Patent Publication Number: US-7588393-B1

Title: Method for supporting top tension drilling and production risers on a floating vessel

Description:
FIELD 
     The present embodiments relate to a method for supporting top tension drilling and production risers on a floating vessel. 
     BACKGROUND 
     A need exists for a method for supporting top tension drilling and production risers, which eliminates the need for riser centralizers or stabilization between a tension ring, and well head equipment when the tensioner stroke range is large. A need exists for a method for supporting method for supporting top tension drilling and production risers that achieves stabilization by compensating a conductor, which transfers tension from the cylinders to the riser. 
     A need further exists for a method for supporting top tension drilling and production risers that utilizes a conductor that can protect the riser from impact with a vessel, and which can provide shelter from wave loading in a wave zone. 
     The present embodiments meet these needs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description will be better understood in conjunction with the accompanying drawings as follows: 
         FIG. 1  depicts front view of the tensioner assembly. 
         FIG. 2  depicts a side view of the tensioner assembly. 
         FIG. 3  is a cut view of the tensioner assembly. 
         FIG. 4  is an exploded view of an embodiment of the tapered bowl tension ring assembly. 
         FIG. 5  is a cut view of an embodiment of the tapered bowl tension ring assembly. 
         FIG. 6  depicts a side view of the tensioner assembly secured to a vessel. 
         FIG. 7  depicts a side view of the floating vessel that can be used with the embodiments of the method. 
         FIG. 8  is a flow diagram of the method for supporting top tension drilling and production risers on a floating vessel. 
     
    
    
     The present embodiments are detailed below with reference to the listed Figures. 
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Before explaining the present apparatus in detail, it is to be understood that the apparatus is not limited to the particular embodiments and that it can be practiced or carried out in various ways. 
     The embodiments can provide stabilization of a riser and reduce the equipment needed to stabilize the riser. This reduces costs associated with riser systems, and enhances the safety of the riser system. 
     The embodiments generally relate to a method for supporting top tension drilling and production risers on a floating vessel. The floating vessel for supporting top tension drilling and production risers has a hull and an operation deck disposed on top of the hull. 
     The floating vessel can be a semi-submersible floating vessel, a ship, a deep draft cassion, barge, a tension leg platform, or a similar floating vessel. 
     An embodiment of the method for supporting top tension drilling and production risers on a floating vessel using a tensioner assembly above the water line of the vessel can include the step of attaching at least one hydraulic cylinder on a first end to a first position on a floating vessel. A second end of the hydraulic cylinder can be attached to a tension frame below the first position. 
     In an embodiment of the method the hydraulic cylinder can be secured to the floating vessel using shackles, pins, or another rotating member adapted to form a rotatable joint. 
     The method can include attaching a plurality of hydraulic cylinders to the floating vessel. In this embodiment the method can include simultaneously using each hydraulic cylinder to apply tension to a plurality of risers within a plurality of conductors. 
     The hydraulic cylinder can apply a tension of at least 200 kips to the conductor. The hydraulic cylinders can have a pressure from about 100 psi to about 3500 psi, and can provide a load from about 200 kips to about 2500 kips. 
     In an embodiment of the method a support frame can be used to mount the at least one hydraulic cylinder and the at least one primary accumulator, and the support frame can be secured to the floating vessel. 
     In an embodiment the support frame can have a first beam and a second beam. The first beam and the second beam can be an I-beam, a C-channel beam, a tubular, or a similar support beam. 
     The pad eyes can have a diameter for receiving a shackle to hold the hydraulic cylinders. The pad eyes can be disposed on the beams or they can be integral with the deck of a vessel. 
     In another embodiment the support frame can be a cassette. The support frame can be secured to the floating vessel by welding. It is also possible that the support frame can be a self supporting frame disposed on the vessel. 
     The method can continue by forming a fluid connection between the at least one hydraulic cylinder and at least one primary accumulator. The accumulator can have a capacity of at least 1 gallon. The accumulator capacity can exceed 470 gallons. 
