Abstract:
A method and apparatus for removing abandoned or obsolete fixed platforms in a marine environment is provided. The apparatus includes a delivery system having an expandable frame carrying explosive charges. The frame includes curved sections which are adjustably moved relative to one another for fitting the explosive charge members to the inside bore of a vertical leg section of the rig. A shaped charge arrangement focuses the explosive charges at a desired location on the rig leg so that when the explosive charge detonates, the rig is cut with minimal invasion of the surrounding environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation-in-part of U.S. patent application Ser. No. 09/177,257, filed Oct. 22, 1998 and now U.S. Pat. No. 6,131,517, which is incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     REFERENCE TO A “MICROFICHE APPENDIX” 
     Not applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to improved method and apparatus for removing abandoned marine platform jackets and like fixed platforms from the seabed and for the remote placement of explosive charges using an improved delivery system. Even more particularly, the present invention relates to improved method and apparatus for removing jackets and like fixed platforms from the seabed by employing a specially configured delivery system that carries explosive charges that are to be placed inside of the hollow legs (or like tubular member) of an abandoned jacket or fixed platform, (e.g. oil well, oil production platform or the like). 
     2. General Background of the Invention 
     In the offshore oil and gas well drilling industry, there are a large number of fixed platforms that have been installed over the years in the fragile marine environment. These platforms typically involve the use of a structural steel frame or “jacket” that is comprised of a plurality of hollow tubular members, many of which are vertically oriented. In order to anchor the jacket to the seabed during installation, elongated hollow piling members are place through the vertical leg portions of the jacket and thrust downwardly into the seabed. 
     After a number of years of use, these offshore oil and gas well drilling platforms and production platforms can become obsolete. Under relevant laws, they are necessarily removed since they are a hazard to navigation. One of the methods of removing offshore oil and gas well drilling platforms and production platforms requires that the legs of the jacket or platform be severed below (e.g. 15 feet) the mud line. The remaining portion above the cut can be lifted from the seabed using a crane. The jacket or platform can be placed on a barge for later disposal at a suitable scrap yard or like site. 
     One of the problems that has faced the offshore oil and gas well drilling industry is the removal of obsolete or abandoned platforms without adversely effecting the surrounding marine environment. Typically, offshore marine environments are very delicate and should necessarily be minimally impacted by a method that is used to remove a fixed platform or production platform. 
     Another problem that faces a salvage company is excess expense and danger if a diver must cut the legs one at a time with an underwater cutting torch. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an improved delivery system for placing explosives that enable removal of an offshore fixed platform from the marine environment. In such a situation, the platform typically has a plurality of legs that extend below the seabed, each leg or like tubular member being hollow and having a leg wall with an inside surface. 
     The method of the present invention first places a delivery apparatus within a leg at a selected locale, eg. the seabed area. The frame includes curved portions that tracks the curvature of the platform leg at an area to be severed. 
     Explosive charges are carried by the frame and positioned against the inside wall surface of the leg at a desired location. 
     The wall of the leg is then severed by detonating the explosive charge that has been supported with the frame. 
