Abstract: The Jiusha Formation in Sha 3 member of well Yi 65 is a typical reservoir characterized by medium water sensitivity and speed sensitivity;the crude oil is light thin oil possessing high solidification point,low density,viscosity and sulphur content;the salinity of the formation water can be as high as 1100~19900mg/L in general,and the water belongs to sodium hydrogen carbonate typed water.This paper investigates the formation damage mechanisms of well Yi 65 with high temperature and low permeability,and evaluates the possible damage and damage conditions from the aspects of formation characteristics,injected water quality,suspended particle blocking,free oil,emulsified oil,scaling,bacteria and past stimulation treatments.The internal factors of the damage to water injection wells include water sensitivity,speed sensitivity and low permeability,and the external factors contain solid suspended particles,poor water quality,excessively high oil content and bacteria numbers.

Key words: well Yi 65, low permeability, blocking, sensitivity, injected water