الصفحات

Showing posts with label completion. Show all posts
Showing posts with label completion. Show all posts

Thursday, March 8, 2012

Perforation (6)(SAFETY PROCEDURES)

2.7. GENERAL SAFETY PROCEDURES

The following comments are applicable to both TCP and wireline conveyed methods.
Additional comments are given in section specific to wireline conveyed perforating.
 
a) All perforating operations, since they involve the handling and use of explosives and possibly radioactive materials, require special safety procedures to be strictly observed at all times.
b) Perforating operations should be carried out strictly according to the safety policies of Eni-Agip and the perforating Contractor. In the event of any inconsistency between policies, the most conservative policy will apply.
a) Operations involving the use of explosives shall only be performed by
Contractor’s specialized personnel responsible for perforation and similar operations. The number of persons involved shall be as low as possible.
b) Only perforating Contractor’s personnel are allowed to remain in the hazardous area (gangway, rig floor etc.) during arming of guns. The number of personnel should be limited when the guns are within 500ft of surface when tripping in and out of the hole.
c) Any operation involving the use of explosives is not allowed in the presence of thunder, lighting and thick fog, as these are sources of electric potential.
d) Explosives shall be kept on site for the shortest possible time, any remaining at the end of the operation shall be removed from the installation.
e) Explosives shall be stored on site in proper containers, within a confined area on the rig. Detonators shall be stored in separate boxes, in the same area as explosives.
f) Warning signs must be placed around the hazardous area where explosives are used.
g) All radio transmitters, radio beacons included, within a radius of 500ft from the well, shall be turned off, (since they may detonate blasting caps), starting from gun arming until perforating guns are 500ft below the sea bottom (similarly, when pulling guns out of hole and guns above 500 ft). All portable transmitters (both Eni-Agip’s and Contractors) shall be placed inside the Eni-Agip office and turned off to avoid accidental transmission. Avoid critical periods of perforating coinciding with arrival and take-off of helicopters.
h) Cranes and welding machines shall be put out of service starting from gun arming till gun pulling out and unloading.
i) District Office shall be advised by the Well Operations Supervisor on the estimated time of radio silence two hours before starting operations. The Radio Operator shall communicate actual timing.
j) Casing perforating can be performed during daylight or at night. However, the first series of shots must be carried out in daylight hours. Before perforating casing, the acceptable cement job quality shall be ascertained by means of CBL/VDL and/or by squeeze jobs.
k) Explosives are to be transported unarmed and clearly labeled to the site in secure and protective containers. Extreme care must be applied during loading and off-loading.
l) At the rig it is the responsibility of the Installation Manager to ensure that these precautions are taken.
 
2.7.1.Firing Systems for TCP Operations
It is normal practice to run the TCP guns with two firing systems, whenever possible, to improve the chance of a successful operation especially when running the guns on the bottom of a completion. A common combination is to use a tubing pressure actuated system as the primary means of detonating the TCP guns with a mechanical system as the back up. There are four main types of firing mechanisms for TCP guns. Only top down firing mechanisms should be used for safety when arming the guns. The operation of each firing mechanism is:
2.7.2. Tubing Pressure Activated
The guns are fired by pressuring up the test string and then bleeding off the pressure immediately. A time delay device is incorporated to allow time to bleed off. This device can be either hydraulic or a slow burning fuse. Some of the firing heads for this system are wireline retrievable which gives another back up option. However, this would preclude the
use of the drop bar system as a back up. Although this technique could be expensive on nitrogen, it is well suited to the use of a nitrogen cushion but the time delay on the system will have to be increased to allow time for the nitrogen cushion to be bled off.
2.7.3. Mechanical Impact
The TCP guns are detonated by the mechanical impact of a firing bar, which for safety must be run on wireline. (This system is colloquially known as the drop bar system.) Since the system can be affected by debris in the tubing, the completion fluid must be kept clean. The system is preferred as a back up instead of the primary firing mechanism because of the need to use wireline.
2.7.4.Electrically Activated
With this system, the guns are fired with an electrically-initiated detonator which must be run on a logging cable. Therefore the pressure control system must be rigged up. Since an inductive or wet electrical connection must be made at the firing head, the system is also susceptible to debris. This system is rarely used on well tests as the only is that the firing heads for this system are wireline retrievable, hence the guns can be run unarmed and, in the case of a misfire, the firing head can be recovered on wireline to determine the cause of the misfire.
2.7.5. Retrievable Slick line Firing Head
This type of head was primarily designed to overcome the concerns over about the possibility of guns being denoted by stray pressure or tools/debris/unnamed articles which could fall down through the tubing string and force the detonating pin into the initiator. With this type of head, this possible problem has been completely eliminated due to the design of the system. The guns are run in the hole without the firing head. Then, when ready to arm the guns, the head is run to depth on slick line and latched on to the firing stem or stinger. This system
provides its own back-up in that if the firing head does not work, it can be retrieved and a replacement run.
Retrievable firing heads are available with mechanical, hydraulic or electric triggering.
Safety
Working with explosives is one of the most dangerous professions. While working with explosives you must concentrate on what you are doing. You must perform each step carefully and correctly. Because when shortcuts are taken, when concentration is broken, when communication fails, when respect for explosives is ignored, when instructions in the book are ignored, accidents can happen and they do happen.
Safe operating practices are critical to the long-term success of perforating.
Any deviation from these procedures can put lives and properties in danger. If precautions are not taken, the danger of premature detonation may occur!
Oil and gas are our main sources of energy and in all probability will be for a long time. The oil and gas industry is involved in finding and exploiting underground deposits of oil and gas in addition maintenance of the equipment used to provide a passage for hydrocarbon to flow from reservoir to the surface is also critical.
Due to the nature of work involved, hazards typical to the oil and gas industry operations exist. Therefore, in the oil and gas industry work and safety must go hand –In -hand.
Safety measurement includes:
Properly designed, constructed and tested equipment
Well-trained, highly qualified personnel
All perforating crew members receive training on the characteristics of the explosives they use and proper techniques for handling and transporting these explosives .perforating engineers and technicians also need to be proficient in the specialized process of gun arming and disarming. They should thoroughly understand procedures and applicable local regulations. In addition, only the engineer or technicians is permitted to arm or disarm the perforating guns on a perforating job.
read more "Perforation (6)(SAFETY PROCEDURES)"

perforation (5)(WIRELINE DEPTH CONTROL)


WIRELINE DEPTH CONTROL
Depth control for perforating is almost universally obtained through radioactivity instruments run in the cased hole in conjunction with the Casing Collar Locator (CCL). The Gamma Ray Log is generally used (Figure B28) though, in some cases, the Neutron Log or both Gamma Ray and Neutron are run. Accurate correlation of radioactivity logs with open hole logs establishes the position of casing collars with respect to the formation to be perforated. A short sub in the casing string is highly desirable to eliminate ambiguities with CCL identification, particularly when all joints of casing are about the same length. If the depth control log is made on a separate trip in the well, the proper shooting depth is determined on the perforating run by recording a second collar log with the collar locator attached to the perforator.
2.6.1.1. Gun-Gamma Ray Tool
If the combination Gun-Gamma Ray Tool is used, the entire equipment for depth control and perforating is run on a single trip in the well. The Gun-Gamma Ray Tool includes a rugged, shock proof gamma ray detector. A casing collar locator and a perforating gun can all run together. This offers greater assurance of accuracy and considerable saving of rig time. Depth control should always be used to accurately position TCP guns. A reference radioactive collar is run in the work string and its distance from the top shot is measured. Once on bottom, a through-tubing GR/CCL log is run and compared to open hole logs to establish how guns should be moved for exact positioning opposite the target formation. A variation of this procedure has been used from floating vessels in sand control completions. A sump packer is positioned and set with a wireline and becomes the locating device. The TCP gun string then is run with a locator and collet assembly on bottom. The distance from bottom gun shot to the collet latch is selected to place guns on depth. A radioactive collar should still be run to allow adjustment by logging in case of pipe tally discrepancies or slippage of the sump packer downhole.

2.6.2.2. Precision Identified Perforations
P.I.P. tags are used to provide a record of the position of perforations with respect to casing collars and/or formation boundaries. Special shaped charges fired at top and bottom of the perforated section leave traces of radioactive material within the perforations. The top and bottom perforations are then identified by sharp peaks on a Gamma Ray curve after perforating. Small size, low activity and short half-life of radioactive material used in the special charges prevent significant contamination of produced fluid. When run with Gun-Gamma Ray tool and Hollow Carrier perforators, no additional rig time is required other than that needed to log through the perforated interval.

2.6.2.  TCP DEPTH CONTROL
Four main techniques are used to ensure that the guns are at the correct perforating depth:
- Running a through-tubing gamma ray collar locator to locate a reference point in the string and tie into openhole logs.
- Setting the packer on wireline at a known depth, and stinging through the guns and completion string.
- Setting the packer and guns on wireline at a known depth, and stabbing the completion string in the packer.
- Tagging a fixed and accurate reference point such as a bridge plug. The first method is the most accurate. It relies on a radioactive marker sub in the string, and the distance from the radioactive marker sub to the top shot being precisely measured at surface. The string is run in the hole to approximately the correct depth and a short section of GRCCL (Gamma Ray-Casing Collar Locator) log is run over the zone where the sub is located. The gamma ray log indicates the position of the sub (a short radioactive peak anomaly) relative to the formation gamma ray as shown in Figure B30. As the distance from the sub to the top shot is known, the position of the guns can be calculated, and corrected if necessary by spacing out the string at surface. After the packer is set, the gamma ray may be rerun to ensure that the guns are at the correct depth. Fig. B30: TCP Depth Control Log.

As the cased hole gamma ray log can be considerably attenuated, a low logging speed will achieve better correlation results between the cased hole and the open hole gamma ray logs. If the formation gamma ray curve does not show much activity, a radioactive pip tag may be placed
As the cased hole gamma ray log can be considerably attenuated, a low logging speed will achieve better correlation results between the cased hole and the open hole gamma ray logs. If the formation gamma ray curve does not show much activity, a radioactive pip tag may be placed in or below one casing joint. (Placement of the pip tag must be included in the casing setting program.) Alternatively, a TDT or a neutron log can be run in place of the gamma ray log.



read more "perforation (5)(WIRELINE DEPTH CONTROL)"

Perforation (3) (Explosives Classifications)


Explosives Classifications
Explosives were invented first by the Chinese in the 10th century, then independently by the Arabs in the 13th century. The low explosive, or black powder, was characterized by slow reaction rates, 500 to 1500 m/sec, and relatively low combustion pressure. Much later, in 1846, the first high explosive was discovered by an Italian, Ascanio Sobreto, and then made commercially by Alfred Nobel in 1867 with the development of dynamite, a combination of nitroglycerin and clayey earth. High explosives, unlike the earlier low explosives, detonate at very rapid rates of 5000 to 9000 m/sec and generate tremendous combustion pressures. The terms low and high explosive are still used to characterize chemical explosives.
2.4.1.Low explosives (propellants)
 Are used in modern oilfield applications as power charges for pressure setting assemblies, bullet perforators and sample taker guns as well as for stimulation (high-energy gas fracturing, perf wash, etc.). High explosives are found in shaped charges, the detonating cord and detonators, and blasting caps.
2.4.2.High explosives 
 are further classified by their sensitivity or ease of detonation. 
2.4.2.1. Primary high explosives 
 are very sensitive and easily detonated by shock, friction or heat. For safety reasons, primary high explosives, such as lead azide, are used only in electrical or percussion detonators in Schlumberger gun systems.
2.4.2.2. Secondary high explosives  
are less sensitive and require a high-energy shock wave to initiate detonation (usually provided by a primary high explosive). Secondary high explosives are used in all other elements of the ballistic chain (detonating cord, boosters and shaped charges). PETN, RDX, HMX and HNS are secondary high explosives used in oilwell perforating. The rate of reaction, combustion pressure and sensitivity of chemical explosives are affected by temperature. Consequently, maximum safe operating temperatures are defined for all explosives. Exceeding temperature ratings may result in autodetonation or reduced performance. The table below lists the 1- and 100-hr temperature ratings and uses for the various explosives in gun systems.
 
2.4.3. Effect of temperature
Temperature affects the rate of reaction, combustion pressure and sensitivity of chemical explosives. Consequently, maximum safe operating temperatures are defined for all explosives. Exceeding the optimum temperature rating may result in autodetonation or reduced performance.
The table lists the 1-hr and 100-hrtemperature ratings and uses for the various explosives in schlumberger gun systems.
 
read more "Perforation (3) (Explosives Classifications)"

perforation(2) (Detonators)(guns)

Detonators

Perforating guns carry explosive charges to the borehole where they are detonated creating cylindrical holes in the casing and the cement. This allows oil and gas to flow from the formation into the well.

  The critical parts of the perforating guns are:
·        Detonating cord
·        Detonators
Detonators are divided into two main types:
·        Electrical detonators
·        Percussion detonators
Electrical detonators are known as blasting caps and are typically used in wireline operations.
Percussion detonators are generally used with tubing conveyed, coil tubing conveyedd and non-electric wireline systems
2.3.4.3. The S.A.F.E system
There are numerous safeguards implemented in both the electrical and percussion detonation systems. However, these conventional systems may explode accidentally when exposed to electric magnetic fields or other voltages found around the field.
The S.A.F.E. Slapper-Actuated Firing Equipment system was developed to be immune from the potential differences created by the radio-frequency(RF) radiation, impressed current from  corrosion cathodic protection, electric welding, high-tension power lines and induction motors such as top drives on drilling rigs.
S.A.F.E. equipment is available for most types of perforating / explosive assemblies run on wireline .
2.3.4.4. Key components of the safe system
The S.A.F.E. system initiates a gun firing without the use of any primary detonating material.
The key components of the S.A.F.E. System are the EFI or exploding foil initiator and the ESIC or the electrical secondary explosive initiating cartridge. The ESIC generates a unique signature of high voltage and current and rapidly discharges the pulse. The pulse is necessary to fire the EFI.
2.3.4.5.Operation mechanism of the S.A.F.E SYSTEM 

Let's now look at the detailed operation mechanism of the S.A.F.E system. Here we see an internal view of the EFI with the components identified
2.3.4.6.Secure Detonator
The secure detonator is a third-generation on S.A.F.E type device that also uses an EFI. it does not contain primary high explosives or a down-hole electronic cartridge. A microcircuit performs the same function as the electronic cartridge and EFI together in a package. It is similar in size to a conventional electric detonator. The secure system has all the technical advantage of S.A.F.E detonator, but is more reliable and fully expandable. It is also smaller in size and therefore allows the gun strings to be shorter.
Both secure and safe system fire using high voltage and current. Their electronic circuits are protected and they don't fire accidentally in case of malfunction. 
2.3.5. Casing guns
Casing guns are a type of carriers. Traditionally, casing guns were run on wireline to perforate wells before completion is run. 
There are two types of casing guns:
·      Reusable-carrier Port Plug Gun (PPG)
·      Expandable High-Efficiency Gun System (HEGS)
Both types of casing guns are fully retrievable.
Casing guns are designed as systems comprising specific carriers, detonating cords and boosters to provide maximum perforator performance. To ensure the performance meets design specifications, charges are quality control-tested during production in actual gun carriers.
Loaded casing guns contain only secondary high explosives (detonating cords, boosters and charges), allowing safe transport and handling when safety procedures are being observed.
2.3.6. Parameters of gun selection
After deciding to use wireline casing guns in the completion, the selection of the most appropriate gun depends on several parameters. These are:
·        Casing internal diameter
·        Bottomhole temperature and pressure
·        Deep penetrator or big hole application
·        Required shot phasing and density
·        Perforator performance and value

