We use an evolutionary finite-element model to determine changes in stress and geomechanical features of sediments near a welding source layer of a salt wall. We show that a significant stress concentration develops at the weld tip, which is experienced by all sediments along the weld as the weld tip propagates along the weld. When the source layer welds, salt flow from diapir pedestal into diapir stops, resulting in a hydrostatic salt pressure. This pressure is less than the overburden stress in sediments over the pedestal. In fact, the salt in the pedestal supports only part of the weight of overlying sediments; the rest is transferred laterally to over-weld sediments through shear stresses above the weld tip. This transfer causes the stress concentration at the weld tip. We show that this concentration results in compression of sediments along the weld and hence enhancement of the weld sealing capacity. The resulting compaction can also explain the tightness of reservoirs near welds and the false pullup of their depths in seismic migration models. Our study is the first quantitative analysis of stress evolution near a welding salt layer and may help characterize and explore reservoirs near welds more accurately.
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