DETERMINATION OF SHALE ANISOTROPIC POROVISCOELASTIC PROPERTIES FROM THREE-POINT BEAM BENDING TEST

Abstract

Permeability is an extremely important property of shale. It is essential to know permeability as it can aid engineers in developing drilling and production strategies and help executives make important financial decisions. However, the measurement of shale permeability has long been a challenge in the industry due to shale’s extremely low porosity and permeability (in Nano Darcy range). Conventional method of measuring shale permeability may take hours even days. This work presents a new permeability measurement method named three-point beam bending test that was originally invented and developed by Scherer in 1992. This method approximates shale permeability that is in reasonable agreement with the theoretically predicted values from empirical equations. In this thesis, orthotropic poroelastic solutions of the pore pressure and load decay are derived and studied. The thesis also extends the poroelastic solutions to poroviscoelastic solutions to accommodate the viscoelasticity of the shale. Viscoelastic properties of shale complicate the problem, thus two viscoelastic models are introduced in this thesis. The analytical solutions pore pressure and load decay under constant deflection test are plotted and investigated. Influence of anisotropy, viscoelastic properties and sensitive of permeability on the solutions are studied. In practice, the permeability of the shale beam is approximated by matching the analytical solution of the load decay to the experimental data acquired from the constant deflection test. At last, potential limitations of the experiment and improvements are discussed.