LIDAR IMAGING OF NATURAL FRACTURES IN THE CHATTANOOGA BLACK SHALE OF NORTHEASTERN ALABAMA

Interest in the organic rich Devonian Chattanooga Shale of the Appalachian fold-thrust belt of Alabama, for natural resource potential, has grown within the last decade. Evaluation of natural fracture patterns is important for understanding unconventional gas-shale reservoirs. Several exposures of the Chattanooga Shale can be found along the backlimb of the Wills Valley Anticline in Northeastern Alabama. They provide opportunity for Terrestrial LIDAR (Light Detection and Ranging) imaging. LIDAR laser scanning in tandem with digital imaging allows an efficient means to obtain precise, high resolution three-dimensional data which constitute an information dense point cloud that provides accurate outcrop details. As natural fractures play a vital role in the movement of fluids, the information rich images gathered from scanning outcrops of the shale can be used to evaluate fracture relationships which offer potential insight into enhanced production as well as insight into the local and regional stress fields preserved in the rock record.

LIDAR images of fractures within Chattanooga shale outcrops along the backlimb of the Wills Valley Anticline allows for quantitative capture of fracture geometry, orientation, and density. These high resolution images allow for the evaluation of the relationship between bedding thickness and fracture intensity in the fractured beds of the Chattanooga Shale. Lithologic variability within the Chattanooga Shale lends itself to distinct tectonic responses. The lower part of the Chattanooga shale behaves ductilely along a decollement surface formed during the Alleghanian orogeny and the upper part of the Chattanooga shale behaves brittlely containing joints and fractures. Analysis of LIDAR images for fracture relationships within the Chattanooga Shale not only provides the opportunity for enhancing hydraulic fracture treatment, but also helps to determine the regional stresses recorded in fractured shale beds.