Patent Publication Number: US-2010108322-A1

Title: Parallel drilling and completion for a dry tree floating production facility

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit, under 35 U.S.C. §119(e), of Applicant&#39;s co-pending U.S. Provisional application No. 60/896.988. filed Mar. 26, 2007, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This disclosure relates to the field of offshore drilling for, and production of, undersea liquid and gaseous hydrocarbon deposits (i.e., natural gas and petroleum). More specifically it relates to a system and a method for performing exploratory and/or field development drilling simultaneously with performing completion and production work from the same offshore structure. 
     The floating structures or facilities used for the development and production of offshore hydrocarbon deposits frequently employ “dry production trees” (production structures and equipment installed at the topside of the production riser system), either by themselves, or in combination with “wet production trees” at the bottom or seabed end of the riser system. The dry production trees are an extension of the well bore through a riser and production tubing system from the seabed and up to the floating facility production deck area or well bay. This riser and production tubing is hung off in a surface wellhead system, this system being supported by a top tensioned riser hang-off system. The purpose of this top-tensioned riser system is to support the surface wellhead loads and to compensate for the relative motion between the surface wellhead and the floating facility. For a floating facility to be able to support such a riser system, strict requirements are set for its motion characteristics with respect to limitations in the overall relative motions, such as vertical heave and pitch and roll characteristics. 
     There are presently several different approaches for achieving a dry tree-based drilling and completion program. One method is based on pre-drilling the development wells using a Mobile Offshore Drilling Unit (MODU) prior to installing the permanent floating facility. The subsequently-deployed permanent facility will employ a smaller tie-back and completion rig for doing tie-back on the production risers and then doing the final completion work to start production. 
     Alternately, offset drilling may be used, in which a MODU performs field development drilling in close proximity to a Dry Tree Unit (DTU) that performs conviction and production work. A fixed or skiddable drill set is installed onto the DTU to perform a sequential drilling and completion program. This drill set can be a full drilling rig with support systems or a Tender Assisted Drill (TAD) set. 
     The above-described current methodologies, other than offset drilling, require a sequential execution program in which doing field development drilling precedes completion by dry tree well drilling and then well completion. Offset drilling, while permitting simultaneous field development and completion/production, is dependant upon favorable environmental conditions for conducting close proximity operations with the MODU and DTU. 
     The above-described sequential or environmentally-restricted operations have up to now been acceptable from an execution time perspective to achieve first oil and plateau rate production, as the water depths and reservoir depths have been sufficiently shallow to enable drilling and completion of each well within a two-to-four month time frame. With the new significant energy reserves confirmed in ultra-deep water areas (e,g., water depths of 2000-3500 meters or more), and hydrocarbon reservoirs below the sub-salt or pre-salt formations, the combination of water depth, reservoir depth, high pressures and temperatures, and formation challenges, has had a significant impact on the drilling and completion time for each individual well. Exploration wells may require six to nine months drilling time, and in a field development program the drilling time can be an additional three to six months, with a subsequent three month completion program. Thus, for an average size field in an ultra-deep water environment in the Gulf of Mexico), a total field development drilling program of seven to nine years could be envisioned for a sub-salt field development program. 
     It would therefore be an advance in the state of the art to provide a system and a method for improving the efficiency of performing field development drilling and well completion/production for deep-water offshore reserves and thus reducing the time expended to bring such reserves into production. It would also be advantageous to increase this efficiency and thus reduce the overall time span from initiation of field development to commencing production in a way that is less sensitive to environmental conditions than has heretofore been achievable. Furthermore, it would be advantageous to provide such a system and method that would allow field development work and completion/production work to be performed simultaneously, and yet fully independently so as to avoid the one interfering with the other. 
     SUMMARY 
     Broadly, the present disclosure, in one aspect, relates to a system for performing both field development drilling and completion/production work in “parallel” (in the temporal, rather than physical sense). The system comprises a floating facility having a deck with a moon pool and a well bay, a first or drilling rig fixed to the deck over the moon pool and that is operable for field development drilling (including exploratory drilling) through the moon pool, and a second or completion rig movably mounted on the deck over the well bay, and that is operable for performing well completion and production functions through the well bay while the first rig is performing field development drilling. 
