HK1140243B - Oil well completion tool having severable tubings string barrier disc - Google Patents

Description

Oil well completion tool with severable tubing string barrier disc

Cross Reference to Related Applications

This application is a continuation-in-part of U.S. patent application No.11/744,605 filed on 5, 4, 2007, the contents of which are incorporated herein by reference.

Background

Technical Field

The present invention relates to an oil well completion tool adapted for insertion within a multi-section tubing string within an oil well casing, typically above another oil well tool such as a packer. The completion tool allows for plugging of the tubing string, for example to allow setting of packers and the like, and thereafter allowing full opening for production from the well.

Background

Typically when an oil or gas well is drilled into a hydrocarbon containing formation, the borehole is isolated from the surrounding formation by a string of interconnected, relatively large diameter pipe sections, also commonly referred to as well casing. For example, the well casing portions may be about 5 to 9 inches in diameter. Cement is typically placed around the casing along its entire length to provide a barrier between the outside of the casing and the inside of the borehole in the well. Cement is used to prevent fluid and gas communication under pressure from one subterranean formation to a nearby formation.

A tubing string made of smaller diameter individual sections interconnected end-to-end is typically run into the well within the casing. During completion of a typical cased well, a tool such as a packer may be placed on the end of the tubing string to isolate a region known as the annulus between the inside of the casing and the outside of the tubing string. There are many types of well packers in use, and elastomeric sleeves or bladders engageable with the interface of the casing are expanded and "set" mechanically, hydraulically, or using wire sets. Mechanical packers are typically actuated by rotating the tubing string, which compresses the sleeve into sealing engagement with its outer surface against the casing.

Hydraulic packers offer many installation and operational advantages, particularly where the well casing has multiple bends and is therefore not substantially straight throughout its length, or where installation in a horizontal wellbore is required so that mechanical packers are impractical. In the case of hydraulic packers, a plug must be provided within the casing below the packer to provide resistance to the hydraulic pressure required for setting of the packer balloon. Once the packer is set, the plug must be fully opened to begin production. Hydraulic packers are just one example of a downhole tool that requires pressurized hydraulic fluid to operate.

In well stimulation operations, the formation is typically "surged" to remove debris from the formation and improve the flow of hydrocarbons. Surging is achieved by reducing the pressure inside the tubing string by an amount below the formation pressure and allowing the pressure differential to equalize very quickly. Another example of well stimulation includes increasing the fluid pressure within the tubing string to a value significantly above the formation pressure. When the pressure in the tubing string is released faster than the pressure in the formation, cracks form in the formation, which can produce hydrocarbons without the need to traverse the broken rock resulting from drilling and completion operations.

In these instances, as with the other example completions, it is advantageous to completely remove the plug from the well flowpath immediately after beginning to operate as a tool or to perform stimulation.

The prior art has many example tools to assist in the setting of packers and similar well annulus isolation devices. Many of these tools utilize plugs to temporarily plug the tubing string so that hydraulic pressure on a packer or the like can be applied to the tool. Some plugs are used on the wire and set in place. After the pressing operation, the wire is retracted to pull the plug to the surface. This type of operation has been found to be time consuming and has risks associated with well disturbances.

Other well casing isolation tools are provided with tubing string plugging devices such as glass or ceramic plugs. These plugs are opened by dropping a rod from the ground causing the plug to break, or by applying an overpressure to the plug causing it to break. Many unresolved problems and safety concerns arise from the use of these types of plugs because the materials are brittle and therefore prone to micro-cracking caused by improper operation on the well surface, improper assembly of tools, or tolerance issues that greatly reduce the rated pressure of the tool, which can lead to unpredictable plug failure.

In U.S. Pat. No.3,779,263, a pressure responsive frac valve particularly for surging an oil well employs a tubular cutting sleeve that is moved by a pressure responsive tubular piston. The main valve passage communicates directly with the piston chamber. Once the piston chamber is pressurized by fluid introduced into the valve passage, the piston-actuated cutting sleeve moves toward a rupture disc that normally blocks the passage through the valve. The rupture disc is deeply scored with a series of radially oriented score lines. When the multi-angled cutting edge of the cutting sleeve is mated to the rupture disc, it breaks up a series of individual petals that are bent outwardly toward the valve wall structure.

The valve of U.S. patent No.4,609,005 relies on a tubular cutting spindle for severing a portion of the disc normally blocking passage through the valve housing while leaving a narrow uncut portion by means of an elongated slit in the working edge of the cutting spindle. As shown in fig. 2 of the drawings of the' 005 patent, the mandrel in the fully actuated position cannot ensure that the desired offset diameter is maintained through the open valve, in part because of the gap between the mandrel and the adjacent valve housing wall.

U.S. patent No.4,658,902 describes a surge tool for a wellbore annulus in response to pressure. A tubular cutter mandrel carried within the tool housing and moved by a separate powered mandrel is operable to engage and cut a C-shaped section from a frangible disc that normally blocks passage through the tool. The cutter arbor has a longitudinally extending slot that leaves the flap portion of the disc uncut. The cut-out portions of the disc, as well as the flap portions, are said to be deflected laterally by the spindle and retained between the outer surface of the spindle and the inner surface of the housing. One or more pins must be sheared before the powered spindle can effect movement of the tool spindle toward the disc. Because the tool spindle is provided with an elongated slot therein, the spindle must be moved through a displacement that is significantly greater than the length of the slot in the spindle. To achieve this extended path of spindle movement, a two-stage spindle structure is required, along with a plurality of pins that control the release of the spindle, thus increasing the complexity of the mechanism and its attendant cost and compromising its overall reliability.

