The dry frame stress sensitivity of sandstones

    Research output: Contribution to journalArticle

    10 Citations (Scopus)

    Abstract

    Two general laws are put forward to described the sensitivity to hydrostatic stress observed in the laboratory on a selection of unsaturated reservoir core and outcrop sandstones, with low to moderate porosities. These relations are based on using the concept of excess compliance as a pseudo-function to describe all internal weaknesses, regardless of whether their origin is cracks, contacts or other mechanisms. The bulk modulus, ?, is defined by a dimensionless parameter Sv lying between 0 and 1, which depends upon the values of the modulus at room pressure and the high pressure asymptote ?8 of the behaviour. The rate parameter, Pc, determines the rapidity of convergence on the final high pressure asymptotic state as pressure is applied. There is a well-defined relationship between ?8 and porosity, but in contrast Sv and Pc are almost independent of porosity. Sv is weakly correlated to clay fraction. Shear wave properties are specified through the normalized shear modulus ? = µ/(? + 2µ). An additional dimensionless parameter Ss determines the magnitude of this particular stress sensitivity. The parameter is predicted to be smaller than Sv but can be either positive or negative. For most dry sandstones Ss remains negative (this corresponding to an increase in Vp/Vs with pressure), with its magnitude and sign correlating to clay fraction.

    Original languageEnglish
    Pages (from-to)59-81
    Number of pages23
    JournalJournal of Seismic Exploration
    Volume11
    Issue number1-2
    Publication statusPublished - 2002

    Keywords

    • Excess compliance
    • Laboratory measurements
    • Pressure sensitivity
    • Sandstone
    • Stress sensitivity
    • Time-lapse sensitivity

    Fingerprint Dive into the research topics of 'The dry frame stress sensitivity of sandstones'. Together they form a unique fingerprint.

    Cite this