Perforating gun for oil and gas wells, and system and method for using the same

1. A well casing perforation system for perforating a well casing within a subterranean well, the well casing containing a well fluid, and the well casing having an inner passage defined by an inner surface, comprising:

a perforating gun having a cylindrical body with an outer radial surface, the cylindrical body extending between a first axial end and a second axial end, disposed opposite the first axial end, wherein the cylindrical body is configured to have the second axial end disposed downhole of the first axial end during use, and the cylindrical body is configured to produce an annular region within the well casing between the outer radial surface of the cylindrical body and the inner surface of the well casing, the perforating gun further including a plurality of shaped charges mounted within the cylindrical body between the first axial end and the second axial end, and at least one initial propellant disposed on the outer radial surface of the cylindrical body axially between the plurality of shaped changes and the second axial end and configured to drive the well fluids within the annular region away from the plurality of shaped charges upon being fired in a direction from the second axial end toward the first axial end; and

a controller configured to selectively cause the perforating gun to actuate when the perforating gun is disposed within the well casing, which actuation of the perforating gun includes first causing the at least one initial propellant to fire and to cause the volume of elevated pressure gas to drive the well fluids within the annular region away from the plurality of shaped charges for a period of time, and second causing the plurality of shaped charges to fire during the period of time.

2. The system of claim 1 , wherein the at least one initial propellant is a solid propellant.

3. The system of claim 2 , wherein the solid propellant includes at least one of potassium perchlorate, ammonium perchlorate, or barium perchlorate.

4. The system of claim 1 , wherein the perforating gun includes a mechanically operated actuating mechanism, and the controller is configured to cause actuation of the perforating gun actuating mechanism.

5. The system of claim 1 , wherein the perforating gun includes an electrically operated actuating mechanism, and the controller is configured to cause actuation of the perforating gun actuating mechanism.

6. A method of perforating a well casing within a subterranean well, the well casing containing a well fluid, and the well casing having an inner passage with an inner diameter surface, the method comprising:

providing a perforating gun having a cylindrical body, a plurality of shaped charges, and at least one initial propellant, the cylindrical body extending between a first axial end and a second axial end disposed opposite the first axial end, the cylindrical body having an outer radial surface, the plurality of shaped charges mounted within the cylindrical body between the first axial end and the second axial end, the at least one initial propellant disposed on the outer radial surface of the cylindrical body axially between the plurality of shaped charges and the second axial end, and wherein the cylindrical body outer radial surface is disposed at a first diameter and the well casing inner diameter surface is disposed at a second diameter, and the second diameter is greater than the first diameter;

disposing the perforating gun within the well casing inner passage with the second axial end of the cylindrical body downhole of the first axial end of the cylindrical body, and at a position where an annular region is formed between the cylindrical body outer radial surface and the well casing inner diameter surface and the annular region is filled with said well fluid;

driving the well fluid within the annular region in a direction from the second axial end of the cylindrical body toward the first axial end of the cylindrical body and out of the annular region by firing the at least one initial propellant disposed axially between the plurality of shaped charges and the second axial end, the propellant firing producing an amount of gas in the annular region at an elevated pressure relative to the well fluid, the amount of gas in the annular region at said elevated pressure maintaining the well fluid out of the annular region for a period of time; and

perforating the well casing by firing the plurality of shaped charges during the period of time in which the well fluid is maintained out of the annular region.

7. The method of claim 6 , wherein the perforating gun includes a mechanically operated actuating mechanism, and the at least one initial propellant is fired by engaging the mechanically operated actuating mechanism.

8. The method of claim 7 , wherein the mechanically operated actuating mechanism is engaged by a drop bar impact.

9. The method of claim 6 , wherein the perforating gun includes an electrically operated actuating mechanism, and the at least one initial propellant is fired by engaging the electrically operated actuating mechanism.

10. The method of claim 9 , wherein the electrically operated actuating mechanism is engaged by a signal sent from a well control station.

11. The method of claim 6 , wherein the perforating gun includes a pressure operated actuating mechanism, and the at least one initial propellant is fired by subjecting the perforating gun to a predetermined first elevated pressure.

12. The method of claim 11 , wherein the plurality of shaped charges are fired by subjecting the perforating gun to a predetermined second elevated pressure, which second elevated pressure is greater than the first elevated pressure.