     In another aspect, the present disclosure relates to a method for simultaneously performing field development drilling and well completion and production functions from a single floating facility having a deck with a drilling moon pool and a well bay, comprising (a) positioning the facility in a first field development position for performing field development drilling at a first well location through the drilling moon pool; (b) using a first or drilling rig fixed to the deck over the drilling moon pool to perform field development drilling at the first well location through the drilling moon pool; (c) moving the facility to a second field development position for field development drilling at a second well location; (d) using the drilling rig to perform field development drilling at the second well location through the drilling moon pool; (e) during the performance of the field development drilling at the second well location, positioning the facility, as necessary, to a first completion position in which the first well location is accessible through the well bay; and (t) using a second or completion rig movably mounted on the deck above the well bay to perform well completion work at the first well location through the well bay while field development drilling is being performed at the second well location. 
     This brief summary has been provided so that the nature of the disclosure may be understood quickly. A more complete understanding of the disclosure may be obtained by reference to the following detailed description of the preferred embodiments thereof in connection with the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an axonometric perspective view of a floating offshore facility or structure incorporating the parallel field development drilling and completion system of the present disclosure; 
         FIG. 2  is a side elevational view of the facility of  FIG. 1  showing a drilling riser deployed from a, fixed drilling rig, and a completion/production riser deployed from a movable completion rig in accordance with the present disclosure; 
         FIG. 2A  is a detailed view of a drill string and drilling riser as may be deployed by the fixed drilling rig of the facility of  FIG. 1 ; 
         FIG. 3  is a rear elevational view of the facility of  FIG. 1 , as viewed from the right side of  FIG. 2 ; 
         FIG. 4  is plan view of the of the facility of  FIG. 1 , taken along the line  4 - 4  of  FIG. 3 ; 
         FIG. 5  is a top plan view of the deck of the facility of  FIG. 1 , taken along line  5 - 5  of  FIG. 3 ; 
         FIG. 6  is a diagrammatic view showing the riser slot configuration through the hull structure of the facility of  FIG. 1 , showing the drilling moon pool and the well bay used for completion/production work, with the corresponding layout of the seabed wellheads; 
         FIG. 7  is a top plan view of the movable completion rig and its associated hydraulic jack skidding apparatus situated over the well bay of the facility of  FIG. 1 . 
         FIG. 8  is a cross-sectional view of a portion of the hydraulic jack skidding apparatus shown in  FIG. 7 , taken along line  8 - 8  of  FIG. 7 ; 
         FIG. 9  is a cross-sectional view taken along line  9 - 9  of  FIG. 8 ; 
         FIG. 10  is a cross-sectional view taken along line  10 - 10  of  FIG. 8 ; and 
         FIGS. 11A-11D  are semi-schematic devotional views of the facility of  FIG. 1 , showing the steps of the method of performing field development drilling in parallel with completion/production work, in accordance with the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings,  FIGS. 1 ,  2 , and  3  show a floating offshore facility or structure  10 . The specific structure shown is a platform of the type known as an extended-draft platform (EDP), but other types of structures known in the art, such as tension-leg platforms (TLP&#39;s), SPARs, and deep-draft semi-submersible platforms, may be used. Indeed, is will be readily appreciated, any floating structure capable of supporting a dry tree completion/production system may be employed. EDP&#39;s, such as the structure  10 , are well-known in the art, as exemplified by U.S. Pat. No. 7,037,044, the disclosure of which is incorporated herein by reference. Briefly, the structure or EDP  10  comprises a hull structure  12  supported above the water surface by several (typically three or four) adjustable-buoyancy columns  14 , attached at their bottom ends to a heave-plate  16  having a central aperture  17 . The hull structure  12  includes several decks, of which only an upper deck or top deck  18  is shown. The upper or top deck  18  supports the drilling, completion, and production apparatus, as will be described in detail below, as well as other structures and equipment, such as, for example, a crew quarters  20  and one or more cranes  22 . 
     The EDP  10  is secured to the seabed by a mooring system comprising a set of mooring lines  24  extending from the structure, such as from the heave plate  16 , as shown. The mooring lines  24  are controlled by winches (not shown), which are operable to shift the position of the EDP  10  relative to the seabed, as will be discussed below. Alternatively, a dynamic (powered) positioning system, of a type well-known in the art, may be employed. 
