US3353851A - Pneumatic cylinder for applying tension to riser pipe - Google Patents

Pneumatic cylinder for applying tension to riser pipe Download PDF

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US3353851A
US3353851A US325855A US32585563A US3353851A US 3353851 A US3353851 A US 3353851A US 325855 A US325855 A US 325855A US 32585563 A US32585563 A US 32585563A US 3353851 A US3353851 A US 3353851A
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riser pipe
tension
section
drilling
pipe
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Renic P Vinceut
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Pan American Petroleum Corp
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    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B19/00Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrick; Apparatus for feeding the rods or cables
    • E21B19/08Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods
    • E21B19/09Apparatus for feeding the rods or cables; Apparatus for increasing or decreasing the pressure on the drilling tool; Apparatus for counterbalancing the weight of the rods specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
    • EFIXED CONSTRUCTIONS
    • E21EARTH DRILLING; MINING
    • E21BEARTH DRILLING, e.g. DEEP DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • E21B17/01Risers

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  • This invention pertains to the art of marine drilling, and more particularly to a method for applying a stabilizing force to the so-called riser pipe used in such marine drilling operations in deep water.
  • Such drilling (usually to produce petroleum) is often carried out at the present time in deep water by using a floating drilling vessel carrying a suitable derrick and other drilling equipment. This is anchored over the well location. At the sea floor some type of special apparatus is cemented in place to define the upper end of the well.
  • the problem then arises as to how to orient the drill string so that each time after replacement of a drill bit the string will re-enter the portion of the well already drilled, and so that during the drilling operation the drilling fluid employed can be circulated between the drilling vessel and the bottom of the well without substantial contamination from the sea water surrounding the location.
  • the drilling vessel itself, of course, is not completely stable in location even with the best means of anchoring known. Due to action of the wind and of waves it rolls, pitches, and moves laterally. In addition, tidal action causes the drilling vessel to change its main elevation by quite a number of feet.
  • riser pipe which is an assembly making up a tubular conduit attached at the bottom to the sea floor apparatus and at the top to the drill rig on the floating vessel.
  • riser pipe must contain at least one flexible joint which is ordinarily provided near the lower end, and at least one telescoping section near the upper end. This provides, therefore, for both angular displacement of the drill rig axis relative to the hole at the sea floor and also for changes in elevation between the vessel and the sea floor.
  • the riser pipe which is a heavy columnar member, may lose its elastic stability, if it is too long. It is also self-evident that the critical length, i.e., the maximum length for which the column is stable while self-supporting, depends on the pipe diameter and wall thickness. As greater and greater depths are considered, a riser pipe length is reached for which the column ceases to be selfsupporting, and to avoid its buckling, the upper termination of the column must be supported through subjecting this termination to a certain amount of tension.
  • the critical length of a hollow column member depends also on the difference of densities between the fluid inside and outside of the member.
  • the critical length becomes smaller, and more tension must be applied at the upper termination to maintain the elastic stability.
  • the riser pipe When critical conditions are reached, the riser pipe will buckle even in absence of any wave forces. Such forces may, however, bend the pipe too much and cause its failure, even when the length of the column is below the critical value. Subjecting the upper termination of the riser pipe to tension decreases the amount of bending and may prevent such failures.
  • FIGURE 1 shows a typical floating drilling vessel supporting a riser pipe assembly suitably connected at the drilling base to vprotective equipment, and in which the telescoping section or slip joint has been provided with my invention
  • FIGURE 2 shows a portion of the riser pipe assembly including in greater detail the slip joint shown in FIGURE 1. Part of the drawing in FIGURE 2 is in cross section;
  • FIGURE '3 represents a mathematical relationship or graph used in connection with this stabilizing method.
  • FIGURE 1 the sea floor is represented diagrammatically at 11.
  • an assemblage of apparatus including a heavy plate 12 with an upper portion 13, a sub 14, and a connection 15 to a blowout preventer 16, which is equipped with hydraulically-actuated rams, the hydraulic pressure being obtained from the drilling vessel (not shown) through suitable high pressure lines to the blowout preventer 16 (also not shown).
  • a blowout preventer 17 which is equipped with hydraulically-actuated rams, the hydraulic pressure being obtained from the drilling vessel (not shown) through suitable high pressure lines to the blowout preventer 16 (also not shown).
  • a second blowout preventer 17 also equipped for remote hydraulic actuation from the loading drilling vessel.
  • a connection 18 to the start of the riser pipe assembly 50 is shown diagrammatically.
  • a flex joint 28 well known in this art.
  • This flex joint consists of a metal sleeve attached at the bottom to member 53. The flex joint has been cut through at several different vertical levels around the circumference to make a plurality of mechanically interlinked sections with considerable angular mechanical freedom.
