Method And Apparatus For Installing Offshore Flow Lines

Abstract

Offshore flow lines are installed on an offshore structure in a body of water by pulling (and/or pushing) a flow line downwardly from water surface through a curved tubular member until one end of the flow line is available to water surface at a horizontally spaced-apart point from said structure. The flow line may be arranged in the curved tubular member when the offshore structure is built and the flow line pulled and/or pushed through it when the structure is located in a vertical position in a body of water.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 797,749 entitled "Method for Installing Offshore Flow Lines" filed Feb. 10, 1969, for Jamie F. Matthews, Jr., now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to the installation of a flow line on an offshore structure such as one used for oil and/or gas wells. More particularly, the invention is concerned with pulling and/or pushing a flow line downwardly from water surface. In other aspects, the invention is concerned with running a flow line downwardly from water surface through a curved conduit.

2. Description of the Prior Art

It is known to install a flow line on an offshore structure by pulling a flow line upwardly from water bottom through a curved conduit. This is the so-called J-tube method which involves pulling the flow line from a barge by a wire line, cable, and the like up through a J-tube by force applied on the line from the deck of an offshore platform. This method is disadvantageous because the pull required is so great, if not properly controlled, it may cause at least partial failure of the platform. Furthermore, the pull must be sufficient to overcome the weight of the flow line running through the tube, the resistance of the pipe against being bent to conform to the curvature of the J-tube, and the friction between the outer surface of the flow line and the inner surface of the J-tube, of these three forces, friction is the greatest. THe sum of these forces is so great that the J-tube method is currently limited to installation of flow lines of 10 inch maximum diameter. The present invention overcomes these disadvantages and, in fact, utilizes the weight of the pipe to assist in the operation, reduces friction, and allows installation of flow lines of large diameter than heretofore possible with the J-tube MOreover, the new method eliminates or reduces the use of divers since all or most of the operations may be conducted from water surface.

The following U.S. patents were considered in connection with this invention: U.S. Pat. Nos. 3,258,928; U.S. Pat. No. 3,331,212; 3,434,296;

BRIEF DESCRIPTION OF THE DRAWING

The present invention will be further illustrated by reference to the drawing in which:

FIG. 1 is a view showing the initial steps of installing a flow line on a submerged structure;

FIG. 2 illustrates the flow line being pulled downwardly to a submerged structure from water surfaces;

FIG. 3 is a showing of connecting flow line to a wellhead on the submerged structure;

FIG. 4 illustrates he invention as applied on a structure extending above water surface;

FIG. 5 is a modification of the invention in which a submerged conduit is employed on a structure extending above water surface and the flow line is pulled and/or pushed through the conduit;

FIG. 6 is an elevational view of an offshore structure with the deck removed;

FIG. 7 is a plan view of the structure of FIG. 6;

FIG. 8 is an enlarged detail of the lower end of the riser of FIG. 7;

FIG. 9 illustrates another means for removing curvature from the flow line; and

FIG. 10 is a sectional view along line 10-10 of FIG. 9

SUMMARY OF THE INVENTION

The present invention may be briefly described and summarized as involving a method of installing a flow line on an offshore structure, either submerged or extending above water level, by running a flow line downwardly through an open-ended curved tubular conduit on the offshore structure until both ends are accessible from water surface. This is accomplished by pulling and/or pushing the low line downwardly from water surface through the curved conduit until the flow line is pulled and/or pushed to an accessible location horizontally spaced from the offshore structure. The flow line is preferably pulled through the tubular conduit by a cable or the like threaded through the tubular conduit.

DESCRIPTION OF THE PREFERRED MODE AND EMBODIMENTS WITH RESPECT TO THE DRAWING

Referring now to the drawing and particularly to FIG. 1, numeral 11 designates a body of water having a bottom 12 and surface 13 on which is floating a work vessel 14 and a lay barge 15. The work vessel 14 is provided with a hoisting mechanism 16 which may be a drilling rig, and the lay barge 15 is provided with a rack 17 of flow line pipe and a hoisting mechanism 18 which may be a suitable winch. Actually in FIG. 1, the distance of the lay barge 15 and platform 21 from the work vessel 14 is much greater than is shown. The relative distance between the two vessels should be such that the pull is more nearly in a horizontal position than that shown.

Arranged on water bottom 12 and securely anchored thereto by members 19 which may be cross braced with cross bracing 20 is submerged platform 21. The members 19 extend into and are securely anchored in water bottom 12 as shown.

As well 22 has been drilled to penetrate a productive subsurface formation which may contain oil and/or gas and extends to the platform 21 and is provided with a wellhead 23 including a suitable valve mechanism.

Prior to installing the platform 21, it is equipped with a curved tubular 24 which has a flared open end 25 and a flared open end 26 on the platform 21. A cable, chain, wire line, or the like, 27 is threaded through the tubular conduit 24 and extends into and is connected with the winch 18. The other ends of cable 27 extends to the work vessel 14 and is connected to the lower end of a fabricated flow line pipe 28 by means of a connector plug 28a, As the flow line is lowered through vessel 14, it is it the same time pulled into and through the curved pipe 24 by means of the winch 18.

As shown more clearly in FIG. 2, the tubular flow line 28 connected to line 27 has been pulled through tubular conduit 24 from the vessel 14 by suitable force exerted by the winch 18 pulling on the line 27.

In FIG. 3, the flow line 28 has been pulled from the vessel 14 through the tubular conduit 24 by line 27 so that the end provided with plug connector 28a, is raised from the surface of the water and is adjacent the lay barge 15. At this time a clamping means 40 is applied to support the pipe 28 and the plug conductor 28a, removed from the end of the pipe.

It will also be seen in FIG. 3, that a wellhead connection 29 has been lowered onto the end of flow line 28 by wire lines 30 connecting with the work vessel 14 and the flared end 26 of tubular conduit 24; a connection 31 being remotely controlled from the vessel 14 with the wellhead 23, connecting to the well pipe 23a, through conductor pipe 23b.

Thus, it will be seen with the description taken with the drawing and with reference to FIGS. 1--3 that a flow line may be installed and connected to a well without resort to divers. Thereafter, lengths of pipe may be added to the end 41 to extend the flow line to a suitable terminal for oil and/or gas and the like.

Referring to FIG. 4, a platform 50 supported above the water surface 13 on members 51 suitably cross braced with cross bracing 52 has a drilling rig 53 including hoisting means 54 thereon located on a platform 50. In this particular instance, a plurality of wells 55 have been drilled from the platform 50 by moving the drilling rig 53. In this particular instance, a flow line 56 connected by line 57 to the hoisting means 54 has been pulled through a curved tubular conduit 58 having flared ends 59 by means of the winch 18 connected by line 27 to the end 41 of flow line 56. The hoisting line 57 is used to connect successive lengths of pipe during the pulling operation. In this particular embodiment, the work vessel 14 has been replaced by the platform 50.

Once the flow line 56 has been pulled through the tubular member 58, it then may be connected to the wellheads 60 of the several wells 55 drilled from platform 50 for production of oil through the flow line 56.

It is within the purview of the present invention to push as well as pull through the tubular conduit and this is best illustrated in FIG. 5 to which reference is now had. In this particular instance, platform 50, similar to that shown in FIG. 4, is supported by members 51. A submerged curved tubular conduit 70 is arranged on the platform 50 below water level 13 and above water bottom 12. Line 27 connects to a tubular flow line 28 by suitable plugged connection means 28a. In this particular mode and embodiment, the flow line 28 is both pulled and pushed through the tubular member 70 and this is accomplished by pulling on the line 27 and exerting downward force on the tubular flow line 28. This is achieved by attaching a connection member 73 to the flow line 28 and in turn connecting it by lines 74 running over sheaves 75 to a hoisting mechanism such as 54 shown in FIG. 4. By pulling on lines 74, a downward push or force is exerted on the flow line 28 at the same time tension is exerted by line 27 which causes a combined push and pull on the flow line 28 which is quite beneficial as will be explained further.

Thus, in accordance with the present invention, with reference to FIGS. 1--4, inclusive, gravity which heretofore had to be overcome to lift the weight of the flow line now works to assist the operation. More importantly, however, than the weight is the effect of the simultaneous pushing and pulling of the flow line, as shown in FIG. 5, in reducing the friction in the tubular conduit 70 since a flow line being moved or run in tubular conduit 70 or the like by pulling force alone tends to bind against the throat of the tubular conduit and severe friction is generated. The pushing force on the same flow line tends to relieve this pressure and friction is thereby reduced. Similarly, the pulling force tends to reduce friction generated by the pushing force. THe reaction of both on the flow line results in friction resistance which has been reduced and is much less than if either force were acting alone. In accordance with the present invention with a pushing force and with reduced friction, it is now possible to install flow lines of a larger diameter than has been possible heretofore. This may be accomplished with substantially reduced danger on parting the pulling cable and with less danger of overstressing; if the pushing force supplied by gravity is insufficient it may be supplied as shown in FIG. 5.

