Patent Publication Number: US-2016230475-A1

Title: Synatic foam design modifications

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application Ser. No. 62/113,056, filed Feb. 6, 2015, the contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The invention relates to the field of buoyancy modules, and in particular to driller riser buoyancy modules. 
     BACKGROUND 
     Driller riser buoyancy modules are used for providing a conduit for various lines of a drill string between the oil rig and ocean floor. 
     Driller riser buoyancy modules for subsea riser pipes are often made of syntactic foam solid cores covered with a tough exterior shell. A conventional driller riser buoyancy module includes two detachable complementary halves each having a complementary co-axially extending primary central opening for a main flow line and a plurality of complementary axially extending secondary openings for receiving auxiliary lines. Each opposite detachable complementary half comprises foam (e.g., syntactic) bounded by an interior surface and a rugged exterior shell. For example, a conventional drilling riser buoyancy module is disclosed U.S. Pat. No. 7,628,665. Each driller riser buoyancy half disclosed in this prior art patent includes a semi-cylindrical cross-sectional exterior surface, so when the halves are combined the cross-sectional exterior of the buoyancy module is cylindrical. An example of a buoyancy module  10  having a cylindrical cross-sectional exterior is illustrated in  FIG. 1 . 
       FIG. 2  is a cross-sectional illustration of a second known driller riser buoyancy module  12 . Notably, the exterior of each detachable complementary half  14 ,  16  includes a flat segment  18 ,  20 , respectively, and partially-cylindrical exterior surface segments  22 - 25 . The flat segments  18 ,  20  provide surfaces that the buoyancy module rests onto when stacked (e.g., on a ship). This configuration is often referred to as a 60-degree flat, and is conventional for a riser system with five auxiliary lines. 
     A problem with the driller riser buoyancy module  12  illustrated in  FIG. 2  is that when a relatively large number of riser joints are stacked (e.g., 9 or more riser joints laid atop one another substantially horizontally), risers on the bottom of the stack are stressed in compression and the compressive forces may cause damage to the riser (e.g., cracking of the foam). 
     There is a need for an improved driller riser buoyancy module. 
     BRIEF SUMMARY 
     A drilling riser buoyancy module comprises two opposite detachable complementary halves each having a complementary co-axially extending primary central opening for a main flow line and first and second complementary axially extending secondary openings radially adjacent and on opposite sides of the primary central opening for receiving and holding first and second auxiliary lines, respectively. Each opposite detachable complementary half comprising syntactic foam bounded by an interior surface and an exterior surface. A first of the opposite detachable complementary halves includes a third co-axial auxiliary line opening and a second of the opposite detachable complementary halves includes a fourth co-axial auxiliary line opening and a fifth co-axial auxiliary line opening. A portion of the interior surfaces of complementary halves are configured and arranged to contact each another. Each exterior surface of the two halves comprises (i) a first flat exterior surface segment radially opposite an associated first flat exterior surface segment of the other half, (ii) a second flat exterior surface segment radially opposite an associated second flat exterior surface segment of the other half, where the second flat exterior surface segment is circumferentially adjacent to the first flat exterior surface segment and (iii) a plurality of partially-cylindrical exterior surface segments whose aggregate circumferential length is greater than aggregate length of the first and second flat exterior surface segments of the two opposite detachable complementary halves. 
     The first and second of complementary axially extending secondary openings may be substantially semi-cylindrical. 
     A first of the two opposite detachable complementary halves includes a first axial opening formed in the interior surface of the first of the two opposite detachable complementary halves. 
     A second of the two opposite detachable complementary halves includes a second axial opening formed in the interior surface of the second of the two opposite detachable complementary halves and a third axial opening formed in the interior surface of the second of the two opposite detachable complementary halves. 
     A drilling riser buoyancy module comprises two opposite detachable complementary halves each having complementary co-axially extending primary central opening for a main flow line and at least five complementary axially extending secondary openings for receiving and holding auxiliary lines. Each opposite detachable complementary half comprising foam bounded by an interior surface and an exterior surface. A portion of the interior surfaces of complementary halves are configured and arranged to contact each another. Each exterior surface of the two halves comprises (i) a first flat exterior surface segment radially opposite an associated first flat exterior surface segment of the other half, (ii) a second flat exterior surface segment radially opposite an associated second flat exterior surface segment of the other half, where the second flat exterior surface segment is circumferentially adjacent to the first flat exterior surface segment and (iii) a plurality of partially-cylindrical exterior surface segments whose aggregate circumferential length is greater than aggregate length of the first and second flat exterior surface segments of the two opposite detachable complementary halves. 
