10/611,188, filed 1 July 2003 in the United States Patent & Trademark Office, U. S. Patent Application Serial No. 10/610,740 filed 1 July 2003 in the United States Patent & Trademark Office, and U. S. Patent Application Serial No. 10/612,207 filed 1 July 2003 in the United States Patent & Trademark Office.

FIELD OF THE INVENTION BACKGROUND OF THE INVENTION Well completion techniques normally require perforation of the ground formation surrounding the borehole to facilitate the flow of interstitial fluid (including gases) into the hole so that the fluid can be gathered. In boreholes constructed with a casing such as steel, the casing must also be perforated. Perforating the casing and underground structures can be accomplished using high explosive charges. The explosion must be conducted in a controlled manner to produce the desired perforation without destruction or collapse of the well bore.

Hydrocarbon production wells are usually lined with steel casing. The cased well, often many thousands of feet in length, penetrates varying strata of underground geologic formations. Only a few of the strata may contain hydrocarbon fluids. Well completion techniques require the placement of explosive charges within a specified portion of the strata. The charge must perforate the casing wall and shatter the underground formation sufficiently to facilitate the flow of hydrocarbon fluid into the well as shown in Figure 1. However, the explosive charge must not collapse the well or cause the well casing wall extending into a non-hydrocarbon containing strata to be breached. It will be appreciated by those skilled in the industry that undesired salt water is frequently contained in geologic strata adjacent to a hydrocarbon production zone, therefore penetration of the casing requires accuracy and precision.

The explosive charges are conveyed to the intended region of the well, such as an underground strata containinghydrocarbon, bymulti-componentperforation gun system (hereinafter sometimes referred to as"gun system"or"gun string". The gun string is typically conveyed through the cased well bore by means of coiled tubing, wire line, or other devices, depending on the application and service company recommendations. Although the following description of the invention will be described in terms of existing oil and gas well production technology, it will be

appreciated that the invention is not limited to those applications.

Typically, the major component of the gun string is the"gun carrier"tube component (hereinafter sometimes referred to as"gun") that houses multiple shaped explosive charges contained in lightweight precut"loading tubes"within the gun. The loading tubes provide axial circumferential orientation of the charges within the gun (and hence within the well bore). The tubes allow the service company to preload charges in the correct geometric configuration, connect the detonation primer cord to the charges, and assemble other necessary hardware. The assembly is then inserted into the gun as shown in Figure 2. Once the assembly is complete, other sealing connection parts are attached to the gun and the completed gun string is lowered into the well bore by the conveying method chosen.

The gun is lowered to the correct down-hole position within the production zone, and the charges are ignited producing an explosive high-energy jet of very short duration as indicated in Figure 3. This explosive jet perforates the gun and well casing while fracturing and penetrating the producing strata outside the casing. After detonation, the expended gun string hardware is extracted form the well or release remotely to fall to the bottom of the well. Oil or gas (hydrocarbon fluids) then enters the casing through the perforations. It will be appreciated that the size and configuration of the explosive charge, and thus the gun string hardware, may vary with the size and composition of the strata, as well as the thickness and interior diameter of the well casing.

Currently, cold-drawn or hot-drawn tubing is used for the gun carrier component and the explosive charges are contained in an inner, lightweight, precut loading tube. The gun is normally constructed from a high-strength alloy metal. The gun is produced by machining connection profiles on the interior circumference of each of the gun's ends and"scallops", or recesses, which are cut along the gun's outer surface to allow protruding extensions ("burrs") created by the explosive discharge through the gun to remain near or below the overall diameter of the gun. This method reduces the chance of burrs inhibiting extraction or dropping the detonated gun. High strength materials are used to construct guns because they must withstand the high energy expended upon detonation. A gun must allow explosions to penetrate the gun body, but not allow the tubing to split or otherwise lose its original shape Extreme distortion of the gun may cause it to jam within the casing. Use of high strength alloys and relatively heavy tube wall thickness has been used to minimize this problem.

Guns typically are used only once. The gun, loading tube, and other associated hardware items are destroyedbythe explosive charge. Although effective, guns are relatively expensive. Most of the expense involved in manufacturing guns is the cost of material. These expenses may account

for as much as 60% or more ofthe total cost of the gun. The oil well service industry has continually sought a method or material to reduce the cost while also seeking to minimize the possibility of misdirected explosive discharges or jamming of the expended gun within the well.

