| Popis: |
Summary In many reservoir-modeling projects, porosity-permeability relationships derived at the core plug measurement scale are applied to the reservoir model without properly taking into account the differences in scale between measurement and model grid block. Each grid bock in the reservoir model is assigned a permeability based on well log effective porosity and porosity-permeability correlations observed from core data, and then treated as a homogeneous volume with isotropic flow properties. This practice fails to account for the well-known phenomenon that in a stratified medium, effective permeability becomes more strongly anisotropic as volume-support increases from "quasi-point" core plug scale to scales which are larger than the heterogeneities which effect fluid flow. This paper proposes a relatively simple and cost effective solution to the "scale mismatch" problem The quasi-point porosity-permeability relationship derived at the core-plug scale is more appropriately applied to single-well micro-models built from the integration of core and wire-line log data. The micro-models are then upscaled to produce porosity, vertical and horizontal permeability distributions and multivariate relationships that are consistent with the macro-scale reservoir model, while preserving the micro-scale flow characteristics. Upscaled porosity-permeability relationships are extracted and used to populate "effective" permeability into the macro-scale reservoir model, prior to flow simulation. The proposed method's application is demonstrated in the reservoir description and flow simulation of a giant extra-heavy oil field in Venezuela. |
