Patent Publication Number: US-10329893-B2

Title: Assembly and method for dynamic, heave-induced load measurement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application having Ser. No. 62/134,059, which was filed on Mar. 17, 2015, and is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     In offshore drilling applications, oilfield tubulars (e.g., casing, drill pipe, strings thereof, etc.) are run from a drilling rig located on a marine vessel or a platform, down to the ocean floor, and then into an earthen bore formed in the ocean floor. In the case of the drilling rig being provided as a buoyant, marine vessel, the position of the vessel is affected by waves on the surface of the ocean. This position change is generally referred to as “heave.” 
     Rig vessels employ a variety of active and passive systems to limit heave; however, heaving movement of the vessel may still occur, for example, in rough seas. This may present a challenge, as the rig may support the oilfield tubular string deployed therefrom using a relatively rigid assembly, for example, including a spider, as compared to a hoisting assembly supporting the oilfield tubulars from flexible cables or compensating systems. Thus, when heaving movement of the rig occurs while the spider supports the oilfield tubular string, a force tending to move the upper end of the tubular string is applied thereto, while the inertia and/or other constraints applied to the position of the tubular string resist such movement. This represents a dynamic loading of the spider and/or the tubular string. Given the heavy weight of the tubular string and rig, such heave-induced dynamic loading may potentially reach dangerous levels. 
     What is needed are tubular support assemblies and methods for monitoring such dynamic loading so as to, for example, avoid damaging the rig structure or the tubular. 
     SUMMARY 
     Embodiments of the present disclosure may provide a tubular support assembly. The tubular support assembly includes a spider configured to support a tubular received therethrough, and a rotary table that supports the spider and transmits a vertical load applied to the spider to a rig floor. The tubular support assembly also includes a load cell configured to measure the vertical load. 
     Embodiments of the present disclosure may also provide a method for measuring dynamic load in an oilfield rig. The method includes coupling a load cell between at least two components of a tubular support assembly. The tubular support assembly includes a spider and a rotary table, with the rotary table being supported by a rig structure. The method also includes engaging a tubular using the spider. A vertical load is applied to the tubular support assembly when the spider engages the tubular, and a dynamic loading of the spider is experienced when the rig heaves. The method further includes measuring the dynamic loading using the load cell. 
     Embodiments of the disclosure may further provide an offshore drilling rig, which includes a floor through which a tubular is received and deployed into a well, a rotary adapter bushing through which the tubular is received, a spider received into the rotary bushing, the tubular being received through the spider, and the spider being configured to engage the tubular, to support a weight of the tubular, and a load cell positioned between the spider and the rig floor, the load cell being configured to determine a dynamic loading of the spider. 
     The foregoing summary is intended merely to introduce a subset of the features more fully described of the following detailed description. Accordingly, this summary should not be considered limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawing, which is incorporated in and constitutes a part of this specification, illustrates an embodiment of the present teachings and together with the description, serves to explain the principles of the present teachings. In the figures: 
         FIG. 1  illustrates a perspective view of a tubular support assembly, according to an embodiment. 
         FIG. 2  illustrates a perspective view of the assembly with the spider thereof removed, according to an embodiment. 
         FIG. 3  illustrates a perspective view of another tubular support assembly, according to an embodiment. 
         FIG. 4  illustrates a schematic view of a drilling rig, according to an embodiment. 
         FIG. 5  illustrates a flowchart of a method for measuring a dynamic load, according to an embodiment. 
     
    
    
     It should be noted that some details of the figure have been simplified and are drawn to facilitate understanding of the embodiments rather than to maintain strict structural accuracy, detail, and scale. 
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present teachings, examples of which are illustrated in the accompanying drawing. In the drawings, like reference numerals have been used throughout to designate identical elements, where convenient. In the following description, reference is made to the accompanying drawing that forms a part thereof, and in which is shown by way of illustration a specific exemplary embodiment in which the present teachings may be practiced. The following description is, therefore, merely exemplary. 
     In general, embodiments of the present disclosure may provide a tubular support assembly and a method for measuring a dynamic, vertical load applied by a string of tubulars supported by the assembly, for example, as induced by movement or “heave” of the drilling rig. In various examples, the tubular support system includes at least a spider and a rotary table, with the spider engaging the tubular and transmitting the weight of the tubular to the rotary table, which in turn is supported by the rig. As such, the tubular support system may have a relatively high rigidity, as compared to the hoisting systems from which tubulars are suspended while being lowered into the well. 