Although the need to ensure gun integrity is paramount, efforts have made to use lower cost steel alloys through heat-treating, mechanical working, or increasing wall thickness in lower-strength but less expensive materials. Unfortunately, these efforts have seen only limited success. Currently, all manufacturers of guns are using some variation of high strength, heavy-wall metal tubes.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention. These drawings, together with the general description of the invention above and the detailed description of the preferred embodiments below, serve to explain the principals of the invention.

Figure 1 illustrates the effect of an explosive discharge from a well perforating gun of the present invention disposed in a well bore, the explosive discharge penetrating through the well casing and into the surrounding geologic formation Figure 1 A is a cross sectional view of a well perforating gun of the present invention having two layers; Figure 1B is a side view of the first layer of a well perforating gun of the present invention with scallops disposed therethrough; Figure 2 is a side view of one embodiment of a well perforating gun of the present invention disposed in a well bore showing the relationship between the loading tube, gun wall, charges and detonation cord.

Figure 2A is a top view of a well perforating gun of the present invention, taken along the line 2A-2A shown in Figure 2; Figure 3 is a side view illustrating the effect of a high-energy explosive gas jet that is produced when a charge detonates.

Figure 4 illustrates one embodiment of the present invention wherein the perforating gun is comprised of an engineered sequence of layered materials; Figure 5 illustrates an embodiment of the well perforating gun of the present invention showing use of perforated tubing, thereby eliminating machining of scallops; Figure 6 illustrates a side-cross section view of the layered wall construction of the well perforating gun of the present invention, taken along the line Vm-Vm of Figure 5;

Figure 7 illustrates an embodiment of the present invention showing a multi-layer gun wall formed by a wrapping one or more layers about an inner layer; Figures 8 and 8A illustrate a detailed embodiment of the present invention employing energy absorption zones between the layers of the gun wall according to the invention; Figure 9 illustrates an embodiment of the present invention utilizing wrapped layer wire around the inner most layer according to the invention; Figure 10 is a side sectional view of the present invention with a scallop configuration and a multilayered gun wall; Figures 10A-l OF illustrate various designs for precut recesses in gun wall layers; Figure 11 shows cut-away sections of the gun wall of the present invention have having scallop configuration of complex side wall design; Figure 12 illustrates a prior art machined scallop having a constant diameter; and Figures 13A and 13B are side views of a gun wall of the present invention illustrating a weld seam connecting components to multiple layers of gun wall requiring less machining.

The above general description and the following detailed description are merely illustrative of the subject invention, additional modes, and advantages. The particulars of this invention will be readily suggested to those skilled in the art without departing from the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention disclosed herein provides for an improved well perforating gun, a method of making the well perforating gun and a method of using the well perforating gun.

The invention disclosed herein incorporates novel engineering criteria into the design and fabrication of well perforating guns. This criterion addresses multiple requirements. First, the ability of gun material (steel or other metal) to withstand high shocks delivered over very short periods of time ("impact strength") created by the simultaneous detonation of multiple explosive charges ("explosive energy pulse"or"pulse") is more important than the gun material's ultimate strength. This impact strength is measurable and is normally associated with steels with 200 low carbon content and/or higher levels of other alloying elements such as chromium and nickel. S econd the shock of the explosion transfers its energy immediately to the outside surface of the tubing. Any imperfections, including scallops, will act as stress risers and can initiate cracking and failure.

In one embodiment, the ability of the gun to withstand the shock of the explosion from the gun by enabling the gun wall to transfer its energy immediately to the outside surface of the tubing quickly and smoothly has been improved. In another embodiment, the overall strength of the gun

is improved.

Figure 1 illustrates the basic casing perforation operation in which the well perforating gun and its fabrication method, as disclosed in this specification, are utilized. A gun 200 having a longitudinal axis 115 is suspended within a well bore 110 by a coil tube or a wire line device 250.

Charge (s) (not shown) contained within the gun are oriented in 90° around the circumference of the gun. An explosive gas jet 450, produced by detonation of the charge (s) penetrates the gun wall 210 and well casing 100 creating fractures 930 in the adjacent strata 950. Penetration of the gun wall 210 is intended to occur at machined recesses 220 disposed in the gun wall. The recesses are fabricated in a selected pattern around the circumference of the gun wall.