  • the metal conduit can permit an angular deflection of the upper pipe section 19 attached by connector 51 to the flex joint 20 through an angle of the order of 4 to 7 degrees in any direction, but the sections of this pipe are held together, much the same as interlocking pieces of a jigsaw puzzle.
  • the cut sections are covered with a reinforced rubber sleeve held tightly against the inner flexible metal sleeve at the top and bottom by two-piece metal clamps.
  • the rubber sleeve is ordinarily also covered with fabric, for example, a layer of tightly wrapped Manila rope, or the like.
  • the riser pipe 19 continues, preferably up to the order of 30 to 40 feet below the surface of the water, the various joints of this conduit being connected together by clamps or the like, as is well known in this art.
  • the apparatus described in FIGURES 1 and 2 includes a column extend: ing from the sea floor 11 up to the top of member 19 which is in compression, and a second member consisting of the upper conduit 22 and the apparatus above it, all of which is in tension. It is well known that a column in compression may buckle. One factor which afiects such buckling is the weight in fluid per unit length of the column, which is in compression. This weight w is equal to the weight per unit length of the riser pipe section 19 plus the weight per unit length of the fluid inside the pipe, less the weight per unit length of an equivalent column of displaced fluid (i.e., sea water) outside the pipe.
  • displaced fluid i.e., sea water
  • W weight of pipe/ unit length
  • W density of fluid inside pipe
  • W density of fluid outside pipe
  • This Equation 1 does not take into consideration any lateral force such as a wave force on the riser. If such wave forces were zero, the maximum length, i.e., that length at which the pipe would just buckle would be given by the equation. At that length, or at a greater length, the riser would be expected to fail even in the absence of wave forces. To give an idea of this height, for ordinary 16-inch pipe weighing 62.6 pounds per foot with a wall thickness of of an inch and with sea water in and out, the critical length is approximately 328 feet. However, if the riser pipe were conducting a mud with a density of 18 pounds per gallon, and on the assumption that the sea water density was 9 pounds per gallon, the corresponding critical length is reduced to 250 feet.
  • the amount of desired tension can be obtained on the following basis: First one determines the critical length L in accordance with Equation 1, given above. The ratio of the actual length L of the desired column up to the top of member 19, divided by the critical length L is then determined. This value (L/L will be referred to as the factor 1. One then enters the graph shown in FIGURE 3 to determine a corresponding quantity X. Finally, the necessary tension or total upward force which must be applied is computed from the following formula:
  • buoyant supports When one employs buoyant supports, the necessary consequence is a considerable increase of the area exposed to wave forces, which results in a considerable increase in tendency to bend the riser pipe assembly-the very defeet that the buoyant chambers were attempting to prevent. If, on the other hand, one employs hanging weights connected through flexible cables and pulleys to the upper part of the lower member of the riser pipe, increased wave action is found on the weights themselves and there is a very serious servicing problem involved on the pulleys, as well as the tensioning cables connecting the weights with the riser pipe.
  • variable volume cell is used since it is apparent that upon motion of the telescoping sections the volume of the chamber 28 will change accordingly.
  • a separate conduit 29 is connected to the variable volume cell, preferably just above the lower end 26 of the upper conduit 22.
  • the conduit 29 is connected to an appropriate source of fluid pressure (not shown) through a quick disconnect joint 32 and conduit 33.
  • any fluid which can be conducted through conduit 29 to the variable volume cell 28 may be employed.
  • a gas for example, compressed air, compressed nitrogen, or the like
  • a liquid is used for applying pressure in the variable volume cell, such telescoping action of these two parts of the riser pipe cause an appreciable. difference in tension, increasing as the variable volume cell decreases in size and vice versa.
  • variable volume cell 28 when the drilling fluid density increases there is need for an appropriate increase in the tension applied and, accordingly, the operators should increase the pressure within the variable volume cell 28.
  • the volume of cell .28 is appreciable and if a gas is, used to apply pressure, within this cell, then minor changes in the length of this variable volume cell, in accordance with Boyles law, will give only 'minor changes in pressure.
  • the method of stabilizing which has been described, may be used when the lower portion of riser pipe 19 is shorter than the 75 percent of critical length. However, there is no particular reason for such stabilization under that conditon. However, as soon as L has appreciably exceeded the 75 percent of critical length of riser pipe, as illustrated by the plot in FIGURE 3, tension is needed in the riser pipe to stabilize it and keep it from buckling. In this case the invention will furnish all of the stability needed.
