Patent Publication Number: US-6341653-B1

Title: Junk basket and method of use

Description:
FIELD OF THE INVENTION 
     The present invention relates to apparatus and methods for collecting debris so as to protect a well bore and its contents during well bore operations, such as perforating the well. Particularly, a junk basket is disclosed which is run into the well bore atop a bridge plug. 
     BACKGROUND OF THE INVENTION 
     After casing is placed in a well bore, various operations can be performed. Workover operations, including perforation of the casing produce significant quantities of debris. It is usually desirable to isolate those portions of the well which are not being worked on. Where the unaffected zones are lower in the well bore, a bridge plug is run in and set in position below the intended work zone and above the zone to be protected. A junk basket is subsequently placed on, or above, the bridge plug to collect debris generated from the operation. 
     For instance, in the case where hydraulic fracturing of a formation is performed at an upper set of perforations in the casing, in a first trip, a retrievable bridge plug is set below the upper perforations to block the lower well bore. A setting tool is run in from the surface carrying the bridge plug. An insertion rod associated with the setting tool is attached to, and holds, the plug in position while an outer sleeve of the setting tool imparts a downward force, setting the sealing elements and slips. Then, a link is sheared to separate the insertion rod from the plug. In a second trip, a junk basket is lowered to sit atop the set bridge plug. The workover operation is performed. Frac balls or ball sealers are often used in fracturing so as to gravitate to and temporarily block some perforations for better distribution of fracturing fluid and proppant. Ball sealers must be later removed or they become a significant nuisance. After the workover, in a third trip, a cleanout tool is run into the hole, circulating fluid for washing light debris away from the top of the junk basket and carrying it uphole for removal at the surface. In a fourth trip, a retrieving tool is run in which includes a fish for attaching to the junk basket and fishing it out of the well. 
     The junk basket typically contains debris including particulate matter (sand) and ball sealers. As required for the particular instance, a fifth trip may be expended to retrieve the bridge plug. 
     In summary, without including additional trips resulting from experiencing problems, a least five trips are performed: run in and set the bridge plug; run in junk basket; cleanup well bore to junk basket, retrieve junk basket, retrieve the bridge plug. 
     Each run in operation and trip out costs time and correspondingly, money. Beside the number of trips, several difficulties are associated with the above-described conventional operation. As the diameter of a junk basket is necessarily close to that of the casing to which it is fitted, the sand from the workover tends to pack between the junk basket and the casing, binding and generally making it difficult to pull the basket during retrieval. Additional difficulties are associated with the means for retrieval. As stated, junk baskets fit closely within the well casing. It is known with conventional baskets to use a central and upward projection or fish-neck. To maximize basket capacity, the fish neck diameter is minimized. The retrieval tool must locate and connect to the fish-neck, however it must do so without laterally deflecting it and bending it, which jeopardizes chances of retrieval. Another problem with the conventional baskets is the lack of reliable feedback which enables the operator to ascertain when the fish has actually latched onto the junk basket. Baskets are light and are not normally detected. Many a trip out is performed to find nothing on the end of the retrieving tool, requiring one or more additional fishing trips. 
     For addressing both economics and reliability issues, there is a need for an improved junk-basket and means of installing and retrieving same. 
     SUMMARY OF THE INVENTION 
     A novel junk basket is provided and a method of operation, which in a preferred form, is attached to a bridge plug with shear pins and set simultaneously therewith, thus requiring only a basket/plug setting step, a basket retrieving step shearing the pins, and a plug retrieving step; not the five or more steps of the prior art. Further, the preferred basket maximizes debris capacity, makes fishing retrieval more reliable, latching of the basket is positively identified and the basket is more easily withdrawn from a cased well bore. 
     The preferred apparatus is a basket having a tubular sleeve with a substantially open bore therethrough, the sleeve fitting closely in the casing. The top end of the basket forms a robust internal latch and adjacent the top end are fluid slots to the casing. The basket has a bottom or floor which is movable in the bore but cannot escape the basket&#39;s bottom end. In the well bore, the basket floor is supported by a protuberance such as the bridge plug thereby spacing the floor upwardly in the basket bore. Once filled with debris and latched with a retrieving tool, the junk basket is lifted upwardly from the protuberance causing loss of support for the floor and allowing it to fall to the bottom of the basket where its fall is arrested, but not before the volume within the basket is suddenly increased for the loosening of the collected debris in the basket and loosening of the packed debris between the sleeve and casing through the slots, and thereby aiding in recovery. 
