SEISMOGEOLOGIC EXPERIENCE IN THE BEAUFORT SEA

Abstract

Conventional seismic data processing was applied to 24‐fold airgun data acquired in the Liverpool and Mackenzie Bay areas of the Beaufort Sea. These data provided general indications of the regional geology and the types of structures present. A part of one line in each area was chosen on the basis of its geologic content and data quality for reprocessing through a velocity analysis package. The purpose was to establish velocity, particularly interval velocity, as the common ground between geology and the seismic section. The velocity package performs a continuous analysis for time and moveout as well as amplitude on all events present within a common‐depth‐point gather. Events are joined from depth point to depth point on the basis of similarity in time, moveout, amplitude, and polarity to yield a segment file. This file is statistically analyzed and sorted into two subsets, primary and nonprimary files, using segment velocity as the criterion. Interval velocities can be calculated between those segments that exhibit velocities characteristic of primary energy. The space‐variant velocity control derived from the data was used to correct it for moveout. A marked improvement in the interpretability of the data resulted on both lines. The data‐derived interval velocities give intriguing indications of lithology which can be correlated to acoustic logs on shore. Plausible hypotheses of offshore geology have been derived without the benefit of any offshore drilling.