JPH0525993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention connects a first structure, such as a platform placed on the sea surface, and a second structure, such as an anchor foundation structure fixed to the seabed. The present invention also relates to a deformable rigid connection body for a riser pipe and a standpipe body for guiding a connecting member such as a pipe connecting these structures.

FIG. 10 of U.S. Pat. No. 3,976,021 shows a standpipe having an intermediate connection with a linear taper between the upper and lower surfaces of the connection. This intermediate connection is not fixed either on the top or on the bottom side. This US patent does not disclose curved slopes or optimal structures for such slopes.

U.S. Pat. No. 3,605,413 discloses a standpipe with a variable stiffness lower section interconnected with an upper section. The lower part or base is made of steel and has a non-uniform stiffness or non-uniform section modulus, which is greatest at the bottom of the base where it connects to the subsea structure and is attached to the upper part. It is smallest at the top of the base.

In order to meet such criteria, this patent shows that the foundation structure consists of a plurality of sections, each section having a different outside diameter and wall thickness. Each section has a different outer diameter, but the husband and wife have the same inner diameter. These sections are interconnected so that the lowermost section has the largest outer diameter and the upper sections have smaller outer diameters. Furthermore, at the interconnection part of each section,
A taper is provided to compensate for the different outer diameters of the connected sections. The patent states that such a slope can be extended along the entire section.

In addition to the diameter-varying section, the base consists of a rigid transition structure that prevents abrupt changes in radius of curvature and acts as a stress transfer member between the upper section of the standpipe and the upper section of the standpipe base.

Although this U.S. patent shows an intermediate connection consisting of components having different outside diameters, it does not show a connection having an outside surface that tapers continuously from the top of the connection to the bottom. do not have. Furthermore, this patent does not disclose an optimally configured intermediate connection having a substantially constant resultant force along the length of the structure.

Other documents known to the applicant as relevant prior art include U.S. Pat. No. 3,794,849, which connects a floating power plant to a stationary conductor connecting the power plant to the shore. A neutrally buoyant conductor is disclosed. The neutral buoyancy conductor is described as having constant inner and outer diameters and bending as a vertical curve for distributed stresses resulting from various loads. This US patent further discloses a vertical structure having a thickness that varies continuously from top to bottom in the drawings. The patent publication states that these are poured concrete revetments constructed to form ditches, but does not specify further.

Similar to U.S. Pat. No. 3,605,413, this U.S. patent also has an outer diameter that varies continuously from top to bottom to provide a nearly constant resultant force along the length of the connection. An intermediate connection which is optimally shaped is not disclosed.

US Pat. No. 3,559,410 is known which discloses a ring-shaped stress relief member. However, this U.S. patent discloses a longitudinally extending, continuously and curvilinearly varying outer diameter intermediate connection having a substantially constant resultant force along the length of the structure. Not yet.

Still other patents known to the applicant include walls of partially varying thickness attached between the lower part of the jacket and the pie to transfer horizontal loads therebetween. U.S. Pat. No. 3,512,811 discloses a jacket-to-pile connector that does the same. However, this U.S. patent describes a structure having a constant inner diameter but a curved outer diameter, and a longitudinal direction having a substantially constant resultant force along the length of the structure. does not show intermediate connections extending to

Finally, US Pat. No. 1,706,246 discloses a vertical structure with a continuously varying or tapered outer surface in its drawings. These vertical structures have walls that vary linearly in thickness from top to bottom. However, this patent does not indicate optimal design criteria or the benefits of having walls that taper in this manner. Moreover, this patent does not disclose an intermediate connection with such a tapered profile.

As can be seen from the above disclosure, there is a need for intermediate connections that connect subsea structures to subsea structures, among other things. Such a connection must also have an optimal construction for material savings and ease of manufacture, while exhibiting dimensions and strength capable of withstanding the varying loads applied to the connection.

However, as stated above, the prior art known and cited by the Applicant does not suggest an optimally configured structure that can be used to connect subsea structures to surface structures, particularly oil and gas production equipment. The above requirements are not met because the intermediate connections are not disclosed. In view of the shortcomings of the prior art, Applicants believe that no previously disclosed devices known to Applicants, alone or in combination, demonstrate the present invention.