     To measure the loading of the spider, one or more load cells are provided in the tubular support system. For example, the load cell(s) may be disposed within the spider, so as to directly measure the force applied by the tubular onto the slips or bushing of the spider. In other examples, the load cell(s) may be disposed between the spider and the rotary table, e.g., between the spider and the rotary adaptor bushing. The load cell(s) may also or instead be positioned at any point between the rotary table and the rig floor, e.g., at the derrick mounts, so as to measure the loading of the spider via the loading of the derrick. In other embodiments, the load cell may be placed anywhere that vertical loading of the spider may be measured, e.g., between any two components through which the weight of the tubular is transmitted while the tubular is supported by the spider. In some cases, the load cells may be positioned closer to the tubular (i.e., with fewer components transmitting forces between the tubular and the load cell), as this may reduce a noise component of the signal produced by the weight of the components between the tubular and the load cell. However, in other cases, it may be easier or more reliable to place the load cells further way from the tubular. 
     Accordingly, the load cell may continuously (i.e., over time, whether analogue or at one or more sampling frequencies) measure the load on the spider, and thus on the rig and tubular string, as the tubular is supported in the tubular support assembly. Furthermore, the load data may be stored relative to the time domain over which the load measurements occurred. Storing load data according to a time domain allows the measured load data to be correlated to other data that may be similarly stored according to time domain, such as string raising/lowering dynamics, vessel heave, etc. Such continuous measurement may allow dynamic loading to be determined. For example, the load cell may produce signals, which may be interpreted by, for example, one or more processing components. The processing components may display, record, store, etc. the load thereon, e.g., specifically the dynamic loading amounts, which may provide useful data for rig design, operation, and/or the like. In a specific example, the dynamic loading history may be matched to a heave data history for the rig, and may facilitate determination of a load path for future loading and sea state conditions. The processing components may also be preset with alarm thresholds or the like, and may emit a warning when the dynamic loading is outside of the thresholds. 
     Turning now to the illustrated examples,  FIG. 1  depicts a perspective view of a tubular support assembly  100 , according to an embodiment. The assembly  100  generally includes a rotary adapter bushing  102 , a load cell  104 , and a spider  106 . The spider  106  and the load cell  104  may be supported in the rotary adapter bushing  102 . The rotary adapter bushing  102  may be supported by a rotary table (not shown in  FIG. 1 ), which may be supported by the rig floor, derrick mounts, etc., so as to transmit force eventually to the ocean in which the rig is buoyant. As shown, the load cell  104  may be formed as a cylindrical element; however, in other embodiments, the load cell  104  may be any other shape. In this embodiment, although not visible in  FIG. 1 , the rotary adapter bushing  102  includes an annular shoulder on its inner diameter. The load cell  104  is seated on this shoulder, such that a loading surface  107  thereof extends vertically upward from a top surface  109  of the rotary adapter bushing  102 . The spider  106 , in turn, is seated on the loading surface  107  of the load cell  104 , such that a vertical load applied to the spider  106  is transmitted to the rotary adapter bushing  102  via the load cell  104  and the shoulder. 
     An oilfield tubular (e.g., drill pipe, casing, stands thereof, strings thereof, etc.) may be lowered through the spider  106 , e.g., using a conventional hoisting and/or drilling system (e.g., elevator, draw-works, top drive, etc.). Once the tubular reaches a desired location, slips or a bushing, or any other engaging features of the spider  106  may be drawn radially inwards, so as to grip and/or otherwise support the tubular towards an upper end thereof. Thereafter, a next tubular may be hoisted and connected (“made-up”) to the tubular being supported by the spider  106 . Once the hoisted tubular is fully connected to the tubular supported by the spider  106 , the spider  106  may release the tubular, such that the tubular string weight is supported by the hoisting assembly of the rig, and then string may be lowered, potentially while being rotated, e.g., as part of drilling operations. Thereafter, the process of engaging the tubular with the spider  106  is repeated. Accordingly, the rotary adapter bushing  102  may be stationary with respect to the rig, e.g., may not be hoisted or otherwise suspended, such as by flexible cables, from the rig. 
       FIG. 2  illustrates a perspective view of the tubular support assembly  100 , with the spider  106  omitted to facilitate further viewing of the load cell  104 , according to an embodiment. The load cell  104  may include a first ring  200  and a second ring  202 , which may be separated axially apart from one another. The first ring  200  may provide the loading surface  107 , while the second ring  202  is seated on a shoulder  203  formed on the inner diameter  105  of the rotary adapter bushing  102 , as mentioned above. Ribs  204  may extend between the first and second rings  200 ,  202 . The load cell  104  may also include one or more strain gauges, which may provide an electrical signal that varies based on the distance between the first and second rings  200 ,  202 . Accordingly, under a vertically compressive load on the load cell  104 , e.g., as between the spider  106  ( FIG. 1 ) and the rotary adapter bushing  102 , the strain gauge may output a signal representative of the load. This may permit real-time, continuous monitoring of the load applied to the tubular string as it is supported by the spider  106 . 
