Patent Publication Number: US-7721650-B2

Title: Modular time delay for actuating wellbore devices and methods for using same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application takes priority from U.S. Provisional Patent Application Ser. No. 60/910,031, filed Apr. 4, 2007. 

   BACKGROUND OF THE DISCLOSURE 
   1. Field of the Disclosure 
   The present disclosure relates to devices and methods for selective actuation of wellbore tools. More particularly, the present disclosure is in the field of control devices and methods for selective firing of a gun assembly. 
   2. Description of the Related Art 
   Hydrocarbons, such as oil and gas, are produced from cased wellbores intersecting one or more hydrocarbon reservoirs in a formation. These hydrocarbons flow into the wellbore through perforations in the cased wellbore. Perforations are usually made using a perforating gun loaded with shaped charges. The gun is lowered into the wellbore on electric wireline, slickline, tubing, coiled tubing, or other conveyance device until it is adjacent the hydrocarbon producing formation. Thereafter, a surface signal actuates a firing head associated with the perforating gun, which then detonates the shaped charges. Projectiles or jets formed by the explosion of the shaped charges penetrate the casing to thereby allow formation fluids to flow through the perforations and into a production string. 
   In many situations, a perforation activity may utilize an assembly of several guns. In such situations, it may be advantageous to have the ability to determine whether all the guns in a gun assembly have fired. One such situation is where two or more guns of a perforating gun assembly include firing heads that are configured to activate at the same applied pressure. Variances in operating equipment and/or design tolerances may cause the firing heads to respond to slightly different applied pressures. Also, the firing heads may be configured to activate at different applied pressures. In either case, it may be advantageous to be able to fire the guns in a manner that ensures all firing heads have sufficient time to activate upon application of pressure. Another situation is where the firing sequence does not permit a clear detection of the firing of each gun in the assembly. If the non-firing of a gun can be easily determined, a firing sequence can be retrieved to cause a firing of any gun that did not fire. Moreover, if less than all the guns have fired, certain procedures may be used at the surface when retrieving the guns to prevent an unintended detonation of any gun that has not fired. 
   The conventional firing systems for various reasons, such as capacity, reliability, cost, and complexity, have proven inadequate for these and other applications. The present disclosure addresses these and other drawbacks of the prior art. 
   SUMMARY OF THE DISCLOSURE 
   In aspects, the present disclosure provides an apparatus for controlling an energy train generated in a wellbore. The energy train may be associated with the firing of a perforating gun or the operation of some other wellbore tool. The apparatus may include a firing head, a detonator cord associated with the firing head, and a plurality of serially aligned modules. One of the modules may be energetically coupled to the detonator cord. Moreover, each module may include an enclosure having a first open end and a second open end, a first portion of a high order detonation material positioned at the first open end, a second portion of the high order detonation material positioned at the second open end, and a low order detonation material interposed between the first portion and the second portion. In arrangements, at least one of the plurality of modules is configured such that the detonation of the first portion detonates the low order detonation material and the detonation of the low order detonation material detonates the second portion. In aspects, a booster charge may be energetically coupled to the detonator cord. Also, a transition detonator may energetically couple the detonator cord to at least one of the plurality of modules. The transition detonator may be formed at least partially of a high order detonation material. In embodiments, the apparatus may have a housing receiving the detonator cord and the plurality of modules. The modules may be configured to be slid into the housing. In arrangements, the first portion of at least one module of the plurality of modules may be energetically coupled to one of: (a) a first portion of an adjacent module, and (b) a second portion of the adjacent module. 
   In aspects, the present disclosure provides a method for controlling an energy train generated in a wellbore. The method may include serially aligning a plurality of modules along the path of the energy train, and detonating at least one of the plurality of modules by detonating a detonator cord. Each module may include an enclosure having a first open end and a second open end, a first portion of a high order detonation material positioned at the first open end, a second portion of the high order detonation material positioned at the second open end, and a low order detonation material interposed between the first portion and the second portion. In arrangements, the method may include configuring at least one of the plurality of modules such that the detonation of the first portion detonates the low order detonation material and the detonation of the low order detonation material detonates the second portion. In variants, the method may also include detonating the detonator cord by using a booster charge. In arrangements, the method may further include energetically coupling the detonator cord to at least one of the plurality of modules using a transition detonator, wherein the transition detonator is formed at least partially of a high order detonation material. 