Referring now to Figure 1A, gun 200 is shown comprising a first layer 1002, an outer layer 1006, and a loading tube 1000 inserted within the first layer 1002. Charges 251,251a, 251b and 251c are contained within the gun and are oriented at 90° intervals around the circumference of the gun. The charges 251,251a, 251b and 251c are disposed in the loading tubing 1000 in a helical arrangement. In an alternative embodiment, the outer layer is fixed to the first layer using an interference fit. It is also contemplated that the gun wall of the present invention can have at least a third layer disposed between first layer and the outer layer, and can be composed of multiple layers, as discussed hereinafter. In addition, it should be noted that the outer layer and the first layer can welded togther or can be adhered together, such as by the use of a binder or laminating agent disposed between the layers.

Penetration of the gun wall is intended to occur at machined recesses, termed"scallops"in the outer layer 1006 of gun wall 210. As shown in Figure 1B, the scallops are depicted as elements 220,220a, 220b, 220c, and 220d. The scallops are positioned in the solid structure of the outer layer in a defined pattern. In the most preferred embodiment, the orientation of the outer layer is parallel to the longitudinal axis of the gun. The scallops are fabricated in a selected pattern around the circumference of the gun in at least the outer layer. In a preferred embodiment, the outer layer of the gun 1006 is a solid surface with scallops disposed therein. The scallops preferably are holes.

In a preferred embodiment, the density of the scallops is at least 1 scallop per foot and up to 21 scallops per foot disposed in the solid structure, and each scallop has a diameter between about a quarter inch (0.25") and one and one-half inches (1.5").

It is desirable to use various arrangements or orientations of the charges ("shots") in the loading tube and to varying the numbers of charges within a given area ("shot density"). This permits variation in the effect and the directionality of the explosive charges. In Figure 1B, the

orientation of the explosive charges or"shots"are shown arranged in a typically helical orientation as charges 251, 251a, 251b and 251c around the gun wall of the gun. However, it is to be understood that the orientation of the charges can vary ; for example, the charges can be oriented in straight lines parallel to the longitudinal axis 115 of the gun.

Guns typically are produced in increments of five feet, with the most common gun being about twenty feet. These guns may hold and fire as many as 21 charges for every foot of gun length.

Perforation jobs may require multiple combinations of 20-foot sections, which are joined together end to end by threaded screw-on connectors. The present invention contemplates that at least two of the novel guns can be connected together, such as with seals, threaded connections or a similar securing devices.

Figures 2 and 2A illustrates the basic components of the gun 200 and the relationship between the gun wall 210, loading tube 1000, charges 251, and detonation cord 421. The longitudinal axis 115 of the gun is parallel to the axis of the borehole, Figure 2A is a sectional view of the gun 200 taken along the line 2A-2A. The loading tube and charge (s) are located within the annulus 215 of the gun wall 210. Also shown is a recess or scallop 220 machined into the outer layer of the gun wall at locations specified to be immediately adjacent to each explosive charge. The charge 251 typically includes the explosive charge 410, shape charge body 324, primer vent 325 and retainer cone 326. Of course, it will be understood to those skilled in the art that differing well conductions, casings, strata, and the like can create a need for varying configurations and properties of the loading tubes, charges, and mounting hardware.

The high-energy explosive gas jet 450 that is produced when a charge detonates is illustrated in Figure 1 and Figure 3. The duration of this explosive event is only of an extremely small fraction of a second and can be considered to be an explosive pulse occurring at detonation. During the violent and explosive energy pulse, the charge casing, loading tubes, and other gun components are subjected to an immediate, non-uniform change in pressure and temperature. The detonation cord 421 ignites the explosive 410 at the primer vent 325 within the non-combusting shaped charge body 324. The entire explosive within the charge ignites nearly instantaneously. Ignition within the shaped charge focuses an explosive jet 450 of expanding hot gas radially outward direction 452 toward the gun wall 210. As the gun wall proximate to the short duration explosive jet or energy pulse contains a machined recess or scallop 220, it has a decreased thickness relative to the non- scalloped gun wall. The explosive jet 450 perforates through the gun wall at the machined scallop and continues through the narrow space between the gun wall 210 and the well casing 100. The

explosive jet energy 450 also perforates the well casing 100. The energy of the jet creates one or more shock waves 455 that creates fracture 930 the geologic formation. It will be appreciated that the amount of energy required to penetrate the gun body is reduced by the thickness provided by the scallops.