2.3.7. High shot density guns
High Shot Density (HSD) guns are another type of carrier guns. They comprise of specific carriers, charges, detonating cords and boosters to provide maximum perforator performance. HSD guns provide increased shot available for natural, stimulated or sand control completions.
HSD are the most flexible guns in the field. They are expandable, retrievable carriers and can be run on any type of conveyance (tubing, completion, slick line, TCP, wireline, coil tubing, etc.)
HSD gun features:
·        Expandable carriers
·        Shot density
·        Helical shot pattern
·        Automatic ballistic connection
·        Firing modes
·        Mechanical connections
·        Exclusive use of secondary explosives
·        Quality assured
HSD perforating guns incorporate shaped charges, detonating cord and detonators. Standard operating procedures must be followed when loading or running these gun systems. Loaded guns should be enclosed in protective tubes during storage to protect the exposed explosives.
Three critical tests are performed on HSD perforating guns for reliability testing. These are:
·        Mechanical / Pressure / Temperature test
·        Perforating gun Split / Swill test
·        Drop Test
2.3.8. Through-tubing Guns
Through-tubing guns are used primarily for underbalanced initial or subsequent completions that have the tubing and bottomhole assembly already in place. Optimal underbalance can be applied to achieve clean, productive perforations while maintaining absolute well control.
The through-tubing guns are designed as systems comprising of specific carriers, charges, detonating cords and boosters to provide maximum perforating performance.
Loaded through-tubing guns contain only secondary high explosives (detonating cords, boosters and charges), allowing safe transport and handling when standard safety procedures are being observed.
Through-tubing guns include:
1. The hollow carrier guns
2. The exposed guns
Types of hollow carrier guns
They include Scallop gun systems .these guns are fully retrievable and are the most rigged through-tubing guns, capable of withstanding the highest temperatures and pressures .the hollow carrier guns can be run at very high speeds .enerjet gun are wireline conveyed ,capsule charge -type ,perforating guns in the enerjet gun systems each shaped charge is encapsuled and loaded on a strip carrier rather than being enclosed in a hollow tube carrier.
This permits larger charges for the same overall gun diameter .Also, due to the greater charge size; enerjet guns outperform hollow carrier guns of the same diameter.
enrjet guns are classified into two main types
1.with retrievable carriers
2.fully expendable carriers
The retrievable system is designed for rugged conveyance while running down-hole .it provides shot verification.any charge that does not retrived from the well along with the carrier strip .as the carrier is retrieved there is less debris in the well. Expendable systems are useful for applications where well components or conditions make the retrievable of the carrier strip difficult after the gun is shot.
read more "perforation(2) (Detonators)(guns)"

Perforation(1)

