Sidewall anchor apparatus

Abstract

In accordance with an illustrative embodiment of the present invention as disclosed herein, an anchor assembly includes oppositely directed slip members that are shiftable between retracted and extended positions by an associated expander, the slip members when retracted having rear portions that extend beyond or overlap the center line of the assembly to provide for a uniquely wide range of expansion diameters. The assembly is principally useful in anchoring drill stem testing tools in open boreholes.

Description

This invention relates generally to well tool anchors of the type having expansible slips that grip the wall of a well bore to prevent longitudinal movement, and particularly to a new and improved open hole anchor suitable for use in borehole operations such as drill stem testing or the like where it is desirable to anchor the equipment off the bottom of a borehole.

A drill stem test, which may be considered to be a temporary completion of a newly drilled well, normally is conducted in open hole. The term "open hole" means that the interval of the well to be tested has not as yet had the casing installed. Thus it becomes necessary where the test is not conducted adjacent the well bottom to anchor the tools against longitudinal movement under conditions where the slip elements must grip the wall of the formation which may be rock or other earthen material. Although the formation wall will generally provide adequate support for the tools, problems arise due to the fact that the diameter of the borehole may be irregular, and in some cases can be quite large if the borehole has become washed out to some extent during the drilling operations, making it difficult if not impossible to obtain an anchor with conventional apparatus.

It is therefore an object of the present invention to provide a new and improved open hole anchoring apparatus having the capability for anchoring in an unusually wide range of borehole diameters.

Another object of the present invention is to provide a new and improved open hole anchor that is constructed and arranged to provide ample slip-expander surface contact and supporting area over a wide range of slip expansion diameters to provide the capability for obtaining a firm anchor for associated well apparatus in irregular and washed out borehole conditions.

These and other objects of the present invention are attained through the provision of oppositely disposed, generally wedge-shaped slip elements that are carried by a tubular housing and adapted to be shifted outwardly from their normally retracted positions to extended positions by an expander member that is movable longitudinally of the housing. A rear portion of one slip member is recessed and adapted to receive a rearward portion of the other slip member so that in the retracted position, the rear portions overlap one another and past the longitudinal axis of the housing. Thus arranged, it is possible for the slip members to be extended outwardly of the housing by the expander and into engagement with a borehole diameter that is significantly larger than is possible with typical prior art devices, while retaining a desirable amount of surface area contact between the expander and the respective slip elements. Such contact area insures the capability for forcefully anchoring the slip elements against a borehole wall without damage to the slip elements, the expander, or the slidable spline connections therebetween.

The present invention has other objects and advantages which will become more clearly apparent in connection with the following detailed description of a preferred embodiment, taken in conjunction with the appended drawings in which:

FIG. 1 is a schematic view of a borehole with a packer and associated testing equipment being anchored therein;

FIGS. 2A and 2B are longitudinal sectional views, with portions in side elevation, of the anchor apparatus of the present invention;

FIG. 3 is a side sectional view of one of the slip members of the anchor apparatus of the present invention;

FIG. 4 is a rear view of the slip member of FIG. 3;

FIG. 5 is a side sectional view of the other slip member of the anchor apparatus;

FIG. 6 is a bottom view of the slip member of FIG. 5; and

FIG. 7 is a side view of the expander member that is utilized to expand and retract the slip members.

Referring intially to FIG. 1, a schematically illustrated assemblage of drill stem testing tools is shown suspended in well bore 10 on pipe string 11. The tools as disclosed in further detail in copending application Ser. No. 410,944, assigned to the assignee of this invention, will normally include a straddle packer assembly capable of sealing off and isolating the interval of the borehole that is to be tested, and may comprise, for example, spaced apart, inflatable elements 12 and 13 that can be inflated and expanded outwardly into sealing contact with the surrounding well bore wall. A pump assembly 14 is used to supply fluid under pressure to effect expansion of the packing elements in response to appropriate manipulation of the pipe string 11, and a valve 15 can be operated at the end of the test in order to deflate the packer elements and to equalize pressures. A tester assembly 16 also is actuated by movement of the pipe string 11 and includes valve elements which open and close a test passage extending through the tools from test ports 17 located between the packing elements 12 and 13 upwardly into the pipe string 11 so that the insolated interval of the borehole can be permitted to flow for a period of time and then can be shut-in to enable recordal of pressure build-up data by a typical pressure recorder 18. A sample chamber in the tester assembly 16 functions to trap the last flowing portion of the formation fluids for subsequent inspection and analysis. A reverse circulating valve 19 can be operated at the end of a test in such a manner that formation fluids recovered in the pipe string 11 can be cleared to the surface before the equipment is withdrawn from the borehole.

The lower end of the string of tools is constituted by an anchor assembly 25 that is constructed in accordance with the principles of the present invention. The anchor assembly 25 in overall arrangement includes a mandrel 26 that is telescopically and rotatably received within an elongated housing 27. The housing 27 carries drag means such as bow spring 28 that engage the well bore wall to inhibit rotation, and oppositely facing slip elements 29 and 30 that are adapted to be extended by an associated expander from retracted positions to extended positions in anchoring contact with the well bore wall as shown. Such extension as well as release of the slip elements 29 and 30 is accomplished in response to movement of the mandrel 26 relative to the housing 27 through appropriate manipulation of the pipe string 11 at the surface as will be more fully described herebelow.

As shown in enlarged detail in FIGS. 2A and 2B, the elongated tubular housing 27 may be constituted by several interconnected sections including an anchor sub 31 and a drag sleeve assembly 32. The drag sleeve assembly 32 includes upper and lower connector subs 33 and 34, each of which carries a retainer sleeve 35, 36 fixedly attached thereto. The lower end portion of each bow spring 28 is received within the lower retainer sleeve 36, whereas the upper end portion of each spring is received within the upper retainer sleeve 35. The respective portions extend through vertical slots 37 and 38 formed in outwardly projecting shoulders 39 and 40 on the drag sleeve 32 and are otherwise loosely coupled within the retainers for limited vertical movement as the bow springs 28 flex laterally to accomodate various well bore diameters. The upper connector sub 33 carries a seal cap 42 that has an elastomer spline wiper ring 43 fixed internally thereof. A segmented spacer collar 44 is interfitted around the lower connector sub 34 and is bolted together by suitable means to provide for ease of assembly and disassembly of the various components. When the mandrel 26 is completely telescoped within the housing 27, a shoulder 45 engages the cap 42 to limit upward movement of the housing relatively along the mandrel.

The anchor sub 31 that forms the lower portion of the elongated housing 27 has two oppositely disposed side openings or windows 46 and 47 of a generally rectangular configuration, each of which is sized to receive a slip member 29 or 30. The slip members, shown in retracted position in FIG. 2B, each have downwardly facing wickers or teeth 50 on their outer peripheries that are adapted to bite into and grip the wall of the borehole when the slips are shifted outwardly to thus anchor the assembly against downward movement. The lower end of the sub 31 is closed by a bottom plug 51 having a plurality of radial ports 52 through which well fluids can enter into the interior spaces of the tool. In order to prohibit rocks, chips or other debris from coming in, however, disc-shaped filter screens 53 can be provided.

The slip members 29 and 30 have respective inner inclined surfaces which are engaged by the respective outer inclined surfaces of an expander member 54 which is movable vertically within the sub 31 from an upper position, as shown, where the slips are retracted, to a lower position where they are shifted transversely outwardly through the windows 46 and 47. To provide for a uniquely wide range of anchoring diameters, a rear portion of one slip member 30 is provided with a cavity that is adapted to receive a rear portion of the other slip member 29 when the members are in retracted position. In this manner, the rear portions of each slip member overlap one other in such position, or, in other words, the inclined expander surfaces thereof extend beyond the center line of the anchor sub 31. Accordingly, as the expander member 54 is advanced downwardly from its uppermost position as shown in FIG. 2B, the slip elements 29 and 30 can be extended laterally outwardly by a significantly greater amount than was heretofore possible while maintaining adequate contact area between the expander member and the slip members to properly support them in contact with the well bore wall. Moreover, a length of contact can be maintained adequate to prevent binding of the dovetail spline and groove couplings between the expander member and the respective slip members as will be described more fully below.

As shown in side section in FIG. 3 and in rear view in FIG. 4, the recessed slip member 30 has a rectangular cavity 58 formed in the rear thereof, with the inner wall 59 of the cavity being inclined with respect to vertical by an angle of about 15.degree.. A "dovetail" spline groove 60 is provided along the rear face of the slip element 30 with the bottom surface 61 of the groove intersecting the rear wall 59 of the cavity 58 at approximately the midportion of the slip body. Side walls 62 and 63 of the groove 60 are inclined inwardly and outwardly in a typical manner, whereby additional bottom surfaces 64 and 65 extend along either side of the cavity 58 over the lower portion of the slip body. The bottom surface 61 and the surfaces 64 and 65 provide ample bearing area for the expander 54 in the expanded position of the slip member 30. The opposite slip member 29 as shown in side section in FIG. 5 and in bottom view in FIG. 6, has an outwardly projecting portion 68 to the rear thereof with a transverse dimension sized to fit within the cavity 58 of the recessed slip member 30. A "dovetail" spline rib 69 extends for the full length of the back of the slip member 29, and has inwardly inclined side walls 70 formed in a typical manner. The outer wall surface 70 of the spline rib 69 provides an expander contact surface with ample area. The rearwardly facing walls 71 and 72 extending to either side of the splined portion 68 are appropriately shaped and arranged to interfit with the wall surfaces 73 and 74 of the recessed slip member 30 in the retracted position.

The expander member 54 that coacts with the slip members 29 and 30 to cause expansion and retraction thereof, is shown in cross-section in FIG. 2B and in side view in FIG. 7. The reduced upper neck portion 76 is appropriately threaded internally for connection to an expander drive sleeve 77, and externally for connection to an adjusting sleeve 88. An intermediate portion 78 of the expander member 54 is generally tubular in form. The lower end portion 79 of the expander 54 is generally wedge or spade-shaped with exterior flat wall surfaces 80 and 81 that incline downwardly and inwardly to an apex. One side of the lower portion 79 is provided with a dovetail spline rib 82 that slidably engages the spline groove 60 in the recessed slip member 30, whereas the other side has a spline groove 83 that slidably engages the spline rib 69 on the opposite slip member 29. Vertically extending keyways 84 and 85 are provided in the tubular portion 78 of the expander 54 and are engaged by longitudinal keys 86 and 87 on the anchor sub 31 to prevent relative rotation. As previously mentioned, the slidable spline connection between the slip members 29 and 30 and the expander 54 cause the slips to be positively retracted to the positions shown in FIG. 2B when the expander is in the upper position within the sub 31, whereas the respective coengaged expander surfaces cause outward shifting of the slips to expanded positions in response to downward movement of the expander relative to the anchor sub.

The expander member 54 is connected by threads to the drive sleeve 77 which extends upwardly within the housing 27 and has an internally threaded section 89 at its upper end. The outer periphery of the section 89 is provided with longitudinally extending spline grooves 90 that mesh with inwardly directed spline ribs 91 on the drag sleeve 32 to prevent relative rotation therebetween. The body member or mandrel 26 extends downwardly into the housing 27 and within the drive sleeve 77 and is provided with a threaded collar 92 at its upper end for connecting the mandrel to the tools thereabove. The mandrel 26 is provided with longitudinally extending splines 93 running throughout a majority of its length and is reduced in diameter along its lower portion 94.

A clutch member 96 in the form of cylinder that is cut longitudinally at circumferentially spaced points from its lower end is slidable relatively along the mandrel 26. The formation of the cuts divides the cylinder for a majority of its length into a plurality of laterally flexible fingers 97, each of which has an enlarged head portion 98 at its lower end as shown in FIG. 2A. The head portions 98 having external threads 99 that mesh with the internal threads 100 on the drive sleeve section 89, and internal spline grooves 101 that mesh with the spline ribs 93 on the mandrel 27. The upper end portion 103 of the clutch member 96 is circumferentially continuous and also is provided with internal grooves 104 in mesh with the mandrel ribs 93, whereas its external configuration is provided by an outwardly directed shoulder 105 that is located below an inwardly directed stop ring 106 on the connector sub 33.

The outer diameter of the intermediate mandrel section 108 is sized such that the threads 99 on the head portions 98 are locked in engagement with the threads 100 on the drive sleeve 77 when the mandrel 26 is telescoped downwardly within the housing 27 however when the mandrel 26 is elevated with respect to the housing 27 by an amount sufficient to dispose the reduced diameter section 94 thereof adjacent the head portions 98, the fingers 97 and the head portions 98 can resile inwardly by an amount sufficient to disengage the threads 99 and 100 and permit the drive sleeve 77 to be forced in an upward direction with respect to the housing 27 by a coil compression spring 110 that surrounds the drive sleeve 77 and reacts between a downwardly facing shoulder surface 111 on the sleeve 77 and an upwardly facing shoulder surface 112 on the lower connector sub 34.

In operation, the string of test tools is lowered into the well bore 10 on the pipe string 11 and positioned such that the packer elements 12 and 13 straddle the interval of the well to be tested. During lowering, of course the elements 12 and 13 are deflated, and the slip elements 48 and 49 are in retracted positions. The bow springs 28 slide downwardly along the borehole wall in frictional engagement therewith and tend to support the elongated housing 27 such that the mandrel 26 is fully telescoped therewithin. In order to actuate the pump assembly 14 in response to upward and downward movement of the pipe string 11, it is necessary to anchor against downward movement, which is accomplished in the following manner. The pipe string 11 is rotated to the right, causing the entire assemblage of tools above the anchor assembly 25 to rotate also. The mandrel 24 is thereby rotated with respect to the housing 27 which is held stationary by frictional engagement of the drag springs 28 with the well bore wall, causing the clutch cylinder 96, which rotates with the mandrel, to feed the drive sleeve 77 downwardly with respect to the housing 27. The corresponding downward movement of the expander 54 causes the slip members 48 and 49 to be shifted laterally outwardly through the windows 46 and 47 until their teeth 50 come into gripping contact with the wall of the borehole. Due to the initial overlapping formation of the rear portions of the slip members, they have an unusually wide range of expansion and are capable of anchoring against a well bore diameter that is, for example, from 1.6 to 1.7 times the diameter of the anchor sub 31 while still retaining proper surface area contact between the expander member 54 and the rear surfaces of the respective slip elements 48 and 49. As the drive sleeve 77 is advanced downwardly, the coil spring 110 is compressed and loaded and thus urges the drive sleeve upwardly or in the direction to retract the slip elements. When the mandrel 26 has been rotated eight to ten revolutions with respect to the housing 27, the slip elements 48 and 49 will normally have engaged the well bore wall, which can be confirmed at the surface by lowering the pipe string 11 and observing on the rig weight indicator that the anchor assembly 25 is supporting a load.

The anchor assembly 25 prevents downward movement of the tools as the pump assembly 14 is actuated in order to inflate the packing elements 12 and 13 and thereby isolate the formation interval that is to be tested. With the elements inflated, the tester valve assembly 16 is operated to alternately flow and shut-in the formation to enable the pressure recorder 18 to instrumentally record the resulting data. When the data has been recorded and it is desired to terminate the test, the valve assembly 15 is operated to cause pressure equalization and deflation of the packer elements 12 and 13. The anchor assembly 25 is released by simply picking straight upwardly on the pipe string 11.

It will be recognized that when the mandrel 26 is moved upwardly relative to the housing 27 by an amount sufficient to position the reduced diameter lower section 94 thereof behind the head portions 98 of the clutch member 96, the head portions are unsupported and are free to resile inwardly. As the teeth 99 and 100 disengage, the compressed coil spring 110 forces the drive sleeve 77 upwardly within the housing 27 to its original position. The drive sleeve 77 of course moves the expander member 54 to its upper position, whereby the respective spline couplings 60, 82 and 69, 83 cam the slip elements 29 and 30 inwardly to their fully retracted positions, so that the anchor assembly 25 can be moved longitudinally through the well bore with the tool string thereabove. The anchor assembly 25 can be set repetitively in the well bore by merely lowering the mandrel 26 within the housing 27 to position the enlarged diameter splines 93 behind the head portions 98 of the clutch member 96 to thereby lock them in engagement with the threads 100 on the drive sleeve section 89, and then rotating the mandrel to effect downward feeding of the drive sleeve 77 as previously described.

It now will be appreciated that a new and improved anchor assembly has been disclosed having a unique slip construction that provides the capability for anchoring in a wide range of borehole diameters, while retaining ample slip-expander surface contact area to prevent binding or breakage of slidable spline connections. Since certain changes or modifications may be made in the disclosed embodiment without departing from the various inventive concepts involved, it is the aim of the appended claims to cover all such changes and modifications falling within the true spirit and scope of the present invention.

Claims

I claim:

1. Apparatus adapted for anchoring a well tool against longitudinal movement in a borehole, comprising: a tubular housing having a longitudinal axis; oppositely disposed slip members mounted on said housing for lateral movement between mutually retracted and extended positions, one of said slip members having recess means in a rear portion thereof arranged and adapted to receive a rear portion of the other of said slip members in said retracted position whereby said portions of said slip members can overlap one another and extend beyond the longitudinal axis of said housing in said retracted position; and expander means movable longitudinally of said housing and said slip members and hvaing inclined surfaces cooperable with companion inclined inner surfaces on said slip members for shifting said slip members from retracted to extended positions in response to movement of said expander means relative to said housing in one longitudinal direction.

2. The apparatus of claim 1 further including slidable spline connections between each of said slip members and said expander means for enabling said expander means to shift said slip members from extended to retracted positions in response to movement in the other longitudinal direction.

3. The apparatus of claim 2 wherein said housing is provided with oppositely disposed windows through which a respective one of said slip members is laterally movable; and further including means for preventing relative rotation between said expander means and said housing.

4. Apparatus adapted for anchoring a well tool against longitudinal movement in a borehole, comprising: a housing; oppositely facing slip members mounted on said housing for lateral movement between mutually retracted and extended positions, one of said slip members having a rearwardly opening cavity, the other of said slip members having a rearwardly extending section sized and arranged to interfit within said cavity when said slip members are in said retracted position; and expander means movable upwardly and downwardly in said housing and having inclined expander surfaces cooperable with inclined expander surfaces on said slip members for shifting said slip members from said retracted position to said extended position in response to downward movement of said expander means with respect to said housing.

5. The apparatus of claim 4 wherein the inclined surfaces on said one slip member include surface areas disposed to either side of said cavity, and the inclined surfaces on said other slip member include a surface area extending along said section.

6. The apparatus of claim 5 further including slidable spline connections between each of said slip members and said expander means for causing retractive movement of said slip members in response to upward movement of said expander means.

7. The apparatus of claim 6 wherein said spline connection between said expander means and said one slip member includes a spline rib on said expander means slidably interconnected with a spline groove formed along the rear of said one slip member, and wherein said spline connection between said expander means and said other slip member includes a spline rib extending along the rear of said other slip member slidably interconnected with a spline groove in said expander means.

8. Apparatus adapted for anchoring a well tool in a well bore, comprising: a tubular housing having a longitudinal axis; first and second slip members carried by said housing and being arranged for transverse movement in opposite lateral directions between mutually retracted and extended positions, said first slip member having a cavity formed therein with inclined expander surfaces extending to either side of said cavity, said second slip member having recess means formed to either side of a rearwardly projecting section thereof with an inclined expander surface extending along said section, said section interfitting within said cavity in said mutually retracted position to enable said expander surfaces on each slip member to extend beyond said longitudinal axis in said mutually retracted position; and expander means movable longitudinally within said housing member and cooperable with said expander surfaces of said slip members for shifting said slip member between said mutually retracted and extended positions.