Kansas Geological Survey Open-file Report 2003-31

Rock Petrophysical Properties and Modeling

Sources for Core Analysis Data

As with many smaller Mississippian fields, core was not available from within the field. To provide models for predicting permeability, oil-water relative permeability, capillary pressure properties, and connate water saturations, regional petrophysical trends for the Mississippian and trends obtained from analysis of eight cores from nearby fields were used.

Porosities for the Wellington West field average 16+4%. Porosities are interparticle, intraparticle and moldic. Properties of the moldic porosity rocks are largely controlled by original depositional fabric with permeablity increasing from mudstones to grainstones.

Lithofacies, Permeability, Porosity

Lithofacies and early diagenesis are major controls on permeability (k) and porosity () despite complex diagenetic overprinting by sub-Pennsylvanian subaerial exposure and burial processes.

k and decrease significantly and continuously with decreasing grain/mold size from packstone to mudstone ( a trend exhibited by many other carbonates) and from echinoderm-rich to spicule-rich facies

The permeability-porosity trend for all lithofacies are approximately bounded within two orders of magnitude by trendlines defined by:

log k_{in situ} = 0.25 _{in situ} - 2.5
log k_{in situ} = 0.25 _{in situ} - 4.5

Between these bounding trends each lithofacies exhibits a generally unique range of k and which together define a continuous trend with k decreasing with decreasing grain/mold size for any given porosity. Each individual lithofacies exhibits a unique sub-parallel trend to the general trend. Statistically the general trend is dominated by the large number of spicule-rich samples and is strongly influenced by mudstone and cemented echinoderm grainstone properties:

log k_{in situ} (md) =0.24 _{in situ}(%) - 3.78

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