Abstract:
A vortex-induced vibration (VIV) suppression device including a body having a wall dimensioned to at least partly envelope a tubular member in an interior area of the body. The device further including a fin protruding outward from an exterior surface of the wall and a stand-off member positioned along an interior surface of the wall. The stand-off member dimensioned to space the body away from the tubular member and having a protruding portion formed by the interior surface of the wall and an indention portion formed by the exterior surface of the wall.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The application is a non-provisional application of co-pending U.S. Patent Application No. 61/580,461, filed Dec. 27, 2011 and incorporated herein by reference. 
     FIELD 
     Vortex-induced vibration (VIV) suppression devices having stand-offs to space the device from an underlying tubular. Other embodiments are also described herein. 
     BACKGROUND 
     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. 
     Helical strakes can be installed over the tubular to mitigate VIV. Helical strakes reduce the correlation of vortex shedding and thereby reduce the synchronization of vortex shedding forces required to produce large vibrations of a long slender tubular. 
     Typically helical strakes are bonded to the tubular or attached to the tubular so that the strake body is adjacent to the tubular surface. This causes a problem with many cathodic protection systems, which require the circulation of fluid adjacent to the tubular in order for the cathodic protection systems to function properly. Since the helical strake bodies are typically wrapped sufficiently tight against the tubular surface to restrict slipping on a vertical tubular, the cathodic protection systems may be compromised. In addition, the presence of helical strake body adjacent to the tubular surface can also produce unwanted thermal insulation. 
     SUMMARY 
     In accordance with an embodiment of the invention, a VIV suppression device is presented with indentations molded into the device that space the body away from an underlying tubular. The indentions can be dimensioned to be sufficiently wide to accommodate a band or banding tool for securely attaching the VIV suppression device to a tubular. The indentions can also be partially or fully filled with a filler to make the exterior surface of the VIV suppression device even. 
     In accordance with a further embodiment of the invention, stand-offs are attached to the interior surface of a VIV suppression device to space the majority of the body section away from an underlying tubular. The standoffs are dimensioned and positioned to allow a fluid to flow freely between the VIV suppression device and the tubular. Springs or other compressible materials may be used in the stand-offs to allow the VIV suppression device to accommodate changes in the diameter of the tubular. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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. 
         FIG. 1A  is a side view of one embodiment of a VIV suppression device with stand-offs on a tubular. 
         FIG. 1B  is a perspective view of one embodiment of the VIV suppression device with stand-offs of  FIG. 1A . 
         FIG. 1C  is a side view of one embodiment of the VIV suppression device with stand-offs of  FIG. 1A  with bands in the stand-offs. 
         FIG. 2A  is a perspective view of one embodiment of a body section of a VIV suppression device with stand-offs. 
         FIG. 2B  is a perspective view of one embodiment of another body section of the VIV suppression device of  FIG. 2A . 
         FIG. 3A  is a side view of one embodiment of a VIV suppression device with stand-offs that run along a longitudinal direction of the VIV suppression device. 
         FIG. 3B  is a cross-sectional view of one embodiment of the VIV suppression device with stand-offs along line A-A′ of  FIG. 3A . 
         FIG. 4A  is a side view of one embodiment of a VIV suppression device with round stand-offs. 
         FIG. 4B  is a cross-sectional view of one embodiment of the VIV suppression device with round stand-offs along line B-B′ of  FIG. 4A . 
         FIG. 5  is a side view of one embodiment of a VIV suppression device with stand-offs that run parallel to the fins on the VIV suppression device. 
         FIG. 6A  is a side view of one embodiment of a VIV suppression device on a tubular with fillers in the stand-offs. 
         FIG. 6B  is a cross-sectional view of one embodiment of the VIV suppression device with fillers in the stand-offs along line C-C′ of  FIG. 6A . 
         FIG. 7  is a side view of one embodiment of a VIV suppression device on a tubular with stand-offs and holes to allow for additional water circulation. 
         FIG. 8  is a side view of multiple VIV suppression devices fitted together end-to-end on a tubular. 
     
    
    
     DETAILED DESCRIPTION 
     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. 
