Patent Publication Number: US-4733723-A

Title: Gravel pack assembly

Description:
This is a continuation of application Ser. No. 886,731, filed 7-18-86, now abandoned. 
    
    
     FIELD OF UTILIZATION 
     The present invention relates generally to the field of well completion and more particularly to sand control in wells. Specifically, this invention relates to placement of gravel pack screens and their release with flow controls peculiar to such operations manageable by manipulation of the working pipe string and control of flow of fluids moving therethrough. 
     BACKGROUND OF THE ART 
     The flow of sand into producing oil and gas wells from the producing formations is well known. The best current sand control practice involves placement of gravel screens in the well in the vicinity of the production zone and packing gravel around the screen and into the formation openings to retard the entrainment of sand by fluids migrating to the well bore. 
     Gravel packing is usually done by the crossover method. The crossover method involves lowering a gravel screen below a crossover device and a packer to the payzone area on a working pipe string. The packer is closed against the well bore wall, and the gravel (usually in a viscous carrier fluid, or slurry) is pumped down the work string flow bore and dumped in the well annulus outside the screen below the packer. The carrier fluid is allowed to return through the screen into a stinger washpipe extending into the screen interior, back to the crossover means, where it is directed into the well bore above the packer. 
     Hardware has evolved that allows the work string to control the packer, crossover device, and release the screen from the work string, so that the screen is left in the well, and most other hardware is recovered with the work string. 
     Advantages of the crossover system includes confinement and control of the downflowing gravel slurry within the work string to prevent contamination of the upper well bore with gravel and debris dislodged by gravel. 
     When packers and gravel screen release contrivances are both used on one work string, the manner of setting the packer and releasing the screen should be separate, so that packer manipulations do not also release the screen. By using work string rotation and weight to set the packer and hydraulic pressure to release the screen, several operations can be carried out in one trip into the well with the work string. Flow through the work string is essential to several well-conditioning operations, and it is desirable to flow without releasing the screen. It is common practice to drop an object down the work string bore to prepare downhole machine elements to release screens on the next occurrence of forward circulation through the work string bore. 
     Prior art in releasing tools downhole without rotating the work string is typified by U.S. Pats. Nos. 2,409,811 and 4,175,778; the latter being specific for gravel packing and the former being more general in nature. 
     The screen release apparatus most closely related to the present invention is disclosed in U.S. Pat. No. 4,570,714. In terms of net effect, the present invention distinguishes in providing a forward or reverse circulation flow through channel to the very bottom of the screen assembly in communication with the work string flow bore prior to screen release and the ability to close the lower screen penetrating channel on screen release. The feature permits apparatus of the present invention to be used as if it were only a work string with a packer to reverse out sand and other materials without compromising the screens. Additionally, the present invention permits clean fluid to be used to backflush screens if they become plugged in well treating. Such actions are not possible with apparatus of the U.S. Pat. No. 4,570,714. It is quite possible to avoid one work string trip into the well with apparatus of the present invention. 
     OBJECTS OF THE INVENTION 
     Therefore, it is an object of this invention to provide well treating apparatus that permits full length forward and reverse circulation of fluid through a work string and gravel pack screen assembly prior to screen release. 
     It is another object of this invention to provide apparatus to close off the lower extremity flow bore penetration of the gravel screen assembly when the screen assembly is released from the work string. 
     It is yet another object of this invention to provide well treating crossover control apparatus that has no crossover channels until crossover is actuated. 
     It is still another object of this invention to provide a circulation valve to control fluid flow between the interior of the released screen and the well annulus above a set packer integral with the packer manipulation equipment. 
     It is yet another object of this invention to provide apparatus to operate either the packer or the circulation valve by choice of sequence and nature of axial and rotational manipulation of the work string. 
     It is yet another object of this invention to provide a hydraulically actuated crossover valve for a well treating gravel packing system that simultaneously releases a gravel screen with crossover valve actuation. 
     It is still a further object of this invention to provide well treating apparatus that releases gravel pack screen assemblies and permits recovery of the reusable packer controls, crossover valve, and screen release assemby as well as the screen stinger. 
     It is yet another object of this invention to provide methods to clean up a well bore, gravel pack, squeeze, circulate out fines, and recover all downhole hardware not essential to the gravel screen assembly, in one trip. 
     It is still a further object of this invention to provide apparatus to permit elected closure and pressure testing of a foot valve below a screen assembly before the screen is released. 
     These and other objects, advantages, and features of this invention will be apparent to those skilled in the art from a consideration of this specification, including the attached drawings and appended claims. 
     SUMMARY OF THE INVENTION 
     The method and apparatus of the present invention involves a working pipe string extending from the earth surface down a cased borehole to a payzone region, and a formation treating assembly attached to the work string. 
     The suspended treating assembly includes a conventional packer, a conventional gravel screen assembly, and a novel manipulation apparatus. 
     The novel manipulation apparatus provides means under all conditions to actuate the packer and to carry out a configuration change in the fluid channeling. 
     As the apparatus is installed in the well, the fluid channel of the work string continues through packer and gravel screen stinger, to be ejected below the screen assembly. Forward and reverse circulation can be conducted, and the packer can be closed, after which the formation can be squeezed without pressuring the upwardly continuing well annulus. 
     To change downhole configuration, a plug is dropped down the work string bore to land on and occlude a piston exposed to the work string bore pressure. Pressure applied to the work string bore causes the piston to affect: 
     (1) plug the downwardly continuing fluid channel from the work string bore, where it once joined a stinger flow bore that extended below the screen assembly; 
     (2) detach the screen assembly from the work string, allowing the screen the drop down, sealingly sliding down the stinger; 
     (3) pull the open lower end of the washpipe into the screen assembly. 
     (4) closes the once open lower flow channel that once extended from the washpipe out the lower end of the screen assembly. 
     (5) opens crossover valves that connect the upwardly continuing work string flow bore to the well annulus below the packer and connects the stinger flow bore, by way of confining fluid flow galleries, to a valve between the work string and the packer, which opens to the well annulus above the packer. 
     Once the downhole configuration is changed, the valve between the packer and work string controls pressure and flow communication between the upper well annulus and the stinger flow bore opening inside the lower portion of the released screen assembly. 
     Before configuration change, the assembly can be used, by reverse circulation as appropriate, to clean out a well, acidize, and squeeze. After configuration change, with packer set, gravel pack can be provided down the work string flow bore with carrier fluids being returned through the screen. 
     After gravel packing is complete, the work string, packer, crossover-release assembly, and stinger are recovered from the well bore, leaving the gravel screen assembly downhole. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     In the drawings, wherein like reference characters are used throughout to designate like parts: 
     FIGS. 1A and 1B are side views, mostly in cutaway, of the preferred embodiment of the invention in the before activation and after activation configurations; 
     FIGS. 2A and 2B are downward continuations of FIGS. 1A and 1B respectfully; 
     FIG. 3 is a surface development of a selected area of the embodiment of FIGS. 1A and 1B; and 
     FIGS. 4A and 4B are side views in cutaway of a selected area, rather enlarged, of the embodiment of FIGS. 1A and 1B. 
     FIGS. 5A and 5B are side views, in cutaway, somewhat enlarged, of an alternate foot valve configuration for the general embodiment of FIG. 1b. Before and after actuation conditions are shown. 
     FIGS. 6A and 6B are side views, in cutaway, of an alternate configuration of the invention for use in wells with sump packers installed. 
    
    
     DETAILED DESCRIPTION OF DRAWINGS 
     Tools used in well bores are necessarily of small diameter, and in most cases the tool structures are quite slender. Small scale drawings of such tools can be more clearly presented if the diametral dimension is shown enlarged relative to length, and the present drawings are distorted in scale for clarity. Additionally, manufacturing and maintenance considerations frequently result in several elements being fastened together to form one functional structure. Where such complicating details have no bearing on points of novelty, the functional structure may be shown as one part. Further, those surfaces situated for relative motion with fluid sealing integrity are captioned by the letter S rather than attempting to define a seal shape in the sealed region. The steps taken to simplify drawings to improve drawing and descriptive clarity are justified on grounds that those skilled in the art disclosed are inherently skilled in the fundamentals of machine constuction art as well. 
     An overall functional description will be followed by more specific details. 
     FIGS. 1A and 2A are mutually continuing drawings, and FIGS. 1B and 2B represent the same apparatus after actuation in a well bore. FIGS. 1A and 2B show apparatus in the runin configuration for the trip into a well bore, but the apparatus can be used as shown for forward or reverse circulation to clean out a well bore. Additionally, packer 4 can be actuated to carry out some activity. 
