US3531941A - Method of forming a riser for marine pipeline - Google Patents

Description

Oct. 6, 1970 R. P. VINCENT 3,531,941

METHOD OF FORMING A RISER FOR MARINE PIPELINE Filed May 5, 1969 5 Sheets-Sheet 1 8 i g o 11 2 2 r 3 i c: I?

2; l S a i, I W E a a g i INVENTOR.

a I RENIC P. VINCENT V TTORNE Y Oct. 6, 1970 R. P. VINCENT 3,531,941

METHOD OF FORMING A RISER FOR MARINE PIPELINE Filed May 5, 1969 s Sheets-Sheet 2 FIG. 2

INVENTOR.

RENIC P. VINCENT ATTORNEY Oct. 6, 1970 R. P. VINCENT 3,531,941

METHOD OF FORMING A RISER FOR MARINE PIPELINE Filed May 5, 1969 5 Sheets-Sheet 5 FIG. 3

INVENTOR. RENIC P. VINCENT ATTORNEY Oct. 6, 1970 R. P. VINCENT msmob OF Fonu me A RISER FOR MARINE PIPELINE Filed May 5, 1969 5 Sheets-Sheet 4 FIGw INVENTOR. RENIC P; VINCENT BY QWQQ M ATTORNEY R. P. VINCENT 3,531,941

METHOD OF rename A axssa FOR MARINE PIPELINE Oct. 6, 1970 5 Sheets-Sheet 6 Filed May 5, 1969 ATTORNEY:

United States Patent O 3,531,941 METHOD OF FORMING A RISER FOR MARINE PIPELINE Renic P. Vincent, Tulsa, Okla., assignor to Pan American Petroleum Corporation, Tulsa, Okla, a corporation of Delaware Filed May 5, 1969, Ser. No. 822,532 Int. Cl. F16] 1/00; B21d 11 /04 U.S. Cl. 6172.3 4 Claims ABSTRACT OF THE DISCLOSURE This concerns a method of making a riser from a subsea line to the flow system on the deck of a platform set above the body of Water. The end of the pipeline is pivotally supported on the top of the platform. A bending structure is placed on the pipeline at a distance from the top of the platform about equal to the height of the platform from the bottom of the body of water. The pipeline is pulled by exerting force on the bending structure so that the point on the pipe where the bending structure was attached is forcibly positioned adjacent the lower end of one of the support legs of the platform.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the laying of pipelines on the bottom of the body of water. It relates especially to the forming of a riser from such pipeline to the top of a platform supported above the body of water by legs extending to the bottom.

Setting of the invention Recently, the drilling of oil and gas wells has been ex tended into water-covered areas such as the Gulf of Mexico. In relatively shallow water, e.g., about 400 feet or less, these Wells are usually drilled from fixed platforms. A common type of fixed platform is one which supports a drilling structure or producing facility above the surface of the water by long columns of pipe which extend from the platform into the bottom of a body of water. Sometimes these wells are completed on the bottom of the body of water, i.e., the well head is adjacent the bottom, and sometimes they are completed on top of a drilling platform. In either event, the produced oil or gas must be transported to land or to another platform where it may be loaded on a transport vessel. A more frequent way of transporting this oil and gas is by laying pipelines along the bottom of the body of Water. If the well is completed by having the well head on top of the platform, then this well head must be connected to the pipeline. One of the most critical links in the olfshore pipeline system is the vertical segment of pipe or riser which connects the well head on the platform to the pipeline on, the ocean floor. For shallow water, less than about 100' feet, the conventional riser has ordinarily consisted of an L-shaped pipe welded to the section of pipe to be laid on the bottom and the assembly is the set into place alongside the platform by a large crane. The crane operates cooperatively with a lay barge and stinger to lower the line and the L-shaped connection to the bottom progressively as additional joints are added to the vertical leg of the riser. The riser is subsequently clamped at intervals to the platform leg by divers.

Other techniques for installing the riser pipe include the J tube method and the bending shoe concept. In each of these methods, the I tube or the bending shoe method, the I tube and the shoe are each installed in the lower end of the platform. In the I tube concept, a J-shaped 3,531,941 Patented Oct. 6, 1970 conduit with an inside diameter several inches larger than the pipeline 0D. is constructed as an integral part of the platform prior to the platform being installed. The cable is fastened to the surface of the platform through the I tube and connected to a special pulling nose welded on the pipeline. The end of the line is positioned on bottom in alignment with the bell-shaped mouth of the I tube. The pipe is then forced or pulled through the conduit around the bend and to the surface of the platform. The bending shoe concept is slightly different. There, the shoe having a specified curvature is fixed to the bottom of the platform. This bending shoe is used as a fulcrum and curvature limiting device for bending the pipeline in place along one of the legs of the platform.

