Statistically-based Lithofacies Predictions for 3-D Reservoir Modeling:An
Example from the Panoma (Council Grove) Field,Hugoton Embayment
Kansas Geological Survey
Open-file Report 2003-30
Statement of Problem
No comprehensive geologic model for the Council Grove
Accurate reservoir model is critical for most efficient
management of remaining resources in this large asset.
Lithofacies controlled petrophysical properties dictate
Accurate discrimination of lithofacies reduces error
in predicted permeability and gas volume.
The Council Grove is a large, complex heterogeneous reservoir.
Field-wide upscaling of lithofacies distribution for
reservoir characterization and analysis of large heterogeneous reservoirs
like the Panoma Field is impractical by traditional methods
Use artificial intelligence to predict lithofacies in 500 wells and fill
a 3D volume with lithofacies constrained porosity, permeability and gas saturations.
- Identify and characterize key lithofacies and tie to core petrophysical
- Predict lithofacies for wells without cores using a neural net and electric
log curves and marine-nonmarine indicator curve as predictor variables.
Generate predicted lithofacies and probability curves.
- Fill 3-D cellular volume with lithofacies and porosity using Petrel.
- Add lithofacies-constrained permeability and gas saturations to cell
properties with transform formulas and height above free water.
- Export cellular model with porosity, permeability, and initial gas saturations
to a reservoir simulator.
Council Grove facies identification
is important to reservoir characterization because petrophysical properties
vary between facies. At porosities > 6% permeability in grainstone/bafflestones
can be 30X greater than mudstones and >100X greater than marine siltstones
of similar porosity. Differences in permeabilities between nonmarine
silt/sandstones and shaly siltstones range from 3.3X at 12% porosity
to 7X at 18%.
Capillary pressures and corresponding
water saturations also vary between facies. For example, at 7% porosity
(which represents >50% of all Mstn/Wkstn) at 200 ft above free water
Mudstones are 100% water saturated while grainstones exhibit water saturations
~40%. Differences in water saturations between facies increase with
decreasing porosity and decreasing height above free water.
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Last updated May 2003