Patent Publication Number: US-9404329-B2

Title: Downhole tool for debris removal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to a downhole tool for debris removal. 
     2. Description of the Related Art 
     Wellbores are formed one section at a time with each section typically lined with a string of tubulars (casing or liner) which are cemented in place before a subsequent, smaller diameter length of wellbore is drilled. The cementing process consists of pumping a curable material down the wellbore and circulating it back up an annular area formed between the new tubular string and the earthen bore around it. When lower sections of tubulars are cemented, there is typically cement residue left at an upper end of the string where it can cure and interfere with later operations. Debris removal tools typically have extendable arms or blades and are run into the wellbore on a work string. Once remotely actuated, the tools are rotated and/or reciprocated in order to remove debris from an upper end of the newly cemented string and from an interior of the lager diameter tubular thereabove. Prior art debris removal tools are unreliable. In one instance, friction between the blades and the debris or the wellbore walls, especially in non-vertical wellbores, can cause at least one blade to prematurely retract while in use. In most cases, an operator at the surface of the well is unaware of the malfunction. In other cases, the tools are removed in an extended position, risking damage to a tubular string therearound as the work string and tool are rotated. 
     What is needed is a debris removal tool for use in a wellbore that is more reliable. 
     SUMMARY OF THE INVENTION 
     The present invention generally relates to a downhole tool for use in a wellbore having a tool body with a blade assembly slidably mounted thereon and movable between a retracted and an outwardly extended position. The blade assembly is biased towards the retracted position and movable with an actuating force to the extended position. The tool includes an indexer constructed and arranged to facilitate the movement of the blade assembly. In one embodiment, the blade assembly is unitary and in another embodiment the tool includes a signaling arrangement to notify an operator when the tool has been shifted between positions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1A  is a partial section view of a lower end of a tool in a run-in position and  FIG. 1B , C are views of an upper portion thereof. 
         FIG. 2  A is a partial section view of a lower end of the tool of  FIG. 1  in an actuation position and  FIG. 2  B, C are views of an upper portion thereof. 
         FIG. 3  A is a partial section view of a lower end of the tool in an operational position and  FIG. 3  B, C are views of an upper portion thereof. 
         FIG. 4  is a perspective view of an indexer. 
         FIG. 5  is a partial section view of the tool in a wellbore. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to a debris removal tool for use in a wellbore. 
     As used herein, the terms “down,” “up,” “downward,” “upward,” “lower,” “upper” and other directional references are relative and are used for reference only. Also, the terms “blade assembly” and “blades” are used interchangeably to simplify explanations. U.S. Pat. No. 7,143,847 and Patent Application Nos. 2009/0025927 and 2009/0218092 disclose downhole tools for debris removal and those are incorporated herein in their entirety. 
       FIG. 1A  is a section view of a lower portion of a tool  100  in a run-in position. The tool  100  includes a blade assembly  105  typically including three blades  110 , radially spaced around a body  115 . The blade assembly  105  is movable relative to the body  115  of the tool and also movable relative to an outer housing  120 . In the embodiment shown, the blade assembly  105  is unitary, whereby all blades  110  move together between the various positions of the tool. The blade assembly  105  is shown in its run-in (retracted) position and is retained in that position by a spring  125  (visible in  FIG. 2B , C) that biases the blade assembly downward relative to the body  115  and outer housing  120  and also by a shearable pin  130  that prevents the tool  100  from becoming actuated during run-in. The unitary nature of the blade assembly permits a single pin to be used to hold the assembly in place during run-in. Because the pin can be more robust that individual pins for each blade, there is less chance of the tool shifting during run-in. In the run-in position shown in  FIG. 2A , the blades  110  are held adjacent the body  115  of the tool due to profiles  140  formed in the blade and pins  145  associated with the body. Each blade  110  is individually biased towards an outwardly extended position by springs  135  and when the tool is shifted, the pins  145  are moved to a different location in the profiles  140  permitting the springs to move the blades outwardly. Upward movement of the blade assembly to the outwardly extended position is limited by the length of a gap  152  that is formed between a leg of an L-shaped member  153  and a lower end of the housing  120 . 
