Oomoldic Reservoirs of Central Kansas, Controls on Porosity, Permeability, Capillary Pressure and Architecture

Kansas Geological Survey
Open-file Report 2002-48

Correlation of Textural Properties with Permeability

To try and improve the prediction of permeability over the standard use of porosity as the independent variable several textural parameters were measured. Indices were created as metrics for measurement using binocular microscope. Metrics using this method were selected since it was assumed that cuttings samples would be the only source of information other than well logs for most wells. It was also believed that this method would provide adequately quantitative data to assess variable influence.

Variables Measured:

Porosity - by helium porosimetry under ambient conditions

Connectivity Index - An index ranging from 1 to 4 representing the degree of connection between oomolds as observed at 10X-20X:

1 - no apparent connection between oomolds, nearly all molds observed have no connection to other molds
2 - Connections are observed but are limited (<10% of molds)
3 - Connections are observed between many molds
4 - A majority of molds display connection to other molds or some percentage of the molds appear to exhibit extensive dissolution and connection

Packing Index - An index from 1 to 4 representing the packing density of oomolds:

1 - Isolated oomolds
2 - Pack-wackestone, Limited contact between oomolds but many portions are wackestone
3 - Extensive contact between oomolds, packstone
4 - Dense packing of oomolds

Size - An estimate of the average oomold diameter in phi units

Archie Matrix Porosity Index - base on Archie’s (1952) second parameter for describing matrix porosity. Archie’s parameter was expressed A-D for matrix porosity. In this study it was expressed as 1 through 4:

1 - No visible porosity in matrix under 10X examination, pores < 0.01mm
2 - Visible porosity, 0.01mm<pores<0.1mm
3 - Visible porosity, 0.1mm<pores<cutting size
4 - Visible porosity, evident by crystal growth on pores, vuggy

Fracture Index - Index ranging from 0-3 representing influence of fractures on permeability:

0 - No fractures evident
1 - hairline fractures or cracks observed
2 - Fracture present
3 - Samples is heavily fractured


Figures to the above right indicate that several of the parameters are correlated with permeability and that the nature of the correlation is consistent with what would be anticipated.

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Last updated March 2004