Abstract:
A string is equipped with a braking device to regulate its speed into the wellbore through an existing tubular. When the targeted amount of overlap with an existing tubular is accomplished the two tubulars are then joined together. The braking system can take many forms such as externally mounted mechanisms that are speed responsive to vary the braking force. The inside of the tubular can have trapped gas to provide buoyancy and reduce the dropping speed. The braking can be accomplished hydraulically through regulated flow through the tubular or by a combination of a hydraulic and mechanical device. The momentum of the dropped string can also be controlled with a swage device that at the appropriate location lands on a taper and wedges or fuses itself to the surrounding tubular to gain support from the surrounding tubular.

Description:
FIELD OF THE INVENTION 
       [0001]    The field of the invention is running tubular string into a wellbore and more particularly a method to rapidly deploy a string without a running string by dropping the string and securing the dropped string to an existing string in the wellbore. 
       BACKGROUND OF THE INVENTION 
       [0002]      FIGS. 1-3  illustrate the typical way strings are run into a wellbore and secured to each other.  FIG. 1  illustrates an upper wellbore  10  that has a tubular string such as casing  12  that is sealed in the wellbore with cement  14 . A hanger/seal is illustrated generically as  16  since there may be situations with higher strings in the wellbore  10  that are above casing  12  or the casing  12  may be supported from a wellhead that is not shown. A subsequent tubular string  18  is assembled at the well surface and then further advanced into the lower wellbore  20  such that the upper end  22  overlaps with the lower end  24  of the casing  12 . A running string  26  is releasably secured to the string  18  and the release occurs after a hanger/seal  28  is deployed to secure the string  18  to the casing  12 . The running string is then pulled from the upper wellbore  10  as shown in  FIG. 3 . 
         [0003]    The process described above requires time to assemble the string  26  to the length that string  18  will overlap at its upper end  22  with the lower end  24  of casing  12 . Having secured the string  18  to the casing  12  the running sting then has to be raised and disassembled and racked near the rig at the surface. The assembly and disassembly time for the running string is the time that is desired to be saved with the present invention. 
         [0004]    The method entails dropping a string into a wellbore through an existing string and controlling its speed in a variety of ways. Upon reaching the desired location the strings are secured to each other in a variety of ways for conducting further downhole completion or production operations. The time saved is the time normally used to assemble and pull the running string. Typically the weight of the string is used to advance it and a variety of speed control features can be used to regulate the rate of advance to the end destination which can be the hole bottom or at a desired level of overlap with the existing tubular to which the dropped string will be attached. A variety of attachment techniques are described. 
         [0005]    In the past, braking systems have been designed to decelerate dropped objects so that they don&#39;t damage downhole components by striking them at high speeds. These devices are typically intended to make the falling object stop either as fast as possible or if there is interaction with a well feature then the intent is to stop the object as that feature is encountered before impact with a downhole tool such as a closed ball valve for example. Other designs expect impact and provide crushable leading ends to absorb the kinetic energy during rapid deceleration to minimize damage to downhole components. Some examples of the above are USP and Published Applications U.S. Pat. No. 7,779,907; 2010/0126732; U.S. Pat. Nos. 7,178,600; 7,328,748; 5,366,013; 6,109,355; 6,454,012; 7,451,809; 4,693,317; 5,083,623; 5,183,113; 5,875,875; 6,708,761; 6,817,598; 4,223,746; 4,658,902; 4,932,471; 4,679,669; 5,549,156; 5,590,714 and 7,296,638. 
         [0006]    The present invention seeks to rapidly deploy a string as well as fixate the rapidly delivered string in a manner that will properly position the string to be secured and minimize pressure effects on the formation that can ensue from excessive string travel speed. Those skilled in the art will more readily appreciate the details of the preferred mode of the invention from the description below and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims. 