     Referring now to an example embodiment of the invention in more detail,  FIG. 1A  presents VIV suppression device  100  on tubular  101 . In one embodiment, VIV suppression device  100  may be a helical strake including body  102 , fins  103  and stand-offs  104 . Body  102  may be formed by a substantially cylindrical wall  106  dimensioned to encircle tubular  101 . In some embodiments, wall  106  is a unitary structure which completely encircles underlying tubular  101 . In this aspect, to position VIV suppression device  100  around tubular  101 , body  102  is inserted over a free end of tubular  101  and shifted down the length of tubular  101  to the desired position. In other embodiments, wall  106  is formed in modular sections which are aligned with one another around a circumference of tubular  101  and secured together so that body  102  encircles tubular  101 . A VIV suppression device formed by modular sections will be described in more detail in reference to  FIGS. 2A and 2B . 
     Again referring to  FIG. 1A , in one embodiment, stand-offs  104  are formed by indentations in wall  106 . Stand-offs  104  may be oriented such that they that run along a circumferential direction of body  102 , as illustrated in  FIG. 1A . In one embodiment, stand-offs  104  are formed only along body  102  and between fins  103  such that they do not overlap with a portion of body  102  from which fins  103  extend. Stand-offs  104  may be formed as part of VIV suppression device  100  and molded into body  102  according to any suitable molding process (e.g., injection molding). 
     Still referring to  FIG. 1A , stand-offs  104  may be of any suitable depth, width and length. Typically stand-offs  104  will be 0.1 inches to 2 inches deep but may be as much as 12 inches deep. The depth of stand-offs  104  may vary, for example the depth may decrease to zero in order to allow a banding tool to install a band on the interior of the standoff and to allow room for the banding tool to operate. Stand-offs  104  may have a length that runs from one edge of fin  103  to an edge of the adjacent fin  103  but may be shorter than this or may run through fins  103 . Stand-offs  104  may be dimensioned to be sufficiently wide to accommodate a band or a banding tool. Stand-offs  104  will typically range from ½ inch to 12 inches wide and may vary in width along a single stand-off  104 . Any number of stand-offs  104  may be used and any number of bands may be used. The bands may lie on top of stand-offs  104 , inside stand-offs  104  (e.g., see  FIG. 1C ), or at a different location than stand-offs  104 . Stand-offs  104  may have any cross-sectional shape (e.g., square, rectangular, triangular or circular) and may be of the same shape or different shapes. In the illustrated embodiment, stand-offs  104  are substantially square shaped channels formed by three walls ( FIG. 1B  shows a better view of the cross-sectional shape of stand-offs  104 ). Stand-offs  104  may also be solid depending upon the manufacturing process used to make VIV suppression device  100 . Stand-offs  104  may run in any desired direction including along a circumferential direction of tubular  101  (as shown in the illustrated embodiment in  FIG. 1A ), along the longitudinal direction of the tubular (i.e., the expected flow direction, as shown in  FIG. 3A ), or helically such as parallel to fins  103  (as shown in  FIG. 5 ). This embodiment of the invention may apply to any VIV suppression devices such as, but not limited to, strakes or fairings. 
     Still referring to  FIG. 1A , in one embodiment, stand-offs  104  may be of the same material as body  102  of VIV suppression device  100  since it is molded as part of body  102 . Body  102  and stand-offs  104  may be made of any suitable material including, but not limited to, metals, plastics, composites, synthetics, fiberglass, rubbers and woods. Alternatively, stand-offs  104  can be formed separate from body  102  and made of the same or different material. 
     Referring now to  FIG. 1B , this figure shows a perspective view of VIV suppression device  100  with body  102  formed by wall  106 , fins  103  and stand-offs  104 . 
     Again referring to  FIG. 1B , this figure shows how stand-offs  104  appear as indentations on exterior surface  110  of wall  106  and appear as protrusions on interior surface  108  of wall  106 .  FIG. 1B  illustrates how stand-offs  104  can stop at the locations of fins  103 . This is so that VIV suppression device  100 , complete with body  102 , fins  103  and stand-offs  104 , can be formed as a single piece. This eliminates the need to attach stand-offs  104  as separate members. 
     Referring now to  FIG. 1C , this figure shows a side view of VIV suppression device  100  with body  102 , fins  103 , and bands  112  positioned inside stand-offs  104  to secure VIV suppression device  100  to underlying tubular  101 . In this embodiment, stand-offs  104  are dimensioned to be sufficiently wide to accommodate placing bands  112  inside the indentions formed by stand-offs  104 . Alternatively, bands  112  can be placed at different locations away from stand-offs  104 . Fillers can also be placed inside the indentions formed by stand-offs  104  to make the exterior surface of body  102  even (e.g., see  FIGS. 6A and 6B ), so that bands  112  can be placed on top of stand-offs  104 . Bands  112  may be any type of band or strap type mechanism dimensioned to encircle and secure a VIV suppression device around a tubular. 
     Referring now to  FIG. 2A  and  FIG. 2B , these figures show modular sections of a VIV suppression device which may be combined to form a VIV suppression device which can encircle an underlying tubular, such as that illustrated in  FIG. 1A .  FIG. 2A  shows VIV suppression device section  200 A which is formed by body section  202 A, fins  203  and stand-offs  204 .  FIG. 2B  shows VIV suppression device section  200 B which is formed by body section  202 B, fins  203  and stand-offs  204 . Body section  202 A, fins  203  and stand-offs  204  of VIV suppression device section  200 A may be formed as one piece, in that they are all molded into VIV suppression device section  200 A together. Similarly, body section  202 B, fins  203  and stand-offs  204  of VIV suppression device section  200 B may be formed as one piece. In one embodiment, the entire VIV suppression device (e.g., device  100  of  FIG. 1A ) can be made as a single piece and then cut it into any number of sections later. 
     Referring to  FIG. 2B , VIV suppression device section  200 B can be mated with VIV suppression device section  200 A of  FIG. 2A . Attachment of both halves can be performed by banding the two halves together around the tubular. It is also possible to bolt the two halves together or to attach them by any other suitable means (e.g., hinging two halves at one side and bolting on the other side). It is also possible to have one or more stand-offs  204  on one half of a VIV suppression device (e.g., VIV suppression device section  200 A of  FIG. 2A ) and not have any stand-offs  204 , or have a different number of stand-offs  204 , on the opposite half of a VIV suppression device (e.g., VIV suppression device section  200 B of  FIG. 2B ). 
     Referring now to  FIG. 3A , this figure shows a side view of VIV suppression device  300  with body  302 , fins  303  and stand-offs  304 . According to this embodiment, stand-offs  304  may run along the longitudinal direction of body  302  instead of circumferentially around body  302 , such as depicted in  FIGS. 1A ,  1 B,  1 C,  2 A, and  2 B. Stand-offs  304  may be discontinuous and oriented in various ways. Any number of stand-offs  304  may be used to restrict the majority of body  302  from contacting an underlying tubular. Representatively, in one embodiment, three stand-offs  304  may be formed between adjacent fins  303 . Alternatively, less than three (e.g., two or one) or more than three (e.g., four or more) stand-offs  304  may be formed between adjacent fins  303 . 
     Still referring to  FIG. 3A , in one embodiment of the invention, stand-offs  304  are dimensioned so that fluid can flow between body  302  and an underlying tubular. Such configuration is desired since if stand-offs  304  are too dense or are arranged to somewhat seal off the fluid around the tubular, stand-offs  304  may not effectively allow for fluid circulation. 
       FIG. 3B  shows a cross-sectional view of VIV suppression device  300  along line A-A′ of  FIG. 3A . VIV suppression device  300  includes body  302  formed by wall  306 , fins  303  and stand-offs  304 . From this view, stand-offs  304  running along the longitudinal direction of body  302  can be seen as indentions  304 A on exterior surface  310  of wall  306  and protrusions  304 B on interior surface  308  of wall  306 . Indentations  304 A and protrusions  304 B may have any cross-sectional shape (e.g., square, rectangular, triangular or circular) and may be of the same shape or different shapes. In the illustrated embodiment, indentation  304 A is a substantially square shaped channel having a bottom portion and sidewalls. Protrusion  304 B is also substantially square and has side walls and a top wall. 