     In a broad apparatus aspect then, a junk basket for collecting debris comprises: 
     a tubular sleeve which fits within a well bore, the sleeve having a bore extending axially therethrough and having top and bottom ends; 
     an internal retrieving latch formed at the top end of the sleeve; 
     a basket floor for substantially blocking the sleeve&#39;s bore and being axially movable therein; 
     an internal shoulder formed within the sleeve&#39;s bottom end for supporting the basket floor preventing its passage downwardly therethrough, the basket floor being operative between at least two positions being, 
     (1) a first collection position wherein basket floor is supported and spaced somewhat upwardly from the sleeve&#39;s bottom end for forming a collection volume for collecting debris, and 
     (2) a second retrieving position wherein the basket floor falls to the internal shoulder when the junk basket is lifted by a retrieving device, thereby increasing the collection volume and whereby the collected debris is loosened within and outside the sleeve permitting ease of retrieving. 
     Preferably the basket floor is supported on a bridge plug anchored in the well bore. More preferably, the sleeve is attached to the bridge plug with shear pins so that, once the retrieving latch is engaged, then at predetermined weight of a retrieving string, the pins shear and the operator is clearly aware the basket was caught and will be retrieved. 
     More preferably, the basket floor is formed with an axial port so an insertion rod can be connected to the bridge plug through the floor, the basket thereby being capable of being run in with the bridge plug and does not interfere with the setting of the plug. Provision for axial slots through the sleeve permits fluid communication with the casing annulus which can aid in the retrieval process. 
     The above apparatus enables a novel method of setting and retrieving a bridge plug and junk basket simultaneously. 
     In a broad method aspect then, a downhole tool, such as a bridge plug is deployed simultaneously with a junk basket using a setting tool and insertion rod, the downhole tool having a top protuberance comprising the steps of: 
     connecting a junk basket to the top of the downhole tool, the junk basket having a tubular sleeve with top and bottom ends, an open bore extending axially through from the top end through to the bottom end, and having a basket floor which blocks the sleeve&#39;s bore, the insertion rod passing through the sleeve&#39;s bore and to an axial port in the basket floor, and a ball which is movable within the sleeve&#39;s bore and is capable of blocking the axial port; 
     releasably connecting the insertion rod to a rod connection at the top protuberance through the sleeve&#39;s bore; 
     inserting the insertion rod, junk basket and downhole tool into the well bore; 
     setting the downhole tool to anchor it within the well bore; and 
     releasing the insertion rod from the rod connection so that the junk basket remains in the well bore above the downhole tool and the ball is able to block the axial port. 