     These steps are repeated until all of the legs have been severed. The platform is then lifted from the seabed so that it can be placed on a transport barge for disposal at a fabrication yard, salvage yard, or scrap yard. 
     The present invention provides an improved delivery system for placing explosive charges in a pipe to be severed. The delivery system thus provides a method of placing an adjustable frame within the leg or pipe to be salvaged at the seabed area, the frame having multiple, curved charge carriers and being movable between retracted and expanded positions. 
     As part of the method, the frame and its explosive charges are positioned next to the inside wall surface of the leg. The frame is expanded to the expanded position so that the frame engages the leg before a detonating of the charge. 
     The expandable frame enables the frame to be lowered or otherwise remotely delivered to a site that would ordinarily be inaccessible. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view of a typical offshore oil and gas well drilling platform prior to removal; 
     FIG. 2 is an exploded perspective view of the preferred embodiment of the apparatus of the present invention; 
     FIG. 3 is a perspective view of the preferred embodiment of the apparatus of the present invention; 
     FIG. 4 is a sectional view taken along lines  4 — 4  of FIG. 3; 
     FIG. 5 is an elevational view of the preferred embodiment of the apparatus of the present invention taken along line  5 — 5  of FIG. 3; 
     FIG. 6 is a top view of the preferred embodiment of the apparatus of the invention; 
     FIG. 7 is perspective cutaway view illustrating the method the present invention and showing the apparatus of the present invention during installation; 
     FIG. 8 is a fragmentary sectional elevational view of the preferred embodiment of the apparatus of the present invention; 
     FIG. 9 is a fragmentary sectional elevational view of the preferred embodiment of the present invention showing destination of the explosive portion; 
     FIG. 10 is a fragmentary sectional elevational view illustrating the leg of a fixed platform after it has been severed using the method and apparatus of the present invention; 
     FIG. 11 is a top, plain view of the preferred embodiment of the apparatus of the present invention and illustrating the first step of the method of the present invention; 
     FIG. 12 is a top, plain view of the preferred embodiment of the apparatus of the present invention and illustrating the second of the method of the present invention; 
     FIG. 13 is a top, plain view of an alternate embodiment of the apparatus of the present invention; 
     FIG. 14 is an elevational view illustrating the final method step of the present invention; 
     FIG. 15 is an exploded perspective view of a third embodiment of the apparatus of the present invention; 
     FIG. 16 is a sectional, elevational, partially cut away view of the third embodiment of the apparatus of the present invention; 
     FIG. 17 is a side elevational view of a fourth embodiment of the apparatus of the present invention showing the delivery system of the present invention; 
     FIG. 18 is a top view of the delivery system in FIG. 17; 
     FIG. 19 is a side elevational view of the delivery system of FIGS. 17 and 18 shown in expanded position; 
     FIG. 20 is a top plan view of the delivery system in expanded position; 
     FIG. 21 is a side elevational view illustrating delivery of the frame and explosive charges as part of the delivery system and when the frame is in retracted position; 
     FIG. 22 is a fragmentary, perspective view of the delivery system of FIGS. 17-21; 
     FIG. 23 is a side, fragmentary view taken along lines  23 — 23  of FIG. 22; 
     FIG. 24 is a side, fragmentary view of the frame portion of the delivery system of the present invention; 
     FIG. 25 is a fragmentary view illustrating the third embodiment of the apparatus of the present invention; 
     FIG. 26 is a side elevational view illustrating the expanded position of the delivery system; and 
     FIG. 27 is a schematic, side elevational view showing detonation of the charges that are part of the third embodiment of the apparatus of the present invention. 
