Two companies have completed what they believe to be the first full scale onboard seismic processing job.
The companies acquired 6,000 km of regional 2-D seismic in the Ardjuna basin in the northwest Java Sea off Indonesia. The participants said the job took only a few weeks compared with 18-24 months without onboard processing.
Atlantic Richfield Indonesia Inc. and Landmark Graphics Corp. said the job resulted in two breakthroughs:
- ARCO was able to concurrently modify the survey and avoid having to commission a second vessel later to obtain the best possible seismic coverage.
- ARCO shortened the time between acquisition and drilling decision by at least 1 year.
Landmark said it is talking with oil companies in the region about onboard processing of 3-D seismic surveys.
ONBOARD PROCESSING
ARCO and Landmark said a team of processors working around the clock processed 4,000 km of seismic data through final migration before the ship docked at the end of its seven week cruise in June.
Donald F. Dean, a geophysicist with ARCO Exploration & Production Technology's geophysical acquisition and processing group in Plano, said:
"What was done here-in terms of the quality and quantity of data processed onboard the boat-has not been done before, to our knowledge."
Dean worked aboard the acquisition vessel for several weeks.
"By onboard processing I mean attempting to run all of the data through a complete processing sequence, including final dip moveout, stack, and migration.
"A lot of people can 'process' data on a boat, or on land, behind the seismic crew, for field acquisition quality control. Typically they process a small subset of the total volume-one or two lines, or every 10th line-to see what the data look like," rather than processing the entire survey.
The team used two workstations with Landmark/ITA software known as supercards, or multiple process accelerators, that allow very high throughput of seismic data. They also used algorithms specially designed to optimize the hardware.
JAVA SEA JOB
Acquisition rates on the northwestern Java Sea job occasionally exceeded 200 km/day, and the acquisition took several weeks less than anticipated, due mainly to calm seas, said D. Gordon Armstrong, geophysical specialist responsible for all seismic processing for ARCO Indonesia.
"Although the company's goal had been to process all 6,000 km of data during acquisition, the interpreters actually received 4,000 km of data that they would not have seen for another eight months if we had done the processing through a contractor onshore."
Armstrong felt certain that all data would have been processed onboard if acquisition had taken the full two months ARCO anticipated.
After modifying the software and installing more accelerators, the ITA system was fully processing about 140 km/day of data.
ARCO was able to forward the data quickly to interpreters in Jakarta who loaded it on an interactive workstation and interpreted it. They decided where they had programmed a certain seismic line was not adequate, Armstrong said.
The interpreters laid out two new lines on a map and sent it to the vessel, which acquired the two lines, processed them, and returned them to Jakarta where they too were interpreted before the survey was finished.
"That data has already been incorporated into maps that are determining exactly where to drill. Without onboard processing, this same scenario would have taken a year and a half or two years," Armstrong said.
DISCIPLINES REUNITED
After three decades of near isolation, a reunion of seismic acquisition, processing, and interpretation is occurring, observed Bruce Nelson of Singapore, general manager of Landmark's Asia/Pacific region.
Several obstacles had to be overcome. Nelson said Landmark personnel in Calgary stayed up late at night to make vital changes to the software, mainly to accommodate very large data sets. Some of the lines were more than 50 km long.
The modifications were sent to the vessel by satellite.
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