     The fluid connection can be a direct connection. In another embodiment the primary accumulator can be disposed remote from the hydraulic cylinder and pluming can be used to fluidly communicate the primary accumulator to the hydraulic cylinder. Examples of the method of pluming the accumulator to the hydraulic cylinder include using an umbilical cord, a tubular steel pipe, a flex pipe, or similar fluid communication device. 
     Each primary accumulator can be secured proximate to one of the hydraulic cylinders, or the primary accumulator can be remote to the hydraulic cylinder. It is possible to arrange the primary accumulators on the floating vessel remote from the hydraulic cylinder in a stacked module, thereby, forming a small footprint on the floating vessel. 
     An example of the accumulator being disposed proximate to the hydraulic cylinder would be mounting on the vessel close to the first position, or in another embodiment the accumulator can be secured to a support frame that is supporting the hydraulic cylinder. 
     An example of the accumulator being mounted remote from the hydraulic cylinder could include mounting the accumulators on a different deck, or on the same deck approximately about 30 feet to about 40 feet from the hydraulic cylinder. 
     The method can include securing a conductor disposed between a wellhead and a piece of well access equipment to the tension frame. The conductor can be bolted to the tension frame, welded to the tension frame, or connected to the tension frame in a similar manner. The conductor can be a fifty four inch outside diameter steel pipe. A riser can be disposed within the conductor. 
     The tension frame can be made from steel and can have a square, round, or rectangular shape. 
     After the conductor is secured to the tension frame the step of centralizing the conductor in an upper conductor guide and a lower conductor guide is performed. The upper conductor guide and the lower conductor guide are secured to the floating vessel. 
     The upper and lower conductor guides can each have a guide frame for supporting a conductor guide wear pad using a conductor guide retaining ring. 
     The upper conductor guide and the lower conductor guide can have different dimensions. The upper conductor guide and the lower conductor guide can be made from metal, composite, or similar structural material. The lower conductor guide can be made from the same or different material as the upper conductor guide. 
     The conductor guide frame can be metal, composite, or similar structural material. The conductor guide frame support conductor guide wear pads using a conductor guide retaining ring. The conductor guide retaining ring can be metal, composite, or any structural material. The conductor guide ring can be attached to the conductor guide frame by bolting, welding, or similar mechanical means. The conductor guide ring can be a complete ring or a segment of a ring. 
     The conductor guide wear pad can be made from an ultra high molecular weight polymer. The ultra high molecular weight polymer can be polypropylene, polyethylene, polybutylene, homopolymer, and copolymers thereof. The conductor wear pads can also be metal or any bearing material. 
     The method can continue by applying tension to a riser within the conductor using the at least one hydraulic cylinder. The conductor slidabley supports top tension drilling and production risers. The risers can be in contact with the piece of well access equipment. 
     The piece of well access equipment can include a blow out preventer, a production tree, or similar pieces of well access equipment. 
     In an embodiment of the method the tensioner assembly can have a tension ring assembly disposed on the conductor above the upper conductor guide. The tension ring assembly can be a tapered bowl tension ring assembly. 
     The tapered bowl tension ring assembly can include a tension disc having a tapered center. Tapered collets can engage the tension disc and a collet support ring can be disposed on the tapered collets to hold the collets together. The collet support ring can be steel or another structural and stiff member. The tapered collets engage the riser and are held together by the collet support ring. 
     The collet support ring is secured to the tension disc. The tension disc can have an outer diameter segment that engages the conductor with a thickness that is about 50 percent to about 70 percent the thickness of the inner diameter segment of the tension disc. The tension disc engages the collets that engage the riser. The tension disc can be made from metal and can have a diameter ranging from about 28 inches to about 63 inches. 
     In another embodiment the tension ring assembly can include a single tension disc directly engaging the conductor, and supporting the riser. 
     In an alternative embodiment the tension disc can be a solid segment with perforations. 
     The embodiments of the invention can be best understood with reference to the Figures. 
     Referring now to  FIGS. 1 ,  2 , and  6 , the tensioner assembly  1  has a conductor  10 . A tension frame  30  is secured to the conductor  10  and at least one hydraulic cylinder  14 . The hydraulic cylinder  14  is secured to a support frame  12 . The support frame  12  is depicted having a first beam  42  parallel to a second beam  44 . The first beam  42  and the second beam  44  can be connected to a rig  15 . A first beam pad eye  43   a  is disposed on the first beam  42 . A second beam pad eye  43   b  is disposed on the second beam  44 . 
