Reservoir Delineation Using High Resolution Seismic Data in the South China Sea

David L. J. Tsay

Conventional seismic data with the frequency bandwidth of 10-80 hz has been playing an invaluable role in mapping favorable subsurface structure for initial exploratory drilling. However, in order to characterize the reservoir properties over the discovered field for reservoir delineation, the seismic data must have the frequency components higher than 80 hz. This is particularly true when the desirable reservoir properties to be delineated are the thickness and porosity of several thin layers within the Miocene carbonate reservoir in the South China Sea. In this paper, two methods of enhancing seismic resolution will be discussed and illustrated with the examples of real data taken from the South China Sea.

The first method of enhancing seismic resolution is to apply the technique of spectral whitening to the original seismic data. The resulted data shows that the frequency bandwidth is almost doubled from the original 10-80 hz to 10-140 hz. As a result, the thickness of each thin layer within Miocene carbonate reservoir can be resolved at 7m instead of 12m from the original data.

The second method is to designed a new field parameter by using a shallower towed depth of seismic energy source at 4m instead of 6m used previously. Because of shallower towed depth, the first notch of source ghost becomes higher and leads to higher resolution of acquired field data with the frequency range of 10-140 hz. Consequently, a thin bed of 7m within carbonate reservoir can be resolved.

The success of enhancing seismic resolution has led to better reservoir delineation, drilling operation design and development plan.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California