     These and other objects, features and advantages of the present invention will become apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional illustration of a first prior art buoyancy module; 
         FIG. 2  is a cross sectional illustration of a second prior art buoyancy module; and 
         FIG. 3  is a cross sectional illustration of an improved buoyancy module; 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 3  is a cross sectional illustration of a drilling riser buoyancy module  30 . The module  30  includes two opposite detachable complementary halves  32 ,  34 . The first detachable complementary half  32  includes a first primary semi-cylindrical opening  36  formed by a plurality of curved sidewalls segments  37   a ,  37   b  each having a radius R. The second detachable complementary half  34  includes a second primary semi-cylindrical opening  38  formed by a plurality of curved sidewalls segments  39   a ,  39   b  and  39   c  each having a radius R. The first and second primary semi-cylindrical openings  36 ,  38  formed by the sidewall segments  37   a ,  37   b ,  39   a ,  39   b  and  39   c  form a primary central opening  40  sized to surround a riser pipe  41 . 
     The first detachable complementary half  32  includes a first axially extending semi-cylindrical secondary opening  42  radially adjacent the primary central opening  40 . The first detachable complementary halve  32  also includes a second axially extending semi-cylindrical secondary opening  44  radially adjacent and on opposite sides of the primary central opening  40 . The secondary openings  42 ,  44  are radially separated by the central opening  40 . The second detachable complementary half  34  includes a third axially extending semi-cylindrical secondary opening  46  radially adjacent to the primary central opening  40 . The second detachable complementary half  32  also includes a fourth axially extending semi-cylindrical secondary opening  48  radially adjacent to the primary central opening  40 . The first and third semi-cylindrical secondary openings  42 ,  46  cooperate to form a first accessory opening  50 , and the second and fourth semi-cylindrical openings  44 ,  48  cooperate to form a second accessory opening  52 . The first and second accessary openings  50 ,  52  are radially separated by the central opening  40 . 
     The first detachable complementary half  32  also includes an axially extending third accessary opening  54 . The second detachable complementary half  34  includes axially extending fourth and fifth accessary openings  56 ,  58 . 
     The first detachable complementary half  32  comprises syntactic foam bounded by the sidewall segments  37   a ,  37   b  and a protective exterior surface  60 . Interior surface of the first detachable complementary halve  32  forms the third accessory opening  54 . The second detachable complementary halve  34  comprises syntactic foam bounded by sidewall segments  39   a ,  39   b  and  39   c  and a protective exterior surface  62 . The interior surface of complementary halve  34  partially forms the fourth and fifth accessary openings  56 ,  58 . 
     As shown in  FIG. 3 , a portion of the interior surfaces of the complementary halves  32 ,  34  are configured and arranged to contact each another, for example at  64 , and the complementary halves  32 ,  34  may be held in contact with fasteners (e.g., bolts) and straps (not shown). 
     The exterior surfaces  60 ,  62  of the detachable complementary halves  32 ,  34 , respectively, may comprise a plurality of curved and straight segments. For example, referring to  FIG. 3 , the first exterior surface  60  may include a first flat exterior surface segment  66  radially opposite an associated first flat exterior surface segment  68  of the second exterior surface  62 . The first exterior surface  60  may also include a second flat exterior surface segment  70  radially opposite an associated second flat exterior surface segment  72  of the other half, where the second flat exterior surface segments  70 ,  72  are circumferentially adjacent to the first flat exterior surface segments  66 ,  68  respectively. 
     In addition, the first exterior surface  60  also includes a plurality of curved segments  74 ,  76 . The segments may have a radius R from the longitudinal center line of the drilling riser buoyancy module  30 . The second exterior surface  60  also includes a plurality of curved segments  78 ,  80 . These curved segments may also be characterized as having a radius R from the longitudinal center line of the drilling riser buoyancy module  30 . The aggregate circumferential length of the plurality of partially-cylindrical exterior surface segments  74 ,  76 ,  78  and  80  may be greater than aggregate length of the flat exterior surface segments  66 ,  68 ,  70  and  72 . 
     Although the present invention has been shown and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the faun and detail thereof, may be made therein, without departing from the spirit and scope of the invention.