In PCT application PCT/GB97/02043, plugs for oil or gas well drilling are described as an alternative to conventional burst-type plugs which burst when the pressure is above a certain level in order to open the tubing string. Some of these early plugs can break free from the tubing string, thereby creating undesirable equipment downhole, which can present problems at a later date. The plug of the' 043 patent application is made of a threaded box end, a threaded pin end, an upper tubular body member, and a lower tubular body member. A steel barrier plate machined from the lower body member extends across the central bore of the tube. A cutter having a tapered cutting blade is secured to the lower body member by a shear pin. The knife is moved by a movable piston sleeve temporarily held in a retracted position within the lower body member by locking dogs and a slotted locking sleeve. By cycling the pressure in the tube, the piston sleeve moves up and down against the action of the spring until a sliding bolt enters a selected position in the slotted sleeve. This results in the release of the locking pawl, allowing the sleeve to move downwardly into engagement with the cutter, effecting shearing of the shear pin, and allowing the cutter to strike the stop plate. Because only a portion of the plate is severed, the cut portion thereof is deflected outwardly by the knife into a recess in the box end. The tool is very large and can only be used in large diameter casing. The functional reliability of this very complex and expensive mechanism has inherent problems in the difficult conditions present at extremely deep wells, rendering the unit unsuitable for most wells.

Tubing string isolation tools using frangible glass discs are described in U.S. patent No. re39,209. The presence of the glass disc allows well fluid from the surface to be introduced into the tubing string at elevated pressure to establish a hydrostatic load that allows the packer or any other auxiliary device to be set hydraulically in a conventional manner. When the packer or other auxiliary device has been set, and it is desired to resume production of fluid from the formation, the pressure of the well fluid in the tubing string is raised, thereby applying a pressurized fluid load to the piston which overcomes the shear pin resistance and moves downward to break the glass disc with sufficient force. The debris from the disk shattering can amount to glass pieces of one-quarter to one-half inch in diameter. Debris of this nature is to be avoided because of the various closed downhole tolerances. If a metal rod is intended to crush the glass disk, bends in the tubing string may actually interrupt the downward movement of the rod or impede the movement of the rod so that the rod does not have sufficient impact force to crush the glass disk.

In U.S. patent No.5,996,696, assigned to the present assignee, a rupture disc is employed to block the flow path through the tubing string to allow testing of the integrity of the tubing string connections. After it is determined that there is no leak in the tubing section, the disc can be burst by applying a predetermined overpressure to the disc through the tubing string. The tubing sections of all tubing strings have the desired offset diameter for a particular inside tubing diameter. While the tubing string integrity test device of the' 696 patent has been found to be satisfactory for many applications, in some instances it has been found that the central portion of the disk which ruptures under overpressure does not open completely, and cannot be folded over onto the device housing, thereby failing to provide the desired offset diameter through the test device.

Disclosure of Invention

The oil well completion tool of the present invention overcomes the problems with prior tools as described above. The tool includes a tubular assembly defining an elongate axially extending main passage with a severable plug mounted within the tubular assembly which normally blocks the axial passage. The movable shear cylinder unit within the tubular assembly has a plug-severing edge operable to sever an entire central portion of the plug from the remaining peripheral portion of the plug as the shear cylinder unit is moved through a plug-severing displacement. Separate elongate hinge structures within the assembly have inner elongate legs secured to the central portion of the plug facing the shear cylinder unit and an outer leg joined to an annular member connected to the peripheral portion of the plug. The elongate leg of the hinge structure operates by virtue of its connection to the annular member to retain the plug within the body of the assembly after severing of the central portion of the plug. The hinge structure allows the cut central portion to be displaced integrally independently of and in a direction away from the remaining peripheral annular portion of the plug. An L-shaped tab is provided on the periphery of the central portion of the plug opposite the hinge structure. The tab is received in a cutout in the plug severing edge of the shear cylinder unit, which tab maintains the leading edge portion of the shear cylinder unit in alignment with the central portion of the plug.

The severable plug is preferably mounted in a tubular assembly of the tool between the bottom sub and a housing connected to the top sub. A displaceable shear cylinder unit within the housing is displaceable through a plug severing displacement by a single acting piston structure forming part of the housing. The function of the tapered plug-severing edge of the shear cylinder unit is to progressively cut the entire central portion of the plug from the remaining peripheral portion of the plug. The elongated legs of the hinge structure retain the severed central portion of the plug within the main passage of the assembly as the hinge structure undergoes elongation, thereby allowing the central portion of the plug to be displaced independently of and in a direction away from the remaining peripheral portion of the plug. By providing a hinge having an elongate leg which is separate from but connected to the central portion of the plug and which undergoes elongation as the central portion of the plug is severed by the shear cylinder unit and then deflected laterally, the severed portion of the plug can be moved laterally and longitudinally of the main passage of the tool and thus into the recess in the wall structure of the tool. As a result, the cut-out portion of the plug does not block the main passage, thus ensuring that the desired offset diameter through the tool is maintained.

