Overbalance perforating and stimulation method for wells

A method of stimulating fluid flow in a subterranean formation around a well having unperforated casing fixed therein, the casing extending at least partially through the formation, comprising:

• creating at least one perforation in the casing communicating with the formation;
• placing a fluid in said casing opposite said perforation;
• setting a bridging means in the casing above said perforation to seal the casing above said means from said formation and said casing below said bridging means;
• injecting a stimulation fluid into the casing above the bridging means in an amount such that when pressure in the casing is released, the fluid pressure in the well at the depth of the perforation is greater than the fracture pressure of the formation;
• activating pressure release means in said bridging means such that pressure of said stimulation fluid is substantially instantaneously applied to the formation through said perforation whereby at least one fracture is formed in said formation;
• and
• injecting additional stimulation fluid into said created fracture to extend the created fracture in the formation.

A method for stimulating fluid flow in a subterranean formation around a well having perforated casing fixed therein, the casing extending at least partially through the formation and having at least one perforation in the casing opposite the formation comprising:

• setting a gun assembly in the casing proximate to the perforation;
• setting a bridging means in the casing above the gun assembly and above the perforation, to seal the casing above the gun assembly and perforation from the formation;
• injecting a stimulation fluid into the casing above the bridging means in an amount such that when pressure in the casing is released, the fluid pressure in the well at the depth of the perforation is greater than the fracture pressure of the formation;
• firing the gun assembly;
• activating the pressure release means in the bridging means such that pressure of the stimulation fluid is substantially instantaneously applied to the formation through the perforation whereby at least one fracture is formed in the formation;
• and
• at a time before pressure at the perforation has dropped substantially below the fracturing pressure of the formation, injecting stimulation fluid into the formation at an effective rate to extend the created fracture in the formation.