Characterization of Mississippian Osage Chat in South-Central Kansas
Kansas Geological Survey
Open-file Report 2002-50
Characteristics of chat reservoirs in study area.
Low resistivity accompanied by low natural gamma ray and high porosity
Extreme lateral, vertical, microscopic, and macroscopic heterogeneity
Fields are segmented into pods or compartments of good reservoir quality separated by areas of poor reservoir quality
Porosities in chert facies range from approximately 20 to 50%
Routine air permeabilities from 5 to 500 md.
Often high water saturations, long transition zones and complex fluid contacts
Incompletely silicified lithofacies or lithofacies associated with tripolitic chert:
cherty dolomite and sucrosic dolomite
cherty dolomite reservoirs exhibit characteristics more typical of carbonate reservoirs (e.g., Aetna Gas Area):
Relatively low porosity, 10-20%, permeabilities less than 5 md
Water saturations from 35-70%
Bulk volume water (BVW) from 0.06-0.10.
Irregularly distributed sucrosic dolomite in cherty limestone (e.g., Bates Field)
porosity ranging from 10-18%
permeabilities between 5 and 70 md
low irreducible water saturations
BVW between 0.05- 0.07.
Last updated January 2003