Patent Publication Number: US-10309161-B2

Title: System and autonomous method for securing a riser support

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to BR 10 2016 021963-9, filed 23 Sep. 2016, which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to systems for securing connectors of risers in petroleum production units. 
     BACKGROUND OF THE INVENTION 
     With the discovery of hydrocarbon producing fields located at ever increasing water depths, the use of rigid structures fixed on the sea bed, intended for installation of production equipment, has become more complex by the day. In some cases, owing to the particular conditions of the region where the hydrocarbon producing field is located, their use has become unviable. 
     In more recent times, floating structures represent an alternative that is used more and more frequently for the installation of production equipment, as they normally offer a lower-cost option compared to fixed structures. 
     Petroleum production in deep water makes extensive use of riser pipes, also known as risers. This tubing, which may be flexible or rigid, collects the oil produced by the subsea well, and conveys it to a floating unit, and then to tankers, or directly to onshore installations. 
     The installation and dismantling of the risers in the structure of the floating unit are known as pull-in and pull-out operations. A pull-in/pull-out cable, connected to a submerged supporting system that supports a riser, suspends an assembly of the riser and supporting system until the connector of the latter engages in a support of the stationary production unit (SPU) and can be fixed and secured manually. 
     The company SBM has developed a system of wedges for fixing and securing the connectors of the supporting systems, especially for supporting systems of the I-tube type, illustrated in  FIG. 1 . 
     The fixing and securing of the connector of the supporting system is carried out with the assistance of divers, since these operations are not fully automated. 
     However, since the method for installing flexible risers conventionally employed in the prior art requires the use of divers and the mobilization of support ships, this method is subject to the sea conditions for a certain period of time. This dependence on the weather conditions may generate unexpected delays in projects, owing to the long waiting periods for good diving conditions. 
     In an attempt to solve this problem, some techniques for fixing and securing riser supporting systems may be found in the prior art. Some of them are described briefly below. 
     U.S. Pat. No. 7,373,986B2 discloses a connector for risers comprising a double-click securing system. In the pull-in operation, an enlargement or joint positioned in the upper portion of a riser enters a pocket fixed to the structure of a platform. A joint or enlargement comprises supporting surfaces comprising cams that engage in recesses of the pocket. The pockets are arranged side by side and the engagement of the cams is guided by guides that move the cams angularly until they are located on the recesses. Then the riser is lowered until the cams engage in the recesses. 
     U.S. Pat. No. 5,947,642A describes a device for coupling flexible risers comprising a tensioner provided with a projection and an angularly moveable retainer for securing the projection automatically when the tensioner is raised into a cylindrical pocket. 
     U.S. Pat. No. 7,967,070B2 also discloses a connector comprising a funnel/guide assembly to be coupled to an underwater structure, wherein the funnel/guide assembly receives a shaft. The shaft is coupled to a tensioner. A securing assembly is coupled to the funnel/guide assembly, wherein the securing assembly comprises a securing device. Retainers move into and out of the funnel/guide assembly, wherein the retainers are inserted into recesses of the shaft for securing the axial movement of the shaft relative to the funnel/guide assembly. The connector is installed and secured using a remotely operated vehicle (ROV). 
     Although the prior art comprises various devices and systems for securing supporting systems or tensioners of risers, many of them are complex and/or require precise adjustments for said securing. Moreover, many will need at least the assistance of a ROV, which may make the pull-in/pull-out operation unviable in extreme sea conditions. 
     As will be explained in detail hereunder, the present invention aims to provides a simple, low-cost alternative for automatic installation and securing of supporting systems. 
     SUMMARY OF THE INVENTION 
     It is an aim to provide a system and autonomous method for securing a riser support that preferably does not require diving operations for manual connection and disconnection of the system or the need for the assistance of a ROV. 
     Thus, in order to achieve this aim, the present disclosure provides an autonomous system for securing or releasing a riser support, wherein the autonomous system comprises at least one or more of the following features: a riser support connectable at its bottom end to a submerged riser and at its upper end to a tensioning element, the riser support having a connector; a supporting ledge comprising a through-hole, through which the tensioning element and at least part of the riser support may pass; a securing device located on the supporting ledge, said securing device being slidable relative to the supporting ledge and driven by an actuator; wherein the securing device is configured to slide, with respect to the through-hole, between an unlocked position and a locked position, wherein, in the locked position, the securing device can engage the connector of the riser support after the connector has passed through the through-hole of the supporting ledge, so as to prevent the connector from passing back through the through-hole. 