The invention also relates to a method of making a well perforating gun for use in oil and natural gas wells comprising the steps of : (1) obtaining a length of a first tube; (2) machining one or more scallops into the first tube to form an outer layer; (3) placing the outer layer in a holder; (4) cutting a second tube to the approximate length of the outer layer; (5) pulling the second tube into the outer layer to form a laminate structure having a first end and a second end; and (6) inserting a loading tube into the laminate structure. The length of the first tube preferably is between about 1 foot and about 40 feet. The length of second tube preferably also is between about 1 foot and about 40 feet. Preferably, each of the first and second tubes have an outer diameter ranging between about 1.5 inches and about 7 inches. Metal suitable for use with the outer layer and the first layer can have a tensile strength between 36 ksi and 400 ksi. Suitable metals include, for example, a chrome alloy, a nickel alloy, a steel alloy, and combinations thereof. The first and outer layers can be composed of the same material or differing materials. For example, in one variation of the invention, the inner layer can be composed of high-strength material (such as the high-strength, alloy metals currently used for guns) and the outer tube can be composed of a mild steel.

The machining of recesses or scallops into the outer layer of the invention can be performed by either a laser, a drill or a mill. The scallops preferably are machined (cut) into the outer layer at a density of at least 1 scallop per foot to about 21 scallops per foot; each scallop has a diameter between about a quarter inch (0.25") and one and one-half inches (1.5"). The pulling of the second tube into the first tube is accomplished using a gear reduced drive and chain mechanism. In pulling the two tubes together, the method of the present invention contemplates using a holder which is a heavy walled tube that is at least 0.020 larger in diameter than the diameter of the first tube.

An additional step comprises forming the thread protectors on a lathe prior to insertion into the first and second ends the laminate structure. Another additional step includes machining internal structures into the laminate structure as will be discussed below.

The design criteria specified by the invention can be used to create an alternative gun tube construction that eliminates many of the problems and costs of the heavy walled tubing currently used. Although it should be understood that multiple embodiments of new gun material selection and construction are within the scope of this invention, attention should be first directed to the design and fabrication of gun tubing utilizing multiple layers of material. This method includes

fabrication by layering or lamination of materials around a radius encompassing the longitudinal axis of the gun tube.

Thus, in one embodiment of the present invention, an additional step comprises cutting one or more additional tubes to the approximate length of the outer layer and pulling the additional tube (s) into the laminate structure to form a multi-layer gun wall. For example, if a third layer is used, it can be located between the first and outer layers and it can be a perforated sheet comprising a plurality of holes, wherein the holes comprise a diameter between about 0.020 inches and about 1.0 inch, and a density of approximately 1 to 700 holes per inch. In an alternative embodiment it is contemplated that the third layer is a solid sheet.

In yet another embodiment, it is contemplated that the gun can have a four layer construction, wherein a fourth layer is disposed between the third layer and the outer layer. It is contemplated that the fourth layer is a solid material. Alternatively, the fourth layer can be an energy absorbing layer disposed between any two layers of the gun wall. It is contemplated that the energy absorbing layer is a perforated sheet or it can be a solid sheet. If it is a solid sheet, it is contemplated that it can comprise lead, magnesium, copper, aluminum, and alloys thereof and a non-metallic substance, such as a ceramic, paper, cardboard, or a pressure laminate composite. If a perforated sheet is used as the energy absorbing layer, it is contemplated that it comprises lead, magnesium, copper, steel, stainless steel, aluminum, and alloys thereof. The density per inch for the perforated sheet is contemplated to be between about 1 hole per square inch and about 700 holes per square inch wherein the diameter of the holes ranges between 0.020 inches and 1 inch.

Referring now to Figure 4, the construction of a gun wall 210 comprised of four material layers or tubes is illustrated. The orientation of each layer is parallel or at a constant radius to the longitudinal axis 115 of the gun 200 and the well bore (not shown). Each layer 210A, 210B, 210C and 210D has a thickness 231A, 231B, 231C and 231D respectively and an outer surface 218A, 218B, 218C and 218D, respectively. The thickness of each layer can be varied. The diameter of the annulus 215 formed within the inner tube also can be varied. The outer surface of each respective layer may be varied in construction to facilitate binding and retard delamination. Such designs may facilitate the strength characteristics of the gun wall in alternate directions, such as traverse or longitudinal directions. It is known that multilayered constructions can have numerous advantageous over conventional, monolithic material constructions. It will be understood by those skilled in the art that the present invention does not limit the number of layers, the composition of the individual layers, or the manner in which layers are assembled or constructed. Further, the

invention is not limited to the use of a binder or laminating agent between material layers.

It will be appreciated that lamination of multiple layers of the same or differing materials maybe used to enhance the performance over a single layer of material without increasing thickness.

