US2399766A

US2399766A - Bridging plug

Info

Publication number: US2399766A
Application number: US468461A
Authority: US
Inventors: Wendell B Steward
Original assignee: Schlumberger Well Surveying Corp
Current assignee: Schlumberger Well Surveying Corp
Priority date: 1942-12-10
Filing date: 1942-12-10
Publication date: 1946-05-07
Anticipated expiration: 1963-05-07

Description

y 9 6- w. B. STEWARD 2,399,766

BRIDGING PLUG Filed Dec. 10. 1942 4 Sheets-Sheet 1 INVENTOR WENDELL B. STEWARD w. B. STEWARD 2,399,766

BRIDGING PLUG Filed Dec. 10, 1942 4 Sheets-Sheet 2 May 7, 1946.

\NVENTOR WENDE LL 5 TEWARD a 4 4 Z 31W M y 7, 1946- w. B. STEWARD 2,399,766

BRIDGING PLUG 4 Sheets-Sheet 3 Filed Dec. 10, 1942 \NVENTOR WENDELL B STEWARD y 9 6- w. B. STEWARD 2,399,766

BRIDGING PLUG Filed Dec. 10, 1942 4 Sheets-Sheet 4 INVENTOR WENDELL B. STEWARID Patented May 9 I g UNITED STATES PATENT OFFICE eamomo PLUG Wendell B. Steward, Houston, Tex, asslgnor to Schlumberger Well Surveying Corporation, Houston. Tex a corporation of Delaware Application December 10, 1942, Serial No. 468,461

11 Claims. (Cl. 168-13) V This invention relates to bridging plugs for bore is independent of the ambient hydrostatic presholes. More particularly it relates to bridging sure in the bore hole. plugs and setting tools therefor that can be run A further object of this invention is to provide into the hole in connection with an electric cable, a new and improved tool for setting a bridging the setting operations being controlled from the plug in a bore hole, which tool can be completely surface. controlled from the surface.

The present invention contemplates providing A Still further object of this inv nti n is t both permanent and retrievable plugs adapted to Provide tti o wh ppli s a c n rolle be set by a novel ot r operated tt n 1 uniform increase in pressure toapacker, insuring which provides an extremely high force for setgood alignment 0f the Parts n a Perfect l ting th packer 1 t plug Th bridging plug between the packer and'the wall of the bore to be and setting tool are lowered into the bore 'hole Packed on an electric cable which not only supports the Further objects and novel features will become weight f the apparatus but also enables the m apparent from the following detailed discussion in the setting tool to be energized from a source of the acmmpanymg drawings. in which: of electrical energy located at the surface. This Figure 1 is a Partial View in longitudinal section permits complete mace control of the through a borehole showing a setting tool and ratus and enables an indication of the functionbridging plug wnstmcted carding t0 the invening of the bore hole equipment to be obtained. a 905mm the plug is set? Accordingly. it is an ubject of this invention sure 2 is a .view in longitudinal section to provide a new and improved apparatus emthrough setting tool and retrievable type or ploymg an electric came for positioning a bad? bridging plug constructed in accordance with the ing plug in a bore hole. i'f h It is also an object of this invention to provide gun a is an enlarged View in longltudmal drilled through when it is no longer needed.

Another object of this invention is to provide aligning: 2:2 and looking in the dia bridging plug in which the packer can be very F gure 2c is an enlarged view in longitudinal $3 2 expanded mm engagement mm the section of the upper portion of the plug and the Another object of this invention is to provide ggga g ggzggg a gg fig s ig: a bridging plug which may be retrieved from the released from the plug.

bore hole after it has served its purpose. I

A further object of the invention is to provide 5: 1? 2: is fi 2 3 g? tg a settin tool which is released from the bridgln n we e 3 3 cally to show the grooves therein.

plugwhenapredetermined setting force has been we 3 is a schematic wiring diagram obtained.

- trating the e ui ment and control a aratus Another object of this invention is provide therefor g single conductor 2;

a setting tool whichprovides a known force to figure 4 is a View in longitudinal section set a bridging P1113111 bore through a permanent type of bridging plug;

Still another object 0: this invention 18 to pro,- pl 5 is a w m longitudinal section vide plug setting apparat includlns means through a modified permanent type oi bridging whereby the force applied in setting a bridging ping;

