Screened boot basket/filter

[0002] The field of this invention is downhole cleanup of casing and liners and more particularly after cementing and before completion.

[0003] The cementing process is known to leave debris such as cement lumps, rocks, and congealed mud in the casing or liner. Other debris can be suspended in the mud and it can include oxidation lumps scale, slivers, shavings and burrs. A variety of well cleaning tools have been developed particularly to dislodge such debris from the casing or liner walls. Jet tools are used to blow such debris loose. A variety of casing scrapers and brushes have been developed to accomplish the same purpose. These tools have more recently been combined with additional tools to filter the downhole fluid and capture the debris therein for removal to the surface.

[0004] One such debris filtering tool is described in UK Application 2 335 687 and is called the Well Patroller, a trademark of the owner Specialised Petroleum Services of Aberdeen, Scotland. This device generally features a wiper cup that rides the inside of the casing. The cup prevents flow around a mandrel. As the tool is lowered, flow is directed through a plurality of ball check valves into an annular space behind a screen and out though the center of the cup and around the mandrel. In this embodiment, no filtration occurs as the tool is inserted and the cup wipes the casing wall. When the tool is brought out of the wellbore, the ball check valves close and fluid above the cup is directed to the annular space inside the filter and out through the filter. The annular space acts as a reservoir for debris retained by the filter. If the filter clogs pressure can be built up to blow a bypass rupture disc, or, in some embodiments to simply shear screws and blow the cup off the mandrel. There are shortcomings in this design. The most significant is that the opening size in the check valves is small and is prone to plugging with debris. When running in the Well Patroller, downhole progress is stopped every 90 feet or so as another stand of tubulars is added at the surface. During these times the fluid flow through the tool stops and debris suspended in the fluid will settle to the bottom of the tool. The debris will eventually accumulate to the point which the ball check valves can not open. Once fluid can not pass though the check valves, the annular restriction at the top of the tool will force the annular fluid to pass through the screen. Any debris in the fluid will not be able to pass through the screen. When the tool is pulled out of the well, the debris will be left in the well. The Well Patroller tool is used in conjunction with a separate tool to scrape debris off the inside casing wall. The wiper cup's purpose, in this tool, is to divert flow as opposed to scraping or swabbing the inner casing wall.

[0005] Other debris removal tools are shown in UK Application 2 335 218; U.S. Pat. Nos. 4,515,212 and 5,330,003. The tool in UK Application 2 335 218 requires forced circulation through a plurality of eductors coupled with a deflector for the induced flow to encourage solids to drop into an annular space. Boot baskets, such as those made by Tri-State Oil Tools Industries Inc., now a part of Baker Hughes Incorporated featured an annular space defined between a solid basket and a mandrel. Solids were capable of being captured on the trip downhole solely due to the velocity decrease as the flow emerged above the boot so that solids could drop into the annular space between the mandrel and the boot. Since the boot was solid, no meaningful capture of solids occurred on the trip out of the hole.

[0006] One of the objects of the present invention is to eliminate or, at least minimize, the shortcomings of the Well Patroller device and the other tools previously used to filter downhole debris. The objective is addressed by providing an improved open area in the valving to reduce the potential problems from plugging. Another feature is the retractable flow diverter which allows rapid insertion into the wellbore, and provides easy passage of suspended debris past the tool. Yet another feature improves the valve structure in this application to get away from spring loaded balls which can create maintenance concerns. These and other advantages of the present invention will be more readily apparent to those skilled in the art from a review of the preferred embodiment which appears below.

[0007] A downhole debris filtering apparatus is disclosed. In a preferred embodiment, the flow diverter is retracted as the tool is run in to provide easy passage for debris. Settling velocity is the rate at which debris will fall through the fluid. Settling velocity is dependent on the density of the fluid and the debris density. If the fluid velocity exceeds the settling velocity, the debris will rise. The restricted annular area outside the screens raises the fluid velocity. Above the cup sleeve, the annular area increases significantly and the fluid velocity is reduce to below the settling velocity to allow debris to settle to the bottom of the tool. On run in, the fluid merely bypasses on the outside of the filter. Large debris will settle into the tool as described. When pulled out of the hole the swab cup/flow diverter is actuated into casing or liner wall contact and a large passage is opened to allow flow though the filter. Small debris that has risen above the tool will be captured as the fluid is filtered through the screen. Another embodiment with a non-retractable cup uses a sliding sleeve valve with a large open area which promotes free flow and minimizes fouling from deposited debris.

[0008] FIGS. 1a-1eillustrate in section a first embodiment of the tool in the run in position.

[0009] FIGS. 2a-2eillustrate the same tool being pulled out of the well.

[0010] FIGS. 3a-3billustrate the distinct features of the preferred tool which differ from FIGS. 1a-1e, showing the retractable feature, in the run in position.

[0011] FIGS. 4a-4bare the tool portions of FIGS. 3a-3bin the pulling out of the well position.

[0012] FIGS. 5a-5eillustrate the preferred tool in the run in position with the sliding sleeve covering the screen.

[0013] FIGS. 6a-6eis the tool of FIGS. 5a-5ebeing pulled from the well.

[0014] Referring to FIGS. 1a-1e, the apparatus A, has a mandrel 10 with a top thread 12 and a lower thread 14. Top thread 12 can be used to attach a string (not shown) to run the apparatus A into wellbore 16. Those skilled in the art will appreciate that the wellbore 16 represents casing, liners, or any other tubular string downhole and will henceforth be referred to collectively as “casing 16”. Bottom thread 14 as well as top thread 12 can also accommodate other known cleaning tools such as scrapers and jets to name a few.

[0015] Mandrel 10 has a passage 18 that extends from bottom sub 20 to top sub 22. Outside of mandrel 10 is a screen 24 which defines an annular space 26 around the mandrel 10 for the purpose of accumulating filtered debris, as will be explained below. Annular space 26 has a lower end 28 shown in FIG. 1eadjacent bottom sub 20. As shown in FIG. 1c, screen 24 terminates in a sleeve 30 at its upper end. At its lower end, screen 24 is supported by the mandrel 10 via bottom sub 20. Mandrel 10 has a valve member 32 which engages a seat 34 on cup sleeve 36 during run in as shown in FIG. 1c. Cup sleeve 36 has a plurality of slotted openings 38 which are open at least in part to allow flow in the annular passage 40 between the casing 16 and the screen 24 to enter the cup sleeve 36 as shown by arrow 42. The screen 24 is bypassed during run in because the annular space 26 is closed off at its upper end 44 by contact of valve member 32 on seat 34.

[0016] A cup 46 acts as a seal and is retained by retainer 48 which is in turn mounted to cup or seal sleeve 36. A series of drag blocks 50 support the cup sleeve 36 against the casing 16 in a sliding manner well known in the art. Cup sleeve 36 has a rupture disc 52 which can be broken with applied pressure if the screen 24 gets clogged as to avoid pulling a wet string from the wellbore. Those skilled in the art will appreciate that other devices that will allow bypass of a clogged screen 24 can be employed instead of rupture disc 52 without departing from the invention. Finally, bolts 54 prevent relative rotation between the sleeve 30 and the cup sleeve 36 while allowing relative longitudinal movement.

[0017] The major components now having been described, the run in operation can now be explained. The mandrel 10 is advanced into casing 16. The cup 46 rides on the inside wall of casing 16 and the spring loaded drag blocks 50 do the same. This resistance allows the mandrel 10 to advance with respect to the cup sleeve 36 until the valve member 32 engages the seat 34. At that time further advancement of the mandrel 10 downhole is made possible by fluid moving in the annular space 40 around the outside of the screen 24 and through the openings 38. Fluid simply bypasses cup 46 which closes off annular passage 40 by passing through the cup sleeve 36, as shown by arrows 42.

[0018] FIGS. 2a-2eillustrate what happens on the trip out of the casing 16. An upward force on mandrel 10 brings it up and with it, screen 24 and sleeve 30. Because the cup 46 and the drag blocks 50 hold the cup sleeve 36 momentarily, relative movement occurs. As a result of this relative movement, the sleeve 30 covers the openings 38 and the valve member 32 moves away from the seat 34. The latter movement opens the upper end 44 of the annular space 26 to passage 58. As the mandrel moves uphole fluid flows through passage 58 through screen 24, as shown by arrows 60. If screen 24 plugs, pressure is applied to passage 58 to blow rupture disc 52 so that fluid can exit to the annular space 40 and bypass the screen 24. This prevents pulling a wet string if the annular space fills with debris or if for any other reason, the screen 24 plugs. When the tool is removed from the wellbore, the accumulated debris can be easily removed by removing bolts 25 near lower end 28 of annular space 26. At that point the sleeve 27 which has windows 29 can be rotated until windows 29 align with openings 31 adjacent the lower end 28 of annular space 26 (see FIG. 1e).

[0019] The preferred version of the apparatus has some changes illustrated in FIGS. 3a-3b, in the run in position. In other respects than those mentioned below, the embodiments are virtually identical. In the preferred version, drag blocks 62 support wiper sleeve 64 during run in, allowing the mandrel 66 to be advanced relative to it. This relative motion, on run in, places the valve member 68 in bore 70 of wiper sleeve 64, closing off passage 72. Wiper 74 is sufficiently rigid to maintain its cylindrical shape flanked above and below by support rings 76 and 78. The assembly of the wiper 74 with rings 76 and 78 can move longitudinally on wiper sleeve 64 during run in. Thus, running in will not cause the wiper 74 to collapse and extend outwardly to the position shown on FIG. 4auntil an upward force is put on the mandrel 66. Those skilled in the art will appreciate that moving the mandrel 66 downhole will direct fluid outside of screen 80 in annular passage 82 as shown by arrow 84. As the apparatus A advances downhole, fluid will pass around the outside of the wiper 74. No flow will go through screen 80 to speak of because the annular space 86 is blocked by valve member 68 in bore 70. Some flow could pass through bore 88 in mandrel 66 but the path of least resistance will be through annular passage 82. Screen 80 has a sleeve 90 which contains a rupture disc 92 or an equivalent device that can provide an emergency bypass of screen 80 if it becomes necessary when coming out of the well.

[0020] When it is time to trip out of the well, an upward force is placed on the mandrel 66 and it moves with respect to wiper sleeve 64. This movement shifts valve member 68 away from bore 70 to open up passage 72. Additionally, sleeve 90 engages ring 78 which buckles wiper 74 into contact with the casing or downhole tubular 94. Sleeve 90 moved up because it is attached to screen 80 which is in turn attached to mandrel 66. Since drag blocks 62 hold back wiper sleeve 64 the wiper 74 can collapse into the contact position for effective sealing of the inner wall of the casing or tubular 94. The filtering occurs as the apparatus A is pulled uphole. Fluid is forced to pass downwardly through passage 72 through screen 80 as shown by arrow 96.

[0021] The embodiment shown in FIGS. 5a-5eand 6a-6ehas a valving variation as compared to the embodiment of FIGS. 3a-3band 4a-4b. In FIGS. 5a-e the valve member 68 is eliminated in favor of sleeve 98, the top of which appears in FIG. 5b. Sleeve 98 is connected to sleeve 100, which is, in turn connected to mandrel 104. Sleeve 98 has a plurality of openings 106. Openings 106 are misaligned with openings 108 in the run in position so that screen 110 is completely covered on its exterior. Flow, represented by arrow 112 goes around the tool as the tool is advanced downhole (see FIG. 5c). Referring to FIG. 5b, the flow 112 goes past the flow diverter 114 which is in the relaxed position for run in. Due to the high velocity, the solids are retained by the flow 112 past the drag blocks 116, which have gaps between them to allow the flow 112 to progress. The larger solids 118 can drop into annular space 120 due to the velocity reduction as the flow area suddenly increases. It should be noted that the outer surface of the screen 110 is fully protected against deposition of solids during the trip downhole. On the trip uphole, the drag blocks facilitate the expansion of the fluid diverter 114 against the wellbore to create a seal around the exterior of the tool. Openings 106 are pulled up into alignment with openings 108 due to the upward force on mandrel 104. Sufficient relative movement occurs to compress fluid diverter 114 as it is retained sufficiently by the drag blocks 116. With the fluid diverter 114 in the position shown in FIG. 6b, tandem movement resumes and flow through screen 110 proceeds as illustrated by arrow 124. The flow 124 must pass through annular space 120 where additional solids, including the smaller particles, which did not previously drop out on the trip downhole, can be retained. Those skilled in the art will appreciate that although a windowed sleeve has been shown as the screen isolation member, other techniques are also within the scope of the invention. These could involve dissolvable coatings and cover sleeves which increase diameter under a twist akin to the action of a child's toy known as a finger trap. One way to accomplish this is to use interlocking elements such as a weave. When the elements a re twisted in a first direction they close up the openings between them. When the twist force is reversed the weave defines openings to allow flow through the screen. The advantage of having the screen 110 covered as solids-laden fluid flows past it is that there is a reduced chance of plugging and a lager flow at reduced pressure drop through the screen 110 on the trip up the wellbore.

[0022] Those skilled in the art will appreciate that wiper 74 can have a cup profile, or it can be a solid elastomer block or a bladder, as illustrated. The valving used in both embodiments and its location above the screen permits large flow areas which can let debris pass with minimal risk to clogging the valve structure. In both embodiments, if the increase in annular area is great enough to reduce the fluid velocity below the settling velocity of the debris, the debris will settle into the tool when running into the well. When stopping to add drill pipe, the tool will be pulled up enough to allow any debris that has accumulated above the wiper sleeve 64 to passthrough passage 96 and settle to the bottom of the tool. As distinguished from the Well Patroller, the flow through the screen is effectively stopped when running in the hole. In the Well Patroller, the fluid can pass through the screen at the same time that it passes through the ball valves. Debris is likely to be trapped to the outside of the screen and remain in the wellbore when the Well Patroller is pulled out.

[0023] Those skilled in the art will appreciate that the parts orientation of either embodiment could be reversed so that the cup 46 is open toward downhole with filtering occurring on the same trip down or on the trip up. Similarly the wiper 74 can be expanded on the trip down and retracted for the trip up. Filtration can occur on the trip up for example. It is also within the scope of the invention to coat the screen such as 24 with a removable material which can be dissolved or otherwise removed on the trip downhole or when the proper depth is reached. Coating the screen for the trip into the wellbore will reduce any tendency of buildup of debris on the outside of the screen on the way down. In the figures, the screens 24 or 80 are shown schematically and should be understood to contemplate the inclusion of such removable layers or coatings. Additionally, sealing can be accomplished with shapes different than cup 46. Other valving arrangements to close upper end 44 are also contemplated. Openings 38 may have different shapes and are preferred to be sufficiently large to allow loose debris to pass there through. When used herein, “screen” refers to any device which can let some material pass while retaining another and can include such structures as mesh, weave and porous materials, to name a few.

[0024] It is to be understood that this disclosure is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended other than as described in the appended claims.