Select fire perforating cartridge system

Abstract

A method and apparatus for using a tandem sub between two perforating guns where an EB fire pressure switch arms a detonator after the detonation of a first perforating gun and then a subsequent electrical signal can then detonate the second perforating gun.

Claims

1. A method of perforating a well comprising: loading a first perforating gun with perforating charges and a first detonating cord; loading a second perforating gun with perforating charges and the first detonating cord; inserting a cartridge containing a detonator into a tandem sub, wherein the detonator is at least partially disposed within the tandem sub; inserting a detonation transfer end fitting into first perforating gun; inserting the first detonating cord into the detonation transfer end fitting; coupling the first perforating gun to a first end of the tandem sub; coupling the second perforating gun to the second end of the tandem sub; assembling the first perforating gun, the tandem sub, and the second perforating gun in a tool string; conveying the tool string into the well; detonating the second perforating gun with an electrical signal, wherein the detonation of the second perforating gun arms the cartridge within the tandem sub; and detonating the first perforating gun with an electrical signal using the armed cartridge.

2. The method of claim 1 wherein the cartridge has at least one electrical contact proximate each end.

3. The method of claim 2 wherein at least one of the electrical contacts of the cartridge is resiliently biased closed.

4. The method of claim 3 wherein at least one of the electrical contacts of the cartridge is a compression spring.

5. The method of claim 2 wherein the cartridge also holds a switch electrically connected to the detonator.

6. The method of claim 1 further comprising: conveying the first perforating gun to a well site after loading the first perforating gun with perforating charges and detonating cord.

7. The method of claim 1 further comprising: conveying the first perforating gun to a well site after inserting the cartridge containing the detonator into the perforating gun.

8. The method of claim 1 further comprising: connecting the first perforating gun to a second perforating gun by threading the body of the first perforating gun directly into the body of the second perforating gun.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings in which reference numbers designate like or similar elements throughout the several figures of the drawing. Briefly:

(2) FIG. 1 is a side cross section view of a portion of a perforating gun tool string.

(3) FIG. 2 is a side cross section view of a tandem sub coupled to a perforating gun on either end.

(4) FIG. 3 is a side cross section view of a cartridge style switch and detonator assembly.

(5) FIG. 4 is a top cross section view of a cartridge style switch and detonator assembly.

DETAILED DESCRIPTION OF EXAMPLES OF THE INVENTION

(6) In the following description, certain terms have been used for brevity, clarity, and examples. No unnecessary limitations are to be implied therefrom and such terms are used for descriptive purposes only and are intended to be broadly construed. The different apparatus, systems and method steps described herein may be used alone or in combination with other apparatus, systems and method steps. It is to be expected that various equivalents, alternatives, and modifications are possible within the scope of the appended claims. Directional and orientation terms such as upper, lower, top, and bottom are used in this description for convenience and clarity in describing the features of components. However, those terms are not inherently associated with terrestrial concepts of up and down or top and bottom as the described components might be used in a well.

(7) FIG. 1 depicts an example embodiment of a portion of a gun string 100. The top assembly 101 is uphole of and coupled to the first perforating gun 103. The first perforating gun 103 is uphole of and coupled to the first tandem sub 102. The tandem sub 102 is uphole of and coupled to the second perforating gun 115. The second perforating gun 115 is uphole of and coupled to the second tandem sub 118. The charge tube 104 of the first perforating gun 103 is held in place by a top end fitting 105 and a detonation transfer end fitting 110. The insulation cap 106 electrically insulates the end fitting 105 from the gun body 119 of the first perforating gun 103. The insulation cap 111 electrically insulates the end fitting 110 from the gun body 119 of the first perforating gun 103. A detonation cord 114 is routed from the top end fitting 105 to the detonation transfer end fitting 110 around the charge tube 104 in such a way as to couple to the ends of each shaped charge (not shown) that is inserted into the charge tube 104. The second perforating gun 115 also has a detonating cord 141 routed around the charge tube 117 and routed from end to end of the charge tube 117. The second perforating gun 115 is has the charge tube 115 electrically isolated from the gun body 120 via end fittings 135 and 145.

