GB1559388A - Marine riser conduit section coupling means - Google Patents

Description

(54) MARINE RISER CONDUIT SECTION COUPLING MEANS (71) WE, REGAN OFFSHORE IN TERNATIONAL, INC., a corporation organized and existing under the laws of the State of California, United States of America, of 21000 Normandie Avenue, Torrance, California 90501, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement : This invention relates generally to marine riser conduit section coupling means which are adapted to withstand high riser tension and bending loads in deep sub sea well drilling and production operations. More specifically, the present invention relates to a construction of coupling means for optimizing the distribution of tension and bending loads through the coupling when employed in association with a marine riser conduit run in sections from a floating vessel to a very deep sub sea well.

Heretofore it has been common to run marine risers from floating vessels or platforms to sub sea well heads for various drilling and production operations. The marine riser comprises a plurality of conduit sections which are assemble together on the vessel or platform and run by known means from the vessel down to the well. As deeper and deeper well drilling and production operations have been undertaken, the tension and bending loads imparted to the riser and its conduit sections have been increasing. It has been found that the heretofore conventionally used coupling means for fastening successive riser conduit sections together may be in adequate to withstand these very high loads. Specifically, prior coupling means which employ a plurality of movable dog means on one mating member and a peripheral groove on the other mating member tend to concentrate the stresses imparted to the coupling under these tension and bending loads in a central area of the coupling where the movable dog members and mating groove means are provided, respectively.

It has therefore been recognized that an improved coupling means is needed for the specific situation of very deep well drilling and production operations in association with a marine riser run in successive joined sections to a very deep well head According to the present invention there is provided a marine riser conduit section coupling means adapted to withstand high riser tension and bending loads in deep sub sea well drilling and production operations comprising : upper and lower coupling members, each connected to a marine conduit section with an internal bore in the coupling member aligned with the bore of the associated conduit section and presenting mutually opposed end flanges having substantially flat end surfaces in abutting relation, fastening means for securing said coupling members together by said end flanges with said end surfaces m abutting relation to hold said conduit sections interconnected during sub sea well operations and the concomitant bending movement of the riser sections, and means on each of said coupling members for achieving a virtually optimum even distribution of bending stress in said coupling members across said abutting end flanges due to such riser bending movement and the tension and bending loads imparted to the couplings thereby, comprising the provision of an outer surface configuration for each said coupling members comprising an effectively continuous outwardly divergent arcuate surface extending circumferentially about substantially the entire outer surface of each coupling member from one axial extremity thereof adjacent the associated conduit section to an opposite extremity thereof adjacent outer marginal areas of the flange.

The arcuate surface of one of the coupling members may be interrupted by shallow bolt head receiving recesses to accommodate bolts forming the fastening means, and means are provided for preventing the inadvertent removal of a bolt from the associated flange even though it has been disconnected from the associated flange.

Locating means are also provided in accordance with the present invention for orienting the two coupling members to one another preparatory to operation of the fastening means to hold the coupling members in a predetermined relative positioning thereof.

The invention will be further described with reference to the accompanying drawings, in which : Figure 1 is a side elevational view of a sub sea wellhead, a vessel on the surface of the sea and a string of maring riser conduit sections extending between the vessel and the wellhead, with the conduit sections coupled by a preferred exemplary embodiment of the marine riser conduit section coupling in accordance with the present invention ; Figure 2 is an enlarged section view of the apparatus of Figure 1 taken therein along the plane II-II showing the exemplary embodiment of coupling in plan view ; Figure 3 is a vertical section view through the coupling and riser conduit sections of Figures 1 and 2 taken in Figure 2 along the plane III-III ; Figure 4 is a detail view of a portion of the coupling of Figure 3 showing an exemplary embodiment of fastening means for holding the coupling members together ; Figure 5 is a detail view of the coupling of Figure 3 showing an exemplary embodiment of locating pin means for aligning the coupling members in a predetermined relationship preparatory to being fastened together ; and Figure 6 is a detail view of the preferred exemplary embodiment of coupling as in Figure 4 showing the preferred exemplary embodiment of fastening means in an unfastened condition.

