Abstract: Kuihua Island offshore reservoirs are composed of strata with high porosity and medium to high permeability or medium porosity and low to medium permeability of which shales are rich montmorillonite and mixture of montmorillonite and illite and they are easily to be damaged. In order to prevent formation damage occurred in engineering operations, damage avoiding operational fluids were innovated. These operational fluids can adjusted into completion fluid, perforating fluid and packer fluid with required properties like density, viscosity and filtration and all of them are with clay and shale inhibitive character.They do not have environmental problem and can be drained on the surface and are less costly. Practlces of 30 wells showed a satisfied results.