The present invention provides a new and improved intermediate connection, namely:
The above and other disadvantages of the prior art are overcome by providing a deformable rigid connection for a riser. This connection is optimally configured to withstand the loads applied in normal use environments and, moreover, is economically and easily manufacturable due to its tapered profile. Also, assuming that the outer circumferential surface of the connecting body is made of many fibers, this outer circumferential surface is tapered, so the bending stress and tensile stress of these fibers are approximately equal to each other along the entire length of the connecting body. becomes constant. In addition, in this specification, the bending stress and tensile stress when considering the outer peripheral surface as a large number of fibers are referred to as outer fiber bending stress and tensile stress.

A deformable rigid connection for a riser pipe according to the invention has a top surface to which the first structure is connected; spaced from this top surface towards the bottom;
a bottom surface to which the second structure is connected; extending between, connecting and surrounding the top surface and the bottom surface, and having a continuous curved taper from the bottom surface to the top surface; When the taper is subjected to a predetermined axial load, shear load, and bending moment on the top surface, the composite stress determined as the sum of the bending stress and the axial stress has a constant distribution between the top surface and the bottom surface. an inner peripheral surface that is arranged concentrically with the outer peripheral surface, extends between the top surface and the bottom surface to connect them, and accommodates a connecting member between the two structures; The contour of the outer peripheral surface is set by the diameters of a plurality of cross sections, and this diameter is determined by the following formula, so that the constant distribution of the resultant stress is achieved. It is characterized by

where Dx=diameter of the cross section at distance x from the top surface, b=[−π/ ^32σd3 −T/8d−M−Sx−T _x sin(
x/Lθ)]/π/32σ where σ = total axial stress along the outer circumference (lbs/parallel feed); d = inside diameter of the above inner circumference (feet); T = tension at the top surface (lbs); ); M = moment at the top surface (in foot-pounds); x = distance measured along the circumference from the top surface toward the bottom (in feet); S = shear force at the top surface (in pounds); L = connection Length (in feet); θ = Angle from vertical at the top surface of the connection (in degrees) and In the formula, a=-4T/πσ The above resultant stress occurs when an axial load, a shear load, and a bending moment are applied.
Since this is almost the entire stress, the above-described effects can be achieved by configuring the connecting body so that this stress is uniformly distributed over the entire length of the outer circumferential surface. Such an outer circumferential surface is achieved by satisfying the above formula.

Note that the term "the distribution of the composite stress is constant" does not mean that it is constant in a strict sense, but rather that it is constant (almost constant) within the range allowed in this field.

This provides an optimal intermediate connection in terms of material economy and ease of manufacture, in addition to intermediate connections caused by bending moments generated by loads imparted to the structure from ocean currents, waves and platform movements. The desired strength against applied stresses is maintained.

Accordingly, from the above description, it is an object of the present invention to provide a new and improved intermediate connection.

Referring to the drawings, and in particular to FIG. 1, the apparatus is placed in a suitable environment of use. Intermediate connection 2 according to the invention as a connection for a standpipe with a fixed bottom
is schematically illustrated. Intermediate connection 2, in the preferred embodiment, is constructed of high strength steel and has a length of approximately 50 feet. This length is preferred because it is easy to manufacture and is long enough to retain the benefits of a theoretically optimal intermediate connection extending the full distance between the most distant points to be connected. Conceivable.

The intermediate connection part 2 is connected to a part of the submarine anchor platform structure 4 located on the seabed 6. This structure 4 has a wellhead body and a wellhead connector. The wellhead connection to which the intermediate connection 2 is connected at the base 8 may be a hydraulically actuated connection or a screw connection.
Since the bending moment caused by the load applied to the intermediate connection 2 is greatest at the base 8, this part must be large enough to withstand such stresses. Since the size and strength of the tunnel connector and other elements constituting the structure 4 are sufficiently larger than the base 8 of the intermediate connection 2, the base 8 is considered to be fixed.

At the end of the intermediate connection part 2 opposite the base part 8 there is a top part 1
0 is set. Since the load at the top 10 is not as great as the load at the base 8, the load at the top 10
It is not necessary to make the diameter as large as that of the base 8. Similarly, at the top 10, the intermediate connection 2 includes a pipe 12 which is preferably a 9 5/8 inch diameter stopper or standpipe in the embodiment schematically illustrated in FIG.
is connected to. The pipe girth 12 and the intermediate connection portion 2 constitute a standpipe assembly.

