Permeability prediction using stress sensitive petrophysical properties

The correlation of stress sensitivity to various petrophysical parameters w as studied by analysis of experimental results from a range of sandstone co re plugs tested hydrostatically at room temperature. The parameters measure d were: compressional wave velocity, porosity permeability and electrical r esistivity, More detailed information on the effects of sorting and grain s ize distributions mas obtained from experiments on artificial, unconsolidat ed sandstone cores. The measurements showed a high degree of stress sensiti vity, which was different for each core but, broadly, could be classified a s either high or low stress sensitivity, Cores from the high permeability c lean sand were less stress sensitise than the cores from the low permeabili ty coarsening-upwards sequence and the petrophysical values when combined i nto a synthetic log distinguished between the two Lithologies. The results were compared to the predictions of a simple asperity deformation model. Th e experimental results and the model suggested a possible logging strategy to deduce permeability, by varying wellbore pressure.