     A primary accumulator  16  is depicted in direct fluid communication with the hydraulic cylinder  14 . 
     An upper conductor guide  18  and a lower conductor guide  20  slidably engage the conductor  10 . 
     The tension frame  30  transfers tension from the hydraulic cylinder  14  to the conductor  10 , then to a riser  32  and a piece of well access equipment  13 , as depicted. 
       FIG. 3  shows a cut view of the tensioner assembly  1 . The well access equipment  13  is depicted secured to the conductor  10 . The conductor  10  is secured to the well access equipment by a tension disc. The riser  32  extends through the center of the conductor  10 . The hydraulic cylinder  14  is depicted secured to the tension frame  30  and the support frame  12 . 
     The upper conductor guide retaining ring  24  is used to secure an upper conductor guide wear pad  25  to the upper conductor guide frame  19 . The upper conductor guide ring  24 , the upper conductor guide wear pad  25 , and the upper conductor guide frame  19 , form the upper conductor guide  18 . 
     The lower conductor guide retaining ring  26  is used to secure a lower conductor guide wear pad  22  to the lower conductor guide frame  21 . The lower conductor guide ring  26 , the lower conductor guide wear pad  22 , and the lower conductor guide frame  21 , form the lower conductor guide  20 . 
     Turning now to  FIG. 4  and  FIG. 5 . A tapered bowl tension ring assembly  34  is depicted. The tapered bowl tension ring assembly  34  is disposed on the conductor  10  above the upper conductor guide  18 . 
     The tapered bowl tension ring assembly  34  includes a tension disc  36 . The tension disc  36  is depicted having a tapered center  37  for engaging the tapered collets  38 . The tapered center  37  can be best seen in  FIG. 5 . The tapered center  37  can have a diameter for fitting commonly used riser diameters. 
     The tapered bowl assembly  34  has tapered collets  38  on threads  39 . The threads  39  can be grooves. The threads  39  are for engaging the riser  32  in a secure connection. The tapered collets  38  engage the tension disc  36 . A collet support ring  40  is disposed on the tapered collets  38  for supporting the tapered collets  38 . The well access equipment  13  is depicted connected to the riser  32 . 
       FIG. 7  depicts a side view of the floating vessel  15  for supporting top tension drilling and production risers. The floating vessel  15  supports a first tensioner  1   a  and a second tensioner assembly  1   b . The tensioner assemblies are described in detail below. The floating vessel for drilling operations is in communication with a wellhead. The wellhead is not shown. 
     The floating vessel for drilling operations has a hull  21  with an operations deck  17  disposed on the top of the hull  21 . 
     The second tensioner assembly  1   b  and the first tension assembly  1   a  have a support frame  12 . The support frame  12  has a first beam  42  parallel to a second beam  44 . The first beam  42  and the second beam  44  are secured to the floating vessel  15 . 
     A first piece of well access equipment  13   a  is disposed on the floating vessel  15 . A second piece of well access equipment  13   b  is disposed on the floating vessel. 
       FIG. 8  depicts a flow diagram of an embodiment of the method. The depicted embodiment of the method for supporting top tension drilling and production risers on a floating vessel using a tensioner assembly above the water line of the vessel, starts with step  100 , which includes attaching at least one hydraulic cylinder on a first end to a first position on a floating vessel and on a second end to a tension frame below the first position. 
     After the hydraulic cylinder is attached to the floating vessel the method continues with step  102 , which includes forming a fluid connection between the at least one hydraulic cylinder and at least one primary accumulator. In step  104 , a conductor is disposed between a well head and a piece of well access equipment is secured to a tension frame. 
     After the conductor is secured to the tension frame the method continues by centralizing the conductor in an upper conductor guide frame and a lower conductor guide frame, in step  106 . The upper conductor guide frame and the lower conductor guide frame are secured to the floating vessel. 
     In step  108  the method includes applying tension to a riser within the conductor using the hydraulic cylinder. The conductor slidably supports top tension drilling and production risers. 
     While these embodiments have been described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.