P g in 11016 is ll indicated at Figure 6 is a schematic wiring diagram illusthe surface. trating a modified circuit employing a three con- An obiect of this invention is to provide a setcable: and tin: tool of the above character which may he mm 7 illustrates a further modification of released from the bridging plus in] the operator th invention. at e, whereby the operator can set the plug Figure 1 illustrates the arrangement of parts to any desired degree and then release the setin a. typical assembly and comprises a bridging ting tool. plug l0 attached to a setting tool i i above which A further object of the invention is to provide may be positioned a jarring assembly l2, all of a bridging plug and a setting tool therefor which which are lowered into a cased bore hole I! by cannot be prematurely set and whose operation an electric cable II, which is manipulated by a winch ii at the surface. The jarring assembly I2 is sometimes used when loosening a retrievable type of bridging plug. It may be of any conventional type and forms no part oi the present invention. The action of the jarring assembly i2 is simply to impart a hammering action after the slips of the plug I6 have been released from the casing, as will be more fully explained in connection with the subsequent figures. A jarring assembly is not normally included in the assembly when the bridging plug I6 is being run into the hole.

In Figure 2 are shown the setting tool H and the plug I6 in its initial unexpanded position. The setting tool ll comprises a tubular housing 26 filled with an incompressible fluid 26', such as oil, for example, within which is mounted an electric motor 2|. The motor 2| is of any conventional type but should preferably be capable of developing a high torque. When a single conduotor cable is employed to lower the equipment into the bore hole, as shown in Figure 3, the motor M is preferably of the series type, which develops a very high starting torque. If a three conductor cable is employed, as shown in Figure 6, the motor 2| is preferably an induction motor.

A reduction gear box 22 is operatively connected to the shaft of motor 2|, serving to reduce its speed of rotation and increase the torque developed thereby. The gear ratios in the box 22 will, of course, depend upon the speed of the motor 2| and the desired output speed, but the reduction ratio will preferably be quite high, 100 to 1 or more, permitting a very high torque to be available from a relatively small motor. A Sylphon bellows 23, communicating with the bore hole fluid L through a passageway 24 formed at any convenient location in the housing 26 serves to maintain pressure equilibrium between the bore hole fluid L and the fluid 26 in the housing 26. Conventional guide springs 25 are attached to the periphery of the housing 26 and serve to prevent it from rotating during the setting or retrieving oi the bridging plug I6.

The output shaft 22' of the gear box 22 is connected to a member 26, which passes through a partition 21 in the housing 26 and through a packing gland 26 and a packing nut 29. The packing gland 26 and packing nut 28 may be of the low pressure variety, as there will normally be very little pressure difference between the inside and the outside of the housing 26. due to the presence of the Sylphon bellows 23. 0bviously, the Bylphon bellows 23 could be eliminated by providing a high pressure type packing instead of packing gland 23; but as high pressure packings produce a very high friction against the rotating member 26, the arrangement shown in Figure 2 is preferred.

At the lower end of the member 26 is formed an enlarged portion 36 having an axially threaded bore 3| therein within which is adapted to be received a threaded rod 32 secured to the bridging plug 16 below. The lower end of the bore 3| is funnel-shaped as at 33 (Fig. 2a) to facilitate the entrance of the rod 32 into the bore 31. Two pins 34 urged downwardly by springs 36 are positioned in longitudinal bores 36' formed in the lower end 36 of the member 26, the upper ends of the springs 35 being secured within the enlarged portion 36 of the member 26. The pins 34 cooperate with arcuate slots 31 having inclined bottoms formed in a laterally extending member or nut 36 (Figures 2b and 2d) which is threaded on the rod by the member 26 isreversed. The

asoavoe 32. The pins 34 and the slots 31 comprise a unidirectional clutch arrangement such that when the member 26 is rotated in one direction, clockwise, for example, the nut 36 is rotated in the same direction; but if the direction of rotation of the member 26 be counter-clockwise, the nut 36 does not rotate. The top end of pins 34 are temporarily secured to springs 36 such as by soldering or frictional engagement. The upper ends of springs 36 are secured to the top of bores 36' in any suitable way to prevent the pins 34 and springs 35 from falling out when the setting tool is removed from the bore hole. This construction permits removal of the entire setting tool, as will be subsequently explained.

A second set of slots 38 is formed on a diii'erent radius in the nut 36 and have their bottoms inclined in the opposite direction so that if the pins 34 are removed and the setting tool it then provided with pins 34' similar to the pins 34, which cooperate with the inclined slots 33 (Fig. 2d), the direction of rotation imparted to the nut 36 Pins 34 and 34' coact with the slots 31 and the slots 36, respectively, but never coact with both sets of slots at the same time. The above described pin and slot arrangement provides a unidirectional clutch, or ratchet, either. direction. The clutch functions to transmit rotation in only one direction during any one trip of the device into the bore hole. If the threads on the support 46 are right-hand threads, the pins 34' coact only with the slots 36, thereby imparting only counter-clockwise direction to the nut 36 to permit contraction of the plug. In like fashion, the pins 34 coast with the slots 61 and impart only clockwise rotation to the nut 36 when the plug is to be expanded in the bore hole.

