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.
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