1. Well Perforation
Perforation  is the process of creating holes in production casing to establish communication between the well and formation.
Perforation holes are used to recover formation fluid, as well as to inject into formation or, gas, cement or other agents.

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In cased hole completions, the well will be drilled down past the section of the formation desired for production and will have casing or a liner run in separating the formation from the well bore.
The final stage of the completion will involve running in perforating guns, a string of shaped charges, down to the desired depth and firing them to perforate the casing or liner.
A typical perforating gun can carry many dozens of charges.

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Commonly, perforation guns are run on E-Line as it is traditional to use electrical signals from the surface to fire the guns.
In more highly deviated wells, coiled Tubing may be used. Newer technologies allow the guns to be run on slick line.
Slick line looks like a long, smooth, unbraided wire, often shiny, silver/chrome in appearance. It comes in varying lengths, according to the depth of wells in the area it is used (it can be ordered to specification) up to 35,000 feet in length.
Slick line is spooled onto a hydraulically controlled drum in the back of a wire line truck

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No communication with the surface is possible with slick line. Instead, a mechanism on the gun arms the charges upon reaching a certain temperature and pressure. A timer will then fire them following a set interval.
The benefit of this strategy is greater deal of control of the well.
Casing the bottom of the hole allows the well to be completed without having to worry about reservoir fluids.
The disadvantage is that perforating can lead to "skin damage", where debris from the perforations can hinder productivity of the well.
In order to mitigate this, perforating is commonly done under balanced (lower pressure in the well bore than in the formation) as the higher formation pressure will caused a surge of fluids into the well at the point of perforating, hopefully carrying the debris with it.

5. Shaped Charges
A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy .
The shaped charge is made up of five components.
1, The main explosive charge
2, The cavity covered with a cone shaped metal Liner.
3, The Primer charge
4, The Detonating cord
5, A Case.

6. Shaped Charge/Bullet

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8. Perforation Gun

9. Types Of Perforation
Over Balanced Perforation: These perforations are made before running the down hole equipment( tubing etc), while the well is full of completion fluid exerting hsp to counter reservoir pressure.
Here a large gun can be run directly through the casing with the following advantages.
1, Large explosive loads
2, multiple shot directions with good penetration.

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Perforation Under Balanced. These Perforations are made after well equipment has been run in and once the production tree has been installed, with the well full of a light fluid having hsp lower than the reservoir pressure.
The guns are run into the well through the tubing, by means of an electric cable.
Because of the pressure under balance, plugging is reduced or even avoided during and after the firing. Additionally, since all the well equipment is in place there are no added safety problems and the well is ready to be cleared.

11. Continue TCP Perforating (Tubing Conveyed Perforator).
Here Guns are run directly with the tubing . The advantages of of TCP Perforation are
2, They can be fired with under balanced pressure and with the permanent well equipment in place if so desired.

12. Radial Penetration