Poroelastic analysis in tunnel and well testing

The theory of poroelasticity forms the analytical basis for fluid flow in soil or rock formation. Fully coupled fluid-flow deformation analyses are performed. The behaviour of a tunnel in clay shale is found to be composed of time-independent and time-dependent components. The time-dependent displacement is dominated by swelling. The investigation of the behavior of a disposal well reveals that the total stresses change during the injection and the maximum injection pressure without causing hydraulic fracturing is larger than the in situ minimum total stress. The permeability has significant effect on the induced pore pressure and total stress changes. The deformability does not affect the maximum induced pore pressure but has some effect on the total stress changes when the pseudo-steady state flow is reached. The study of 3 well tests in an oil sand reservoir draws the conclusion that the porosity-dependent permeability of the formation near the wellbore is greatly enhanced due to increasing high injection pressure. The pressure-dependent deformability has significant effects on the induced pore pressure and the total stress changes. The use of increasing injection step-rates can be a strategy to inject water into an oil sand reservoir.