   In aspects, the present disclosure provides an apparatus for controlling an energy train used to activate a wellbore tool. The apparatus may include a housing, a module slidably received into the housing, and a firing head positioned external to the housing. The module may include a support member having a first open end and a second open end, a first energetic material inside the support member, the first energetic material being configured to cause a low order detonation; and a second energetic material in the support member, the second energetic material being configured to cause a high order detonation. In embodiments, the apparatus may include at least one module wherein the first energetic material is disposed between a first portion and a second portion of the second energetic material. In aspects, the first portion may detonate the first energetic material and the first energetic material may detonate the second portion. In variants, the first energetic material may have a burn rate on the order of seconds and the second energetic material may have a burn rate on the order of microseconds. In aspects, the apparatus may include a plurality of modules being positioned in the housing, each of the plurality of modules having a predetermined amount of the first energetic material. In aspects, each of the plurality of modules may include a portion of the second energetic material. 
   It should be understood that examples of the more illustrative features of the disclosure have been summarized rather broadly in order that detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For detailed understanding of the present disclosure, references should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals and wherein: 
       FIG. 1  schematically illustrates a perforating gun assembly made in accordance with one embodiment of the present disclosure; and 
       FIG. 2  schematically illustrates one embodiment of a time delay made in accordance with the present disclosure. 
   

   DESCRIPTION OF THE DISCLOSURE 
   The present disclosure relates to devices and methods for actuating downhole tools. The present disclosure is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the present disclosure with the understanding that the present disclosure is to be considered an exemplification of the principles of the disclosure, and is not intended to limit the disclosure to that illustrated and described herein. 
   Referring initially to  FIG. 1 , there is shown a well construction and/or hydrocarbon production facility  30  positioned over subterranean formations of interest  32 ,  34 . The facility  30  can be a land-based or offshore rig adapted to drill, complete, or service a wellbore  38 . The facility  30  can include known equipment and structures such as a platform  40  at the earth&#39;s surface  42 , a wellhead  44 , and casing  46 . A work string  48  suspended within the well bore  38  is used to convey tooling into and out of the wellbore  38 . The work string  48  can include coiled tubing, drill pipe, wire line, slick line, or any other known conveyance means. The work string  48  can include telemetry lines or other signal/power transmission mediums that establish one-way or two-way telemetric communication from the surface to one or more tools connected to an end of the work string  48 . A suitable telemetry system (not shown) can be known types as mud pulse, pressure pulses, electrical signals, acoustic, or other suitable systems. A surface control unit (e.g., a power source and/or firing panel)  54  can be used to monitor and/or operate tooling connected to the work string  48 . The controller  54  can include a monitoring device for measuring and/or recording parameters of interest relating to the firing sequence. The monitoring device can be an acoustical tool coupled to the work string  48 , a pressure sensor (not shown) in communication with the wellbore fluid, or other suitable device. 
   The teachings of the present disclosure may be applied to any wellbore tool wherein pyrotechnics are used in connection with activation of that tool. Merely for ease of explanation, embodiments of the present disclosure will be discussed in the context of a perforating gun assembly  60  that is coupled to an end of the work string  48 . An exemplary gun assembly  60  includes a plurality of guns or gun sets  62   a - b , each of which includes perforating shaped charges  64   a - b , firing heads  66   a - b  and detonators  68  a-b. The guns  62   a - b  are connected to one another by a connector  70 . While two guns are shown, it should be understood that the gun assembly  60  can utilize greater or fewer guns. In an exemplary deployment, an operator initiates a firing sequence for the gun assembly  60  by transmitting an activation signal to the firing heads  66   a - b . The activation signal may be an applied pressure, an electrical signal or an impact caused by a device such as a “drop bar.” Upon receiving the activation signal, the firing heads  66 - a - b  releases or generates an “energy train” that activates the detonators  68   a - b . By energy train, it is generally meant a shock wave or thermal energy that travels along a predetermined path. 
   In embodiments, a modular time delay device  100  is positioned between the firing heads  66   a - b  and their respective detonators  68   a - b  to adjust or control the time needed for the energy train to travel between each firing head  66   a - b  and its respective detonator  68   a - b . By adjustable or controllable, it is meant that the modular time delay device  100  can be configured to increase or decrease the time between the transmission of an activation signal and the eventual firing of the guns  60   a - b . In one embodiment, the modular time delay device  100  includes a combination of energetic materials, each of which exhibit different burn characteristics, e.g., the type or rate of energy released by that material. By appropriately configuring the chemistry, volume, and positioning of these energetic materials, a desired or predetermined time delay can be in the firing sequence. Generally, the energetic materials can include materials such as RDX, HMX that provides a high order detonation and a second energetic material that provides a low order detonation. The burn rate of an energetic material exhibiting a high order detonation, or high order detonation material, is generally viewed as instantaneous, e.g., on the order of microseconds or milliseconds. The burn rate of an energetic material exhibiting a low order detonation, or low order detonation material, may be on the order of seconds. In some conventions, the high order detonation is referred to simply as a detonation and the low order detonation is referred to as a deflagration. 
   Referring now to  FIG. 2 , there is shown a modular time delay device  100  made in accordance with one embodiment of the present disclosure. The modular time delay device  100  has a first end  101  that receives an energy input and a second end  102  that provides an energy output. In one arrangement, the modular time delay device  100  has a housing  104 , a detonator cord  106 , a transition detonator  108  and a plurality of delay modules  110 . The transition detonator  108  and the detonator cord  106 , which is connected to a booster charge  103 , cooperate to produce a high order detonation at the second end  102 . The delay modules  110  control the time needed for an energy train to travel between the first end  101  and the second end  102 . Each delay module  110  provides a preset amount of time delay. By “delay,” it is generally meant the time period needed for an energy train to traverse or cross the module  110 . For instance, an exemplary module  110  can provide ten second time delay, a thirty five second time delay, a sixty seconds of time delay, etc. Thus, where a module  110  has a sixty second time delay, the housing  104  may be fitted with no modules  110  for no delay, with one module  110  for a sixty seconds time delay, two modules  110  for a one hundred twenty seconds time delay, three modules  110  for a one hundred eighty seconds time delay, etc. In some embodiments, each module  110  may have the same predetermined time delay. In other embodiments, the modules  110  can be configured to provide different amounts of predetermined time delays; e.g., one module may have a ten second delay and another module may have a forty five second delay. 
   The modules  110  may include one or more energetic materials that exhibit a predetermined burn rate suitable for providing a desired time delay. In the arrangement shown, the module  110  uses a first energetic material  112  that exhibits a low order detonation and a second material  114  that exhibits a high order detonation. Suitable materials for the first energetic material  112  include materials that release energy over a period of seconds rather than relatively instantaneously. The material make-up, density, quantity and positioning of the first energetic material  112  may be adjusted as needed to provide a predetermined delay period. The second energetic material  114  is formulated to energetically couple the modules  110  to one another, to energetically couple the module  110  to the transition detonator  108 , and to energetically couple the energy input at the end  101  to the module  110 . Because each of these components is separate, the interface between each of these components creates a discontinuity that is to be crossed by the energy train. The second energetic material  114  functions much like a booster charge that ensures an efficient energy transfer across these discontinuities. It should be appreciated that in certain embodiments the module  110  may include only the first energetic material  112 . That is, in applications where an energy train is expected to effectively cross such discontinuities, the second energetic material  114  may be omitted. The energetic materials  112  and  114  can be disposed in a support member such as a casing  116 . The casing  116  may be a sheath or tube having open ends. In one arrangement, the second energetic materials  114  are positioned at the open ends and the first energetic material  112  is interposed between the second energetic materials  112 . 
   Thus, the modular time delay device  100  may be described as having in a serial fashion, a high order detonation material energetically coupled to a plurality of modules, each of which include a low order detonation material interposed between high order detonation materials. 
   Referring now to  FIGS. 1 and 2 , the detonator cord  106  and the transition detonator  108  cooperate to convert the energy released from the modules  110  into a high order detonation suitable for initiating the detonators  68   a - b . The transition detonator  108  converts the detonation of the modules  110  into a form suitable for properly detonating the detonator cord  106 . The detonator cord  106  in turn undergoes a high order detonation that is transmitted the detonators  68   a - b . The detonator cord  106  and transition detonator  108  may be formed of known explosives suitable for high order detonations. As is known, detonator cords may be cut to suit a particular length. Thus, the detonator cord  106  may be sized as needed to accommodate the number of modules  110  used. 
   It should be appreciated that each modular time delay device  100  used in the perforating gun assembly  60  can be configured at the surface to provide a predetermined time delay by selecting an appropriate number of modules  110 . One method of implementing a desired time delay includes selecting a time delay to be inserted into a firing sequence of a particular gun, e.g., gun  60   a  or  60   b . Next, an operator determines the number of modules  110  needed to provide the selected time delay. The modules  110  are thereafter inserted into the housing  104 . The modules  110  may be configured to slide into the housing  104  and arrange themselves in an end-to-end serial fashion. As noted above, the detonator cord  106  may be cut to the proper size to span the distance between the transition detonator  108  and the output end  102 . The modular time delay device  100  can then be inserted into the perforating gun  60 . 
