Abstract:
A drill ship is provided for conducting subsea operations, including intervention, maintenance and workover operations. The ship includes a hull having a substantially wide beam-to-length ratio and a deckspace. An automated system for handling tubulars and risers is mounted to the deck space, along with a pipe racking system. The deckspace includes a heavy-lift heave crane for handling seafloor operations and a medium duty crane mounted over the deckspace. The ship is configured to provide heavy lift subsea construction operations including 16-inch riser well intervention and workover programs, connected riser completion operations, and riserless tophole drilling and casing operations. The ship is also able to perform connected riser remedial drilling and slim hole well construction. The ship maximizes environmental efficiency in both construction and use, and provides a stable and safe work and living environment for operations personnel.

Description:
SUMMARY OF THE INVENTION 
       [0001]    In one embodiment, the drill ship is configured to operate in multi-tasking environments for subsea oil and gas field development and maintenance, including various subsea operations up to 7,500 feet of water depth. The drill ship includes capabilities for connected 16″ riser well intervention and work over programs, heavy lift subsea construction programs, connected 16″ riser small outer diameter tubing hanger completion programs, riserless tophole large outer-diameter drilling and casing batch programs, and connected riser remedial drilling and slim hole well construction. 
         [0002]    The design of the drill ship incorporates elements to ensure safety of personnel and environmentally efficient and “green” operation and construction. In particular, the ship exceeds the Mobile Offshore Drilling Unit (MODU) Passenger Vessel Intact and Damage Stability regulations. The design also incorporates concepts for protected temporary safe refuge muster concepts. Provisions on the ship are also made to form exhaust NOX emission reactors. 
         [0003]    The design of the ship&#39;s hull incorporates a small force “hull form” which provides low fuel consumption within an environmental class. Furthermore, the hull is double-hull compliant and includes nitrogen-blanketed hull methanol and helifuel storage capability. 
         [0004]    The deck of the ship includes automated deck tubular handling systems along with pipe racking systems and a riser handling system. Furthermore, knuckle-boom cranes are implemented on the deck for above-deck and subsea operations. Finally, a regulation-sized helipad is provided on the bow section of the ship. 
         [0005]    In the present embodiment, the light displacement hull includes a variety of operational areas and systems, including a blowout preventer (BOP) handling system, a 13⅝″ subsea BOP, a 16″ pressurized riser system, a box tower hoisting and lowering system with a top drive and an active heave compensated drawworks, the heavy-lift heave crane, and the medium duty deck crane. The power systems on the ship include a plurality of 2,200 horsepower fluid pumps and 2,200 horsepower cement units. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a slide view of a first embodiment of the drill ship of the present invention; 
           [0007]      FIG. 2  is a rear perspective view of the drill ship of  FIG. 1 ; 
           [0008]      FIG. 3  is a right front side perspective view of the drill ship of  FIG. 1 ; 
           [0009]      FIG. 4  is a right front side perspective view of the drill ship of  FIG. 1 ; 
           [0010]      FIG. 5  is a perspective view overlooking the deck of the drill ship of  FIG. 1 ; 
           [0011]      FIG. 6  is a right side perspective view of the hull of the drill ship of  FIG. 1 ; 
           [0012]      FIG. 7  is a rear, right side perspective view of the drill ship of  FIG. 1 , showing portions of the deck operational areas; 
           [0013]      FIG. 8  is a rear perspective view of the aft deck operational areas; 
           [0014]      FIG. 8   a  is a top plan view of the aft deck area of the ship of  FIG. 1 ; 
           [0015]      FIG. 9  is a side perspective view of the drill ship of  FIG. 1 ; 
           [0016]      FIG. 10  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0017]      FIG. 11  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0018]      FIG. 12  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0019]      FIG. 13  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0020]      FIG. 14  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0021]      FIG. 15  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0022]      FIG. 16  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0023]      FIG. 17  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0024]      FIG. 18  is a cross-sectional plan view of a portion of the drill ship of  FIG. 1 ; 
           [0025]      FIG. 19  is a perspective view of a portion of the deck of the drill ship of  FIG. 1 ; 
           [0026]      FIG. 20  is a top plan view of the drill floor for the ship of  FIG. 1 ; 
           [0027]      FIG. 21  is a side schematic view of a subsea BOP system with the embodiment of the drill ship of  FIG. 1 ; 
           [0028]      FIG. 22  is a perspective top view of the box tower hoisting and lowering system for use on the drill ship of  FIG. 1 ; 
           [0029]      FIG. 23  is a rear right-side perspective view of the heavy-lift active heave crane of the drill ship of  FIG. 1 ; 
           [0030]      FIG. 24  is an upper plan view of the rear portion of the deck of the drill ship of  FIG. 1 ; 
           [0031]      FIG. 25  is a perspective view of the medium duty deck crane for use on the drill ship of  FIG. 1 ; 
           [0032]      FIG. 26  is a cross-sectional view through the hull of the drill ship of  FIG. 1 ; and 
           [0033]      FIG. 27  and  FIG. 28  are schematic slender well construction examples for well operations using the drill ship of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hull and Main Ship Design 
       [0034]    As shown in  FIGS. 1-6 , the drill ship  1  includes a hull  10 , crew quarters structure at section  7 , a helipad  5  and a main deck  12 . Positioned on the aft region of the deck  12  are the box tower hoisting and lowering system and top drive  26 , a heavy-lift knuckle-boom seafloor active heave crane  50 , a medium duty seafloor and deck crane  60 , and an ROV installation with an integrated vessel control center  70 . 
         [0035]    As shown in  FIG. 1 , directional thrusters  3  are positioned at various points in the hull, and the engines and power systems are housed within the hull as shown at  2 . 4 azimuthing &amp; 1 tunnel variable frequency thrusters are used. (20.3 MW combined thrusters rating), and capability to allow for loss of 1 Thruster in a Worst Case Compartment or Component Failure Mode which complies with requirements for redundant dynamic positioning capability. 
         [0036]    The main hull  10  of the drill ship  1  is shown in the drawings at  FIGS. 1-6 . The hull  10  is formed for light displacement moderate environment conditions. In the preferred embodiments, the hull is 120 meters in length, 32 meters in breadth with an 8 meter operating draft. The drill ship has 23,000 metric tons of operating displacement, and utilizes 75% less shipyard steel fabrication weight than conventional newly-built drill ships. It is important to note that the hull includes a wide beam-to-length ratio to provide for improved deck operability. The hull form limits combined seas for operation Hs=4 m, Hmax=8 m, and the significant pitch is 2°. The connected standby meets the Hmax-11.8 m parameter. 
         [0037]    The hull has a DP-3 stationkeeping with +15 knot transit rating. The parameters for the hull are as follows:
       DP-3 Rating for 57 Knt wind, 2.5 Knt Current in Combined Beam Condition   4 Independent Engine Rooms, 22.6 MW combined generating power   Design Transit Speed+15 Knts   +30 Day F.O. Capacity in High Load Conditions   Panamax Compliant       
 
