Abstract: Undershooting Using the Vertical Hydrophone Array
Nick Moldeveanu, Mark Chang
Acquiring seismic data in obstructed areas is typically done using a dual-vessel operation of undershooting. For multiple obstruction areas this technique often yields data for which the offset distribution is quite uneven and the dip sampling is insufficient. These shortcomings in the data in turn can lead to spurious amplitudes and/or erroneous structural interpretations. The bottom-cable technique, among others, has been used to correct for these. However, ghosting becomes a problem for the bottom-referenced techniques as the water bottom reaches certain depth. The use of hydrophone-geophone dual sensors has been suggested to alleviate the ghosting problem. While this dual-sensor approach is theoretically simple and intriguing, its operation and processing can be complicated by suc issues as phone calibration, matching, and coupling. In this paper, a dual-hydrophone technique is introduced as a viable alternative for use in marine undershooting.
A field experiment aimed at testing the geophysical, as well as the operational, feasibility of this new approach was carried out during a routine data acquisition program. The field operation proved to be flexible and robust, and the ensuing processing achieved superior ghost attenuation and high-quality merging with the regular streamer data. This technique has since been employed in a recent survey to infill data in a severely obstructed area in the Gulf of Mexico.
AAPG Search and Discovery Article #90981©1994 AAPG Pacific Section Meeting, Ventura, California, April 27-29, 1994