Abstract:
A method for controlling the ascent and descent of a tubular member passing through a pipe or casing slip into a well bore. A float control member is affixed beneath the top surface of the pipe or casing slip. The control member is activated to control the raising or lowering of the tubular member. A piston within a cylinder housing is positioned below the top surface of the slip. As the tubular member is lowered, but before there is significant weight on the supporting structure, the piston is moved to its maximum height extension. Once the slips are set and the weight of the tubular member is applied to the slips, the piston begins to descend in the cylinder housing floating the final descent of the string. The string may be raised by activating a pump to force fluid within the housing chamber, raising the piston and thereby raising or lifting the string.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to well drilling technology. More particularly, the present invention relates to a method and apparatus for controlling the ascent and descent of vertical pipe or other tubular members passing through a pipe or casing slip into a well borehole.  
         [0002]     It is well known in the oil well drilling art that pipe or casing slip assemblies are utilized in oil field operations for drilling, setting casing, or placing or removing any tubular member from a well bore. An excellent explanation of the function and operation of drill pipe slip assemblies is provided in U.S. Pat. No. 6,471,439, which is incorporated herein by reference for all purposes.  
         [0003]     One of the most significant problems encountered in setting slips is maintaining control of the descent of the pipe into the slip and the slip into the slip bowl. The extensive lengths of piping in a drill string may result in considerable weight having to be controlled by the rig operator&#39;s braking procedures. Dropping the weight too quickly may result in damage to the pipe wall leading to fatigue of the pipe or breaking of the slip dies. If a pipe section fails the entire length of the drill string below the failure may be lost. Attempts to pull stuck drill strings from the well bore often puts site personnel at considerable safety risk. The draw works (block and tackle arrangement) may snap or the derrick rigging itself may collapse. These problems are associated with the pulling or supporting of the drill string from above the rig platform and, more particularly, having the pulling or supporting force coming from above the top surface of the slip. Casing jacks have been used in the past to pull old casing from the well bore. However, these are set up after the well is drilled. With the present invention the float system may be in place before the drilling starts.  
         [0004]     The present invention provides a number of embodiments which push or support the drill string from beneath rather than pulling from above. The same method and apparatus allows for the string to be cushioned, controlled, or dampened in its descent thereby reducing pipe or casing wall failures. Thus, the present invention further reduces the likelihood of broken slip teeth (dies) and crimping and fatiguing of the pipe wall which results in pipe failure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]      FIG. 1A  is a side elevation, cross-sectional view of the pipe floating system of the present invention in a first unloaded position. The lifting member is disposed within the slip bowl.  
         [0006]      FIG. 1B  is the system of  FIG. 1A  in a second loaded position.  
         [0007]      FIG. 2A  is a side elevation, cross-sectional view of an alternative embodiment of the pipe floating system of the present invention in a first unloaded position. The lifting member is disposed within the slip itself.  
         [0008]      FIG. 2B  is the embodiment of  FIG. 2A  in a second loaded position.  
         [0009]      FIG. 3  is a top view of the piston member of the embodiment of  FIG. 2 .  
         [0010]      FIG. 4  shows a perspective view of the slip wedge of the embodiment of  FIG. 2  with the associated hydraulics.  
         [0011]      FIG. 5  illustrates a perspective view of the piston of the floating pipe system with replaceable slip teeth inserted.  
         [0012]      FIG. 6  shows a slip spider mechanism on a lifting platform of the present invention.  
         [0013]      FIG. 6A  is a side elevation, cross-sectional view of the embodiment of  FIG. 6 .  
         [0014]      FIG. 7  illustrates the floating platform of the  FIG. 6  embodiment showing the hydraulic cylinders.  
         [0015]      FIG. 8  is a perspective view of yet another embodiment of the present invention in a rotary table floating frame. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]      FIGS. 1A and 1B  illustrate a side elevation, cross-sectional view of a pipe floating system  10  of the present invention.  FIG. 1A  shows the system in a first unloaded position.  FIG. 1B  illustrates a second loaded position. A section of drill string pipe  11  passes through a pipe or casing slip  12  into a well borehole. The construction of the conventional slip  12  is well known in the art. The slip teeth  13  engage the outer surface of the pipe or casing and are rotatably held within slip bowl bushings  14 . The ascent and descent of the pipe  11  may be controlled by the raising and lowering of the primary piston bowl assembly  16  into which the slips  12  and bushing  14  fit. It should be understood that the intent of the present invention system is to control the ascent and descent from beneath the top surface  18  of the slips.  
