Abstract:
A method of hot tapping into a multiple string configuration for obtaining access to the production tubing without removing outer layers of casing by providing a multiple casing string that includes at least an outer casing and an inner casing or production string; mounting a clamp assembly around the wall of the outer casing; hot tapping a small opening through the outer casing wall to capture any pressurized fluid through the opening; cutting first and second large openings through the wall of the outer casing to access the inner casing, each opening being approximately 180 degrees from the other opening; through the first opening, drilling a small hole through the wall of the inner casing to capture any pressurized fluid through the opening in the inner casing; and inserting an anvil through the second opening to contact and stabilize the wall of the inner casing to prevent the casing from moving while the casing is drilled.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 13/908,657, filed Jun. 3, 2013, which is a continuation of U.S. patent application Ser. No. 13/104,397, filed May 11, 2011 (issued as U.S. Pat. No. 8,474,473 on Jul. 2, 2013), which is a continuation of U.S. patent application Ser. No. 12/276,863, filed Nov. 24, 2008 (issued as U.S. Pat. No. 7,938,137 on May 10, 2011), which is a nonprovisional of U.S. Provisional Patent Application Ser. No. 60/990,498, filed Nov. 27, 2007, each of which is incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not applicable 
       REFERENCE TO A “MICROFICHE APPENDIX” 
       [0003]    Not applicable 
       BACKGROUND OF THE INVENTION 
       [0004]    1. Field of the Invention 
         [0005]    The process of the present invention relates to gaining access to the production tubing to vent fluid pressure within the tubing. More particularly, the present invention relates to a hot tapping system to vent pressurized fluids that eliminates the need to remove the outer layer of casing to obtain access to the production tubing. 
         [0006]    2. General Background of the Invention 
         [0007]    The conventional hot tap system is designed to allow hot tapping of the outer casing. For the conventional hot tap system, the outer casing must be removed by a process known as wedding caking to proceed to the next casing string. The conventional hot tap system takes more time and equipment to complete the same job as the Multiple String Hot Tap System. With more conventional Hot Tap System, the outer casing strings must first be hot tapped to release any trapped pressure in the casing or pump heavier fluid plug into the casing overcome the pressure. Once the pressure is released or controlled, a support structure can be attached to the outer casing for removal of a small section of the outer casing. This process is known as wedding caking; because each layer of casing is removed in layers. Once the small section of outer casing has been removed, the next casing string can now be hot tapped to gain control of this casing layer. The cycle of casing removal and hot tapping is repeated until the production tubing is reached. Once the production tubing has been hot tapped and the well bore has been controlled, the damage well casing and wellhead can be removed. 
         [0008]    A temporary wellhead is installed on the well using the remaining casing. With the temporary wellhead in place, Plug and Abandonment operation can be started. The conventional hot tapping system could take several weeks to complete all of the hot tapping and vent of casing strings and production tubing. With a temporary wellhead installed, wireline or coil tubing operation can be used to lock open the SCSSV (surface control subsurface safety) with the manufacturers lock open tools. If there is pressure below the SCSSV, a bridge plug or tubing plug can be set to plug off the wellbore. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    What is provided is a method of hot tapping into a multiple string configuration for obtaining access to the production tubing without removing outer layers of casing by providing a multiple casing string that includes at least an outer casing and an inner casing or production string; mounting a clamp assembly around the wall of the outer casing; hot tapping a small opening through the outer casing wall to capture any pressurized fluid through the opening; cutting first and second large openings through the wall of the outer casing to access the inner casing, each opening being approximately 180 degrees from the other opening; through the first opening, drilling a small hole through the wall of the inner casing to capture any pressurized fluid through the opening in the inner casing; and inserting an anvil through the second opening to contact and stabilize the wall of the inner casing to prevent the casing from moving while the casing is drilled. 
         [0010]    The multiple string hot tap system is a hot tapping system that eliminates the need to remove the outer layers of casing to obtain access to the production tubing. The system is designed around a unique hot tap clamping system which has a 4 or 6 inch diameter bore in the center of the clamps. This bore in the center of the clamps will be used to drill an access hole in the outer casing after the casing has been hot tapped. The access holes are later used to hot tap the next casing string. 
         [0011]    The multiple string hot tap system eliminates the need for removal of the outer layers of casing to gain access to the inner layers of casing and the production tubing. The system designed around two clamps (a front clamp and a rear clamp). The two clamps are connected together with four chains. The chains are tensioned by applying torque to the nuts on the chain connector. The tension on the chains is based on the outer casing or surface casing size, wall thickness and material properties. If the chains are tensioned too high, the casing will fall in collapse. The maximum hot tapping pressure for the assembly is controlled by the outer casing specification and the specific set up of the multiple string hot tap assembly. The maximum hot tapping pressure can be increased by adding tension chains and increasing clamp bearing area. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    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: 
