Full-Core Porosity and Permeability Comparison to Nuclear Magnetic Resonance Results in Mississippi Lime

Smith, Charles H.; Ziane, Lynda

The Mississippi Lime, a primary target for oil exploration in Central Kansas and Oklahoma, is a difficult, altered lime reservoir with significant secondary porosity. Production generally has a very high water cut. A full core was taken and an analysis of the basic porosity and permeability was conducted. The release of the data coincides with the enhanced interest in this reservoir and the search for useful log information to determine the best position for horizontal drilling to minimize the water production and maximize the oil production.

Advancements in the physics of measurement and details of analysis have generated great confidence in the basic measurements of nuclear magnetic resonance (NMR) logs. The measurement of total porosity is capably determined by this technology with virtually no massaging of data. A conclusion of effective porosity, while not as easily determined, is still less subject to the whims of an analyst than any other method currently employed in the oil and gas business. Permeability calculated from the NMR measurements is less straightforward. Historically, this calculation requires a knowledge of the particular reservoir involved, with adjustments to the calculation made as the analyst detects changes in the rock structure. Any ability to remove subjective inputs from analysis is a desirable objective.

In this study, we will compare the results of porosity, effective porosity, and permeability from NMR to these same values as determined by lab work on the cores. For porosity, T1 (polarization) and T2 (relaxation) characterizations will both be considered. For permeability, Coates' permeability and Bray-Smith permeability will be presented.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013