Abstract: A permeability estimator is constructed from the lambda parameter, .LAMBDA., which is the size of dynamically connected pores. For simple pore geometries at high permeabilities, .LAMBDA. should theoretically be proportional to the pore volume-to-surface area ratio. Further, at high permeabilities, the permeability is proportional to .LAMBDA..sup.2 /F where F is the formation factor. Core data are used to establish the proportionality constant. At permeabilities less than about 100 md, the estimated permeability is seen to overestimate the actual permeability by a factor related to the estimate. Thus, a corrected second estimate can be readily made and is shown to match measured permeabilities on a diverse set of sands and shaly sands with a correlation coefficient of 0.89 for log k. The estimate can also be made using NMR relaxation time data with a correlation coefficient of 0.92 for the same data set.

Abstract: Carbonate formations yield unreliable, down hole NMR results. Inter alia, these results must be corrected for temperature. The invention features several methods for obtaining more reliable NMR results for rock petrophysical parameters in carbonate rock formations based upon adjusting T.sub.2 data with respect to temperature.