US2881842A - Safety device - Google Patents

Description

H. T. WILSON SAFETY DEVICE April 14, 1959 2 Sheets-Sheet 2 7 Filed Dec. 20, 1956 FIG.6B

INVENTOR. H OMER T. w|| so- By Mam/.

FIG.6A

HIS ATTORNEY United rates SAFETY DEVICE Homer T. Wilson, Bakersfield, -Calif., assignor to Johnston Testers, Inc.,.Houston, Tex., a corporation of Texas Application December 20, 1956, Serial No. 629,539

1 Claim. (Cl. 166-221) The present invention relates tosafety devices and, morepar'ticularly, to a combined expansion and. safety joint ,to be connected below a formation testing tool and above an anchor pipe.

In formation tests of a type commonly made, a length of anchor pipe is suspended from a packer below the formation tester, and the anchor pipe, packer and tester are lowered through the borehole at the end of a pipe string until the anchor pipe sets on the bottom of the borehole or on some resistance. The anchor pipe then serves as a support to permit the packer to be expanded laterally against the walls of the borehole by setting down weight of the pipe string.

Occasionally the anchor pipe gets stuck at the bottom of the borehole, or while, going in or pulling out, and cannot be dislodged by manipulating the pipe string at the surface or by the use of jars. lt is therefore desirable to have a safety joint in the tester above the-anchor pipe and preferably between the packer and the anchor'pipe whereby the main body of the tester may be disconnected :from the anchor and removed to the surface, leaving the anchor pipe in the borehole. Since the pipe string is conveniently rotated to the right when coming out of the borehole to disconnect the joints, the safety joint should desirably not be disconnected by suchusual right hand rotation. For the sake of convenience and precision of control, however, the safety joint should desirably be released by right hand rotation of the pipe when the anchor pipe is stuck; However, the packer must first be unseated to permit unscrewing the safety joint below it.

It is therefore an object of this invention to provide a new and improved safety device for use with a formation testing tool which may be conveniently operated to disconnect the tool from stuck anchor pipe.

Another object of this invention is to provide a new and improved safety device for insertion between a packer and a length of anchor pipe which permits the packer to be unseated from the walls of a borehole and released from the-anchor pipe.

Yet another object of this invention is to provide a new and improved safety device which combines a disconnectable safety joint with expansion means permitting a packer to be unseated from the walls of a borehole.

These and other objects are attained in accordance with the present invention by a safety device, preferably connected between a packer and a length of anchor pipe, which combines the functions of a safety .jointsand an expansion joint. An elongated tubular mandrel is slidably received within a housing having upper and lower sections which may be disconnected by relative rotation, thus providing a safety joint. The upper housing section is keyed to the mandrel so as to be corotative therewith and so as toperrnit sliding movement of the mandrel between a retracted and anextendedposition. Means,

which may include interengagingsplines,are provided on the vlower end of the mandrel'and onthe lower'housing section to secure these parts for corotation when the mandrel is in its extendedposition while permitting relative ice rotation in the retracted position. The mandrel and one of thehousing sections are threaded at opposite ends for connection in a pipe string below a packer. Rotation of a the pipe string to the right at the surface when the mandrel is in'its retracted position permits the safety joint to be unscrewed. The provision for travel of the elongated mandrel between extended and retracted positions permits unseating of the packer before unscrewing the Other features of the invention and others of its obdetailed description when taken inconjunction with the accompanying drawings in which:

Fig. l is a schematic diagram of an exemplary arrangement of'apparatus extending into a borehole and including a safety device in accordance with the invention;

:Figs. 2iziand 2b are vertical cross-sectional views of the .upper andlower portions, respectively, of the safety device in its retracted position, portions being cut away to better show interior detail;

. .Figs. 3, 4and 5 are cross-sectional views of the apparatus ofFigs. Zaand 2b taken on lines 33, 4-4 and 5-5, respectively, looking in the direction of the arrows;

Figs. 6a and 6b are vertical cross-sectional views, similar to Figs. 2a .and 2b, showing the safety device in its extended position; and

Figs- 7 and 8 are cross-sectional views of the apparatus of Figs. 6a and 6b. taken on lines 77 and 8-8, respectively, looking in thedirection of the arrows.

In Fig.1 1 is showna borehole 10, either cased or uncased, traversing earth formations 11 and including a Zone which is to be tested for fluid-production. To exemplify. the practice of the invention there is shown a formation ltester 12 connected at the lower end of a pipe string 13. and including at least a packer 14 which 'is expanded to seatagainst the wall of'the borehole when the zone to be tested has been reached. A variety of for1nation testers may be employed. For illustrative purposes,

the formation tester 12 is shown to comprise a main or retaining valvenassembly 15, the .packer 14 connected .therebelow, perforated pipe 16 connected below the packer to admit a fluid sample and a pressure recorder housing 1'7 therebelow.

A safety device 18, which is the subject of the present invention, is fastened at its upper end to recorder housing 17 :and.has a. length of anchor pipe 19 suspended from its lower .end. As shown, anchor pipe 19 s ets on thebottom of borehole 10 to provide a support to permit packer v14-10 be expanded. laterally against the walls of'the borehole by setting down weight of the pipe string." The valve assembly 15 may suitably be' of the type shown and described at page 2721 ofthe Composite Catalog of Oil .Field and .Pipe Line Equipment, 21st (195556) edition,

published by the. Gulf Publishing Company, and combining the functions of arby-pass or equalizing valve, a main or retaining valve, as Well as a downwardly opening check valve. If desired, of course, one or more of these timetrons could .be performed by separate valves appropriately connected inthe pipe string. The pipe string itself may be of the type commonly referred to as drill string, a tubingvstring or. the like, and generally afiords a fluid-tight longitudinal-passage .for the flow of recovered fluids to the surface.

The-safetydevice 13 includes a top sub 20, a mandrel 30, a housing 40 including an upper section 50 and a lower section 60, an expansion sub 76, and a bottom sub 80. As shown inFig. 2a, the top sub 20 has a conventional .threaded upper .box end 21 to receive the threaded end ofrecorder housing 17. The lower end ofsub 20;.has. a. tapered and threaded opening 2 2 to receive threaded pin end 3110f the mandrel 30.

Mandrel 30 is an elongated tubular element with a longitudinally extending central bore 32 to permit passage of test fluid through its length. The upper and middle portions of the mandrel are formed with a plurality of keyways 33 (see Fig. 3), terminating short of an enlarged lower end 34 which defines an upwardly facing shoulder 35 and a downwardly facing shoulder 35a. A plurality of equally spaced grooves 36 defining splines are cut into lower end 34 to a depth which corresponds to the diameter of the unkeyed or unenlarged portion of mandrel 30, indicated by numeral 37.

The upper section 50 of housing 40 is a splined left hand pin having a central bore 51 of a diameter to receive the unkeyed portions of mandrel 30. A plurality of keys 52 extend along the bore at the upper end of section 50 to mate with keyways 33. The lower end of section 50 has a reduced outer diameter and a tapered and threaded pin end 53 thereon. The inside diameter of pin end 53 is smaller than the outside diameter of mandrel end 34 (see Fig. 8) whereby the shoulders 35 on mandrel 30 strike the downwardly facing shoulder 53a on the lower end of pin end 53 when the mandrel is slidably moved upwardly through housing 40 to its extended position.

The lower housing section 60, which. is more specifically a splined left hand box, has a tapered and threaded upper box end 61 to receive pin end 53, and ends 53 and 61 form a joint with mating left hand threads. This joint serves as a safety joint, since it may be separated by relative rotation of housing sections 50 and 60 to leave the anchor pipe 19 in the borehole. A central bore 62 is formed longitudinally of section 60 and has a diameter corresponding to that of mandrel end 34. A plurality of equally spaced splines 63 (see Fig. 4 and also Fig 7) extend inwardly from the surface defining bore 62 and have a size and pattern so as to mate with grooves 36 on mandrel 30. To facilitate interengagement of the grooves 36 and splines 63, splines 63 have tapered lower ends 64 which may be slightly rounded at the tips.

The expansion sub 70 is an elongated tubular section with a threaded upper box end 71 to receive a threaded lower pin end 65 on section 60. The threads at this joint, in contrast to those at the safety joints 53, 61 in housing 40, are right hand threads. Sub 70 has a longitudinally extending central bore 72 of a diameter to slidably and rotatably receive mandrel end 34, as is apparent in Figs. 2b and 5.

The bottom sub 80 has a threaded upper pin end 81 to receive the threaded lower box end 73 of expansion sub 70, and is also a right hand joint. Pin end 81 limits the downward travel of mandrel 30 since the central bore 82 therein is of smaller diameter than the outside diameter of mandrel end 34 thereby forming an upwardly facing shoulder 80a. Bore 82 completes a passage for allowing fluid to pass through safety device 18 from anchor pipe 19 to the packer 14 and the formation tester 12 thereabove. Sub 80 has a threaded lower pin end 83 to receive sections of anchor pipe 19. Of course, subs 70 and 80 may take other forms and comprise means to slidably and rotatably receive mandrel end 34 and to limit downward travel thereof, respectively.

In an exemplary operation, safety device 18 is connected in the pipe string below the formation tester 12 between the packer 14 and anchor pipe 19. As the formation tester, packer and anchor pipe are lowered through borehole at the end of pipe string 13, the Weight of the anchor pipe causes mandrel 30 to slide within housing 40 and sub 70 to assume its extended position, as illustrated in Figs. 6a and 6b. Grooves 36 on mandrel 30 mesh with splines 63 on lower housing section 60, and shoulders 35 contact pin end 53 to limit upward travel of mandrel 30 (see Figs. 7 and 8). Keyways 33 are engaged with keys 52 in this extended position, whereby mandrel 30 and both sections of housing 40 are corotatively secured together, and the safety joint between housing sections 50 and 60 cannot be separated.

The tapered lower ends 64 of splines 63 facilitate engagement of grooves 36 and splines 63. If these splines are misaligned so that ends 64 strike shoulders 35 as mandrel end 34 slides within housing 40, it requires only a small amount of rotation of pipe string 13 and mandrel 30, whcih are corotative, to align ends 64 with grooves 36 and enable meshing of grooves 36 and splines 63 under the weight of the anchor pipe.

When formation tester 12 reaches the zone which is to be tested, anchor pipe 19 is set on the bottom of the borehole 10 or on some resistance and serves as a support to permit packer 14 to be expanded laterally against the walls of the borehole by setting weight of the pipe string vertically downward. As the weight is set down. mandrel 30 slides relative to housing 40 and expansion sub 70 until the downwardly facing shoulder 35a on mandrel 30 strikes pin end 81 of bottom sub 80. Packer 14 is thereafter expanded and the test is made.

Occasionally the anchor pipe 19 becomes stuck at the bottom of the borehole and cannot be dislodged by the ordinary methods. Obviously, it is desirable to retrieve the packer as well as the formation tester 12, and to this end safety device 18 is inclined in the pipe string immediately above anchor pipe 19. According to this invention, the safety joint in housing 40 is separated by applying right hand rotation to pipe string 13 and mandrel 30 at the surface. Before this operation can be accomplished, however, packer 14 must be elongated to unseat it from the walls of the borehole, and to this end safety device 18 also includes expansion means to permit packer 14 to be picked up and freed from the walls.

When it is desired to withdraw formation tester 12 upwardly through borehole 10, packer 14 is unseated by picking up weight on pipe string 13. Packer 14 may be picked up by an amount corresponding to the length of travel of mandrel 30 in expansion sub 70 and lower housing section 60. It having been ascertained that the anchor pipe is stuck, enough Weight is set on pipe string 13 to cause mandrel 30 to slide relative to section 60 to disengage grooves 36 and splines 63, i.e. until shoulder 35 clears tapered spline ends 64.

Thereafter right hand rotation is applied to pipe string 13 at the surface. Since mandrel end 34 rotates freely within expansion sub 70 and since upper housing section 50 is keyed to mandrel 30 for corotation therewith, this right hand rotation operates to turn pin end 53 on upper section 50 relative to box end 61 on lower section 60, which, along with subs 70 and and anchor pipe 19, is held fast within the borehole. There is no separation at the joints between subs 60 and 70 and subs 70 and 80 because these are right hand joints and because mandrel end 34 rotates freely within expansion sub 70 and exerts no torque on this region. The result is that top sub 20, mandrel 30 and upper housing section 50 are withdrawn to the surface along with formation tester 12 and packer 14. The stuck anchor pipe 19, lower housing section 60, expansion sub 70 and bottom sub 80 remain in the borehole.

Safety device 18 may be similarly separated if anchor pipe 19 gets stuck in the borehole while going in or pulling out. When ordinary loosening means such as jars fail to dislodge the stuck anchor, it is again advantageous to unscrew the safety joint in housing 40 to salvage the elements thereabove in the pipe string and to permit fishing operations for the anchor pipe. In this mode of operation, weight is let down on pipe string 13 until mandrel end 34 clears splines 63 and, as before, right hand rotation is applied to the pipe string 13 at the surface to separate the safety joint between upper and lower housing sections 50 and 60.

Safety device 18 conveniently combines precision of control with ease of operation. The usual right hand rotations applied to the pipe string to operate the formation tester when the packer is seated do not operate the safety joint. Right hand rotations, on the other hand, when the packer is unseated and the safety device is collapsed, do not operate the tester to provide a convenient and well controlled means to operate the safety joint as desired. Travel of mandrel 30 relative to subs 50, 659 and 70 provides not only a means of securing the joint against separation but also provides the further function of allowing the packer to be picked up to free it from the walls of the borehole. Safety device 18 thus is a combination expansion and left hand safety joint.

A further advantage of safety device 18 is an additional convenience when pulling out of the borehole when the anchor pipe has not become stuck and is still connected to the pipe string. When pulling out the weight of the anchor pipe causes the safety device to assume the extended position of Figs. 6a and 6b in which grooves 36 and splines 63 are meshed together. In this position right hand rotation of pipe string 13 does not operate the safety joint because mandrel 3t and housing sections 50 and 60 are locked together for corotation. In this extended position, then, the joints in pipe string 13 may be unscrewed by the rotary table While pulling out instead of having to chain tong the pipe out. Clearly, right hand rotation of the rotary table will not separate the safety joint when the safety device 18 is in its extended position.

A preferred embodiment of safety device 18 has been illustrated and described. Since many modifications may be made in the preferred embodiment without departing from the principles of the invention, the invention is intended to include all such modifications and equivalents as fall within the scope of the invention as defined by the appended claim.

I claim:

A safety device for connection between a packer and an anchor pipe therebelow, comprising a tubular housing having an upper, an intermediate and a lower section,

said upper and intermediate sections having a left hand threaded connection, said upper section having a first here with internal splines extending therealong and a downwardly directed annular shoulder at its lower end, said intermediate section having a second bore of larger diameter than said first bore with longitudinal splines extending inwardly from said second bore substantially to the internal diameter of said first bore, said lower section having an unsplined third bore of substantially the same diameter as said second bore and an upwardly directed annular shoulder at its lower end, and a tubular mandrel having an upper section adapted for connection with a packer, an intermediate section having a reduced diameter for slidably fitting through the upper and intermediate sections of said housing and longitudinally grooved to receive the internal splines of said upper housing section only for continuous co-rotative engagement therewith, and a lower section of enlarged diameter slidably and rotatably received in said third bore to permit unthreading of said threaded connection by rotation of said mandrel relative to said intermediate and lower housing sections, said lower mandrel section defining upper and lower annular shoulders engageable with said downwardly and upwardly directed shoulders, respectively, in the upper and lower positions of said mandrel with respect to said housing to transmit longitudinal force from said mandrel to said housing, said enlarged lower section of said mandrel being grooved to receive the internal splines of the intermediate housing section in the upper position of said mandrel to prevent unthreading of said left-hand connection, said inter mediate mandrel section being of suflicient length to space said upper mandrel section above said upper housing section when the lower shoulder of said lower mandrel section bears upon the upwardly directed shoulder of said lower housing section.

References Cited in the file of this patent UNITED STATES PATENTS 2,317,021 Bassinger Apr. 20, 1943 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 881342 April 14., 1959 Homer T, Wilson It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1,, linen 41 and 42 for "released" read releas'able' column 5, line 3, for "to provide" read me but provide Signed and sealed this 1st day of." September 1959c Attest:

KARL Ii, AXLINE ROBERT C. WATSON Attesting Oflicer Commissioner of Patents

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