Abstract

Ballistic perforation remains a fundamental part of the process of producing valuable hydrocarbon deposits. The basic technique of lowering a gun containing shaped charges into a well is essentially unchanged since the 1930's, but the method of deployment has undergone many improvements. This paper intends to examine the benefits and advantages of using new carbon composite materials technology in increasing the efficiency and effectiveness of perforation.

The semi-stiff carbon rod is very strong, rigid, has low friction and contains an electrical conductor. These factors all combine to confer significant advantages over wireline for deploying perforation guns. The simplest benefit is that the strength of the rod makes rigging up and running very long and heavy gun strings feasible, reducing the number of runs in hole required to perforate a given interval. The rigidity of the rod reduces the risk of being blown up-hole by pressure differentials, thus allowing more potential underbalance than when using wireline while the conductor allows the use of addressable select fire systems.

Economic management of a well will almost certainly involve some intervention during its lifetime. A not uncommon example is a well where depletion has moved reservoir contacts and re-perforation becomes desirable to maximise recovery. If deviation is high, as in a recent well in the North Sea, a tractor intervention will be required and due to the constraints of a conventional cable deployment, gun lengths will be limited resulting in multiple runs. The carbon composite rod system was able to halve the number of runs required to perforate the new interval resulting in a considerable saving.

Many wells may not be horizontal but have a sustained section at high angle which precludes the use of wireline alone. The low friction of the rod and the ability to push it into hole allows access without recourse to a tractor, while the stiffness prevents movement of the string uphole after shooting, allowing significant underbalance to be applied with all the attendant benefits to reservoir performance. Combining new developments in selective firing and flexible gun systems with the attributes of the rod allow access to zones below known restrictions which are currently impassable by tractor or any other conventional deployment system.

Demonstrating the ability of the carbon composite rod system to save time and perforate longer sections more economically allows optimised planning. Eliminating concerns over gun lift, especially in high deviations, gives far more flexibility for planning underbalance perforation with all its intrinsic advantages. The electrical conductor in the rod enables the use of addressable select fire systems and head tension devices that, along with the ability to push the BHA, allows entry through otherwise impassable restrictions.

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