           [0013]      FIG. 1  illustrates a cross sectional view of the hot tap assembly in the system of the present invention; 
           [0014]      FIG. 2  illustrates a front view of the hot tap assembly of the present invention; 
           [0015]      FIG. 3  illustrates a rear view of the hot tap assembly of the present invention; 
           [0016]      FIG. 4  illustrates a side view of the hot tap assembly of the present invention; 
           [0017]      FIG. 5  illustrates a front view of the hot tap assembly of the present invention with front donut removed; 
           [0018]      FIG. 6  illustrates a cross-section view of the hot tap assembly of the present invention with access holes; 
           [0019]      FIG. 7  illustrates a cross-section view of the hot tap assembly of the present invention modified for inner casing hot tap; 
           [0020]      FIG. 8  illustrates the hot tap assembly with front clamp modified with larger bearing area; 
           [0021]      FIG. 9  illustrates a side view of the modified hot tap assembly with front clamp modified with larger bearing area; 
           [0022]      FIG. 10  illustrates a cross-section view of alternative hot tap clamp assembly of the present invention with larger access holes; 
           [0023]      FIG. 11  illustrates a front view of alternative hot tap clamp assembly of the present invention with larger access holes; 
           [0024]      FIG. 12  illustrates a side view of alternative hot tap clamp assembly of the present invention with larger access holes; and 
           [0025]      FIG. 13  illustrates a side view of the chain connector with hydraulic cylinder to better control the tensile/clamping loads in the system of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    As will be seen more clearly in  FIGS. 1 through 13 , the method of the present invention relates to hot tapping a damaged oil well to release any pressure within the layers of casing or pipe, without removing the outer casing string to access inner casing strings and production tubing. The novel method utilizes a multiple string hot tap system  10 , also referred to as the novel System  10 . The equipment is designed to allow hot tapping of each string of pipe in the completion without removal of the support clamps. 
         [0027]    In the present system, as illustrated in the various  FIGS. 1 through 13 , a front clamp  18  and a rear clamp  36  are connected together with four tension chains  22 . The chains  22  are tensioned by applying torque to the nuts  10  on the chain connectors  14 . The tension on the chains  22  is based on the outer casing size, wall thickness, and material properties. If the chains  22  are tensioned too high, the casing  24  will fall and collapse. This amount of tension in the chains  22  will also control the maximum pressure that the hot tap assembly  10  can operate at or drill. 
         [0028]    With the novel System  10 , each casing string  24  is first hot tapped with a standard hot tap drill. The hot tap drill size is generally a ½ to ¾ inch diameter. After each casing string has been drilled, access holes  25  are bored. The access holes provide a way to extend the hot tap seal saddle  32  to the next casing string  260   r  the production tubing  28 . The access holes  25  are generally 6 inches in diameter for casing sizes larger than 9 inches in diameter. For casing size smaller than 9 inches in diameter, the access hole can be as small as 3 inches in diameter. The process is repeated for each inner casing string until the production tubing is reached without removing each casing string. 
         [0029]    The novel System or method, as illustrated fully in the figures, and more completely in  FIG. 7 , is designed around two cramps (a front clamp  18  and rear clamp  36 ) as shown above in the drawing figures of the hot tap assembly  10 . The key to the system is the larger access bores  25  in the two clamps  18 ,  36  which provide access to inner casing string  26  and production tubing  28 . The major components of the novel System  10  would comprise a front clamp  18  with large access bore  25 ; rear clamp  36  with large access bore  25 ; a front donut  30  with replaceable hot tap seal saddle  32 ; a rear donut  38  with adjustable rear support anvil  40 ; and an extension  44  for hot tap seal saddle  32  positioning. 
         [0030]    A critical feature of the multiple string hot tap system  10  includes a provision to allow the stabilization or gripping the inner string  26  or pipe  28  for hot tap drilling. Through a second access hole  25 , the rear support anvil  40  is installed 180° from the hot tap seal saddle  32 . The casing/pipe  26  is firmly held in place. This eliminates the need to force to one side of the outer pipe  24  and insure that the inner pipe  26  will not move during the hot tap operations. It also prevents the pipe  26  that is being hot tap grabbing the drill and failing in buckling due to bending loads. 
         [0031]    The multiple string hot tap system  10  shows the use of standard hot tap drilling equipment. The donut insert  30  which contains the hot seal saddle mechanism  32  has been designed to allow the uses of extensions  44  to make up the addition distance to the next pipe. As stated earlier, the multiple string hot tap system  10  also provides a rear support anvil  40  for stabilization the inner string to be hot tapped. The rear support anvil  40  has been designed to allow position adjustment by screwing the anvil  40  in or out of the rear donut insert  38 . The multiple string hot tap system has a wider clamp to provide more support and bearing area. The increase bearing area provides higher operating pressure. The wider clamp can provide more resistant to bending load that are created by the hot tap drilling subassembly. 