     For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, there can be seen a typical fixed platform  10  anchored to the seabed  12  in an offshore marine environment. The fixed platform  10  typically includes a plurality of vertical leg members  14 ,  15  and a number of transversely extending structural members  16 . In keeping with good engineering practice, the vertical members  14 ,  15  are extended well into the seabed  12  a minimum dimension “A” as shown in FIG. 1, typically at least 16 or more feet. 
     The present invention provides a method and apparatus for removing abandoned platforms  10  that are no longer used in oil or gas well drilling or production or other related use. This is accomplished by providing an explosive apparatus  20  that is placed within the interior  17  of a selected vertical leg member  14 ,  15  with the help of a diver  18  that is supported by a plurality of life support cables  19  tethered from a tending vessel floating above. 
     In FIGS. 3 and 4, explosive apparatus  10  includes a telescoping strut member  21  that has end portions  22 ,  23 . The telescoping strut member  21  forms a connection at end portion  22  with curved member  24 . A pair of turnbuckles  25 ,  26  extend between telescoping member  21  and curved member  24  as shown in FIGS. 2 and 3. 
     Extension and retraction of turnbuckles  25 ,  26  enables the user to change the curvature of the curved member  24 . 
     The telescoping member  21  includes a telescoping threaded shaft portion  27  having external threads  28  thereon (see FIG.  5 ). The threads  28  engage and move with respect to correspondingly shaped internally threaded barrel  31  of strut member  21 . A transverse bar  34  is affixed to threaded shaft portion  27 . Handles  33  can be rotated by a user in order to extend or retract the shaft  27  relative to barrel  31 . 
     During use, a user rotates the handles  33  until the threaded shaft  27  has extended fully, wherein the bar  34  engages the inside wall surface  35  of a vertical leg member  14 ,  15 . During use, a user also moves the turnbuckles  25 ,  26  in or out as shown by the curved arrows  29 ,  30  in FIG. 6 in order to change the curvature of curved member  24 . In FIG. 6, the phantom lines show a smaller curvature for the curved member  24  and the hard lines show a larger curvature thereof. 
     Once the explosive apparatus  20  has been positioned as shown in FIGS. 11 and 12 against the inside surface  35  of a selected vertical member  14  or  15 , an explosive charge  40  can be detonated to partially sever the leg  14  or  15 . Explosive charge  40  is pressed against inside wall surface  35  of a jacket leg or vertical member  14 ,  15  as shown in FIG.  8 . The explosive charge  40  is preferably about 5 pounds of explosives or less. The explosive  40  can be a plastic bonded explosive (PBX) in sheet form such as a manufactured Ensign Bickford Company or Hi Tech so that it can be layered. The curved member  24  engages and presses against the explosive charge  40  holding it against the inside surface  35  of the selected vertical member  14  or  15  (see FIGS.  4  and  8 ). 
     A rubber block  36  that is preferably trapezoidally shaped in cross section is positioned in between the explosive material  40  and the inside surface  35  of the selected vertical member  14  of  15 . The block  36  thus provides a flat surface  37 , and a pair of inclined surfaces  38 ,  39  that form an angle with the surface  37 . The angle formed by surfaces  38  and  39  is preferably between about 100 and 160 degrees. Additionally, a flat surface  41  is provided in between the inclined surfaces  38 ,  39 . The surface  41  is preferably parallel to the surface  37 . Fuse  42  can be used to detonate the explosive charge  40 . Multiple fuses  42  can be employed as shown in FIG.  11 . In FIG. 9, lines of force  43  are shown demonstrating the focusing of explosive force to a focal point at the leg wall, using the apparatus  20  of the present invention to sever the vertical members  14  or  15 . In FIG. 10, the numeral  44  indicates this focal point, namely the fracture site. 
