Reservoir Characterization to Inexpensively Evaluate the Exploitation Potential of a Small Morrow Incised Valley-fill Field

Kansas Geological Survey
Open-file Report 2002-9

Core Petrophysical Properties

Permeability and Porosity

To predict permeability within the Morrow for all well locations a relationship between measured permeabilities and porosity and argillaceousness (shalyness) was developed. The general relationship between permeability and porosity for the Norcan East Minneola Unit Morrow is similar to the relationship exhibited by other Morrow channel sandstones. Although previous Morrow study (Byrnes, 2000) has shown relationships between permeability and porosity as a function of lithofacies, because details of lithofacies are not available for many wells in the Minneola unit and several unit are just channel sandstones, a simpler predictive relationship for permeability was developed. A measure for shalyness was obtained from correlation of shalyness in core with API gamma-ray units on logs. Permeability increases with both increasing porosity and decreasing shalyness. Also evident is that the cleaner sandstones do not always exhibit the highest porosity values. This may be due to greater quartz cementation or porer sorting. Permeability may be predicted within a factor of 3.4 using the following relation:

log10kinsitu = 0.134 finsitu - 0.03 GRI + 0.138

Where kinsitu is the in situ Klinkenberg permeability and finsitu is the in situ porosity. The standard error of prediction for this equation is a factor of 3.4 (e.g. a predicted permeability of 1 md might be 3.4 md or 0.3 md). For prediction of reservoir permeability three classes of shalyness were defined; GRI<30 API units, 30<GRI<39 API units, and GRI > 40 API units. Based on wireline-log analysis the Morrow has been subdivided into three flow units in the Minneola Unit. For each of these intervals the average GRI over the flow unit interval was calculated. The interval was assigned to one of the three classes based on the average interval GRI and the permeability calculated using the appropriate equation for that class as determined by linear regression analysis for each class:

GRI <30 log10kinsitu = 0.140 finsitu - 0.558
30<GRI<40 log10kinsitu = 0.137 finsitu - 0.924
GRI >40 log10kinsitu = 0.121 finsitu 1.069

Both Patton #1-3 and Statton #2-12 show a fining-upward sequence that also correlates with increasing GRI upward. Since permeability decreases with increasing shalyness, the lower intervals in these wells exhibit higher permeability. The division of the Minneola reservoir into 3 layers is consistent with subdivision of the fining upward sequence.

Using the predicted permeabilities for each of the three layers at each well location, gridcell permeability values were assigned. Gridcell values for the surrounding gridcells in the simulation model were assigned values based on mapping interpolation.

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Last updated March 2002