     Preferably, the sleeve has one or more fluid ports for communication between its bore and the well bore and basket floor is movable within the sleeve&#39;s bore and initially spaced upwardly by the protuberance so that when the basket is retrieved, the ball is blocking the axial port and the floor drops, increasing the basket volume and loosening debris within and outside the basket. More preferably, the basket&#39;s sleeve is attached to the downhole tool with shear pins for enabling confirmation of the latching of a retrieval tool and thus completing the method for deploying, collecting debris and retrieving the debris. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional, axially compressed view of a junk basket according to one embodiment of the present invention; 
     FIGS. 2 a - 2   b  are cross-sectional views of the junk basket accordingly to FIG. 1, with and without the setting tool assembly. More specifically: 
     FIG. 2 a  illustrates setting the bridge plug and junk basket, using the junk basket as a setting sleeve; 
     FIG. 2 b  illustrates the junk basket on the bridge plug after removal of the setting tool; 
     FIG. 3 a  is a cross-sectional view illustrating the collection of debris in the junk basket, including ball sealers, the bridge plug detail is omitted to clarify the junk basket components; 
     FIG. 3 b  is a close-up of the slot area according to FIG. 3 a  illustrating packing of sand between the sleeve and casing; 
     FIG. 4 a  is a cross-sectional view illustrating a retrieval tool inserted into a well bore, just above the junk basket (no debris is shown); 
     FIG. 4 b  is a cross-sectional view illustrating the retrieval tool with the mandrel engaging the shoulders of the junk basket while collapsing the latch fingers radially inwardly, before actually latching (no debris is shown); 
     FIGS. 5 a - 5   c  are detail partial views of the latching of the retrieving tool with the top sub before, after setting down with tubing weight and during lifting respectively; 
     FIG. 6 is a cross-sectional view illustrating a debris-filled junk basket with the basket&#39;s ball in place in the basket floor&#39;s port. Cleanout fluid flow is shown lifting fine debris upwardly past the retrieving tool&#39;s lower centralizer; 
     FIG. 7 a  is a cross-sectional view illustrating the retrieval tool positively engaged with the junk basket having upward facing, outside shoulders of the latch finger&#39;s shoulders catching inside shoulders of the basket&#39;s top sub (no debris is shown); 
     FIG. 7 b  is a cross-sectional view illustrating commencement of retrieval by shearing of the junk basket from the bridge plug, dropping the basket floor of the basket for rapid loosening of the debris therein and packed therearound (no debris is shown); 
     FIG. 8 is a cross-sectional view illustrating the loosened, yet still debris-filled junk basket after shearing from the bridge plug and in the process of being retrieved from the well bore; 
     FIG. 9 a  is a cross-sectional view of the retrieval device complete with upper and lower centralizer subs, a cleanout nozzle and collet supporting latch fingers; 
     FIG. 9 b  is a cross-sectional view along section lines B—B of FIG. 9 a  illustrating the hollow mandrel having a fluid bore and annular cleanout passages; 
     FIG. 9 c  is a cross-sectional view along section lines C—C of FIG. 9 a  illustrating the individual finger latches of the collet; and 
     FIG. 9 d  is a partial cross-sectional view of the tip of a finger latch. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Having reference to FIGS. 1 and 2 a , a well bore  10  is shown which is going to have some sort of workover performed intermediate along the well bore. The well bore  10  has a casing  11 , a bridge plug  50  (FIG. 2A) and a junk basket  12  installed for collecting debris above the plug  50 . The term “well bore” is sometimes used herein as a more general term for the bore of the casing  11 . The preferred embodiment is described in the context of a workover comprising a hydraulic fracturing operation which utilizes ball sealers. The presence of ball sealers is instructive in illustrating the ability of the invention to deal with a variety of debris. Applicant is not restricting use of the invention to fracturing operations, but the operation is merely used for best illustrating the present invention. 
     The junk basket  12  is positioned above the bridge plug  50  using a process described later. The basket  12  comprises a cylindrical sleeve  13  having a top end  14   a  and a bottom end  15   a . The sleeve  13  fits closely within the casing  11 , forming a narrow casing/sleeve annulus  16 . A top sub  14   b  is threaded onto the sleeve&#39;s top end  14   a  and a bottom sub  15   b  is threaded onto the sleeve&#39;s bottom end  15   a . A contiguous bore  19  extends through the top sub  14   b , sleeve  13  and bottom sub  15   b.    
     At the top of the sleeve  13 , adjacent to the top sub  14   b , axial slots  29  (four shown) are provided for permitting fluid communication between the sleeve&#39;s bore  19  and the casing annulus  16 . The slots are sized to permit fluid communication but exclude large debris. 
     The basket  12  has a movable floor  20  preferably formed of a funnel-shaped body which fits closely within the sleeve&#39;s bore  19 . The basket floor  20  is axially slidable within the bore  19  for varying the volume V within the bore  19  of the sleeve  13 . An internal upset within the bottom sub  15   b  forms an inward internal shoulder  21  which projects sufficiently into the sleeve&#39;s bore.  19  to prevent exit of the basket floor  20 . In FIG. 1, the basket floor  20  is shown resting on the bottom sub&#39;s internal shoulder  21 . In FIG. 2 a , the basket floor  20  is shown spaced upwardly intermediate the sleeve&#39;s bore. 
     The basket floor  20  has an axial, centralized port  25  and ball seat  26 . A ball  27  is provided which is movable within the sleeve&#39;s bore  19  and which is operative to seat on the ball seat  26  and block the axial port  25 . The ball  27  is only operative at a defined point in the operation of the junk basket as described in greater detail later. 
     The top sub  14   b  (FIG. 1) is adapted for engaging a retrieving tool  70  (FIGS. 9 a - 9   d ). The retrieving tool  70  is provided for the eventual retrieval of the junk basket  12  (See sequential FIGS. 4 a ,  4   b ,  7   a  and  7   b ). 
     Referring then to FIGS. 1,  5   a - 5   c , and  9   d , the top sub  14   b  and retrieving tool  70  have complementary latching shoulders  32 ,  132 . For enabling the engagement of the retrieving tool  70 , the top sub  14   b  comprises a wide mouth  19   a . Downhole from the mouth  19   a , the top sub&#39;s bore  19  progressively narrows for forming an internal shoulder  31 . The uphole end of the shoulder  31  forms a ramp  33  for guiding and easing the entry of the complementary retrieving tool  70 . A bottom face of the shoulder  31  is angled perpendicularly for forming the top sub&#39;s internal latch  32 . 
     As an assembly, the sleeve  13 , bottom sub  15   b , basket floor  20  and ball  27  form the volume V for the collection of debris. 
     Accordingly, referring to FIGS. 2 a ,  2   b , the junk basket  12  is supported in the well bore  10  by the bridge plug  50 . The bridge plug  50  is utilized to separate the well bore into a lower isolated zone and an upper working zone. Preferably the bridge plug is retrievable, providing maximum flexibility in the resumption of well operations after the workover. The bridge plug  50  is anchored in the well bore  10  and actuated for sealing the casing  11 . Besides anchoring slips and sealing elements (not shown), the plug  50  comprises a mandrel  51  having an axially extending protuberance  52  which incorporates a central shear stud  53  having a weakened neck portion  54 . Positioned near the top of the plug&#39;s mandrel  51  are laterally projecting setting and retrieving load-bearing lugs  55 . 
     The junk basket  12  is connected to the plug&#39;s top protuberance  52 . The bridge plug&#39;s top protuberance  52  extends into the bore  19  of the bottom sub  15   b  until the bottom sub bears against the retrieval lugs  55 . The bottom sub  15   b  is retained to the bridge plug using two brass set shear pins  59  having a known shear load—typically 1000 lbs. each. To decouple the basket  12  and plug  50 , the basket  12  is loaded in tension relative to the anchored plug  50  until the brass pins  59  shear. 
     When coupled, the basket floor  20  rests against the plug&#39;s protuberance  52  under its own weight. The protuberance  52  causes the floor to be spaced upwardly in the sleeve&#39;s bore  19 , above the top protuberance  52 . The axial port  25  in the floor  20  is sized to accept and pass the plug&#39;s shear stud  53  therethrough. 
     The structure of the junk basket  12  enables unique setting, debris collection and retrieval. 
     Setting Tool Assembly 
     Best seen in FIG. 2 a , a setting tool assembly  60  is provided comprising both a setting tool  61  and a slender insertion rod  62 . The setting tool assembly  60  is used for conveying the bridge plug  50  into the well bore  10  and then setting or deploying it in the casing  11 . The assembly  60  is typically connected to the end of coiled tubing or electric wireline (neither shown) which is run in the well bore  10 . The assembly&#39;s insertion rod  62  is positioned at the lower end of the setting tool assembly  60  and projects through the bore  19  of the junk basket&#39;s top sub  14   b  and through the sleeve  13  to connect to a rod connection of the plug, such as the shear stud  53 , typically by threaded connection. 
     An annular space  64  is formed in the sleeve&#39;s bore  19  between the insertion rod  62  and the sleeve  13 . The ball  27  is movable within the annular space  64 . The ball  27  cannot achieve a central position over the axial port  26  of the basket floor  20  due to the presence of the assembly&#39;s insertion rod  62 . 
     The setting tool  61  causes the basket&#39;s sleeve  13  and bottom sub  15   b  to bear down on the plug&#39;s lateral lugs  55 , setting the plug&#39;s anchoring slips and sealing the plug  50  in the casing  11 . During setting of the plug, the insertion rod  62  remains fixed to the setting tool  61 , resulting in relative movement between the insertion rod  62  and the lateral lugs  55 . 
     Once the plug  50  is set, further downward load on the basket causes an ever increasing tensile load on the insertion rod  62  until the stud  53  shears and separates at the neck  54  into an upper portion  53   a  above the neck for removal from the well bore  10  with the insertion rod and a lower portion  53   b  which remains with the plug  50 . The top protuberance  52  continues to support the basket floor  20  even after the stud  53  is sheared. Means for actuating the relative movement of the setting tool  61  and insertion rod  62  are known in the art and have not been described in detail. 
     Retrieving Tool 
     The retrieving tool  70  is connected to the bottom of a coil tubing string (not shown) which is run into the well bore  10  for engaging and retrieving the junk basket  12 . 
     As detailed in FIGS. 9 a - 9   d , the retrieving tool  70  comprises a hollow mandrel  71  comprising a fluid bore  72 , a cleanout nozzle  73 , finger latches  74 , a lower centralizer  75 , an upper centralizer  76 , and lift jets  77 . Typically, air is used as the cleanout fluid. The fluid bore  72  conducts sufficient air flow for discharge from the nozzle  73  to fluidize, elutriate and carry light or fine debris, such as sand, up the casing  11  for removal from the well bore  10  at the surface. As shown in FIG. 9 b , the upper and lower centralizers have axial ports  79  formed about their periphery for passing the cleanout fluid and debris up the well bore  10  The lift jets  77  are directed upwardly and outwardly to aid in lifting debris up the well bore  10 . 
     The mandrel  71  is an assembly having a top centralizer sub  80  and a lower centralizer sub  81 . The top centralizer sub  80  has an upper threaded socket for connection to tubing string and a lower male pin end  83   a . The upper centralizer  76  is formed onto the top centralizer sub  80 . The lower centralizer sub  75  has a female socket  83   b  for accepting the top centralizer sub&#39;s male in end  83   a . A ring seal  84  seals the pin end  83   a  and socket  83   b  with shear screws  85  retaining them together. The shear screws  85  provide a safety disconnect and shear at loads greater than the anticipated working loads and those necessary to shear the sleeve-to-plug pins  59 , typically about 10,000-15,000 lb. force. 
     The bottom end  86   a  of the lower centralizer sub  81  is threaded for adapting to a complementary threaded male connection  86   b  on the cleanout nozzle  73 . 
     Best seen in FIGS. 9 a  and  9   c , the finger latches  74  are formed by a collet  87  comprising a ring collar  88  having a plurality of independent longitudinally extending finger latches  74 . The ring collar  88  fits slidably over the lower centralizer sub  81  forming a latch deflection annulus  89  therebetween. The deflection annulus  89  has sufficient clearance to permit tips  90  of the finger latches to be deflected radially inwardly by the basket&#39;s top sub shoulder  31 , bending elastically at the collar  88 . 
     As detailed in FIG. 9 d , the profile of the finger latches  74  is complementary to that of the basket&#39;s top sub  14   b . Each finger has an outward facing latch  91  formed at its tip  90 . The tip  90  of each finger  74  thickens upwardly and ramps radially outwardly, forming an outward facing ramp  92  and shoulder  93 . At the upper end of the shoulder  93 , a top face  132  is angled perpendicularly inward for complementary latching with the top sub latch  32 . 
     The greatest radial extent of the shoulder  93  in the undeflected state is about that of the bore of the basket&#39;s top sub below the top sub shoulder  31 . When engaged, the top face  132  of the finger latches  74  positively engage the internal latch  32  of the top sub  14   b.    
     The lower centralizer  75  and latch collet are fitted over the lower centralizer sub  81  before connection of the cleanout nozzle  73 . When the cleanout nozzle  73  is threaded into the bottom of the hollow mandrel  71 , it retains the lower centralizer and collet  87  onto the mandrel  71 . 
     The cleanout nozzle  73  comprises two jets which are contiguous with the fluid bore. The nozzle&#39;s jets are directed generally downwardly for engaging and loosening debris. Provision of two or more jets avoids complete loss of circulation of one jet becomes blocked. 
     The operation of the junk basket  12  can be described as having three basic stages; running in, collection of debris, and retrieval. These three operations are accomplished in only two trips. 
     Running In 
     To run in the basket  12 , it is first assembled with the bridge plug  50 , the result being illustrated in FIG. 2 a . The basket  12  and plug  50 , the bottom sub  15   b  is inserted over the plug&#39;s protuberance  52 . Tangs (not shown) depending from the bottom of the bottom sub engage the lugs  55 . The shear stud  53  is installed into the plug&#39;s protuberance  52 . The basket floor  20  is placed over the shear stud  53 . The setting tool assembly&#39;s insertion rod  62  is threaded onto the shear stud  53 . The sleeve  13  is threaded into the bottom sub  15   b . The ball  27  is inserted into the annulus  64  between the insertion rod  62  and the sleeve  13 . The top sub  14   b  is threaded onto the sleeve  13 . The setting tool  61  is threaded onto the insertion rod  62 . An adjustment on the setting tool  61  takes up slack between the setting tool  61 , the sleeve  13 , bottom sub  15   b  and the plug&#39;s lugs  55 . When the top sub  14   b , sleeve  13  and bottom sub&#39;s tangs (not shown) are sandwiched tight between the setting tool  61  and the plug  50 , the brass shear screws  59  are installed into the sleeve&#39;s bottom sub  15   b.    
     The junk basket  12 , bridge plug  50  and setting tool assembly  60  are attached to lowering means such as a tubing string (not shown). The tubing string is inserted into the well bore  10  to the desired setting depth (FIG. 2 a ). The setting tool  61  is actuated for setting or anchoring the plug  50  in the well bore  10  by imparting opposing forces on the plug  50  and shear stud  53 , downward through the basket  12  against the plug&#39;s setting lugs  55  and through the shear stud  53 . Once set, the stud  53  is sheared for separating the insertion rod  62  from the plug  50 . 
     The setting tool  61  and insertion rod  62  are removed from the well bore  10 , leaving the basket  12  and bridge plug  50  in the well bore  10  (FIG. 2 b ). The sleeve&#39;s bore  19  is wide open for accepting debris  100  with the basket floor  20  spaced somewhat upwards from the bottom of the basket  12  by the plug&#39;s top protuberance  52 . 
     Collection of Debris 
     As shown in FIG. 3 a , during a workover, debris  100  falls through the basket&#39;s top sub  14   b , into its bore  19  and enters the basket&#39;s collection volume V. The sleeve  13  fits quite closely to the well bore casing  11  and thus most debris  100  enters the basket  12 . The debris includes fines, like sand, and larger debris, like ball sealers  101 . As shown in FIG. 3 b , sand can settle in the very small annulus  102  formed between the sleeve  13  and the well bore  10 . 
     The amount of debris  100  usually exceeds the volume of the collection volume V, filling it to above the top sub  14   b  and continuing to pack in the well bore  10  thereabove. 
     Retrieving 
     Having reference to FIGS. 4 a - 6 , in order to engage and latch the retrieving tool  70  into the basket&#39;s top sub  14   b , some of the debris  100  which has accumulated on top of the basket  12 —such as packed sand—must be cleared both from above and within the upper portion of the top sub  14   b  of the junk basket  12 . Accordingly, the retrieving tool  70  is run into the well bore  10  on a tubing string. 
     Having reference to FIGS. 4 a ,  6  cleanout fluid F is pumped down to the retrieving tool  70  and nozzle  73  for fluidizing lighter gravity debris  100  that may be in the well bore  10  and basket. FIG. 6 illustrates the conclusion of the debris cleaning operation. The velocity and viscosity of the fluid F is sufficient to carry the lighter debris  100  up the well bore  10 , past the retrieving tool, through the centralizer ports  79  and to the surface. Some fluid F will pass through axial slots and up the casing annulus  16  and around the top sub  14   b.    
     Heavier components of the debris  100 , like solid ball sealers  101 , are too heavy to be fluid lifted to the surface nor can they pass through axial slots  29 , nor past the lower centralizer, and thus concentrate in the collection volume V of the basket  12 . 
     Having reference more specifically to FIGS. 5 a - 5   c  and  9   d , as the retrieving tool  70  reaches the top sub  14   b , the ramp  92  of the tapered fingers  74  contact the inside ramp  33  of the top sub  14   b  (FIG. 5 a ). Set down weight on the retrieving tool  70  causes the ramps  92  of the latch fingers  74  to ride on the top sub ramp  33 , collapsing the finger latches radially inwardly, allowing the latch fingers  74  to slide into the top sub  14   b  until the upward facing, outward facing latch  132  of the latch fingers pass the downward facing inside shoulder  31  of the top sub  14   b . The lower centralizer  75  is seen to contact the top sub, arresting the retrieving tool (FIG. 5 b ). The finger latches  74  expand inside the top sub  14   b  and when the retrieving tool is again lifted (FIG. 5 c ), the outside shoulders  132  of the finger latch  74  catch the top sub&#39;s inside shoulder  32 , positively engaging the retrieving tool  70  to the basket&#39;s top sub  14   b . The latched condition is shown in FIG.  6 . 
     At any time thereafter, once an operator believes the retrieving tool  70  has reached the top sub  14   b , the operator can positively determine whether the tool  70  has latched the top sub  14   b  and a trip out will yield the junk basket  12 . The operator pulls up on the retrieving tool  70 , by pulling up on the tubing string. The operator observes the pull force and compares that against the weight of the tubing string. If the pull force climbs significantly, approaching. 2000 lbs. over the weight of the tubing, then it is understood that the combination retrieving tool  70  must have latched onto the junk basket  12 . If the operator continues to pull up on the tubing string to approx. 2000 lbs., and then the pull force drops sharply to that of the tubing weight alone, the operator has then confirmed that the junk basket  12  is latched and that the brass screws  59  have sheared, separating the basket  12  from the bridge plug  50  as shown in FIGS. 7 b  and  8 . 
     As shown in FIG. 8, one of the significant features of the novel junk basket  12  is demonstrated when the brass screws  59  are sheared. Once sheared, the retrieving tool  70  and latched junk basket immediately and quickly lift free of the bridge plug. This lifting action quickly spaces the basket  12  from the plug  50  and removes support from the basket floor  20 . Accordingly, the basket floor  20  falls abruptly to the bottom sub&#39;s inner shoulder  21  resulting in a sharp increase in the collection volume V. This increase in the collection volume V causes the packed debris  100  to loosen as it expands to fill the greater volume. Surprisingly, the basket is then much easier to retrieve. It is postulated that fine debris, like packed sand, has been loosened in the annulus  102  between the sleeve  13  and the casing  11 . While the exact mechanism is not clear, it may be that the falling of the floor acts as a jar, or possible that the sudden increase in volume creates a localized pressure differential and resulting fluid flow between the basket&#39;s bore  19  and the basket/casing annulus  102  which appears to loosen the grip any packed sand in the annulus  102 . Having loosened the basket  12  in the casing  11 , the basket  12  is more readily retrieved without binding. 
     Lastly, the retrieving tool  70  and junk basket  12  are pulled out of the well bore  10 . 
     To complete the practical aspect of completing the task, the disassembly of the retrieving tool  70  from the junk basket  12  is described as follows. The basket&#39;s top sub  14   b  is unscrewed from the sleeve  13 . The nozzle  73  is unscrewed from the retrieving tool  70  and the remainder of the retrieving tool  81 , 80  is slid out of the top sub  14   b . The collet  87  is removed through the bottom end of the top sub  14   b . Lastly, the ball  27  and basket floor  20  are removed from the inside of the sleeve  13 , and the connection between the sleeve  13  and bottom sub  15   b  is unscrewed.