Referring firstly to Figure 1 of the drawings, a typical sub sea oil well installation is shown for purposes of illustrating the environment of the exemplary embodiment in marine riser conduit section coupling of the present invention. An exemplary floating vessel, indicated generally at 10. is shown floating on the surface of the sea 11 overa wellhead assembly 12 situated at the ocean floor 13. The marine riser conduit 14 is shown run from the floating vessel down to the wellhead 12, the latter being provided with conventional blow out preventers 15 and riser connector 16.

In the exemplary embodiment of Figure 1, a pair of guide lines 17 and 18 are shown run from the floating vessel to the sub sea wellhead for use in guiding the riser conduit sections through the well head from the vessel derrick 19 through the conventional well 20 of the vessel. A rotary table 21 is shown on the vessel over well 20. Marine riser casing sections 22-26 are shown connected by coupling means in accordance with the present invention such means including an upper connector member 27, positioned on the lower end of a conduit section, and a lower connector member 28, positioned on an upper end of a preceding conduit section, such as illustrated in association with sections 22 and 23 in Figure 1.

Guide sleeves 29 are shown mounted to the connector members for use in guiding them and the associated marine riser conduit sections from the vessel to the well in a manner generally known heretofore.

The preferred exemplary embodiment of marine riser conduit section coupling means in accordance with the present invention is illustrated in detail in Figures 2 through 6.

Referring initially to Figures 2 and 3, the preferred exemplary embodiment of connector means inclues the aforementioned upper connector member 27 and lower connector member 28 mounted to their respective conduit sections 22 and 23, respectively, by. appropriate means such as welds 30 and 33. Upper connector member 27, as seen in Figure 3, has its inner bore 32 aligned and connected to the associated riser section bore 31 by means of weld 30.

Similarily, lower connector member 28 has its inner bore 34 aligned and connected to the associated riser section bore 35 by weld 33. When in assemble relation as illustrated in Figure 3, the connector members may have their bores sealed from the surrounding environment by means of an appropriate annular seal means 36 located between flanges 37 and 38 of the respective coupling members 27 and 28.

As is particularly contemplated within the present invention, each riser conduit section coupling member is provided with an exterior surface configuration which is designed in a manner to allow the coupling to withstand the high riser tension and bending loads normally encountered in deep sub sea well drilling and production operations in a manner not heretofore attainable. Specifically. in accordance with the present invention, the outer surface configuration for each of the coupling members is provided in the form of an effectively continuous arcuate surface extending about substantially the entire outer surface of each coupling member from one extremity thereof adjacent the associated conduit section to the other extremity thereof adjacent outer marginal areas of the coupling member flanges 37 and 38, as will now be described in detail.

As seen in Figure 3, each coupling member 27 and 28 has a base formed by the associated flanges 37 and 38 respectively.

The opposite extremity of each coupling member comprises a tubular portion or extremity 39 and 40, respectively. Extend ing effectively continuously from the extremities, 39 and 40 of each coupling, to the outer marginal areas of each flange 37 and 38, respectively, are the effectively continuous arcuate surfaces 41 and 42, respectively. Surfaces 41 and 42 are arcuate, curved or non-linear, when viewed in cross section in Figure 3 and extend circumferentially around the exterior of each of the members. By so providing the exterior configuration of each coupling member, its resistance to failure under the high riser tension and bending loads normally imparted to a sub sea marine riser conduit coupling are effectively distributed through the coupling without causing stress concentration in any particular portions thereof as is true in the prior art couplings employed in these types of risers.