  • Means for stabilizing a riser pipe in deep water marine drilling operations by maintaining said riser pipe in tension, said riser pipe being connected between a floating vessel and the marine floo-r and including at least one telescoping section near the bottom of said vessel, said section comprising inner and outer conduit sections slidingly sealed to each other at the ends of said section thereby forming a fluid tight variable volume cell therebetween, each said end of said sections carrying a sealing means thereon which forms said cell between said inner and outer conduit, said variable volume cell being so constructed that the axial distance between the cell ends of said section can increase, thereby placing the riser pipe in tension, said tension being mantained by supplying only fluid under pressure to the variable volume cell formed within said telescoping section by said conduit sections, whereby the tendency of said riser pipe to column buckling and bending during operations is minimized.
  • Equipment for marine drilling operations from a floating vessel comprising a riser pipe assembly attached at one end to said floating vessel and at the other end to the marine floor and containing therebetween a telescoping section including an inner and an outer conduit section comprising part of the confining walls of said riser pipe assembly, said inner conduit section having an outer diameter less than the inner diameter of the outer conduit section and having an enlarged head portion, said outer pipe section provided with a radially inwardly directed portion, the periphery of said head portion and said radially inwardly directed portion provided with seal means thereon, said head portion, radially inwardly directed portion and the walls of the inner and outer conduit sections contained therebetween, forming a substantially fluid-tight variable volume cell in said section, said outer pipe section provided with conduit connecting means in the wall thereof in the area of said variable volume cell, a source of fiuid pressure, and a conduit connected to said source and to said means on said variable volume cell, by means of which fluid pressure in said cell provides tensile force between the ends of said assembly to

Description

R. P. VINCENT Nov. 21, 1967 PNEUMATIC CYLINDER FOR APPLYING TENSION TO RISER PIPE 2 Sheets-Sheet 1 Filed Nov. 26, 1965 FIG. I
INVENTOR. RENIC P. VINCENT BY P a! M ATTORNEY R. P. VINCENT Nov. 21, 1967 PNEUMATIC CYLINDER FOR APPLYING TENSION TO RISER PIPE Filed Nov. 26, 1963 2 Sheets-Sheet 2 TO PUMP RENIC P. VINCENT INVENTOR A T TORNE Y United States Patent *Ofitice Patented Nov. 21, 1967 3,353,851 PNEUMATIC CYLINDER FOR APPLYING TENSION T RISER PIPE Renic P. Vincent, Tulsa, Okla, assignor to Pan American Petroleum Corporation, Tulsa, Okla, a corporation of Delaware Filed Nov. 26, 1963, Ser. No. 325,855 4 Claims. (Cl. 285-302) ABSTRACT OF THE DISCLOSURE In rotary drilling from a floating drilling barge or similar support, it is found convenient to employ a tubular conduit system frequently called a riser pipe assembly between the floating vessel and the solid ground below the water as a means of confining the return of the drilling fluid from the mud line to the floating vessel. This assembly is arranged with a flexible joint near the bottom to permit horizontal displacement of the drill rig with respect to the top of the well at the mud line, and a slip joint or telescoping section, which provides for longitudinal changes in length of the assembly required due to vertical movement of the floating vessel. If this slip joint is adjacent the floating vessel, as I prefer, there is a long section from the slip joint to the mud line which is a column under compression. Mechanically this is undesirable. Various systems have been proposed for placing this part of the riser pipe assembly under tension. The gist of my invention insists in applying hydraulic (frequently pneumatic) pressure within the slip joint in such a way that this pressure applies an upward force to the lower section of the riser pipe and a downward force to the top section of the riser pipe, to place the assembly in tension. Such hydraulic pressure is applied in a predetermined amount, preferably from the floating vessel, through an at least semi-flexible hose to the variable volume cell formed between parts making up the slip joint.
This invention pertains to the art of marine drilling, and more particularly to a method for applying a stabilizing force to the so-called riser pipe used in such marine drilling operations in deep water. Such drilling (usually to produce petroleum) is often carried out at the present time in deep water by using a floating drilling vessel carrying a suitable derrick and other drilling equipment. This is anchored over the well location. At the sea floor some type of special apparatus is cemented in place to define the upper end of the well. In the rotary system of drilling, which is customarily employed, the problem then arises as to how to orient the drill string so that each time after replacement of a drill bit the string will re-enter the portion of the well already drilled, and so that during the drilling operation the drilling fluid employed can be circulated between the drilling vessel and the bottom of the well without substantial contamination from the sea water surrounding the location. The drilling vessel itself, of course, is not completely stable in location even with the best means of anchoring known. Due to action of the wind and of waves it rolls, pitches, and moves laterally. In addition, tidal action causes the drilling vessel to change its main elevation by quite a number of feet.