The bridging plug I6 is of the retrievable type and it comprises a central rod 46 of enlarged diameter (Fig. 2a) integral with the lower end of the threaded rod 32, on which central rod is mounted a flexible packing member 4|. For the sake of clarity this central rod 46 will hereinafter be referred to as a packer support, or support. The packing member 4| is adapted to be compressed into engagement with the bore hole casing by

retainers

42 and 43 slidably mounted on the support 46 at its upper and lower ends respectively, and which are slidably mounted on opposite ends of the support 46 and are adapted to be forced toward one another in a manner well known in the art by the combined action of

conventional slips

44 and 46, keyed, preferably by means of T-shaped keys and key slots, to irusto-conical or tapered expanding

members

46 and 41. The upper frusto-conical member 46 is held against rotation relative to the tubular housing 26 by a plurality of guide pins 33, which are threadedly secured to the housing 26 of the setting tool II and which have a sliding fit in holes 46 formed in the upper face of the expanding member 46. A ball orroller thrust bearing 43 is inserted between the lower face of disc 36 and the upper face of the member 46 to reduce the friction between them.

A small compression spring 56 is interposed between the lower end of tapered member 46 and a shouldered portion 46"formed in the retainer 42. A similar compression spring 6! is interposed between a shouldered portion 41' formed in the retainer 43 and the tapered member 41. The tapered member 41 includes a frustoconical sleeve 41c that is supported on and fixed which may be set to act in l with relation to a shaft 4'": having a laterally.

extending disc-like stop member 41c on its lower and. The shaft 41b is secured to the lower end of the support 40. The action of the two coil springs and Si maintains the assembly in its unexpanded position as shown in Figure 2. The natural elasticity of the packer 4i also assists in maintaining the assembly in its unexpanded position when being raised or lowered in the bore hole. Guide pins 52 and 53 may be inserted between

theretainers

42 and 43 and the

slips

44 and 45, respectively, to prevent all parts oi the plug' ill from rotating relative to the housing 20 when the motor 2| of the setting tool Ii is energized. The guide pins 53 and cooperating slots 53' should preferably be T-shaped so that the slips 45 will be maintained against the retainer 43. Any other suitable means may be used for this purpose. Any suitable safety measures may be provided; for example, the rod 3! may be reduced in cross-section as at 32', in order that it may be broken, if necessary, by tension applied through the cable.

A typical electric circuit that can be utilized with a single conductor cable is shown schematically in Figure 3. It comprises essentially a source of direct current 60 connected through an ammeter 6i and a rheostat 82 to the central terminals 63a and 83b of a double-pole, double-throw switch 63. In order to permit reversal oi the direction of the current flowing to the bore hole equipment, the tgrmlnals 64 and N of the switch 63 are connected together and to the single conductor cable 14 going into the bore hole, while the terminals 56 and 61 are connected together and to the metallic sheath of the cable or to a. suitable ground.

The lower end of the cable I4 is connected to one of the terminals of the iield winding 2i! oi the motor 2i, the other terminal of which is connected to a central terminal 88 on a doublepole, double-throw; relay type switch II. The lower end of cable i4 is also connected to one terminal of the energizing solenoid 69 of the relay Hi, the other terminal of which is connected to the cable sheath or other ground in the bore hole. One terminal of the armature Ila oi motor ii is connected to the terminals II and 12 of the relay switch 10, while the other armature terminal is connected to the

terminals

13 and 14, as is apparent from Figure 3. The other center terminal ll of the relay switch 10 is connected to ground. The'relay switch I! is preferably of the polarized type, but it may be of any variety which will accomplish interchanging the armature or the field leads when the direction of the current flow through the cable I4 is reversed.

In operation, the parts are assembled at the surface as shown in Figure 2 and attached to the electric cable in the conventional manner. The winch i5 is rotated and the bridging plug ill and setting tool assembly il lowered to the desired depth in the bore hole. The switch 83 (Figure 3) is closed, thus energizing the motor 2| of the setting tool ii. As the setting tool housing 2|) is held from rotation by the guide springs 25, the motor 2i, acting through the reduction gear assembly 22 and the member 26, rotates the nut 36 threading it downwardly along the threaded rod 32 the bridging plug Iii. As the nut as threads downwardly alo e e rod 3 the two

tapered members

48 and 41 are forced toward one another, moving the

slips

44 and 45 into engagement with the casing (not shown). Continued rotation oi the motor 2| compresses the flexible packing member 4! longitudinally and forces it into engagement with the casing (not shown). The teeth on

slips

44 and 45 are faced such that the two

slips

44 and 45 move toward one another relatively easily, but the reverse action is essentially prevented.