       FIG. 3  illustrates a perspective view of another tubular support assembly  300 , according to an embodiment. In this embodiment, the tubular support assembly  300  includes a rotary table  302  and one or more load cells (three are visible:  304 , 306 ,  308 ), which may be located, for example, where the rotary table  302  meets the rig floor (not shown in  FIG. 3 ). The load cells  304 ,  306 ,  308  may be provided by any suitable type of load cell. The rotary table  302  may include a shoulder  309  formed on an inner diameter  310  thereof. Although not shown, a spider, configured to support a tubular string received therethrough, may be received into the inner diameter  310  and supported vertically by engagement with the shoulder  309  and/or with a top surface  312  of the rotary table  302 . 
     Accordingly, the load applied to the spider may be transmitted to the rotary table  302 . In turn, the load applied to the rotary table  302  may be transmitted to the rig floor (not shown) via the load cells  304 ,  306 ,  308 . Thus, similar to the tubular support assembly  100  described above, the tubular support assembly  300  may measure and provide a signal indicative of vertical load applied thereto by engagement between the spider and the oilfield tubular supported therein. 
       FIG. 4  illustrates a schematic view of an offshore drilling rig  400 , according to an embodiment. The rig  400  may be floating, as shown, on the surface  402  of a body of water, such as the ocean. In some embodiments, the rig  400  may be a marine vessel, i.e., a ship, but in other embodiments may be a platform that may be moved into position by a ship. The rig  400  may include hoisting and/or drilling equipment  404 , which may be configured to lower a tubular  406  through a rig floor  408  of the rig  400 . 
     The rig  400  may include the tubular support assembly  100 , as illustrated, but may additionally or instead include the tubular support assembly  300 , as described above, may include the rotary table  302  through which the tubular  406  is received. The rotary table  302  may be supported by the rig floor  408 . Further, the tubular support assembly  100  may include the spider  106 , the rotary adapter bushing  102 , and/or the load cell  104 , as shown in and described above with reference to  FIGS. 1 and 2 . Alternatively, as shown in  FIG. 3 , the load cells  304 ,  306 ,  308  may be positioned between the rotary table  302  and the rig floor  408 . 
     The tubular  406  may be received through a riser  409  to the ocean floor  410 . The tubular  406  may then be received through various subsea equipment  412 , such as one or more blowout preventers. 
     With reference to  FIGS. 1-4 ,  FIG. 5  illustrates a flowchart of a method  500  for measuring dynamic load in an oilfield rig, according to an embodiment. For convenience, the method  500  is described with respect to the above-described embodiments of the tubular support assemblies  100 ,  300 , but it will be appreciated that some embodiments of the method  500  may be executed using different structures. 
     The method  500  may include coupling a load cell between at least two components of a tubular support assembly  100 , as at  502 . In some embodiments, the tubular support assembly  100  includes the spider  106  and the rotary table  302 , with the rotary table  302  being supported by a rig floor  408 . Further, coupling the load cell  104  may include receiving the load cell  104  into an inner diameter of a rotary adapter bushing  102  coupled with the rotary table  302 . In such an embodiment, the vertical load applied by the tubular  406  on the spider  106  is transmitted to the rotary adapter bushing  102  via the load cell  104 . In another embodiment, several load cells  304 ,  306 ,  308  may be employed, and coupling the load cell includes positioning the load cell(s)  304 ,  306 ,  308  below the rotary table  302 , such that the vertical load on the rotary table  302  compresses the load cell(s)  304 ,  306 ,  308 . 
     The method  500  may also include engaging the tubular  406  using the spider  106 , as at  504 . A vertical load is applied to the tubular support assembly  100  when the spider  106  engages the tubular  406 . Further, a dynamic loading of the spider  106  is experienced when the spider  106  engages the tubular  406 , e.g., when the rig  400  heaves, e.g., in response to wave action on the surface  402  of the water. 
     The method  500  may thus further include measuring the dynamic loading using the load cell, as at  506 . In an embodiment, measuring the dynamic loading may include continuously measuring the vertical load on the spider  106  when the tubular  406  is supported in the tubular support assembly  100 . Further, the method  500  may include storing data representing the dynamic loading as a function of time. 
     The method  500  may also include determining a dynamic loading history based on the dynamic loading measured by the load cell, as at  508 . The method  500  may then also include matching the dynamic loading history to a heave data history for the rig, as at  510 . 
     While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the illustrated embodiment. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal. 
     Other embodiments of the present teachings will be apparent to those skilled in the art from consideration of the specification and practice of the present teachings disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims.