A helical strake segment including shell segments with, or without, discrete fins. Other embodiments are also described herein.
A difficult obstacle associated with the exploration and production of oil and gas is management of significant ocean currents. These currents can produce vortex-induced vibration (VIV) and/or large deflections of tubulars associated with drilling and production. VIV can cause substantial fatigue damage to the tubular or cause suspension of drilling due to increased deflections. A common device for suppressing VIV is a helical strake.
A helical strake may include a shell with fins attached to the shell in a helical arrangement to disrupt the flow. Helical strakes control the point at which the oncoming current separates from the helical strake thereby controlling, and shortening, correlation length of the vortex shedding. This decreased correlation length reduces VIV due to both weaker vortices and near random phasing of the various vortices that are shed along the tubular span.
The present invention is directed to methods for fabricating a helical strake using discrete fins and/or with minimal mold costs. A recent development for constructing a helical strake is to eliminate the shell and simply band rigid fins to the tubular, also referred to as banded fins. These fins, however, are difficult to construct. In addition, helical strakes having a shell are often still required on a portion of the tubular in order to coat the fins and shell with a coating to inhibit marine growth. While it is possible to produce an entire mold when a large number of helical strakes having a shell are required, it can be cost prohibitive when the quantity required is moderate or low. Thus, the instant invention proposes a method for fabricating a helical strake with a shell when the quantity of fins is moderate or low, and optionally when banded fins for the same size tubular are already being constructed. The invention further contemplates a cost effective method for fabricating helical strakes having a shell utilizing discrete fins.
Representatively, in one aspect, the invention is directed to a helical strake for suppressing a vortex induced vibration (VIV) of a tubular. The helical strake may include a shell dimensioned to at least partially encircle an underlying tubular and having at least one fin opening, and at least one fin dimensioned to be positioned within the at least one fin opening formed by the shell. The at least one fin may have a base portion dimensioned to be positioned along an underlying tubular and a tail portion dimensioned to extend through the at least one fin opening and radially outward from an underlying tubular. In some aspects, the at least one fin opening is an elongated opening having a longitudinal opening axis that is at an angle to a longitudinal shell axis of the shell. The at least one fin may include a plurality of fin segments that extend from a first end to a second end of the shell, or may be a continuous fin that extends from a first end to a second end of the shell. The shell may include a plurality of fin openings, and the plurality of fin openings are helically arranged around the shell. In some aspects, the at least one fin may include a plurality of fins that are helically arranged around the underlying tubular when positioned within the plurality of fin openings. The shell may include a first shell member, a second shell member and a third shell member that form at least three fin openings circumferentially spaced around an underlying tubular. The first shell member, the second shell member and the third shell member may be separate structures that each include a center portion positioned along the underlying tubular and a pair of flanges extending radially outward from the center portion, and wherein the fin openings are formed between the flanges of adjacent ones of the first, second and third shell members. In some embodiments, the at least one fin is a T shaped fin and the base portion is wider than the at least one fin opening. In addition, the strake may include a slot formed through the at least one fin, the slot dimensioned to receive a band for securing the at least one fin and the shell to the underlying tubular.
In another aspect, the invention is directed to a helical strake for suppressing a vortex induced vibration (VIV) of a tubular including a shell dimensioned to at least partially encircle an underlying tubular, the shell having a plurality of circumferentially spaced fin openings formed through the shell, and a plurality of fins dimensioned to be positioned within the plurality of circumferentially spaced fin openings, and wherein the plurality of fins are in a helical arrangement when positioned within the fin openings. The shell may include a plurality of shell members that are connected together to completely encircle the underlying tubular. In some cases, at least one opening of the plurality of circumferentially spaced fin openings is an elongated opening extending between a first end and a second end of the shell, and at least one fin of the plurality of fins is a continuous fin. In still further aspects, at least two openings of the plurality of circumferentially spaced openings are helically arranged between a first end and a second end of the shell, and at least one fin of the plurality of fins comprises at least two discrete fin segments positioned in the at least two openings. The plurality of fins may have a triangular shape comprising a base portion that is wider than the plurality of openings and rests against an underlying tubular while a tail portion extends through the plurality of openings.
In still further aspects, the invention is directed to a helical strake for suppressing a vortex induced vibration (VIV) of a tubular including a shell comprising a plurality of shell members that are dimensioned to at least partially encircle an underlying tubular, the shell members having a center portion that conforms to a shape of the underlying tubular and a pair flanges that extend radially outward from opposite sides of the center portion, and wherein the pair of flanges of one of the shell members are dimensioned to align with the pair of flanges of adjacent shell members to form a plurality of helical extension member along the underlying tubular. In some embodiments, the plurality of circumferentially spaced fin openings are formed between the flanges of the plurality of shell members, and the strake further comprises a plurality of fins dimensioned to be positioned within the plurality of circumferentially spaced fin openings. The flanges may conform to a shape of the plurality of fins positioned within the plurality of circumferentially spaced fin openings and hold the fins against an underlying tubular. Each of the plurality of fins may include a base portion that is positioned between the shell and the underlying tubular and a tail portion that extends through the plurality of fin opening. A fastener may be used to secure the flanges to each other or the plurality of fins.
The above summary does not include an exhaustive list of all aspects of the present invention. It is contemplated that the invention includes all apparatuses that can be practiced from all suitable combinations of the various aspects summarized above, as well as those disclosed in the Detailed Description below and particularly pointed out in the claims filed with the application. Such combinations have particular advantages not specifically recited in the above summary.
The embodiments disclosed herein are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and they mean at least one.