One means of being sure that the mud returns will be uncontaminated and that the drill string will retrace its path each time after the bit is replaced (or during cementing operations) is to connect the apparatus at the sea floor to the floating drilling vessel by what is called a riser pipe, which is an assembly making up a tubular conduit attached at the bottom to the sea floor apparatus and at the top to the drill rig on the floating vessel. Such riser pipe must contain at least one flexible joint which is ordinarily provided near the lower end, and at least one telescoping section near the upper end. This provides, therefore, for both angular displacement of the drill rig axis relative to the hole at the sea floor and also for changes in elevation between the vessel and the sea floor.
In the first attempts to use riser pipes, difliculties and mechanical failures were encountered which ultimately were determined to take place due to lack of elastic stability of the riser pipe.
The riser pipe, which is a heavy columnar member, may lose its elastic stability, if it is too long. It is also self-evident that the critical length, i.e., the maximum length for which the column is stable while self-supporting, depends on the pipe diameter and wall thickness. As greater and greater depths are considered, a riser pipe length is reached for which the column ceases to be selfsupporting, and to avoid its buckling, the upper termination of the column must be supported through subjecting this termination to a certain amount of tension.
It is known to those skilled in the art that the critical length of a hollow column member, such as the riser pipe, depends also on the difference of densities between the fluid inside and outside of the member. When the fluid becomes denser inside than outside, the critical length becomes smaller, and more tension must be applied at the upper termination to maintain the elastic stability.
When critical conditions are reached, the riser pipe will buckle even in absence of any wave forces. Such forces may, however, bend the pipe too much and cause its failure, even when the length of the column is below the critical value. Subjecting the upper termination of the riser pipe to tension decreases the amount of bending and may prevent such failures.
This development will be described in connection with the appended three figures. In these figures:
FIGURE 1 shows a typical floating drilling vessel supporting a riser pipe assembly suitably connected at the drilling base to vprotective equipment, and in which the telescoping section or slip joint has been provided with my invention;
FIGURE 2 shows a portion of the riser pipe assembly including in greater detail the slip joint shown in FIGURE 1. Part of the drawing in FIGURE 2 is in cross section;
FIGURE '3 represents a mathematical relationship or graph used in connection with this stabilizing method.
In FIGURE 1, the sea floor is represented diagrammatically at 11. Mounted on this is an assemblage of apparatus including a heavy plate 12 with an upper portion 13, a sub 14, and a connection 15 to a blowout preventer 16, which is equipped with hydraulically-actuated rams, the hydraulic pressure being obtained from the drilling vessel (not shown) through suitable high pressure lines to the blowout preventer 16 (also not shown). Above this (with some other apparatus not important to this invention) may be and desirably is mounted a second blowout preventer 17 also equipped for remote hydraulic actuation from the loading drilling vessel. Above this is a connection 18 to the start of the riser pipe assembly 50. This whole set of apparatus is shown diagrammatically.
It has already been mentioned that one function of the riser pipe is to provide freedom of angular movement between the drilling vessel and the drill string (at the point where the string passes through), for example, at the plate 12. Accordingly, above a short sub at the bottom of the riser pipe 19 is mounted what is called a flex joint 28, well known in this art. This flex joint consists of a metal sleeve attached at the bottom to member 53. The flex joint has been cut through at several different vertical levels around the circumference to make a plurality of mechanically interlinked sections with considerable angular mechanical freedom. Thus, the metal conduit can permit an angular deflection of the upper pipe section 19 attached by connector 51 to the flex joint 20 through an angle of the order of 4 to 7 degrees in any direction, but the sections of this pipe are held together, much the same as interlocking pieces of a jigsaw puzzle.
This gives a required longitudinal strength but does not close off the riser pipe from the sea water outside the riser. Accordingly, the cut sections are covered with a reinforced rubber sleeve held tightly against the inner flexible metal sleeve at the top and bottom by two-piece metal clamps. The rubber sleeve is ordinarily also covered with fabric, for example, a layer of tightly wrapped Manila rope, or the like.
Above the top of the flex joint, the riser pipe 19 continues, preferably up to the order of 30 to 40 feet below the surface of the water, the various joints of this conduit being connected together by clamps or the like, as is well known in this art.
It is necessary to compensate for vertical changes in elevation of the drilling vessel 52, which is held over the apparatus mounted above the sea floor 11, for example by anchoring or mooring lines 53. This is accomplished by using what is called a slip joint which permits one part of the riser pipe 19 to telescope within another part 22 (see FIGURE 2). This slip joint ordinarily provides about feet of travel to permit Vertical movement of the vessel. The slip joint is equipped with packing 27 which tends to render the friction joints substantially fluid-tight. The upper conduit section 22 is connected through some sort of coupling mechanism such as a clamp 23 to the bottom of the drilling assembly 24 which is mounted on the drilling vessel itself. The drill string, and the various strings of casing, are run through the inside of the riser pipe.