     The hull structure  12  is provided with two openings or “moon pools” extending through all of the decks to provide access to the seabed. The first, smaller moon pool is a drilling moon pool  26  (see  FIGS. 2 ,  5 , and  6 ), while the second, larger moon pool is a well bay  28  that accommodates a plurality of production riser slots, as will be described below. 
     Fixed to the upper deck  18  over the drilling moon pool  26  is a first or fixed drilling rig  30  that is operable for field development drilling into an undersea hydrocarbon reservoir (not shown) beneath the seabed  32 . The field development drilling is performed with a drill string  34  operated from the fixed drilling rig  30  and deployed through the drilling moon pool  26 . The drill string  34  is advantageously deployed through a high-pressure drilling riser  36  fixed to a sub-sea wellhead  38  installed by the fixed drilling rig  30 . 
     A second, movable completion rig  40  is movably supported over the well has  28  so as to allow it to be shifted or translated relative to the well bay  28 , in a plane substantially parallel to the top deck  18 . The shifting or translation of the movable rig  40  may advantageously be accomplished by a hydraulic jack skidding apparatus  42  (to be described in detail below) that is fixed to the upper or top deck  18  over the well bay  28 . The completion rig  40  performs the “tie-back” operation by deploying a production riser  44  that extends through the well bay  28  and connects, at its bottom end, to the wellhead  38 . Production tubing (not shown) is deployed by the completion rig  40  through the production riser  44  down into the well (not shown) through the seabed wellhead  38 . The tubing is suspended from a connection at the dry tree apparatus (not shown) that is fixed to the top end of the production riser  44 . The upper end of the production tubing within the production riser is hydraulically and mechanically connected to the dry tree apparatus by conventional means well-known in the art. The well bay  28  is dimensioned to accommodate a plurality (typically six to twelve or more) of predefined positions or “slots”  46  (see  FIGS. 5-7 ), each of which receives one production riser  44 . To this end, a grid structure (not shown) may be installed in the well bay  28  to define the riser slots  46 . See, for example, U.S. Pat. No. 6,692,193, the disclosure of which is incorporated herein by reference. 
       FIG. 6  shows, schematically, a typical layout of the wellheads  38  (“well splay”) after completion is performed on a number of wells within a particular subsea wellhead area  48  corresponding to the number of production riser slots  46  in the well bay  28 . The drilling moon pool  26  and the drilling riser  36  are shown within the subsea wellhead area  48 , and a plurality of production risers  44  is shown within the well bay  28 . The arrangement of the well has  28  relative to the drilling moon pool  26  is such that the drilling riser  36  and the production risers  44  can be deployed and accessed independently and without interference, using the method of parallel development drilling and well completion/production described below. 
       FIGS. 7-10  illustrate the hydraulic jack skidding apparatus  42  on which the movable completion rig  40  is advantageously mounted. The skidding apparatus  42  comprises an elevated rail structure comprising a pair of parallel longitudinal beams  50  supported above or on the upper or top deck  18  by a plurality of vertical supports  52  ( FIGS. 2 and 3 ). A skid platform  54  is slidably mounted on a pair of parallel transverse beams  56  that, in turn, are slidably mounted on the longitudinal beams  50 . Each of the beams  50 ,  56  has horizontal flange  58  fixed to its top surface by means of a rail element  60 . The completion rig  40  is fixed to the skid platform; therefore, the skid platform  54  has an aperture  62 , over which the completion rig  40  is mounted, through which the production risers  44  are deployed. 
     The skid platform  54  is translatable longitudinally with respect to the top deck  18  along each of the longitudinal beams  50  by a first or longitudinal hydraulic gripper jack system  64 , and it is translatable transversely along each of the transverse beams  56 , by a second, or transverse hydraulic gripper jack system  66 . Thus, there are preferably two longitudinal hydraulic gripper jack systems  64  acting in concert, and two transverse hydraulic gripper jack systems  66  acting in concert. The hydraulic gripper jack systems  64 ,  66  may advantageously of the type marketed by Bardex Corporation, of Goleta, Calif. (www.bardex.com), under die trade name “Bardex Gripper Jack.” Briefly described, each of the gripper jack systems  64 ,  66  comprises a pair of hydraulic jacking cylinders  68  fixed to a hydraulic friction lock device  70 . Each of the cylinders  68  contains a hydraulic piston rod  72 . In the longitudinal hydraulic gripper jack systems  64 , the piston rods  72  are connected to one of the transverse beams  56 . In die transverse hydraulic gripper jack systems  66 , the piston rods  72  are connected to the slid platform  54 . Each of the friction lock devices  70  is slidably mounted on the flange  58  of one of the beams  50 ,  56 . 