   During deployment, the gun assembly  60  is positioned adjacent the zones to be perforated, a firing signal is transmitted from the surface to the gun  60 . This firing signal can be caused by increasing the pressure of the fluid in the wellbore via suitable pumps (not shown) or other suitable methods. The firing signal will activate the firing heads  66   a - b . Upon receiving the firing signal, the firing heads  66   a - b  initiates a high order detonation that is applied to the first end  101  of each modular time delay device  100 . This high order detonation is initially applied to the module  110  closest to the first end  101 . Each module  110  in successions burns a predetermined amount of time and eventually ignites the transition detonator  108 . The transition detonator  108  detonates the detonator cord  106 , which then detonates the detonators  68   a - b . Each gun  60   a - b  may utilize the same delay period or a different delay period. As the gun assembly  60  fires, each gun  60   a - b  releases energy such as acoustical waves or pressure waves. By measuring these waves or pulses, an operator can determine the number of guns  60   a - b  that have fired. It should also be appreciated that the modular time delays  100  provide time delays between sequential firing that can facilitate detection of the individual firing events. Thus, for example, if two distinct firings are measured, then personnel at the surface can be reasonably assured that all guns  60   a - b  have fired. If only one distinct firing is measured, then personnel at the surface are given an indication that a gun may not have fired. 
   From the above, it should be appreciated that what has been described includes an apparatus for controlling an energy train generated in a wellbore. The apparatus may include a firing head, a detonator cord associated with the firing head, and a plurality of serially aligned modules. One of the modules may be energetically coupled to the detonator cord. Moreover, each module may include an enclosure having a first open end and a second open end. A first portion of a high order detonation material may be positioned at the first open end and a second portion of the high order detonation material positioned at the second open end. A low order detonation material may be interposed between the first portion and the second portion. In arrangements, at least one of the modules is configured such that the detonation of the first portion detonates the low order detonation material and the detonation of the low order detonation material detonates the second portion. In aspects, a booster charge may be energetically coupled to the detonator cord. Also, a transition detonator may energetically couple the detonator cord to at least one of the modules. The transition detonator may be formed at least partially of a high order detonation material. In embodiments, the apparatus may have a housing receiving the detonator cord and the plurality of modules. The modules may be configured to be slid into the housing. In arrangements, the first portion of at least one module of the plurality of modules may be energetically coupled to one of: (a) a first portion of an adjacent module, and (b) a second portion of the adjacent module. 
   From the above, it should be appreciated that what has also been described includes a method for controlling an energy train generated in a wellbore. The method may include serially aligning the above-described modules along the path of the energy train, and detonating at least one of the plurality of modules by detonating a detonator cord. 
   From the above, it should be appreciated that what has also been described includes an apparatus for controlling an energy train used to activate a wellbore tool. The apparatus may include a housing, a module slidably received into the housing, and a firing head positioned external to the housing. The module may include a support member having a first open end and a second open end. The support member may be a sheath, a sleeve, a tube or other suitable structure. A first energetic material positioned inside the support member may be formulated or configured to cause a low order detonation. A second energetic material positioned in the support member may be configured to cause a high order detonation. In embodiments, the apparatus may include at least one module wherein the first energetic material is disposed between a first portion and a second portion of the second energetic material. In aspects, the first portion may detonate the first energetic material and the first energetic material may detonate the second portion. In variants, the first energetic material may have a burn rate on the order of seconds and the second energetic material may have a burn rate on the order of microseconds. In aspects, the apparatus may include a plurality of modules being positioned in the housing, each of the plurality of modules having a predetermined amount of the first energetic material. In aspects, each of the plurality of modules may include a portion of the second energetic material. 
   While the above-described embodiments have been discussed in connection with a perforating gun assembly, it should be appreciated that the present teachings can readily be applied to any wellbore tool using pyrotechnics in its activation process. For example, devices such as pipe cutters and setting tools may be configured to utilize explosive energy to perform a specified task. Embodiments of the present invention can be readily used to provide a controlled delay in the firing sequence for such devices. The foregoing description is directed to particular embodiments of the present disclosure for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the disclosure. It is intended that the following claims be interpreted to embrace all such modifications and changes.