The Stress Response of Permeability

Abstract

Abstract The response of intergranular permeability to applied hydrostatic stress is quantified through third-order polynomial fits to data from three loosely-to-moderately consolidated sandstone reservoirs from the same geological province. The derivatives of the fitted polynomials allow diverse permeability vs. stress behaviors to be identified and grouped. This grouping is quantified using composite stress-response parameters based on the polynomial regression coefficients, most notably their root mean square. This composite parameter shows a sufficiently good correspondence to Leverett's equivalent circular pore diameter Lp to define exclusive "stress facies" in terms of ranges of Lp in these formations. A permeability reduction factor from ambient conditions to effective reservoir stress is determined for each stress facies as a basis for correcting conventional core measurements. Although the results are formation- and stress-facies-specific, the approach has a general validity and can be adopted for any appropriate permeability vs. stress function. Principal benefits include better reservoir characterization and a sharper description of the change in permeability with stress as a basis for improved simulation models for development planning.