Fracture Characterization with Borehole Imagery: An Example from the Mount Vernon Unit,

Lamott Consolidated Field, Posey County, Indiana

By

SMITH, JASON T., DAVID E. BRITTON, and J. GARY PETERS

Team Energy, LLC, Bridgeport IL,

PETER S. KAUFMAN and IAN D. BRYANT

Schlumberger-Doll Research, Ridgefield, CT

     Horizontal wells with borehole imagery are rare in the Illinois Basin. As part of a detailed reservoir monitoring study, Team Energy, L.L.C. and Schlumberger drilled a horizontal borehole into the Mississippian Cypress Sandstone in the Mount Vernon Unit, less than a mile southeast of the Carbon Fault. Both wireline and logging-while-drilling (LWD) logs were collected in an inclined pilot hole. A full set of LWD logs and electrical image logs were collected using the GeoVISION^* tool in the horizontal drain hole. In addition to allowing highly accurate placement of the well into a thin oil column, the borehole imagery revealed the presence of a dense network of steeply dipping, open fractures. Over the 640-ft logged horizontal section, 157 fractures were interpreted from the image logs. Two fracture sets are present; the principal one strikes ENE, and the second strikes NNE. Detailed examination of the fractures on the borehole imagery shows that most of them terminate vertically against thin shale beds, which are acting as mechanical boundary layers. Because these thin shale layers are ubiquitous in the reservoir, the fractures will not contribute substantially to the vertical permeability of the formation but may enhance the horizontal permeability and could affect the drainage characteristics.

     *Mark of Schlumberger