During reservoir model building, one encounters several stages where upscaling or averaging of petrophysical data is required; core plug data have to be compared to wireline measurements and wireline measurements are averaged to the scale of building-size reservoir grid cells. Simple averaging does not, in most cases, give representative values, since the property in question is very scale-dependent. This is especially true for permeability and permeability anisotropy (kv/kh).

For the case of a reservoir model of the Garn Formation (Middle Jurassic) in the Tyrihans Field, a simple geologically based upscaling method including the use of the SBEDe software package has been developed. Small-scale models of near well-bore geology are upscaled using single-phase flow simulation to obtain directional-dependent permeabilities for facies with different mud contents and style. The resulting kv/kh estimation curve has been implemented in the reservoir model by modelling Vshale as a continuous parameter and applying the function to derive upscaled horizontal and vertical permeability grids. Upscaled permeabilities were found to closely match the well test data. This approach gives a more realistic kv/kh ratio than traditional methods involving simple averaging, or arbitrary guesses, of vertical permeability.

C. Elfenbein, Ø. Husby and P. Ringrose, Statoil

Read complete article

Hear From us

You have Successfully Subscribed!

Pin It on Pinterest

Share This