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The Santa Barbara Channel is 50 mi northwest of Los Angeles, and represents the offshore part of the Ventura basin, which covers an area of approximately 70 mi in length and 25 mi in width. Structurally, the basin is characterized by sharply folded, highly faulted anticlines, some of which are offshore extensions of onshore producing trends. The basin contains up to 40,000 ft of Tertiary sediments, with production from Pliocene through Eocene reservoirs.
The history of Humble's geophysical activity in the Santa Barbara Channel spans the period from early 1948, when the first reconnaissance lines were shot, through the 1969 digital CDP program. During this period, Humble compiled approximately 10,000 mi of seismic data. All of the data accumulated through 1967 was incorporated into a regional interpretation of the Santa Barbara Channel in preparation for the Federal lease sale in February 1968. Later surveys continued to improve data quality and velocity control for prospect evaluation on Humble leases.
Early seismic surveys, 1948-1953, used dynamite or black powder as an energy source and were recorded on paper records. An "L" spread cable configuration was commonly used, which enabled the geophysicists to resolve a true strike and dip at each shot point. These seismic events were laboriously hand picked, plotted, and migrated. Interpretation of the deep structure was greatly limited on these data by lack of penetration and a severe multiple problem. The near surface structures could be defined and resulted in the discovery of several fields on State offshore leases.
The development of CDP shooting techniques, first used by Humble in 1964 in the Santa Barbara Channel, gave the first insight into the deep structural complexity. Attenuation of multiple energy was possible and greatly needed velocity information could be obtained. Regulations limiting the amount of dynamite which could be used, were the greatest incentive for industry to change to non-dynamite sources. Air gun, gas exploder, and Aquapulse became the principal sources used. Data quality continues to be enhanced by improvements in the energy source, shooting technique, and data processing.
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