     Overview
             Perforating is a critical part of any well completion process.
             The perforating process generates holes -perforation tunnels- in 
             steel casing surrounding cement and the formation.
                       In the past, perforation was regarded simply as holes in steel casing made .
                       By different methods. But perforation is not just a simple 
                           hole drilling process.Perforated completions play a crucial 
                       role in economic oil and gas production.
                       Long term well productivity and efficient hydrocarbon recovery.
2.2. History of Perforation in Brief
       1.      Prior to the early 1930's, casing could be perforated in place by 
         mechanical perforators. These tools consisted of either a single 
        blade or wheel-type knife which could be opened at the desired 
        level to cut vertical slots in the casing.
        2. Bullet perforating equipment was developed in the early
        1930's and has been in continuous and widespread use since that time.
            -The major drawbacks with this   method were that the bullet 
               remained in the perforation tunnel, penetration was not very good,
               and some casings could not be perforated effectively.
         3.       After World War II the Monroe, or shaped – charge,
          principle was adapted to oil well work, and the resulting 
           practice is now commonly referred to as jet perforating.
               -The principle of the shaped charge was developed during 
                World War II fo  armor piercing shells used in bazookas
                to destroy tanks. This new technology allowed the oil 
                producers to have some control over the perforating design 
               (penetration and entry hole size) to optimize productivity.
  2.3. Gun systems
2.3.1. Overview
In order to allow oil and gas to flow into the well, conduits
 need to be made into the formation. To do this, a gun is 
positioned across the producing formation and is detonated
 to create perforations through the casing and cement. 
The guns used for this purpose are known as perforating guns.
2.3.2. Perforating guns are divided into two primary categories:
·        Capsule guns
·        Carrier guns
2.3.3. The perforating gun performance is affected by the
·        Gun size
·        Clearance
·        Entrance hole diameter
·        Shot density
·        Gun phasing
·        Perforating length
·        Temperature rating
After firing the gun and while retrieving, unwanted solids enter 
into the wellbore or formation through perforating tunnels. 
These are called the perforating debris. Perforating debris 
can create problems in highly deviated or horizontal wellbores
 and can also create problems with the completion hardware.
Sources of debris are not only gun system, but also from 
the casing, cement and formation. 
Gun hardware contributing to debris are:
·        Gun body
·        Shaped charge liner slug and jet
·        Shaped charge case
·        Shaped charge retaining system (that holds the charge inside the gun).
2.3.4.1. Shaped charge liner
Perforating debris sources can be controlled if properly engineered.
 Shape charge liner used in deep penetrating charges is made of
 powder metal, which eliminates the carrot and slug associated with 
liner penetration into the formation during charge detonation.
Big hole charges us solid liners in order to produce large 
hole into the casing. However pf4621 power flow liners, 
produce big holes and yet leave no slugs into perforating tunnels,
 this new technology charge can replace the ultrapack charges.
Attempts are made to contain the debris in the gun, 
collect it after perforating or minimize the quantity expelled. 
To address this problem of controlling the debris,
 two methods are used. These are:
·        Zinc casing method
·        Patented packing method 
Additional techniques that contribute to reduced perforating 
debris include powder metal liners and non-plastic charge retention systems.
These recent innovations help in limiting problems arising from
perforation debris.
2.3.4.1.1. SHAPED CHARGE THEORY
The ultimate goal of perforating is to provide adequate productivity. 
Test laboratories evolved over the years to provide means of predicting 
and improving well performance. Today, the performance of the charges
 is determined according to the procedures outlined in the API RP 43 
 (standard procedure for evaluation of well perforators) fifth edition, 
published in 1991. From Figure B1 it can be seen that the penetrating
 power of a cylinder of explosive is greatly increased by a cavity at 
the end opposite to the detonator. Furthermore, placing a thin metallic
 liner in the cavity increases penetration. A typical shaped charge
 consists of four main components: a case, a high order explosive powder,
 primer and a liner, as shown in Figure shown
 The case simply holds all the components together.
- The explosive (RDX, HMX and HNS) is a complex mixture
 designed to allow packing and shipping in the case.
- The primer is a purer mixture of explosive which is more sensitive
to the detonation of the detonating cord.
- The liner is used to form a jet which physically does the perforating.
- The detonating cord, which is initiated by a blasting cap, detonates
 each charge.
The selection of explosive material is based on the well 
temperature and anticipated exposure time at that temperature (Figure B3).
 RDX, HMX and HNS are all explosives used in oil well shaped charge
manufacture. For deep penetrating charges, the liner is made from a mixture
 of powdered metals pressed into the shape of a cone. High precision in
 the pressing operation is required and it must be done in an extremely
 uniform and predictable manner. For Big Hole charges, the liner is
 drawn from a solid sheet of metal into hemispherical, parabolic, 
or more complex shapes. 
For each of the two types of charges, there is a trade-off between 
entrance hole size and penetration. The sequence of events in 
firing is illustrated in Figure B4 from top to bottom. 
The detonator initiates the cord which detonates at a rate 
of approximately 7000 m/s (23,000 ft/sec.) The pressure impulse 
from this detonation initiates the primer in the charge and the
 explosive begins to detonate along the length of the charge. 