While these various methods of installing the riser have been used with success, none are fully satisfactory. For example, the J tube concept and the bending shoe concept each require considerable additional structure permanently fixed on the platform. Insofar as setting the riser in deeper water, it is desirable to have a system in which less equipment can be left permanently attached to the drilling platform. My present invention provides such a system.

SUMMARY OF THE INVENTION This is a method of forming a riser pipe from a pipeline laid along the bottom of a body of water to the top of a platform set in such body of water. One end of the pipeline is pivotally supported at the top of the platform. The other end of the pipeline is connected to a barge. A bending structure is placed on the pipeline at a distance from the pivot point which is about equal to the height of the platform from the bottom of the body of water. The bending structure includes an arcuate section which has a radius sufiiciently large so as to prevent buckling of the pipe when force is applied thereto. This bending structure is placed on top and attached to the pipe. A cable extends from the bending structure to a pulley which has previously been attached to the bottom of one of the legs of the platform. The cable extends up to a winch on the surface. The winch takes up on the cable, pulling the structure down toward the pulley. As this structure is pulled downwardly it causes the pipe to bend along the shape of the structure. One end of the bend leads into a vertical section which goes to the top of the pipe, and the other end leads into the pipeline which is laid along the bottom of the body of water.

Various objects and a better understanding of the invention will become apparent from the description which follows when taken in conjunction with the drawings.

DRAWINGS FIG. 1 illustrates a pipeline supported between a floating lay barge and a platform with bending structure attached;

FIG. 2 is similar to FIG. 1 except that the pipeline has been bent about one-half of the distance to its ultimate position;

FIG. 3 illustrates the pipeline after it has been bent to form a riser section alongside the platform;

FIG. 4 illustrates a pivot at the top of the platform for the pipe;

FIG. 5 is a side view of the apparatus of FIG. 4 with pipe inserted in the clamping means;

FIG. 6 illustrates an enlarged view of a preferred bending structure;

FIG. 7 is a view taken along the line 77 of FIG. 6;

and

FIG. 8 illustrates a planned view of the barge, platform and pipeline for explaining the operations when the pipeline and riser are being laid toward the platform.

Attention is first directed to FIG. 1 which illustrates a platform riser pipeline connection device. Shown thereon is a portion of platform 10 having leg 12 which extends through a body of water 14 into the bottom 16. Floating on the body of water is a barge 18. Barge 18 can be any conventional pipeline laying barge for use in laying pipeline in water-covered areas and can be equipped with whatever equipment may be needed for laying pipe. Extending from barge 18 to the deck of platform 10 is a section of pipe 20. It is desired that this pipe 20 be laid along the bottom 16, and a portion of the pipe will form the vertical section of the riser along leg 12 as shown in FIG. 3.

At point 22, pipe 20 is hinged to platform 10. This can comprise a clamp means 24 having shaft 26 which is fixed to platform 10. The clamp then can rotate about axis 26. FIG. 4 is an enlarged view of the clamp. The clamp for the pipe includes jaws 60 which are connected by pivots 62 to arm 64 which is attached to horizontal shaft 26. Jaws 60 can be sized to closely fit pipe 40 and when bolted together by bolts through holes 68, securely fastens the pipe to the jaws. If it is desired that the pipe be able to slip through the jaws 60, the jaws can, of course, be made sufficiently large to permit this. Shaft 26 is supported from platform 10 by support members 66.

Mounted on pipe 20 is a bending structure 28. This structure is positioned along the pipe from pivot 22 a distance D which is approximately the distance from pivot 24 to the bottom of the body of water. One takes into account whether the pipeline is to be laid beneath the bottom in a trench which may be dug and also the expected curvature of the pipe around structure 28. This is all simple mathematics and will not be gone into in detail. Structure 28 has a curved surface 30 which has a radius R which is sufiicient to prevent buckling of the pipe as the bending structure is forced downwardly. The bending structure 28 is preferably fixed to pipe 20 by a releasable clamp. End 70 shows that the curved portion 30 is shaped to receive the pipe to be bent. Bracing 72 is provided to give the structure rigidity. Means are provided for attaching a pulling cable to the main bending structure 30. This includes members 78, shaft 80 extending between the two members, end members 82 for holding shaft 80 in position, arm 74 attached to shaft 80 and eyelet 76 at the end of arm 74. Shaft 80 can be an explosive bolt so that the bending structure can be released from the pipe and cable. A line 71 can extend from the bending structure to the surface so that such structure can be readily recovered.

I will now discuss the means for pulling the bending structure down toward the base of the platform 10. On the base of platform 10 is a pulley 34. This is the only structure in addition to the pipeline which is required to be attached to the platform and left in place after the riser has been established in position. A cable 37 extends from eyelet 76 from member 74 of bending structure 28 downwardly about pulley 34 and up alongside leg 12 of the platform over a second pulley 36 to a winch 38.