A girder 12 extends upwardly from the intermediate connection 2 to the sea surface platform 14. Platform 14 is a floating tension leg platform. The girth 12 is connected to the platform 14 by a connection 16, which in the preferred embodiment is a tension jack.

Platform 1 is installed inside the above-mentioned subsea structure.
4 and the seabed 6 are arranged. In the preferred embodiment described herein, conveying gutter 18 is a standpipe that conveys material obtained from the seabed to platform 14.

FIG. 1 further schematically depicts a member 20 disposed on the platform 14 and cooperating with the conveying girth 18 to control the conveyance of material on the conveying girth 18 on the platform 14. ing. Preferably, member 20 is a completed structure.

Referring now to Figures 2, 3 and 4, a preferred embodiment of the intermediate connection 2 is illustrated. The intermediate connecting portion 2 has a first top planar top surface 32, a second bottom planar bottom surface 34, a third outer circumferential surface 36 and a fourth outer circumferential surface 36.
It is constituted by a structural member 30 formed by an inner peripheral surface 38 of. The intermediate connecting portion 2 has first, second, third, and fourth surfaces 32, 34, 36, 3
solid within the area defined by 8.

Top plane 32 is annular and has an external contour defined by a predetermined diameter. This predetermined diameter is selected depending on the diameter and configuration of the tube girder 12 to which the intermediate connection is connected. A lower plane 34 is parallel to the top plane 32 and is also annular and has an outer contour defined by a diameter larger than the diameter defining the outer contour of the top plane 32. The top and bottom planes 32, 34 are spaced apart.

An outer surface 36 and an inner surface 38 define the structural member 30 longitudinally. An outer surface 36 extends between, connects to, and surrounds the outer contours of the top plane 32 and the bottom plane 34. The contour of the outer surface 36 is the lower plane 3
4 to the top plane 32 in a curved manner. An inner surface 38 similarly extends perpendicular to the surfaces extending between the top plane 32 and the bottom plane 34 to define a longitudinal bore through the structural member 30.

Referring now to FIG. 5, the tapered profile of the outer surface 36 is shown. This taper is formed over the entire length of the outer surface and is longer than the diameter of the largest cross section of the connection section, ie the lower plane 34. FIG. 5 schematically shows an intermediate connection 2 which is loaded, for example by ocean currents, waves or platform movements. These loads include a bending moment on the connection part 2, an axial tension load T, a shear load S, and
It carries another stress, indicated by the moment M. These stresses result in a composite stress of the bending stress applied along the length of the convexly curved outer surface of the intermediate connection and the tensile stress applied to the intermediate connection. In order to obtain an optimum intermediate connection, the contour of the outer surface 36 must be shaped in the present invention such that this resultant stress is substantially constant over the entire length of the intermediate connection. This is achieved by tapering the outer surface 36 by: The applicant discovered this equation and its underlying parameter definitions by combining certain assumptions and certain analyses. The assumption is based on the fact that the intermediate connection 2 is fixed at the base 8 as shown in FIG. 1 and that the internal bore defined by the inner surface 38 has a constant internal diameter as shown. . It was further assumed that the intermediate connection 2 is made of the same material as the tube 12 and that the stresses T, M, S are known.

Having made these assumptions and established Applicants' parameters as follows, the accompanying analysis was conducted: T = Tension, Top of Intermediate Connection (lbs.) M = Moment, Top of Intermediate Connection (Feet-lbs.) S = Shear stress, top of mid-joint in pounds θ = Angle from vertical, top of mid-joint in degrees L = Length of mid-joint in feet d = Inside diameter in feet x = Standpipe distance, measured from the top down (in feet) σ = Surface total axial stress (lbs/ ^ft2 ) A _x = Cross-sectional area at x ( ^feet2 ) D _x = Outside diameter at x (feet) I _x = Outside diameter at x (feet) Moment of inertia (foot ⁴ ) T _x , M _x , S _x , θ _x = Same as above, when the measurement beam at point x is minute, σ is defined by the following equation from the known beam theory (Here, the entire surface axis direction refers to the stress generated on the outer peripheral surface.
σ = M _x D _x /2I _x +T _x /A _x (2) Assuming T _x = T, x in the highest row
The total moment at (M _x ) is M _x = M + S _x + T _x sinθ _x (3) Assuming that θ _x changes linearly with x, θ _x = x/Lθ (4), and (3) and (4) Therefore, M _x = M + S _x + T _x sin (x/Lθ) (5) F = S + T sin (x/Lθ) (6) Thus, M _x = M + F _x . (7) Solving equation (2) for M _x and assuming T _x = T, M _x = (σ−T/A _x )2I _x /D _x (8) From equation (7) and equation (8), M + F _x = (σ - T/A _x )2I _x /D _x (9) By definition and standard formula; I _x = π/64 (D _x ⁴ - d ⁴ ) (10) A _x = π/4 (D _x ² −d ² ) (11) Equation (10), Eq.