     The tool  100  is shifted to its outwardly extended position (and back to its run-in position) by the generation of an actuating force between a lower end of the blade assembly  105  and a stationary object in the wellbore, like an upper end of a tubular or polished bore receptacle ( FIG. 2A ). The tool is constructed and arranged whereby an outer diameter of the blade assembly  105  is greater than the inner diameter of the tubular while the outer diameter of the tool body  115  is smaller than the inner diameter of the tubular. In this manner, the body  115  of the tool can extend into an inner diameter of the stationary tubular while the blade assembly  105  is retained at an upper end of the tubular and can be moved towards its outwardly extended position. As the tool  100  is actuated a first time, the shear pin  130  is fractured, permitting the blade assembly  105  to move against the biasing force of the spring  125 . 
     The tool is intended to be shifted between positions by the actuating force described above and the position of the blades and blade assembly  105  is determined and managed by an indexer  150  that is illustrated in  FIG. 1B , C. Like the blade assembly, the indexer  150  is arranged around the body  115  of the tool  100  and moves with the blade assembly independent of the body and outer housing  120 . The indexer  150  includes a continuous groove  155  formed around its perimeter and operates with a set of inwardly facing balls  160  that are radially disposed around an interior of the housing  120  and retained in the grove  155 . In the run-in position shown in  FIG. 1B , the balls are retained at a location “1” in the groove. 
     In addition to the indexer  150 , the tool illustrated includes a signaling arrangement to notify an operator at the surface of the well of the position of the tool. Still referring to  FIG. 1B , C, the signaling arrangement in the embodiment shown includes windows  165  formed around the indexer  150 , ports  170  formed in the body  115  and corresponding ports  175  formed in the outer housing  120  of the tool. The ports  170 ,  175  and windows  165 , when aligned, permit fluid communication between a central bore  180  of the tool and an annulus between the tool and casing therearound (not shown). For example, the ports  170 ,  175  and windows  165  are constructed and arranged to align when the tool is moved from the run-in position to the actuation or operational positions shown in  FIGS. 2A-C ,  3 A-C. In this manner, a shift of the tool  100  from the run-in position will result in a change in pressure, noticeable at the surface of the well, as the windows and ports align and fluid from the bore of the body is permitted to escape to the annulus. The ports can be sized depending on the flow rate of fluid through a work string and the desired pressure drop. In one example, fluid is pumped at 600 gallons per minute (GPM) and a drill bit at the lower end of the string creates a fluid pressure of 1000 psi in the string. The ports can be sized so that when they are aligned with the windows of the indexer, a pressure drop of 20% takes place, resulting in a drop of pressure at the surface from 1000 to 800 psi. 
       FIG. 2A  is a partial section view of a lower end of the tool of  FIG. 1  in an actuation position. The tool  100  is shown in an outer tubular  200  and in contact at a lower end with a smaller diameter tubular  300 . An annular space  301  between the tubulars represents the annulus that is typically filled with cement. Debris to be cleaned by the tool typically comprises surplus cement that flows upwards from this annulus and dries on the upper surface of tubular  300  or the inner walls of larger diameter tubular  200 . As is visible, the blade assembly  105  has been moved upwards relative to the body  115  and outer housing  120  by an actuation force developed between a lower end of the blades  110  and an upper surface of the tubular  300 . The shearable pin  130  has been broken and the blade assembly  105  has compressed the spring  125  ( FIG. 2B ) and moved to a position in which the gap  152  previously formed between the leg of L-shaped member  153  and a lower end of the housing  120 , no longer exists. Similarly, the pins  145  have moved to a lower position in the blade profiles  140 . In addition, the blades  110  have moved to their outwardly extended position with the springs  135  biasing the blades  110  out and away from the body. While the blades are shown outwardly extended in  FIG. 2A , it will be noted that the actuation force might create adequate friction between the blades  110  and tubular  300  that the blades remain in their retracted position while the actuation force is engaged. 
       FIG. 2B , C are views of the upper portion of the tool  100  in the actuation position. Comparing  FIG. 2B , C to  FIG. 1B , C, the location of the inwardly facing balls  160  has changed relative to the continuous groove  155  of the indexer  150 . Specifically, the balls  160  have moved from location “1” to location “2” as the indexer  150  has moved upwards relative to the body  115 . The balls will remain in this position as long as the actuation force exists between the blades  110  and the tubular  300 . Also visible in  FIG. 2B , C is an alignment between the windows  165  of the indexer, the ports  170  of the body, and ports  175  of the outer housing (not visible in  FIG. 2B ) illustrating that fluid communication has been established between the bore  180  of the tool and an annular area between the tool  100  and the larger diameter outer tubular  200  with a resulting pressure drop that will notify the operator that the tool  100  is no longer in its run-in position. The alignment of the windows and ports is due to axial movement of the body and rotational movement of the indexer. 
