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The AAPG/Datapages Combined Publications Database
Houston Geological Society Bulletin
Abstract
Abstract: Integrated Subsurface Characterization of the Bonga Field, Offshore Nigeria
By
Shell Oil Co.
Houston, Texas
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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