Claims (1)

[Scope of Claims] 1. A top surface to which a first structure is connected; a bottom surface remote from this top surface toward the bottom and to which a second structure is connected; , connecting and surrounding them, and having a continuous curvilinear taper from the bottom surface to the top surface, the taper being such that the top surface is subjected to predetermined axial loads, shear loads, and bending moments. is applied, the resultant stress defined as the sum of the bending stress and the axial stress has a constant distribution between the top surface and the bottom surface; , an inner circumferential surface extending between the top surface and the bottom surface to connect them and accommodating a connecting member between the two structures; A deformable rigid connection body for a riser pipe, characterized in that the constant distribution of resultant stress is achieved by the diameter of the surface being determined by the following formula: where Dx=diameter of the cross section at distance x from the top surface, b=[−π/ ^32σd3 −T/8d−M−Sx−T _x sin(
x/Lθ]/π/32σ where σ = total axial stress along the outer circumference (lbs/parallel feet); d = inside diameter of the above inner circumference (feet); T = tension at the top surface (lbs) M = moment at the top surface (in feet-pounds); x = distance measured along the circumferential surface from the top surface toward the bottom (in feet); S = shear force at the top surface (in pounds); L = the force of the connection Length (feet); θ = angle from vertical at top surface of connector (degrees); and In the formula, a=-4T/πσ 2 The riser having a fixed bottom portion according to claim 1, wherein the bottom surface is configured to be fixed to a foundation structure constituting the second structure. Deformable rigid connections for pipes. 3. A deformable rigid connection for a riser having a fixed bottom as claimed in claim 1 or 2, wherein said top and bottom surfaces are annular surfaces. 4. A rigid deformable connection for a riser pipe as claimed in claim 1, 2 or 3, wherein the inner circumferential surface extends perpendicularly to both the top surface and the bottom surface. 5. Claims 1 to 4, wherein the connecting body is solid between the top surface, the outer peripheral surface, and the inner peripheral surface.
A deformable rigid connection for a riser according to any one of the preceding clauses. 6. A deformable rigid connection for a riser according to any one of claims 1 to 5, wherein the top surface and the bottom surface are parallel. 7 a pipe whose upper end is connected to a platform at sea level; a top surface of the pipe whose lower end is connected;
a bottom surface spaced apart from the top surface toward the bottom and connected to a subsea anchor foundation structure;
and having a continuous curved taper from the bottom surface to the top surface, the taper being such that when a predetermined axial load, shear load, and bending moment are applied to the top surface, the bending stress is applied to the top surface. an outer circumferential surface such that the resultant stress defined as the sum of an inner circumferential surface that extends to connect the two structures and accommodates a connecting member between the two structures; A standpipe solid body, characterized in that the constant distribution of resultant stress is achieved by having the diameter determined by the following formula: where Dx=diameter of the cross section at distance x from the top surface, b=[−π/ ^32σd3 −T/8d−M−Sx−T _x sin(
x/Lθ)]/π/32σ where σ = total axial stress along the outer circumferential surface (pounds/parallel feet); d=inner diameter (feet) of the inner circumferential surface; T=tension at the top surface (pounds/parallel feet); ); M = moment at the top surface (in foot-pounds); x = distance measured along the circumference from the top surface toward the bottom (in feet); S = shear force at the top surface (in pounds); L = connection Length (in feet); θ = Angle from vertical at the top surface of the connection (in degrees) and In the formula, a=-4T/πσ 8 The standpipe solid body according to claim 7, wherein the top surface and the bottom surface are annular surfaces. 9. The standpipe body according to claim 7 or 8, wherein the outer diameter of the top surface is equal to the outer diameter of the pipe girder. 10. The standpipe body according to any one of claims 7 to 9, wherein the connecting body and the pipe pipe are made of the same material. 11. The standpipe solid body according to any one of claims 7 to 10, wherein the top surface and the bottom surface are parallel.