US3012609A

US3012609A - Device for perforating well casing

Info

Publication number: US3012609A
Application number: US854504A
Authority: US
Inventors: Lester W Toelke
Original assignee: SGL Carbon Corp
Current assignee: SGL Carbon Corp
Priority date: 1959-11-20
Filing date: 1959-11-20
Publication date: 1961-12-12
Anticipated expiration: 1978-12-12

Description

l.. w. TOELKE 3,012,609

DEVICE EOE PERFORMING WELL cAsING Filed Nov. 2o, 1959 Dec- 12, 1961 -5 Sheets-sheetI 1 Dec. 12, 1961 .w.1'oE| KE DEVICE FOR PERFORMING WELL cAsING Filed NOV. 20, 1959 www w L. W. TOELKE DEVICE FOR PERFORATING WELL CASING Dec. 12, 1961 3 Sheets-Sheet 3 Filed NOV. 20, 1959 n MZ FIEE

iinited tates @arent 3,012,609 DEVICE FOR PERFRATING WELL CASHQG Lester W. Toelke, Houston, rIex., assigner to Great Lakes Carbon Corporation, New York, NX., a corporation of Deiaware Filed Nov. 20, 1959, Ser. No. 854,594 13 Claims. (Cl. 16o-55.4)

This invention pertains to devices for perforating casing. More particularly, this device pertains to guns employing projectiles for the perforation of casing placed in water, oil and gas wells.

ln the drilling of petroleum and gas wells it is common practice to provide a steel casing to line the earth bore and prevent intrusion of solid and liquid matter into the well. It is also common practice to place cement around the casing in order to prevent its movement. The casing and cement are perforated by projectiles, and in more recent practice by means of shaped charges, in order to provide avenues of entry for the petroleum into the well in order that it may be flowed or pumped to the surface.

One of the most common types of guns for perforating casing is the so-called bullet gun. This usually consists of a gun 4body of elongate form and of such diameter that it may be lowered into the Well casing. The gun ybody will have a plurality of gun barrels threadably secured in chambers, each gun barrel communicating with a propellant chamber. Various means have been employed to tire the propellant in these chambers, either substantially simultaneously, sequentially or selectively. Since it is desired to obtain a uniform pattern of holes in the casing, the surrounding cement and ground formation, the gun barrels are positioned at regular intervals and angles in the gun body. Because sequential tiring of the individual projectiles lwill impart recoil shock and movement to the gun body it is diicult to predict or provide a uniform pattern of perforations in the casing. This disadvantage is, for all practical purposes, eliminated when all of the gun barrels are fired simultaneously. In order to achieve,

this, a mechanism in common usage provides a bore or firing channel running longitudinally of the gun body and transversely of the individual gun barrels. This channel connects with a chamber which contains an explosive primer. Upon detonation of this primer high pressure gases or flame will pass through the ignition channel and into laterally disposed individual ignition channels communicating with each gun barrel. This results in setting oif the propellant positioned behindA each gun barrel and drives the projectile out of the barrel through the casing. Typical devices of the foregoing type are described in U. S. Patents Nos. 2,436,118; 2,551,031; 2,446,235 and others.

In guns of the type described above the lateral ignition channels must be drilled in the gun body and become a permanent and integral part thereof. In many forms of these devices, there is 4also provided a channel or groove in the gun barrel itself which forms or serves as a conduit between the lateral ignition channel in the gun body and the propellant chamber.` After prolonged usage, these ignition channels become eroded and/or enlarged and reduce the eifective energy of the propellant because pressure will be lost through these channels proportionate to their diameter. Also, progressive enlargement of the lateral ignition channels in the gun body will necessitate either discarding the gun or remachining the channels and inserting sleeves whose inside diameter approximates that of the diameter of the original channel. It is, therefore desirable to minimize the erosion and enlargement of the ignition channels in the gun body itself and in the gun barrels containing such channels, or to eliminate the necessity for ignition chan-- nels in the gun barrel. Such improvements will result in machining economy, reduced gun barrel replacement, ,and'would also result in more eilicient use of the pressure generated from the propellant.

. It is an object kof this invention to provide an improved perforating gun whereby projectile penetration is considerably improved due to the more etlicient utilization of the force generated by the explosion of the projectile propellant.

It is a further object of this invention to provide an Y any damage to the ignition and firing channels caused by the resulting increased pressures from the tired propellant.

yIt is a further object of this invention to provide a perforating bulletgun in which'the propellant positioned in chambers behind each gun barrel is ignited by hot pressurized gases from a tiring channel and communicating with the propellant chamber by means of a unique, relatively inexpensive device which is replaceable after each tiring, which retains the maximum amount of pressure in the propellant chamber by minimizing gas losses due to back pressure into the ignition and tiring channels, .and which further minimizes the burning of the interior walls and threadsV of the' gun barrel chamber and the threads.

of the gun barrel which is secured in the chamber. j

Additional objects and advantages of the present inventionwill appear in the following description in which certain preferred embodiments of the invention are exempliiied, but which embodiments are intended for illustrative purposes only and not to limit the scope of the inven` tion, the latter being set forth in the appended claims. f

Briefly stated, the invention comprises an improved device for transmitting hot pressurized gases to a propellant chamber for'the purpose of igniting the propellant and imparting maximum velocity to a projectile fired from a gun barrel which communicates with the propellant chamber. The aforesaid device consists essentially of a ilat, solid imperforate Shear disc usually fabricated from steel, and having an external perpiheral depression, pref-k erably in the form of a groove. The disc is further provided With a duct or port which communicates the peripheral depression with a propellant chamber which, in turn, is positioned behind and communicates with a gun barrel. It is essential that the diameter of the disc he greater than the diameter of the propellant chamber in order that a substantially explosive gas-tight seal is formed when the disc is positioned against the shoulder of the propellant,v

when the propellant is ignited. In addition, this flange is useful in preventing a backward movement of the disc in operation of the perforating gun when the propellant is ignited. The flange is also referred to as a pressure'seal skirt integral with the disc. yIn t-he event that a liange or pressure seal skirt integral with the disc is employed, this ange extends into the propellant chamber and frlctionally bears against or engages the wall thereof to further 1mprove the sealing of the propellant gases. The duct or choke hole which is drilled into the disc and which forms a communication between the propellant channel and the peripheral groove of the disc minimizes the loss of propellant pressure and when the disc is ruptured by pressure, provides maximum force to drive the projectile through the casing and exterior earth formation.

Upon rupture of the shear disc the central portion of the disc, having a diameter approximating that of the bore of the gun barrel will be projected into and through the barrel thereby providing a gas-tight seal behind the projectile and added impetus to the projectile.

In another embodiment of the invention the shear disc of the present invention may comprise more than one element and consist of a shear disc base, an imperforate shear disc itting therein and optionally also a seal wafer, all of which will be readily apparent upon consideration of the attached drawings.

Referring Ito the drawings, FIGURE 1 is an elevation, partly in section of a perforating bullet gun embodying the invention.

FIGURE 2 is a sectional view taken along the line 2 2 of FIGURE l.

FIGURE 3 is a detailed plan view of the shear disc, partly in section.

FIGURE 4 is a view similar to FIGURE 2 showing the condition of the shear disc and the position of the projectile immediately after tiring the propellant.

FIGURE 5 is a view similar to FIGURE 2 showing the position of projectile and the central portion of shear disc at a longer interval after tiring than is shown in FIG URE 4.

FIGURE 6 is a sectional view similar to FIGURE 2 but using a shear disc comprising more than one element.

FIGURE 7 is an exploded view of the two main elements of the modiied shear disc of FIGURE 6.

FIGURE 8 is a cross-sectional view of a seal wafer, before and after pressure thereon, which may be employed with the modified shear disc of FIGURE 6.

In FIGURE 1 the perforating bullet gun device is shown generally at Iii, and consists of a gun body 11 of vertically elongate form and having a diameter which is appropriate to the diameter of the casing into which the gun will be lowered. The most commonly us-ed gun will have a diameter of approximately 4".

The gun in FIGURE l is shown positioned in a casing 46 which is in place in an earth bore 39. The gun body 10 has a plurality of gun barrels 26 which are threadably secured in threaded chambers 26a, these chambers being counterbored in the gun thereby leaving an eX- terior shoulder 25 which forms a surface recess in the gun body. This recess is useful in providing room for a torque wrench or other device employed in securing the threaded gun barrels into the threaded chambers. In some cases a rubber or other plastic seal (not shown) may be fitted over the outside end of the gun barrel and occupy the shoulder space 2S. The gun body 1@ has chambers 27 which hold propellant charges 28. The propellant chambers 27 are positioned behind the gun barrel charnbers 26a and will have diameters smaller than the diameter of the gun barrel chambers so that annular shoulders 26b are formed at the inner ends of barrel chambers 26a. Projectiles 38, normally in the form. of solid steel bullets, are disposed in Athe inner ends of the bore 36 of gun barrel 26. In FIGURE l three gun barrels and chambers are shown but it will -be understood that either one or a larger number of these barrels may be employed in the gun body.

Positioned between the end face of the projectile 38 and the propellant chamber 27 is a replaceable pressure shear disc 29 having an external peripheral depression Sil, preferably in the form of a generally V shaped groove. Opposite the peripheral depression 3i?, when the shear disc 29 is in place in the gun barrel chamber 26a, there is provided as an integral part of the gun body a lateral ignition channel 23 which conducts hot pressureized ignition gases or flame produced by igniting a primer, normally positioned in the upper part of the gun. Each of the ignition channels 23 communicates with a primary firing channel 13 which is a longitudinal -hole drilled in the gun body so as to intersect the individual ignition channels 23 at each gun barrel chamber 26a. The end of the tiring channel 13 is sealed by means of a plug 14 positioned in threaded passage 12. In the upper portion of the gun body 10 and communicating with Ithe tiring channel 13 is a lateral passage 15 leading from a primer chamber `17 which is drilled laterally into the gun body and, after positioning of the primer in primer chamber 17, said chamber is sealed to exclude well iluids by means of a plug 16. There is further provided a longitudinally drilled passage or duct 20 positioned in choke screw 19 which communicates the primer chamber 17 with a cartridge 21. The cartridge 21 is contained in a sub-assembly 18 which is threadably secured into the top end of the gun body 10, the sub-assembly containing conventional means for electrically tiring the cartridge 21, for example as is illustrated and described in US. Patents Nos. 2,433,231 and 2,636,56l. Y i

In FIGURE 2 more detail of the gun barrel propellant chamber, .tiring and ignition channels, and the replaceable pressure shear disc which is the essential feature of this invention, are shown. This figure further illustrates how provision is made for drilling ignition channel 23 into the gun body, this being done by forming a relatively large diametered surface hole through the gun body which hole or opening provides anaccess channel `for a drill so that passage 23 can be drilled in Ithe gun body. After passage 23 is drilled, the resulting surface hole is sealed with a plug or seal screw 24. Exclusion of well fluids at this point is ensured by positioning a metal seal 42 at the bottom of the drilled hole, and positioning a plastic seal 43, for example of neoprene, between the seal 42 Iand the seal screw 2d. In FIGURE 2 there is shown the peripheral depression or groove 35i in the pressure shear disc 29 which is shown in its preferred embodiment as including a flange or pressure seal skirt 32. This view also shows a detail of the ignition duct or choke hole 3.1 which connects the peripheral depression 30 of the shear disc with the propellant chamber 27. FIGURE 2 further illustrates the employment of a plastic seal 34 which excludes well fluids and which is positioned on the inside face of the gun barrel 26 and which seals against the face of the shear disc 29 or which seals against a ilash seal washer 33 described hereinafter.

In the views shown in FIGURES 2, 4 and 5, there is also illustrated one preferred embodiment of the invention which includes a flash seal washer 33 positioned between the shear disc 29 and the inside face of the gun barrel 26. This washer has an aperture whose diameter is larger than the diameter of the bore 36 of gun barrel 26 and an outside diameter equal to or slightly greater than the diameter of shear disc 29. This flash seal washer is used to restrain the shear disc 29 at its outer edges and to prevent the disc from upsetting in-to the groove for the barrel seal 34. The seal washer also prevents hot gases from propellant chamber 27 and `from ignition channel 23 from searing the threads of gun barrel 26 and gun barrel chamber 26a which progressively burns out the threads. The bore 36 of the gun barrel 26 is sealed to exclude well fluids by employing a rubber seal 37 which fits over the point of the projectile 38 and engages the walls of the bore 36. The projectile seal 37 is also useful as a means for holding the projectile 38 in proper position in gun barrel 26.

In FIGURE 3 there is shown a detailed plan view of the pressure shear disc 29 which is the essential and important feature of the present invention. This view also shows Ithe peripheral depression or groove 30, the ignition duct or choke hole channel 31 and also shows a preferred, although not absolutely essential feature of the invention, namely the flange or pressure seal skirt 32 which is an integral part ofthe shear disc.

In FIGURES 4 and 5 there are shown views of the projectile 38 and shear disc 29 immediately after and shortly after tiring of the propellant 2S. When the propellant is ignited by means of hot pressurized gases or flame conducted by means of the peripheral depression in the shear disc, the resulting pressurized gases shear the disc 29 causing the central por-tion of the disc,y having a diameter approximating that of the bore 36 of gun barrel 26 to be projected into and through the bore thereby 4forcing the projectile 38 out of the bore and through the casing shown in a perforated condition at 441. FIGURE 4 shows the pressure shear disc 29 being distorted in its central p0rtion due to the pressure of gases generated by the pro pellant; FIGURE 5 shows the ruptured pressure disc with the sheared off portion 29 traversing the bore 36 of gun barrel 26. yIn these figures, a preferred, but not absolutely essential embodiment of the invention is shown as including the use of a flash seal washer 33 positioned between the end face of gun barrel 26 and the shear disc 29. This washer has an aperture 35 having a diameter greater than Ithe bore 36 of gun barrel 26 and an overall diameter approximately equal to that of the shear disc 29. Under some circumstances it is preferable that the outside diameter of the seal washer 33 be slightly greater than the diameter of the shear disc 29. When the flash seal washer 33 is used, the shear disc 29 shears on the hole 35 and is forced into the smaller diameter of the gun barrel thereby forming a cup-shaped sealing arrangement. This increases the velocity of the projectile 38.

Again referring to FIGURE l t-he operation of the device is as fo-llows: A primer chamber 17 at the top end of the gun houses a primer charge, generally of the low explosive type such asfbulls eye powder in pelletized form. The threaded top end ofthe gun body receives a sub-assembly 1S which houses an electrically fired cartridge 21. An electric conductor cable positioned in lowering cable 22 is energized and the cartridge 21 is fired. The hot pressurized gases travel through the choke screw 19 and duct 2.0 and ignite the primer in primer chamber 17. The primer explodes and forces hot pressurized gases and/or flame into the firing channel y13. The ring channel which runs longitudinally approximately the entire length of the gun, communicates with each gun barrel 26a by means of the ignition duct 23 which, in turn, communicates with the peripheral depression or groove 30 in pressure shear disc 29. From the peripheral groove the gases enter the igniter channel or port cho-ke hole 31 and ignite propellant 2S in propellant chamber 27. The resulting gases build up to a predetermined pressure causing the shear disc 29 to rupture forcing the projectile 38 out of the gun barrel and into and through the target (surrounding casing, etc.).

Since the pressure shear disc `29 is replaceable after each projectile is tired, it is possible touse a greater amount of propellant to drive the projectile through the casing and into the formation. The choke hole or igniter duct in the shear disc minimizes the loss of propellant pressure and damage to the permanent parts of the perforating gun, particularly the ignition channel 23 and the threads of the gun barrel 26 and gun barrel chamber 26a.

It will be seen that by means of the common fir-ing channel 13 which communicates with each of the gun barrel chambers 26a through individual lateral ignition channels 23, all of the projectiles will be fired substantially simultaneously thereby providing a uniformly distributed pattern of perforations in the casing and formation.

While this il-lustrated `embodiment of the invention shows certain highly desirable and useful features such as the pressure seal washer 33, and the ange or pressure seal skirt 32 which is an integral part of the pressure seal disc 29, it is understood that the invention is not limited to the utilization of these features. Also it is contemplated that the perforating gun described herein which utilizes the pressure seal disc 29 in its various forms can employ a tiring means whereby the individual projectiles are discharged sequentially or selectively, instead of simultaneously, for example as illustrated in U.S. Patent No. 2,551,031. It will also be understood that the invention is not limited to any particular construction of the gun barrels and/or the projectiles positioned therein and vari. ous modifications of the features illustrated in this respect can he employed.

Yetv another modification of this invention consists in the utilization of vthe shear disc and complementing parts therefor shown in FIGURES 6, 7 and 8. This modified shear disc uses at least two pieces (see FIGURE 7); a shear disc base 124, having a peripheral groove 130, a shear disc base ignition duct 31, and also a seat and/or an inner peripheral recess to contain the shear disc 126. The placement of these parts in position in the gun barrel is shown in FIGURE 6, which -additionally shows seal wafer 106 (of FIGURE 8) in place.y

A pressure seal skirt 32 may optionallyalso be used on shear disc base 124 as a seal and/or centralizing aid.

The mild steel seal wafer 106, prior to assembly, is a thin cupped shaped disc. It is dropped into the barrel bore 36 with the convex side up and with the other sideA in contact with the shear disc and base. When the barrel 26 with its rubber seal 34l in place is screwed down, it

presses down on the wafer to flatten and thus expand itL to engage the walls on the complete periphery of the gun bore at point A.

This wafer 106 serves two purposes: (l) to Seal at point A, preventing hot gases from blowing out on the barrel threads; and (2) it provides a metal to metal seal bridging the tolerance and clearance gap between the shear disc base and the gun bore walls. This prevents the well fluid from forcing the rubber seal down into the annulus just mentioned, and causing the seal to leak.

The combined thickness of the shear disc andthe Wafer control the pressure buildup in the propellant chamber. Therefore this combined thickness is closely controlled.

This seal wafer also eliminates the need for a rubber seal plug 37 on the bullet because a complete solid shield is effected across the whole shear disc and finally sealed by the rubber barrel seal 34. The bullet is retained by any commercial snap ring or a soft metal washer 109 pressed down into place and retained by frictional contact. It does not have to be fluid-tight. In fact, the bullet can be retained by a good adhesive cement.

The shear disc base 124 may be made from a powdered metal of a type that will easily fragmentize with the explosion. This material is simil-ar to cast iron. This fragmentization permits easy removal of the base 124 from the gun because it will usually split at the ignition duct 31 and directly opposite. Therefore, two pieces literally fall out of the gun'when it is ready to clean. The shear disc base 124 can, of course, be made from other materials, such as cast iron, aluminum, steel, plastics, ceramic, etc.

This application is a continuation-impart of my previously filed application for Device for Perforating Well Casing, Serial No. 631,574, filed December 31, 1956 now abandoned.

I claim as my invention:

1. In a casing perforating gun having means for igniting projectile propellant by hot, pressurized gases and including a gun body having an internal, longitudinal primary firing channel for transmitting said gases, at least one barrel bored in said body to receive a projectile, al

propellant chamber communicating with said barrel, a shoulder between said barrel and said propellant chamber and a replaceable shear disc of large diameter than the propellant chamber positioned against the shoulder of said propellant chamber to form a substantially explosive gas-tight seal, the improvement wherein the face of said shear disc is imperforate and said disc has a peripheral depression, and ignition duct connecting said deprsion with said propellant chamber, and an ignition channel leading from the ring channel in said gun body and registering with the peripheral depression of the shear disc.

2. Apparatus according to claim 1 wherein said peripheral depression consists of an annular groove.

3. Apparatus according to claim l wherein the shear disc has a flange which projects inwardly into and along the inside wall of the propellant chamber when the face of the disc is positioned against the shoulder of the propellant chamber.

4. In a casing perforating gun having ignition means for igniting projectile propellant by hot pressurized gases and including a gun body having secured therein at least one barrel bored to receive a projectile, a propellant chamber communicating with said barrel, a shoulder between said barrel and said propellant chamber, and a replaceable shear disc of larger diameter than the propellant chamber positioned against the shoulder of said propellant chamber to form a substantially explosive gastight seal, the improvement wherein the face of said shear disc is imperforate and said disc has an external peripheral depression and an ignition passage connecting said depression with said propellant chamber and having a flash seal washer positioned between the end face of the gun barrel and the shear disc, said washer also having an inside diameter greater than the diameter of the barrel bore, said disc and washer forming a substantially gas-tight seal when the face of the disc is positioned against the shoulder of the propellant chamber.

5. Apparatus according to claim 4 wherein the outside diameter of the Hash seal washer is greater than the diameter of the shear disc.

6. Apparatus according to claim 4 wherein the shear disc has a ange which projects inwardly into and along the inside wall of the propellant chamber when the face of the disc is positioned against the shoulder of the propellant chamber.

7. In a device for ring projectiles by means of gases from ignited propellant including a gun barrel bored to receive a projectile, a propellant chamber communicating with said barrel, and a disc positioned between said barrel and said chamber and having a diameter greater than the diameter of said chamber, the improvement wherein said disc has an imperforate face and a peripheral groove to receive and convey hot pressurized igniter gases, and an ignition duct communicating said groove with said propellant chamber.

8. A device according to claim 7 and having positioned .f'

between the disc and the barrel a ash seal washer of larger inside diameter than the bore of the gun barrel and larger outside diameter than the diameter of the disc.

9. A device according to claim 7 with a propellant pressure ange integral with said disc and insertable into the propellant chamber, said ange projecting inwardly and along the inside wall of the propellant chamber.

l0. In a casing perforating gun having ignition means for igniting projectile propellant by hot, pressurized gases and including a gun body having secured therein at least one barrel bored to receive a projectile, a propellant chamber `communicating with said barrel, a shoulder between said barrel and said propellant chamber and a replaceable shear disc assemblage of larger diameter than the propellant chamber positioned against the shoulder of said propellant chamber to form a substantiallsl explosive gas-tight seal, the improvement wherein said shear disc assembly possesses a base part which has an external peripheral depression and an ignition duct which connects said ignition means with said propellant chamber, and which base part also possesses an inner peripheral recess upon which is situated a shear disc also of larger diameter than the propellant chamber.

1l. In a casing perforating gun having ignition means for igniting projectile propellant by hot pressurized gases and including a gun body having secured therein at least one barrel bored to receive a projectile, a propellant chamber communicating with said barrel, a shoulder between said barrel and said propellant chamber, and a replaceable shear disc assembly of larger diameter than the propellant chamber positioned against the shoulder of said propellant chamber to form a substantially explosive gas-tight seal, the improvement wherein said shear disc assemblage possesses a base part which has an external peripheral depression and an ignition duct which connects said ignition means with said propellant chamber, and which base part also possesses an inner peripheral recess upon which is situated a shear disc also of larger diameter than the propellant chamber; and a seal wafer straddled across both the base part and the shear disc, the entire assemblage being adapted to form a substantially explosive gas-tight seal when the bar-rel is tightly threaded into the gun body.

12. In a device for ring projectiles by means of gases from ignited propellant including a gun barrel boredto receive a projectile, a propellant chamber communicating with said barrel, and a disc assemblage positioned between said barrel and said chamber and having `a diameter greater than the diameter of said chamber, the improvement wherein said disc assemblage possesses a base part which has an external peripheral depression and an ignition duct which connects said ignited propellant with said propellant chamber and which base part also possesses an inner peripheral recess upon which is situated a shear V disc also of larger diameter than the propellant chamber.

13. A device according to claim 12 and having a seal wafer straddled across both the base part and the shear disc, the entire assemblage being adapted to form a substantially explosive gas-tight seal when the barrel is tightly threaded into the projectile firing device.

References Cited in the file of this patent UNITED STATES PATENTS 2,414,900 Schiavo-n Jan. 28, 1947 2,436,118 Neal Feb. 17, 1948 2,446,235 Markant Aug. 3, 1948 2,551,031 McCullough May 1, 1951