     To move the platform  54  longitudinally in a first or forward direction, the friction lock devices  70  of the two longitudinal gripper jack systems  64  are actuated to lock onto the flanges  58  of their respective longitudinal beams  50 . The cylinders  68  of the longitudinal gripper jack systems  64  are then actuated to extend their respective piston rods  72  to effect longitudinal translation of the platform  54  by an increment distance up to the full extendable length of the piston rods  72 . To move the platform  54  by the next distance increment, the friction lock devices  70  are actuated to release their locking engagement with the flange  58 , and the piston rods  72  are retracted, which pulls the friction lock devices  70  in the first or forward direction. The friction lock devices  70  are then locked onto the flange  58 , and the process is repeated until the desired longitudinal position is achieved. Longitudinal movement in a second, or reverse direction is achieved by operating the cylinders  68  and the friction lock devices  70  so as to push the friction lock devices  70  in the reverse direction. Movement of the platform  54  transversely along the transverse beams  56  is achieved by similarly operating the cylinders  68  and the friction lock devices  70  of the two transverse gripper jack systems  66 . Thus, by appropriately moving the platform  56  longitudinally and transversely over the well bay  28 , each of the production riser slots  46  can be accessed for deployment of a production riser  44  through it. 
     It will be appreciated that the above-described hydraulic jack skidding apparatus  42  is merely one particularly advantageous mechanism for shifting or translating the movable rig. Other suitable shifting or translating mechanisms will suggest themselves to those skilled in the pertinent arts. 
     The floating facility  10  described above is operable for performing field development drilling and well completion/production work in “parallel,” in a temporal, rather than physical, sense. That is, completion and production work can be performed from a single facility or structure at a first well that has previously been drilled by field development drilling from that structure while field development drilling is simultaneously being performed from that structure for a second well in the development field. 
     Specifically, as shown in  FIG. 11A , the facility  10  is positioned in a first development position for performing field development drilling at a first well location  80   a  through the drilling moon pool  26 . Field development drilling is performed at the first well location  80   a  through the drilling moon pool  26  with a first drill string  34   a  operated by the fixed drilling rig  30  through a drilling riser  36  (see  FIG. 2A ). As shown in  FIG. 11B , the fixed drilling rig  30  removes the first drill string  34   a  and a first drilling riser  36  from the first well location  80   a,  and the facility  10  is moved (by means such as the mooring lines  24 , or by a other means known in the art) to a second field development position for field development drilling at a second well location  80   b.  Then, as shown in  FIG. 11C , field development drilling is commenced at the second well location  80   b  through the drilling moon pool  26  with a second drill string  34   b  operated by the fixed drilling rig  30  through a drilling riser  36 . During the field development drilling at the second well location  80   b,  the position of the facility  10  may be adjusted, a, needed, to a first completion position in which the first well location  80   a  is accessible through the well bay  28 . Finally, as shown in  FIGS. 2 ,  3 , and  11 D, while field development drilling is still being performed at the second well location  80   b,  well completion/production work is commenced at the first well location  80   a  by the movable completion rig  40  which deploys a production riser  44  to the first well location  80   a  through the well bay  28 . 
     The above-listed sequence of steps is repeated as field development drilling is commenced at each subsequent well location, while completion/production work is performed at the most recently-drilled well location. The position of the movable completion rig  40  is shifted over the well-bay  28  to access each successive production riser slot  46  by means of the hydraulic jack skidding apparatus  42  described above. The use of top tensioned production risers  44  and the production tubing therein) facilitates the position shifting of the facility  10  needed for the movable completion rig  40  to access each well location after field development drilling has been finished at that location. 
     As will be appreciated, the apparatus and method disclosed above and illustrated in the drawings are exemplary embodiments only, and are not to be construed as exclusive of other embodiments and equivalents that may suggest themselves to those skilled in the pertinent arts. Indeed, such equivalents as may reasonably suggest themselves are deemed to be within the spirit and scope of the invention as defined in the claims that follow.