The wall structure of the tool tubular assembly and the movable shear cylinder unit cooperate to form a chamber, typically at atmospheric pressure, with a piston surface facing a plug that typically blocks the passage through the tubular assembly. When the fluid in the chamber is pressurized, thereby applying a force to the piston surface sufficient to displace the shear cylinder unit, the leading end of the conical plug-severing edge of the shear cylinder unit first contacts the central portion of the plug to begin severing the plug, which continues around the circumference of the plug until the entire central portion of the plug is separated from its peripheral portion. Preferably, the plug is provided with a cavity in one surface thereof which is aligned with the leading end of the shear cylinder unit which first contacts the surface of the plug. The depth of the central region of the cavity is greater than the depth of the cavity regions on each side thereof to facilitate initiation of severing of the central portion of the stopper by the shear cylinder unit.

Any of a variety of pressure or force actuatable devices may be provided to control the displacement of the shear cylinder unit through the plug severing displacement. The device may be a rupture disc or Kobe drop lever activated slam-down plug. The use of a rupture disc in communication with the piston chamber in the wall structure of the tool assembly or shear cylinder unit allows for actuation of the shear cylinder unit by atmospheric or differential pressure that can be controlled from the surface. The use of a rupture disc for this purpose is preferred because the pressure response can be selectively controlled by selecting a rupture disc of predetermined burst characteristics.

The tool of the present invention has utility in vertical well casings and in one or more horizontal casing sections leading from a vertical well extending to the surface. Particularly useful in multiple well applications because no debris is left in the hole after the plug is opened to enable production from the well, whether vertical or horizontal.

Another important feature of the present invention is that the compressive characteristics of the plugging plug can be selectively varied by varying the plug thickness, the material of construction and the overall shape of the plug. Without adversely affecting the ability of the stopper to fully open.

Most prior art completion tools operate under specific parameters and operating procedures that do not allow for tool changes and alternative configurations to account for changing well conditions and procedures.

The design of the present oil well completion tool is such that in most typical operations, the internal atmospheric chamber that receives the piston is pressure sealed against the annulus surrounding the piston and piston housing. Thus, the atmospheric chamber is not adversely affected at normal annulus pressures.

In the case of very high pressure well conditions, which must be accommodated, the pressure differential, i.e. the pressure differential between the annulus pressure and the pressure in the tubing string and thus in the tool, must be compensated for sufficiently in order to prevent damage to the tool housing or piston structure caused by overpressure when using the oil well completion tool of the present invention. This high pressure compensation must be provided while maintaining full control over the selective operation of the tool. In wells that encounter excessive pressure, the pressure differential between the well annulus pressure and atmospheric pressure may be of a magnitude sufficient to collapse the tool housing or piston shear cylinder wall in an inward direction toward the atmospheric pressure chamber. To prevent these potentially adverse and catastrophic events, a series of holes may be provided in the tool housing to reduce the pressure differential between the inside of the tool and the surrounding annulus to a mechanically acceptable level, or pressure compensating holes may be provided in the piston.

Because the amount of pressure required to effect operation of the tool is a controllable parameter, pressure may be applied from the surface down the pipe or casing string at a level sufficiently above the annulus or pipe pressure to effect the desired efficient operation of the tool.

Drawings

FIG. 1 is a fragmentary vertical cross-sectional view of a tubing string with an oil well completion tool assembly according to the present invention positioned below a schematically illustrated packer;

FIG. 2 is a vertical cross-sectional view of an embodiment of a completion tool assembly showing the shear cylinder unit in its normal position over a severable plug mounted within the tubular assembly in normally blocking relationship with the axial passage of the assembly;

FIG. 3 is a vertical cross-sectional view of the embodiment of FIG. 2 showing the position of the shear cylinder unit after it has been moved through its plug severing displacement;

FIG. 4 is a perspective view of a movable shear cylinder unit of the completion tool assembly;

FIG. 5 is an enlarged fragmentary vertical cross-sectional view showing the position of the shear cylinder unit prior to severing of the central portion of the severable plug mounted in the tool assembly;

FIG. 6 is an enlarged, fragmentary, vertical cross-sectional view similar to FIG. 5, but showing the shear cylinder unit in its actuated position after the shear cylinder unit has severed the central portion of the stopper;

fig. 7 is an enlarged vertical cross-sectional view of a portion of the component shown in fig. 6, as compared to 90 shown in fig. 6. (ii) a

FIG. 8 is an enlarged cross-sectional view through the tubular completion assembly along a horizontal plane showing the bottom of the severable plug;

FIG. 9 is an enlarged cross-sectional view taken along the same line as FIG. 8, without the severable plug and hinge attached thereto;

FIG. 10 is a top perspective view of the severable plug with a hinge structure attached to a central portion of the plug;

FIG. 11 is a bottom perspective view of the severable plug of FIG. 10;

FIG. 12 is an exploded bottom perspective view of the severable plug and the hinge member and its associated annular support member adapted to be attached to the plug body;

FIG. 13 is a vertical cross-sectional view of a second embodiment of a completion tool assembly;

FIG. 14 is a vertical cross-sectional view of a third embodiment of a completion tool assembly optionally having a plurality of bores disposed in the piston in communication with an atmospheric chamber that reciprocatingly receives a portion of the piston during movement of the piston;

FIG. 15 is a horizontal cross-sectional view taken substantially on line 15-15 of FIG. 14 and viewed in the direction indicated by the arrows;

FIG. 16 is a vertical cross-sectional view of a fourth embodiment of a completion tool assembly; and

FIG. 17 is a vertical cross-sectional view of a fifth embodiment of a completion tool assembly.