     According to another aspect of the disclosure, there is provided an autonomous method for securing a riser support, wherein the method comprises one or more of the steps of: passing, through a through-hole of a supporting ledge, at least part of a riser support connected at its bottom end to a submerged riser and at its upper end to a tensioning element; and sliding, relative to the supporting ledge, a securing device located on the supporting ledge, said securing device being driven by an actuator, wherein the securing device slides between an unlocked position and a locked position relative to the through-hole, wherein, in the locked position, the securing device can engage with a connector of the riser support after the connector has passed through the through-hole of the supporting ledge, so as to prevent the connector from returning through the through-hole. 
     According to another aspect of the disclosure, there is provided an autonomous method for releasing a riser support, wherein the method comprises one or more of the steps of: providing a securing device in a locked position on a supporting ledge, engaged with a riser support, so as to prevent the riser support passing through a through-hole of a supporting ledge, wherein the riser support is connected at its bottom end to a submerged riser and at its upper end to a tensioning element; sliding, relative to the supporting ledge, the securing device, said securing device being driven by an actuator, wherein the securing device slides between the locked position and an unlocked position relative to the through-hole in the supporting ledge, so as to disengage from the riser support; and passing, through the through-hole of the supporting ledge, at least part of the riser support. 
     According to another aspect of the disclosure, there is provided an autonomous system for securing a riser support, comprising (i) a riser support connected at its bottom end to a submerged riser and at its upper end to a tensioning element, (ii) a supporting ledge comprising a through-hole through which the tensioning element and at least part of the riser support pass, and (iii) a securing device located on the supporting ledge, the securing device sliding relative to the supporting ledge and actuated by an actuating means, wherein the securing device slides between an unlocked position and locked position on the through-hole, wherein, in the locked position, the securing device can engage with locking in a connector of the riser support after the connector has passed through the through-hole of the supporting ledge. 
     The present disclosure further provides an autonomous method for securing a riser support, comprising the steps of (i) passing, through a through-hole of a supporting ledge, at least part of a riser support connected at its bottom end to a submerged riser and at its upper end to a tensioning element and (ii) sliding, relative to the supporting ledge, a securing device located on the supporting ledge, the securing device being actuated by an actuating means, wherein the securing device slides between an unlocked position and a locked position on the through-hole, wherein, in the locked position, the securing device can engage with locking in a connector of the riser support after the connector has passed through the through-hole of the supporting ledge. 
     According to one aspect of the disclosure, there is proposed an autonomous system for securing a riser support, characterized in that it comprises one or more of the following features: a riser support connected at its bottom end to a submerged riser and at its upper end to a tensioning element; a supporting ledge comprising a through-hole, through which the tensioning element and at least part of the riser support pass; a securing device located on the supporting ledge, said securing device sliding relative to the supporting ledge and driven by an actuator; wherein the securing device slides between an unlocked position and a locked position on the through-hole, wherein, in the locked position, the securing device can engage with locking in a connector of the riser support after the connector has passed through the through-hole of the supporting ledge. 
     A further aspect of the disclosure provides that the securing device slides on at least one rail located on the supporting ledge. 
     A further aspect of the disclosure provides that the securing device is lockable in the locked position by means of at least one locking pin that can engage in at least one securing hole of the supporting ledge. 
     A further aspect of the disclosure provides that the at least one locking pin is driven by at least one hydraulic locking cylinder. 
     A further aspect of the disclosure provides that the actuator is at least one hydraulic displacement cylinder. 
     A further aspect of the disclosure provides that the securing device comprises a horseshoe shape where there is a front opening for positioning said securing device around the connector of the riser support. 
     A further aspect of the disclosure provides that the securing device comprises an upper surface that comes into contact with the connector of the riser support, inclined in at least one direction relative to a bottom surface. 
     A further aspect of the disclosure provides that the inclination of the upper surface of the securing device relative to at least one direction corresponds to at least one of the catenary angle and the azimuth angle of the riser. 
     A further aspect of the disclosure provides that the riser support is a support of the I-tube type or MFBM. 
     A further aspect of the disclosure provides an autonomous method for securing a riser support, characterized in that it comprises one or more of the steps of: passing, through a through-hole of a supporting ledge, at least part of a riser support connected at its bottom end to a submerged riser and at its upper end to a tensioning element; sliding, relative to the supporting ledge, a securing device located on the supporting ledge, said securing device being driven by an actuator, wherein the securing device slides between an unlocked position and a locked position on the through-hole, wherein, in the locked position, the securing device can engage with locking in a connector of the riser support after the connector has passed through the through-hole of the supporting ledge. 
     A further aspect of the disclosure provides that it comprises an additional step of locking the securing device in the locked position by means of at least one locking pin that can engage in at least one securing hole of the supporting ledge. 
