Future of Seismic in Oman, Advantages of WAZ Compared to NAZ
Klaassen, Rini *1; Smith, Richard 1; Benjamin, Nigel 2; Cramp, Richard 2; Wah-Hong, Teo 2
(1) XPP/1, PDO, Muscat, Oman. (2) Pdo inhouse centre, CGGVeritas, Muscat, Oman.
Petroleum Development Oman (PDO) has been operating their high channel count acquisition seismic crews for the last 2 years. These crews, which operate 24 hrs per day using simultaneous vibroseis sourcing and consistently setting world-class production records well in excess of 13,000 VPs per day, have enable wide-azimuth (WAZ) with finely-sampled seismic data to be acquired efficiently. A typical PDO WAZ survey is in excess of 2,000km2 with more than 4000 fold data in 25x25 m common midpoint bins. At the moment 7 surveys have been acquired covering a total area of 12540 km2. Each survey generates approximately 25 billion seismic traces and 130 Terabytes of raw data.
The signal processing of WAZ data is carried out by CGGV in-house centre at PDO which has been upgraded to process these large volumes. Additional CPU capacity, mainly for imaging, is utilised in CGGV’s main UK centre for fast turnaround. The large volumes have challenged our processing centre and both software and processing flows have been consistently updated to achieve optimum results and turnaround times. The new geophysical software developed in the last years include data-adaptive ground roll attenuation, software to facilitate azimuthal velocity analysis, a new 3D Radon multiple attenuation module and the implementation of Common Offset Vector and 5D interpolation. They all became part of the routine processing flow with processing turnarounds of 8 to 12 months.
The results have shown that WAZ have improved signal to noise ratio with better imaging than existing NAZ data. Automatic azimuthal velocity picking and azimuthal migration algorithms have enabled preservation of the azimuthal information that could be used to map the variation in subsurface geology. Attributes extraction from such data for reservoir characterisation: lithology, fluid and fracture mapping is being studied. Software to improve the viewing capability and quick analysis to determine the azimuths that have unique information are under development.
Even though PDO has not yet attained the full potential of the WAZ data, the improved images and multiple suppression have already de-risked the structures that were based on NAZ data. PDO will continue to acquire WAZ data and is working hard to further develop existing and new processing algorithms to take advantage of the big potential of the WAZ data.
Some results and comparisons between NAZ and WAZ will be described in this paper.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain