Geomechanical Studies on Intrasalt Shear Zones

Presenter

Maria Nikolinakou
Research Professor
Bureau of Economic Geology
Jackson School of Geosciences
The University of Texas at Austin

Description

I discuss geomechanical insights on the development and spatial/temporal evolution of intra-salt shear zones. Evidence from several forward finite element models shows that non-fault-related shear zones in salt domes and sheets may not necessarily form at diapir margins. I show that key controls for the formation of such intra-salt anomalous zones are sharp changes in salt-flow velocity magnitude and orientation. Characteristics of salt flow vary during the evolution of the salt system; hence the location and intensity of shear zones also evolves. I also discuss intra-salt shear zones caused by an active basement fault. I show that shear zones develop between the fault and breaks in surface topography. Salt viscosity affects how the basement fault modifies surface topography, and as topography evolves, shear zones evolve with it. Salt re-crystallization may remove many shear fabrics. However, internal layering may record such zones sheared over time. Therefore, understanding the mechanisms that create anomalous zones inside salt can help de-risk siting of storage caverns and waste repositories.