f Acquisition and In-Field Processing on Bottom Cable 3-D Seismic Surveys

Two 3-D seismic surveys located off the north coast of Java between Jakarta and Cirebon, were acquired by CGG for ARCO Indonesia in conjunction with PERT AMINA.One covered 105 square kilometers in the transition zone near Cilamaya. For operational and accessibility reasons, hydrophone bottom cables were used. Geophones in marsh cases on shore and in very shallow water provided 3-D coverage beneath the shoreline from shallow marine sources. The other survey covered 189 square kilometers in a producing oil field 35 kilometers north of Pamanukan in water depths of 35 to 45 meters. The presence of many platforms, tankers, and moorings made the dual-sensor bottom cable technique ideal for this area. A patch acquisition geometry was chosen for both surveys because of its ability to provide shallow coverage and the desired data distributions under obstacles, and for its operational simplicity among the obstructions. Bottom cables were used to allow deployment near the platforms and for their low noise characteristics. Acoustic positioning provided accurate receiver positions, while minimizing surface buoys, a major source of noise. Finally, extensive QC procedures, including DGPS monitoring, positioning control, attribute mapping, and seismic processing were used to provide feedback to the crew, allowing them to optimize operations. During one survey, two field-processed, 3-D migrated data blocks were delivered to the interpreter for preliminary mapping within a week after recording the last shots on each of those blocks.