     In FIGS. 11 and 12, the sequence of the method of the present invention is shown more particularly. In FIG. 11, the apparatus  20  is first positioned to cut one-half of the leg when explosive forces follow the pattern of arrows  45 . In FIG. 12, a fracture  44  has been made extending about 180 degrees around a selected vertical member  14  or  15 . In FIG. 12, the apparatus  20  has been repositioned as shown to fracture the remaining 180 degrees of the selected leg  14  or  15 . The arrows  46  indicate the direction of force applied by the explosive charge in FIG. 12 as the second one-half portion (i.e. 180 degrees) of the selected leg or vertical member  14 ,  15  is cut. The platform vertical members such as  14 ,  15  can be cut one at a time. Alternatively, multiple vertical members or legs  14 ,  15  can be rigged with the apparatus  20  of the present invention so that charges can be detonated on multiple legs at one time which becomes an efficient procedure when dealing for example with very large offshore platforms  10 . 
     FIG. 13 shows an alternate version of the apparatus of the present invention, designated generally by the number  20 A. In the embodiment of FIG. 13, the telescoping member  21  is constructed like the embodiment of FIGS. 1-12. However, the curved member  24  is replaced by the curved member  24 A that extends about 120 degrees as shown by the angle alpha in FIG.  13 . With the embodiment of FIG. 13, the turnbuckles  25 ,  26  are replaced with rigid struts  47 ,  48 . The curved member  50  holds and explosive charge  49  as configured like the embodiment of FIGS. 1-12, however it is shorter in length, extending a measure of about 120 degrees. With the embodiment of FIGS. 13, three positioning of frame  20 A are required rather than the two positionings required for apparatus  20  as show in FIGS. 11 and 12. 
     In FIG. 14, a crane  51  is shown having a crown block  52  for lifting platform  10  once it has been severed below the seabed  11 . Once severed, the platform  10  can be lifted, leaving remnants of the legs  14 ,  15  well below the mud line in an environmentally less harmful position. The platform  10  can be lifted upwardly as shown by arrow  53  in FIG.  14 . The salvaged platform  10  is placed upon barge  54  for transport to a remote location such as a salvage yard, fabrication yard, scrap yard or the like. Some platforms are reusable. The present invention is minimally invasive of the platform structure so that reuse is not compromised by the method of the present invention. 
     FIGS. 15 and 16 show a third embodiment of the apparatus of the present invention designated generally by the numeral  55  in FIGS. 15 and 16. 
     Explosive apparatus  55  can be used on a leg member  56  by placing the apparatus  55  on the outer surface  39  of the leg member  56  as shown in FIG.  16 . The leg member  56  has a hollow interior  57  surrounded by inner surface  58  of leg member  56 . 
     In FIGS. 15 and 16, a generally circular strap member  60  has an inner surface  61  that is cylindrically shaped to conform generally to the cylindrically shaped outer surface  71  of explosive charge  69 . The strap member  60  has a pair of flanges  62 ,  63  the form a closure when the strap member  60  is placed around leg  56  as shown in FIG.  16  and encircling wave shaper  73  and explosive charge  69 . 
     The flanges  62 ,  63  are secured together during use, tightening the strap member  61  in position using threaded fastener  64  and wing nut  65 . Slot  66  on flange  63  receives threaded fastener  64 . The assembly is tightened with wing nut  65  once in position on leg  56 . 
     The explosive charge  69  provides an inner surface  72  that is placed against wave shaper  73  and an outer surface  71  that is placed against surface  61  of strap member  60 . 
     A beam that is comprised of pair of flanges  67 ,  68  can be placed at 90 degrees with respect to each other (e.g. welded) as shown in FIGS. 15 and 16 and welded to strap member  60  for reinforcing strap member  60 . 