         [0032]    The present novel System  10  is connected using a combination of roller chains  22  and chain connectors  14 . The chains  22  are tensioned by applying torque to the nuts  12  on the end of the chain connector  14 . The condition of a coating of Teflon (a registered Trademark of DuPont Corp.) on the chain connector threads and the nuts  12  will control the actual tension in the chain  22 . On chain connectors  14  and nuts  12 , with new Teflon coating, the coefficient of friction is low about 0.15 to 0.05. On chain connectors  14  and nuts  12  with worn Teflon coatings, the coefficient of friction is higher about 0.2 to 15. As the coefficient of friction rises, the tensile load for a specific torque falls. In the present hot tap system, the specified setting torque is about 50 ft-lbs to 105 ft-lbs to produce 5000 lbs. of clamping load in the chain. If a hydraulic cylinder  50 , of the type illustrated in  FIG. 13  was added to the chain connectors  14 , the clamping load can be controlled by applying especial hydraulic pressure. The modified chain connectors  14  would replace each one of the four standard chain connectors  14  and nuts  12 . This would eliminate the problems of accurately applying clamping loads. The clamping loads would be uniformly applied to each of the four chain in the hot tap clamp assembly. 
         [0033]    As illustrated in the  FIGS. 1 through 13 , to carry out the method in the multiple string hot tap system  10  of the present invention, the first each casing string  24  is first hot tapped with a standard drill. The standard hot tap drill size is generally ½ to ¾ inch in diameter. Next, the multiple string hot tap clamp assembly  10  is installed on the outer casing  24  without the front donut  30  and the rear donut  38  in place. In the preferred embodiment, the centerline of the front clamp  18  and the rear clamp  36  should be aligned to insure that correct support on future operations. The chains  22  should be tensed only enough to hold the clamp assembly  10  in place. There is next provided a chain tensioning nut  12  which should be torqued to the value specified preferably by the engineer in charge of the plug and abandon operation. The torque value is based on the casing specification, hot tap pressure, and condition of the component of the hot tap assembly components. Next, the rear donut  38  with the rear support anvil  40  is installed. The position of the rear support anvil  40  should be adjusted to insure that there is a minimum gap of 0.060 inch between the rear donut  38  and the rear clamp  36  when the retainer bolts  12  are installed. The retainer bolts  12  can be replaced with 4 swing bolts and nuts. The swing bolts  12  are then pinned to the rear clamp  36 . In the next step, the front donut  30  with the hot tap seal saddle  32  is installed. The position of the hot-tap seal saddle  32  should be adjusted to insure that the there is a minimum gap of 0.060 inch between the front donut  30  and the front clamp  18  when the retainer bolts  12  are installed. The retainer bolts  12  may be replaced with 4 swing bolts and nuts. The swing bolts are pinned to front clamp. Again, the front retainer bolts  12  should be torqued to the value specified by the engineer in charge of the plug and abandon operation. The torque value is based on the hot tap, pre-charge pressure that is required. The pre-charge pressure is usually set at a higher than the casing. The pressure provides an indicator when the hot tap drill breaks through the easing wall by dropping. 
         [0034]    Next, the hot tap drilling sub assembly  10  is attached to the front donut  30  and the hot tap saddle  32  as illustrated. The hot tap drilling subassembly would include the hydraulic drill or manual drill with a drill bit; the pressure gauge to monitor hot tap drill pre-charge pressure; the pressure pre-charge control valve; the hot tap vent valve; and the union. 
         [0035]    The hot tap drilling subassembly should be pressured up to the pre-charge value that was specified by the engineer in charge of the plug and abandon operation. The casing or pipe is drilled with ½ to ¾ inch diameter bit when the bit breaks through the pipe wall, the pre-charge pressure will drop to a casing or pipe internal pressure. The casing or pipe internal pressure is vented and the hot tap drilling sub assembly  10  is removed. Next, the front donut  30  with the hot tap saddle  32  is removed. The rear donut  38  with the hot tap rear support anvil  40  is removed. The rail system, which is used to support and position the large diameter drill (4 inch to 6 inch in diameter) or hole saw, is then installed on the outer casing  24  below the multiple string hot tap clamp assembly  10 . If the multiple string hot tap clamp assembly  10  has to be moved or rotated to provide better support during hot tapping of an inner casing string  26 , the rail system can also be used as a support while the clamp is repositioned. 
         [0036]    Next, a probe is then run into hot tap hole, and the location of the next inner casing string or production tubing  26  is determined. If the inner casing or pipe  26  is not located on the center line the hot tap clamps  18 ,  36 , the hot tap clamps must be repositioned to insure that the next string is located In the center tine of the hot tap clamps. Two access holes  25  are drilled in the outer casing  24 . The first access hole  25  is drilled through the clamp  18 . The second access hole  25  is drilled through the rear clamp  36 . The access holes  25  will allow the hot tap saddle  32  to be installed on the inner casing  26  and the rear support anvil  40  to be installed. Before the rear donut  38  is installed, the rear support anvil  40  must be adjusted. When the rear donut  38  is installed and bolted in the rear hot tap clamp  36 , the flange on the rear donut  38  should have an offset gap with the rear clamp  36 . The rear donut  38  is now installed. 