Fastening means are provided for securing the coupling members together by their respective flanges to hold the coupling sections interconnected during sub sea well operations. As seen in Figures 4 and 6, the preferred exemplary embodiment of fasten mg means includes the provision of bolts on one of the coupling members adapted to be screwed into mating means on the flange of the other coupling member. Specifically, coupling member 27 has its effectively con tinuous surface 41 interrupted minimally by recesses 43 for receiving the fastening means indicated generally at 50. A bore 44 is provided centrally of each recess 43 with only an upper portion thereof provided with screw threads 45 to prevent inadvertent dislodging of a retracted bolt as seen in Figure 6. The mating flange of the other coupling member 28 is provided with a screw threaded bore. 46 which receives a screw threaded sleeve 47. Therefore, fastening means 50 including bolt 51, having shank 52, hexhead 53 and screw threaded body portion 54 adjacent to its lower end may be turned down relative to coupling member 27 into the screw threaded sleeve 46 to retain the coupling members together, the hexhead 53 having a peripheral flange adapted to seat within recess 43 as illustrated.

In order to provide for a predetermined orientation of the coupling members 27 and 28 to one another prior to their being fastened by the exemplary fastening means, indicated generally at 50, means are provided for locating the two coupling members relative to one another preparatory to operating the fastening means. In the exemplary embodiment, such locating means include the provision of locating pins, as pin 55 in Figure 5, which have a screw threaded body 56 secured to the flange of member 28 and a head portion 57 protruding axially of the coupling member. An appropriate mating blind bore 58 may be provided in the flange of the other connector member 27 in three spaced locations, as seen in Figure 2, so as to mate with the associated pins 55 in only one predetermined relative orientation.

Provision may also be made in the conduit coupling means of the present invention to provide for the connection and orientation of choke and kill lines run from the vessel to the well. As seen in Figure 3, a flow line type coupling may be provided in the form of line couplings 60 and 61 mounted on the connector members 27 and 28, respectively.

Associated flow lines 62 and 65 may be provided with appropriate end fittings 63 and 64 for a stab-connect engagement with the associated line couplings 60 and 61 in otherwise conventional manner.

Claims (6)

WHAT WE CLAIM IS :

1. A marine riser conduit section coupling means adapted to withstand high riser tension and bending loads in deep sub sea well drilling and production operations comprising : upper and lower coupling members, each connected to a marine conduit section with an internal bore in the coupling member aligned with the bore of the associated conduit section and presenting mutually opposed end flanges having substantially flat end surfaces in abutting relation, fastening means for securing said coupling members together by said end flanges with said end surfaces in abutting relation to hold said conduit sections interconnected during sub sea well operations and the concomitant bending movement of the riser sections ; and means on each of said coupling members for achieving a virtually optimum even distribution of bending stress in said coupling members across said abutting end flanges due to such riser bending movement and the tension and bending loads imparted to the couplings thereby comprising the provision of an outer surface configuration for each said coupling members comprising an effectively continuous outwardly divergent arcuate surface extending circumferentially about substantially the entire outer surface of each coupling member from one axial extremity thereof adjacent the associated conduit section to an opposite extrem- ity thereof adjacent outer marginal areas of the flange.

2. The marine riser conduit section coupling of claim t wherein : said arcuate surface of one of said coupling members is interrupted periodically by shallow bolt head receiving recess to accommodate bolt means of said fastening means and said fastening means comprises a plurality of bolt means.

3. The marine riser conduit section coupling of claim 2 wherein said one of said coupling members is provided with a respective bolt receivifig bore generally concentric with each of said recess with zipper portions only of each said bore being screw threaded to facilitate retention of a bolt threaded through ; and ad associated bolt means haing a shank screw threaded only adjacent a lower end to facilitate retention of such bolt on the coupling member once it is threaded through said bolt receiving bore upper portions preparatory to evenfually being secured to a mating screw threaded bore of the lower coupling member.

4. The marine riser conduit section coupling of claim 1 wherein : a plurality of locaitng pin means are provided on the end surface of the flange of said one of the coupling members fading toward the other of said members ; a like plurality of pin receiving bores are provided oh the end surface of the itange of the other of the coupling members facing said one coupling member ftange ; and said locating pin means and piri receiving bores are so provided that said coupting members may be oriented to each other with said pin means and bores mating in only one predetermined relative orienta- tion.

5. A marine riser conduit section coupling substantially as hereinbefore described with reference to the accompanying drawings.

6. A marine riser comprising a plurality of conduit sections coupled together by means of couplings each in accordance with any one of the preceding claims.