Abstract:
A downhole debris recovery tool including a ported sub coupled to a debris sub, a suction tube disposed in the debris sub, and an annular jet pump sub disposed in the ported sub and fluidly connected to the suction tube is disclosed. A method of removing debris from a wellbore including the steps of lowering a downhole debris removal tool into the wellbore, the downhole debris removal tool having an annular jet pump sub, a mixing tube, a diffuser, and a suction tube, flowing a fluid through a bore of the annular jet pump sub, jetting the fluid from the annular jet pump sub into the mixing tube, displacing an initially static fluid in the mixing tube through the diffuser, thereby creating a vacuum effect in the suction tube to draw a debris-laden fluid into the downhole debris removal tool, and removing the tool downhole debris removal tool from the wellbore after a predetermined time interval is also disclosed. Further, an isolation valve including a housing, an inner tube disposed coaxially with the housing, and a gate, wherein the gate is configured to selectively close an annular space between the housing and the inner tube is disclosed.

Description:
BACKGROUND OF INVENTION 
     1. Field of the Invention 
     Embodiments disclosed herein generally relate to a downhole debris retrieval tool for removing debris from a wellbore. Further, embodiments disclosed herein relate to a downhole tool for debris removal with maximum efficiency at a low pump rates. 
     2. Background Art 
     A wellbore may be drilled in the earth for various purposes, such as hydrocarbon extraction, geothermal energy, or water. After a wellbore is drilled, the well bore is typically lined with casing. The casing preserves the shape of the well bore as well as provides a sealed conduit for fluid to be transported to the surface. 
     In general, it is desirable to maintain a clean wellbore to prevent possible complications that may occur from debris in the well bore. For example, accumulation of debris can prevent free movement of tools through the wellbore during operations, as well as possibly interfere with production of hydrocarbons or damage tools. Potential debris includes cuttings produced from the drilling of the wellbore, metallic debris from the various tools and components used in operations, and corrosion of the casing. Smaller debris may be circulated out of the well bore using drilling fluid; however, larger debris is sometimes unable to be circulated out of the well. Also, the well bore geometry may affect the accumulation of debris. In particular, horizontal or otherwise significantly angled portions in a well bore can cause the well bore to be more prone to debris accumulation. Because of this recognized problem, many tools and methods are currently used for cleaning out well bores. 
     One type of tool known in the art for collecting debris is the junk catcher, sometimes referred to as a junk basket, junk boot, or boot basket, depending on the particular configuration for collecting debris and the particular debris to be collected. The different junk catchers known in the art rely on various mechanisms to capture debris from the well bore. A common link between most junk catchers is that they rely on the movement of fluid in the well bore to capture the sort of debris discussed above. The movement of the fluid may be accomplished by surface pumps or by movement of the string of pipe or tubing to which the junk catcher is connected. Hereinafter, the term “work string” will be used to collectively refer to the string of pipe or tubing and all tools that may be used along with the junk catchers. For describing fluid flow, “uphole” refers to a direction in the well bore that is towards the surface, while “downhole” refers to a direction in the well bore that is towards the distal end of the well bore. 
     The use of coiled tubing and its ability to circulate fluids is often used to address debris problems once they are recognized. Coiled tubing runs involving cleanout fluids and downhole tools to clean the production tubing are often costly. 
     Accordingly, there exists a need for a more efficient tool and method for removing debris from a wellbore. 
     SUMMARY OF INVENTION 
     In one aspect, embodiments disclosed herein relate to a downhole debris recovery tool including a ported sub coupled to a debris sub, a suction tube disposed in the debris sub, and an annular jet pump sub disposed in the ported sub and fluidly connected to the suction tube. 
     In another aspect, embodiments disclosed herein relate to a method of removing debris from a wellbore including the steps of lowering a downhole debris removal tool into the wellbore, the downhole debris removal tool having an annular jet pump sub, a mixing tube, a diffuser, and a suction tube, flowing a fluid through a bore of the annular jet pump sub, jetting the fluid from the annular jet pump sub into the mixing tube, displacing an initially static fluid in the mixing tube through the diffuser, thereby creating a vacuum effect in the suction tube to draw a debris-laden fluid into the downhole debris removal tool, and removing the tool downhole debris removal tool from the wellbore after a predetermined time interval. 
     In yet another aspect, embodiments disclosed herein relate to an isolation valve including a housing, an inner tube disposed coaxially within the housing, and a gate, wherein the gate is configured to selectively close an annular space between the housing and the inner tube. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  show plots of jet pump operations and equations. 
         FIGS. 2A and 2B  show a side view and a cross sectional view, respectively, of a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 3  shows the overall operation of a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 4  shows a cross sectional view of a ported sub of downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 5  shows a cross sectional view of a debris sub section of downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 6  shows a cross sectional view of a bottom sub and a debris removal cap of a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 7  is a perspective view of a screen of a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 8  shows a cross sectional view of a bottom sub and a debris removal cap of downhole debris removal tool in accordance with embodiments disclosed herein, with the debris removal cap removed from its assembled position. 
         FIGS. 9-11  are graphs of suction flow rate versus the pump flow rate for 0.16 d/D, 0.25 d/D, and 0.39 d/D ratio rings, respectively, of a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIG. 12  is a schematic view of a test procedure for evaluating the amount of debris lifted by a downhole debris removal tool in accordance with embodiments disclosed herein. 
         FIGS. 13A and 13B  show perspective and cross sectional views, respectively, of an annular jet pump sub in accordance with embodiments disclosed herein. 
         FIG. 14  shows an exploded view of an isolation valve in accordance with embodiments disclosed herein. 
         FIGS. 15A and 15B  show open and closed configurations, respectively, of an isolation valve in accordance with embodiments disclosed herein. 
         FIG. 16  shows an exploded view of an isolation valve in accordance with embodiments disclosed herein. 
         FIGS. 17A and 17B  show open and closed views, respectively, of an isolation valve in accordance with embodiments disclosed herein. 
         FIGS. 18A and 18B  show open and closed cross sectional views, respectively, of an isolation valve in accordance with embodiments disclosed herein. 
         FIG. 19  shows a cross sectional view of a portion of a debris catcher tool in accordance with embodiments disclosed herein. 
         FIGS. 20A and 20B  show open and closed cross sectional views, respectively, of a drain pin in accordance with embodiments disclosed herein. 
         FIG. 21A  shows a cross sectional view of a debris catcher tool in accordance with embodiments disclosed herein;  FIG. 21B  shows a close-perspective view of portion  2100  of  FIG. 21A . 
         FIG. 22  shows a detailed view of a portion of a debris catcher tool in accordance with embodiments disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     Generally, embodiments of the present disclosure relate to a downhole tool for removing debris from a wellbore. More specifically, embodiments disclosed herein relate to a downhole debris removal tool that includes an annular jet pump. Further, certain embodiments disclosed herein relate to a downhole tool for debris removal with maximum efficiency at a low pump rates. 
     A downhole debris removal tool, in accordance with embodiments disclosed herein, includes a jet pump device. Generally, a jet pump is a fluid device used to move a volume of fluid. The volume of fluid is moved by means of a suction tube, a high pressure jet, a mixing tube, and a diffuser. The high pressure jet injects fluid into the mixing tube, displacing the fluid that was originally static in the mixing tube. This displacement of fluid due to the high pressure jet imparting momentum to the fluid causes suction at the end of the suction tube. The high pressure jet and the entrained fluid mix in the mixing tube and exit through the diffuser. 
     Basic principles of jet pump operation may generally be explained by Equation 1 below, with reference to  FIGS. 1A and 1B .
 
Jet Pump Efficiency=( H   D   −H   S   /H   J   −H   D )( Q   S   /Q   J )  (1)
 
where H D  is discharge head, H S  is suction head, H J  is jet head, Q S  is suction volume flow, and Q J  is driving volume flow. In accordance with certain embodiments of the present disclosure, for maximum jet pump efficiency, an inlet of the annular jet pump is smooth and convergent, while the diffuser is divergent. Additionally, the ratio of the inner diameter, d, of the jet to the inner diameter, D, of the mixing tube ranges from 0.14 to 0.9. Further, the jet standoff distance or driving nozzle distance, l, ranges from 0.8 to 2.0 inches. The mixing tube length, L m , is approximately 7 times the inner diameter of the mixing tube, D.
 
     Embodiments of the present disclosure provide a downhole debris removal tool for removing debris from a completed wellbore with a low rig pump rate. An operator may circulate fluid conventionally down a drillstring at a low flow rate when desirable, e.g., in wellbores with open perforations or where a pressure sensitive formation isolation valve (FIV) is used. The downhole debris removal tool, in accordance with embodiments disclosed herein, lifts (through a vacuum effect) a column of fluid from the bottom of the tool at a velocity high enough to capture heavy debris, such as perforating debris or milling debris, with a low rig pump rate. In contrast, in conventional debris removal tools, high pump flow rates are required to remove such heavy debris. In certain embodiments, the downhole debris removal tool has sufficient capacity to store the collected debris in-situ, thereby providing easy removal and disposal of the debris when the tool is returned to the surface. 
     Referring now to  FIGS. 2A and 2B , a side view and a cross sectional view of a downhole debris removal tool  200 , in accordance with embodiments of the present disclosure, are shown, respectively. The downhole debris removal tool  200  includes a top sub  201 , a ported sub  203 , a debris sub  202 , a bottom sub  205 , and a debris removal cap  207 . The top sub  201  is configured to connect to a drill string and includes a central bore  243  configured to provide a flow of fluid through the downhole debris removal tool  200 . In certain embodiments, the debris sub  202  may be made up of more than one tubing section coupled together. For example, an extension piece, or additional tubing, may be added to the debris sub  202  to provide additional collection and storage space for debris. A section of washpipe (not shown) may be provided below the downhole debris removal tool  200 . 
     The ported sub  203  is disposed below the top sub  201  and houses a mixing tube  208 , a diffuser  210 , and an annular jet pump sub  206 . The ported sub  203  is a generally cylindrical component and includes a plurality of ports configured to align with the diffuser  210  proximate the upper end of the ported sub  203 , thereby allowing fluids to exit the downhole debris removal tool  200 . The ported sub  203  may be connected to the top sub  201  by any mechanism known in the art, for example, threaded connection, welding, etc. 
     As shown in more detail in  FIG. 4 , the annular jet pump sub  206  is a component disposed within the ported sub  203 . The annular jet pump sub  206  includes a bore  228  in fluid connection with the central bore of the top sub  201 . At least one small opening or jet  209  fluidly connects the bore  228  of the annular jet pump sub  206  to the mixing tube  208 . The jets  209  provide a flow of fluid from the drill string into the mixing tube  208  to displace initially static fluid in the mixing tube  208 . The fluid then flows upward in the mixing tube  208  and exits the ported sub  203  through the diffuser  210 , as indicated by the solid black lines. 
     Referring to  FIGS. 2 ,  4 , and  5 , a lower end  230  of the annular jet pump sub  206  is disposed proximate an exit end of a screen  214  disposed in the debris sub  202 , forming an inlet  226  into the mixing tube  208 . Fluid suctioned up through the debris sub  202  enters the mixing tube  208  through the inlet  226  and exits the mixing tube  208  through one or more diffusers  210 . An annular jet cup  232  is disposed over the lower end  230  of the annular jet pump sub  206  and configured to at least partially cover jets  209  to provide a ring nozzle. The at least one jet  209  size may be changed by varying the gap between the annular jet cup  232  and the annular jet pump sub  206 , thereby providing for flexible operation of the downhole debris removal tool  200 . The gap may be varied by moving the annular jet cup  232  in an uphole or downhole direction along the annular jet pump sub  206 . In one embodiment, the annular jet cup  232  may be threadedly coupled to the annular jet pump sub  206 , thereby allowing the annular jet cup  232  to be threaded into a position that provides a desired gap between annular jet cup  232  and the annular jet pump sub  206 . 
     A spacer ring  224  may be disposed around the lower end  230  of the annular jet pump sub  206  and proximate a shoulder  234  formed on an outer surface of the lower end  230 . The spacer ring  224  is assembled to the annular jet pump sub  206  and the annular jet cup  232  is disposed over the lower end  230  and the spacer ring  224 . Thus, the spacer ring  224  limits the movement of the annular jet cup  232 . One or more spacer rings  224  with varying thickness may be used to selectively choose the location of the assembled annular jet cup  232 , and provide a pre-selected gap between the annular jet cup  232  and the annular jet pump sub  206 . That is, the thickness of the spacer ring  224  may be selected so as to provide a desired d/D ratio. Varying the gap between the annular jet cup  232  and the annular jet pump sub  206  also provides for adjustment of the distance of the at least one jet  209  from the mixing tube  208  entrance. Thus, the jet standoff distance (l) of the tool  200  may be increased, thereby promoting jet pump efficiency. 
     Referring back to  FIGS. 2A and 2B , the debris sub  202  is coupled to a lower end of the ported sub  203  and houses a suction tube  204 , a flow diverter  212 , and the screen  214 . The debris sub  202  may be connected to the ported sub  203  by any mechanism known in the art, for example, threaded connection, welding, etc. The debris sub  202  is configured to separate and collect debris from a fluid stream as the fluid is vacuumed or suctioned up through the downhole debris recovery tool  200 . Referring also to  FIG. 5 , the suction tube  204  is configured to receive a stream of fluid and debris from the wellbore and directs the stream through the flow diverter  212 . In one embodiment, the flow diverter  212  may be a spiral flow diverter. In this embodiment, the spiral flow diverter is configured to impart rotation to the fluid/debris stream as it enters a debris chamber from the suction tube  204 . The rotation imparted to the fluid helps separate the fluid stream from the debris. The debris separated from the fluid stream drops down and is contained within the debris sub  202 . A debris removal cap  207  is coupled to a lower end of the debris sub  202  and may be removed from the downhole debris recovery tool  200  at the surface to remove the collected debris from the downhole debris recovery  200  (see  FIGS. 6 and 8 ). The downhole debris recovery tool  200  may be configured to collect a specified anticipated debris volume. The length of the debris sub  202  may be selected based on the anticipated debris volume in the wellbore. 
     In one embodiment, the screen  214  may be a cylindrical component with a small perforations disposed on an outside surface, as shown in  FIG. 7 . In alternate embodiments, the outer cylindrical surface of the screening device  214  may be formed from a wire mesh cloth, as shown in  FIG. 5 . One of ordinary skill in the art will appreciate that any screening device known in the art for debris recovery may be used without departing from the scope of embodiments disclosed herein. In certain embodiments, the screen  214  is a low differential pressure screen. A packing element  240  and an element seal ring  242  are disposed around a pin end of the screen  214  to prevent fluid from bypassing the screen  214 . The fluid stream flowing through the diverter  212  enters the screen  214 . Debris larger than the perforations or mesh size of the screen cloth remains on the surface of the screen or fall and remain within the debris sub  202 . The filtered stream of fluid is then further suctioned up into the ported sub  203 . 
       FIG. 3  shows a general overview of the operation of the downhole debris removal tool  200 . Solid arrow lines indicate driving flow, while dashed arrow lines indicate suction flow of the tool. As shown, fluid is pumped down through the central bore of the top sub  201  and into the bore  228  of the annular jet pump sub  206 . The fluid is pumped at a low flow rate. For example, in certain embodiments, the fluid flowed into the bore  228  of the annular jet pump sub  206  is pumped at a rate of less than 10 BPM. In some embodiments, the fluid flowed through the bore  228  of the annular jet pump sub  206  is pumped at a rate of approximately 7 BPM. The fluid exits the annular jet pump sub  206  through a high pressure jet  209  into the mixing tube  208 . Injection of the fluid into the mixing tube  208  displaces the originally static fluid in the mixing tube  208 , thereby causing suction at the suction tube  204 . The high pressure jet fluid and the entrained fluid mix in the mixing tube  208  and exit through the diffuser  210 . The fluid exiting the diffuser  210  and vacuum effect at the suction tube  204  dislodges and removes debris from the wellbore. 
     In certain embodiments, at least one extension piece may be added to the downhole debris removal tool to increase the capacity of the debris sub  202  such that more debris may be stored/collected therein.  FIGS. 21A and 21B  show one embodiment having an extension piece  2100  disposed between two sections of debris sub  202 . The at least one extension piece may have an inner tube  2104  configured to align with the suction tube  204 . Additionally, in select embodiments, the inner tube  2104  of the expansion piece  2100  may be coupled to a flow diverter  212 , and/or inner tubes  2104  of additional expansion pieces  2100 . The at least one extension piece  2100  may also have an outer housing  2102  configured to couple to at least one debris sub  202 , and/or outer housing  2102  of additional expansion pieces. One of ordinary skill in the art will appreciate that multiple extension pieces may be added to the downhole debris recovery tool, and that components may be coupled by any means known in the art. For example, components may be coupled using threads, welding, etc. 
     At least one isolation valve  2106  may be integrated into the at least one extension piece  2100 , as shown in  FIG. 21 . Alternatively, one of ordinary skill in the art will appreciate that the extension piece  2100  and the isolation valve  2106  may be independent components, or in another embodiment, the isolation valve  2106  may be integrated into a debris sub  202 . In select embodiments, more than one isolation valve may be used such that multiple chambers may be created within the debris removal tool. 
     Referring to  FIG. 14 , an isolation valve  1400  in accordance with embodiments disclosed herein is shown. The isolation valve  1400  includes a housing  1402 , upper and lower portions of an inner tube, referred to herein as velocity tube  1404 , an annular space  1426  disposed between the housing  1402  and the velocity tube  1404 , a gate  1406 , a cutout  1414 , and a central axis  1420 . The velocity tube  1404  and the housing  1402  may have inner and outer diameters substantially the same as the inner and outer diameters of suction tube  204  and debris sub  202 , respectively, of  FIGS. 2A and 2B . The isolation valve  1400  may also include a cutout  1414  disposed through the velocity tube  1404  and the housing  1402 , which accommodates a gate  1406 . Gate  1406  may rotate a cutout axis  1416 . The cutout axis  1416  may be substantially perpendicular to the central axis  1420  of the isolation valve  1400 . The gate  1406  may further include an o-ring  1408 , a circlip  1410 , a hex socket head  1422 , a gate hole  1418 , and a gate hole axis  1424 . The gate hole  1418  may have a diameter substantially equal to the inner diameter of the upper and lower portions of velocity tube  1404 . 
       FIGS. 15A and 15B  show open and closed configurations, respectively, of the isolation valve  1400  shown in  FIG. 14 . As shown in  FIG. 15A , the isolation valve  1400  is open when the gate hole axis  1424  is axially aligned with central axis  1420 , thus allowing flow through both the velocity tube  1404  and the annular space  1426 .  FIG. 15B  shows a closed isolation valve  1400  having the gate hole axis  1424  disposed perpendicular to the central axis  1420 . In the closed configuration, flow through the velocity tube  1404  and the annular space  1426  is restricted. In the embodiment shown in  FIGS. 14 ,  15 A, and  15 B, the hex socket head  1422  may be engaged with a corresponding tool (not shown) and rotated to change the position of the gate  1406  relative to the velocity tube  1404  and annular space  1426 . Other socket head geometries, such as square or star socket heads, may also be used. Furthermore, one of ordinary skill in the art will appreciate that other mechanical or hydraulic means for controlling the gate may be used without departing from the scope of the present disclosure. For example, a shearing pin may be used to control the actuation of isolation valve  1400  in accordance with embodiments disclosed herein. 
       FIGS. 16 ,  17 A, and  17 B show another exemplary isolation valve  1600  in accordance with the embodiments disclosed herein. Isolation valve  1600  allows uninterrupted flow through velocity tube  1604  and selectively allows flow through annular space  1626 . Isolation valve  1600  includes a housing  1602 , a velocity tube  1604 , an annular space  1626  disposed between housing  1602  and velocity tube  1604 , a central axis  1620 , a gate  1606 , and rotatable brackets  1608 . The gate  1606  may further include a hole  1614  through which velocity tube  1604  is disposed, and at least one curved surface  1610  configured to allow movement of the gate  1606  relative to the velocity tube  1604 . Rotatable brackets  1608  may be configured to couple to the gate  1606  and to bracket holes  1616  disposed in the housing  1602 . Additionally, a hex socket head  1622  may be disposed on at least one of the rotatable brackets  1608 . Alternatively, other socket head geometries, such as square or star socket heads, may be used. The rotatable brackets  1608 , together with the gate  1606 , may be rotated about a gate axis  1624  relative to the velocity tube  1604 . 
     Referring to  FIGS. 17A and 18A , an isolation valve  1600  is shown in an open position in accordance with embodiments disclosed herein. The gate  1606  may be positioned such that flow through the annular space  1626  is allowed ( FIG. 17A ). In certain embodiments, the at least one curved surface  1610  of the opened gate  1606  may contact an outer surface of the velocity tube  1604 . Referring to  FIGS. 17B and 18B , the gate  1606  of isolation valve  1600  may be positioned such that flow through the annular space  1626  is restricted. In the embodiment shown in  FIGS. 17A ,  17 B,  18 A, and  18 B, flow through the velocity tube  1604  of isolation valve  1600  is allowed, regardless of the position of gate  1606 . 
     During operation, the at least one isolation valve remains open so that the suction action of the tool is maintained. It may be advantageous to close the at least one isolation valve when the downhole debris removal tool is pulled from the well so that an extension piece may be installed. While the isolation valve is in the closed position, components may be added, removed, and/or replaced therebelow without fluid and debris that may have accumulated above the isolation valve spilling out into the wellbore or onto the deck. Additionally, after the debris removal tool is removed from the well, components therebelow may be removed and the isolation valve may be opened so that accumulated debris may be removed from the tool. 
     Referring back to  FIG. 3 , suction at the suction tube  204  provided by the annular jet pump sub  206  may draw fluid and debris into the downhole debris removal tool  200 , and through at least one isolation valve. After passing through the at least one isolation valve, the flow diverter  212  diverts the fluid/debris mix from the suction tube  204  downward, as shown in more detail in  FIG. 5 . The flow diverter  212  is configured to provide rotation to the fluid stream as it is diverted downwards. The rotation provided to the fluid stream may help separate the debris from the fluid stream due to the centrifugal effect and the greater density of the debris. Thus, the flow diverter  212  separates larger pieces of debris from the fluid. The debris separated from the fluid streams drop downwards within the debris sub  202 . After the fluid stream exits the diverter, it travels through the screen  214 . The screen  214  is configured to remove additional debris entrained in the fluid stream. 
     As shown in  FIG. 22 , in select embodiments, at least one magnet  2202  may be disposed on or near a lower end of the screen  214 . The magnets  2202  may magnetically attract metallic debris suspended in the fluid and may prevent the metallic debris from clogging the screen  214 .  FIG. 22  shows an embodiment having magnets  2202  that are ring-shaped and disposed around an outer surface of shaft  2206 . The magnets may be rare earth magnets, such as samarium-cobalt or neodymium-iron-boron (NIB) magnets. One of ordinary skill in the art will appreciate that magnets of other shapes and sizes may also be used. Additionally, the embodiment of  FIG. 22  shows a magnet cover  2204  disposed around the magnets  2202  such that the fluid may not directly contact the magnets  2202 . The cover  2204  may protect the magnets  2202  from being damaged by debris. 
     Referring back to  FIG. 3 , after passing through the screen  214 , the fluid flows past the annular jet pump sub  206  into the mixing tube  208 . The fluid is then returned to the casing annulus (not shown) through the diffuser  210 . In embodiments disclosed herein, as shown in  FIGS. 2-8 , the fluid entering the mixing tube  208  from the suction tube  204  does not significantly change direction until after the fluid enters the diffuser  210  and is diverted into the casing annulus. In contrast, in conventional debris removal tools with conventional nozzle arrangements, fluid flowing from the suction tube changes direction 180 degrees to enter the mixing tube. 
     After completion of the debris recovery job, the drill string is pulled from the wellbore and the downhole debris recovery tool  200  is returned to the surface. As shown in  FIGS. 6 and 8 , a retaining screw  220  may be removed from the debris removal cap  207  to allow the debris removal cap  207  to be removed from the downhole debris recovery tool  200 , thereby allowing the debris to be easily removed (indicated by dashed arrows) from the debris sub  202 . 
     In certain embodiments, a drain pin may be disposed in bottom sub  205  and may be opened before removing debris removal cap  207  so that fluid may be emptied from the bottom sub  205  and/or the debris sub  202 . Referring to  FIG. 19 , the drain pin  1902  may be opened to allow fluid from at least one cavity  1904 , disposed in bottom sub  205 , to flow out through suction tube  204 . In certain embodiments, a hex socket head  1906  may be disposed on the drain pin  1902 . One of ordinary skill in the art will appreciate that alternative socket geometries, such as square or star, may be used without departing from the scope of the present disclosure. The hex socket head  1906  may be engaged with a corresponding tool (not shown) and rotated to open or close the drain pin  1902 .  FIGS. 20A and 20B  show cross-sectional views of a debris removal tool having a drain pin  1902 .  FIG. 20A  shows drain pin  1902  in the open position, allowing fluid communication between at least one cavity  1904  and suction tube  204 . In certain embodiments, the space created by the opened drain pin  1902  may be sized to prevent debris from escaping with the fluid.  FIG. 20B  shows drain pin  1902  in the closed position preventing fluid in cavity  1904  from entering suction tube  204 . It may be advantageous to open drain pin  1902  prior to removing debris removal cap  207  so that fluid may be released from the tool before debris removal, thereby preventing the fluid from spilling out onto, for example, the rig floor. 
     Referring now to  FIGS. 13A and 13B , an alternate embodiment of an annular jet pump sub  306  in accordance with embodiments of the present disclosure is shown. Annular jet pump sub  306  is disposed within a ported sub  303  which provides a mixing tube  308 , and includes a two staged annular jet pump  360 . As shown, the annular jet pump sub  306  includes two stages  313 ,  315 . The annular jet pump sub  306  includes a bore  328  in fluid connection with the central bore of a top sub  301 . As shown, the first stage  313  includes at least one small opening or jet  309  disposed near a lower end of the annular jet pump sub  306  and the second stage  315  includes at least one small opening or jet  311  disposed axially above the first stage  313 . The jets  309 ,  311  fluidly connect the bore  328  of the annular jet pump sub  306  to the mixing tube  308 . 
     The two stages  313 ,  315  of the annular jet pump sub  306  may provide a more efficient pumping tool. In particular, the two staged annular jet pump  360  may reduce the pumping flow rate of the tool and double the overall efficiency of the downhole debris removal tool  300 . In the embodiment shown in  FIGS. 13A and 13B , a flow of fluid exits the annular jet pump sub  306  through jets  309  of first stage  313  into mixing tube  308 . Injection of the fluid into the mixing tube  308  displaces the originally static fluid in the mixing tube  308 , thereby causing suction at a suction tube ( 204  in  FIG. 3 ) disposed below the annular jet pump sub  306 . Additionally, a flow of fluid exits the annular jet pump sub  306  through jets  311  of second stage  315  into mixing tube  308 . The flow of fluid exiting the annular jet pump sub  306  through second stage  315  accelerates fluid flow in the mixing tube  308 . The fluid then flows upward in the mixing tube  308  and exits the ported sub through the diffuser  310 . The suction provided by the first stage  313  and the acceleration of fluid provided by the second stage  315  of the annular jet pump sub  306  may allow a small volume of fluid to pull a larger volume of fluid with a lower pressure than a one-stage annular jet pump. 
     Referring to  FIGS. 5 and 13  together, a lower end  330  of the annular jet pump sub  306  is disposed proximate an exit end of a screen  214  disposed in the debris sub  202 , forming an inlet (not shown) into the mixing tube  308 . Fluid suctioned up through the debris sub  202  enters the mixing tube  308  through the inlet (inlet) and exits the mixing tube  308  through one or more diffusers  310 . An annular jet cup  323  may be disposed over the lower end  330  of the annular jet pump sub  306  and configured to at least partially cover jets  309  of the first stage  313  to provide a ring nozzle. A second annular jet cup  325  may be disposed around the annular jet pump sub  306  proximate the second stage  315  and configured to at least partially cover jets  311  to provide a ring nozzle. One of ordinary skill in the art will appreciate that based on the specific needs of a given application, the annular jet pump sub  306  may include an annular jet cup  323  for only the first stage  313 , an annular jet cup  325  for only the second stage  315 , or an annular jet cup  323 ,  325  for both the first and second stages  313 ,  315 . The size of the jets  309 ,  311  may be changed by varying the gap between the annular jet cup  323 ,  325  and the annular jet pump sub  306 , thereby providing for flexible operation of the downhole debris removal tool  300 . The gap may be varied by moving the annular jet cup  323 ,  325  in an uphole or downhole direction along the annular jet pump sub  306 . In one embodiment, the annular jet cup  323 ,  325  may be threadedly coupled to the annular jet pump sub  306 , thereby allowing the annular jet cup  323 ,  325  to be threaded into a position that provides a desired gap between the annular jet cup  323 ,  325  and the annular jet pump sub  306 . 
     As discussed above, a spacer ring (not shown) may be disposed around the lower end  330  of the annular jet pump sub  306  and proximate a shoulder (not shown) formed on an outer surface of the lower end  330 . The spacer ring (not shown) may limit the movement of the annular jet cup  323 ,  325 . One or more spacer rings with varying thickness may be used to selectively choose the location of the assembled annular jet cup  323 ,  325 , and provide a pre-selected gap between the annular jet cup  323 ,  325  and the annular jet pump sub  306 . That is, the thickness of the spacer ring may be selected so as to provide a desired d/D ratio. Varying the gap between the annular jet cup  323 ,  325  and the annular jet pump sub  306  also provides for adjustment of the distance of the at least one jet  309 ,  311  from the mixing tube  308  entrance. Thus, the jet standoff distance (l) of the tool  300  may be increased, thereby promoting jet pump efficiency 
     Tests 
     Tests were run on various embodiments of the present disclosure. A summary of these tests and the results determined are described below. 
     A 7⅞″ downhole debris recovery tool, in accordance with embodiments disclosed herein, was tested to evaluate the suction flow (flow at the pin end of the tool) for a given driving flow (pump flow rate through the tool). The flow rates at each location were determined using flow meters. To evaluate the suction flow, fluid was pumped through the tool at 20-425 gpm for 2-3 minutes at each pump rate. Pump pressure, pump flow rate, and in-line flow meter rate were recorded. The tool was tested with various spacer rings to provide 0.16 d/D, 0.25 d/D, and 0.39 d/D ratio rings. The results of this part of the test are summarized below in Tables 1-3. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 0.16 d/D Ratio Ring Test Results 
               
             
          
           
               
                 Pump Rate 
                 Standpipe 
                 Flow Meter 
               
               
                 (GPM) 
                 pressure (PSI) 
                 Rate (GPM) 
               
               
                   
               
             
          
           
               
                 30 
                 50 
                 11.5 
               
               
                 45 
                 100 
                 17 
               
               
                 65 
                 175 
                 24.5 
               
               
                 90 
                 350 
                 40 
               
               
                 120 
                 450 
                 58.5 
               
               
                 140 
                 500 
                 73 
               
               
                 250 
                 350 
                 75 
               
               
                 275 
                 450 
                 85.5 
               
               
                 300 
                 500 
                 79.5 
               
               
                 325 
                 650 
                 88 
               
               
                 350 
                 750 
                 89 
               
               
                 375 
                 800 
                 91 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 0.25 d/D Ratio Ring Test Results 
               
             
          
           
               
                 Pump Rate 
                 Standpipe 
                 Flow Meter 
               
               
                 (GPM) 
                 pressure (PSI) 
                 Rate (GPM) 
               
               
                   
               
             
          
           
               
                 300 
                 250 
                 57.5 
               
               
                 325 
                 300 
                 65 
               
               
                 350 
                 400 
                 69 
               
               
                 375 
                 450 
                 75.6 
               
               
                 400 
                 525 
                 81 
               
               
                 425 
                 600 
                 85 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 0.39 d/D Ratio Ring Test Results 
               
             
          
           
               
                 Pump Rate 
                 Standpipe 
                 Flow Meter 
               
               
                 (GPM) 
                 pressure (PSI) 
                 Rate (GPM) 
               
               
                   
               
             
          
           
               
                 300 
                 37 
                 31.5 
               
               
                 325 
                 50 
                 40.5 
               
               
                 350 
                 75 
                 42.5 
               
               
                 375 
                 100 
                 46.5 
               
               
                 400 
                 125 
                 52 
               
               
                 425 
                 150 
                 55.5 
               
               
                   
               
             
          
         
       
     
     Plots of suction flow rate versus the pump flow rate are shown in  FIGS. 9-11  for the 0.16 d/D, 0.25 d/D, and 0.39 d/D ratio rings, respectively. 
     Additionally, the 7⅞″ downhole debris recovery tool was tested to determine if the tool could lift heaving casing debris along with sand. The debris used in each test varied and included sand, metal debris, set screws, gravel, and o-rings. In one test, a packer plug retrieval/perforating debris cleaning trip after firing perforating guns was replicated.  FIG. 12  shows the test step up for this part of the test. For this test, a packer plug fixture was placed in the casing and 125 lbs of sand was poured on top of the plug. Then, 10-20 lbs of perforating debris was poured on top of the sand. Fluid was pumped through the tool at 200 GPM. Once the test was completed, the debris removal cap was removed and the debris was collected and measured. The results of this part of the test are summarized in Tables 9 and 10 below for 0.25 d/D ratio ring and 0.16 d/D ratio, respectively, where TD is target depth. 
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Metal Debris Test - 200 GPM 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (7 mins to TD) 5 min 
                 150-200 
                 200-220 
                 15 lbs steel 
                 12 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                 shavings; 
                 shavings; 
               
               
                   
                 TD 
                   
                   
                 100¼-20 screws; 
                 13¼-20 screws; 
               
               
                   
                   
                   
                   
                 100⅜-16 
                 24⅜-16 
               
               
                   
                   
                   
                   
                 screws 
                 screws 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Partial Sand Load and Metal Debris Test - 200 GPM 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (8 mins to TD) 5 min 
                 150-200 
                 220 
                 15 lbs steel 
                 115 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                 shavings; 
                 shavings, 
               
               
                   
                 TD (1 st  trip) 
                   
                   
                 100¼-20 screws; 
                 sand, and 
               
               
                   
                   
                   
                   
                 100⅜-16 
                 rocks 
               
               
                   
                   
                   
                   
                 screws; 150 lbs 
               
               
                   
                   
                   
                   
                 sand; 100 lbs 
               
               
                   
                   
                   
                   
                 rocks 
               
               
                 15-20 
                 (8 mins to TD) 5 min 
                 400 
                 305 
                 Same 
                 105 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                   
                 shavings, 
               
               
                   
                 TD (2 nd  trip) 
                   
                   
                   
                 sand, and 
               
               
                   
                   
                   
                   
                   
                 rocks 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Full Sand Load Test - 200 GPM 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (8 mins to TD) 
                 150-200 
                 222 
                 300 lbs 
                 170 lbs 
               
               
                   
                 5 min circulation 
                   
                   
                 sand 
                 sand 
               
               
                   
                 after reaching 
               
               
                   
                 TD (1 st  trip) 
               
               
                 15-20 
                 (5 mins to TD) 
                 400-500 
                 410 
                 Same 
                 190 lbs 
               
               
                   
                 5 min circulation 
                   
                   
                   
                 sand 
               
               
                   
                 after reaching 
               
               
                   
                 TD (2 nd  trip) 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Partial Sand Load and O-ring Test - 200 GPM 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (5 mins to TD) 5 min 
                 150-200 
                 220 
                 150 lbs sand; 8 
                 108 lbs sand; 
               
               
                   
                 circulation after reaching 
                   
                   
                 3″ o-rings; 5 
                 10 0.75″ o- 
               
               
                   
                 TD (1 st  trip) 
                   
                   
                 plastic ring 
                 rings; 1 plastic 
               
               
                   
                   
                   
                   
                 chucks; 7 o- 
                 ring chunks; 1 
               
               
                   
                   
                   
                   
                 ring chunks; 
                 o-ring chunk 
               
               
                   
                   
                   
                   
                 10 0.75″ o- 
               
               
                   
                   
                   
                   
                 rings 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Partial Sand Load and Metal Debris Test - 400 GPM 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (7 mins to TD) 5 min 
                 400-500 
                 416 
                 15 lbs steel 
                 Less than 20 lbs 
               
               
                   
                 circulation after reaching 
                   
                   
                 shavings; 
                 sand, 
               
               
                   
                 TD (1 st  trip) 
                   
                   
                 100¼-20 screws; 
                 gravel, metal 
               
               
                   
                   
                   
                   
                 100/-16 
                 shavings 
               
               
                   
                   
                   
                   
                 screws; 150 lbs 
               
               
                   
                   
                   
                   
                 sand; 100 lbs 
               
               
                   
                   
                   
                   
                 rocks 
               
               
                 15-20 
                 (5 mins to TD) 5 min 
                 400-500 
                 410 
                 Same 
                 177 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                   
                 shavings, 
               
               
                   
                 TD (2 nd  trip) 
                   
                   
                   
                 sand, rocks, 
               
               
                   
                   
                   
                   
                   
                 1⅜-16 screw 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 9 
               
             
             
               
                   
               
               
                 Packer Plug Perforation Debris Test with 0.25 d/D Ratio Ring 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (4 mins to TD) 2 min 
                 150-200 
                 250 
                  15 lbs perf. 
                 100 lbs 
               
               
                   
                 circulation after reaching 
                   
                   
                 Gun debris 
                 Sand and 
               
               
                   
                 TD (1 st  trip) 
                   
                   
                 125 lbs sand 
                 some debris 
               
               
                 15-20 
                 (3 mins to TD) 2 min 
                 400 
                 400 
                 Same 
                 3.5 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                   
                 perf. Gun 
               
               
                   
                 TD (2 nd  trip) 
                   
                   
                   
                 debris, some 
               
               
                   
                   
                   
                   
                   
                 sand 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                 Packer Plug Perforation Debris Test with 0.16 d/D Ratio Ring 
               
             
          
           
               
                   
                   
                 Circulation 
                 Pump 
                   
                   
               
               
                   
                   
                 Pressure 
                 Rate 
                 Debris 
                 Debris 
               
               
                 RPM 
                 Circulation Time 
                 (PSI) 
                 (GPM) 
                 Dropped 
                 Recovered 
               
               
                   
               
               
                 15-20 
                 (5 mins to TD) 5 min 
                 650 
                 325 
                  15 lbs perf. 
                 109 lbs 
               
               
                   
                 circulation after reaching 
                   
                   
                 Gun debris 
                 Sand and 
               
               
                   
                 TD (1 st  trip) 
                   
                   
                 125 lbs sand 
                 some debris 
               
               
                 15-20 
                 (3 mins to TD) 5 min 
                 700 
                 350 
                 Same 
                  10 lbs steel 
               
               
                   
                 circulation after reaching 
                   
                   
                   
                 perf. Gun 
               
               
                   
                 TD (2 nd  trip) 
                   
                   
                   
                 debris, some 
               
               
                   
                   
                   
                   
                   
                 sand 
               
               
                   
               
             
          
         
       
     
     During these tests, a conventional debris removal tool was also tested and compared with the tool of the present invention. Generally, the downhole debris removal tool of the present disclosure had a lower overall operating pressure. It was also observed that the tool can be reciprocated to TD several times before pulling the string out of the hole to reduce the number of trips. The flow rates recorded during the tests were based on a 1.5 inch inlet on the bottom of the tool. It was also determined that the overall jet pump size could be increased to boost performance by reducing the O.D. of the jet pump sub. 
     From the results of the test performed, it was determined that the smaller the d or inner diameter of the jet, the stronger the suction at the suction tube and the higher the efficiency of the jet pump. However, it was observed that an inner diameter of the jet of 0.051″ or greater may result in lower suction flow velocity. In one test with a large d of 0.156″ (equivalent jet diameter) (d/D=0.39), the tool almost lost the ‘pump’ function. It was further noted that the larger the d/D ratio, that is, the ratio of the equivalent diameter of the jet to the inner diameter of the mixing tube, the weaker the sucking force. At low flow rates, conventional and the annular jet pump had higher efficiencies (20 GPM pumping flow rate). It was observed that if the overall size of the jet pump can be increased, the efficiency of the jet pump at higher rig pump rates can be increased due to lower turbulence values and friction losses in the jet pump itself. An advantage of the annular jet pump arrangement is that it will allow for the largest possible jet pump size for a given tool outer diameter due to its unique geometry. 
     Advantageously, embodiments of the present disclosure provide a downhole debris removal tool that includes a jet pump device to create a vacuum to suction fluid and debris from a wellbore. Further, the downhole debris removal tool of the present disclosure produces a venturi effect with maximum efficiency at low pump rates for removing debris from, for example, FIV valves and completion equipment. Additionally, the downhole debris removal tool of the present disclosure may be used in wellbores of varying sizes. That is, the annular size, or annulus space between the casing and the tool, may be insignificant. Embodiments of the present invention provide a downhole debris removal tool that can easily be field redressed and that allows verification of removed debris on the surface. Advantageously, special chemicals do not need to be pumped with the tool and high rig flow rates are not required for optimal clean up. 
     Further, embodiments disclosed herein advantageously provide an isolation valve for a downhole debris removal tool. In particular, an isolation valve in accordance with embodiments disclosed herein provides selective isolation of a debris sub to allow for connections between multiple segments of a debris sub and/or connections between the debris sub and other tools or components to be broken and made up with minimal spillage or leakage of debris and fluids contained within the debris sub. An isolation valve formed in accordance with the present disclosure may provide a safer and cleaner downhole debris removal tool. 
     Furthermore, embodiments disclosed herein advantageously provide a downhole debris removal tool having a drain pin. The drain pin formed in accordance with the present disclosure provides selective fluid communication between the debris sub and the suction tube to allow for fluid contained in the debris sub to be selectively disposed of through the suction tube. Selective disposal of the fluids contained within the debris sub may be performed on a rig floor after the downhole debris removal tool has been removed from the wellbore. Draining fluid from the tool may provide a safer working environment by reducing the risk of fluid spillage when disassembling components of the downhole debris removal tool. 
     Advantageously, embodiments disclosed herein provide a downhole debris removal tool including magnets disclosed on or proximate a screen disposed in the debris sub. Magnets disposed on or proximate the screen may attract metallic debris to the magnet or magnetic surface. Collection of the metallic debris on the magnets may prevent or reduce clogging the screen. Thus, embodiments disclosed herein may provide a more efficient downhole debris removal tool. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.