Upscaling Core
Plug Data to Reservoir Modelling Grid: A Small-Scale Heterogeneity Modelling
Approach
Wen, Renjun1, Philip Ringrose2,
Kjetil Nordahl3 (1) Geomodeling Technology Corp, Calgary, AB (2)
Statoil R & D, 7005 Trondheim, Norway (3) Statoil ASA, Trondheim, Norway
Core plugs are direct measurements of
reservoir rocks and, therefore, represent the most quantitative information
about the reservoir. However, use of core plug data in reservoir models is a
major challenge due to sample bias (a core plug represents a tiny fraction of
the reservoir). Petrophysical properties at core-plug scale are primarily
controlled by mm- to cm-scale bedding structures. Conventional reservoir
modelling workflows integrate core plug data into full-field grids by statistical
methods that ignore the effects of mm- to cm-scale heterogeneity. To increase
the accuracy of reservoir property models, we developed a workflow for
upscaling petrophysical models from core plug scale to simulation grid scale.
The modelling method consists of two
steps. First, we simulate bedding structure grids by modelling bedform
migration, deposition and erosion processes. Second, the bedding structure grid
is populated with rock properties, such as porosity and permeability, which can
be derived from core plug data and/or high-resolution well log data.
Stacking of different bedding structures
can generate a near-well-bore heterogeneity model with a grid cell size of
about 1 mm3. The net-to-gross ratio and porosity data can be conditioned to
core or log data. Directional permeability (kx, ky,
kz) and relative permeability at the bedding structure scale (0.1 to 1 metre)
is calculated by upscaling the mm-scale model using fixed, linear or periodic
boundary conditions. Rock type curves, facies-dependent kv/kh and effective
property values can be derived from the upscaling results of multiple bedding
structure realizations.
Since a litho-facies is an association of
bedding structure types, the upscaled properties from the bedding structure
models can be assigned to full-field facies model grids. The resulting models
account for small-scale heterogeneity and can be applied to flow simulations.
Case studies demonstrate that small-scale modelling and upscaling can improve
accuracy of reservoir simulations and production profile forecasting.
AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California