The high pressure wave 30x106 kPa, 4,500,000 psi) strikes 
the liner and propels it inward. The liner collapses from 
apex to skirt imparting momentum with a velocity approaching 
2500 m/s (8000 ft/sec). At the point of impact on the axis 
the pressure increases to approximately 50x106 kPa (7,000,000 psi) 
and from this high pressure region, a small amount of material is 
propelled out at velocities in excess of 7000 m/sec (23,000 ft/sec).
As the liner collapses further down the cone, more and more material
 must be propelled by less and less explosive such that the 
impact pressure is substantially less. Thus the tip of this so-called
 jet is travelling 20 times faster than the rear portion and gives the
 elongated shape to the jet. The penetration depth depends on this
stretching action. As the liner walls collapse inward, the resultant 
collision along the axis divides the flow into two parts, as in 
Figure B5. The inner surface of the liner material forms 
the penetrating jet which is squirted out along the charge. 
The outer surface of the liner, which was in contact with the explosive, 
forms a rear jet or slug which moves forward slower than the forward jet.
 In the zone of collision, where division of the material forming the jet
 and slug takes place, there is a neutral point which moves along the axis
 as the liner collapse process continues. The very fast jet impacting 
a casing generates a pressure of approximately 70x106 kPa (10,000,000 psi). 
At this pressure the steel casing flows plastically and the entrance hole is formed.
A similar behavior occurs with formation material as the jet penetrates.
 In addition, crushing and compacting of the formation material around
 the perforation may also occur. The entire process from detonation
 to perforation completion takes from 100 to 300 microseconds.
 The jet material arriving last at the target, making the end of the perforation,
 comes from the skirt or base. As discrete portions of the jet strike at this
 end of the hole, they penetrate, expending their energy in the process. 
Portions of the jet continue the penetration process, until the entire jet is expended.
 The perforation occurs so fast that, essentially, no heat is transferred.
 Indeed, it has been demonstrated that a stack of telephone directories
 can be penetrated without singeing a single page. It follows that no fusing 
of formation material occurs during penetration. However, crushing and 
compacting of formation material is to be expected, and will be reviewed later.










   

2.3.4.1.2. SHAPED CHARGE DESIGN
Liner aspects, such as geometry, angle, material, and distance from base to apex,
 as well as stand off, and explosive density are more important  than the amount
 of explosive (Figure B7a). Only about 20% of the available explosive energy 
goes into the useful jet. It has been proven that properly designed charges
 can out perform poorly designed charges that have twice the explosive load.


 This is important in situations where a higher explosive load causes 
casing damage. Once a charge is designed for entrance hole and 
penetration efficiency, manufacturing quality control and 
consistency become significant in shaped charge performance.
 Perforation efficiency is accomplished with maximum penetration,
 uniform crushed zone, and minimal plugging due to slug debris. 
This is achieved by designing a liner that will provide 
a uniform jet diameter and velocity with little to no deviation from the conical liner axis. For example, it is critical that the liner thickness and density be precise around the cone at any given point away from the apex. Figure B7b is an example of a less desirable jet due to poor quality control
read more "Perforation(1)"