It is apparent from this description that the apparatus described in FIGURES 1 and 2 includes a column extend: ing from the sea floor 11 up to the top of member 19 which is in compression, and a second member consisting of the upper conduit 22 and the apparatus above it, all of which is in tension. It is well known that a column in compression may buckle. One factor which afiects such buckling is the weight in fluid per unit length of the column, which is in compression. This weight w is equal to the weight per unit length of the riser pipe section 19 plus the weight per unit length of the fluid inside the pipe, less the weight per unit length of an equivalent column of displaced fluid (i.e., sea water) outside the pipe.
, From this mathematical treatment it is possible to determine a critical height which is the maximum length of j the column in compression for which the system is stable.
This is given for the riser pipe by the expression where:
' L =critical weight I=moment of inertia of the pipe E=Youngs modulus of pipe W=weight of column/unit length I where:
W ,=weight of pipe/ unit length W =density of fluid inside pipe W =density of fluid outside pipe For the derivation of Equation 1, see for instance A Study of the Buckling of Rotary Drilling Strings, by Arthur Lubinski, published in the 1950 vol. of API Drilling and Production Practice. For Equation 2, see for instance Buckling of Tubing in Pumping Wells, Its Effects and Means for Controlling It, by Arthur Lubinski and K. A. Blenkarn, published in the Transactions of AIME (Petroleum Branch), 1957, vol. 210.
This Equation 1 does not take into consideration any lateral force such as a wave force on the riser. If such wave forces were zero, the maximum length, i.e., that length at which the pipe would just buckle would be given by the equation. At that length, or at a greater length, the riser would be expected to fail even in the absence of wave forces. To give an idea of this height, for ordinary 16-inch pipe weighing 62.6 pounds per foot with a wall thickness of of an inch and with sea water in and out, the critical length is approximately 328 feet. However, if the riser pipe were conducting a mud with a density of 18 pounds per gallon, and on the assumption that the sea water density was 9 pounds per gallon, the corresponding critical length is reduced to 250 feet.
The presence of lateral forces, such as wave forces, causes the pipe to bend. From a practical standpoint it is found that such bending may be excessive only when the actual length of the column under compression is fairly close to the critical length. It seems sufficiently safe to adopt in practice as a maximum length of the unsupported riser pipe a value equal to about of the critical value L Thus, in the case just considered, one would conclude that a length of about 187 feet is the maximum that one should use for the section of the 16-inch riser pipe in compression.
If the length of the riser pipe is greater than the value considered, i.e., as the depth of water increases, one must in some fashion provide additional support for the riser pipe. Various systems have been suggested to accomplish this. Essentially they all involve in some fashion applying an upward force to the column otherwise under compression, i.e., to place that colunm to a degree under tension. Using the first reference cited above, it may be shown that the amount of desired tension can be obtained on the following basis: First one determines the critical length L in accordance with Equation 1, given above. The ratio of the actual length L of the desired column up to the top of member 19, divided by the critical length L is then determined. This value (L/L will be referred to as the factor 1. One then enters the graph shown in FIGURE 3 to determine a corresponding quantity X. Finally, the necessary tension or total upward force which must be applied is computed from the following formula:
where T is the tensile force to be applied at the upper extremity of member 25. It can be seen by reference to FIGURE 3 that if F=0'.75 then X =0, which means that a length of riser pipe no longer than A of the critical length requires no application of tension. For greater values of the length of the riser pipe, i.e., for deeper water, the method explained above gives the necessary value of tension which will give the same degree of safety as that which will occur with the unsupported riser pipe not longer than A of the critical length. Thus,
if the length of the riser pipe under compression in the example given above were 32.5. feet, the factor i would equal X =l.67, and T=22,000 pounds.
Various methods have been suggested for applying tension to a riser pipe to avoid the difficulty of possible buckling or excessive bending. For example, the Rhodes et al. US. Patent 3,017,934 suggests the use of buoyant supports for the casing extending upwardly around the main riser pipe itself. It is also known to attach the upper part of the riser pipe 19 directly to the vessel above with cables which pass through pulleys afiixed to the bottom of the drilling vessel down to weights, which thus supply tension to the lower portion 19 of the riser pipe. However, there are real difiiculties in both of these attempts at solution of the problem of stabilizing the riser pipe. When one employs buoyant supports, the necessary consequence is a considerable increase of the area exposed to wave forces, which results in a considerable increase in tendency to bend the riser pipe assembly-the very defeet that the buoyant chambers were attempting to prevent. If, on the other hand, one employs hanging weights connected through flexible cables and pulleys to the upper part of the lower member of the riser pipe, increased wave action is found on the weights themselves and there is a very serious servicing problem involved on the pulleys, as well as the tensioning cables connecting the weights with the riser pipe.
