Geomechanical analysis of a welding salt layer and its effects on adjacent sediments

- We study stresses in and around a welding salt layer using a forward finite-element model.
- Salt pressure is significantly higher than overburden stress in thinned areas of the layer.
- An anomalous stress increase develops in sediments at the weld tip.
- This stress increase explains anomalous compaction and faulting of weld sediments.
- These material changes explain changes in location and productivity of adjacent reservoirs.

We simulate welding of the source layer of a salt diapir with a forward finite-element model and study stresses and deformation in the salt layer and the diapir, as well as in their adjacent sediments. Welded salt layers are abundant in mature salt basins, where most or all of the salt has withdrawn into diapirs. However, there is little understanding of the stress field in these layers and their adjacent sediments. We show that salt flow along the source layer leads to significant stress anomalies inside the layer and in adjacent sediments. In the source layer, salt pressure becomes higher than overburden stress in nearly welded areas and becomes lower than overburden stress in adjacent thicker areas. When the source layer welds, stresses increase significantly in sediments near the weld tip, which helps compaction of these sediments and possibly their fracturing and faulting. Our model illustrates that all sediments overlying the weld experience this stress increase and the associated material changes as the weld tip propagates along the weld. We present natural examples fitting our predictions and discuss the importance of our results for the exploration, characterization, and production of reservoirs near welded salt layers.

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