In operation the pipeline is either laid toward the platform 10 or laid away from it, that is, by beginning at the platform. I shall first discuss the laying procedure for laying the pipeline 20 beginning from the platform and proceeding outwardly. In this case, barge 18 is used to lay the pipeline from the top of deck 20 outwardly. The end of the pipe is secured by clamp 24 on the platform. Then, sufficient length of pipe is laid so that distance D is satisfied as described above. Then bending structure 28 is attached to the pipeline at the proper position. The cable 37 has previously been threaded down through pulley 34, for example, when pulley 34 was installed.

Pulling bending structure 29 downwardly by cable 37, I provide adequate length of line 20 between bending structure 28 and barge 18 so that there is sufficient length of pipeline to follow good pipeline laying practice for the particular depth of water 14. The lay barge 18 can move backwards to accommodate the extra pipe for making the bend.

We are now ready to proceed with bending of pipeline 20 to form the desired riser pipe. This is accomplished merely by taking up on winch 38 the pull the bending structure 28 down first into an intermediate position, as shown in FIG. 2. It is seen that a part of the pipe is resting on the sea floor. Additional pulling on cable 37 pulls the pipe into the position shown in FIG. 3. There, one can readily see that a portion 40 of the pipe 20 is essentially a vertical section along leg 12. Section 40 curves through portion 42 into the remaining portion of pipe 20. It will ordinarily be necessary to either connect additional lengths of pipe to the pipe on barge 18 as we draw structure 28 downwardly toward pulley 34 or drive the barge 18 back toward the platform to provide for this additional length of pipe required for the bending procedure in forming the riser section. After the pipe has been bent as shown in FIG. 3, the bending structure 28 is released such as by exploding shaft so that the bending structure can be recovered by a line connected by eyelet 71 and used on subsequent jobs. Cable 37 can be severed from eyelet 76 in any of a number of ways so that the cable can be recovered. Thus, all that is left on the platform in addition to the platform itself is sheave 34.

We shall now consider the procedure for laying a pipeline and riser when we are coming into the platform. That is, the pipeline has been laid starting at a point far removed from the platform. Basically, the only difference is that we must use a little difierent way in providing the extra length of pipe which will be consumed by the bend of the pipe after it is bent. Turning to FIG. 8, we see a planned view having platform 10, pipe 20 and bending structure between the platform 10 and barge 18. After the pipe is connected to the platform we wish it to have a straight line indicated by dotted lines 20A. The pipeline section 20 between platform 10 and some point 50 is curved from line 20A providing the required additional length of pipe required for the riser portion of the pipe. It is easy to calculate the distance of pipe 20A from point 50 to the platform point 22A. It is known the horizontal distance from the point 50 to the platform; it is also known what the vertical section of pipe 40 is, as shown in FIG. 3, and the curved section 42. I simply make a mark on pipe 20 at point 50 and add suflicient lengths of pipe so that a length that the pipe in its uncurved position from point 50 to point 22A as indicated by line 20 in FIG. 8 is equivalent to the calculated length. We then attach bending structure 28 to pipe 20 and bend the pipe into place as described above in connection with FIGS. 1, 2 and 3. In this process the pipe 20 is supported from barge 18 by a crane, not shown. As the pipe bending structure 28 is pulled downwardly, the pipe is gently fed from barge 18 to rest on the bottom of the body of water. This prevents the cable from having to drag the pipe 20 laterally across the bottom which might require considerable horsepower. After the riser is in position I prefer to clamp section 40 of FIG. 3 to the leg 12 by clamps 41.

The above embodiments have been described with a certain amount of detail. However, it is to be understood that various modifications can be made therefrom without departing from the spirit or scope of the invention.

I claim:

1. A method of forming a riser pipe extending from the surface of a platform set in a body of water to a pipeline laid along the bottom of said body which comprises:

supporting a pipeline from the top of said platform at one end and to a barge on the other end;

placing a bending structure on said pipeline at a position a distance from the top of said platform about equal to the height of said platform from said bottom, said bending structure including an arcuate structure having a radius sufiicient to prevent buckling of the of pivotally connecting one end of said pipeline to said pipe when force is applied thereto; upper end of said platform, and pulling said structure down toward the base of said maintaining said pipe in tension while said bending platform whereby said pipeline extends vertically stnlcture is pulled downwardly.

downwardly from the top of said platform and curves 5 into the horizontal pipe at the bottom of said body References Cited Water UNITED STATES PATENTS 2. A method as defined in claim 1 including the step 2 981 074 4/1961 Wilder 61 72 3 X of fixing said bending structure to said pipeline at said 3466882 9/1969 &-; 1 723 position. 10 l i 3. A method as defined in claim 1 including the step of JACOB 'SHAPIRO, Primary Examiner pivotally connecting said pipeline to the upper end of said platform prior to pulling said bending structure to the base thereof. 72-318 4. A method as defined in claim 1 including the steps 15

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