Abstract:
An embodiment of a method for forming slots in a wellbore casing, comprises providing at least one cutting tool, the cutting tool comprising at least a jetting assembly and an indexing assembly, disposing the cutting tool into the wellbore via a conveyance, stopping movement along the wellbore axis of the cutting tool, and forming slots in the casing by actuating the indexing assembly such that the jetting assembly forms slots in a predetermined pattern in the casing. In an embodiment, the method further comprises flowing a material into the slots formed in the casing to seal the wellbore.

Description:
BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art 
     The present disclosure is related in general to wellsite and wellbore equipment such as oilfield surface equipment, downhole wellbore equipment and methods, and the like. 
     On occasion, a wellbore having casing or casings installed therein may need to be cemented, i.e., have cement flow into the area between the casing and the formation, for example, in order to plug and/or abandon a well. Cementing the area between the casing and formation should assist in plugging, killing, and/or abandoning the well. 
     In order to accomplish the cementing of the wellbore, it may be desirable to cut or form slots in the casing at a desired location while maintaining the structural integrity of the casing. After the slots are cut or formed in the casing, cement may be flowed into the slots and into the area between the casing and the formation to assist in the plugging and/or abandoning of the well. 
     It remains desirable to provide improvements in the efficiency, flexibility, reliability, and maintainability of wellsite surface and downhole equipment. 
     SUMMARY 
     An embodiment of a method for forming slots in a wellbore casing, comprises providing at least one cutting tool, the cutting tool comprising at least a jetting assembly and an indexing assembly, disposing the cutting tool into the wellbore via a conveyance, stopping movement along the wellbore axis of the cutting tool, and forming slots in the casing by actuating the indexing assembly such that the jetting assembly forms slots in a predetermined pattern in the casing. In an embodiment, the method further comprises flowing a material into the slots formed in the casing to seal the wellbore. The material may comprise a cement material. The method may further comprise killing the wellbore by flowing the material into the casing and at least an annulus disposed around the casing. In an embodiment, stopping movement comprises forming a solid base in the wellbore prior to disposing the jetting assembly into the wellbore and engaging the indexing assembly with the solid base. The solid base may comprise at least one of a bridge plug, a sand plug, a cement plug, and combinations thereof. In an embodiment, forming slots comprises forming slots in the casing without completely severing the casing into distinct portions thereof. 
     In an embodiment, forming slots comprises causing rotation of the jetting tool via reciprocating actuation of the indexing assembly, providing may comprise providing an indexing assembly comprising an outer shell and an inner mandrel disposed interior of the outer shell, the outer shell having a pin that engages with a helical groove formed in the outer surface of the mandrel, the indexing assembly further comprising a spring-biased bushing in the outer shell for urging the shell in an upward position, and causing rotation may comprise applying an axial force to the conveyance and compressing the spring and thereby allowing the outer shell to move downwardly while the mandrel remains substantially stationary, the pin engaging with the groove and rotating the jetting assembly and indexing assembly during movement thereof. In an embodiment, providing comprises providing surface equipment having a supply of jetting fluid in fluid communication with the cutting tool. In an embodiment, disposing comprises disposing the cutting tool into the wellbore via coiled tubing. In an embodiment, forming comprises forming slots in the casing that are substantially perpendicular to the wellbore axis of the cutting tool. In an embodiment, forming comprises forming slots in multiple concentric casings. In an embodiment, providing comprises providing a cutting tool with a jetting assemblies assembly comprising first and second nozzles and wherein forming comprises forming slots with the first nozzles, deactivating the first nozzles, activating the second nozzles and forming slots with the second nozzles. 
     An embodiment of a system for forming slots in a cased wellbore, comprises at least one cutting tool, the cutting tool comprising at least a jetting assembly and an indexing assembly, a conveyance for disposing the cutting tool in the wellbore, and surface equipment in fluid communication with the at least one cutting tool via the conveyance, the cutting tool configured to form a plurality of distinct slots in a predetermined pattern in the casing of the wellbore when actuated. In an embodiment, the conveyance comprises coiled tubing. In an embodiment, the surface equipment comprises jetting fluid equipment. 
     In an embodiment, the indexing assembly comprises an outer shell and an inner mandrel disposed interior of the outer shell, the outer shell having a pin that engages with a helical groove formed in the outer surface of the mandrel, the indexing assembly further comprising a spring-biased bushing in the outer shell for urging the shell in an upward position, wherein an application of an axial force to the conveyance compresses the spring, allowing the outer shell to move downwardly while the mandrel remains substantially stationary, the pin engaging with the groove and rotating the jetting assembly and indexing assembly during movement thereof. The cutting tool may further comprise a base index assembly for engaging with a solid base within the wellbore and further comprise a bearing for allowing rotation of the jetting assembly and indexing assemblies. In an embodiment, the at least one cutting tool comprises at least a pair of nozzle bodies for forming the slots, the tool further comprising at least one centralizer disposed between the nozzle bodies, wherein the at least a pair of nozzle bodies are configured to be selectively deactivated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
         FIG. 1A  is a schematic view of an embodiment of a cutting tool deployed in a wellbore. 
