Patent Publication Number: US-8540029-B2

Title: System and apparatus for drilling riser conduit clamp

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/204,760, filed 9 Jan. 2009, titled “System and Apparatus for Drilling Riser Conduit Clamp.” 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system and method for clamping, engaging and disengaging conduit connections in oil and gas wellhead risers, wherein the wellhead equipment of the well is positioned below the surface of the water. 
     2. Description of Related Art 
     In subsea drilling operations, as in any drilling operation, drilling fluid must be circulated through the drill bit in order to cool the bit, carry away the cuttings and provide hydrostatic head pressure against the formation to aid in the prevention of blowouts. This drilling fluid is normally returned to the floating vessel by means of a large diameter pipe, known as a riser, which extends between the subsea wellhead assembly and the floating vessel or rig at the water&#39;s surface. The lower end of this riser is connected to the BOP and wellhead assembly which is generally located adjacent the ocean floor, and the upper end usually extends through a centrally located opening of the floating vessel or fixed rig. A drill string extends downward through the riser into earth formations lying below the body of water, and drilling fluids circulate downwardly through the drill string, out through the drilling bit, and then upwardly through the annular space between the drill string and the riser, returning to the vessel or rig. 
     Buoyancy or ballasting devices may be attached to the submerged portion of the riser. These devices may be comprised of syntactic foam attached on the outer elements of the riser section. These buoyancy devices create upwardly directed forces in the riser, compensating for the compressive stresses created by the riser&#39;s weight preventing riser failure. 
     In an underwater drilling rig riser, multiple lines are integrated in the rig riser. These include multiplexed hydraulic lines, choke lines, boost lines and an Installation/Workover Control Systems (IWOCS) line. In conventional installations, the failure of a riser or its release from the subsea installation due to tripping of a blowout preventer cuts these various lines as they are integrated in the riser. The present invention presents an improved riser clamp to securely hold the various lines in place as well as allowing for the selective release of the all important IWOCS line away from the riser for easy replacement or continued control of the subsurface wellhead assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment of the invention, there is shown a clamp for securing about annular casing via a centrally oriented aperture having a radius having at least one aperture for grasping a longitudinally extending accessory disposed about the radius of the centrally oriented aperture, and at least one fastening member for securing the longitudinally extending accessory about the clamp, wherein the at least one fastening member and the at least one aperture act to secure a longitudinally extending accessory relative to the annular casing. 
     The primary advantage of the invention is to improve equipment reliability by providing a clamp to hold subsurface control lines within the confines of an underwater drilling rig riser and allow easy access to said lines for maintenance, replacement or separation from the riser in case of failure. 
     Another advantage of the invention is that the line clamps are integrated to provide support for the permanently attached lines to prevent the buckling of the lines during pressurization. 
     Another advantage of the invention is that the clamps holding the removable lines, which are fitted and removed during a riser run/pull do not have to be physically removed as per the conventional systems and are locked inside the floatation perimeter to prevent damage and creating a safety hazard on board the rig or platform. 
     Other objects and advantages of the present invention will become apparent from the following descriptions, taken in connection with the accompanying drawings, wherein, by way of illustration and example, an embodiment of the present invention is disclosed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The invention and its preferred embodiments and preferred mode of use and further objectives and advantages thereof, will best be understood by reference to the following detailed description when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  illustrates an offshore drilling system configured for dual gradient riser drilling and depicting riser clamps in gapped areas between riser floatation modules. 
         FIGS. 2A and 2B  illustrate a riser clamp in accordance with a preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Detailed descriptions of the preferred embodiment are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the issued claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure or manner. 
     In oil, gas and mineral production various hydraulic operated pumps; valves, connectors, tubing and piping are used to extract oil, gas or other minerals from the subsurface strata. These devices are arranged in a manner to safely extract oil, gas or other minerals in a liquid or gaseous form under pressure and allow redundancy in case of failure of one or more of the component parts. To that end, drilling riser component parts are typically integrated into sustained operations of an oil, gas or mineral field. 
     In a preferred embodiment,  FIG. 1  illustrates a typical offshore drilling site where a drilling vessel  10  floats on a body of water  12  which overlays a pre-selected drill site. Drilling rig  14  is positioned in the middle of drilling vessel  10 , above moon pool  16 . Moon pool  16  is a walled opening that extends through drilling vessel  10  and through which drilling tools are lowered from drilling vessel  10  to a sea floor or mudline  18 . At mudline  18 , structural pipe  20  extends into wellbore  22 . Wellhead assembly  24  and adjacent blowout preventer  26  are run to mudline  18 . A riser system  28  as shown in  FIG. 1  typically includes one or more auxiliary lines (well-control lines and boost line) on the outside of a riser. As is illustrated in  FIG. 1 , a plurality of buoyant floats  30  surrounds a riser. A plurality of well control lines such as a choke line, multiple hydraulic lines, boost line and integrated components are either embedded within the floats running parallel with the riser or adjacent to the riser floats. Between each float is riser, clamp ( 32 ) which securely holds the well control lines in place with the riser floats or adjacent to the riser floats. 
     Drilling vessel  10  can include additional riser clamps  32  which can be employed to hold various pieces of equipment. For example, in certain embodiments, as is shown in  FIG. 1 , a riser clamp  32  may be disposed near the opening of the moon pool and used to maintain a piece of equipment that is not susceptible to high pressures, such as a device employed to measure water temperature and current flow. At another depth, as is illustrated near the middle of the drill string in  FIG. 1 , another riser clamp  32  can be employed to further maintain the same or another line. At an even deeper location, an additional riser clamp  32  can be employed to maintain another line or series of lines which can be used for yet another purpose, such as powering a device measuring the flow rate of fluids flowing through. 
