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Seismic Acquisitin Design in a Geologically Complex and Difficult Area of Berau Bay, Papua Barat

Supriyono, Supriyono; Suryanto, Deny
Seismic Delivery, BP Indonesia, Jakarta, Indonesia.

The seismic method is not guaranteed to work. Some overburdens can scatter, absorb and deflect seismic energy so badly that little or no energy from the target returns to the surface. The small amount of energy that does return will usually be exceptionally difficult to process, not least because it will then be difficult even to identify primary energy pre-stack, making it especially difficult to design and test a denoise, demultiple and /or depth imaging strategy. Seismic acquisition and processing in many areas of Berau Bay (Papua Barat) must overcome overburden problems in this ultra-difficult class. The other challenge is shallow waters of Berau Bay where streamer operations are mostly difficult or impossible, and OBC must instead be used.

BP had a successful trenched OBC survey over the Vorwata Field in 2005. Trenching the cable prevents it moving in the strong tidal currents, improves receiver coupling and significantly reduces ambient noise. However the cost/km² is very high, hence trenched OBC is prohibitively expensive except in small areas of very high value such as giant field production cores. We needed an untrenched approach in Berau Bay.

The acquisition design started with a 3D Finite Difference Acoustic Forward Modeling study. This type of study has made important contributions in Berau Bay, by suggesting acquisition designs and seismic processing techniques that can image through the laterally variable, complex subsurface geology. Computer simulation is far cheaper and faster than real acquisition testing. With a realistic processing sequence, the synthetic data produces images very similar to the real target structures as a function of field effort, allowing us to assess the cost - benefit trade off for various acquisition designs.

The result of the modeling study together with a thorough seismic acquisition technology evaluation and field trial equipment testing led to a decision to use wide azimuth - wide patch - high fold acquisition with an OBC ‘parallel' geometry. This paper illustrates the results for three surveys, covering exploration, appraisal and development applications. The OBC parallel geometry was successful despite the complex geology and difficult surface conditions in Berau Bay.

 

AAPG Search and Discovery Article #90155©2012 AAPG International Conference & Exhibition, Singapore, 16-19 September 2012