I have found that it is possible to stabilize the riser pipe in this type of marine drilling operations (that is, those involving drilling in deep water) which consists in applying tension to the riser pipe by means of fluid pressure applied to the telescoping section of the riser pipe. Reference to FIGURE 2 will illustrate this. Here the lower portion of the riser pipe 19 terminates in an upper end 25 while the upper portion of the riser pipe 22 terminates in a lower end 26. The two sections of the riser pipe 19 and 22 are designed with an appreciable difference in diameter and each is provided with packing 27 so that the upper and lower telescoping portions of the riser pipe, together with the ends or faces 30 and 31 thereof, form a variable volume cell 28. The term variable volume cell is used since it is apparent that upon motion of the telescoping sections the volume of the chamber 28 will change accordingly. A separate conduit 29 is connected to the variable volume cell, preferably just above the lower end 26 of the upper conduit 22. The conduit 29 is connected to an appropriate source of fluid pressure (not shown) through a quick disconnect joint 32 and conduit 33.
It is apparent from the description of the apparatus that when fluid pressure is applied through conduit 29 to the variable volume cell 28 that an upward pressure is exerted on the lower face 30 of the end 25 and similarly on the upper face 31 of lower end 26, thus applying an upward force on member 19 and a downward force on member 22 of equal magnitude. This, therefore, is a means of applying the required tension to the riser pipe assembly so that it is possible to maintain it stable under all conditions. The drilling crew need simply be instructed to maintain the force required above that given by Equation 3. The tension is equal to the fluid pressure in cell 23 times the area of face 30. I,
It is apparent that in utilization of this method of applying tension to the riser pipe that any fluid which can be conducted through conduit 29 to the variable volume cell 28, may be employed. However, I find it particularly advantageous to use a gas, for example, compressed air, compressed nitrogen, or the like, because of the fact that there is almost continual motion between the sections 19 and 22 of the riser pipe, as the floating vessel responds to wave and wind action. If a liquid is used for applying pressure in the variable volume cell, such telescoping action of these two parts of the riser pipe cause an appreciable. difference in tension, increasing as the variable volume cell decreases in size and vice versa. However, it is desirable to maintain this tension substantially constant, except when there is an increase in the density of the drilling fluid. As is apparent upon reference to the equations given above, when the drilling fluid density increases there is need for an appropriate increase in the tension applied and, accordingly, the operators should increase the pressure within the variable volume cell 28. Now, if the volume of cell .28 is appreciable and if a gas is, used to apply pressure, within this cell, then minor changes in the length of this variable volume cell, in accordance with Boyles law, will give only 'minor changes in pressure. In order to further minimize such pressure changes, it is desirable though not strictly essential to provide a surge tank 34 at some conventional point connected in parallel with the pump (not shown) to conduit 33. (The volume of such tank 34 should preferably be at least as large as the maximum volume in cell 28.)
It is not to be assumed, however, that liquids cannot be employed for, in fact, they will operate well, the only difference being that there will be a larger component of varying tension under ordinary operating conditions, since liquids have less compressibility than gases. If a liquid is used, it is necessary to provide surge tank 34 as discussed above, with at least the major part of its volume being occupied at all times by a gas.
The method of stabilizing which has been described, may be used when the lower portion of riser pipe 19 is shorter than the 75 percent of critical length. However, there is no particular reason for such stabilization under that conditon. However, as soon as L has appreciably exceeded the 75 percent of critical length of riser pipe, as illustrated by the plot in FIGURE 3, tension is needed in the riser pipe to stabilize it and keep it from buckling. In this case the invention will furnish all of the stability needed.
I claim:
1. Means for stabilizing a riser pipe in deep water marine drilling operations by maintaining said riser pipe in tension, said riser pipe being connected between a floating vessel and the marine floo-r and including at least one telescoping section near the bottom of said vessel, said section comprising inner and outer conduit sections slidingly sealed to each other at the ends of said section thereby forming a fluid tight variable volume cell therebetween, each said end of said sections carrying a sealing means thereon which forms said cell between said inner and outer conduit, said variable volume cell being so constructed that the axial distance between the cell ends of said section can increase, thereby placing the riser pipe in tension, said tension being mantained by supplying only fluid under pressure to the variable volume cell formed within said telescoping section by said conduit sections, whereby the tendency of said riser pipe to column buckling and bending during operations is minimized.
2. The process according to claim 1 in which said fluid pressure is applied pneumatically by meansv of a 3. The process according to claim 1 in which said fluid pressure is maintained substantially constant as long as the drilling fluid density remains substantially constant and is increased upon increase of said drilling fluid density.