The present invention allows the installation of connection means on the platform end of the flow line before it is lowered into the water as shown in FIG. 3. Otherwise, for an underwater platform this would require pulling the flow line into place upwardly, and cutting the pulling head by a welding torch or other cutting means such as a mechanical cutter.

Referring now to FIGS. 6 to 9 inclusive, in which another mode of the present invention is illustrated, numeral 80 illustrates an offshore structure, provided with a curved conduit 81, arranged in a vertical position in a body of water 11. The curved conduit 81 has its lower end 82 at least adjacent to the bottom of the body of water and its upper end 83 at least adjacent the upper end of the structure 80. The structure 80 is provided with legs 84 and crossmembers 85 which may be suitably braced as shown in FIGS. 6 and 7 by members 86 and 87. The conduit 81 has a flow line 88 extending through it which is provided on its lower end with a pulling head 89 which is shown in more detail in FIG. 8. The pulling head 89 is connected to the flow line 88 by flange 90 and blind flange 91 by bolts 92. A suitable cable may be connected to the pulling head 89 by padeye 93 for pulling the flow line 88 through the conduit 81.

It will be noted in FIG. 6 that the conduit 81 has a first section, designated by the numeral 94, which has a curvature with a radius in one direction, whereas the section 95 between the markers A and B has a reverse curvature or radius. The purpose of the reverse curvature is to remove residual curvature or set from the flow line 88 as it is pulled through the conduit 81.

The removal of residual curvature or set of flow line 88 may be accomplished by other means such as illustrated in FIGS. 8,9 and 10 wherein the conduit 81 is provided adjacent its lower end with rollers 97 in the area 95 between markers A and B. As shown in FIG. 10, the rollers 97 extend into the interior of conduit 81 through slots 96 and are pivoted on axles 98 carried on yokes or plates 99. A roller 97a, located on the underside of conduit 81 may extend deeper into the conduit than the rollers 97. As the flow line 88 passes between these three rollers 97, 97a, and 97 it is forced into an opposite curvature and thus will be straightened, removing the residual curve. The rollers in the area 95 function as a means for straightening the flow line as it passes through the conduit 81.

Other rollers 100, which are identical to the rollers 97 may be positioned along the other section of conduit 81 to contact the flow line 81 and reduce friction as the flow line is moved through the conduit. However, rollers 100 may be used wherever desired on the conduit 81. The location and number of rollers may vary with the size of the conduit 81, the flow line 88 and the radius of the conduit 81. Three rollers will usually be sufficient but more or less may be used. AS a general rule the rollers may be placed wherever the flow line 88 tends to contact the interior of conduit 81. Anywhere from one to 10 or more spaced-apart horizontally and vertically spaced-apart rollers may be used.

In the practice of the present invention, as illustrated in FIGS. 6 to 9, flow line 88 is installed in the conduit 81 during land fabrication of the structure 80 and may be pulled through the conduit 81 as has been described. Once the structure is located vertically in body of water 11, as shown in FIG. 6, and difficulty is experienced in pulling the flow line 88 through the conduit 81, then the flanges 90 and 91 may be unbolted and an underwater connection made to an extended flow line such as 56, shown in FIG. 4, either through use of divers or remotely with means well known in the art.

