Abstract: Characterization of a Complex Fluvio-Deltaic Reservoir for Simulation

Steve Begg, Alex Kay, Edmund Gustason

We demonstrate how a range of reservoir characterization techniques were integrated to generate a highly geologically based reservoir-simulation model for investigating gravity drainage in the Prudhoe Bay Field. The essence of our approach is to use geology to generate fine-scale porosity-permeability models, then rescale these to the simulator grid.

The lower part of the reservoir comprises very heterogeneous rocks deposited in fluvio-deltaic environments. Using core data, we identified a number of lithotypes as the main geologic controls on flow. However, these lithotypes cannot be identified in non-cored wells and are not continuous at normal well spacings. Thus, they could not be used directly to derive the simulation model.

However, amalgamating lithotypes by depositional environment yielded 6 Major Facies Associations (MFAs) which were identifiable in non-cored wells. This reduced the problem to one of generating an MFA model and then assigning simulator-scale porosity and permeability to each MFA.

The MFA model was generated by the Sequential Indicator Simulation (SIS) technique, conditioned to 60 wells. The porosity and permeability for each MFA was derived by first generating a model of the lithotypes within it, using an object technique to preserve known geometrical relationships. This lithotype model was converted to a fine-scale porosity and permeability model using core-plug data and then rescaled to the simulation grid.

Finally, the MFA and porosity and permeability models were combined to produce the simulation model, which readily matched over 10 years of production data, with virtually no changes to the description.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994