Detailed Description

An oil well completion tool 20 according to a preferred embodiment of the present invention is shown in FIG. 1, the oil well completion tool 20 being shown installed in a multi-section tubing string 22 below a schematically shown packer 24 located in an oil well casing 26. The tool 20 includes a tubular assembly 28 having a threaded upper box section 30 adapted to receive the threaded end of the pipe segment 22 a. The outer shell 32 of the assembly 28 is threadably connected to the top sub 30 and interposed between the sub 30 and the threaded lower pin sub 34. The pin section 34, which is threadably coupled to housing 32, is adapted to be threaded into a section 22b of tubing string 22. A shear cylinder unit 36 is displaceably mounted within the housing 32 for axial movement in a main passage 38 of the tool 20. A severable plug, generally designated 40, is mounted between the adjacent ends of the housing 32 and the lower segment 34. The plug 40 in the normal position blocks the main passage 38 of the tool 20. The plug 40 is preferably made of a metal such as inconel, stainless steel or equivalent metals. In the orientation of unit 36 shown in fig. 2, the lowermost tapered plug-severing edge 42 of shear cylinder unit 36 has a leading edge segment 42a and a plurality of opposed trailing edge segments 42b, with leading edge segment 42a being closest to the adjacent surface of plug 40 and trailing edge segments 42b each being at an angle of about 7 ° to 18 °, preferably about 11 ° to 16 °, and most preferably about 15 °, relative to the longitudinal axis of channel 38. The edge segments 42a and 42b cooperate to define a circular, tapered plug-severing edge. In this regard, edge 42 is also preferably beveled at an angle of about 15 from the outer diameter to the inner diameter of shear cylinder unit 36.

The plug 40 comprises an assembly having a solid circular body 44, the solid body 44 comprising a central planar surface portion 46 having an outer conical portion 48 merging with an annular peripheral step portion 50, the step portion 50 comprising an inner circular portion 50a and an outer circular portion 50 b. For example, it can be seen from FIG. 5 that the surface 52 of the plug 40 opposite the plug portion 46 is substantially flat except for a circumferentially extending rim portion 54 at the periphery of the plug.

The hinge structure, generally designated 56, in the assembly 28 includes an annular member 58 secured to the outermost stepped peripheral surface 50b of the plug 40. The elongated L-shaped member 60 of the hinge structure 56 includes an outermost generally U-shaped portion 62 and an outer leg portion 64. The U-shaped portion 62 includes legs 66 and 68, with leg 68 being joined to outer leg portion 64. The leg 66 of the portion 62 is integral with the annular member 58. Plug 40 and hinge structure 56 may be made from any of a number of metals conventionally used in the manufacture of rupture discs, with inconel being preferred, but 316 stainless steel may also be used, by way of example only.

Although the figures show a preferred embodiment of plug 40 having substantially flat opposing surfaces forming a central portion 46 of the plug, the severable plug may have a central portion that is raised to a concavo-convex shape with the concave surface facing either upstream or downstream of the pressure source, depending on the well pressure profile and the purpose to be achieved by well completion tool 20.

The lower section 34 has an internally threaded inner cavity portion 34a configured to receive the externally threaded end portion 32a of the housing 32. The lowermost end 32a of the housing 32 is provided with an outermost annular groove 70 which complementarily receives the rim portion 54 of the plug 40. The rim portion 54 serves to restrain bulging of the body 44 under fluid pressure acting thereon. It can also be seen from fig. 5 that the plug 40 is clamped between the lowermost end 32a of the housing 32 and the circumferentially extending inner channel portion 34b of the lower section 34. By properly tightening the threaded interconnection between housing 32 and segment 34, a metal-to-metal seal is formed between plug 40 and housing 32 and segment 34 that prevents leakage, thus eliminating the need to provide packing such as O-rings that may degrade over time. The cylindrical interior of the segment 34 has a cut-out portion 34d to receive the portion 62 of the hinge structure 56.

Shear cylinder unit 36 has an elongated tubular body portion 72 received in a circumferentially extending elongated recess 74 in a wall structure 76 of segment 30, and an elongated annular recess 78 in a wall structure 80 of housing 32. The recess 78 in the housing 32 is stepped and has a larger diameter than the recess 74. A circumferential piston projection 82 extending outwardly from the cylindrical wall 36a of shear cylinder unit 36 contacts the surface of recess 78 and cooperates with the surface to form axially spaced circumferentially extending chambers 84 and 86, respectively. Chamber 86 has a larger area than chamber 84. in the embodiment shown in fig. 2 and 3, chamber 86 is typically at about atmospheric pressure.

