Laboratory Study on Effect of Hydration to Shale Mechanics

On the basis of analyses of wellbore unstability mechanism, the changing law of shale mechanics parameters was established after shale hydration by the experimentation. The results from contrasts of collapsing pressures between unhydrated shale and hydrated one indicate that collapsing pressure for shale which behaves poor water sensitivity can be increased on a large scale, and verify the phenomenon exists that shale is stable in early contact with drillng fluid and turns out to be unstable later.