         [0043]    As shown in  FIGS. 1 and 2 , the hull  10  of the drill ship  1  includes a wide deck area  12  for subsea operations. The deck  12  includes an integrated system storage area  20  close to the control center  22  of the ship  1  as shown in  FIG. 7 . Also shown in  FIG. 7  is the helipad  5 , crew quarters  7 , a tubular storage area  24 , the box tower  26 , and a pipe racking and handling system  30 . All of these integrated systems are rated for a water depth of up to 7,500 feet. 
         [0044]    A perspective view of the deck  12  is shown in  FIG. 8 , which also shows the box tower hoisting and lowering system  26 , the heavy-lift heave crane  50  and the light-duty deck crane  60 . The large ultra high capacity load rated open aft deck  12  is suitable for a wide range of configurations. The loading on the ultra high capacity deck  12  is rated at 10-15 T/m2 (2,000-3,000 pounds/foot2). (Typically, on other types of global offshore drilling units, the load rating is only 500 pounds/foot2). The high deck load rating allows a wide range of subsea well and subsea construction activities to be conducted including storage of subsea trees, assembly of coiled tubing or wireline intervention equipment, staging of subsea construction elements, storage of drilling equipment and many others. The wide hull  10  allows for 1,050 m2 of usable unobstructed deck area. The deck area in the aft region is also shown in the top plan view  FIG. 8   a.    
         [0045]    As shown in  FIG. 9 , both the port and starboard sides of the hull  10  are integrated with the Remote Operated Vehicle (ROV) portion of the hull  10  is integrated with the ROV installation  70 . The ROV installation  70  preferably includes an integrated vessel control center, with a system designed for dual work-class ROV systems. Various integrated control centers and systems are shown as indicated in  FIGS. 10 and 11 . 
         [0046]    The hull design in the wide-beam of the ship allows for relatively large and comfortable crew quarters  7 , the configurations of which are shown for example in  FIGS. 12 ,  13  and  14 . As shown, the ship quarters  7  provides for 140-person quarters and project office facilities. As shown, 100 single man cabins  81  are shown and 20 dual man cabins  82  are provided. A plurality of mess areas  83  are provided along with a plurality of galleys  84  and storage compartments  85  in the crew area. 
         [0047]    In general, the cross-sectional layouts of the crew areas in relation to the hull  10  of the ship  1  are shown in  FIGS. 17 and 18 . Tubular storage area  24  is provided for vertical storage of the tubulars in the midsection behind the operational control center  22  for the ship, as shown in  FIG. 16 . A cross-sectional area, vertically through the hull  10  is shown at  FIG. 15 . Various below-water facilities and operational areas in the lower decks, including engines  2 , engine control rooms  91 , workshops  92  and various utility rooms  93  are shown in  FIGS. 15 and 16 . In general, the ship of the present embodiment includes seven decks above the bottom floor base  95  of the hull  10  at its highest elevation as shown in  FIG. 16 . 
       BOP Handling System 
       [0048]    The drill ship  1  includes a specialized and efficient handling system for the BOP as shown in  FIGS. 19 and 20 . The handling system  100  includes a hinged rig floor and unitized stack handling capabilities. Efficient workspace is provided by a driller control room  104  and vertical tensioning slip joint storage  106 . 
       Slender Riser and Subsea BOP System 
       [0049]    The Subsea BOP system utilized in the present embodiment is a 13⅝″,  10  ksi, NACE-compliant BOP stack. The BOP stack will be a conventional wellhead connector, double ram, annual ram, LMRP configuration. Optionally, a craneretrievable BOP/LMRP system may be provided with an infield wet storage of the deployed riser. Furthermore, 3, 4 or 5 ram stack options are available, dependent on the subsea test tree requirements in the program implemented. The riser may be a 16″ slender riser implementation. 
