Abstract:
A method and a device for subsea wire line drilling permit the recovery of a full core barrel with a coiled tubing, without pulling up a drill string.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a method and a device for subsea wire line drilling. The invention is intended to be used with a subsea drilling system, such as that described in co-pending U.S. Patent Application No. (Attorney Docket No. F-8973), filed on the same date as the instant application and the disclosure of which is hereby incorporated into the instant application in its entirety. 
         [0003]    2. Description of Related Art 
         [0004]    Prior art wire line subsea drilling devices have not used coiled tubing and have required a drill string to be pulled up in order to recover cores. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    It is accordingly an object of the invention to provide a method and a device for subsea wire line drilling, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and in which wire line core retrieval is accomplished by using coiled tubing and cores can be recovered without pulling up the drill string. 
         [0006]    With the foregoing and other objects in view there is provided, in accordance with the invention, a method subsea for wire line drilling. The method comprises drilling a hole in a seafloor with a drill string, running coiled tubing down the drill string to a full core barrel having a core and latching the coiled tubing onto the full core barrel, recovering the full core barrel with the coiled tubing without pulling up the drill string, inserting the full core barrel into a tool carousel, retrieving an empty core barrel from the tool carousel, attaching the coiled tubing to the empty core barrel, lowering the empty core barrel into the drill string, unlatching the coiled tubing from the empty core barrel, and restarting drilling to recover another core. 
         [0007]    With the objects of the invention in view, there is concomitantly provided a 
         [0008]    device for subsea wire line drilling. The device comprises a drilling head to be disposed under water, and a wire line coiled tubing system associated with the drilling head underwater. The coiled tubing system includes a reel, coiled tubing wound on the reel, a drill string with a drill rod and a drill bit, and a core barrel to be latched to the coiled tubing for recovering cores without pulling up the drill string. 
         [0009]    Drilling processes with a drilling system that uses only a wire rope to retrieve and deploy core barrels have only been employed in the past for land drilling. The invention uses such a process for the first time for underwater drilling with a coiled tubing reel. 
         [0010]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0011]    Although the invention is illustrated and described herein as embodied in a method and a device for subsea wire line drilling, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0012]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0013]      FIG. 1  is a longitudinal-sectional view of a coiled subsea tubing system; 
           [0014]      FIG. 2  is a reduced, perspective view of the coiled subsea tubing system with the drilling head moveable thereon; 
           [0015]      FIG. 3  is an elevational view of the coiled subsea tubing system with a core barrel which has been retrieved; 
           [0016]      FIG. 4  is an elevational view of the coiled subsea tubing system illustrating a sequence of disconnecting a coiled tubing reel from the core barrel; 
           [0017]      FIG. 5  is an elevational view of the coiled subsea tubing system illustrating a process step in which an empty core barrel is to be dropped into a drill string; and 
           [0018]      FIG. 6  is an elevational view of the coiled subsea tubing system illustrating a sequence step in which the empty core barrel is dropped, latched and ready to drill into the drill string. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a longitudinal-sectional view of a coiled subsea tubing system  1 , which is used to retrieve wire line cores from a drilling operation. The coiled tubing system  1  also has the ability to send telemetry, indicated by reference numeral  4 , to the surface through a line  5  and subsea drilling system instrumentation  6 , using a subsea drilling system described in co-pending U.S. Patent Application No. (Attorney Docket No. F-8973), filed on the same date as the instant application. The coiled tubing system  1  also has a coiled tube reel  8  with a slip ring  9  connected to the line  5 , and a tube straightener  11 . The coiled tubing  12  is basically steel tubing wound on the reel  8 , which requires the straightener  11  before it is used. An injector  14  is used to push and pull the coiled tubing  12  down a hole. The coiled tubing reel  8 , the straightener  11  and the injector  14  are located on top of the subsea drilling system. 