       SUMMARY OF THE INVENTION 
       [0007]    A string is equipped with a braking device to regulate its speed into the wellbore through an existing tubular. When the targeted amount of overlap with an existing tubular is accomplished the two tubulars are then joined together. The braking system can take many forms such as externally mounted mechanisms that are speed responsive to vary the braking force. The inside of the tubular can have trapped gas to provide buoyancy and reduce the dropping speed. The braking can be accomplished hydraulically through regulated flow through the tubular or by a combination of a hydraulic and mechanical device. The momentum of the dropped string can also be controlled with a swage device that at the appropriate location lands on a taper and wedges or fuses itself to the surrounding tubular to gain support from the surrounding tubular. A hanger/packer device can be associated with the falling string to set against the surrounding tubular when the desired depth is reached. Actuation can be with a variety of signals or timers, for example. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  shows cemented casing in a wellbore as is done in a manner known in the art; 
           [0009]      FIG. 2  is the view of  FIG. 1  showing another string run to the lower end of the casing and in position for being joined to the casing; 
           [0010]      FIG. 3  is the view of  FIG. 2  showing the second string attached to the casing and the running string pulled from the wellbore; 
           [0011]      FIG. 4  shows a tubular string dropped through an existing string using the method of the present invention; 
           [0012]      FIG. 5  shows a part of the falling string illustrating a braking assembly and a hanger/packer assembly that can be used to secure to an existing well tubular; 
           [0013]      FIG. 6  shows an alternative design of a braking assembly than shown in  FIG. 5  using a combination of mechanical and hydraulic operation; 
           [0014]      FIG. 7  shows an alternative braking device that relies on flow through the falling tubular to actuate the braking force; 
           [0015]      FIG. 8  shows a braking device that is a swage that elastically expands the exiting tubular wall as a braking device for the falling string; and 
           [0016]      FIG. 9  shows a braking device that is a multi-part construction and responds to speed to apply more braking force in combination with a an annular barrier; 
           [0017]      FIG. 10  is an alternative braking device using a wheel with a braking device; 
           [0018]      FIG. 11  is the view along lines  11 - 11  of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0019]      FIG. 4  schematically illustrates the concept of the method of the present invention. A string  30  is dropped through an existing tubular  32  that is already in wellbore  34 . Schematically illustrated as  36  is a braking device and a device that can secure the tubular  30  to the tubular  32 . The braking and supports devices can be discrete or they can be integrated. Also shown schematically at a lower end  38  is a nose portion  40  that can facilitate travel of the string past joints or other wall irregularities in the existing string  32  or at transitions between strings if the dropping string  30  has to pass through more than a single size of tubular string that exists in the wellbore. Optionally, the nose  40  can have a crumple feature to absorb shocks such as when the falling string is designed to optionally land on the well bottom  42  before being secured to the tubular  32 . 
         [0020]      FIG. 5  shows one type of brake mechanism  44  on the outside wall  46  of the string  30  that is dropping. A wedge  48  is biased in a downhole direction by a spring  50  that bears on a stop  52 . One or more flexible drag devices such as bow springs  54  are designed to extend into contact with the interior surface  56  of the existing string  32 . The friction force that is generated from such sliding movement of the springs  54  overcomes the force of the spring or springs  50  so that the wedge  48  rides up under ramped surface  58  of brake sleeve or segment  60  that is secured to the dropping string  30  at ring  62 . Sleeve or segment  60  flexes radially to contact surface  56  to slow the advance of the string  30 . The top of the string  30  has a plug  64  and at the lower end there is another plug  66  to define a closed space  68  that holds air or another gas preferably at atmospheric pressure. The filling of the space  68  with gas adds to the buoyancy of the assembly and acts as a brake force against the weight of the string  30  falling under a gravitational force of its own weight. Once at the desired position the plugs  64  and  66  can be removed such as by exposure over time to well temperatures, or the addition of a material to the well to dissolve or otherwise remove these plugs or the use of anticipated well fluid properties with time exposure to get the result of plug removal so that further completion operations can take place through the string  30  or subsequent production or injection operations, for example. 
         [0021]    As previously stated the string  30  can fall until the nose  40 , if used, or the lower end  38  land on the well bottom  42  so that the hanger/packer assembly  70  is at the right location near the lower end of the existing tubular  32 . Alternatively, the inner wall  56  can have a profile  70  that the brake assembly  44  can engage with sleeve or segment  60 . 
         [0022]    The hanger/packer assembly  70  is illustrated schematically and is actuated in several ways as schematically illustrated by arrow  72 . One or more slips  74  and a seal assembly  76  can be actuated in a variety of known ways such as wellbore pressure, hydrostatic pressure, an adjacent processor that determines that it is time to actuate based on depth, acoustic signals, radio frequency signals, pressure release from a chamber or the like. The hanger packer assembly  70  and its mode of actuation is known in the art and incorporated into the method of the present invention to accomplish the securing function of joining the dropped tubular  30  to the surrounding tubular  32 . 
