Tubing-Conveyed Perforating

Tubing-conveyed perforating (TCP) technology has grown dramatically duringthe past 5 years.
This paper presents a general overview of state-of-the-artTCP systems and operating techniques
and discusses the TCP benefits and thetradeoffs involved in the use of conventional wireline
perforating. The TCP gunstring, with spacers and selected accessories, is run into the well on the
termination of a testing or completion string, and the guns are positioned across the zonesof
interest (Fig. 1). When the TCP string is positioned with a nuclear-typelogging device, the surface
well-control equipment installed, and the desiredpressure underbalance established, the guns are
fired. The result is pressure underbalance recognized, the guns are fired. The result is concurrent
perforation of all selected intervals with high-performance gun systems in anoptimal pressure
environment.
Benefits of TCP
Operational Efficiency. TCP allows the well operator to perforate long, orwidely spaced, intervals
simultaneously on a single trip into the well ratherthan having to make multiple runs on wireline.
The difference between TCP andwireline-perforating rig time depends on interval length and the
number ofwireline descents vs. the additional time to position the string and to readythe well for
TCP operations. However, TCP exposes the gun to the wellenvironment longer than wireline
perforating, a concern in high-temperatureoperations. TCP gives the well operator an opportunity
to perform a flow testimmediately after perforating. Impulse type testing techniques can be used
toidentify the extent of wellbore damage before large investments in stimulationor gravel packing
are made. In addition to impulse testing, a variety of othertesting and completion equipment can
be combined with the TCP string to providefor comprehensive reservoir evaluation immediately
after perforating.
Underbalanced Perforating. An underbalance, established between theformation and wellbore

pressures before the TCP guns are fired, creates aninstantaneous and controlled surge of
formation fluids into the well, whichcleans the perforations and enhances the well's productivity
andinjectivity.
Safety. Surface well-control equipment is installed and tested beforeperforating, guaranteeing

complete safety throughout all phases of the TCPoperation. phases of the TCP operation. High-
Performance Perforating Systems.Gun size is limited by the ID of the casing, permitting use of
the largestpossible charges permitting use of the largest possible charges (either
deeplypenetrating or big-entry-hole type) and high shot densities. Guns can beconfigured to
provide the optimum shot density and pattern for the specificapplication.
TCP Completion Types
Temporary TCP Completions. In a temporary TCP completion, the guns are runinto the well at
the end of a workstring. After the guns are fired, and time isallowed for cleanup and testing, the
well is killed with a nondamagingcompletion fluid and the TCP string is removed.
Completionprocedures-backwashing, acidizing, procedures-backwashing, acidizing,fracturing, or
gravel packing then be implemented. Large Intervals or MultizoneWells. Large intervals or wells
where several widely spaced zones arecommingled into a single production string are completed
efficiently productionstring are completed efficiently on a temporary workstring. After
perforating,the well is killed with a nondamaging perforating, the well is killed with anondamaging
completion fluid and the gun string is removed. This system affordsthe benefits of TCP while
providing an alternative to leaving the gun string inthe well where it could interfere with future
operations. Gravel-Packed Wells.High-shot-density TCP guns loaded with big-entry-hole charges
shotunderbalanced are used to perforate a zone to be gravel packed. After perforatea zone to be
gravel packed. After cleanup, the well is killed with anondamaging completion fluid and the guns
are retrieved to permit the runningof screens and installation of the gravel pack. Testing. A well-
control valvecan be used in conjunction with TCP to provide a quick look at thenear-wellbore
region by impulse testing. A longer-duration drillstem test (DST)provides for a more detailed
analysis of the commercial potential of thereservoir through observation of the types of fluids
recovered and the flowrates. The DST/TCP combination ensures optimum perforation cleanup
and providesreservoir performance characteristics. The system involves TCP guns run below
aretrievable packer and a set of DST tools. Immediately after firing, the wellis tested by
alternately flowing and shutting in to develop the desiredreservoir information.
Permanent TCP Completions. In a Permanent TCP Completions. In a permanentTCP completion,

the guns are run of permanent TCP completion, the guns are runof the end of the final completion
string. The wellhead and safety equipmentare installed before firing. The guns remain in the well
after the perforatingoperation and may be dropped into the rathole if desired.

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Tubing-conveyed perforating (TCP) technology has grown dramatically duringthe past 5 years.

Underbalanced Perforating. An underbalance, established between theformation and wellbore

Safety. Surface well-control equipment is installed and tested beforeperforating, guaranteeing

TCP Completion Types

Permanent TCP Completions. In a Permanent TCP Completions. In a permanentTCP completion,

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