In this section, we shall explain several preferred embodiments with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the embodiments is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments may be practiced without these details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the understanding of this description.
The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the invention. Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like may be used herein for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising” specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.
The terms “or” and “and/or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and/or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.
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Helical strake segment 101 may be attached to tubular 100 by any suitable means including, but not limited to, banding, clamping, fastening, chemical bonding, or by the use of other intermediate structures. Shell 102 and fins 103 may have coatings or other structures on their interior or their exterior, or both their interior and their exterior, such as anti-fouling coatings or copper (or copper alloy) bar. Helical strake segment 101 may be of any suitable length, diameter, or cross section. Shell 102 may have any suitable length, diameter, or cross section and may have a cross section that varies along its length. Fins 103 may have openings for bands, springs, or other structures. Shell 102 may have openings for bands, springs, or other structures. Shell 102 and fins 103 may have openings for other reasons such as for heat transfer from or to the underlying structure or to improve the performance of an underlying cathodic protection coating, system, or structure. Shell 102 may have indentations so that part of shell 102 is spaced off of tubular 100. Openings 104 may be of any suitable size or shape.
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Representatively, in this embodiment, fins 123 are T-shaped in cross section and the ends (flanges) of shell members 122 are made to approximately match at least part of the T-shaped cross section. Fins 123 may have other similar shapes, for example fins 123 may have a base portion 170, such as the base of the inverted T in
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Fasteners 135 can be any type of fasteners suitable for attaching, or connecting, fins 133 to shell members 132. Representatively, fasteners 135 can include, but are not limited to, fastening with nuts, bolts, rivets, clamps, or other mechanical means, taping, welding or chemical bonding. Any number of fasteners 135 may be used for a single fin 133 or shell member 132 and fasteners 135, bolts 136, and nuts 137 may be of any size, shape, or quantity. Fasteners 135, bolts 136, and nuts 137 may be made of the same material or may be made of different materials.
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Shell members 142A, 142B, and 142C each extend around part of the circumference of helical strake segment 141. Each of shell members 142A, 142B an 142C may have edges that are raised (and extend away from the underlying tubular) and helical in shape so that edges of adjacent shell members 142A, 142B, and 142C can be adjoined to form helical strake segment 141 and the edges of adjacent shell members 142A, 142B, and 142C form the fins 143 of helical strake segment 141. Any number of shell members 142A, 142B, and 142C may be present and openings may be present in shell members 142A, 142B, and 142C with these openings used for any suitable purpose. For example, gaps in the edges of shell members 142A, 142B, and 142C may be used as channels for bands in fins 143 and may even contain springs for bands so as to accommodate changes in diameter of the underlying tubular. While
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The fins 103 may be similar to the previously discussed fins in that they can include a base portion 170 and tail portion 172. In this embodiment, the base portion 170 may be positioned on the outer surface of the shell 102. For example, the base portion 170 can be connected to the shell 102 at attachment region 169, which could be a weld joint. The fins 103 can be attached to the shell 102 before or after securing the shell 102 around the tubular. For example, in one aspect, the shell 102 is closed and secured at point 168 around the tubular, and then the fins 103 can be attached to the outer surface of the shell 102. It should further be recognized that in some aspects, the fins 103 are stiff or rigid enough to maintain a helical configuration on their own around a tubular and therefore do not need to be welded to the shell, or otherwise secured to the shell by another piece. Instead, once the shell 102 is positioned around the tubular, the fins 103 can be positioned around the shell 102 and will remain in place without welding. The fins 103 may also help hold the shell 102 around the tubular, without welding the fins 103 to the shell 102, due to their stiff or rigid helical shape.
The fins 103 may be similar to the previously discussed fins, except in this embodiment fins 103 may have a T shape. Representatively, fin 103 may include a base portion 170 made up of flanges 155, and a tail portion 157 that is perpendicular to the flanges 155 of base portion 170 such that they form a T shape. The flanges 155 (or widest portion of the fin) are attached (e.g., welded) to the outer surface of the shell 102 at attachment regions 169, as previously discussed. It should further be recognized that in some aspects, the fins 103 are stiff enough to maintain a helical configuration on their own around a tubular and therefore do not need to be welded to the shell. Instead, once the shell 102 is positioned around the tubular, the fins 103 can be positioned around the shell 102 and will remain in place without welding. The fins 103 may also help hold the shell 102 around the tubular, without welding the fins 103 to the shell 102, due to their stiff or rigid helical shape.
In broad embodiments, the present invention is directed to a helical strake segment including shell segments with, or without, discrete fins. The above aspects of this invention may be mixed and matched in any manner suitable to achieve the purposes of this invention. Other appurtenances for connecting various components may be utilized and each component may be manufactured by any suitable means. One or more anti-fouling coatings or structures may be applied to the inner surface, the outer surface, or both the inner and outer surface of any of the helical strake segments or components described herein. Each helical strake segment may have any number of slits and may be divided circumferentially into any number of section in any suitable manner including sections that are helical in shape. Attachments may be temporary such as for storage or installation or may be more permanent for field use. The helical strake sections may be attached around an underlying tubular by any suitable means including, but not limited to, banding, bolting, clamping, and chemical bonding.
While the foregoing written description of the invention enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. For several of the ideas presented herein, one or more of the parts may be optional. The invention should therefore not be limited by the above described embodiment, method, and examples, but by all embodiments and methods within the scope and spirit of the invention.
The application is a non-provisional application of co-pending U.S. Provisional Patent Application No. 62/618,046, filed Jan. 16, 2018, which is incorporated herein by reference.
Number | Date | Country | |
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62618046 | Jan 2018 | US |