         [0023]      FIG. 6  illustrates and alternative braking assembly  78 . Here a dragging device such as a bow spring or springs  80  move a piston  82  to reduce the volume of chamber  84  and force out hydraulic fluid through line  86  to radially extend pistons  88  and in turn move out the brake shoe  90  against the inner wall  56  of the existing tubular  32 . 
         [0024]      FIG. 7  illustrates a braking device  92  for the dropped string  30  that uses a top sleeve  94  that has a plug  96  with an aperture  98 . As the string  30  falls flow represented by arrow  100  goes through aperture  98  which puts an uphole force on the sleeve  94  that in turn drives ramp  102  along tapered surface  104  so that the brake shoe  106  is forcibly driven into wall  56  to slow the velocity of the dropping string  30 . 
         [0025]      FIG. 8  is another embodiment that is schematically represented as a swage member  108  that preferably elastically expands the inner wall  56  of the existing tubular  32  to get the desired braking force as the string  30  drops at a controlled rate. The inner wall  56  can have a profile  110  that is strong enough to stop the moving string when the swage member  108  comes into contact with it. Doing it this way will then use the hanger/seal assembly  78  as one way to secure the strings  30  and  32 . Alternatively, the swage  108  can have a lock device to latch and seal in the profile  110  upon landing in it. In yet another alternative the interaction of the swage  108  as it enters the profile  110  can be used to fuse the two together from the heat generated from the momentum of the string  30  as it rapidly decelerates in the vicinity of the profile  110 . Materials conducive to the fusion of surfaces can be used in the profile  110  and/or the outer face of the swage  108 . 
         [0026]      FIG. 9  illustrates the string  30  with a nose  40  connected to a ramp  112  that is biased downhole by spring  114  bearing on ring  116 . Ramp  112  has a flexible annular barrier  118  that is designed to drag on wall  56  and has a port or ports  120  at are provided to attain the desired speed of descent. Alternatively the flow can go through the nose  40  if an opening is provided in it so that flow can pass through the string  18 . Well fluid can also flex the barrier  118  so that flow can pass around the outside of the barrier  118  when it is flexed away from the wall  56 . The uphole force on the ramp assembly  112  is related to the characteristics of the barrier  118  and the frictional force it generates. The higher the uphole force that is generated from the dropping of the string  30  the more braking force is applied by the shoe  122  against the surface  56  of the existing tubular  32 . 
         [0027]    Referring to  FIGS. 10 and 11  a single assembly of four is shown in detail. A housing  136  supports a link  134  that is biased away from the string by a biasing member  132 . At the other end of link  134  is a wheel  128  that rides on the inside wall of the string. The wheel  128  has a gear or pulley  130  on an axis thereof for connection to a drive system  126  that can be a belt or a chain. The drive system  126  links the rotation of the wheel  128  to a rotor  122 . Rotation of rotor  122  is resisted by viscous drag between the rotor  122  and surrounding fluid. The surrounding fluid may be wellbore fluid or fluid enclosed in housing  124 . The viscous drag thus creates a positive feedback system whereby the velocity of the string is limited by a ratio of drag coefficients to buoyant weight of the string. Those skilled in the art will appreciate that there are other variations to the above described method. Velocity control can also be with a processor and speed sensor for the falling string that can employ on board power such as a battery to actuate the braking device and to hold a predetermined speed of descent. The braking device can be configured to respond to velocity increases with increasing braking force. The buoyancy feature can be obtained with only a top plug  64  while omitting the bottom plug  66  leaving chamber  68  with an open bottom that could compress the gas in the chamber and somewhat reduce the buoyant force due to gas compression in chamber  68 . The braking is designed for speed control to avoid raising pressure unduly on the formation as the string descends as is the goal when lowering a string on a running string. Stopping the string is done using the hole bottom or features in the existing sting through which the dropped string is moving. Once properly positioned, the hanger/packer can be deployed in a variety of ways. Alternatively, the two strings can be fused together as the dropped string reaches a stationary position using the heat from elastic deformation caused by the swage on the dropped string regulating its speed with the resistance of the elastic deformation of the swage associated with the dropped string. The leading end of the dropped string can have a tapered nose to ease passage of the string over irregularities in one or more existing strings or at size transitions between or among strings. The nose can have a crumple feature that can collapse if the string is allowed to drop to the hole bottom. 
         [0028]    The above description is illustrative of the preferred embodiment and many modifications may be made by those skilled in the art without departing from the invention whose scope is to be determined from the literal and equivalent scope of the claims below.