         [0050]    An MUX control system is also provided with 3.38″ ID kill-and-choke lines. A riser boost line is also provided and the system includes an EMI-pressurized 500 psi gas buster riser rating (in lieu of a diverter). Finally, the system includes a tensioning slip joint, all of which are shown in  FIG. 21 . 
         [0000]    Bog Tower Hoisting and Lowering System with Top Drive 
         [0051]    A box tower hoisting and lowering system with top drive and active heave compensation is provided at  26  as shown in  FIG. 22  and the foregoing figures. In the exemplary embodiment, the box tower is a 400 metric ton multipurpose tower implemented for vertical lifting above the deck  12 . The system includes a 400 metric ton heave-compensated AC drawworks and a 350 metric ton top drive. Finally, the tower includes a segmented traveling block system as shown. 
       Heavy-Lift Crane 
       [0052]    Importantly, the deck  12  of a ship  1  is implemented with a heavy-lift knuckle-boom, seafloor active heave crane  50  as shown in  FIG. 23  in the previous figures. The crane  50  in the exemplary embodiment of the drill ship  1  is rated at 250 metric tons. The crane  50  also includes a 250 metric ton rated single fall rated hook with capacity to 5,000 feet of water depth. Also, a 200 metric ton single fall rated hook is provided for a capacity to 7,500 feet of water depth. Higher load capacity can be accommodated into the crane design. Preferably, the crane includes a two-hour lowering speed to the rated depth at maximum loads. 
       Crane, Such as Medium Duty Crane 
       [0053]    As shown in  FIGS. 24 ,  25  and in the previous figures, the medium duty seafloor and deck crane  60  is also provided on the deck  12  of the ship  1 . The crane is a knuckle-boom deck utility crane nominally rated at 50 metric tons, and in the preferred embodiment includes a 15 kip seafloor rating to a water depth of 7,500 feet. The boom reach of the crane  60  covers the entire usable vessel deck area, including the aft deck  12 . Furthermore, the crane  60  preferably includes a pipe gripper arm for manipulating the tubulars from a tubular storage area  24 . 
       Fluid Power Systems 
       [0054]    As shown in  FIG. 26 , the ship  1  includes a plurality of fluid pump systems and cement units. In particular, the present embodiment includes four 7,500 psi, 2,200 horsepower quintaplex fluid pumps with precision AC drives. The system includes an option for a higher working pressure as well. Below deck, charging pumps in the special piping system maximize the usable tank volume relative to a 2,200 horsepower cement unit. The main system includes a 3,000 bbl NAF mud system including a 1,200 gpm fluid processing system. The system also includes a 3,000 bbl completion brine system with 1,880 gpm, 2 micron filtration system. Additional base oil and brine capacity can be incorporated into the design. 
       Slender Well Construction Examples 
       [0055]    The exemplary drill ship  1  of the present embodiment is capable of maintaining both large and slender casing schemes, the parameters of which are shown by the schematics of  FIGS. 27 and 28 . In particular, the large casing scheme is shown in  FIG. 27 , including the hole construction for a 16″ casing.  FIG. 28  shows the casing scheme for a slender 13⅜″ casing. 
       SPECIFICATION SUMMARY 
       [0056]    The following ratings, parameters and specifications are provided for the present embodiments of the drill ship  1 : 
       Design Criteria 
       [0057]      
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Water Depth 
                 7,500 ft. 
               