Use of fibrous materials, such as high strength carbon, graphite, silica based fibers and coated fibers are included within the scope of this invention. Although some embodiments may utilize one or more binding elements between one or more layers of material, the invention is not limited to the use of such binders. Plywood is an example of enhancing material properties by layering wood to produce a material that is superior to a solid wood board of equal thickness. Applications of multi- layered lamination can be subdivided into primary and complex designs. Additional embodiments of the invention are described below.

Referring now to Figure 5, in one embodiment, the construction of the gun wall is the primary"tube-within-a-tube"design, having a longitudinal axis 115. The outer layer 210D is in the form of a cylinder or tube in which holes 230A and 230B have been cut through the thickness 231D of the outer surface of layer 210D. The diameter of the outer cylinder 210D is approximately equal to the outer diameter of the next inner cylinder 210C. In the embodiment illustrated in Figure 5, there are no holes cut through the outer wall of the next inner cylinder 210C. Therefore, the combined cylinder, comprising the"tube-within-a-tube"of layers 210D and 210C, has the approximate physical shape of the prior art single walled gun having recesses or scallops machined into the outer surface of the wall. Preferably, holes 230A and 230B are cut through the outer cylinder wall 210D prior to assembly of the two cylinders 210C and 210D in the"tube-within-a- tube", thereby eliminating the need for machining. It will be appreciated that the resulting recess 225 formed by the holes 230A and 230B is comparable to the recess or scallop 220 machined into the gun wall 210 of the earlier Figures.

Figure 6 is a cross-sectional view through hole 230A taken along the line vm-vm, and shows a portion of the inner cylinder wall 210C and its relationship with the outer wall 210D and annulus 215. The thickness 231D of outer cylinder wall 210D forms the side wall 228 of recess 225 and the outer surface 218C of the next inner cylinder 210C forms the bottom wall 229. It is to be noted that this illustration does not depict the radial curvature of each layer. The diameter 288 of the hole 230A may be varied. The axis 119 of the resulting hole 230A may be orthogonal to the longitudinal axis 115.

Figure 6 also illustrates the ability to perform machining or other fabrication on the individual layers prior to assembly into the completed unit. For example, machining of connector

structures can be performed on the inner layers individually prior to being inserted or pulled into the larger outer-more layers. These structural components may be machined threads, seal bores, etc.

Figure 6 also illustrates a design that incorporates a machined connection end components 591 and 592 on the innermost layer of a multilayered tube construction.

As discussed above, it is not necessary that the interface 212 (as shown in Figure 6) of the surfaces of the inner and outer layers be bound or otherwise mechanically attached together. An advantage to this design is its simplicity and ease of manufacture. Each of the layers may have different chemical and mechanical characteristics, depending on the performance needs of the perforation work. Alternatively, each layer can be made of the same material. In another variation, each of the layers can be made of the same material but oriented differently to achieve the desired properties (similar to the mutually orthogonal layering of plywood). h yet another embodiment of this design, a further variation can be implemented by offsetting a seam of each layer in the manufacturing process by rolling the flat material forming the layer into a tubular shape.

Figure 7 illustrates an embodiment of the invention in which the gun has four material layers (210D, 210C, 210B and 210A). However, it is to be understood that the invention is not limited to just four layers. The multilayer design might consist of"tube-within-a-tube"fabrication or the wrapping of material around the outer surface of an inner tube maintaining a relative uniform radius about a central axis 115. The inner layer or tube defines the area of the tube annulus 215. Each of the layers may be seamless or rolled. It will be readily appreciated that layering material can be wrapped in various orientations 285 and 286 to provide enhanced strength.

Referring now to Figure 7, layers 210C and 210B are shown helically wrapped orientation 285 at a radius around the longitudinal axis 115. The next inner layer 210A is shown in the form of a rolled tube having a seam parallel to the longitudinal axis. It will also be appreciated that the wrapping might include braiding or similar woven construction of material. Figure 7 also illustrates that any given layer 210C and 21 OB might consist of a material"tape"wrapped around an inner tube or layer 210A. The inner most layer 210A also can be formed around a removable mandrel (not shown).

Wrapping designs and fabrication techniques allow far greater numbers of metals and non- metallic materials to be used as lamination layers, thereby achieving cost savings and reducing production and fabrication times. Improved rupture protection can be achieved without increasing the weight or cost. The laminations can consist of other metals or non-metals to obtain desirable characteristics. For example, aluminum is a good energy absorber, as is magnesium or lead. The

present invention does not limit the material choices for the lamination layers or the manufacturing method in obtaining a layer. Rather, it specifies that layers exist and provide advantages over single- wall, monolithic gun designs.