As the packer H is being expanded into engagement with the casing (not shown), the load upon the motor 2i increases. Hence, it draws an increased amount of power, which is indicated on the ammeter 61 of Figure 3. By suitable calibration oi the surface indicating instrument, the progress and stage 01' the setting operation are continuously indicated.

The motor II is maintained energized until the desired setting torque is being supplied to the bridging plug III, as indicated by the surface instrument Si, or until the motor 2| stalls. The surface switch 83 is then thrown to the opposite position, thereby reversing the direction of rotation of the motor 2|. when this condition obtains, the clutch assembly, comprising the pins 34, inclined grooves 31 in the nut 38, slips. unthreading the member ill from the threaded rod 32 of the bridging plug it. It should be emphasized that the nut 36 remains in its tightened position, positively preventing release of pressure from the bridging plug ill. After the setting tool H has been completely disconnected from the bridging plug iii. the setting tool Ii and supporting cable may be removed from the hole.

After the bridging plug has served its useful purpose. it may be retrieved from the bore hole by removing the clutch pins 34 from the bores 35' and securing the pins 34' within other bores 35" closer to the center of the enlarged portion 30 on the member 28 (Fig. 2c) and lowering the setting tool ll into the hole on the electric cable. As the bridging plug I0 is symmetrical and generally rather long in comparison to its diameter. 7

the upwardly extending threaded rod 32 will be very near the axis of the casing. The guide springs 25 on the setting tool I I also serve to keep it centered in the hole. Consequently, the (unnelled portion 33 of the member 30 in the setting tool II will pass over the upper end of threaded rod 32 and align the two axially.

The surface switch 63 is then thrown to the position for setting the plug, causing the member 26 to be threaded along rod 32 until the clutch pins 34' enter the inclined grooves 38 in the nut 36. When that occurs, the direction oi rotation of the motor ii is reversed, causing the nut 38 to be threaded upwardly along the threaded rod 32, thereby returning the bridging plug in to the position shown in Figure 2.

Due to the extreme biting action between the slips 4| and 45 and the casing. or due to a partial vulcanizing oi the packer 4i against the casing, the plug it may not be completely released from the casing. In such case, a pull on the supporting cable usually releases the plug iii. If it does not. a jarring member I! (Figure i) can be positioned above the setting tool ii to impart a jarring action to the released plug Ill. The compression springs iii and Si insure that the bridging plug ill will contract uniformly and properly when released.

A permanent type plug Ili' which is set by the same setting tool II is shown in Figure 4. This plug is similar in many respects to the one described in connection with Figure 2, the most notable exception being the direction of the taper on-the two tapered members which expand the slips. In this embodiment, a flexible packing member ll 15 positioned about a support 48 between two retainers l2 and 42. A key 88 is formed on the upper reduced portion 48' of support l8. just below the threaded portion 32. The ke 85 cooperates with a keyway 81 formed in the upper tapered member 88, preventing relative rotation between the two. The plug I8 is'provided with an upwardly and inwardly tapering expanding member 88 and a downwardly and inwardly tapering member 89, which members are adapted to cooperate with similarly tapered slips 88' and 88' to expand the packing member ll into engagement with the bore hole casing. The slips 88' and 89' may be retained initially in their contracted position as shown by any suitable means, as, for example, by passing small coil springs or pieces of

wire

81 and 88 through holes 88 and I88 in the slips 88' and 88', respectively. Above the slips 88' is disposed a laterally extending member or disc 88 through which force may be transmitted from the disc 28 to the slips 88.

The lower expanding member 88 i slidably supported on the shalt 88a 01 the laterally extending stop member 88b which is secured to the end oi the support 48.

