Mathematical Modelling of Irreversible Deforming, Micro- and Macrofracture of Rock in the Vicinity of a Borehole in Its Dynamical Unloading

Abstract eng:
The rock formation at a depth of several thousand meters is exposed to a hydrostatic pressure. Drilling a borehole makes the drill experience same pressure from the walls of the borehole. On fast removing of the drill from the borehole the dynamical process of unloading borehole walls begins. The sharp decrease of normal pressure on the walls of the borehole brings to the increase of ring stresses. The waves of unloading propagate from the borehole, which could cause fragmentation of rock and blocking the borehole with fractured material. The goal of the present paper is to give the problem statement foe the dynamical process of unloading the internal walls of the borehole after removing the drill, and successive oil-bearing layer’s fracturing. The layer is represented by the model of damageable thermoelastoplastic material with two parameters of damaging (by evolution of micropores and by shear microfracturing). The criterion of the beginning of new free surfaces within the material) uses the principle of the critical value of specific dissipated energy.The problem is treated as two-dimensional (plane deformed state). This task is solved numerical modeling on Lagrancian mesh by method similar to M.L. Wilkins one and on local reconstruction of the Lanrangian grid in the vicinity of the fracture origination.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket