- Copyright © 2002 Society of Exploration Geophysicists
The key to successful development planning is the building of earth models integrating all relevant subsurface data and predicting reservoir performance in the presence of uncertainties.
The development of Bonga Field is presented as an example of integrated subsurface modeling of complex, deepwater channel reservoirs in which geophysical techniques are highlighted. Three main static reservoir parameters were modeled in detail: net sand distribution, subseismic channel architecture, and 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 the in-place oil volume assessment. However, because of limits to seismic resolution, all potentially relevant sand and mud beds cannot be visualized from (inverted) seismic data alone. Consequently, subseismic channel architectures have been deterministically placed in the static models based on analog and well data and guided by seismic attributes. Connectivity is especially important because pressure support and sweep from water injection wells is crucial to productivity from these near-hydropressured reservoirs. Reservoir connectivity is defined as a function of horizontal and vertical permeability, and transmissibility barriers. Analysis of seismic equal-amplitude surfaces is a way seismic can potentially help indicate areas of relatively better or worse connectivity. Each reservoir is simulated multiple times using scenarios based on all combinations of the above parameters. Highly amalgamated channels 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 might add to production in the future.
Bonga Field is currently under development 120 km offshore the southwestern coast of Nigeria, in water depths of 3100–3800 ft (Figure 1). It is in Block OML 118, formerly OPL 212, and …