Mary L. Krasovec

Imaging with reverse vertical seismic profiles using a downhole,hydraulic, axial vibrator.

Summary We present the analysis of a reverse vertical seismic profile (RVSP) acquired over a pinnacle reef in the northern Michigan reef trend. The survey exhibited two features of note: 1) a new, strong, downhole vertical vibrator, and 2) a random distribution of surface receiver locations. A short sequence of processing steps followed by diffraction summation migration provides a high resolution image of a portion of the target reef at 4600 feet depth. The high resolution of the image was largely due to the downhole source, which generated a high powered signal at frequencies up to several hundred Hz. The source signal was repeatable, allowing our processing scheme to recover these high frequencies. Due to adverse conditions, a large portion of the surface spread had to be abandoned. The reduced spatial coverage limits the extent of the migrated image, and therefore precludes an evaluation of the effectiveness of the random receiver spread. However, the partial image agrees with our previous interpretation of the reef. The high resolution offers new insight into the structure of the reef, although a detailed geological interpretation is not possible due to the limited extent of the image.