     Referring now to  FIG. 4A , this figure shows a side view of another embodiment of a VIV suppression device having stand-offs. VIV suppression device  400  may include body  402 , fins  403  and stand-offs  404 . In this embodiment, VIV suppression device  400  includes several rounded stand-offs  404 . These rounded stand-offs  404  may be hemispheric shaped domes on the interior surface of body  402  (see  FIG. 4B  for a cross-sectional view of stand-offs  404 ), so that when VIV suppression device  400  is secured to a tubular, only the tops of these domes contact the underlying tubular. Any number of stand-offs  404  may be used to space body  402  of VIV suppression device  400  away from an underlying tubular. Stand-offs  404  may be of any suitable geometry and may appear circular, elliptical, rectangular, trapezoidal, or of any other shape when viewed from the outside such as in  FIG. 4A . 
       FIG. 4B  shows a cross-sectional view of VIV suppression device  400  along line B-B′ of  FIG. 4A . VIV suppression device  400  includes body  402  formed by wall  406 , fins  403 , and stand-offs  404 . From this view, a perspective of the hemispheric dome shape of stand-offs  404  can be seen. Stand-offs  404  may form protrusions  404 B on interior surface  408  of wall  406  and may form indentions  404 A on exterior surface  410  of wall  406 . Stand-offs  404  may be formed during the molding process of VIV suppression device  400  or may be attached after VIV suppression device  400  is formed. In embodiments where stand-offs  404  are attached to body  402 , indentations  404 A may be omitted. Stand-offs  404  may be made of any suitable material including, but not limited to, metals, plastics, composites, synthetics, and woods. In embodiments where stand-offs  404  are attached to body  402 , stand-offs  404  may also include a compressible material capable of regaining its original shape, such as a spring, or be made of a compressible material capable of regaining its original shape, such as rubbers. This allows VIV suppression device  400  to accommodate changes in the diameter of an underlying tubular. Stand-offs  404  may be made of the same material as body  402  or a different material than body  402 . 
     Referring now to  FIG. 5 , this figure shows a side view of one embodiment of VIV suppression device  500 , with body  502 , fins  503 , and stand-offs  504 . As shown in this embodiment, stand-offs  504  can run in a helical direction, parallel to fins  503 , around body  502 . As illustrated  FIG. 5 , there is one stand-off  504  formed between adjacent fins  503 . However, more than one (e.g., two or more) stand-offs  504  may be formed between adjacent fins  503 . 
     Referring to  FIG. 6A , this figure shows a side view of VIV suppression device  600  on tubular  601 . VIV suppression device  600  includes body  602 , fins  603  and fillers  605  which are dimensioned to fit within stand-offs  604 . Fillers  605  can be dimensioned to partially or fully fit into any stand-offs  604  present on body  602  of VIV suppression device  600 . Fillers  605  may be fitted to make the exterior surface of body  602  even (see  FIG. 6B  for a better view) so that a banding tool can optionally attach bands at the locations of stand-offs  604 . Without the presence of fillers  605 , the banding tool may be too wide to fit inside the indentions formed by stand-offs  604  and therefore unable to properly tighten a band. Fillers  605  may be pieces of a metal, plastic, composite, synthetic wood, rubber or any other resilient material or structure dimensioned to fit within any one or more of the previously discussed stand-off indentions. For example, in one embodiment, fillers  605  may be springs, or any other compressible material capable of regaining its original shape that can serve a spring function, to allow VIV suppression device  600  to accommodate changes in the diameter of underlying tubular  601 . Fillers  605  may also be pre-compressed for easy transportation and become uncompressed at time of application, such as a spray-able foam. 
     Still referring to  FIG. 6A , any number, size, and shape of fillers  605  may be used to partially or fully fill the indentations formed by stand-offs  604 . While fillers  605  will typically be held into place by bands that are placed over them, fillers  605  may also be permanently or temporarily bonded or attached to stand-offs  604  or body  602  of VIV suppression device  600 . This bonding or attachment may be made by any suitable means including chemical bonding and mechanical fastening. 