(8) For electrical communication, the gun body of each perforating gun acts as a ground, while the hot wire is the charge tube, which is electrically isolated from the gun body using insulation caps at either end of the charge tube. The electrical connection from the top sub 101 to the charge tube 104 of the first perforating gun 103 is by way of a feed thru contact pin 107 slideably engaged with a contact retainer 108 preloaded with a compression spring 109. The tandem sub 102 provides an electrical pathway from the charge tube 104 as shown in FIG. 2 through the detonation transfer end fitting 110, through the cartridge assembly 112 that is electrically isolated from the body of the tandem sub 102, and through feed thru contact pin 137, which is slideably engaged with contact retainer 138, the hot path makes contact with the end fitting 135, which is electrically coupled to the charge tube 117, and contact is maintained via spring 139.

(9) An example of the perforating gun firing sequence may include arming the tandem sub 118 via perforating gun located downhole of the tandem sub 118. The shock of the explosion of a perforating gun will arm the detonator 140. An electrical signal sent via the hot connection will then activate detonator 140, thus setting off detonating cord 141 along with any shaped charges located within charge tube 117. The shock and gas expansion associated with the detonation of perforating gun 115 will move the feed thru contact pin 137, thus arming detonator 121 by putting it in electrical contact with the hot and ground sides of the tandem sub 102. An electrical signal is then sent from the surface to detonate the detonating cord 114 via detonator 121. The detonation of the detonating cord 114 will cause all of the shaped charges installed in the charge tube 104 to detonate as well.

(10) An example cartridge assembly 200 is shown in FIG. 3, which is a side view of the assembly. A top case 211 is coupled to a bottom case 212. An EB switch housing 202 is located within the cartridge assembly 200 and a bulkhead is coupled, in this example threaded, into the EB switch housing 202. A piston assembly 203 is located within the bulkhead 201 and may be composed of PEEK or some other non-conductive material. A firing pin assembly 205 is spring loaded and located within the brass receptacle assembly 204. A dart wire connection spring 206 is coupled to the firing pin assembly 205. Insulation 209 and 210 provide electrical insulation between the firing pin assembly 205 and the top and bottom cases 211 and 212, respectively. Switch wire 208 is connected between the detonator 216 and the dart wire connection spring 206. Diode assembly 207 provides the one-way electrical contact between the EB switch housing with the ground when the switch is armed, however the circuit is installed in this example as open. Metal end cap 213, in conjunction with contact spring 214, is adapted to couple to a detonation transfer end fitting. Detonation sleeve 215 electrically isolates the detonator 216 from the hot side of the circuit.

(11) Another view of the example embodiment depicts a top cross-sectional view of cartridge assembly 200 in FIG. 4. The bulkhead 201 contains the piston assembly 203 and is coupled to the EB switch housing 202, which contains the EB switch 222. Feed thru wire and washer 217 connects to feed thru wire 221. The detonator 216 has a first lead wire 226 and a second lead wire 223. Wire 224 coming off of diode assembly 207 is connected to the first lead wire 226. Ground screw 218 and ground lug 219 provide the grounding for ground wire 220 which is attached to the second lead wire 223 from the detonator 216. Diode 225 designates the polarity of the switch, either positive or negative. The feed thru wire 221 is connected to the switch wire 208.

(12) Although the invention has been described in terms of embodiments which are set forth in detail, it should be understood that this is by illustration only and that the invention is not necessarily limited thereto. For example, terms such as upper and lower or top and bottom can be substituted with uphole and downhole, respectfully. Top and bottom could be left and right, respectively. Uphole and downhole could be shown in figures as left and right, respectively, or top and bottom, respectively. Generally downhole tools initially enter the borehole in a vertical orientation, but since some boreholes end up horizontal, the orientation of the tool may change. In that case downhole, lower, or bottom is generally a component in the tool string that enters the borehole before a component referred to as uphole, upper, or top, relatively speaking. The first housing and second housing may be top housing and bottom housing, respectfully. Terms like wellbore, borehole, well, bore, oil well, and other alternatives may be used synonymously. The alternative embodiments and operating techniques will become apparent to those of ordinary skill in the art in view of the present disclosure. Accordingly, modifications of the invention are contemplated which may be made without departing from the spirit of the claimed invention.