Seismic reflection data obtained with a 500-channel, digital streamer cable can be processed by array-forming techniques that include optimal weighting and time-shifting of individual channels. Such processing can improve the vertical resolution of horizons at early and intermediate times as well as enhance the continuity and clarity of later reflections. In addition to the recording of individual channels, a separate recording can be made aboard ship with the individual channels array formed to simulate data obtainable with any of a wide variety of conventional

End_Page 921------------------------------

streamers.

To demonstrate data enhancement obtained by these techniques, a line was surveyed in the Gulf of Mexico, first with the 500-channel system and then with a conventional 48-channel streamer. When the 500-channel data were processed to duplicate the conventional streamer data, the larger system yielded better results for late as well as early times; this improvement may be attributed partly to reduced cable noise. Comparisons made with record sections and stacked sections show that: (1) long, beam-steered arrays can enhance deeper events while retaining the high-frequency content of shallow data, and (2) short arrays at small group intervals allow fine resolution of shallow events.

The ultimate approach to preserving broadband information is full 500-channel processing of individually recorded channels. With such processing, individual hydrophone groups can be considered essentially as points. When the Gulf of Mexico data are processed in this way, signal continuity persists to frequencies above 125 Hz, and lateral changes are observed to the limit of resolution provided by the 3-m spacing of the output stacked traces.

End_of_Article - Last_Page 922------------