     In numerous instances, a single line or a plurality of lines can be connected to each of riser clamps  32 . In certain embodiments one line may adapt to one riser clamp located at a particular depth and adapt to another riser clamp at another depth, after bypassing one or more riser clamps. Riser clamps  32  may be employed to draw tension among one or more lines running along various lengths of riser system  28 . In certain embodiments a singular riser clamp  32 , similar to what is shown in  FIG. 1 , can be located near the ocean floor can be employed to couple a line near the bottom of the ocean floor, in order to allow a line to move almost independent of riser system  28 . Such an embodiment would be ideal in the event that a drill string needed to be removed from the ocean floor. Numerous riser clamps  32  can be employed and allowed to independently and selectively release various lines as becomes necessary. Such an embodiment would be ideal in the event that numerous lines were coupled to riser system  28  and only particular lines needed to be released from riser system  28  at various depths. For example, in the event that a particular event occurs such as completion of a fracturing technique and only particular lines of communication need to be maintained, riser clamps  32  that are used to maintain a line measuring fluid flows can be selectively released from riser system  28 , while lines measuring bottom hole pressure can be a maintained at their present position. Allowing for selective removal of lines along riser system  28  via riser clamps  32  provides for a lack of congestion along a typical string. Further, when particular lines carrying various signals are allowed to be selectively removed prior to removal of a riser system  28  from the ocean floor, the potential for tangling of lines is severely reduced. 
       FIGS. 2A and 2B  illustrate cross sectional views of an exemplary riser clamp of the preferred embodiment of the invention in both the closed ( FIG. 2A ) and open ( FIG. 2B ) positions. Riser clamp  40  fits around drilling rig riser  42  and securely holds multiplexed electronic and hydraulic line clamps  44 , choke lines  46 , boost line  48  and an Installation/Workover Control Systems (IWOCS) line clamp  50 . As shown, two extensions support choke lines  46  and line clamps  44  shown in  FIG. 2B . One extension supports a clasp that holds boost line  48  and IWOCS line clamp  50 . Clamp  40  may be made of plastic or any other material and is fashioned to allow IWOCS line clamp  50  and multiplex electronic &amp; hydraulic line clamps  44  to permit disengagement from the riser assembly when clamp is in the open position ( FIG. 2B ) and the riser is being pulled.  FIG. 2B  shows the position of the floatation riser situated against the flat top of the riser clamp on five radial extensions. Clamp  50  is outside the periphery of the flotation when in the closed positioned. See  FIG. 1  which shows a series of clamps  32  positioned above each section of floatation  30 . Clamp  50  may be configured with, detents positioned to hold the clamp in an open position when not in use or when being pulled. 
     In certain embodiments, clamp  40  can be employed to secure about riser system  28  via a centrally oriented aperture having a radius. At least one aperture for grasping a longitudinally extending accessory such as a choke line, a hydraulic line, a boost line or other integrated components is disposed about the radius of a centrally oriented aperture. Additionally, at least one fastening member such clamp  40  may be employed for securing a longitudinally extending accessory such as a line choke, a hydraulic line, a boost line or other integrated components about clamp  40 . In certain embodiments, at least one fastening member and at least one aperture may act to secure a longitudinally extending accessory relative to riser system  28 . In certain embodiments, riser system  28  may be annular casing or any other type of drill string. 
     In particular embodiments, similar to what is shown in  FIG. 2A , riser clamp  40  can include a casing component, which provides for protection and security of a line or other member secured by riser clamp  40 . In such embodiments, as is illustrated in  FIG. 2A  riser clamp  40 , may be coupled to an opposing portion of riser clamp  40 , via a mechanism that allows a riser clamp  40  to swing out, while maintaining its coupling to another portion of riser clamp  40 . In other embodiments, riser clamp  40  can be made such that portions of riser clamp  40  detachably configure as separate components to couple with one another around a riser or portion of a riser. In certain embodiments, portions of riser clamp  40  can be configured to allow lines, cables or tubing, to attach once riser clamp  40  is coupled to a riser or portion of a riser. For example, as is illustrated in  FIG. 2A , riser clamp  40  can first be coupled and secured to a riser via aperture  42 . Proper lines may then be disposed about riser clamp  40  via apertures  46  and  48  and subsequently remaining portions of riser clamp  40  may then be connected to secure lines in place. 
     In other embodiments, riser clamp  40  can be oriented such that numerous lines individually couple to exterior portions as is illustrated in  FIG. 2B . In this particular embodiment, lines may extend through individual apertures and are capable of being released through individual clamping mechanisms. Such clamping mechanisms are ideal in high pressure environments and those in which certain lines are capable of collapsing due to changes in pressure and temperature. 
     In certain embodiments, multiple apertures may be employed for coupling longitudinally extending accessories about a riser system  28 . For example six apertures may be employed to couple longitudinally extending accessories relative to riser system  28 . When it is desirable to release one or more of the longitudinally extending accessories, each accessory may be individually released from an aperture via clamp  40 . In certain embodiments combinations of longitudinally extending accessories may be released via a single clamp  40  or multiple clamps  40 . Additionally, riser clamp  32  may be released from rig riser  42  via securing mechanisms disposed about multiplexed electronic and hydraulic lines  44 . 
     While the invention has been described in connection with a preferred embodiment, it is not intended to limit the scope of the invention to the particular form set forth, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the later filed claims.