Paper l

Comparison of fracture apertures computed from electrical borehole scans and reflected Stoneley waves:  an integrated interpretation

Brian E. Hornby, Stefan M. Luthi, and Richard A. Plumb

Schlumberger-Doll Research, Ridgefield, CT

ABSTRACT

Fractures crossing the borehole are probed using electrical currents generated by For­mation MicroScanner pads and Stoneley waves generated by an acoustic source. New techniques have been developed to invert these measurements for estimates of equivalent fracture aperture. The objective of this paper is twofold: first, to com­pare aperture estimates in rock types, and second, to exploit the different physical measurements to improve our understanding of the fracture system. In the first case, natural fractures are probed in crystalline rocks. The second example investigates fractures in a limestone reservoir. Fracture aperture results are displayed alongside acoustic borehole televiewer images, Formation MicroScanner images and core pho­tographs for reference. Fractures evident on the borehole televiewer images and in cores are quantified by both techniques. A combined analysis of the two methods is interpreted to yield additional information concerning fracture extent, fracture con­nectivity and borehole effects such as fracture enlargement and borehole rugosity.