Future workflows for water saturation interpretation in heterogeneous intervals, should take the heterogeneity into account in a robust manner. We want fine-scale geology to be modelled realistically, down towards mm-scale when appropriate, and populate these models with properties from pore-scale modelling. The geologically realistic models can then be upscaled for effective properties for different rocktypes. Accordingly, Archie’s law can be used for water saturation interpretation without breaking its assumptions. The work presented is a study in which we want to validate such a workflow, and assess the predictivity to be expected. Two core plugs from a heterogeneous reservoir have been studied in a steady-state flow experiment while simultaneously measuring both resistivity and in-situ saturation in 3D by CT-imaging. Resistivity was measured in a 4-electrode set-up connected to a multi frequency impedance meter. The experimental design yielded data where now resistivity, relative permeability and fine-scale saturation are all coupled. 3D digital models of the plugs have subsequentially been constructed from CT porosity and populated with properties from pore-space modelling. This enables us to compare the fine scale saturation modelling, which is a difficult task for this type of sedimentary rocks, to the measured water distribution in the plug. Fine-scale saturation also determines upscaled resistivity, which we can model digitally using pore-space models and compare with the measurements. Our findings indicate that the workflow is viable, and that we are able to obtain predictive power from pore-scale modelling and fine-scale geological modelling.
Håvard Berland, SPE, Kari Børset, SPE, Kjetil Nordahl, Lars Rennan, Alf B. Rustad, SPE, StatoilHydro Research Centre Trondheim, Norway