4. Equipment for marine drilling operations from a floating vessel comprising a riser pipe assembly attached at one end to said floating vessel and at the other end to the marine floor and containing therebetween a telescoping section including an inner and an outer conduit section comprising part of the confining walls of said riser pipe assembly, said inner conduit section having an outer diameter less than the inner diameter of the outer conduit section and having an enlarged head portion, said outer pipe section provided with a radially inwardly directed portion, the periphery of said head portion and said radially inwardly directed portion provided with seal means thereon, said head portion, radially inwardly directed portion and the walls of the inner and outer conduit sections contained therebetween, forming a substantially fluid-tight variable volume cell in said section, said outer pipe section provided with conduit connecting means in the wall thereof in the area of said variable volume cell, a source of fiuid pressure, and a conduit connected to said source and to said means on said variable volume cell, by means of which fluid pressure in said cell provides tensile force between the ends of said assembly to decrease tendency for column buckling 0r bending in said assembly.
References Cited UNITED STATES PATENTS Kamrnerer 175-5 X Bellinger 28518 Rhodes et al 175220 X Kofahl 166-665 Buoy 287-20 X Pollard et a1 166-66.5 X Lacy 16666.5
CARL W. TOMLIN, Primary Examiner.
DAVE W. AROLA, Assistant Examiner.
UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,353,851 November 21, 1967 Renic P. Vincent It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 3, line 7, for "28" read 20 line 70, for "weight" read height column 6, line 17, for "conventionaj read convenient Signed and sealed this 17th day of December 1968.
(SEAlJ Attest:
EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Jr.
Attesting Officer

Claims (1)

1. MEANS FOR STABILIZING A RISER PIPE IN DEEP WATER MARINE DRILLING OPERATIONS BY MAINTAINING SAID RISER PIPE IN TENSION, SAID RISER PIPE BEING CONNECTED BETWEEN A FLOATING VESSEL AND THE MARINE FLOOR AND INCLUDING AT LEAST ONE TELESCOPING SECTION NEAR THE BOTTOM OF SAID VESSEL, SAID SECTION COMPRISING INNER AND OUTER CONDUIT SECTIONS SLIDING SEALED TO EACH OTHER AT THE ENDS OF SAID SECTION THEREBY FORMING A FLUID TIGHT VARIABLE VOLUME CELL THEREBETWEEN, EACH SAID END OF SAID SECTIONS CARRYING A SEALING MEANS THEREON WHICH FORMS SAID CELL BETWEEN SAID INNER AND OUTER CONDUIT, SAID VARIABLE VOLUME CELL BEING SO CONSTRUCTED THAT THE AXIAL DISTANCE BETWEEN THE CELL ENDS OF SAID SECTION CAN INCREASE, THEREBY PLACING THE RISER PIPE IN TENSION, SAID TENSION BEING MANTAINED BY SUPPLYING ONLY FLUID UNDER PRESSURE TO THE VARIABLE VOLUME CELL FORMED WITHIN SAID TELESCOPING SECTION BY SAID CONDUIT SECTIONS, WHEREBY THE TENDENCY OF SAID RISER PIPE TO COLUMN BUCKING AND BENDING OPERATIONS IS MINIMIZED.
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Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3601187A (en) * 1969-05-02 1971-08-24 Exxon Production Research Co Drilling riser
US3917006A (en) * 1972-09-29 1975-11-04 Smith International Floorlevel motion compensator
US3955621A (en) * 1975-02-14 1976-05-11 Houston Engineers, Inc. Riser assembly
US4094548A (en) * 1973-11-08 1978-06-13 Schuttgutfordertechnik Ag Apparatus for conveying and separating loose material
US4367981A (en) * 1981-06-29 1983-01-11 Combustion Engineering, Inc. Fluid pressure-tensioned slip joint for drilling riser
US4615542A (en) * 1983-03-29 1986-10-07 Agency Of Industrial Science & Technology Telescopic riser joint
FR2584449A1 (en) * 1985-01-31 1987-01-09 Vetco Offshore Ind Inc UPPER ASSEMBLY FOR MARINE EXTENSION TUBE, SELF-TENSIONING SLIDING JOINT, ROTATION BEARING SEAL, TUBULAR CONDUIT, SHIP AND METHOD USING THE SAME
US5069488A (en) * 1988-11-09 1991-12-03 Smedvig Ipr A/S Method and a device for movement-compensation in riser pipes
US6148922A (en) * 1996-05-13 2000-11-21 Maritime Hydraulics As Slip joint
US6173781B1 (en) 1998-10-28 2001-01-16 Deep Vision Llc Slip joint intervention riser with pressure seals and method of using the same