       FIG. 3A  is a section view of the tool  100  in its operating position. The blade assembly  105  is at a location along the body  115  between the run-in and actuation positions with the blades  110  outwardly extended and a partial gap  152  formed between the L-shaped member  153  and the outer housing  120 .  FIG. 3B  is a partial section view of the upper portion of the tool  100  showing the indexer  150  with its continuous groove  155  and its relationship with the inwardly facing balls  160 . In the operating position, the balls are located at location “3” on the indexer. In this position, the blade assembly  105  is held in place relative to the body  115  and outer housing  120  solely by the balls and the groove. As with the actuation position, in the operating position the windows of the indexer are aligned with the ports of the body and ports of the outer housing ( FIG. 3C ) producing a noticeable pressure drop. 
     One purpose of the indexer, with its inwardly facing balls and continuous groove is to permit the tool to be repeatably shifted between the run-in and operating positions. For example, from the run-in position (indexer location “1”), the tool is “set down” on a stationary object in order to generate an actuating force (indexer location “2”). Thereafter, as the tool is lifted off the tubular and the actuating force is relived, the tool moves to its operating position (indexer location “3”). If, in the course of using the tool in its operating position, an actuating force is inadvertently applied (moving balls to location 4) due to friction between the blade assembly and the side of the wellbore, for instance the indexer will move to the run-in position (location 5) and the operator will be notified due to a pressure increase as the window and ports are taken out of alignment. However, the continuous nature of the groove permits the tool to easily be reactivated by setting down weight and moving the balls from location 5 to the next set of locations that correspond to locations 2, 3, and 4. In this manner, the tool can be repeatedly shifted between run-in and operating positions. 
     The embodiment discussed contemplates an indexer  150  with groove positions that shift the tool between the run-in and operation position with a single actuation force required between each movement. However, the indexer could be provided with a continuous groove that requires two separate actuating forces to return the tool to the run-in position.  FIG. 4  is a perspective view of an indexer  150  with such a continuous groove  155  and the redundant operational position is shown by location 5 which is reached prior to a run-in position, shown as location 7. This embodiment ensures the tool will remain in an operating position even if an actuating force is inadvertently applied. 
       FIG. 5  is a view of the tool  100  on a work string  101  in a wellbore. A larger diameter tubular (casing)  200  surrounds the tool  100  and below is an upper end of the smaller diameter tubular string  300 . The tool is in the run-in position with the blades  110  in contact the lower casing just prior to “set down” and development of an actuation force. In  FIG. 5 , a packer or hanger is shown in the gap  301  between the two tubulars. The hanger permits the smaller diameter tubular string to be “hung” off the larger one while the smaller string is cemented in place. 
     As the forgoing description and Figures illustrate, the tool  100  is run-in on a tubular string in a run-in position. When the tool reaches a junction between a larger diameter tubular string and a smaller diameter string therebelow, the tool is “set down” on the lower tubular to develop an actuation force. In the actuation position, the blades  110  may or may not be extended but in either case, a top surface of the lower tubular can be cleaned as the tool is rotated while in contact with the surface. Thereafter, the weight is removed and the tool moves to an operating position wherein the blades are extended as shown in  FIGS. 2A-C . The tool can be rotated and reciprocated in the wellbore to remove debris while fluid is circulated to flush the debris to the surface with return fluid. To move the tool back to a run-in position, an actuation fore is again applied and then removed. Each time the tool moves from the run-in position, an accompanying pressure drop provides a signal to an operator. In one embodiment, debris can include debris created when the outer tubular is perforated and the blades can be equipped with abrasive and/or hardened material like tungsten carbide for that purpose. 
     In one embodiment, the tool  100  as it appears in  FIG. 5  can be installed in a work string with any number of other tools and various downhole operations are performed in a single “run”. For example, a single work string might include a bit at a lower end for drilling out a cement plug at the lower end of the newly cemented tubular string. By spacing the bit and the debris cleaning tool, the tool can be set down on the casing top and shifted to the operational position just after the plug is drilled out. In addition, metallic debris loosened by the tool can be collected with string magnets. Once the debris cleaning operation is complete, fluid may be circulated to flush the wellbore of any drilling mud and replace it with water. In the same run, using additional equipment in the work string, the well can be subjected to a negative pressure test. Thereafter, the debris removal tool can be returned to its run in position and tripped out of the well. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.