ORION AND POLARIS VISCOUS OIL DEVELOPMENTS: INTEGRATION AND MODELING OF HORIZONTAL MULTI-LATERAL WELLS

Development of the Greater Prudhoe Bay area Orion and Polaris viscous oil fields offers a strategic opportunity to tap a portion of the North Slope's 25+ billion barrel viscous oil resource and unlock future heavy oil potential. To aid in field development, the Orion/Polaris Team constructed a fully integrated static model that incorporates detailed core-based reservoir descriptions to create a robust dynamic model that defines reservoir flow units for dynamic simulation. Since the fields contain components of both ongoing and future development, the model must support both near-term well planning for high rate multi-lateral wells, and form the basis for simulation input into multi-million dollar facility decisions. The model can be quickly updated, since minimal time is required to modify the well data and rock properties.

The target Schrader Bluff Formation is a series of compartmentalized, stacked shallow marine sandstone reservoirs that exhibit marked variability in reservoir quality. Integration of core-based reservoir description and high-resolution biostratigraphy, with log-derived detailed stratigraphic correlations at the field-scale and facies scale, allows delineation of cyclical stratigraphic partitioning and facies heterogeneity that control reservoir quality distribution within the field. The combination of this stratigraphic framework for well interpretation and the transition to faster Linux workstations has enabled a truly iterative reservoir modeling process. Historically, the static and dynamic models were updated once a year. The new static model can be completely rebuilt in less than two days, and updated in a few hours in response to dynamic modeling results.

Highlights of advances in the modeling update process include: 1. Structural control picked at the wellsite that accurately positions horizontal wells for history-matching; 2. Reservoir architecture that delineates high-permeability transgressive sands from lower permeability highstand deposits 3. Rock property distributions constrained by core-based facies analysis; and 4. Saturation functions unique to each of the twelve structural compartments and six sands developed.