-Back Structures
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