Abstract: The stress around a hole will re-distribute after the hole has been drilled, due to the loss of original stress balance, There exists a plastic zone around hole for the poorly consolidated sand formation, The zone near well bore gas the lowest permeability because of the invasion of drilling fluid, solid particles. and the influence of plastic deformation, There exist three different ermeability zones around wellbore, damaged zone having plastic feature, plastic zone, and elastic zone. The plastic zone will extend for width when the fluid
flows into the well, and cause formation damage aggravation. The critical flow rate depends On the permeability of damaged zone,formation consolidation and the viscosity Of formation fluid.

Key words: Elastoplasticity, Stress field, Stress analysis, critical velocity, Permeability, Formation damage