If you withdraw, the surface will subside.

If you inject fluid in a rock that has no open spaces, it will explode (earthquake)

If there are open spaces, the fluid will occupy those spaces if it can get there.

Hi Gabriel

I believe that firsrly the pressure make the rock crack initiation. As the time passing with more pressure that initiated crack, propagates.

Good luck

I can answer your question from the stiff clay point of view. Its important to know the current stresses on the rock you are talking about. In such condition fissuring plays an important role where if fissurs present penetration of water into fissures can cause develoment of cracks. Further more as Farzad mentiond by time this cracks will propogate.

First of all it is...what kind of fluid, at what temperature, how much volume and into what kind of rock

every thing varies depending on all these criteria

In a hard rock like granite which is un weathered...if you try to inject fluid by making some hole or along some plane...it will be less effective whereas

in case of sandstone it will occupy pore spaces, in case of shale it will react with soft clay minerals...

when you simply inject and withdraw fluid unless it is of large volume

nothing big will happen

you have to add the other dimensions also, specially time, temperature, composition...both of rock and fluid.