     Wave shaper  73  includes a cylindrically shaped inner surface  74  and a plurality of outer surfaces  75 ,  76 ,  77 . The outer surface  77  is generally cylindrically shaped for engaging the flat inner surface  72  of explosive charge  69 . A pair of beveled annular surfaces  75 ,  76  are inclined with respect to each other and with respect to inner surface  74  as shown in FIG.  16 . 
     A fourth embodiment of the apparatus of the present invention, designated generally by the numeral  80  in FIG. 17, shows an improved delivery system and explosive apparatus for severing a leg or pipe in an underwater marine environment. 
     Delivery apparatus  80  includes a frame  81  having an upper end portion  82  and a lower end portion  83 . An eyelet  84  can be used to secure a cable  85  to frame  81  so that the frame  81  can be lowered into a pipe, platform leg or like tubular member  88  as shown in FIG. 21 in the direction of arrow  86 . Tubular member  88  has a bore  87  into which frame  81  is placed and lowered when the frame  81  is in the retracted position of FIGS. 17,  18 , and  20 . 
     The frame  81  is comprised of a central, vertical post  91  to which a plurality of struts are pivotally attached. An upper sleeve  117  slides upon post  91 . Similarly, a lower sleeve  118  slides upon post  91 . Attachment plates  119  extend laterally from sleeve  117 . Upper struts  89  form pivotal attachments to sleeve  117  at attachment plates  119 . Similarly, lower struts  90  are pivotally attached to lower sleeve  118  at plates  120 . 
     A plurality of charge carriers  92  provide chambers  93  (see FIG. 23) for containing explosive material  94 . A detonator  95  also communicates with chamber  93  for exploding the material  94 . Shaper  96  is placed within chamber  93  for shaping the explosion, forming a cutting jet when material  93  is detonated. Chamber  93  is surrounded by housing  97  that includes arcuate wall  98 , arcuate wall  99 , flat end walls  100 ,  101 , and upper and lower walls  102 ,  103 . 
     Attachment plates  104  extend upwardly from upper wall  102  and downwardly from bottom wall  103  as shown in FIG.  22 . Bolted connections  105  can be used for attaching upper and lower struts  89 ,  90  respectively to housing  97  as shown in FIGS. 22 and 23. 
     Detonating cord  106  is supplied to each of the detonators  95 . Electric line  107  is used to detonate electric detonator  108 . The electric detonator  108  is used to sever horizontal cable  109  that holds frame  81  in a retracted position as shown in FIGS. 17,  18  and  21 . Horizontal cable  109  extends between gussets  110 . The cable  109  holds the frame  81  in the retracted position of FIGS. 17 and 21 by compressing upper and lower springs  111 ,  112 . Upper spring  111  extends between disc  113  and disc  114 . Similarly, lower spring  112  extends between disc  115  and disc  116 . The discs  114 ,  116  engage respective upper and lower sleeves  117 ,  118  as shown in FIG.  17 . 
     When the apparatus  80  is to be deployed, it is lowered to a selected location inside the bore  87  of tubular member  88  as shown in FIG.  21 . An operator then detonates the detonator  95  using primer cord  96 . Electric line  107  is used for detonating electric detonator  108  to sever cable  109  as shown in FIGS. 24-26. The cable  109  extends through openings  121 ,  122  in post  91  as shown in FIG.  25 . 
     Once the detonator  108  severs cable  109 , upper and lower springs  11 ,  112  expand as shown in FIG.  19 . Springs  111 ,  112  urge the sleeves  117 ,  118  in the directions respectively of arrows  123 ,  124  causing the struts  89 ,  90  to push the charge carriers  92  outwardly in the direction of arrows  125 ,  126  (see FIG.  19 ). As shown in FIG. 26, the expanded frame  81  places charge carriers  92  against the inside surface of tubular member  88 . Detonator cord  106  can then be used to detonate the explosive material  94  contained in chamber  93  severing the tubular member  88  into upper  88 A and lower  88 B sections and creating a fracture  127  (see FIG.  27 ). 
     The following table lists the parts numbers and parts descriptions as used herein and in the drawings attached hereto. 
     