An L-shaped tab 88 mounted on the periphery of surface 52 of plug 40 engages the lowermost end of shear cylinder unit 36. The tab 88 has a leg 88a attached to the surface 52 of the plug 40 and an outwardly facing leg 88b, the leg 88b being received in a cutout 89 in the lowermost end 36b of the shear cylinder unit 36. As can be seen in fig. 11, leg 88b of tab 88 is transversely arcuate to complementarily fit ramp 36c of cutout 89. The leg portion 88b of the tab 88 has a width equal to the width of the cross-section of the cutout 89, whereby the side edges of the leg portion 88b engage the opposite sides of the cutout 89. The wall portion 36c of the lowermost end 36b of shear cylinder unit 36 is reduced in thickness and aligned with tab 88 to receive the outer end extension 88b, as shown in fig. 2, 3 and 5.

During assembly of the oil well completion tool 20, when the shear cylinder unit 36 is inserted into the housing 32, the leg portion 88b of the tab 88 is trapped between the outer surface of the reduced thickness cutaway wall portion 36c of the lower end 36b of the shear cylinder unit 36 and the innermost surface of the housing 32. The leg 88b of the tab 88 has a cross-sectional curvature that generally conforms to the configuration of the transversely tapered surface 36c of the outermost end 36b of the shear cylinder unit 36. During insertion of the shear cylinder unit 36 into the tubular assembly 28, the engagement of the side edges of the legs 88b of the tabs 88 with the opposing edges 89a of the cutouts 89 prevents rotation of the shear cylinder unit 36 within the channel 38 caused by the torque applied to the piston as the upper case segment 30 is screwed into place. Thus, leading edge segment 42a of shear cylinder unit 36 remains in accurate alignment with portion 40a of plug 40, not only during installation of shear cylinder unit 36 but also during operational shifting.

When the oil well completion tool 20 is subjected to high downhole pressures, which may be as high as 10,000psi or higher, the central portion 46 of the plug 40 will bend to some extent in a direction toward the pressure exerted on the plug 40. The opposite side edges of leg 88b of tab 88 remain engaged with the opposite side 89a of cutout 89 even if the central portion 46 deflects to some extent under the high pressure fluid in the well. Thus, there is no tendency for shear cylinder unit 36 to rotate within housing 32, which could cause edge segment 42a of edge 42 to move out of its predetermined, accurately aligned position relative to portion 46 of plug 40.

An upper piston shoulder 90 of the protrusion 82 faces the chamber 84, while a lower piston shoulder 92 of the protrusion 82 faces the chamber 86. A pair of tubular fittings 94 threaded into opposing sidewalls 36a of shear cylinder unit 36 and aligned with chamber 84 each carry a rupturable member 96, preferably comprising a bulged pressure-activated rupture disc, which communicate with passage 38 of tubular assembly 28. Once the fluid pressure within passage 38 of tubular assembly 28 is great enough to rupture disc 96, the fluid pressure within chamber 84 acting on piston shoulder 90 causes shear cylinder unit 36 to move toward plug 40. Because chamber 86 is at atmospheric pressure, chamber 86 does not provide any significant resistance to the pressure applied to shoulder 90 once rupture disc 96 is ruptured.

Rupture disc 96 is preferably provided in increments of 200psi each over a wide range of pressure applications so that an appropriate rupture disc may be selected depending on well conditions and operation. Generally, the rupture disc is selected to require application of fluid pressure on the order of at least about 3500psi in order to effect rupture of the rupture disc 96, although disc rupture values of up to 10,000psi may be employed depending upon the operating parameters of the particular well. In addition, the diameter of the bore of fitting 94 to be opened after rupture of disc 96 may vary depending on the desired speed of shear cylinder unit 36 toward plug 40. In the event that very high pressure differentials must be accommodated between the internal passage 38 of the tubular assembly 28 and the surrounding annulus, the bore diameter through fitting 94 may be selected to ensure that the flow of pressurized fluid into chamber 84 is controlled to prevent shear cylinder unit 36 from moving toward plug 40 at excessively high rates of movement.

The leading edge segment 42a of edge 42 of shear cylinder unit 36 moves into contact with surface 52 of plug body 44 to begin progressively severing central portion 46 of plug 40 from peripheral portion 50 of plug 40 (represented by dashed line 46a in fig. 8). As can be seen in fig. 2, 5 and 10, surface 52 of stopper 40 is provided with an elongated lumen 98 in peripheral portion 50 of stopper 40 opposite hinge structure 56. The longitudinally curvilinear cavity 98 is strategically located inboard of the rim 54 in the region of the plug 40 initially contacted by the leading edge segment 42a of shear cylinder unit 36. The lumen 98 has a central region 100 that has a depth greater than the depths of regions 102 and 104 on opposite sides thereof. The member 58 is preferably provided with at least three integral projections 58a, b and c extending outwardly from the outermost circumferential edge of the member 58. The spacing between the projections 58a and 58b is smaller than the spacing of the projections 58b to 58 c. Thus, the projections 58a-c are complementarily received within the recesses 58d of the respective sub 34 (FIG. 9), ensuring that the plug 40 is positioned in an orientation relative to the sub 34 such that the leading edge segment 42a of the shear cylinder unit 36 is directly aligned with the central region 100 of the cavity 98 within the plug 40. Projections 58a, b and c are of sufficient size, shape and number to prevent plug 40 from rotating out of its predetermined timed orientation relative to leading edge segment 42a of shear cylinder unit 36 when housing 32 is installed in sub 34.

