Poroelastic measurements resulting in complete data sets for granular and other anisotropic porous media |

Poroelastic analysis usually progresses from assumed knowledge of
dry or drained porous media to the predicted behavior of fluid-saturated and
undrained porous media. Unfortunately, the experimental situation is often incompatible
with these assumptions, especially when field data (from hydrological or oil/gas reservoirs)
are involved. The present work considers several different experimental scenarios
typified by one in which a set of undrained poroelastic (stiffness) constants
has been measured using either ultrasound or seismic wave analysis,
while some or all of the dry or drained constants are
normally unknown. Drained constants for such a poroelastic system can be deduced
for isotropic systems from available data if a complete set of undrained compliance data
for the principal stresses is available, together with a few other commonly measured
quantities such as porosity, fluid bulk modulus, and grain bulk modulus.
Similar results are also developed here for anisotropic systems having up to orthotropic symmetry
if the system is granular (*i.e.*, composed of solid grains assembled into
a solid matrix, either by a cementation process or by applied stress) and the grains are
known to be elastically homogeneous.
Finally, the analysis is also fully developed for anisotropic systems with nonhomogeneous
(more than one mineral type), but still isotropic, grains --
as well as for uniform collections of anisotropic grains as long as their axes of symmetry
are either perfectly aligned or perfectly random.

- INTRODUCTION
- ISOTROPIC POROELASTICITY
- Homogeneous grains
- Deducing drained moduli from undrained: Isotropic system with homogeneous grains
- Heterogeneous grains
- Heterogeneous pores
- Deducing drained constants from undrained: Heterogeneous grains and pores

- ANISOTROPIC POROELASTICITY
- The coefficients
- Coefficient
- Inverting poroelastic compliance
- Deducing anisotropic drained constants from undrained: Homogeneous grains and pores
- Deducing anisotropic drained constants from undrained: Heterogeneous grains and pores
- Deducing anisotropic drained constants from undrained for very heterogeneous porous media

- SUMMARY AND CONCLUSIONS
- ACKNOWLEDGMENTS
- Bibliography
- About this document ...

Poroelastic measurements resulting in complete data sets for granular and other anisotropic porous media |

2009-10-19