     Manipulator arbor 1 and circulating housing 2 form a circulating valve assembly attached to an upwardly continuing work string WS and to a conventional packer 4. Crossover-release 5 is attached to the packer and is releasably attached to a mating screen nipple 9. Screen nipple 9 is attached to a conventional gravel screen assembly 11 and 13. A blank pipe is usually situated between nipple 9 and screen 11. An O-ring sub 12 is usually used between screens 11 and 13. 
     Foot valve 14 is unique and provides the lower terminus of the apparatus. 
     Packer 4 is conventional and purchasable hardware, actuated by work string rotation followed by application of weight, and releasable by reverse rotation and lift on the work string. As shown actuated in FIG. 1B, rubber packers 4a are expandable to seal against the well bore wall. Slips 4b are pushed out by packer actuation and grip the well casing (WC) wall to provide axial holding ability. There are two fluid flow paths through the packer. Inner tube 1e provides bore 1c, which completes a channel from the work string bore to bore 5c of crossover-release assembly 5. The second channel is an annulus 4c outside tube 1e within the packer mandrel. In the runin configuration, the second channel is closed in both axial directions and is ineffective. Some form of drag block (not shown) is usually supplied with the packer to provide a drag resistance on the well bore wall. 
     In the run-in configuration, flow down the work string bore has continuity, because piston 6 is sealingly situated in the crossover release assembly 5 to close ports 5d and ports 6a to deliver flow through bore 6b to the stinger bore 8a. The stinger, or washpipe, 8 is sealingly connected to foot valve 14 by surface 8b in bore 14g and delivers flow in bore 8a to enclosure 14c and out openings 14d. The flow can go either way. In the run-in configuration, the overall apparatus functions as a single tube to permit forward or reverse circulation to the very bottom of the well. 
     As shown in FIG. 2b, plug 16 can be dropped down the work string bore to enter bore 6b, seal against seat 6e, and engage undercut 6f with snap ring 16a. Snap ring 16a is in a deep groove in plug 16 and can be pushed below the surface of the plug as it hits tapered seat 6e to enter bore 6b. The snap ring holds the plug in place. The snap ring, a means to hold the plug in place, may shortly be replaced by a collet having tubular spring fingers tipped with lugs that extend in interference to upward movement of the plug once it moves downward into bore 6b. 
     With plug 16 in place, fluid is pumped down the work string bore to push piston 6 downward to shear bolt 7, open ports 5d, and move cylindrical surface 6d out from under lugs (or balls) 10, and allow them to move in recess 6c. This releases groove 9b and the related screen assembly, and nipple 9c moves down. Snap ring 6g is in a deep groove in piston 6, and when it moves below extension 5f the ring snaps out to prevent the upward movement of piston 6. 
     Once the screen assembly is released, it commonly drops about two feet, the amount determined by positioning the apparatus a selected distance above well bottom before the packer is actuated to seal. The well bottom may be a bridge plug. 
     When the screen assembly is released and drops, washpipe terminal 8b is pulled out of bore 14g of the foot valve 14, and the new open end of the stinger washpipe 8 is inside screen 13. The stinger is sealed on the outside by O-ring sub 12. 
     With washpipe 8 no longer holding the foot valve down and open, spring 15, acting against flange 14a, moves the valve element upward. Ports 14d are drawn into the bore 14f and, hence, closed. Snap ring 14h expands once above bore 14f and avoids re-opening of the foot valve. Flange 14e stops upward motion of the valve movable element. 
     When assembling the apparatus at the rig floor, the foot valve may serve best if the removal of the washpipe from the foot valve is a reversible process. A simple toggle latch responsive to the washpipe presence to retract from an interfering position is now in use experimentally to replace the one-time action of the snap ring. The same purpose is served once the washpipe is moved upward after screen release downhole. 
     Cross-over and screen release are one time actions and not directly reversible. In the operational configuration of FIGS. 1B and 2B, there are still two significant actuation options. Arbors 1 and housing 2 are held together by lug 2a and groove 1f. As will be shown in FIG. 3, groove 1f allows lug 2a to move peripherally around arbor 1, provided it is moved axially at selected times. In application, arbor 1 is rotated by the work string, and if the work string is not moved axially, lug 2a will force sympathetic rotation of housing 2. 
     If housing 2 is rotated, the packer will be actuated if the packer is in a cased well bore, because slips 4b or drag blocks (not shown) always cause some wall drag, and the arbor 4e will rotate relative to the slips. The preferred off-the-shelf packer will, in time, seat and resist further work string rotation after weight is applied. 
     With the packer set, the work string can be lowered against the packer to slide the arbor relative to the housing to align ports 1d and 2c. This is a valving action, as will be later described. 
     FIG. 3 should be addressed in conjunction with FIGS. 1A and 1B. This is a surface development of grooves 1b and 1f in the cylindrical surface of arbor 2 viewed toward the apparatus centerline. Lug 2a is dotted in at position A and is trapped in groove 1f. The grooves 1f and 1b are on arbor 1 and, hence, are responsive to work string movement. Stress key 3 is biased radially inward from close-fitting pocket 2b and, hence, like lug 2a, can force movement of housing 2. 
     If the lug 2a is in position A, forward work string rotation can drive the lug left to rotate the packer arbor. If the work string is forced downward, lug 2a will tend to move along dashed line b1. Key 3, now clear of groove 1b, will slide along dashed line b2, provided the work string is rotated clockwise. When lug 2a reaches point B, the valve ports 1d and 2c are aligned and open. The work string can rotate the packer mandrel in either direction at position B. 
     From position B, the work string can be pulled upward Ito close the port 1d-2c valve, and from position c, the lug 2a can only move right in groove 1f, along dashed line d1, around to dashed line a1. Lug 2a cannot move from position C to position B, because key 3 will drop into groove 1b at position C to prohibit relative axial motion between arbor 1 and housing 2 until the workstring is rotated clockwise until key 3 is again at position A, in the discontinuity of groove 1b. 
     Note that the lug end groove arrangement permits the packer to be &#34;set&#34; or released whether the circulating valve (ports 1d and 2c) is opened or closed either before or after the gravel screen is released and fluid channel crossover is accomplished. 
     FIGS. 4A and 4B show a side view of key 3 and the related pocket 2b and groove 1b. Spring 3a is a compression spring. The groove 1b extends as shown in FIG. 4B almost completely around arbor 1. Near the peripheral position A of FIG. 3, the groove shallows out to a cylindrical surface, and key 3 can move vertically until the work string moves down enough to drop key 3 into groove 1b, the arbor 1 can move within limits imposed by lug 2a in groove 1f (of FIG. 3). The function of key 3 is to prevent return of lug 2a from position C to position B until the work string is rotated around to put lug 2a in position A. Key 3 also carries most of the axial load on large surfaces to protect the necessarily small lug 2a. 
     Once the screen assembly has been released, the packer can be unseated from the well bore wall by rotating the work string counterclockwise and lifting the load off the packer. The work string can then be moved upward until the lower end of stringer washpipe 8 has been moved above O-ring sub 12. The fluid communication to bore 8a then includes both screens 11 and 13. The stinger is still sealed against nipple 9. The packer is reset in this position by clockwise rotation of the work string and application of weight. 
     When operations yet to be described are complete, the packer is unseated by counterclockwise rotation and lifting of the work string, and the work string is removed from the well. This leaves the entire screen assembly in the well but recovers the stinger 8 and all elements above the stinger. 
     Having described the mechanical functions of the various features of the apparatus, operational matters can now be more effectively described. 
     In the run-in configuration of FIGS. 1A and 2A, the apparatus is usable to reverse out jell pills in the well from previous operations. Sand fill found in the well can be reversed to clean up the well bore to the bottom or bridge plug. 
     In the run-in configuration, the packer can be set, and surge valves up hole in the work string can be actuated This is old art involving the collapse of an air column trapped up hole in the work string to flow shock the formation. 
     With the packer set and the foot valve well above the perforations, a sand or gravel prepack can be run in the well and into the formation with fluid rising in the well annulus. After prepack is complete, sand settles out in the annulus and is reversed out, totally cleaning up the well bore. The packer can be set at will by clockwise rotation and downthrust, and various flow test and sequence operations can be performed. The order of such squeeze, flow, and prepack operations vary with circumstance but depend upon the tool utility for choices made by operators. 
     Crossover and screen release actuation is not a directly reversible process and is often preceded by various tests in the run-in configuration. Crossover and screen release can be done at any time by dropping plug 16 down the work string bore and applying fluid pressure to the work string. Common practice, however, will involve positioning the foot valve 14 about two feet above hole bottom and setting the packer before release of screens. 
     After plug 16 is in place, packer set, and screens released, the well annulus is divided into upper annulus above the packers and lower annulus below the packer. Fluid communication from the upper annulus goes through the circulation valve (ports 1d and 2c) when open, bore 1c, tubular annulus 2d, 4c, and 5b, veins 5e, ports 6a, bores 6b and 8a, and the inside of screen 13. 
     The work string bore will be communicated to the lower well bore annulus by bores 1c and 5c and ports 5d. 
     Gravel packing involves the injection of a gravel slurry into the work string bore at the earth surface to flow into the lower well annulus, into perforations shown adjacent screen 11, and into the formation. The formation is usually preconditioned to accept gravel, if not already prepacked. 
     With gravel packing underway, the carrier fluids may be accepted by the well formation or may be allowed to move above the packer from inside screen 13 with the circulating valve open. 
     If the formation accepts fluids too readily, the circulating valve may be closed to permit the work string bore to limit the rate of fluid delivery to the formation. In case the formation being treated requires high pressure, the circulating valve can be closed to prevent the high pressure standing on the upper well annulus of any reason, such as protection of higher perforations in the well. 
     When gravel covers the screen 13, flow to bore 8a and the upper well annulus will show more resistance, and the operator will know, from pressure gages, where the gravel level has evolved. 
     By unseating the packer and lifting the work string, stinger 8 can be moved up until the bore 8a is opening inside screen 11. The packer is commonly reset and gravel packing continued until screen 11 shows increased flow resistance. Additional gravel is commonly added in known amounts to fill the well annulus around the blank pipe between screen 11 and nipple 9. 
     With gravel packing completed, the work string is recovered with the downhole assembly minus the screen assembly as previously described. 
     FIGS. 5A and 5B represent an alternate embodiment of the foot valve 14 of FIGS. 2A and 2B. This valve permits actuation before screen release and permits pressure testing the foot valve after closure. 
     When fluid is pumped down the work string bore and through the washpipe bore 8a it flows into recess 16c, through openings 16d, into the opening 15a, and out valve seat 15f. Reverse circulation is, of course, carried out in the opposite direction. 
     Before the crossover release plug 16 is dropped down the work string bore, ball 17 is dropped and goes all the way down to seat 16b. When fluid pressure is added to the work string bore, snap ring 16f is pushed out of tapered groove 15b as plug 16 is moved downward to push poppet 16e into seat 15f. Snap ring 16f expands into groove 15c to hold the plug down. Plate 15e deforms downward under force to provide resilience to the sealing system even if plug 16 moves slightly upward due to clearance of snap ring and groove. 
     When the screen 13 is dropped, washpipe extension 8b is pulled upward out of the bore of plug 16, as was the case with foot valve configuration 14. The foot valve is sealed permanently. 
     FIGS. 6A and 6B show a modified apparatus for use with wells fitted with sump packers. A sump packer is sealed against well casing and provides hole below to act as a collection sump for fines that enter the screens. 
     Element 18 may be regarded as a combination O-ring sub to slidingly seal against washpipe 8 and a locator sub to spear into the bore of the sump packer 19. Extension 18c does not seal against the bore 19b of the sump packer, and fluid can be pumped down the well annulus through the clearance between extension 18c and bore 19b to clean out the sump and reverse out fines through bore 8a of washpipe 8. 
     When the screen assembly is released, or lowered by any process, seals 18b and 19c the screen assembly to the sump packer. The seal may be on an enlarged section of extension 18c instead but is still sealed to the packer in the lowered position. 
     To circulate through the screen 13, the washpipe is lifted upward, by repositioning the work string, to clear bore 19b. 
     The screen assembly is left in the well, and the attached elements of 18 continue to seal the screen to the packer. Fines entering the screens may fall below to the sump to extend the working life of the well completion function. 
     From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the method and apparatus. 
     It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims. 
     As many possible embodiments may be made of the apparatus and method of this invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.