Measuring Pressure Dependent Permeability in Shales: Impact of Stress Path and Anisotropy Available to Purchase

Accurate measurements of matrix storage and transport properties in unconventional tight oil/shale gas systems are of fundamental importance to informing key business decisions as stress-sensitive matrix response can predominate on controlling later life field performance. We have developed novel laboratory stress application and flow systems/techniques for measuring the effects of a non-hydrostatic stress field (maximum overburden stress orientated perpendicular to sedimentary layering) on storage and transport properties of anisotropic shale formations. Measured pore volume compressibility and stress sensitive, bedding-parallel permeability exponents in Mancos shale samples indicate an approximately 50% reduction in both storage and transport multiplier magnitudes when measured under uniaxial strain boundary conditions, as opposed to the more routinely applied hydrostatic “net confining stress” approach. Various “uniaxial strain correction factors” are outlined for converting hydrostatic measurements to their equivalent uniaxial values, more representative of the u reservoir condition.