Patent Publication Number: US-9422796-B2

Title: Cased hole chemical perforator

Description:
BACKGROUND 
     In drilling oil and gas wells, after a productive hydrocarbon zone has been reached it is often necessary to run a well casing into the wellbore. The casing is then anchored into place by injecting a volume of cement into the annulus between the wellbore wall and the casing. The cement anchors the casing into place and seals the hydrocarbon zone to prevent the migration of fluids from one zone to another through the annular space. Unfortunately, the casing blocks the flow of formation fluid, in particular hydrocarbons, into the interior of the casing. 
     In order to produce the hydrocarbons from a wellbore, it is necessary to provide a series of lateral perforations through the casing and any adjacent cement. In many instance a perforation gun is used to perforate the casing and the adjacent cement. 
     A perforation gun may use a series of shaped charges to perforate the casing. The perforation gun is lowered into the vicinity of the casing that is desired to be perforated and, upon actuation of the perforation gun from the surface, the shaped charge is fired, penetrating the casing and adjacent cement. After the casing has been perforated approximately adjacent to a hydrocarbon producing formation the formation is typically fractured or otherwise treated to enhance the production of hydrocarbons from the zone. 
     Presently it is becoming more common to drill through multiple zones with a single wellbore and due to the structure of the formation zones long horizontal sections are increasingly becoming the typical method of drilling a well. As horizontal completions become increasingly common, it is desirable, due to the high cost of standby time for the fracturing and well treating equipment, to minimize the time required to set up and complete the treatment or fracturing of one hydrocarbon producing zone and move to the next hydrocarbon producing zone in the same wellbore. 
     One method of decreasing the high cost of standby time for the fracturing and well treating equipment, that has been developed is to incorporate sliding sleeves with ball valves into the casing string and then to cement the tubular in place including the sliding sleeves. With sliding sleeves cemented into place a perforating gun is not necessary as ports are provided in the sliding sleeves. When it becomes necessary to open a sliding sleeve a ball or other plug is circulated downhole to open the sleeve allowing the operator to fracture or treat the desired hydrocarbon producing zone. 
     The drawback to such a system is that the decision to complete the well with sliding sleeves must be made relatively early, a complete system must be purchased, and the complete system should be precisely incorporated into the tubular assembly to correspond with each hydrocarbon producing zone. 
     SUMMARY 
     One embodiment of the present allows the operator to decide how to complete the well even after the well has been cased. By employing open-hole sliding sleeve technology. Previously the use of sliding sleeve technology has not been possible because there has not been a means to perforate the casing adjacent to the ports in the sliding sleeve. However, by using a chemical cutter such as bromine trifluoride with a steel wool catalyst, a self-contained chemical-filled cartridge may be positioned within the sliding sleeve at the preferred well location. To activate the sleeve and its associated chemical cutter a ball may be circulated to move the chemical perforator radially outward against the casing. Additional pressure ruptures the cartridge, forcing the chemical to contact the steel wool and start the oxidizing reaction. Continued pressure drives this reaction against the casing in a focused jet to create a through-hole perforation in the casing. One the sliding sleeve is open and the casing is perforated the hydrocarbon producing formation may then be treated. The steel wool catalyst may be particles of iron. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a cased wellbore with a tubular assembly. 
         FIG. 2  depicts a single perforating sleeve located in casing. 
         FIG. 3  depicts a perforating assembly in its initial state being run into the casing. 
         FIG. 4  depicts the perforation assembly as the ball strikes the perforation cartridge but before actuating the perforation cartridge. 
         FIG. 5  depicts the perforation assembly just after the ball has impacted the perforation cartridge. 
         FIG. 6  depicts the perforation assembly after the ball has moved the perforation cartridge radially outwards against the casing. 
         FIG. 7  depicts the perforation assembly as continued pressure from the surface forces the chemical penetrator and the catalyst against the casing. 
         FIG. 8  depicts production from the hydrocarbon producing formation through the port cut in the casing by the penetrator assembly. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
     The description that follows includes exemplary apparatus, methods, techniques, and instruction sequences that embody techniques of the inventive subject matter. However, it is understood that the described embodiments may be practiced without these specific details. 
       FIG. 1  depicts a wellbore  10  in which casing  12  where cement has been pumped through the casing  12  from the surface  20 . The cement is forced out of the bottom of the casing and then flows back up towards the surface  20  through the annulus  22  between the casing and the wellbore  10 . Once the annulus  22  is filled with cement the cement is allowed to set anchoring the casing  12  into place in the wellbore  10 . 
     The operator may then run a tubular assembly  30  into the casing  12 . The tubular assembly is assembled on the surface  20  and run into the casing by rig  40  so that each desired perforating sleeve  24  may be adjacent to a portion of a hydrocarbon producing formation  26 . Once the perforating sleeves  24  are properly located the perforating sleeves  24  may be actuated. Many operators may choose to activate each perforating sleeve  24  independently such as by using differently sized balls to actuate each perforating sleeve  24  or by using any of the methods whereby a single ball may actuate a particular perforating sleeve  24 . In certain instances the operator may choose to actuate all of the perforating sleeves  24  with a single ball. It should be understood that while an actuating ball is referred to throughout, an actuating dart, plug or any other device that may actuate the perforating sleeve  24  may be used. 