         FIG. 1B  is a schematic view of an embodiment of multiple concentric casings. 
         FIGS. 2 a  and 2 b    are schematic perspective views, respectively, of an embodiment of a cutting tool. 
         FIG. 3  is a schematic view of slots formed in a casing with an embodiment of a cutting tool. 
         FIGS. 4A-4C  are schematic side views, respectively, of an embodiment of a cutting tool. 
         FIGS. 5A-5C  are cross-sectional views, respectively, taken along line  5 - 5  in  FIGS. 4 a   - 4   d.    
         FIG. 6  is a cross-sectional view taken along line  5 - 5  in  FIG. 4B . 
         FIG. 7  is a schematic view of slots formed in a casing with an embodiment of a cutting tool. 
         FIG. 8  is a flowchart depicting an embodiment of a method for forming slots in a wellbore casing. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1A , a schematic view of cutting tool or gun is indicated generally at  100 . The tool  100  is deployed into a wellbore  102  on a conveyance  104 , such as coiled tubing or the like. The tool  100  comprises an upper indexing assembly  107 , a jetting assembly  108 , and a lower or base indexing assembly  106 , discussed in more detail below. A casing  110  is deployed in the wellbore  102  and defines an area or annulus  112  between the casing  110  and the wellbore formation  114 . The casing  110  may comprise a single casing, such as that shown in  FIG. 1A , or multiple casings, such as multiple concentric casings comprising a casing  110  and at least one additional concentric casing  110   a , such as that shown in  FIG. 1B . In the case of multiple concentric casings, there may be concentric areas formed between the casings, such as the area  113  defined by casings  110  and  110   a  shown in  FIG. 1 a   , and the annulus  112  formed between the casing  110   a  and the wellbore formation, such as the wellbore formation  114 , as will be appreciated by those skilled in the art. 
     The conveyance or coiled tubing  104  is in fluid communication with suitable surface equipment  118 , such as high pressure fluid pumps, a source of abrasive fluid and/or cement, or the like, as will be appreciated by those skilled in the art. The tool  100  is suitably deployed in the wellbore  102  adjacent a solid base  116 , such as, but not limited to, a bridge plug, a sand plug, a cement plug, or any suitable solid base  116  for actuating the indexing assembly  106 , discussed in more detail below. The solid base  116  is preferably formed prior to introducing the tool  100  into the wellbore  102 . 
     Referring now to  FIGS. 2 a  and 2 b   , the jetting assembly  108  of the tool is shown having an upper portion  120  for attachment to the conveyance or coiled tubing  104  or the upper indexing assembly  107  and a lower portion  122  for attachment to the lower or base indexing assembly  106 . The jetting assembly  108  comprises an upper set of jets  124  and a lower set of jets  126 . In a non-limiting example, the upper set of jets  124  comprise three jets  124  arranged substantially equidistant about the circumference of the jetting assembly  108  (i.e. spaced about 120° apart along the circumference of the jetting assembly  108 ) and the lower set of jets  126  comprise three jets  126  arranged equidistant about the circumference of the jetting assembly  108  (i.e. about 120° along the circumference of the jetting assembly  108 ). The set of jets  124  and the set of jets  126  may each be located at substantially the same axial distance along the assembly  108  between the upper portion  120  and the lower portion  122 . The jets  124  and the jets  126  are spaced apart at about 60° along the circumference of the jetting assembly  108  and the centerline  128  of the jets  124  is spaced apart from the centerline  130  of the jets  126  by a predetermined distance, indicated by an arrow  132 . In a non-limiting example, the predetermined distance  132  may be about 2 inches or about 5 centimeters. 
     In an embodiment, best seen in  FIGS. 4A through 5C , a jetting assembly or tool  400  is disclosed. The tool  400  comprises an upper indexing assembly  407 , a jetting assembly  408 , and a lower or base indexing assembly  406 . The jetting assembly  408  comprises an upper nozzle body  424  and a lower nozzle body  426  spaced apart along the assembly  408  and having at least one centralizer  428  (four illustrated) disposed between the nozzle bodies  424  and  426  along the jetting assembly  408 . The nozzle bodies  424  and  426  define a plurality of nozzles  425  therein and in fluid communication with a central bore  430  defined along the jetting tool  400 . The centralizers  428  comprise a centralizer body  432  having at least one fin  434  extending therefrom. The fin or fins  434  of the centralizers  428  function to maintain radial alignment of the tool  400  and jetting assembly  408  within the borehole and thus provide a minimum radial spacing between the casing, such as the casing  110  and the nozzles  425 , as the jetting assembly and conveyance are moved to the desired location within the wellbore  102  and/or the wellbore formation  114 . 
     In the jetting tool  400 , the nozzle bodies  424  and  426  define four nozzles  425  spaced apart at about 90 degrees along the circumference of the nozzle body  424  or  426 . More or fewer nozzles  425  may be defined by the nozzle bodies  424  or  426 . The nozzles  425  are spaced apart by a predetermined distance, as indicated by an arrow  427 . The distance  427  defined by the nozzles  425  of the nozzle body  424  may be different than the distance  427  defined by the nozzles  425  of the nozzle body  426 . The nozzles  425  may be removable inserts formed as part of the jetting assembly  408  to enable different sized nozzles  425  to be placed as part of the nozzle bodies  424  or  426  and/or to enable maintenance and/or replacement of the nozzles  425 , as will be appreciated by those skilled in the art. 
     The upper indexing assembly  407  comprises an outer hollow shell or housing  436  slidably disposed about an inner mandrel  438 . The inner mandrel  438  has a groove  440  formed in an exterior surface thereof. The groove  440  extends in a helical or spiral direction in an axial direction along the exterior surface of the mandrel  438 . A pin or key  441  extends from an interior surface of the housing  436  of the upper indexing assembly  407  and engages with the surface defined by groove  440  of the mandrel  438 . More than one cooperating groove  440  and pin  441  may be formed as part of housing  436  and mandrel  438  of the upper indexing assembly  407  such as, but not limited to, a groove  440  and a pin  441  formed on opposing sides of the housing  436  and the mandrel  438 . The mandrel  438  extends into and defines part of the central bore  430  of the jetting assembly  408  and the lower indexing assembly  406 . A bushing  442  is fixedly disposed in the housing  436  downstream of the pin  441  and is biased by a compression spring  444  or similar biasing device. The spring  444  is disposed between the bushing  442  and the axially movable portion of the housing  436 , best seen in  FIGS. 4A and 5A . 
     A bearing  456  or similar device is disposed on the mandrel  438  adjacent the lower or base indexing assembly  406  to allow for rotation of the inner mandrel  438 , indexing assembly  407 , jetting assembly  408  and base indexing assembly  406 . The bearing  456  may be formed as part of a foot assembly  458  and disposed between an upper foot portion  452  and a lower foot portion  450 . 
     In operation, the tool  100  or  400  is disposed in the wellbore and the base indexing assembly  406  is axially moved in the wellbore  102  and disposed against or engaged with the solid base  116 , wherein vertical or axial movement of the tool  100  or  400  is prevented. The application of additional downward, axial, or downhole force to the tool  100  and conveyance  104 , such as by surface equipment  118  or the like, compresses the spring  444  and allows movement of the housing  436  within the indexing assembly  106 . The movement of the housing  436  allows the pin  436  to travel along the groove  440 , applying a force to and thereby rotating the mandrel  438  and thus rotating the indexing assembly  407 , jetting assembly  408  and base indexing assembly  406  about the bearing  446  of the base assembly  406 , while the indexing assembly  407 , jetting assembly  408  and base indexing assembly  406  remain axially stationary, i.e. do not move axially within the wellbore  102 . Those skilled in the art will appreciate that similar methods or devices for converting a reciprocating axial movement or translation into rotational movement or translation may be utilized to rotate the indexing assembly  407 , jetting assembly  408  and base indexing assembly  406 . 
     In order to form a slot or slots in the casing or casings  110  with the tool  100 , abrasive or jetting fluid is flowed from the surface equipment  118  through the conveyance  104  and out the jets  124  and  126  of the jetting assembly  108 . Force is applied to the tool  100  and conveyance  104  to rotate the jetting assembly  108 . The abrasive fluid flows from the jets  124  and  126  and will form slots  150  and  152  in the casing  110  as the jetting assembly  108  is rotated by the indexing assemblies  106  and  107 , as shown in  FIG. 3 , while the while the indexing assemblies  106  and  107  and jetting assembly  108  remain axially stationary. 
     In order to form a slot or slots in the casing or casings  110  with the tool  400 , abrasive or jetting fluid is flowed from the surface equipment  118  through the conveyance  104  and out the nozzles  425  of the jetting assembly  408 . An axial force is applied, such as intermittently or the like, to the tool  400  and conveyance  104  to rotate the jetting assembly  408 . The abrasive fluid flows from the nozzles  425  and will form slots  160  and  162  in the casing  110  as the jetting assembly  408  is rotated by the indexing assemblies  406  and  407 , as shown in  FIG. 7 , while the indexing assemblies  406  and  407  and the jetting assembly  408  remain axially stationary. 
     In an embodiment of the tool  400 , the upper nozzle body  424  may be inactive and the lower nozzle body  426  may be active. In such an embodiment, the nozzles  425  of the nozzle body  424  are blocked by a sleeve  446  disposed in the nozzle body  424  and thus are not in fluid communication with the central bore or passage  430 . The sleeve  446  is held in place with a number of shear pins  450  and set screws  448 , best seen in  FIG. 6 . With the sleeve  446  blocking the nozzles  425  of the nozzle body  424 , fluid flows only out of the nozzles  425  of the nozzle body  426 . To activate the upper nozzle body  424  and deactivate the lower nozzle body  426 , a ball  429  may be dropped into the conveyance  104  and the tool  400  from the surface. The ball  429  engages with a seat portion of the sleeve  446 , blocking fluid flow through the central bore  430  and allowing pressure to build up on the upstream side of the ball  429  and nozzle body  424 . When a predetermined pressure is reached, the shear pins  450  fail or shear, which allows the sleeve  446  to move downwardly in the nozzle body  424  to expose the nozzles  425  of the nozzle body  424  to the central bore  430 . The sleeve  446  may engage with a raised shoulder within the nozzle body  424  to prevent further downward movement of the sleeve  446  after the pins  450  have been sheared. A jetting operation may now be carried out through the nozzles  425  of the nozzle body  424  utilizing the indexing assemblies  406  and  407  as detailed hereinabove and further flow of jetting fluid through the central bore  430  is prevented by the presence of the ball  429 . 
     Those skilled in the art will appreciate that the amount of axial and rotational movement of the tools  100  or  400  and thus the size of the slots  150  and  152  or  160  and  162  formed are based on the length and orientation of the groove  440  formed in the inner mandrel and thus may be varied depending on the requirements of the casing or casings  110 . Thus, if the groove  440  has a short axial length, the corresponding slots  150 ,  152 ,  160 , or  162 , will be correspondingly short in length and may therefore comprise individual apertures rather than elongated slots as shown in  FIGS. 3 and 7 , discussed in more detail below. 
     In operation, the tool  100  will form a pattern of slots  101  in the casing as shown in  FIG. 3  and the tool  400  will form a pattern of slots  401  in the casing as shown in  FIG. 7 . The tool  100  may be used advantageously to create horizontal slots through a plurality of casings, such as concentric casings  110  and  110   a , or three (3) casings or the like, while forming slots  150 ,  152 ,  160 , and  162  that may cover substantially a full 360° of the interior surface of the casing or casings  110  or  110   a  while not cutting or severing the casing  110  or  110   a  into distinct portions thereof. 
     After the slots  101  or  401  are formed, a fluid, such as a sealing fluid such as cement or the like may be flowed from suitable surface equipment, such as the surface equipment  118 , through the conveyance or coiled tubing  104 , through the slots  150  and  152  and into the space  112  in order to seal the space  112  between the casing  104  and the formation  114 . Preferably, the tool  100  or  400  is withdrawn from the wellbore  102  prior to introduction of the cement or sealing fluid. The cement may comprise, but is not limited to, cement known by the commercial name of SqueezeCRETE and available from Schlumberger Corporation, or may comprise any suitable sealing fluid. 
     Referring now to  FIG. 8 , in a method of operation, indicated generally at  500 , a solid base  116 , such as a bridge plug, a sand plug, a cement plug or the like, is formed in a step  502  by any suitable method. In a step  504 , the tool  100  or  400  is introduced into the wellbore  102  on the conveyance  104 . In a step  506 , the tool  100  or  400  is set against the solid base  116 . In a step  508 , the tool  100  or  400  is indexed or rotated and abrasive or jetting fluid is flowed from the surface equipment  118  through the conveyance  104  and through the jets  124 ,  126  or the nozzles  425  to form slots  150 ,  152 ,  160 , or  162 . In a step  510 , a sealing fluid is flowed from suitable surface equipment, such as the surface equipment  118 , through the slots  150 ,  152 ,  160 , and  162  to seal the space or annulus  112  between the casing  104  and the formation  114  and/or the area  113  between multiple strings of casing  110  and  110   a  and thereby plugging or killing the wellbore  102 . 
     The preceding description has been presented with references to certain exemplary embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings. Instead, the scope of the application is to be defined by the appended claims, and equivalents thereof. 
     The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. In particular, every range of values (of the form, “from about a to about b,” or, equivalently, “from approximately a to b,” or, equivalently, “from approximately a-b”) disclosed herein is to be understood as referring to the power set (the set of all subsets) of the respective range of values. Accordingly, the protection sought herein is as set forth in the claims below.