| Tubing Conveyed Perforating (TCP) Systems Guns to cover production intervals are assembled. A firing head is placed on top and/or bottom of the guns. The perforating assembly is run on the desired pipe string with a sub with a marker sub installed above the packer for positive depth positioning. All components of our TCP assembly are measured before tripping into the hole. The strapped distance from the top shot to the marker sub is carefully established. When perforating depth is reached, a gamma ray or neutron depth-control log is run inside the tubing. This log locates the exact position of the TCP assembly with respect to the open hole log from which perforating intervals were selected. Additionally, the gun assembly may “tag” an electric line set sump packer and raise pipe to place the system at the correct depth. An underbalance tool assembly allows the tubing to be run dry or with the proper fluid cushion. Various types of underbalance methods are available for specific completion applications. Underbalance assemblies can be opened by dropping the detonating bar. Some tools close additional ports with hydrostatic pressure used during shoot and pull applications. Various vent assemblies are used for both completion and gravel pack perforating. All wellhead work is completed before charges are detonated. The blowout preventer is removed and the wellhead is installed. A choice of mechanical or pressure-actuated firing systems is available, eliminating the dangers of electrically detonated blasting caps. Immediately after guns are detonated, differential pressure to the wellbore backsurges debris, mud filtrate and other contaminates, along with any rathole fluid, to the surface. Backsurging can be performed at pressure differentials as high as 5,000 psi. Or, if sand is expected, back pressure can be maintained with a fluid cushion in the tubing. Some operators use nitrogen gas to hold back pressure during perforating and to “bring” the well in easily. In most cases, natural cleanup is finished quickly. A gun release system - auto, mechanical, or hydraulically actuated - provides a safe, economical and dependable means of releasing guns after perforating. For the mechanical release, a shifting tool is run on slickline to shift a latch sleeve, which releases the guns into the rathole. Tubing may be left open-ended so ball sealers or other diverting agents can be used. Smith Services supplies the perforating system to perforate your underbalanced well. Prior to a conventional gravel pack with Smith or a high rate pack:
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