       FIG. 2  depicts a single perforating sleeve  24  located in casing  12 . The perforating sleeve  24  is has a perforating assembly  50  located in the housing  52 . A separate inner sleeve  54  may be incorporated to fix the perforating assembly&#39;s 50 components in place. In some instances the inner sleeve  54  may not be used and the perforating assembly may be fixed directly to the housing  52  by threads, screws, welding, brazing, press fit into position or any other means known in the industry. In many instances the inner sleeve  54  may not be fixed into position but may be longitudinally movable to close or open the port through the housing and casing that is created by the operation of the perforating assembly  50 . A ball  56  is sized so that the ball  56  will actuate the perforating assembly  50  by a portion of the perforating assembly  50  radially outward as the ball  56  passes the perforating assembly. The perforating sleeve  24  has a fixed ball seat  58  to catch the ball  56  after the perforating assembly  50  has been actuated. After the perforating assembly  50  creates a port in the casing  12  and the perforating sleeve  24  pressure from the surface  20  may be applied to the ball  56  on seat  58  to fracture or otherwise treat the adjacent hydrocarbon zone  26 . In certain perforating sleeves the seat  58  may not be rigidly fixed to the perforating sleeve  24 . 
       FIG. 3  depicts a perforating assembly  50  in its initial state as it is being run into the casing  12 . The perforating assembly  50  is depicted as being screwed into housing  52  via threads  60  on the perforating assembly base  62  and corresponding threads  64  on the housing  50 . The perforation cartridge  68  is held in its set position by shear pins  70 . While shear pins  70  are depicted any known means of retaining the perforation cartridge  68  in its set position such as shear screws, adhesives, or friction could be used. The shear pins  70  hold the perforation cartridge  68  such that a portion of the perforation cartridge  68  protrudes radially inward into the interior bore of the perforation sleeve  24 . The portion of the perforation cartridge  68  that protrudes into the interior bore of the perforation sleeve  24  may have a sloping profile  76  so that when a ball, such as ball  56 , contacts the perforation cartridge the force that the ball  56  can apply to the perforation cartridge  68  may be magnified. The perforation cartridge  68  is located in a bore  72  in the inner sleeve  54 . The shoulders  74  of the bore  72  may serve as a guide so that when ball  56  strikes the sloping profile  76  the perforation cartridge  68  will be driven radially outward with little longitudinal offset. 
     The perforation cartridge  68  also has a penetrator assembly  86 . The perforation cartridge  68  may have a bore  88  through the perforation cartridge  68  to retain the penetrator assembly  86 . The bore  88  may have a protective membrane  82  located on the bore opening furthest from the centerline of the penetrator sleeve  24 . The protective membrane may be an elastomer, a metal, or any material that will retain and protect the catalyst  84  in the bore  88 . In certain instances no protective membrane  82  may be required. The catalyst is useful to increase the effects of the chemical penetrator  94  and depending upon the chemical penetrator  94  is typically steel wool. High pressure rupture disks  92  are located at the innermost end of the bore  88  and between the catalyst and the chemical penetrator  94 . The chemical penetrator is retained in the bore  88  by the high pressure rupture disks  92 . Typically the chemical penetrator  94  is bromine trifluoride although any chemical that may erode the casing  12  may be used. 
       FIG. 4  depicts the perforation assembly  50  and a portion of the surrounding perforation sleeve  24 , casing  12 , cement  80 , and hydrocarbon producing formation  26  as the ball  56  strikes the sloping profile  76  of the perforation cartridge  68  but before the perforation cartridge  68  can move. 
       FIG. 5  depicts the perforation assembly  50  just after the ball  56  has impacted the perforation cartridge  68 . Pressure is applied from the surface  20  through the rig  40  to force the ball  56  to shear the shear pins  70  and move the perforation cartridge  68  radially outward. The perforation cartridge  68  has moved radially outward in the perforating assembly base  62  so that sloping profile  76  is fully recessed into the bore in the inner sleeve  52  and the furthest radially outward portion of the perforation cartridge  68  contacts the casing  12 . After the ball  56  has forced the perforation cartridge  68  into the recess  72  the ball  56  continues down the tubular assembly until it seats on seat  58 . 
       FIG. 6  depicts the perforation assembly  50  shortly after the ball  56  has moved the perforation cartridge  68  radially outwards against the casing  12 . Continued pressure from the surface  20  should cause both of the high pressure rupture disks  92  and the protective membrane  82  to break. Once the high pressure rupture disks  92  break the chemical penetrator  94  and the catalyst  84  to come into contact with one another. The pressure from the surface  20  will also cause the chemical penetrator  94  and the catalyst  84  to move in the direction of arrow  100  allowing the chemical penetrator  94  to interact with the catalyst  84 . 
       FIG. 7  depicts the perforation assembly  50  as continued pressure from the surface  20  continues to force the chemical penetrator  94  and the catalyst  84  mixture in the direction of arrow  112  against the casing  12  where it penetrates through the casing and at least to the cement  80 . Further pressure from surface  20  in addition to the chemical penetrator  94  and the catalyst  84  mixture will penetrate the cement  80 . The hydrocarbon producing formation  26  may then be treated so that production may be optimized. 
       FIG. 8  depicts production from the hydrocarbon producing formation  26  through the cement  80  and through the port  110  in the casing  12  that was cut by the penetrator assembly  50 . The direction of production is shown by arrows  114 . 
     While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
     Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.