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
             
          
           
               
                 Part Number 
                 Description 
               
               
                   
               
             
          
           
               
                  10 
                 fixed platform 
               
               
                  11 
                 mud line 
               
               
                  12 
                 seabed 
               
               
                  13 
                 water surface 
               
               
                  14 
                 vertical leg member 
               
               
                  15 
                 vertical leg member 
               
               
                  16 
                 transverse leg member 
               
               
                  17 
                 interior 
               
               
                  18 
                 diver 
               
               
                  19 
                 support cables 
               
               
                  20 
                 explosive apparatus 
               
               
                 20A 
                 explosive apparatus 
               
               
                  21 
                 telescoping strut member 
               
               
                  22 
                 end 
               
               
                  23 
                 end 
               
               
                  24 
                 curved member 
               
               
                 24A 
                 curved member 
               
               
                  25 
                 turnbuckle 
               
               
                  26 
                 turnbuckle 
               
               
                  27 
                 telescoping rod 
               
               
                  28 
                 threads 
               
               
                  29 
                 arrow 
               
               
                  30 
                 arrow 
               
               
                  31 
                 barrel 
               
               
                  32 
                 interval threads 
               
               
                  33 
                 handle 
               
               
                  34 
                 bar 
               
               
                  35 
                 inside wall surface 
               
               
                  36 
                 block 
               
               
                  37 
                 large flat surface 
               
               
                  38 
                 inclined surface 
               
               
                  39 
                 inclined surface 
               
               
                  40 
                 explosive change 
               
               
                  41 
                 small flat surface 
               
               
                  42 
                 fuse 
               
               
                  43 
                 force lines 
               
               
                  44 
                 fracture 
               
               
                  45 
                 arrow 
               
               
                  46 
                 arrow 
               
               
                  47 
                 strut 
               
               
                  48 
                 strut 
               
               
                  49 
                 explosive charge 
               
               
                  50 
                 curved member 
               
               
                  51 
                 crane 
               
               
                  52 
                 crown block 
               
               
                  53 
                 arrow 
               
               
                  54 
                 barge 
               
               
                  55 
                 explosive apparatus 
               
               
                  56 
                 leg member 
               
               
                  57 
                 hollow interior 
               
               
                  58 
                 inner surface 
               
               
                  59 
                 outer surface 
               
               
                  60 
                 strap member 
               
               
                  61 
                 inner surface 
               
               
                  62 
                 flange 
               
               
                  63 
                 flange 
               
               
                  64 
                 threaded fastener 
               
               
                  65 
                 wing nut 
               
               
                  66 
                 slot 
               
               
                  67 
                 flange 
               
               
                  68 
                 flange 
               
               
                  69 
                 explosive charge 
               
               
                  70 
                 fuse 
               
               
                  71 
                 outer surface 
               
               
                  72 
                 inner surface 
               
               
                  73 
                 wave shaper 
               
               
                  74 
                 cylindrical inner 
               
               
                  75 
                 annular surface 
               
               
                  76 
                 annular surface 
               
               
                  77 
                 annular surface 
               
               
                  80 
                 delivery apparatus 
               
               
                  81 
                 frame 
               
               
                  82 
                 upper end 
               
               
                  83 
                 lower end 
               
               
                  84 
                 eyelet 
               
               
                  85 
                 cable 
               
               
                  86 
                 arrow 
               
               
                  87 
                 bore 
               
               
                  88 
                 tubular member 
               
               
                 88A 
                 upper section 
               
               
                 88B 
                 lower section 
               
               
                  89 
                 upper strut 
               
               
                  90 
                 lower strut 
               
               
                  91 
                 central vertical post 
               
               
                  92 
                 charge carrier 
               
               
                  93 
                 chamber 
               
               
                  94 
                 explosive material 
               
               
                  95 
                 detonator 
               
               
                  96 
                 shaper 
               
               
                  97 
                 housing 
               
               
                  98 
                 arcuate wall 
               
               
                  99 
                 arcuate wall 
               
               
                 100 
                 flat end wall 
               
               
                 101 
                 flat end wall 
               
               
                 102 
                 upper wall 
               
               
                 103 
                 bottom wall 
               
               
                 104 
                 attachment plate 
               
               
                 105 
                 bolted connection 
               
               
                 106 
                 detonator cord 
               
               
                 107 
                 electric line 
               
               
                 108 
                 electric detonator 
               
               
                 109 
                 horizontal cable 
               
               
                 110 
                 gusset 
               
               
                 111 
                 upper spring 
               
               
                 112 
                 lower spring 
               
               
                 113 
                 disk 
               
               
                 114 
                 disk 
               
               
                 115 
                 disk 
               
               
                 116 
                 disk 
               
               
                 117 
                 sleeve 
               
               
                 119 
                 plate 
               
               
                 120 
                 plate 
               
               
                 121 
                 opening 
               
               
                 122 
                 opening 
               
               
                 123 
                 arrow 
               
               
                 124 
                 arrow 
               
               
                 125 
                 arrow 
               
               
                 126 
                 arrow 
               
               
                 127 
                 fracture 
               
               
                   
               
             
          
         
       
     
     The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.