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2. 2. Casing Gun Perforating System 
The basic technique includes establishment of a 
suitable underbalanced pressure condition by 
swabbing the well down. The advantages and 
disadvantages of this system can be summarized as 
follows: 
1.
The system is simple and effective, 
especially for low reservoir pressure and 
limited drawdown. In addition, the guns 
provide substantially higher performance 
than smaller, through tubing ones. 
2.
The system is economically feasible because 
of the simplicity of the surface pressure 
control. 
Disadvantages 
1.
Laboratory investigation
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of perforating 
damage of Berea sandstone has shown the 
existence of permeability reduction for the 
compacted zone of about 10 to 20 % of that 
of the undisturbed rock.
2.
The resultant compacted zone
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for Berea 
sandstone could reduce flow from 
perforation to about 30 % of the flow either 
if the compacted zone were did not exist, or 
if the rock had a virgin (undisturbed) 
permeability.
3.
The technique
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is restricted to single-gun 
runs because of the underbalanced condition. 
2. 3. Tubing Conveyed Casing Gun
Perforating System 
The Tubing Conveyed Perforating system
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(TCP) 
has been widely used successfully in many oil fields 
throughout many countries of the World. It is a 
method of perforating the well casing using 
perforating guns suspended from jointed tubing. In 
this method, the well may be closed, empty, or 
partially filled tubing. Then, a hollow carrier is run 
into the well, as shown in 
Fig. 1
.
While the packer is set, a packer actuated venting 
assembly relieves the hydrostatic pressure below the 
packer. At this time, a bar is dropped down the 
tubing to detonate the perforating gun. 
Instantaneously, formation fluid surges into the 
casing and up into the empty tubing through the 
perforations. The perforated guns can be assembled 
for any required length and shot density. The 
combination of a hollow carrier gun (to gain deep 
penetration) and the flushing effect (as much as 
1,000 to 5,000 psi differential pressure) has to 
provide ideal perforations with only a small effect 
long clean channels in a penetrated formation with 
small effect from the penetrating bullet. When the 
required application conditions of the underbalanced 
Vannsystem are satisfied, many advantages over 
other perforating systems can be offered, as follows: 
1.
There is an ability to run the perforator on 
the end of the tubing string and longer or 
multiple intervals
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can be perforated on a 
single trip.
2.
This system can be used under higher 
underbalanced pressure drop safely, 
especially for testing high-pressure, H
2
S 
wells.
3.
The perforator can pass through the 
permanent packer and be located opposite 
the Cockfield zone.
4.
Later, the guns can be dropped into the rate 
hole (below the perforators) to allow 
unrestricted flow to the surface.
5.
This system provides the ability to use the 
flow capacity (Kh) to predict the open-hole 
flow potential and calculated absolute flow 
(CAOF) safely.
6.
The results of this system usually match or 
surpass open-hole DST rates. This provides a 
good chance for detecting the percentage of 
perforating damage, if present. 
7.
This system is suitable for highly deviated 
wells.
8.
This system provides higher well 
performance under varied completion 
conditions. 
Disadvantages: 
1.
This system costs almost 25 % more than 
other perforating techniques, and
2.
More improvement is needed for attaining 
proper detecting of gun firing and for 
reducing gun exposure time. 
The problem to be overcome in Bahariya formation 
(Egypt) is to increase the minimum of the producing 
formation for Melehia lease. This formation is 
mainly of lower Cenomanian Age and is 
characterized by a sequence of interbedded 
argillaceous sandstone and shales with subordinate 
carbonates. 
Because of poor reservoir characteristing the 
Bahariya formation is easily damaged during drilling, 
cementing and completion operation due to the poor 
reservoir characteristics. Even at virgin pressure, the 
formation is unable to produce naturally, and the 
wells are produced artificially by sucker rod system. 
For wells without formation damage, the well 
production is maximized by the pump capacity. In 

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SPE 
114793 
the other cases where the formation is damaged, the 
impairment in productivity limits the rate at which 
the pump can be operated. To cure the problem, the 
conventional tubing conveyed perforation technique 
was tried, butt this still required to kill the well 
between perforation and running the pump. 
Mahfouz
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presented the development of a novel gun 
firing techniques, which enable running the gun 
strings with sucker rod pump installation. He also 
introduced the design features of the system 
components and its economic feasibility in 
comparison to other perforating techniques.