               
                   
                 Dynamic Positioning 
                 DP(AAA) 
               
               
                   
                   
               
             
          
         
       
     
       Derrick 
       [0000]    
       
         
           
             Multi Purpose Lift Tower 
             400 mt capacity 
             Segmented Traveling Block 
             350T Top Drive 
           
         
       
     
       Fluid Pumps 
       [0000]    
       
         
           
             4×2200 HP Quintaplex Pumps 
             High Volume and High Pressure Capability 
           
         
       
     
       Cranes 
       [0000]    
       
         
           
             250 mt deck mounted, heave compensated, crane for subsea construction, rated to 7,500 ft. water depth 
             50 mt deck mounted, knuckle boom crane with integral fast winch rated for 15 kips at 7,500 ft. water depth 
           
         
       
     
       Subsea BOP 
       [0066]    a. One Wellhead Connector, 13⅝″×18¾″
 
b. Two 13⅝″ Double Ram BOP Units
 
c. One 13⅝″ Annular Preventer
 
d. One 13⅝″ Lower Marine Riser Package Connector
 
       BOP Stack 
       [0000]    
       
         
           
             Crane Retrievable 
             Multiple configurations optimized for program 
             MUX control with acoustic &amp; ROV backup control 
           
         
       
     
       Operational Regions 
       [0000]    
       
         
           
             Moderate Environment Deepwater, Worldwide 
           
         
       
     
       Drawworks 
       [0000]    
       
         
           
             Active Heave Compensated 
             400 mt capacity 
           
         
       
     
       Cement Unit 
       [0000]    
       
         
           
             2000 hp×7500 psi WP quintaplex fluid pump 
             16″ OD Riser×14.85″ ID 
             75′ Joints Lengths 
             Two (2) 3.38″ ID 10,000 psi Choke and Kill lines 
             One (1) 1.40″ ID 5,000 psi hydraulic supply lines 
             One (1) 3.34″ ID×5,000 psi mud booster/circulating line 
             Pup Joints, for any 5′ increment 
             Buoyancy 
           
         
       
     
       Fluid Systems 
       [0000]    
       
         
           
             Mud Pits 3.000 bbl, minimum 
             Brine Pits 3,000 bbl, minimum 
             1,880 gpm 2 Micron Filtration System 
           
         
       
     
       Bulk Capacity 
       [0000]    
       
         
           
             Bulk Gel/Bar, 3,000 ft3 combined 
             Bulk Cement, 2,000 ft3 
           
         
       
     
       Helideck 
       [0000]    
       
         
           
             S61 or S92 Capable 
           
         
       
     
       Quarters for 140 Personnel 
       [0000]    
       
         
           
             100 private staterooms with bath 
             20 double staterooms with bath 
           
         
       
     
         [0089]    It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.