Patent Publication Number: US-8978752-B2

Title: Electric submersible pump band basket catcher

Description:
RELATED APPLICATIONS 
     This application hereby claims the priority filing date of and incorporates by reference U.S. provisional patent application 61/313,425, filed Mar. 12, 2010, entitled Electric Submersible Pump Band Basket Catcher, inventors Gary Erickson and Ronald Dobson. 
    
    
     COPYRIGHT NOTICE 
     A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     FIELD OF THE INVENTION 
     This invention relates to petroleum extraction and more particularly to a method and apparatus for clearing the borehole of an oil well bore. 
     BACKGROUND OF THE INVENTION 
     Referring now to the figures, in many environments crude oil is produced by boring a shaft or borehole  10  into the ground down to a natural reservoir of oil  11  and then inserting a pump into the borehole and pumping the oil out of that reservoir. 
     The borehole  10  is drilled and then lined with a tubular metal casing  12 . The casing  12  is made up of lengths of casing pipe coupled together to form one continuous pipe with a central bore. Each length of casing is in the range of about forty-four feet long and has male threads at both ends, joined together with female-female threaded collars  16  to form the continuous tube with an interior bore. A collar  16  generally is a short length of pipe with female threads on either end that acts as a coupling to join two lengths of pipe, here casing  12  pipe having male threads at each end. When the male threads of two casing pipes are inserted into a collar there is a short gap within the collar between the ends of adjoining lengths of casing pipe. 
     Oil reservoirs  11  may be relatively deep, perhaps 6,500-11,000 feet deep, and the borehole may need to be drilled through several zones of different material found at lesser depths, such as an aquifer that might be found at a relatively shallow 1,500 feet or less below the surface. In addition to the casing  12  of the borehole  10 , cement may be poured around the outside of the casing to seal the walls of the borehole from the surrounding material. This seal is created both to prevent oil leakage out of the borehole and fluid leakage into the borehole from the various surrounding zones of material. This seal may be critical in order to prevent the oil from leaking out of the borehole and contaminating a surrounding aquifer that the borehole passes through. 
     At the terminal or bottom end of the casing  12 , where the borehole  10  intrudes into an oil reservoir or oil sands zone  11 , a final section of liner  14  pipe is placed and hung with liner hanger to the end of the casing, forming a single continuous bore through the casing and liner pipe. 
     A joint  18  refers generally to a single length of pipe, for example liner, casing, or tubing that has threaded connections at both ends. Joints  18  are made in standard lengths depending on the type of pipe. Several joints  18  coupled together are called a stand of pipe and a string of pipe refers to the entire length of all the joints of pipe or tube used in the length of the borehole. A pup joint  20  is a joint of less than standard length. The shorter lengths of pup joint production tubing are used to adjust the total length of a stand or string should the desired length be less than exactly a multiple of the standard lengths, to add a length of pipe of less than a whole standard length to more precisely size the total length of the string. 
     Typically the liner  14  pipe used has a narrower internal diameter than that of the casing pipe it is used with, for example a typical industry standard uses a casing  12  having an internal diameter of 8⅝ inch and is used with a liner pipe having a narrower 6⅝ inch internal diameter. The liner  14  pipe is also different from the casing  12  in that the liner is not sealed from the surrounding material and is instead perforated with voids or slots  14 A. The liner  14  is inserted into an oil reservoir or oil sands zone  11  and allows oil from the reservoir or reservoir sands  11  to seep through the perforations  14 A into the liner. The voids  14 A of the liner  14  may be slots that are small enough to keep most surrounding sand out of the liner while allowing the crude oil to seep into the liner. 
     An electric submersible pump  22  comprised of various components including an impeller and electric motor is lowered into the casing and is hung atop the opening of the liner  14  pipe. The electric motor portion of the pump  23  is usually located at the bottom of the submersible pump  22  and is sized to fit within the casing  12 . 
     The electric pump  22  has couplings or flanges at each end to allow several pumps to be connected in series as a single pump and the pump sucks liquid that&#39;s entered from the liner  14  section at the lower end, the intake opening  22 A and expels it through the second upper opening at the top of the pump, the exhaust opening  22 B, at the opposite end of the pump. Production tubing or line  24  is affixed to the exhaust opening  22 B to achieve liquid communication with the pump. The production tubing  24  connected to the pump  22  runs from the pump to the surface within the length of the casing  12 . The electric pump  22  and production tubing  24  together form a single liquid conduit through which oil is pumped from the liner  14  through the production tubing to the surface. 
     The motor  23  of the electric pump  22  is sized to fit snugly within the casing and therefore has an outside diameter larger than that of the liner  14  section, preventing the electric pump motor from entering the liner section. In cases where the diameter of the pump motor may be less that of the liner, the pump may include a No-Go  26 , which are flanges or protuberances or wings  26 A affixed to and protruding from the electric pump or other tools that are lowered into the casing. The No-Go  26  functions to maintain a sufficient outside diameter so as to interfere with the internal diameter of the liner pipe  14  section, thereby preventing that pump or tool from entering the liner section. 
     The production tubing  24  is usually of substantially smaller outside diameter than the casing  12  internal diameter that it is placed in. In the example used the production tubing  24  may have an outside diameter of 2⅞ inches. As with the casing pipe  12 , each joint of the production tubing  24 , including pup joints  20 , has two male ends. A collar  16  is used to connect two joints together to form a stand or string of production tubing  24 . Production tubing  24  joints are joined together with production tubing collars  16  to form a string of production tubing connected to the electric pump  22  and traversing the length of the casing. 
     The electric pump motor  23  requires an electric power supply to operate and therefore an electric cable  28  of about 1¼ inches in diameter is plugged into the pump motor  23 . Flat cable is plugged into the pump directly, runs up the productions line  24  for a joint or two, then the 1¼ cable is used, which runs the length of the production tubing to a power source located on the surface. Metal bands  30  are installed around the production tubing  24  and electric cable  30  at intervals to hold them together to prevent the electrical cable from becoming entwined, jammed or knotted up when the production tube is inserted or withdrawn from the casing  12 . The bands  30  are typically metal strapping affixed around the electric cable and crimped together with a saddle fastener (not shown). The pump uses a flat special banding, flat guards banding to band the flat cable to the pump. 
     The bands  30  are affixed around the production tubing  24  and electrical cable  28 , and, around the electric pump  22  and electric cable  28  as the stand of pipe is assembled and lowered into the casing  12 . The bands  30  are typically placed on either side of the production tubing collars  24 A as joints are added. A count is kept of the number of bands affixed to the production tubing determine how many may be missing when the string is eventually removed from the casing  12 . 
     A problem arises as the string of production tubing  24  and pump  22  is withdrawn from the casing, for example to service the electric pump. The bands  30  may rub against the interior wall of the casing  12  or snag on the gaps in the casing collars and then the bands sometimes break and fall off into the casing. The broken bands  30  may occlude the casing  12 , jamming the casing and making it difficult to reinsert the electric pump  22  and string of production tubing  24  for example. 
     This band debris problem is especially acute in a deviated drill borehole where the borehole was drilled with a deviation from vertical. Many or most modern oil well boreholes are not vertical shafts, they bend at several junctures and some run horizontally for great distances. The act of withdrawing the pump from a casing that is not oriented vertically exacerbates the damage to the bands because the weight of the production tubing make it more likely that the bands will rub against or be dragged along the interior of the casing, breaking the bands. 
     This problem is addressed by clean-out procedures. The number of bands  30  affixed to a production tubing  24  string are counted when the production tubing is inserted and, should there be bands missing after the production tube string is withdrawn from the casing  12 , the casing must be cleaned out. The broken bands usually have to be extracted from the casing before the pump can be again placed in the casing. The present methods of cleaning out an oil well casing of broken bands and other debris are expensive, laborious and very time-consuming, keeping the oil well out production during the cleanout procedure. 
