Wells – Processes – Graveling or filter forming
Reexamination Certificate
1999-12-20
2001-03-27
Tsay, Frank S. (Department: 3672)
Wells
Processes
Graveling or filter forming
C166S297000, C166S055100
Reexamination Certificate
active
06206100
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatuses and methods for the completion of mineral production wells. In particular, the invention is related to a perforating and gravel packing system and method.
Modern oil and gas wells are typically equipped with a protective casing which is run into the wellbore. Production tubing is then run into the casing for producing minerals from the well. Adjacent the production zones, the protective casing is perforated to allow production fluids to enter the casing bore. Since particles of sand are typically carried with the mineral from the production zone into the casing, it is sometimes necessary to install a gravel pack or production screen to filter the particles of sand. Therefore, it is common practice to complete a mineral well in two steps: (1) run-in the well with a perforating gun to perforate the casing; and (2) run-in the well with a gravel pack tool to gravel pack and/or isolate the perforated zone. However, this method is disadvantageous because it requires multiple trips into the well to perforate and gravel pack the zone.
To reduce the required number of trips into the wellbore casing, various single trip perforation/gravel packing devices have been developed. For example, as described in U.S. Pat. No. 4,372,384, incorporated herein by reference, a single trip apparatus for completing a formation in a case borehole is disclosed. The patent teaches the use of a tool string which includes a perforating gun, gravel packing tools and a packer means. The casing is perforated by running a gun firing device down through the tubing string. The well is allowed to flow freely to clean up the perforated formation. The system is then moved to position a sandscreen of the gravel packer adjacent the perforations and packers are used at each end of the screen to straddle and pack off the perforated pay zone. With the screen and packers in position, a gravel pack is established in the annulus between the perforated casing and the screen. The tool screen is left downhole in the casing as a permanent completion device. The produced fluid is allowed to flow through the perforations, the gravel, screen, and finally up through the tubing screen to the surface.
An alternative well completion system is disclosed in U.S. Pat. No. 5,954,133, incorporated herein by reference. In particular, a method of displacing a perforating gun in a well bore is used to perforate multiple zones without the need to unset or reset a packer. Multiple perforating guns in a positioning device are configured in an axially compressed configuration. The perforating guns are attached to the positioning device and inserted into the wellbore. With a first perforating gun positioned adjacent a first zone, the gun is fired to perforate the casing. The positioning device is then extended to axially displace a second perforating gun within the casing to a position adjacent a second zone. The second gun is then fired to perforate the casing. After a zone(s) has been perforated, the positioning device is further axially extended to displace a production screen and packer. The production screen is positioned adjacent the perforations and the packer is positioned opposite the perforations.
As illustrated in the above referenced patent documents, in traditional one-trip systems, the perforating gun assembly is mechanically connected to the gravel pack assembly during run-in and perforating operations. A basic problem with traditional one-trip perforation/gravel packing systems is that the gravel packing portions of the system are damaged when the guns of the perforation portion of the system are detonated. In particular, a major factor affecting the reliability of one-trip perforation/gravel packing systems is the effects of gunshock on the gravel pack assembly. This shock loading can be in the form of a mechanical force which is communicated through a pipe string or similar structure correcting the perforating guns to the gravel packing assembly. Alternatively, a pressure wave created during detonation in the fluid column inside the wellbore casing can damage the gravel packing apparatus due to a shock effect It has been very difficult to predict the size of this shock effect and even more difficult to prevent it.
Therefore, there is a need for a one-trip perforation/gravel packing system which is more reliable than traditional systems in that the gravel packing portion of the system is protected from gunshock generated by the guns of the perforating portion of the system.
SUMMARY OF THE INVENTION
The present invention is a system and method of operation which performs both the perforating and gravel packing operations during a single-trip into a wellbore, and which also protects the gravel packing portion of the system from becoming damaged when the guns of the perforating portion of the system are detonated. The process that is described here represents a novel approach which involves a modification to traditional performing/gravel pack systems to eliminate the effects of gun shock on the gravel pack apparatus.
The present invention involves running the perforating apparatus into the wellbore on the same pipe string as the gravel pack assembly and anchoring the perforating apparatus to the wellbore. The perforating apparatus is then decoupled from the gravel pack assembly and the gravel pack assembly is picked up above the perforating apparatus. This accomplishes two things. First, mechanical shock is eliminated because the guns are no longer in mechanical contact with the gravel pack assembly. Mechanical shock is further dampened because the perforating apparatus is anchored into the wellbore. Second, the effects of a pressure wave are eliminated due to the dampening effect of the fluid column that exists between the top of the perforating apparatus and the bottom of the gravel pack assembly which is pulled away from and set above the perforating apparatus. Upon detonation, the guns and anchor device of the perforating apparatus are released or unset from the casing and are allowed to free fall or be pushed to the bottom of the wellbore. With the guns released from the wellbore casing, the gravel pack assembly is repositioned across the perforated zone. Sand control and stimulation treatments are then conducted to complete the well.
According to one aspect of the invention, there is provided a method of perforating and gravel packing a wellbore casing, the method comprising: making-up to a pipe string, a gravel packer assembly and a perforating apparatus; running-in the pipe string until the perforating apparatus is at a depth of intended perforations; and setting the perforating apparatus in the wellbore casing at a depth of intended perforations; and disconnecting the perforating apparatus from the pipe string.
According to a further aspect of the invention, there is provided a system for perforating and gravel packing a wellbore casing in a single trip into the wellbore, the system comprising: a gravel packer assembly having a production screen and at least one packer; a perforating apparatus connected to the gravel packer assembly, wherein the perforating apparatus is detachable from the gravel packer assembly after the system is placed in the wellbore and before a detonation of the perforating apparatus; a tool having at least one casing engaging slip segment, wherein the tool is matable with the perforating apparatus, and wherein the tool is settable in the wellbore casing.
According to still another aspect of the invention, there is provided a system for perforating and gravel packing a wellbore casing in a single trip into the wellbore, the system comprising: a gravel packer assembly having a production screen and at least one packer, wherein the gravel packer assembly is connected to a pipe string for running the system into the wellbore; a perforating apparatus connected to the gravel packer assembly, wherein the perforating apparatus is detachable from the gravel packer assembly after the system is placed in the wellbore and before a detonatio
George Kevin R.
Smith Barry Ed
Traweek Marvin Bryce
Walker David Joseph
Wall Stanley
Baker & Botts L.L.P.
Osca, Inc.
Tsay Frank S.
LandOfFree
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