However, it has been found that the application of pushing force acting in conjunction with a pulling force in accordance with the present invention, as shown in and described with respect to FIG. 5, reduces the total force required to move the flow line downwardly through the conduit by almost 30 percent of that required in pulling the flow line upwardly through the conduit It has also been found that if the flow line 88 is lubricated, the force required to pull and push it downwardly through the conduit 81 is reduced even further. For example, a length of 1 1/2 pipe or tubing of the same size was then coated with a heavy fibrous grease such as used on heavy gears and/or on heavy duty equipment was pulled and pushed through a conduit such as 81 with the total force reduced by 35 percent due to the reduction of friction. It is, therefore, contemplated in the practice of the present invention that at least one of the contact surfaces between the internal wall of the conduit and the outer wall of the flow line may be coated with a suitable lubricant such as a heavy grease which may be used to reduce friction and to facilitate the pulling and pushing of a flow line through the conduit. The combined effect of applying pushing as well as pulling and use of lubricant has been to reduce the total force required by 55 percent. It will be noted that the percentages given before are not directly additive. In short, in the practice of the present invention, it is contemplated that the interior of the conduit, or the exterior of the flow line, or both of them, may be coated with a suitable lubricant or grease to reduce total force required in pushing and/or pulling the flow line down through the conduit. When lubrication is used, rollers 97 may not be necessary. When rollers 97 are used, the only lubrication which may be required is for the axles 98. Of course rollers and lubrication may be used but both may under some conditions be dispensed with.

THe rollers provide two functions: (1) they facilitate movement through the conduit; and (2) they eliminate or remove residual curvature or set, both of which are quite advantageous and useful.

In accordance with the present invention, an underwater platform with a completed well or wells may be connected to a production manifold with a floating drill rig in position over the top end of the curved tubular conduit which may be installed during fabrication on land. A work barge may be substituted for a drilling vessel. In either instance a steel cable or chain is run through the tubular conduit to the drilling rig or hoisting means and the other end secured to the pipe laying barge in which sections of flow line pipe are racked. Thus, as illustrated, several sections of flow line pipe may be sequentially joined as shown on the drill floor of the rig as the flow line pipe is lowered into the curved tubular member and the weight thereof and the tension applied thereon causes the flow line pipe to move downwardly through the tubular member and to be pulled to the barge 15. The set or curvature taken by the flow line in passing through the curved tubular member is removed by reverse curvature as it leaves the curved tubular member.

Thus, in accordance with the present invention, flow lines are run downwardly rather than upwardly through a tubular member by pulling and pushing on the ends thereof which results in improved operations as has been brought out hereinbefore which results in numerous advantages. Thus, the present invention is quite important and useful and allows the obtaining of new and improved results not obvious from the prior art. The present invention is, therefore, quite advantageous and useful and allows the obtaining of economic and safety advantages not possible heretofore.

Claims

The nature and objects of the present invention having been completely described and illustrated and the best mode contemplated set forth, what I wish to claim as new and useful and secure by Letters Patent is:

1. A method for installing a flow line having first and second ends on an offshore structure in a body of water wherein said structure is provided with an open-ended curved tubular conduit having a first end at least adjacent water bottom and a second end extending upwardly on said structure which comprises:

positioning a flexible member through said tubular conduit with the first end of said flexible member extending from the first end of said conduit to water surface at a horizontally spaced apart point from said structure and the second end of the flexible member extending from the second end of said conduit;

attaching the first end of said flow line to the second end of said flexible member; and

then pulling said flexible member and the flow line downwardly through said conduit until the first end of said flow line extends from the first end of said conduit to said point horizontally spaced apart from said structure.

2. A method in accordance with claim 1 in which the offshore structure is submerged.

3. A method in accordance with claim 1 in which the offshore structure extends at least to water surface.

4. A method in accordance with claim 1 in which lengths of pipe are added to the first end of said flow line at least adjacent water surface to increase the length thereof.

5. A method in accordance with claim 1, in which the flexible member is a cable.

6. A method in accordance with claim 1 in which the flexible member is a chain.

7. A method in accordance with claim 1 in which the flexible member and the flow line are on a floating vessel and the structure and tubular conduit are submerged.

8. A method in accordance with claim 1 in which the flexible member and the flow line are on a fixed offshore structure extending at least to water surface and the tubular conduit also extends at least to water surface.

9. A method in accordance with claim 1 in which the offshore structure is provided with said curved tubular conduit before the offshore structure is placed in said body of water.

10. A method in accordance with claim 1 in which the point adjacent water surface is a floating vessel horizontally spaced from said structure.

11. A method in accordance with claim 1 in which the outer wall of the flow line is lubricated.

12. A method in accordance with claim 1 in which the flow line is pushed at the same time it is being pulled by exertion of force on the second end.

