MIXED SOURCE ACQUISITION, ELK HILLS AND BUENA VISTA HILLS, CALIFORNIA

During the past 18 months Occidental of Elk Hills has operated two 3D seismic surveys across Elk Hills and one 2D survey across Buena Vista Hills. Phase 1 and 2 3D surveys across Elk Hills covered 150 square miles, and entailed the acquisition of 38262 vibrator and 10549 dynamite source points. The Buena Vista 2D seismic project consisted of 12 lines, totaling 141 line miles and entailed the acquisition of 5751 vibrator and 957 dynamite source points. Vibrator energy source surveys must be augmented with dynamite due to complex land use issues such as "conservation areas," rugged terrain and agriculture. Dynamite testing is relevant, even though it was used as a secondary source in these surveys, because dynamite usage tends to be clustered while in either 3D or 2D mode. Dynamite testing show that depth of shot is a key parameter decision, while charge size is of lesser importance. Which energy source is "better?" Dogma within many southern San Joaquin Operators has traditionally been that vibroseis is superior in terms of penetration and bandwidth. Results from the recently acquired Buena Vista 2D program, however, offer strong arguments in contradiction to this traditional view. Source signature matching between vibroseis and dynamite can be facilitated by examining vibroseis versus dynamite in both CMP stack and CMP gathers. Examples demonstrate significant data degradation when this issue is unresolved.