         [0017]     The piston bowl assembly  16  is provided with a circumferential piston head  20 , seals  22 , and a retainer ring  24 . An upper rotary table insert  26  supports the piston bowl assembly and may optimally be driven by a gear  28  and pinion  30  drive mechanism.  
         [0018]     Pinion  30  engages gear  28  in upper table insert  26 . Rotation of the pinion is translated into rotary motion of the insert and the piston bowl assembly  16  via meshing of splines  27  in the insert with complementary splines  17  in the bowl assembly.  
         [0019]     The upper insert  26  is attached at joint  32  to the lower table insert  34 . Seals  36  along the inner face of upper table insert  26  seal against the sliding face  35  of piston bowl assembly  16  as will be further understood below. Lower table insert  34  is provided with a cooperating circumferential piston shoulder  29  having seals  39 . Thus, a fluid chamber  42  is formed between the underside of the piston head  20  and the upper side of piston shoulder  29 . The chamber  42  is sealed by seal sets  22  and  39 . Oil is provided to chamber  42  by an oil pressure control system  40 . A pressure control valve V allows oil to flow between chamber  42  and reservoir R.  
         [0020]      FIG. 1A  illustrates the pipe float system  10  in a first unloaded position. Pipe  11  is suspended by overhead rigging not shown but well known in the art. The slips have been inserted into the slip bushings within the piston bowl. The chamber  42  is at its full volume and filled with oil (and an inert gas to provide cushioning as desired). As the weight of the drill string is allowed to bear upon the slips, the pipe&#39;s descent is controlled by the “cushion effect” or the “dampening effect” of the oil in the chamber. The pressure control system  40  allows oil to bleed past the control valve V and into the oil reservoir R.  
         [0021]     When the full weight of the drill string is loaded onto the pipe float system  10 , the piston bowl assembly  16  has moved to a second loaded position as shown in  FIG. 1B . It should be understood that an oil reservoir  41  may be incorporated into the lower table insert  34  as shown in broken lines in  FIG. 1B . Further, it is envisioned within the scope of the present inventive system that the oil pressure control system may be provided with pumps, valves, automated weight control system and piping capable of injecting oil into the chamber  42  as necessary to assist in the lifting of the slips, slip bushings, and the piston bowl assembly. Thus, with the present system both the descent and ascent of the drill string may be controlled from beneath the top surface of the slips.  
         [0022]     To ensure that the bowl assembly is not overly extended either in the load or unload position, retainer ring  24  is threadingly secured to the bottom of piston assembly bowl  16 .  
         [0023]     Turning to  FIGS. 2A and 2B , an alternative embodiment of the present invention is illustrated. In this embodiment the system  100  employs an ascent and descent control mechanism within the slip wedge itself. An L-shaped piston member  60  slides within a cylinder housing  72  within each wedge segment  70 . The piston  60  has a cylindrical head section  62 , a horizontal extension  64  and a vertical leg  66  ( FIG. 5 ). The leg has a notch  68  which accepts replaceable slip teeth segments  80 . Each piston  60  has various sets of ring seals. O-rings  77  are attached to the outer surface of the piston to seal against the cylinder wall  73 . A bypass ring  74  may be attached to the piston to further control the oil flow within the pressure chamber  76  as will be described below. A sealing ring  78  is affixed to the piston to seal oil within and to retain a compression spring  82  in the chamber  76 .  
         [0024]      FIG. 3  illustrates a top plan view of the piston  6  showing the head section  62 , the extension  64 , the leg  66 , and the slip teeth receiving notch  68 .  
         [0025]     The wedge segment  70  has a piston cylinder housing  72  for retaining the piston head section  62 , a hydraulic pressure vein  84  extending from the top surface  83  of the segment and exiting at a location  85  near the bottom of the cylinder housing below the piston head. As will be described further, oil in the chamber  76  may flow through vein  84  when the piston head  60  moves within the housing  72  to raise and lower the slip segments  80 . A piston leg guide  89  ( FIG. 4 ) extends along one edge of the segment  70  to guide and retain the piston leg with the slip teeth sections. A slip seat  87  is disposed at the bottom of guide  89  to prevent the leg  66  and slip segments  80  from excessive downward travel.  FIG. 4  shows a wedge segment and an associated pressure control system  90 . System  90  has an oil reservoir R, a pressure control valve V, piping  91 , and pump P as needed.  
