3D Static Modeling of a Deep Water Nigeria Field, using Training Image-Based Modeling

Mark W. Dixon
Chevron Texaco Overseas Petroleum, Bellaire, TX

A Deep Water Field, located offshore Nigeria, was discovered and appraised over the last few years. The reservoirs, comprising of multiple hydrocarbon-bearing sands within the Middle and Upper Miocene age, are characterized as combined stratigraphic and structural traps. Shale diapiric movement has formed the structure, and deep water, turbiditic sand fairways define the reservoir limits. These reservoirs are fairly-well imaged on the 3D seismic, and oil-bearing sands are known to manifest themselves as Class II/III AVO anomalies.

For the last two years, a key sub-surface focus item has been the ongoing development of a 3D Static Model. This, in turn, has supported the Dynamic model, used for well planning and field development design.

The challenges for the modeling were to address the key uncertainties of sand distribution (net to gross) and reservoir connectivity and heterogeneity. Constraints on these parameters are provided by the depositional architecture of the turbidite systems and interpretation of channel and sheet geometries, as seen from the 3D seismic and supported by core data. Facies models were built by "training image-based" modeling using ChevronTexaco proprietary Multi-Point Statistics (MPS) software, within the GOCAD platform (marketed by Earth Decision Sciences). The selective use of seismic attributes, particularly coherency (EDGE), and a detailed depositional model interpretation, provided a successful workflow for populating the 3D model with reservoir facies. The use of MPS software allowed the flexibility to simulate a realistic spectrum of channel and sheet geometries, within the constraints of the complex, deep water, turbidite depositional environment.