Boring or penetrating the earth – Boring with explosion in inaccessible hole – With wall engaging packer or anchor
Reexamination Certificate
1999-10-28
2001-04-24
Schoeppel, Roger (Department: 3672)
Boring or penetrating the earth
Boring with explosion in inaccessible hole
With wall engaging packer or anchor
C175S004560, C166S055100, C166S297000, C102S320000, C102S323000
Reexamination Certificate
active
06220370
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a tubing conveyed perforating gun system of the type used to perforate a well bore for the production of well bore fluids, and, specifically, to such a system with internal components designed to decrease firing debris and to allow reverse washing of fill encountered in the well bore, without tripping the system out of the well.
2. Description of the Prior Art
As oil and gas wells are being drilled, the integrity of the borehole is preserved by cementing a casing or liner in place in the borehole. The casing or liner is a metal cylindrical conduit which must be punctured or perforated over the desired production interval in order to produce well bore fluids once drilling is complete. A perforating gun which utilizes some form of fired projectile and an explosive charge is used to perforate the casing or liner to begin production from the well.
Prior perforating gun techniques have either utilized tools which were run on a wireline or cable or have utilized tubing conveyed devices which were run on a tubing string to a desired depth in a well bore. Tubing conveyed devices have certain advantages over wireline methods. For example, tubing conveyed devices allow safe, immediate release of formation pressure at maximum pressure differentials into the tubing string. With tubing conveyed perforating systems, the tubing can be run into position, a packer set to seal off the well bore, and the surface wellhead equipment can be installed. The packer setting can be checked by circulating fluid under pressure through the well annulus or through the well tubing string. Once the surface work is completed and tested for safety, the perforating gun can be fired to bring in the well. Tubing Conveyed Perforating (TCP) systems provide rig time savings, higher shot density, greater gun length and the ability to perforate “under balanced” so that perforations are cleansed through formation fluid backflow. Since perforating guns can be run below the production tubing they enable the well to be perforated and completed, i.e., put into production, in one operation.
Occasionally, sand fill has infiltrated into the well and causes problems with gravel packing or other well bore operations. It is thus desirable to provide an apparatus having the capability of reverse circulating the fill out of the well. Obviously, it is desirable to accomplish the reverse circulation of the fill out of the well without having to pull the work string, gravel packing and/or perforating apparatus.
In wells utilizing a sump packer below the zone to be perforated, it is necessary for the perforating string to have its lower end sealingly engaged with a bore of the sump packer prior to performing the desired well bore operation. With the prior art systems, if sand fill was encountered on top of the sump packer, it was generally necessary to trip the perforating apparatus and its associated tool string out of the well. A work string was then run into the well to reverse circulate the sand fill away from the sump packer. The work string was then required to be tripped out of the well so that the perforating tool string could again be run into the well. Often times, as many as three trips in and out of the well were required before the entire operation could be accomplished.
The present invention has as one object to provide a tubing conveyed perforating apparatus with means for reducing the accumulation of firing debris within the well bore at the conclusion of the firing operation.
Another object of the invention is to provide such an apparatus which allows for the reverse circulation of sand fill encountered within the well bore, such as sand fill encountered directly on top of a sump packer located within the well bore.
Another object of the invention is to provide a tubing conveyed perforating apparatus which allows the plug in a sump packer to be placed and released, perforation of the well casing, reverse circulation of fill and/or debris from the top of the sump packer, and subsequent retrieval of the plug from the sump packer.
Another object of the invention is to provide such an apparatus which is relatively simple in design and economical to manufacture.
SUMMARY OF THE INVENTION
The tubing conveyed perforating apparatus of the invention is used in perforating a surrounding well bore. The apparatus comprises a tubular assembly made up of a plurality of tubular sections. The tubular sections present a generally cylindrical exterior and a concentric interior bore. The tubular assembly has an upper connecting end for connection in tubing string extending to the well surface and a lower end. At least one of the selected tubular sections comprises a tubular firing section having a plurality of explosive charges carried therein. Each of the explosive charges is initially aligned with a region of reduced wall area provided within the tubular firing section surrounding the charges. A piston sleeve is mounted on the exterior of the tubular firing section. The piston sleeve has a plurality of apertures therein which are initially aligned with the regions of reduced wall area in the tubular firing section and thus with the explosive charges. A firing means is located within the tubular assembly for detonating the explosive charges to perforating the surrounding well bore. The piston sleeve includes a piston area which communicates by means of an internal port with the interior bore of the tubular firing section. Detonation of the firing means applies a force to the piston area to shift the piston sleeve, thereby moving the piston sleeve apertures out of alignment with openings formed in the tubular firing section due to detonation of the explosive charges. This action serves to trap any resulting explosive debris within the interior bore of the tubular firing section.
In addition to utilizing the force of explosive gases to shift the piston sleeve, well hydrostatic pressure can be utilized to apply a force to the piston area to shift the piston sleeve, the well hydrostatic pressure being communicated to the interior bore of the tubular firing section upon detonation of the explosive charges. Detonation of the explosive charges creates openings in the tubular firing section at the regions of reduced wall area, thereby forming a temporary flow path to the interior bore of the tubular firing section.
Preferably, a plurality of tubular firing sections are connected end-to-end in the tubular assembly, the firing sections being connected by ignition means for detonation by the firing means.
The lower end of the tubular assembly can carry a sealing plug which is designed to seat within a mating bore of a sump packer located within the well bore. The sealing plug is preferably connected to the lower end of the tubular assembly by a shear means, whereby setting weight on the tubing string shears the shear means to release the lower end of the tubular assembly from the sealing plug. A piston actuated retrieving assembly can be located within the lower end of the tubular assembly above the sealing plug. The piston actuated retrieving assembly has a reactive piston area which is exposed to forces applied by the firing of the explosive charges and/or well hydrostatic pressure to shift the retrieving assembly downwardly within the lower end of the tubular assembly. The lower end of the tubular assembly can also be provided with one or more bottom circulation ports for ultimately communicating the interior bore of the tubular assembly with the surrounding well annulus. Movement of the piston actuated retrieving assembly downwardly within the tubular assembly serves to uncover the bottom circulation ports.
The piston actuated retrieving assembly preferably includes a fishing head at a lower extent thereof which includes a colleted opening for engaging a mating surface provided on the sealing plug for retrieving the sealing plug from the bore of the sump packer. The piston actuated retrieving assembly includes an intermediate length between the rea
Andrich Lyle W.
Wesson David S.
Williger Gabe
Gunter, Jr. Charles D.
Owen Oil Tools, Inc.
Schoeppel Roger
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