The development of the Bonga field is presented as an example of integrated subsurface modeling of complex, deepwater channel reservoirs, highlighting geophysical techniques. Three main static reservoir parameters were modeled in detail: (1) net sand distribution, (2) sub-seismic channel architecture, and (3) reservoir connectivity. Proprietary probabilistic, model-based seismic inversion has provided excellent predictions of net sand thickness in development wells in the main reservoir, adding confidence to our in-place oil volume assessment.

Because of limits to seismic resolution, all potentially relevant sand and mud beds cannot be visualized from (inverted) seismic data alone. Sub-seismic channel architectures have been deterministically placed in the static models based on analogue and well data and guided by seismic attributes. Connectivity is especially important because pressure support and sweep from water injection wells are crucial to productivity from these nearly hydro-pressured reservoirs. Reservoir connectivity is defined as a function of horizontal and vertical permeability and of transmissibility barriers. Analysis of seismic equal-amplitude surfaces provides a way seismic can potentially help indicate areas of relatively better and worse connectivity. Each reservoir is simulated multiple times using scenarios based on all combinations of the above parameters. Highly amalgamated channels

Unnumbered Figure. Seismic section showing Bonga's 4 main reservoir intervals. An offset synthetic displays increasing amplitude with offset, characteristic of Bonga oil sands.

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are less impacted by connectivity variation than less well amalgamated channels. Reservoir simulation models have been transferred to synthetic seismic models and demonstrate the potential value of time-lapse (4D) seismic. Other "in-field opportunity" reservoirs have been identified in addition to the main reservoirs and may provide added production potential in the future.

Acknowledgements

The authors would like to thank the following for permission to publish this work: The Nigerian National Oil Company (NNPC), National Petroleum Investment Management Services Company (NAPIMS), Shell Nigeria Exploration and Production Company Limited (SNEPCO), Esso Exploration and Production Nigeria (Deepwater) Ltd., Nigeria Agip Exploration Ltd., Elf Petroleum Nigeria Ltd, and Shell Deepwater Services.

Unnumbered Figure. Location map of Bonga Field, offshore Nigeria.

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