     A further aspect of the disclosure provides that it comprises an additional step of unlocking the securing device in the locked position by releasing at least one locking pin of the at least one securing hole of the supporting ledge. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The detailed description presented hereunder refers to the appended figures and their respective reference numbers, representing the embodiments of the present disclosure. 
         FIG. 1  shows a system of wedges for fixing and securing connectors of supporting systems of the I-tube type as known in the prior art. 
         FIG. 2  shows an isometric view of a portion of a body of a SPU where the system of the present disclosure can be installed. 
         FIG. 3  shows a detailed isometric view of a preferred embodiment of the system of the present disclosure in a locked position. 
         FIG. 4  shows an isometric view of the preferred embodiment of the system of the present disclosure in an unlocked position where a connector has not yet passed through a through-hole of a supporting ledge. 
         FIG. 5  shows an isometric view of the preferred embodiment of the system of the present disclosure in an unlocked position where the connector is passing through a through-hole of the supporting ledge. 
         FIG. 6  shows an isometric view of the preferred embodiment of the system of the present disclosure in an unlocked position where the connector has already passed through a through-hole of the supporting ledge. 
         FIG. 7  shows an isometric view of the preferred embodiment of the system of the present disclosure in an intermediate position where a securing device is being moved for securing the connector. 
         FIG. 8  shows a detailed isometric view of the preferred embodiment of the system of the present disclosure in the locked position. 
         FIG. 9  shows a detailed isometric view of the securing device according to a preferred disclosure of the present invention. 
         FIG. 10  shows four views of the securing device of  FIG. 9 , namely a front view, a side view, a bottom view and an isometric bottom view. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Firstly, it is emphasized that the description that follows will be based on a preferred embodiment of the disclosure. As will be obvious to a person skilled in the art, however, the invention is not limited to this particular embodiment. 
       FIGS. 2 to 8  show isometric views of a portion of a body  10  of a stationary production unit (SPU) where the system of the present disclosure is installed. 
     The present system comprises a supporting ledge  20 , which is submerged. The ledge  20  comprises a through-hole  22  through which a tensioning element  30  can pass. Tensioning element  30  is a steel cable in some embodiment. In some embodiments, tensioning element  30  is at least part of a riser support  32 . The supporting ledge  20  is fixed relative to the body  10  of the SPU. 
     A riser support  32 , which can also make up part of the proposed system, is connected at its bottom end to a submerged riser  34 . The riser support  32  is connected at its upper end to the tensioning element  30 . 
     In some embodiments, the riser support  32  is a support of the I-tube type or of the multifunctional bell mouth (MFBM) type, usually employed for supporting risers in SPUs. 
     Optionally, the tensioning element  30  passes via a deflection pulley  36 . This allows for directing the loading of the riser support  32  and, consequently, of the submerged riser  34 . 
     Once the tensioning element  30  and at least part of the riser support  32  have passed through the through-hole  22  (as shown in  FIG. 3 ), as a result of the tensioning of the tensioning element  30 , the riser support  32  can be secured relative to the supporting ledge  20  by means of a securing device  40  positioned thereon. 
     The securing device  40  slides between an unlocked position ( FIGS. 4 to 6 ), away from the through-hole  22 , and a locked position ( FIG. 8 ) on the through-hole  22 . 
     In some embodiments, the securing device  40  slides on at least one rail  24 . The rail  24  can be located on the supporting ledge  20 . In some embodiments, two rails are provided on the supporting ledge  20  for sliding of the securing device  40 , as illustrated in the detail in  FIG. 2 . Optionally, stops  25  are positioned at one or both ends of any rail, to limit the movement of the securing device  40 . 
     In the locked position, the securing device  40  can engage with locking in a connector  38  of the riser support  32  after the connector  38  has passed through the through-hole  22  of the supporting ledge  20 , so as to prevent the connector  38  from passing back through the through-hole. That is, once the connector has passed through the through-hole  22  to be on the same side of the through-hole  22  as the securing device  40 , the securing device  40  can prevent the connector  38  from returning. In some embodiments, the connector  38  comprises an annular projection for coupling into the securing device  40 . 
     In some embodiments, the securing device  40  comprises a horseshoe shape, where there is a front opening  42  for positioning said securing device  40  around the connector  38  of the riser support  32  and coupling to the annular projection thereof. That is, the front opening  42  can fit under the annular projection on the riser support  32 , and the tension in the riser support  32  then biases the annular projection towards the securing device  40 , thus securing riser support  32  against the securing device  40 . This is discussed in further detail below. 
     Preferably, the securing device  40  is lockable in the locked position by means of at least one locking pin  44 . In some embodiments, locking pin  44  can engage in at least one securing hole  26  of the supporting ledge  20  (as shown in  FIG. 2 ). In some embodiments, two locking pins are provided for coupling in two securing holes of the supporting ledge  20 . 
     In some embodiments, the at least one locking pin  44  is actuated by at least one hydraulic locking cylinder  46 . Thus, when the securing device  40  is in the locked position, the at least one hydraulic locking cylinder  46  actuates the at least one locking pin  44  for coupling into the at least one securing hole  26  of the supporting ledge  20  and for securing the riser support  32 . That is, the hydraulic locking cylinder can hydraulically propel the pin  44  into the securing hole  26 . To disconnect the system, the at least one hydraulic locking cylinder  46  can be actuated so as to uncouple the at least one locking pin  44  from the at least one securing hole  26  of the supporting ledge  20 . In this way, the securing device  40  becomes free to move between the locked and unlocked positions. Sliding the securing device  40  to the unlocked position removes the securing device  40  from underneath the annular projection of the connector  38  of riser support  32 , thus releasing the riser support  32  from the securing device  40 . 
     Sliding of the securing device  40  between the locked and unlocked positions is effected by means of an actuator  48 . In some embodiments, the actuator  48  is at least one hydraulic displacement cylinder. The hydraulic displacement cylinder can be fixed at one end to the securing device  40 . The other end of the hydraulic displacement cylinder can be fixed to a fixing element  49  of the supporting ledge  20 . 
     In some embodiments, the securing device  40  can further comprise an upper surface, which will come into contact with the connector  38  of the riser support  32 . The upper surface can be inclined in at least one direction relative to a bottom surface of the securing device  40 , as illustrated in the front and side views in  FIG. 10 . As can be seen, angles X and Y are formed in two mutually perpendicular directions. This promotes better coupling of the upper surface of the securing device  40  with the connector  38  of the riser support  32 . In other words, the sloped upper surface discourages the connector  38  from sliding out of the securing device  40  whilst the securing device  40  is in the locked position. The angles X and Y will vary according to the catenary angle and/or the azimuth angle of the riser  34 . In some embodiments, the angles X and Y can correspond to the catenary angle and/or the azimuth angle of the riser  34 . The angles X and Y can also vary according to the angle of the supporting ledge  20 . 
     In some embodiments, a centralizing cap  37  (e.g. see  FIG. 4 ) is provided below the riser support  32 . Also, in some embodiments, a flexible joint (also known as a flex joint)  39  is provided at the upper end of the riser  34  (i.e. below the riser support  32 , as shown in  FIG. 6 , or below the centralizing cap  37 , if present, as shown in  FIG. 5 ). 
     Optionally, each of the components of the system of the present invention may be treated with at least one of a sliding coating, in the case of moving parts, and an antifouling coating. 
     The present disclosure also provides a method associated with the system proposed above, comprising the steps of: (a) passing, through the through-hole  22  of the supporting ledge  20 , at least part of the riser support  32  connected at its bottom end to the submerged riser  34  and at its upper end to the tensioning element  30 ; and (b) sliding, relative to the supporting ledge  20 , the securing device  40  located on the supporting ledge  20 , the securing device  40  being driven by the actuator  48 . 
     In the proposed method, the securing device  40  can slide between an unlocked position and a locked position on the through-hole  22 . In the locked position, the securing device  40  can engage with locking in the connector  38  of the riser support  32  after the connector  38  has passed through the through-hole  22  of the supporting ledge  20 . 
     The steps of the method can be performed without direct user manipulation, and can instead be performed remotely. That is the action of passing the riser support  32  through the through-hole  22  can be controlled by applying tension to the tensioning element  30  through a remotely controlled tensioning or winding system, for example. The action of sliding can be controlled by remotely operating actuator  48 . 
     In some embodiments, the method can comprise an additional step of locking the securing device  40  in the locked position by means of at least one locking pin  44 . The locking pin  44  can be a pin that engages in at least one securing hole  26  of the supporting ledge  20 . 
     In some embodiments, the method can comprise an additional step of unlocking the securing device  40  from the locked position. This can be achieved by releasing at least one locking pin  44  from the at least one securing hole  26  of the supporting ledge  20 . 
     Thus, the present disclosure provides a system and an autonomous method for securing a riser support that does not require diving operations for manual connection and disconnection of the system or the need for the assistance of a ROV. 
     Numerous variations falling within the scope of protection of the present application are permitted. Thus, it is emphasized that the present invention is not limited to the particular configurations/embodiments described above. Modification of the above-described apparatuses and methods, combinations between different variations as practicable, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the spirit and scope of the claims.