Also illustrated in Figure 7 are one or more layers 210D and 210C containing holes 230D and 230C, respectively, each of the holes having diameters cut prior to assembly. The hole 230D cut into the outer tube 210D has a diameter 288. The axis of the holes can be orthogonal to the longitudinal axis 115 of the gun wall. The tube layer thickness 231D and 231C forms the wall of the recess 225 and the outer surface 218B of the next underlying layer 21 OB forms the bottom of the recess. The architecture of the resulting recess is comparable, but advantageous to, the prior art machined scallops.

Figure 8 illustrates how a perforated or non-continuous material can produce a lamination layer, even though voids may exist within that layer. The layers might consist of continuous sheets with regular perforations, woven sheets of wire, bonded composites, etc. An energy absorption layer 210C contains numerous perforations 226 each having small diameter 289. Figure 8 also shows a recess 225 in the gun wall 210 fabricated from hole 230D cut through selected layer 210D prior to assembly of the combined tubes. The outer surface 218C forms the bottom of the precut recess 230D. In another embodiment, not shown, the voids might contain material contributing to material strength at ambient temperature and pressure, but that is readily vaporized by the explosive high- temperature andhigh-pressure energypulse, therebyprovidingminimal energyimpedanceproximate to the explosive charge, recess and well casing, but maximum shock absorption in other portions of the gun not immediately subjected to the directed high temperature explosive gas jets.

Referring now to Figure 8A, the energy absorption layer 210C has mechanical properties permitting the inner layers 210B and 210A to expand into the volume occupied by the absorption layer in response to the high impact outward traveling explosive energypulse occurring upon charge detonation. This mechanical action will consume energy that might otherwise contribute to a catastrophic failure of the outer layer 210D. As already discussed, such failure can hinder the intended perforation of the well casing and the surrounding geologic formation (not shown) or hinder the removal of the gun from the well. These mechanical property enhancements allow higher strength, thinner wall perforating guns with high impact resistance and energy absorption.

In addition to the specific energy absorbing layer shown in Figures 8 and 8A, it will be appreciated that each layer could provide strength or other properties specifically selected by the design engineer to meet conditions of an individual well bore. Therefore, this invention allows wall

thickness and composition to become design variables without needing mill runs or large quantities of material.

Figure 9 illustrates an embodiment using helically wound fiber or wire 397 and 398 around an inner layer 210A. The wrapping can also be performed utilizing a removable mandrel. The wrapped layers 210B and 210C can be combined with tubes or cylindrical layers 210A and 210D.

The tube layers can incorporate a precut hole 230 in the outer layer 210D. The winding may be performed prior to placement of the next outer layer. The fiber or wire can be high strength, high modulus material. This material can provide strength against the explosive pulse. The diameter of the fiber or wire and/or the thickness of wrapping can be varied for specific job requirements. The geometry of the winding (or braiding) can be varied, particularly in regard to the orientation to the longitudinal axis 115.

The step of wrapping the wire is performed by winding the wire in a first layer at an angle which is between 0 and 60 degrees from the horizontal axis of the second length of tube. In another embodiment, the step of wrapping the wire is performed by winding the wire in a second layer over the first layer at an angle which is between 0 and 60 degrees from the angle at which the first layer was wound. The wrapping of the wire can be repeated for up to 8 layers and wherein each layer is at an angle between 0 and 60 degrees from the angle of the prior layer.

As described above, the invention specifically includes an embodiment of a perforating device, such as a gun, which has a longitudinal axis and a horizontal axis and a loading tube having an explosive charge; a first layer slidably, non-fixedly and removably disposed over the loading tube; and at least one outer wire layer wound over the first layer and wherein said outer layer is wire.

In this embodiment, the wire is wound around the first layer at an angle between 1 degree and 60 degrees from the horizontal axis of the perforating device and wherein the wire is wound such that adjacent wire is in a parallel relationship. Alternatively, the outer wire layer can be wire cloth. As wire cloth it is contemplated such that the wire forms into a mesh with a mesh size between 4 wires per inch and 150 wires per inch, and a wire diameter between 0.015 inches and 1. 088 inches.

Preferably, the wire is a metal. An epoxy, binder, adhesive material or laminating agent can be disposed between the wire and the first layer and/or between the wire layers. Alternatively, the wire can be welded to the first layer. A third layer can be disposed between the first layer and the outer wire layer. This third layer can be a perforated sheet comprising a plurality of holes, wherein the holes comprise a diameter between 0.020 inches and 1 inch, and a density of approximately 1 hole per inch to 700 holes per inch. Alternatively, the third layer can be a solid sheet. A fourth layer

can be disposed between the third layer and the outer layer. The fourth layer can be a solid material.

An energy absorbing layer can be disposed between the wire and the first layer. This energy absorbing layer can be a perforated sheet made from steel, stainless steel, aluminum, alloys of steel, alloys of stainless steel, alloys of aluminum and combinations thereof. A preferred density per inch for the perforated sheet is between 1 hole per square inch and 700 holes per square inch wherein the diameter of the holes ranges between 0.020 inches and 1 inch. In this embodiment, the first layer can be a metal with a tensile strength between 36 ksi and 400 ksi, such as a chrome alloy, a nickel alloy, a steel alloy and combinations thereof. Ill yet another embodiment, the first layer and the outer wire layer can be of the same material. In yet another embodiment, the outer diameter of the wire is between 0.015 inches to 0. 188 inches.

Figure 10 illustrates a complex gun 200 formed from multiple layers or tubes radially aligned around a longitudinal axis 115. The gun wall 210 of the gun forms a housing around an annulus 215. The explosive charges, detonator cord, and carrier tube can be placed within this annulus 215.

Recess 225 is formed in the manner described previously. The center axis 119 of recess 225 is has an orientation 910 orthogonal to center axis 115 of the gun.

Figure 1 OA illustrates an embodiment of the invention wherein the outer three layers 21 OD, 210C and 210B of the gun wall 210 contain holes cut prior to assembly of the tubes into a single layer. Although the diameter 288D, 288C and 288B of each hole is different, the center axis 119 of the combined holes 230 are aligned. The inner layer 210A is not cut, and the outer surface 218A of the inner layer forms the bottom 229 of the resulting recess 225. The thickness of each precut layer creates a stepped wall 228 of the recess.

Figure 1 OB illustrates an embodiment wherein the inner tube layer 21 osa is cut through prior to assembly, a next outer layer 210B is not cut at the location, but the next outermost layers 210C and 210D are cut through and the center axis 119 of the precut holes are aligned. This architecture achieves an inner recess 226 within the gun wall 210 aligned with an outer recess 225. This architecture or structure can be readily achieved by this invention. This structure cannot be practically achieved by the prior technology.

Figure 10C illustrates an embodiment readily achieved by the present invention, but that is not practicable by prior technology. It will be appreciated that the shape of the interior recess 226 can be varied in the same manner as the outer recesses may be formed. Accordingly, the recess diameter can be varied within the interior of the gun wall 210.

Figure 10D illustrates a structure that has not been possible prior to the present invention.

The gun wall 210 contains an interior recess or cavity 235. The radial axis 119 of the cavity can be aligned with an explosive charge. At the time of assembly, the cavity may be filled with a eutectic material or other material selected to provide strength at ambient conditions but disperse, vaporize or otherwise degrade with the rapid explosive energy pulse.

FIGI OE illustrates a combination interior recess 236 with an internal cavity235. The interior recess diameter 288A and the internal cavity diameter 288C may be varied as selected by the gun designer.

It will be readily understood by those skilled in the art that the dimensions of each precut hole can be specified. This ability can achieve recesses within multiple layers that, when assembled into the composite gun, the recess walls may possess a desired geometry that may enhance the efficiency of the explosive charge or otherwise impact the directionality of the charge. Further, it will be appreciated that interior recesses may be filled with materials that, when subjected to high temperature, rapidly vaporize or undergo a chemical reaction enhancing o contributing to the original energy pulse.

Figure 10F is a detail of a complex recess 225 comprised of precut holes of varying diameters and aligned in relationship to the same radial axis 119. It will be appreciated that the illustrated recess may comprise part of an internal wall cavity (similar to that depicted in Figure 10D) or a recess on the interior gun wall (similar to that depicted in Figure 10C). It will be appreciated that the recess illustrated in Figure 10F contains stepped walls 228,231B, 231C, and 231D having increasing diameter outward along the axis 119. The outer gun wall is comprised of the surface 231D of the outer layer. The bottom of the recess is formed by the outer surface 218A of inner layer 210A.

Figure 11 illustrates precut holes forming recesses 225 in the outer layer 210D of the multi- layered gun wall (here shown as layers 210D and 210C), the recesses having predefined complex outside wall shapes alternative to the circular shaped precut hole illustrated in the earlier Figures.

The layer thickness 231D and surface 218D and 218C as well as the annulus 215 and longitudinal axis 115 also arr shown. Actual shape design of the recess is unlimited since design is no longer restricted by conventional machining methods. Any combination between layers (such as the example shown in Figures 10A through 10F) and any shape (such as the example shown in Figure 11) can be easily produced by laser cutting, tube assembly or layer lamination, and any required material wrapping. Due to recess wall orientation, an additional advantage of the invention is fewer "off-center"shot problems and better charge performance since the outer tube's recess 225 can

achieve a constant underlying wall thickness 210D regardless of the explosive jet exit point.

In comparison, Figure 12 illustrates the prior art machined scallop 220X having a constant diameter 288X. The bottom of the scallop 229X is flat and of non uniform thickness. It will be appreciated that if the explosive pulse of the detonated charge is not oriented perpendicular to the outside gun wall, the brief explosive jet pulse will encounter a non uniform gun wall, thereby creating a disruption or turbulence in the flow with resulting dissipation of energy. The invention subject of this disclosure results in a uniform wall thickness, thereby minimizing energy dissipation.

Unlike the prior art technology of milling scallops into solid monolithic tube wall, the radial orientation of the recess side wall formed by the present invention can be maintained constant to a point on the longitudinal axis. Referring now to Figures 10A through 10F and Figure 12A, the constant angle 289 and 289 of the recess side wall 228 and 228C is oriented to the centerline 119 achieved by this invention. The cut hole results in a removal of an arc segment 289D and 289C from the circumference of the layer or tube wall 210D and 210C. The angle can be varied by the length of the arc segment 289D and 289C cut relative to the diameter of the tube layer (or radial distance from the center axis of the gun). It will be appreciated by persons skilled in the technology that the angle can facilitate the accuracy or efficiency of the explosive charge. This angle may minimize interference or disruption of the explosive gas jet 251 through the gun toward the casing and strata. The prior art scallops generally have a fixed orientation to the center axis 119 of the scallop. However, this fixed dimension creates a non uniform orientation to the center axis of the gun or the explosive charge positioned within the annulus 215 and proximate to the center axis.

Figure 12A illustrates how the gun wall recess 225 of the present invention may also achieve variable side wall angles 289D. The relationship of the precut hole diameter 288D to the side wall angle and to the center axis 115 of the gun, as well as the annulus 215 is also shown. The curvature of the bottom surface 218C of the recess 225 also is illustrated.

Figure 13A shows a weld seam 268 connecting components 265 to multiple layers of gun wall 210 requiring less machining. This weld can be performed by laser welding, similar to techniques available for precutting of holes 225 within the gun wall 210. The weld seam 268 illustrated in Figure 13B depicts the size achieved by conventional well technology.

In some embodiments, it may be advantageous to weld or mechanically attach machine threaded connection ends to at least one tube layer. Figure 13A and Figure 13B illustrates use of laser welding gun connection fittings for designs utilizing multiple layers. Laser welding involves low-heat input process, thereby allowing completed machined connection end turnings to be welded

directly. Conventional multi-pass welds may require machining after welding to eliminate the effects of distortion.

Other advantages of the invention include more choices of tube supply, especially domestic supplies with far shorter lead times. Lower manufacturing costs are achieved by laser cutting scallops in the outer lamination instead of machining solid, heavy-walled tubes, which is the practice of current technology.

Specific benefits from the construction of guns utilizing multi-layering of differing materials and material costs, reduction of material weight and thickness, decreased dependence upon expensive high strength materials having long lead-time production requirements, and greater flexibility in gun designs including tailoring the properties of the gun wall to accommodate varying field conditions to achieve enhanced performance. In addition, better gun performance is achieved by precut tube scallops having uniform thickness, increased flexibility to create modified scallop walls and shapes, and increased impulse shock absorption by the multiple tube layer interface. Also an inner tube can have higher strength without the adverse effects of brittleness since an outer ductile layer may contain the inner tube.

Since recesses (scallops) can be cut individually into each tube layer before being assembled into a gun tube, many different recess designs are available. One benefit of this recess capability is to produce internal and inner diameter (inner wall) recesses that would be virtually impossible to produce in conventional gun manufacture. It is not the intent of this invention to specifically describe the benefits of all recess designs, but rather to indicate that the advantages will be apparent to persons skilled in the technology of this invention.

While particular embodiments of the invention have been described, it will be understood, of course, that the invention is not limited thereto, and that many obvious modifications and variations can be made, and that such modifications and variations are intended to fall within the scope of the appended claims.