POROELASTIC RESPONSE OF A BOREHOLE IN A NON-HYDROSTATIC STRESS-FIELD

This paper deals with the solution of the stress, displacement, and pore pressure field induced by the drilling and/or the pressurization of a vertical borehole. The rock, which is permeated by fluid, is assumed to behave as a poroelastic material with compressible constituents, following the Biot theory. The analytical solution is derived in the Laplace transform space, and is transformed to the time domain using an approximate numerical inversion technique. The solution reveals a full range of coupled poroelastic effects which provide potential mechanisms for delayed borehole instability and shear fracture initiation inside the rock.