US20080078880A1 (en) * 2006-09-29 2008-04-03 Airbus Uk Limited Aircraft fuel pipe coupling
WO2008051092A1 (en) * 2006-10-27 2008-05-02 Fmc Kongsberg Subsea As Telescopic joint
US20080271896A1 (en) * 2004-05-21 2008-11-06 Fmc Kongsberg Subsea As Device in Connection with Heave Compensation
US20120325487A1 (en) * 2011-06-23 2012-12-27 David Wright Systems and methods for stabilizing oilfield equipment
US9441426B2 (en) 2013-05-24 2016-09-13 Oil States Industries, Inc. Elastomeric sleeve-enabled telescopic joint for a marine drilling riser

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US2945676A (en) * 1956-11-08 1960-07-19 Jr Archer W Kammerer Hydraulic weight control and compen-sating apparatus for subsurface well bore devices
US2955850A (en) * 1956-11-15 1960-10-11 Strachan & Henshaw Ltd Pipe coupling having telescopic and lateral compensating means
US3017934A (en) * 1955-09-30 1962-01-23 Shell Oil Co Casing support
US3179179A (en) * 1961-10-16 1965-04-20 Richfield Oil Corp Off-shore drilling apparatus
US3181435A (en) * 1961-10-27 1965-05-04 Harry R Buey Fluid pressure actuated mechanism
US3195639A (en) * 1961-10-16 1965-07-20 Richfield Oil Corp Off-shore drilling and production apparatus
US3211224A (en) * 1963-10-09 1965-10-12 Shell Oil Co Underwater well drilling apparatus

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Publication number Priority date Publication date Assignee Title
US3017934A (en) * 1955-09-30 1962-01-23 Shell Oil Co Casing support
US2945676A (en) * 1956-11-08 1960-07-19 Jr Archer W Kammerer Hydraulic weight control and compen-sating apparatus for subsurface well bore devices
US2955850A (en) * 1956-11-15 1960-10-11 Strachan & Henshaw Ltd Pipe coupling having telescopic and lateral compensating means
US3179179A (en) * 1961-10-16 1965-04-20 Richfield Oil Corp Off-shore drilling apparatus
US3195639A (en) * 1961-10-16 1965-07-20 Richfield Oil Corp Off-shore drilling and production apparatus
US3181435A (en) * 1961-10-27 1965-05-04 Harry R Buey Fluid pressure actuated mechanism
US3211224A (en) * 1963-10-09 1965-10-12 Shell Oil Co Underwater well drilling apparatus

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3601187A (en) * 1969-05-02 1971-08-24 Exxon Production Research Co Drilling riser
US3917006A (en) * 1972-09-29 1975-11-04 Smith International Floorlevel motion compensator
US4094548A (en) * 1973-11-08 1978-06-13 Schuttgutfordertechnik Ag Apparatus for conveying and separating loose material
US3955621A (en) * 1975-02-14 1976-05-11 Houston Engineers, Inc. Riser assembly
US4367981A (en) * 1981-06-29 1983-01-11 Combustion Engineering, Inc. Fluid pressure-tensioned slip joint for drilling riser
US4615542A (en) * 1983-03-29 1986-10-07 Agency Of Industrial Science & Technology Telescopic riser joint
FR2584449A1 (en) * 1985-01-31 1987-01-09 Vetco Offshore Ind Inc UPPER ASSEMBLY FOR MARINE EXTENSION TUBE, SELF-TENSIONING SLIDING JOINT, ROTATION BEARING SEAL, TUBULAR CONDUIT, SHIP AND METHOD USING THE SAME
US4712620A (en) * 1985-01-31 1987-12-15 Vetco Gray Inc. Upper marine riser package
US5069488A (en) * 1988-11-09 1991-12-03 Smedvig Ipr A/S Method and a device for movement-compensation in riser pipes
US6148922A (en) * 1996-05-13 2000-11-21 Maritime Hydraulics As Slip joint
US6173781B1 (en) 1998-10-28 2001-01-16 Deep Vision Llc Slip joint intervention riser with pressure seals and method of using the same
US20080271896A1 (en) * 2004-05-21 2008-11-06 Fmc Kongsberg Subsea As Device in Connection with Heave Compensation
US20080078880A1 (en) * 2006-09-29 2008-04-03 Airbus Uk Limited Aircraft fuel pipe coupling
WO2008051092A1 (en) * 2006-10-27 2008-05-02 Fmc Kongsberg Subsea As Telescopic joint
GB2456706A (en) * 2006-10-27 2009-07-29 Fmc Kongsberg Subsea As Telescopic joint
GB2456706B (en) * 2006-10-27 2011-05-18 Fmc Kongsberg Subsea As Telescopic joint
US20120325487A1 (en) * 2011-06-23 2012-12-27 David Wright Systems and methods for stabilizing oilfield equipment
US8746351B2 (en) * 2011-06-23 2014-06-10 Wright's Well Control Services, Llc Method for stabilizing oilfield equipment
US9441426B2 (en) 2013-05-24 2016-09-13 Oil States Industries, Inc. Elastomeric sleeve-enabled telescopic joint for a marine drilling riser

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