Fracture Corridors as Seal-bypass Systems - Case Studies from the Jurassic Entrada Formation Utah, USA

Abstract

We discuss discrete zones of enhanced fracturing characterized by closely-spaced, sub-parallel fracture networks (i.e. fracture corridors) as preferential fluid flow pathways which serve to bypass sealing systems and to connect reservoirs at different stratigraphic levels. We identify 3 types of fracture corridors on the basis of their structural relationships with larger faults and folds, representing end-members of a continuum of possibly interrelated products. These fracture networks are: 1) fault damage zone, 2) fault tip process zone and 3) fold-related crestal zone fracture corridors. The tabular corridors show different orientations and patterns of fracturing, defining a local- to large-scale network of inferred high-permeability vertical and lateral conduits. In the study area (Utah, USA), analyzed fracture corridors share the occurrence of discolored (bleached) zones, testifying to the ancient circulation of reducing fluids. These observations can be used to support reservoir-caprock systems modeling and fluid flow simulation assessment, for instance in geological CO2 storage.