     If there are bands missing from those counted after the production line is withdrawn a two-stage cleanout operation typically is performed. In the first stage of the cleanout operation a surge tool  32  is inserted down the length of the bore. A surge tool  32  has a rubber packoff cup  32 A that is sized to snugly fit within the inside diameter of the casing  12  to form a seal. The surge tool  32  has a central opening with a junk catcher  34  mounted within the central opening to create a one-way trap for debris to pass through as the surge tool is inserted. The junk catcher includes a radial array of fingers  34 A that are spring-biased to bend into the surge tool only, to allow debris to pass into the body of the surge tool, then snap closed to retain the debris. The surge tool  32  is affixed to a length of perforated pup joint  32 B at the end opposite the junk catcher and the pup joint is also attached to the production tubing string. As the surge tool  32  is inserted into the casing  12  most liquid and debris in the casing will be forced through and be trapped by the junk catcher  34  within the surge tool. As the surge tool is withdrawn the pup joint perforations allow liquid to still pass even when the debris trapped by the junk catcher clogs the bottom of the surge tool. 
     The surge tool  32  is lowered into the casing the entire length by affixing successive lengths of production tubing  24 , then withdrawn. The debris and broken bands are thereby trapped within the surge tool  32  as it is inserted and are collected for disposal as the surge tool is pulled to the surface. 
     This first surge tool operation is time consuming and may take four to six hours to complete. 
     After the surge tool operation has been completed a second cleanup operation is conducted to pulverize any remaining contaminants, bands or other debris still in the casing and missed by the surge tool operation. In the second stage of the cleanout operation a grinding head  36  is inserted down the length of the bore. Like the surge tool  32  the grinding head  36  also has a central opening with a junk catcher  34  mounted within the central opening to create a one-way gate for debris to pass through as the surge tool is inserted. The outer edge of the grinding head  36  surrounding the junk catcher  24  is comprised of a rough material made of a hard metal such as tungsten-carbide. The grinding tool is affixed to production tubing  24  and lowered the length of the casing  12 . As the grinding head  36  encounters debris or broken bands it grinds them up and the ground-up debris is forced through the junk catcher  34 , to be withdrawn later with the grinding head for disposal. This second separate operation is also time-consuming and may take another four to six hours or longer to complete. 
     What is needed then is a device and method for more easily and reliably removing any broken bands, reducing the need for these cleanup operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section diagram of the components of an oil well bore. 
         FIG. 2  is a cross-section diagram of the components of tools of the prior art used to clean out the casing of an oil well. 
         FIG. 3  is a perspective view of the basket catcher of the present invention. 
         FIG. 4  is a top and side schematic view of the collar fabrication details of the basket catcher of the present invention. 
         FIG. 5  a cross-section diagram of the present invention in use with components of the prior art in one configuration. 
         FIG. 6  a cross-section diagram of the present invention in use with components of the prior art in another configuration. 
         FIG. 7  a cross-section diagram of the present invention in use with components of the prior art in yet another configuration. 
     
    
    
     SUMMARY OF THE INVENTION 
     A solution to the above has been devised. A band basket catcher is placed above or below the submersible pump to collect or scavenge broken bands as the production tubing and pump are withdrawn from the casing. The basket catcher is made from a collar that includes a series of spring-tensioned blades arranged radially and directed upwardly that, when dragged through the casing, catches and retains any broken bands or other debris as the production tubing and pump are removed from the casing. The blades together form a basket structure to catch broken bands  30  during pump withdrawal. The band basket catcher thereby minimizes or eliminates the need for cleanout operations because it catches any broken bands as the pump itself is withdrawn. 
     In the preferred embodiment the basket catcher is fabricated with eight blades from a collar base of the same diameter pipe that is being used for the production tubing so that it can be affixed either to the production tubing itself or to the pump with a pup joint. Eight voids are first milled in the end of a collar at regularly spaced intervals about the collar, at forty-five degree intervals for eight blades for example. Each milled void is formed to receive an end of a blade and the individual blades are welded into each void. The blades are formed to radiate outwardly from the collar and are of sufficient length to cause the blades to contact the interior wall of a given casing. The dimensions of the blades to be formed vary depending on the internal diameter of a given casing for which the basket is intended to be used with. In all cases the blades should be sized to be long enough and radiate outwardly enough so that the outside of the blades contact the interior wall with spring tension against the surrounding casing, and further curve inwardly at the ends distal the collar. The inward curve is provided so that the ends do not catch on any collars connecting casings together. 
     In this manner the spring tensioning of the blades also allows the basket catcher to continue maintaining contact with he interior casing wall should the internal diameter vary by use of stands of casing of different diameter in the string of casing. As the basket catcher is moved from a casing of one internal diameter to a casing of a different internal diameter the basket catcher blades will retract or expand under their spring bias to maintain contact with the wall of the casing. 
     It is preferred that the basket catcher be affixed below a submersible pump, below the lowest bands and flat guards that are at risk of loss, with a length of perforated pup joint to serve the dual functions of connecting the basket catcher to the pump and of also creating a storage space to collect any broken bands and other debris collected as it is removed from the casing. A No-Go  26  created on the basket catcher can prevent the basket catcher from slipping into a liner section. 
     Multiple basket catchers can be used in combination with a single production tube, placing them for example above and below the pump or along the production line, as desired, to effect multiple cleanings of a casing. 
     A Y-Tool may be used with the basket catcher of the present invention. A Y-Tool allows a second tool to be affixed to the production tubing along with the pump. For example a Y-tool may be affixed to the end of the production tubing and the Y-Tool is also connected to both a submersible pump an instrument monitoring tube or other equipment that might need to extend further toward the liner, past the basket catcher. One or more of the eight blades can be formed or omitted to leave an opening for that instrument tube to extend through and past the basket catcher. 
     The method of the present invention is straightforward. One or more basket catchers are affixed to a production string or pump of the production string prior to inserting the production string into the casing. When the production string is withdrawn debris caught by the one or more basket catchers is removed and disposed of after removal. 
     DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENT 
     A band basket catcher  40  is placed above or below the submersible pump  22  to collect or scavenge broken bands as the production tubing  24  and pump  22  is withdrawn from the casing  12 . The basket catcher  40  is made from a collar  40 A used as a base that is modified to include a series of spring-tensioned blades  40 B arranged radially and directed upwardly that, when dragged through the casing  12  catches and retains any broken bands  30  or other debris as the production tubing  24  and pump  22  are removed from the casing. The band basket catcher  40  thereby minimizes or eliminates the need for cleanout operations because it catches any broken bands as the pump is withdrawn. 
     The blades  40 B together form a basket structure to catch broken bands  30  during pump withdrawal. Blades  40 B are used in this embodiment but such a basket could conceivably be formed from structures other than the blades of the preferred embodiment and the scope of this disclosure is intended to also encompass those equivalent structures that perform the same function. 
     This description, and the figures to which it refers, are provided for the purpose of describing examples and specific embodiments of the invention only and are not intended to exhaustively describe all possible examples and embodiments of the invention. 
     The basket catcher  40  of the presently-preferred is fabricated from a collar base  40 A for use with the same diameter pipe that is being used for the production tubing  24  so that it can be affixed either to the production tubing or to the pump  22  with a pup joint  20 . In the preferred embodiment the band basket catcher  40  is fabricated with eight blades  40 B. Eight voids  40 C are first milled in the end of a collar  40 A, regularly spaced about the collar, here at forty-five degree intervals for eight blades. Each milled void  40 C is formed to receive an end of a blade and the individual blades  40 B are welded into each void. Eight blades  40 B have been found to be sufficient to create enough of a basket to catch loose bands and other debris, while still allowing liquid to pass by the basket as it is withdrawn from the casing. 
     The blades  40 B are formed to radiate outwardly from the collar and are of sufficient length to cause the blades to contact the interior wall of a given casing. The dimensions of the blades  40 B to be formed varies depending on the internal diameter of a given casing  12 , but they are typically about two inches wide and twelve inches in length, and formed to radiate away from the collar at about a forty-five degree angle. In the typical example when the band basket catcher  40  is fabricated it is about seventeen inches in overall height, initially with straight twelve-inch blades  40 B, then the blades are bent inwardly at  40 D, for an overall height of the blades of about nine inches. In all cases the blades  40 B should be sized to be long enough and radiate outwardly enough so that the outside of the blades contact the interior wall with spring tension against the surrounding casing  12 , then curve inwardly at the ends distal the collar  40 A, at  40 D. 
     The blades  40 B are heat-tempered to make them flexible to maintain a spring-biased tension against the interior wall of the casing  12 . This prevents broken bands from slipping past the basket catcher  40 . The spring tensioning of the blades  40 B also allows the basket catcher to continue maintaining contact with he interior casing  12  wall should the internal diameter vary by use of stands of casing of different diameter in the string of casing. As the basket catcher  40  is moved from a casing  12  of one internal diameter to a casing of a different internal diameter the basket catcher blades will retract or expand under their spring bias to maintain contact with the wall of the casing  12 . Spring tensioning the blades  40 B also makes the tool more versatile too, a single basket catcher  40  can be used with casings  12  of many different sizes. It has been found that a single basket catcher  40  having spring-tensioned blades  40 B is suitable for use with 7 through 9⅝ inch interior diameter casings  12 , and these dimensions include the sizes more commonly used in oil well boreholes. 
     The ends of the blades  40 B distal the collar are formed to curve inwardly  40 D so that they do not catch on the collars  16  connecting the casing  12  together; the collars may have gaps or other imperfections in the wall of the casing as the basket catcher is withdrawn from the casing. Without the slight inward curve  40 D of the blades  40 B the blades may function like a barb or grappling hook and potentially hold the production string in the casing. 
     In the preferred embodiment a No-Go  26  is formed from four semi-circular wings  26 A welded to the exterior of the collar  40 A of the basket catcher  40 , arranged at regular intervals, here 90 degrees, to form a No-Go that will interfere with a the narrower-diameter liner  14  portion at the bottom of the bore, preventing the basket catcher from slipping into the liner. 
     It is preferred that the assembled basket catcher  40  made from the milled collar  40 A, blades  40 B and wings  40 D is nickel-coated to prevent corrosion of the metal of the basket catcher, after which the basket catcher is painted. 
     It is preferred that the basket catcher  40  be affixed below the submersible pump  22  below the lowest bands and flat guards  30  that could be lost with a length of perforated pup joint  40 E to serve the dual functions of connecting the basket catcher to the pump and of also creating a storage space to collect the broken bands and other debris as it is gathered when the string is removed from the casing  12 . Broken bands  30  for example can fill the basket catcher  40  and further wrap around and stack up on the perforated pup joint  40 E. Different lengths of pup joint  40 E can be used to afford suitably adequate storage for a given application. 
     In most cases the submersible pump  22  should be attached to the production tubing  24  at its upper end and to the perforated pup joint  40 E connected to the basket catcher  40  at the other lower end, so that the basket catcher resides lower in the casing  12  than the pump  22 . The No-Go  26  created on the basket catcher  40  prevents the basket catcher from slipping into the liner section  14 . In some applications however it is necessary to place the basket catcher above the pump  22 , for example when a tool such as a de-sander or an anode needs to be hung below the pump, perhaps to extend into the liner. In this embodiment the basket catcher  40  would be attached to the pump  22  above the pump with a pup joint and the perforated pup joint length  40 E would be attached to the production tubing. 
     Multiple basket catchers  40  can be used in combination with a single production tube  24  and pump  22 , placing them for example above and below the pump or along the production line, as desired, to effect multiple cleanings of the casing  14 . 
     In another embodiment a Y-Tool  50  may be used. A Y-Tool allows a second tool  52  to be affixed to the production tubing along with the pump  22 . For example, a Y-tool  50  may be affixed to the end of the production tubing  24  and the Y-Tool is also connected to both a submersible pump  22  and, for example, an instrument monitoring tube  52  or other equipment that might need to extend further toward the liner, past the basket catcher. 
     In this case one or more of the eight blades  40 B can be omitted to allow the tool  52  to extend through the basket catcher  50  where the blade  40 B was omitted. A band basket catcher  40  of this embodiment would include only seven blades  40 B, leaving an opening for that instrument tube  52  to extend through and past the basket catcher. 
     The method of the present invention is straightforward. One or more basket catchers  40  are affixed to a production string or pump  22  of the production string prior to inserting the production string into the casing  12 . When the production string is withdrawn debris caught by the one or more basket catchers  40  is removed and disposed of. In this manner most debris can be caught by the basket catchers, reducing or eliminating the need for cleaning out the casing, as is done in the prior art. 
     It will be appreciated that the invention has been described hereabove with reference to certain examples or preferred embodiments as shown in the drawings. Various additions, deletions, changes and alterations may be made to the above-described embodiments and examples without departing from the intended spirit and scope of this invention. Accordingly, it is intended that all such additions, deletions, changes and alterations be included within the scope of claims allowed for this application.