         [0026]      FIG. 2A  depicts the piston  60  in a first unloaded position. Only one slip segment is illustrated for clarity. The slip segments  80  and the leg  66  are holding pipe  11  as it is being lowered. The weight of the pipe string is transferred to the piston head  62  as the slip teeth engage the pipe. The head  62  compresses the oil in chamber  76  and this increased fluid pressure is translated to the pressure control system  90 . Thus, the downward movement of the drill string is cushioned or dampened by the system  100 .  
         [0027]     To provide further controls of the movement (upward and downward) of the pipe, a flow pressure ring  74  having a beveled edge or drilled through holes may be affixed to the piston head  62 . Further control may be provided by a compression spring  82  retained in the chamber  76  within the housing  72  beneath a piston ring  78 . Any number of further controls may be provided.  
         [0028]      FIG. 2B  shows the piston  60  in a second loaded position having taken the weight of the drill string and stopping at seat  87 . Again, it is within the scope of the present invention that the oil pressure control system may inject oil into the chamber  76  as necessary to assist in the ascent or lifting of the slips and the drill string. While the present discussion has disclosed the use of an oil pressure system, it is within the scope of the invention that any pressure regulation system such as springs, inert gas, or other hydraulic fluids may be used.  
         [0029]      FIGS. 6, 6A , and  7  illustrate yet another embodiment  150  of the present invention. A spider system  91  for setting slips on production tubing and casing is well known in oil field art. A hydraulic or electric motor  95  activates an extension and retraction unit  97  which controls the clamping action of the slip wedges  96  about the pipe  11 . In the present inventive embodiment, an ascent/descent control platform  90  supports the spider system  91  on the well head.  
         [0030]      FIG. 7  shows a simple U-shaped platform base  97  adapted to accommodate a plurality of lifting jacks  102  within housings  92 . The jacks  102  are connected by common control conduit  93  linking the jacks so that they may be raised and lowered at the same time. From the foregoing description of the other embodiments it should be understood that the final descent of the tubing or casing string may be controlled by controlling the upward and downward movement of the jack  102 . A suitable pressure control system is connected to the control conduit through piping  98  extending from the control conduit to the pressure regulation system.  
         [0031]     Another embodiment of the present invention is illustrated in  FIG. 8 . In system  200 , a rotary table (not shown), well known in the art, is supported by a frame  106 . Beneath frame  106  a plurality of hydraulic jacks  110  are disposed to support the ascent and descent of the frame (and the rotary table) as the drill and/or casing string is held, raised or lowered into the associated slips as discussed above.  
         [0032]     In the inventive method, the slips are set and the elevators are unlatched. A joint of pipe is picked up by the operators and attached to the existing drill string. Then the entire drill or casing string is lifted with the draw works. The slips are pulled. While the entire string is being lowered and no drill string weight is on the table, electric (or air, or hydraulic) pump  112  moves the jack pistons  114  to their maximum height or extension, thereby raising the frame  110  and the rotary table (not shown).  
         [0033]     When the drill string is lowered by the operator via the draw works to the desired position to set the slips, the slips are set. The electric control throttle valve  118  is set to take a certain minimum weight (for example 50 K lbs). A million pound drill string, for example, may activate the throttle valve  118  to open as the frame is urged downwardly by the weight of the drill string (shown by arrows with broken lines) pushing oil from the jack reservoirs JR through the connective piping past the throttle valve  118  through the oil return line  119  and into the main oil reservoir R. Thus, the drill string is “floated” downwardly in its descent. The procedure is repeated with each new pipe joint.  
         [0034]     An automatic increase in the throttle valve  118  threshold may be provided as the drill string weight increases as more pipe is connected to the string. Oil flow may be metered by observing and monitoring oil pressure through sensor/recorder  120  and manually or automatically adjusting the throttle valve  118  to compensate for the increased or decreased weight of the string. The closer the pistons  114  get to the bottom of the stroke, the slower the float. This may be set by the throttle valve settings. A high pressure check valve  122  is provided for system safety to allow oil bleed back into the main reservoir as necessary.  
         [0035]     As with all embodiments of the present invention, system  200  is provided with a pump  112  and piping that may be used to lift the frame  106  to jack the string out of the borehole by lifting the slips attached to the outer surface of the pipe casing. This is a safe way to push a stuck string upwardly without using forces above the rig floor to pull the string upwardly.  
         [0036]     Although the invention has been described with reference to a specific embodiment, this description is not meant to be construed in a limiting sense. On the contrary, various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the true spirit and scope of the invention.