The presence of discontinuities in a seal affects both their mechanical and hydrogeologic properties; migration of fluids or gas through mm- to cm-scale discontinuity networks can lead to the failure of gas or fluid traps. The presence of discontinuity networks increases the volume of rock matrix in contact with subsurface fluids creating preferential pathways for fluid flow and changing the mechanical properties of the seal. We examine the mechanical and fracture stratigraphy of failed seals analogues exposed in central and south-east Utah. We use outcrop surveys to identify relationships between occurrence of discontinuities and sedimentologic variability, and to understand the nature of alteration associated with fluid flow through these fractures. We use data from each locality to quantitatively define mechano-stratigraphic units, based on consistency in fracture distribution, bed thickness, lithologic stacking pattern, field-derived compressive strength and permeability. These data allow us to define mechano-stratigraphic units at each locality and to compare the changes in deformation behaviour between localities. Using this systematic methodology to quantify differences and similarities between field analogues we improve our understanding of the important role of micro- to meso-scale fracture networks play within sealing lithologies and how various seal lithologies respond the changes in stress.


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