         [0020]      FIG. 1  also shows a drilling head  2 , which is described in more detail in co-pending U.S. Patent Application No. (Attorney Docket No. F-8973), filed on the same date as the instant application. The drilling head  2  has a spindle assembly  3  as well as a non-illustrated hydraulic spindle drive motor and drive belt. The drilling head  2  can move up and down, as is indicated by a doubled-headed arrow  15 , and has a water inlet  16  leading into the drilling head. This structure according to the invention permits drilling without pulling the rods up continuously, as in diamond drilling. A drill rod  17 , which makes up a drill string  18 , has an open/close valve  20  at the top and a drill bit  21  at the bottom. A core barrel  22  is connected to the coiled tubing  12  at a latch  23 , below the seafloor  25 , and extends into the drill bit  21 , as in diamond drilling. The coiled tubing  12  is used to recover cores without pulling the drill string  18  back up. 
         [0021]      FIG. 2  is a perspective view of the coiled tubing system  1 , in which the instrumentation  6 , the slip ring  9 , the reel  8 , the coiled tubing  12 , the straightener  11 , the injector  14  and the drilling head  2  can be seen. The figure also shows hydraulic cylinders  27 ,  28  on which the drilling head  2  moves up and down in the direction of the arrow  15  and receives water at the inlet  16 . In addition, there are seen cylinder rods  29 ,  30  connected at the bottom to a machine frame.  FIG. 2  illustrates the coiled tubing system as drilling is started into the hole, and additional drill rods  17  are added. As each core barrel  22  is full, the core is recovered and pulled up by the coil tube reel. 
         [0022]      FIG. 3  shows a core barrel  22  with a core  32  which has just been pulled up by the coiled tubing reel  8  in the direction of an arrow  33  and retrieved from the drill rod  17  of the drill string  18 . It may also be seen that the drill with the bit  21  stays in the hole during drilling, but the core can be pulled from the drill string  18  and also replaced by using the coiled tubing system  1 . Upper and lower tool arms  35 ,  39  with respective grippers  35 ′,  39 ′ and a tool carousel  36 , as described in more detail in co-pending U.S. Patent Application No. (Attorney Docket No. F-8973), filed on the same date as the instant application, with drilling tools  37 ,  38  and core barrels  22 , can be seen on the left in  FIG. 3 . The upper tool arm  35 , which is a grabber tool arm, and the lower tool arm  39 , which is an alignment tool arm, are used to grab the core, align it and replace it, that is, to grab the core, disconnect it from the coiled tubing reel and place it back into the tool carousel  36 . 
         [0023]      FIG. 4  shows a step in a sequence of operation of the coiled tubing system  1 , in which the coiled tubing reel  8  is disconnected from the core barrel  22  and the tool arms  35 ,  39  are used to deploy and store the core  32  in the carousel  36 . The tool arms  35 ,  39  are also used to retrieve an empty core barrel  22 , which can be put down to the drill string  18  later on. 
         [0024]      FIG. 5  shows a process step in which the coiled tubing reel  8  is connected to an empty core barrel  22  that is ready to drop into the drill string  18  in the direction of an arrow  40 , at a connection location  42 . It may be seen that an outer barrel housing  44  of the core barrel  22 , the drill string  18  and the drill bit  21 , are deployed in this process step. 
         [0025]      FIG. 6  shows a step in the sequence of operation of the coiled tubing system  1 , in which the empty core barrel  22  has been dropped down, latched and is ready to drill into the drill string  18 . The figure shows the coiled tubing  12  disconnected from the core barrel  22  and ready to recover the core barrel when it becomes full again. This drilling process according to the invention does not require the drill rods  17  to be recovered every time there is a core  32  to be recovered and therefore is a faster drilling process than in the prior art. Processes have only been used in the past with a land drilling system that is merely a wire rope for retrieving and deploying core barrels. Such a process has never been used for underwater drilling with a coiled tubing reel. 
         [0026]    In summary, the sequence of operation of the coiled tubing system  1  is to drill a hole, run the coiled tubing  12  down to a core barrel  22  and latch on to it. Then the core barrel  22  is recovered using the coiled tubing reel  8  itself. Once the core barrel  22  is recovered, the arms  35 ,  39  are used to deploy the full core barrel  22  to the tool carousel  36  and again to retrieve an empty core barrel  22 . The next step is then to attach the coiled tubing  12  to the empty core barrel  22 , place it into the drill string  18  using the tool arms  35 ,  39 , then lower it down the drill string  18  until it latches into the outer barrel housing  44  of the core barrel  22 . Then the coiled tubing  12  is unlatched from the core barrel  22  and drilling can be started again to recover another core  32 .