The internal cavity 98 in the plug 40 ensures that the deforming force initially applied by the leading edge segment 42a to the surface 52 of the plug 40 is concentrated on the area of the plug 40 that is relatively narrow in cross-section and less thick than the remainder of the peripheral portion 50 during displacement of the shear cylinder unit 36 by fluid pressure applied to the shoulder 90 of the piston nose 82 for a displacement to effect severing of the entire central portion 46 of the plug 40. Leading edge segment 42a of edge 42 of shear cylinder unit 36 first contacts plug 40 in the central region of internal cavity 98. Thus, the available force applied to plug 40 by shear cylinder unit 36 is concentrated directly on one area of plug 40, which ensures that shearing of plug 40 is initiated.

Once the tapered edge 42 of shear cylinder unit 36 has completely severed central portion 46 from peripheral portion 50 of plug 40, continued downward movement of the cylindrical outermost end 36b of shear cylinder unit 36 causes severed central portion 46 to flex outwardly toward its position shown in FIGS. 6 and 7. The sidewall of the segment 34 has an internal cavity 108 positioned to receive the deflected central portion 46 of the stopper 40 and components of the hinge structure 56.

As best seen in fig. 3, 6 and 7, when central segment 46 is severed from peripheral portion 50 of plug 40 by shear cylinder unit 36, U-shaped portion 62 of hinge structure 56 experiences elongation, thereby allowing severed central portion 46 to not only flex laterally, but also shift bodily independently of peripheral portion 50 of plug 40 and in a direction away from peripheral portion 50. Cutout 89 in lowermost end 36b of shear cylinder unit 36 clears portion 62 of hinge structure 56 as shear cylinder unit 36 severs and then flexes central portion 46 of plug 40. Full deflection and axial displacement of the central portion 46 of the plug 40 by the shear cylinder unit 36 ensures that the severed central portion 46 of the plug 40 is moved fully into the lumen 108, thereby preventing the central portion 46 from interfering with the offset diameter of the tubular assembly 28. When the leg portion 88b is laterally displaced between the reduced wall thickness portion 36c of the shear cylinder unit 36 and the innermost surface of the housing 32, the leg portion 88b of the tab 88 straightens out to be generally parallel to the leg portion 88 a. Continued engagement of the side edges of leg 88a with the corresponding opposing surfaces of cavity 89 prevents rotation of shear cylinder unit 36 as shear cylinder unit 36 moves through a displacement to effect severing of central portion 46 of plug 40 by the leading edge of shear cylinder unit 36.

The cavity 98 within the plug 40 acts to amplify the shearing action of the plug 40 at the point of maximum mechanical loading without adversely affecting the overall plug pressure rating. The overall extent of displacement of the cut-out portion 46 of the plug 40 in the axial direction of the passage 38 of the tubular assembly 28 can be varied as desired by increasing or decreasing the length of the legs 66 and 68 of the U-shaped portion 62 of the hinge structure 56.

The lower portion 112 of the end portion 106 of the shear cylinder unit 36 is machined to a smaller diameter than the upper portion of the unit 36 to provide clearance for the end portion 106 as the shear cylinder unit 36 moves through its plug-severing displacement. The longitudinally extending cut-out surface portion 36c of end 106 on the same side as cutout 89 also provides play to surface 52 of the severed central portion 46 of stopper 40 as stopper 40 flexes into internal cavity 108.

The oil well completion tool 120 of fig. 13 differs from the tool 20 in that a fitting 194 provided with a rupturable component such as a rupture disc 196 is mounted within the sidewall structure 180 of the tubular assembly 128. Further, as shown in fig. 13, the shear cylinder unit 136 may be constituted by an assembly including a piston 122 and a shear cylinder 124. In this example, the tubing string connected to the main passage 138 by the tubular assembly 128 should be understood to be at substantially atmospheric pressure, as would the extreme chamber 186 receiving the piston 122. Fluid pressure is applied downwardly to the annulus between the well casing, such as casing 26 of fig. 1, and the outer surface of tubular assembly 128 to create a pressure differential between the annulus and the interior passage of tubular assembly 128 sufficient to effect rupture of disc 196, thereby causing the pressure introduced into piston chamber 184 acting on piston shoulder 190 of piston extension 182 to move shear cylinder unit 136 through its plug-severing displacement in the same manner as tubular assembly 28 operates.

The oil well completion tool 220 of fig. 14 is structurally similar to the tool 120, except that in this example it is understood that the tubing string of the tubular assembly 228 connected thereto and the main passage 238 are at a predetermined fluid pressure, which may be the gravitational force of the liquid within the tubing string. To actuate shear cylinder unit 236, fluid pressure is applied to the annulus surrounding tubular assembly 228 sufficient to rupture disc 296 of fitting 294 in sidewall structure 288 of tubular assembly 228. Upon rupture of the rupture disc 296, fluid pressure exerted on the shoulder 290 of the piston protrusion 282 causes the shear cylinder unit 236 to move through its plug severing displacement, as described with respect to tools 20 and 120.

The oil well completion tool 220, for example, is optionally provided with six 0.25 inch diameter bores 298 in the shear cylinder unit 236 spaced 60 ° apart around the piston circumference. The purpose of the bore 298 is to provide compensation for well pressures above normal annulus pressures without damaging forces being exerted on the tool housing 232, particularly the sidewall structure 288 or piston 236 surrounding and forming part of the atmospheric chamber 286. To actuate the tool 220, the annulus pressure in the casing surrounding the tool 220 is increased to a value greater than the pressure within the tubing string and within the main passage 238 of the tubular assembly 228, thereby causing the rupture disc 296 to rupture and displace the piston 236 toward and into a severing relationship with the plug 240.

The oil well completion tool 320 in fig. 16 is the same as the tool 120, except that the coriolis drop rod activation plug 330 replaces the rupture disc member 94 of the tool 20. Thus, as the conventional drop rod is dropped through the tubing string connected to the upper section 376 of the tubular assembly 328, the tubular extension 332 of the Kobe plug is broken, thereby allowing pressurized fluid within the main passage 338 of the tubular assembly 328 to be introduced into the chamber 384. As described above for tools 20, 120 and 220, pressurized fluid introduced into chamber 384 acting on piston shoulder 390 of piston extension 382 of shear cylinder unit 336 displaces the assembly through a plug severing displacement regulated by atmospheric chamber 341.

The oil well completion tool 320 in fig. 17 is the same as tool 20 except that a series of holes 426 are provided in a sidewall structure 480 of housing 432. Also, preferably, six 0.25 inch diameter holes 426 are provided around the circumference of the sidewall structure 480, spaced 60 apart. In this example, chamber 486 is not at atmospheric pressure and its pressure is equal to the fluid pressure in the annulus between tubular assembly 428 and the surrounding well casing. Thus, by increasing the fluid pressure within main passage 438 of tubular assembly 428 as compared to the fluid pressure within the annulus surrounding tubular assembly 428 and within chamber 486 to a level where the pressure differential is sufficient to effect rupture of disc 496, fluid introduced into chamber 486 acting on piston shoulder 490 of piston extension 482 may cause shear cylinder unit 436 to displace through a displacement to effect severing of plug 440. Because the fluid pressure in the chamber 486 remains equal to the pressure in the annulus surrounding the tubular assembly 428 by virtue of the provision of the apertures 426, displacing the shear cylinder unit 436 under the increased pressure in the main passage 438 causes the fluid in the chamber 486 to be expelled through the apertures 426 into the annular region surrounding the tubular assembly 428.

The design of the oil well completion tool 420 having a series of openings 426 in the side wall of the housing 432 is particularly suitable for changing well conditions, such as very high pressures, as may occur in very deep oil wells. In these high pressure well conditions, it may be desirable to use differential pressure to operate well completion tool 420. In this example, the pressure differential is defined as the difference between the pressure in the annulus and the pressure in the tubing string 22. The occurrence of differential pressure is a problem with well design or well geometry or may be created by applying pressure to the tubing string or annulus from the surface.

In wells with excessive pressure, the pressure differential between the well pressure and the atmospheric chamber 486 can cause the housing 432 to collapse or rupture the piston wall 436 toward the atmospheric chamber 486. Because it has been determined what pressure is needed to operate oil well completion tool 420, pressure may be applied from the surface down tubing string 22 at a magnitude greater than the annulus pressure to enable tool 420 to perform the appropriate operations.

Claims (25)

1. An oil well completion tool adapted to be connected to a multi-section tubing string within an oil well casing, the tool comprising:

a tubular assembly having a wall structure forming an elongate axially extending main channel,

said assembly having opposite ends, at least one of said ends being adapted to be connected to a section of said tubing string;

a severable plug mounted within the tubular assembly, the plug normally blocking the axial passage;

a movable shear cylinder unit within the passage of the assembly, the shear cylinder unit being provided with a plug-severing edge normally spaced from a peripheral portion of the plug,

said shear cylinder unit being movable through a plug severing displacement wherein said edge of said shear cylinder unit severs the entire central portion of said plug from the remaining peripheral portion of said plug; and

a separate elongate hinge structure within the assembly, the hinge structure being connected to the central portion of the plug,

the hinge structure is operable to retain the severed central portion of the plug within the main passage of the assembly while allowing the central portion of the plug to be displaced entirely independently of and in a direction away from the peripheral portion of the plug.

2. An oil well completion tool as set forth in claim 1, wherein said hinge structure is configured to allow said central portion of said plug to elongate after severing from said peripheral portion of said plug.

3. An oil well completion tool as set forth in claim 1, wherein said hinge structure is connected to said peripheral portion of said plug.

4. An oil well completion tool as set forth in claim 1, wherein said wall structure is provided with a recess receiving said cut central portion of said plug, thereby preventing said cut central portion of said plug from interfering with said main passage through said assembly.

5. An oil well completion tool as set forth in claim 1 wherein said shear cylinder unit includes a tubular piston and a cylindrical plug shearing device, said piston being mounted within said passage of said assembly and being deployed to engage and effect displacement of said shear cylinder unit shearing device toward said plug.

6. An oil well completion tool as set forth in claim 1, wherein said peripheral portion of said plug is provided with a rim, and said wall structure of said assembly has a circumferentially extending shoulder engageable with said rim of said plug.

7. An oil well completion tool as set forth in claim 1, wherein the circular portion of said central portion of said plug has a thickness greater than the thickness of the annular peripheral portion of said plug.

8. An oil well completion tool as set forth in claim 1 wherein said wall structure and said shear cylinder unit cooperate to form a chamber with a piston shoulder facing a plug severing edge of said shear cylinder unit, and actuatable means permit actuating fluid to be introduced into said chamber against said piston shoulder to displace said shear cylinder unit through said central portion severing displacement thereof.

9. An oil well completion tool as set forth in claim 5 wherein a rupturable member is provided within said wall structure of said assembly, said rupturable member being operable to permit application of fluid pressure to said piston to displace the piston to move the shear device of said shear cylinder unit through said central portion severing displacement upon rupture of said member.

10. An oil well completion tool as set forth in claim 6, wherein said central portion of said plug is provided with a cavity adjacent said peripheral portion of said plug to initiate severing of said central portion of said plug by said edge of said shear cylinder unit.

11. An oil well completion tool as set forth in claim 10, wherein said internal cavity is disposed opposite a region of said hinge structure connected to said assembly.

12. An oil well completion tool as set forth in claim 11, wherein said internal cavity comprises a region of greater depth than the remainder of said internal cavity.

13. An oil well completion tool as set forth in claim 12 wherein said internal cavity includes shallower depth sections on opposite sides of said zone.

14. An oil well completion tool as set forth in claim 10, wherein said inner chamber is an elongated structure having a region of greater depth than the remainder of said inner chamber, said region being located intermediate each end of said inner chamber.

15. An oil well completion tool as set forth in claim 10, wherein said internal cavity is located on an opposite side of said central portion of said plug from said hinge structure.

16. An oil well completion tool as set forth in claim 10 wherein said internal cavity is located inboard of and adjacent to said rim.

17. An oil well completion tool as set forth in claim 1 wherein said plug-severing edge of said shear cylinder unit is tapered and includes a leading edge segment and trailing edge segments, each of said trailing edge segments extending in opposite directions at an angle away from said leading edge segment.

18. An oil well completion tool as set forth in claim 17 wherein said trailing edge segments each extend at an angle of from 7 ° to 18 ° relative to the longitudinal axis of said passage.

19. An oil well completion tool as set forth in claim 17 wherein said central portion of said plug is provided with an internal cavity adjacent said peripheral portion of said plug, said leading edge segment of said shear cylinder unit being generally aligned with said internal cavity so as to initiate severing of said central portion of said plug at said internal cavity by said leading edge segment.

20. An oil well completion tool as set forth in claim 17, wherein said leading edge section and trailing edge section are beveled.

21. An oil well completion tool as in claim 19, wherein said leading edge section and trailing edge section are chamfered at an angle of 15 °.

22. An oil well completion tool as set forth in claim 1, wherein said hinge structure comprises an annular member attached to said peripheral portion of said plug and an elongated generally L-shaped member having a generally U-shaped leg portion formed of interconnected legs, one of said legs being joined to said annular member and the other of said legs being connected to said outer leg portion, said outer leg portion being attached to said central portion of said plug.

23. An oil well completion tool as set forth in claim 22, wherein said U-shaped leg portion of said hinge structure is configured to at least partially straighten out after said central portion of said plug is severed from said peripheral portion thereof, thereby allowing said central portion to move bodily independently of and in a direction away from said peripheral portion of said plug.

24. An oil well completion tool as set forth in claim 8, wherein said actuatable device comprises an actuator extending into said main passage, said actuator being adapted to be engaged by a drop rod to actuate said actuatable device.

25. An oil well completion tool adapted to be connected to a multi-section tubing string within an oil well casing, the tool comprising:

a tubular assembly having a wall structure forming an elongate axially extending main passage,

said assembly having opposite ends, at least one of said ends being adapted to be connected to a section of said tubing string;

a severable plug mounted within the tubular assembly, the plug normally blocking the axial passage;

a movable shear cylinder unit within the passageway of the tubular assembly, the shear cylinder unit being provided with a plug-severing edge normally spaced from a peripheral portion of the plug,

said plug severing edge of said shear cylinder unit being tapered and having a leading edge segment and trailing edge segments, each extending at an angle away from said leading edge segment in opposite directions;

a central portion of the plug is provided with a lumen adjacent the peripheral portion of the plug, the lumen being substantially aligned with the leading edge segment of the shear cylinder unit,

the shear cylinder unit is movable through a plug severing displacement wherein the leading edge segment initiates severing of the central portion of the plug and the leading edge segment and the trailing edge segment of the shear cylinder unit cooperate to cut the entire central portion of the plug from the remaining peripheral portion of the plug.