13. A method in accordance with claim 1 in which:

a. lengths of pipe are added to the first end of said flow line at least adjacent water surface;

b. the flexible member is a cable;

c. the flexible member is positioned by running it downwardly through said conduit;

d. the offshore structure is provided with said curved tubular conduit prior to placement of the structure in said body of water; and

e. the flow line is pushed at the same time it is being pulled by exertion of force on the second end.

14. A method in accordance with claim 1 in which the flexible member is positioned in said conduit by pulling same from said structure to said location horizontally spaced apart from said structure.

15. A method in accordance with claim 14 in which the location is on a floating vessel.

16. A method for installing a flow line having first and second ends on an offshore structure in a body of water wherein said structure is provided with an open-ended curve tubular conduit having a and end at least adjacent water bottom and a second end extending vertically on said structure which comprises:

running the first end of a flow line from water surface into the second end of said curved conduit and out the first end of said conduit and then to a point at least adjacent water surface horizontally spaced from said structure until the second end of said flow line is accessible from said structure and the first end is accessible from water surface.

17. A method in accordance with claim 16 in which the flow line is pulled and pushed through said curved conduit.

18. A method in accordance with claim 17 in which a lubricant is applied to at least one of the contact surfaces between the inner wall of the conduit and the outer wall of the flow line.

19. A method in accordance it claim 17 in which the outer wall of the flow line is lubricated.

20. A method in accordance with claim 16 in which the flow line is pushed through said curved conduit.

21. A method in accordance with claim 16 in which the second end of the tubular conduit extends at least to water surface.

22. A method in accordance with claim 16 in which the tubular conduit is submerged.

23. A method in accordance with claim 16 in which a lubricant is applied to at least one he contact surfaces between the inner wall of the conduit and outer wall of the flow line.

24. A method in accordance with claim 16 in which the flow line is run into said curved conduit by pulling.

25. A method for installing a flow line having first and second ends on a structure located vertically offshore in a body of water wherein said structure is provided with an open-ended curved tubular conduit having a first end located at least adjacent water bottom and a second end extending vertically on said structure, said conduit having a flow line arranged therein with a first end adjacent the first end of the conduit and the second end extending from the second end of the conduit which comprises:

moving said flow line through said curved conduit and out the first end of said conduit such that said first end of said flow line is accessible from water surface spaced horizontally from said structure and the second end is accessible from said structure.

26. A method in accordance with claim 25 in which the flow line is pulled through said curved conduit.

27. A method in accordance with claim 25 in which the line is pulled and pushed through said curved conduit.

28. A method in accordance with claim 27 in which a lubricant is applied to at least one of the contact surfaces between the inner wall of the conduit and the outer wall of the flow line.

29. A method in accordance with claim 25 in which the outer wall of the flow line is lubricated.

30. A method in accordance with claim 25 in which the residual curvature or set of the flow line is removed when said flow line is run through said conduit.

31. A method in accordance with claim 30 in which the residual curvature or set is removed by running the flow line through a portion of the conduit having a radius of curvature in reverse to that of the main portion the conduit.

32. A method in accordance with claim 25 in which the end of the flow line adjacent water bottom is connected to a pipe line.

33. A method for installing pipe in a body of water using pipe contact means including a member having structure adapted to contact pipe on substantially opposite sides thereof capable of changing the direction of movement of said pipe from a generally vertical to a generally horizontal direction which comprises attaching one end of a flexible member extending through said pip contact means to said pipe and then moving said flexible member and said pipe downwardly through said pipe contact means until said pipe extends through said pipe contact means to a point horizontally spaced a substantial distance from said pipe contact means.

34. A method in accordance with claim 33 in which said pipe contact means and at the same time said pipe is pulled through said pipe contact means.

35. A method in accordance with claim 3 in which residual curvature or set is removed from said pipe as the pipe traverses said pipe contact means.

36. Apparatus for installing pipe in a body of water which comprises:

pipe contact means including a member having structure adapted to contact pipe on substantially opposite sides thereof capable of changing the direction of movement of a pipe from a generally vertical to a generally horizontal direction when said pipe is moved downwardly through said pipe contact means

means for moving pipe downwardly through said pipe contact means; and

means arranged adjacent said pipe contact means for removing residual curvature or set from the pipe as said pipe traverses said pipe contact means.

37. Apparatus as recited in claim 36 including means within said pipe contact means for facilitating the movement of pipe through said pipe contact means.