Field Development and Renewed Reservoir Characterization for CO2 Flooding of the Hall-Gurney Field, Central Kansas

Kansas Geological Survey
Open-file Report 2001-38

Calibrating Unscaled Electric Logs

Within the area mapped there were no modern or even scaled electric logs were available until the Carter-Colliver CO2 I-1 well was drilled. The only logs available were Gamma Ray-Neutron Logs (unscaled) run in the open portion of the wells. Generally, 7" casing was set in the top of the Lansing, 10-20 feet above the top of the "C" zone, and the "C" zone was completed through open hole.

The neutron logs were calibrated using the only core petrophysical measurements available, from the Colliver #1 which was cored in in May of 1936. The maximum core porosity of 26% in the "C" zone was assumed to be the maximum neutron count and the least porous portion of the Lower Plattsburg ("D" zone) was assumed to have 3% porosity. A logarithmic porosity scale was "pinned" at these two points on the Colliver #1 and yielded a good match between the balance of the core porosity data and the now scaled neutron log.

With the log scaled, the marine shale at the base of the Plattsburg (base of "D" zone) has a porosity of 28%. This blanket, relatively deep marine shale was assumed to have consistent porosity throughout the area and was used as one of the "pin" points and that along with the least porous portion of the "D" zone (3%), the other "pin" point, the other logs were scaled to obtain porosities throughout the area of interest.

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Last updated December 2001