         [0037]    Before the front donut  30  is installed, the hot tap seal saddle  32  must match the casing diameter or pipe diameter. The position of the hot tap saddle  32  is adjusted by inserting the hot tap seal saddle extensions  44 . When the front donut  30  is installed and bolted in the front hot tap clamp  18 , the flange on the front donut  30  should have an offset gap with the front clamp  18 . Next, the front donut  30  is installed. The front donut  30  retaining bolts or nuts  12  should be made up to the torque value that is specified by the engineer in charge of the plug and abandon operation. The torque value is based on the hot tap pre-charge pressure. 
         [0038]    The hot tap drilling sub assembly  10  is attached to the front donut  30  and the hot tap saddle  32 . The hot tap drilling subassembly would include the hydraulic drill or manual drill with a drill bit; the pressure gauge to monitor hot tap drill pre-charge pressure; the pressure pre-charge control valve; the hot tap vent valve; and the union. The hot tap drilling subassembly should be pressured up to the pre-charge value that was specified by the engineer in charge of the plug and abandon operation. The casing or pipe is drilled with a ½ to a ¾ inch diameter bit. When the bit breaks through the pipe wall, the pre-charge pressure will drop to a casing or pipe internal pressure. The casing or pipe internal pressure is vented. 
         [0039]    Following the venting of the internal pressure in the casing or pipe, as described above, the process is repeated for each addition inner casing layer and production tubing in the well has been drilled and the pressure vented or brought under control. For each casing layer, the multiple string hot tap seal saddle  32  must be changed to match the casing or tubing diameter. In addition, seal saddle extensions  44  must be added to compensate for the added distance from the multiple string hot tap clamp assembly  10 . 
         [0040]      FIGS. 8 through 10  illustrate front, side and overall views respectively of the multiple string hot tap system  10  having a front clamp  18  designed to provide a larger bearing area  19 , and for providing larger access holes  25  in the casing or pipe. The claim  18  is held in place by a series of four tension chains  22  secured to nuts  12 . 
         [0041]      FIGS. 11 and 12  illustrate front and side views respectively of yet another modified manner in which to secure the front and rear  18 ,  36  onto the wall of the casing  24  so as to provide a more stable means to hot tap the casing  24 , and drill the larger access bores  25  in order to have access to the next size casing or tubing  26  and production strings  28 . 
         [0042]    As referenced earlier,  FIG. 13  illustrates the use of a hydraulic cylinder  50  that would be engaged to the chain connectors  14 , so that the clamping load can be controlled by applying especial hydraulic pressure. The modified chain connectors  14  would replace each one of the four standard chain connectors  14  and nuts  12 . This would eliminate the problems of accurately applying clamping loads. The clamping loads would be uniformly applied to each of the four chain in the hot tap clamp assembly. 
         [0043]    The following is a list of parts and materials suitable for use in the present invention. 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
             
          
           
               
                 Part Number 
                 Description 
               
               
                   
               
               
                 10 
                 multiple string hot tap system 
               
               
                 12 
                 chain tensioning nut 
               
               
                 14 
                 chain connector 
               
               
                 16 
                 washer 
               
               
                 18 
                 front clamp 
               
               
                 19 
                 larger bearing area 
               
               
                 20 
                 anvil 
               
               
                 22 
                 tension chain 
               
               
                 24 
                 surface casing 
               
               
                 25 
                 access bores 
               
               
                 26 
                 production casing 
               
               
                 28 
                 production tubing 
               
               
                 30 
                 front donut 
               
               
                 32 
                 hot tap seal saddle 
               
               
                 34 
                 Teflon seal ring 
               
               
                 36 
                 rear clamp 
               
               
                 38 
                 rear donut 
               
               
                 40 
                 rear support anvil 
               
               
                 44 
                 extension 
               
               
                 50 
                 hydraulic cylinder 
               
               
                   
               
             
          
         
       
     
         [0044]    All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
         [0045]    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.