--> Abstract: Quantitative Analysis of 3-D Geologic Outcrops: Deep-Water Jackfork Sandstone from Big Rock Quarry, Arkansas, by Mariana I. Olariu, Carlos L. Aiken, John F. Ferguson, and Xueming Xu; #90078 (2008)

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Quantitative Analysis of 3-D Geologic Outcrops: Deep-Water Jackfork Sandstone from Big Rock Quarry, Arkansas

Mariana I. Olariu1, Carlos L. Aiken1, John F. Ferguson1, and Xueming Xu2
1Geosciences, UT at Dallas, Richardson, TX
2Real Earth Models LLC., Dallas, TX

This study represents the first attempt at three-dimensional interpretation of the geometry and facies pattern of the Pennsylvanian Jackfork channel complex at Big Rock Quarry in Arkansas. Oblique close range photography acquired from the ground is integrated with terrain data obtained by laser scanning the outcrop and converted into a three-dimensional digital photo real model.

Facies architecture and dimensions of channel sandstones are highly anisotropic (width/length/thickness). As a consequence it is critical to know how outcrops are oriented within depositional strike/dip to make meaningful quantitative analysis of channel dimensions. We use the 3-D photo real model of the outcrop to generate dimensional data that represent true dip/strike orientation.

The exposed channels are characterized by a low aspect ratio (4:1 to 32:1) with widths ranging from 25 m to 314 m and thicknesses from 2 m to 24 m. Thickness distributions of various facies show that the sandstone comprises a significant proportion (83% in average) of the total channel fill, while shale and matrix-supported breccia represents about 8%, and respectively 17%. The channels have a high net to gross ratio of more than 80%.

The exposure has a blocky aspect due to preferential weathering on the fracture planes. The blocky pattern of the terrain surface of the outcrop was quantitatively captured by high-density, high-accuracy terrestrial laser scanners. By developing a surface classification algorithm for fracture identification and orientation it was possible to evaluate the fracture geometry, which is helpful in interpretation of reservoir quality. Visualization and analysis of the centimeter-resolution terrain data provided characterization of the fracture system at outcrop scale that is consistent with the deformations at larger, regional scale.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas