Title:
Well bore perforating apparatus
United States Patent 3923105
Abstract:
In the representative embodiment of the present invention disclosed herein, new and improved selectively-operated perforating apparatus is arranged to include two or more enclosed thin-walled tubular carriers carrying a corresponding number of sets of shaped explosive charges which are to be independently actuated for successively perforating a cased well bore at selected depth intervals. To effectively protect the charges in the yet-unfired carriers during the sequential operation of the perforating apparatus, the carriers are tandemly joined by a unique shock-isolating inter-carrier coupler cooperatively arranged for carrying interconnecting wires between the carriers as well as for at least substantially absorbing the longitudinally directed and laterally directed explosive shocks or impacts which are inherently developed by such sequential firing operations.


Inventors:
LANDS JR JACK F
Application Number:
05/529422
Publication Date:
12/02/1975
Filing Date:
12/04/1974
Assignee:
Schlumberger Technology Corporation (New York, NY)
Primary Class:
Other Classes:
166/55.1
International Classes:
E21B43/1185; E21B43/119; (IPC1-7): E21B43/11
Field of Search:
166/55.1,63 175
View Patent Images:
US Patent References:
3528511APPARATUS FOR SEALING CHAMBERS IN A PERFORATING TOOL1970-09-15Boop et al.
3441093JET PERFORATING GUN ARMING SWITCH AND CIRCUITRY1969-04-29Boop
3216751Flexible well tool coupling1965-11-09Der Mott
3162214Flexible tubular structures1964-12-22Bazinet
3128825N/A1964-04-14Blagg
3100443Shaped charge apparatus1963-08-13Pohoriles
3068946Knuckle joint1962-12-18Frisby et al.
2885461Expansion and deflection conduit coupling1959-05-05Cafiero
2844948Torque transmitting and cushioning means1958-07-29Jarvis
2536216Flexible connections in drill pipe strings1951-01-02Powell
1948211Flexible sealing coupling1934-02-20Fritz
Primary Examiner:
Brown, David H.
Attorney, Agent or Firm:
Archambeau Jr., Ernest Sherman William Moore Stewart R. R. F.
Claims:
What is claimed is

1. Perforating apparatus comprising:

2. The perforating apparatus of claim 1 wherein said rigid coupler members are releasably coupled to said perforating guns.

3. The perforating apparatus of claim 1 wherein said rigid and yieldable coupler members are arranged along the longitudinal axis of said perforating guns with their adjacent surfaces respectively bonded together for inducing shearing stresses in said yieldable coupler member to attenuate laterally directed shocks imposed on said one perforating gun whenever actuation of said other perforating gun shifts it laterally in relation to said one perforating gun.

4. The perforating apparatus of claim 3 wherein said absorbing coupling means further include:

5. The perforating apparatus of claim 1 wherein said coupler members are annularly shaped and further including:

6. The perforating apparatus of claim 5 wherein said rigid and yieldable coupler members are arranged along the longitudinal axis of said perforating guns with their adjacent surfaces respectively bonded together for inducing shearing stresses in said yieldable coupler member to attenuate laterallydirected shocks imposed on said one perforating gun whenever actuation of said other perforating gun shifts it laterally in relation to said one perforating gun.

7. The perforating apparatus of claim 6 wherein said absorbing coupling means further include:

8. Perforating apparatus comprising:

9. The perforating apparatus of claim 8 wherein said flexible cables are at least partially embedded within the exterior surface of said elastomeric member.

10. Perforating apparatus comprising:

11. The perforating apparatus of claim 10 wherein there are a plurality of said flexible load-supporting members disposed around said elastomeric coupling member and at least partially embedded in the exterior surface thereof.

Description:
Present-day completion techniques often require the perforation of a well at two or more different depth intervals. Very often this must be carried out without removing the small-diameter production tubing from the well. To accomplish this, it is customary to tandemly arrange a corresponding number of small-diameter perforating guns into a selectively controlled unitary assembly and, by means of a typical electrical cable, lower the assembled tool through the production string to the depth interval where the first gun is to be operated. Thereafter, the perforator tool is repositioned and the second gun is operated for perforating the formations at the second depth interval. This procedure is repeated until all of the several guns in the perforator tool have been fired.

Those skilled in the art will, of course, appreciate that where each of these guns include a number of shaped explosive charges, the simultaneous detonation of these charges will impose severe shocks and sudden impacts on the entire perforator tool. This problem has been accentuated by the recent development of more-powerful charges. In particular, where the charges are carried in thin-wall tubular carriers such as those shown in U.S. Pat. No. 3,048,102 and U.S. Pat. No. 3,429,384, these carriers are typically so light that the entire perforator tool will often be driven laterally with considerable force each time the charges in one of the carriers in the tool are detonated.

Accordingly it has been not at all uncommon to find that the operation of the first set of charges in a tandem assemby of such light-weight carriers has damaged one or more of the unexpended shaped charges in the adjacent carriers in the perforator tool. For example, as shown in FIG. 2 of the aforementioned U.S. Pat. No. 3,429,384, there is ordinarily a minimal clearance space between the internal carrier wall and the forward and rearward portions of the shaped charges. Thus, the sudden impact or shock developed upon firing of one set of charges will rapidly drive or shift an adjacent carrier of this type laterally in relation to the several shaped charges enclosed therein since the charges are typically supported by only a thin, generally flexible metal strip. Forceful inertial movements of this nature are known to be particularly responsible for damage to the exposed forward ends or skirt portions of the fragile liners typically used in such shaped charges. Similarly, it has been found that vertical movements or jumping of the perforator tool caused by detonation of one set of charges can also damage the metal strips carrying the unexpended shaped charges in adjacent carriers. In either case, it has been found that often one or more of the shaped charges in these adjacent carriers are sufficiently damaged that they will not operate properly when these charges are subsequently detonated.

Accordingly, it is an object of the present invention to provide new and improved repetitively operated shaped charge perforating apparatus which is cooperatively arranged for protecting unfired shaped charges in the apparatus from explosive impacts or violent shocks which might otherwise damage or disrupt these unexpended charges upon the detonation of other shaped charges in the apparatus.

This and other objects of the present invention are attained by tandemly intercoupling upper and lower perforating guns by means of rigid and yieldable coupling members, with one of the guns being secured or coupled to one of the rigid members located below an intermediately located yieldable member and the other gun being secured or coupled to another one of the rigid members above that yieldable member. In this manner, the yieldable member disposed between the two rigid members will effectively isolate the two guns from explosive impacts and shocks developed upon actuation of the other gun. The assembly of coupler members is further arranged to define a protective wire passage for carrying interconnecting electrical wires between the two guns.

The novel features of the present invention are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may be best understood by way of the following description of exemplary apparatus employing the principles of the invention as illustrated in the accompanying drawings, in which:

FIG. 1 shows new and improved perforating apparatus arranged in accordance with the present invention as that apparatus is being positioned in a typical well bore; and

FIG. 2 is an enlarged longitudinal cross-sectional view of a preferred embodiment of a new and improved shock-resistant inter-carrier coupler incorporating the principles of the present invention.

Turning now to FIG. 1, new and improved through-tubing perforating apparatus 10 is shown as it is being positioned in a typical cased well bore 11 adjacent to one of two producible earth formations 12 and 13. As is customary, a string of small-diameter tubing 14 is suspended in the well bore 11 and extended through a typical packer 15 set therein above the earth formations 12 and 13 for isolating the two producing zones from that portion of the well bore above the packer. The perforating apparatus 10 is suspended in the usual manner from a suitable electrical cable 16 that is spooled from a winch (not shown) at the surface and connected to the upper end of the perforating apparatus. As is customary, a typical casing collar locator 17 is employed for providing indications at the surface representative of the depth of the perforating apparatus 10.

Inasmuch as it is intended that the perforating apparatus 10 will be successively positioned opposite each of the formations 12 and 13, the perforating apparatus includes separate upper and lower guns 18 and 19 which are cooperatively arranged to be individually operated upon command from the surface. In the preferred embodiment depicted in FIG. 1, the two guns 18 and 19 are respectively arranged in accordance with the through-tubing perforators shown in either U.S. Pat. No. 3,048,102 or U.S. Pat. No. 3,429,384, each of which is hereby incorporated by reference. Thus, as fully described in either of the aforementioned patents, each of the guns 18 and 19 respectively includes an enclosed carrier 20 and 21 formed of a suitable length of thin-walled steel tubing which has a number of typical shaped explosive charges, as at 22 and 23, mounted at longitudinally spaced intervals along an elongated metal strip (not shown) arranged therein for positioning each of the charges for firing in a selected lateral direction. It will, of course, be appreciated that each of the guns 18 and 19 is respectively provided with an electrically responsive detonator (not shown) which is coupled to a length of typical detonating cord (not shown) operatively disposed along the rear portion of each of the charges, as at 22 and 23, for simultaneously detonating them when the detonator in that gun is energized.

Since the guns 18 and 19 are to be independently fired, suitable provisions must be made for their selective operation. Those skilled in the art will recognize, of course, that any one of several typical switching arrangements may be utilized for achieving such selective control. For example selectively operated switching systems such as those shown in either U.S. Pat. No. 3,327,791 or U.S. Pat. No. 3,517,758 could be successfully employed with the new and improved perforating apparatus 10 of the present invention where the switching is to be directly controlled from the surface. Alternatively, if it is preferred that the switching be accomplished upon firing of the lower gun 19, for example a detonation-responsive control system, as at 24, would be included with the new and improved perforating apparatus 10. Typical detonation responsive control systems, as at 24, are fully described in U.S. Pat. No. 3,246,707 and U.S. Pat. No. 3,246,708, each of which is incorporated herein by reference. It will, or course, be appreciated that since it is ordinarily preferred to shoot the lowermost gun first and then subsequently shoot the next-higher gun, the detonation-responsive control system 24 is operatively positioned adjacent to the upper end of the lower gun 19 so that successful detonation of the charges, as at 23, will electrically connect the cable 16 to the detonator for the yet-unexpended charges, as at 22, in the upper gun 18. Since the two last-mentioned patents fully explain the operation of the detonation-responsive control system 24, no further explanation is believed necessary. It should be realized, however, that regardless of the control system used, electrical wires must be connected between the upper and lower guns 18 and 19 and it is essential to their successful operation that these wires remain undamaged at least until the upper gun is fired.

The upper and lower guns 18 and 19 in the new and improved perforating apparatus 10 are tandemly intercoupled by means of a uniquely arranged shock or impact resistant intercarrier coupler 25 which, as will be subsequently explained, is cooperatively arranged for substantially absorbing the severe impact or shock forces developed upon detonation of the shaped charges, as at 23, in the lower gun 19 to thereby protect the yet-unfired charges, as at 22, in the upper gun 18 from unwanted damage. Thus, as best seen in FIG. 2, in its preferred embodiment the unique shock or impact-resistant inter-carrier coupler 25 includes a pair of oppositely directed, cup-shaped end pieces 26 and 27 of a rigid material such as steel which are joined by one another by a body 28 of a yieldable or resilient shock-absorbing material such as a suitable elastomer. The unique shock-resistant inter-carrier coupler 25 further includes a cylindrical body or upper head 29 which is adapted to be complementally fitted and secured in a known angular position within the lower tubular end of the upper carrier 20 within the upper end piece 26. Similarly, a cylindrical body or lower head 30 on the other end of the impact-resistant coupler 25 is secured in a known angular position in the lower carrier 21 and coupled to the lower end piece 27 as by one or more bolts or screws 31.

It will, of course, be appreciated that where the switching system 24 is arranged in accordance with the aforementioned U.S. Pat No. 3,246,707 or U.S. Pat. No. 3,246,708, for example, the lower head 30 can also be conveniently arranged as necessary for readily supporting the components of such a detonation-responsive system as well as for being complementally fitted and fluidly sealed within the upper end of the lower carrier 21.

To facilitate the necessary electrical interconnection between the guns 18 and 19, a wire passage is provided through the inter-carrier coupler 25 by way of an elongated and somewhat-flexible tubular conduit 32 which is coaxially disposed within the stacked coupler members 26-28 and has its enlarged upper and lower ends 33 and 34 fluidly sealed within the complemental counterbores 35 and 36 respectively formed in longitudinal passages 37 and 38 respectively arranged through the upper and lower coupling heads 29 and 30. It will be noted from FIG. 2 that the counterbores 35 and 36 are of sufficient length to accommodate the longitudinal movements of the wire conduit 32 during the use of the new and improved inter-carrier coupler 25. As a matter of operating convenience, a lateral port 39 with a threaded plug 40 are provided in the lower head 30 to facilitate the splicing of the interconnecting detonator wires (not shown) running between the two guns 18 and 19.

It will be recognized, therefore, that with the upper and lower guns 18 and 19 being intercoupled to one another solely by the unique coupler 25, the lower gun is directly connected to the upper gun only by way of the resilient member 28 and the end pieces 26 and 27. Thus, an upwardly directed shock on the upper gun 18 (as will be occasioned by the detonation of the charges, as at 23, in the lower gun 19) will be substantially cushioned by the respective expansion and compression of the resilient coupler member 28. Similarly, since the resilient member 28 is sufficiently yieldable under impact for allowing the rigid coupler members 26 and 28 to move laterally or tilt in relation to one another, the resilience as well as the elasticity of shear of the resilient coupler member will effectively absorb or dampen a considerable amount of the laterally directed shocks or impacts which would otherwise be transmitted to the upper gun 18 when the lower gun 19 is fired. It should be noted at this point that although firing of the lower gun 19 will impart a substantial accelerational force to the lower gun, the operation of the inter-carrier coupler 25 will be effective for at least minimizing or reducing the acceleration of the upper gun 18.

As discussed above, the elastomeric element 28 is firmly bonded to the two end pieces 26 and 27; and, ordinarily, it would be expected that the overall assembly 25 will be of sufficient strength to safely support the lower gun 19. However, as a matter of achieving total reliability, the two end pieces 26 and 27 are further interconnected by means of one or more flexible cords or metal cables, as at 41 and 42, which are uniformly spaced around the elastomeric member 28. In one manner of securing the cables 41 and 42 to the end pieces 26 and 27, a spherical head, as at 43, may be secured to each end of each cable and disposed in a complementary enlargement 44 which is formed in the wall of the end piece and connected to a reduced-diameter groove 45 adapted to carry the adjacent end portion of the cable. To retain the heads 43 in position, the ends of the elastomeric member 28 are preferably extended, as at 48, for trapping the cable ends in their respective opening 44 and 45. Accordingly, should the elastomeric element 28 fail, the several cables, as at 41 and 42, will be of sufficient strength to support the full weight of the lower gun 19.

It should be noted that by virtue of their flexibility, the cables 41 and 42 present little or no restraint to either axial bending of the elastomeric element 28, compressional movement of the element, or to relative lateral movements of the end pieces 26 and 27 which would impose a shearing stress on the elastomeric member. Thus, the cables 41 and 42 will not unduly limit the shock-attenuation provided by the coupler 25. It should also be noted that by arranging the end pieces 26 and 27 to be separate from their respectively-associated heads 29 and 30, damage to the new and improved coupler assembly 25 will allow its replacement without having to also replace the more-expensive heads.

Accordingly, it will be appreciated that the new and improved repetitively-operated perforating apparatus of the present invention is well suited for guarding yet-unfired shaped charges from damage as other shaped charges on the apparatus are fired. By intercoupling two or more typical shaped charge guns with the new and improved inter-carrier coupler disclosed herein, the severe explosive shocks and excessive accelerational forces developed upon actuation of one of the guns in the assembled tool will be sufficiently dampened or absorbed that there will be little or no risk of damage to the shaped charges in the other guns.

While only a particular embodiment of the present invention has been shown and described, it is apparent that changes and modifications may be made without departing from this invention in its broader aspects; and, therefore, the aim in the appended claims is to cover all changes and modifications as fall within the true spirit and scope of this invention.