Terrestrial Lidar Imaging and Fracture Analysis of the Woodford Shale; Western Arkoma Basin, Oklahoma

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Since the late 1990s horizontal drilling and hydraulic fracturing of Devonian shales in the mid-continent region, such as the Woodford Shale, has revolutionized gas exploration in the United States. These two methods are reliant on robust predictive reservoir models, particularly addressing the geometry, spacing, and density of complex natural fracture networks within the otherwise tight shale. However, the natural fractures within the Woodford Shale have not been rigorously studied despite their importance to fluid flow and ultimately recovery of hydrocarbons. Most of the subsurface fracture mapping of the Woodford has been done using 3D seismic data and seismic attribute analysis. This study applies terrestrial Light Detection and Ranging (LiDAR) to study natural fracture patterns of two Woodford outcrops located in the Arkoma Basin, southeastern Oklahoma. One outcrop is located south of the town Wapanucka, and the other outcrop is east of the town Atoka. The high-resolution images obtained from terrestrial LiDAR reveal fracture spacing and fracture density allowing the quantitative assessment of how these fractures vary in different sections of the Woodford Shale where bedding thickness, mineralogy, and degree of deformation (folding) differ significantly. In this study we evaluate whether a statistical relationship exists between bedding thickness and the mineralogy (i.e., silica content vs organic content), fracture spacing, and fracture density of shale beds. Preliminary results suggest that thicker beds contain larger fracture spacing and smaller fracture density. The results of this study will help us to 1) better understand geometry, origin, and distribution of natural fractures in the Devonian Woodford shale in the Mid-Continent region of the United States and in other parts of the world; and 2) develop more realistic reservoir models for improved hydraulic fracturing methods.

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