     Referring now to  FIG. 6B , this figure shows a cross-sectional view of VIV suppression device  600  along line C-C′ of  FIG. 6A . VIV suppression device  600  includes body  602  formed by wall  606  and fillers  605  dimensioned to fit within stand-offs  604 . Fins  603  are omitted for clarity. As illustrated in this embodiment, fillers  605  are dimensioned to completely fill indentions  604 A formed by stand-offs  604 , making exterior surface  610  of wall  606  even at the locations of stand-offs  604 . Alternatively, fillers  605  can be dimensioned to partially fill indentions  604 A formed by stand-offs  604 . Fillers  605  may be pieces of a metal, plastic, composite, synthetic wood, rubber or any other resilient material or structure dimensioned to fit within indentions  604 A. This view also illustrates an embodiment in which recesses  620  complementary to stand-offs  604  are formed within the exterior surface of tubular  601 . Recesses  620  are dimensioned to maintain an alignment of VIV suppression device  600  along the length of the tubular  601 . In this aspect, protrusions  604 B of stand-offs  604  may align with, and fit within, recesses  620  when VIV suppression device  600  is installed about tubular  601 . In some cases, recesses  620  may have a depth less than the height of protrusions  604 B such that a gap between the portions of interior surface wall  608  between protrusions  604 B and tubular  601  is maintained. It is to be understood, however, that recesses  620  are optional and therefore may be omitted such that tubular  601  has a substantially straight side wall and stand-offs  604  sit on top of the side wall. 
     Referring to  FIG. 7 , this figure shows a side view of VIV suppression device  700  on tubular  701 . VIV suppression device  700  includes body  702 , fins  703  and stand-offs  704  as previously discussed. In addition to stand-offs  704  to facilitate water circulation between VIV suppression device  700  and tubular  701 , VIV suppression device  700  may include holes  711  formed through body  702 . Holes  711  may allow water to flow through VIV suppression device  700 . Any number of holes  711  having any size and dimensions suitable to allow for flow of water through body  702  may be formed through body  702 . Holes  711  may be used in addition to stand-offs  704  to facilitate water flow, or instead of stand-offs  704  and stand-offs  704  omitted. 
       FIG. 8  shows a side view of multiple VIV suppression devices  800  fitted together end-to-end on tubular  801 . Each VIV suppression device  800  includes body  802 , fins  803  and stand-offs  804 . This view illustrates how multiple VIV suppression devices  800  can be fitted together end-to-end to completely envelope a section of tubular  801 . Fins  803  are positioned on VIV suppression device  800  such that when two VIV suppression devices  800  are placed next to each other end-to-end, fins  803  on one suppression device  800  align with fins  803  on the other device  800 . This allows for an easier molding process for producing VIV suppression devices  800  since VIV suppression devices  800  can be produced in smaller segments. Alternatively, multiple VIV suppression devices  800  can be formed all together during the molding process, and then cut into smaller segments after to produce each individual VIV suppression device  800 . 
     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. 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. 
     It should also be appreciated that reference throughout this specification to “one embodiment”, “an embodiment”, or “one or more embodiments”, for example, means that a particular feature may be included in the practice of the invention. Similarly, it should be appreciated that in the description various features are sometimes grouped together in a single embodiment, Figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects may lie in less than all features of a single disclosed embodiment. Thus, the claims following the Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment of the invention. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes can be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. For example, the stand-offs may be arranged on the helical strake to fit into an indention on the tubular to avoid slipping. Still further, although the VIV suppression device is illustrated as a helical strake, it is contemplated that stand-offs may be used in connection with any type of VIV suppression device in which a spacing between the device and underlying tubular is desired. For example, the stand-offs may be formed along a body portion of a fairing or any other VIV suppression device having a cylindrical or partially cylindrical body portion which encircles a tubular (e.g., a collar, a clamp, a Henning device, a smooth sleeve or a buoyancy or weighted material dimensioned to encircle a tubular). The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.