--> Abstract: Syndepositional Fracture Patterns of the Devonian Reef Complexes, Canning Basin, Western Australia; #90063 (2007)

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Syndepositional Fracture Patterns of the Devonian Reef Complexes, Canning Basin, Western Australia

 

Frost, Ned1, Leonel Gomez1 (1) The University of Texas at Austin, Austin, TX

 

Syndepositional opening-mode fractures known as neptunian dikes are a common feature in many carbonate systems throughout the geologic record. The Canning Basin's Devonian reef complexes preserve perhaps some the world's best examples of these features. Syndepositional fractures exert a profound influence on diagenesis, porosity and permeability evolution, and karst development; understanding the controls on their distribution is critical to accurate reservoir characterization.

 

Fracture aperture and spacing were measured along 1D scanlines in the outcrops of Windjana Gorge. In these data sets we analyzed key fracture attributes such as orientation, fracture strain, fracture intensity, aperture scaling, and spatial arrangement. We used Normalized Correlation Count (NCC), a recently developed analytical technique, to distinguish between five possible types of spatial arrangements: random, harmonically arranged clusters, fractal, more abundant than random (plateau), or a combination of the previous four arrangements.

 

This study shows strong variations in fracture patterns as function of depositional facies, platform margin trajectory, and tectonic setting. Facies in prograding platforms consistently exhibit higher values of fracture intensity and extension than their counterparts in retrograding margins. The backreef is typically the least fractured; however, discrete zones of high fracture intensity often occur near syndepositional faults and zones of curvature created by compaction over antecedent topography. Fractal, harmonically arranged, and random spatial arrangements of fractures are observed, with cluster type, width, and spacing varying with individual facies. These variations in fracture characteristics primarily arise from differing mechanical properties of individual facies, and the fundamentally different fracture controls acting prograding and retrograding margins.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California