In operation. the permanent plug I8 of Figure 4 is very similar to that described in Figure 2. The action of the setting tool II causes the nut 38 to be threaded downwardly along the threaded rod 32, forcing the slips 88' and 88' into engagement with the casing (not shown). Further rotation of the nut 38 forces the two tapered expanding

members

88 and 88 toward one another, thereby compressing the packing member ll and causing it to expand laterally into engagement with the casing. In this embodiment, it will be noted that if either end of the bridging plug I8 is subjected to excessive pressure or other force, the plug I8 will be set tighter in position. Ac-

cordingly, a plug is provided which does not tend to slide up or down the casing when force is applied to it after the setting has been completed. Inasmuch as all parts of the plug I8 are designed to have a considerable cross-sectional area, the plug I8 has sufficient strength to enable it to function properly even when made of cast iron.

or other material that can be easily drilled.

Figure 5 illustrates a modified type of nonretrievable bridging plug II" in which the packer is partially expanded into engagement with the casing before both sets of slips contact the easing, and also one in which "the bridging plug is positively held in retracted position during the descent by shear pins or screws. This form is similar to the embodiment shown in Figure 4 except that the slips 88' are secured to the tapered expanding member 88, by screws or other suitable securing means 88 that can be readily sheared oil. In addition, downward movement of the support 48 is prevented by ratchet teeth 95 formed on the upper reduced portion l8" oi the support 48, which is adapted to cooperate with a pawl 86 secured within the tapered expanding member 88. The pawl 85 is normally maintained in engagement with the ratchet teeth 95 by means or a conventional leaf spring 88',

In operation, the bridging plug I8" is run into a hole attached to the setting tool II. The motor of the setting tool is energized, causing the disc 88 to be threaded downwardly along the rod 82. The relative motion between the nut 38 and the rod 22 causes the stop member 89b of the ascents the slips 88' to bite the casing. Continued rotation or the nut 88 along the threaded rod 22 causes the flexible packing member I to be partially expanded, the pawl and ratchet

mechanism

88 and 88 looking the assembly in the expanding positions as the setting proceeds. When additional force is applied to the disc 88, and hence to the slips 88', the screws 84 are sheared, permitting the slips 88' to travel easily along the tapered member .8. Continued rotation of the nut 88 forces the upper slips 88' into engagement with the casing and completes the expansion .0! the packer ll.

It will-be noted that at the beginning of the setting operation, the power delivered to the motor 2i will be relatively small, as no great load is imposed upon it. As the lower slips 88' begin to contact the casing and the packer ll begins to expand, additional work will be required or the motor 2| with a corresponding increase in the reading or the surface instrument 8i. When the screws 84 shear, the torque required from the motor will be greatly reduced, with an attendant sudden drop in the energy being sent from the surface. As the setting operation proceeds, the current will again rise to a maximum value when the plug I8" is set. Thus, the various operations of the setting of the plug will easily be discerned by noting the readings of the ammeter ii.

In the event it is desired to use a multi-conductor cable, for example, a three conductor cahis, the circuit shown in Figure 6 may be employed. As shown in the figure, electric power is supplied from any suitable three phase supply a, b. c, by means of the conductors 88a, 88b, and 880, through a switch 88 to a double-pole, doublethrow reversing switch 82 at the suriace. The Iunction of the switch 82 is to reverse the leads 88a and 88b in the three phase system. Threephase power is supplied through the leads 88a, 88b, and 880 in the supporting cable (not shown) to a three phase motor 2| in the bore hole. By manipulating the switch 82, the motor 2i may be made to rotate in either direction to perform the functions described above.

Figure '2 illustrates an'embodiment of the invention which is designed to provide a known predetermined force for setting the plug. Reierring to Figure '7, the housing 28 is provided with a transverse member I8I having a central aperture I82 through which the rod 22 extends. Rotation of the rod 22 with respect to the housing 28 is prevented by a key I88 on the transverse member I8I which cooperates with a keyway I88 on the rod 22, so that the guide springs 28 shown in Figure 2 may be eliminated. Spacers I88 formed integrally with the housing 28 serve to maintain a hired distance between the member 88 and the irusto-conical or tapered member 48, and a ball or roller thrust bearing 48 is disposed between the member 88 and the transverse member MI.

The lower portion oi the rod 82 is provided with a buttress thread I88 and extends through a similarly threaded split nut IN, the parts oi which are maintained in a recess I88 in the tapered member 48 by a plurality oi spring members I89 secured to the spacers I88. The split nut I81 is preferably made in three or more parts. The rod 82 is also provided with a weakened portion 82' which is designed to break when the the gear box 22.

ceeds the force required to expand it fully into packing position.

In setting the plug lll', the motor 2| (Fig. 2) is energized and drives the member 30 through This causes the rod 32 to move upwardly with respect to the housing Ill, thereby raising the segments of the split nut llll against the spring members I09 until they have suflicient room to jump down one thread on therod 32. The nut I01 and the rod 32 thus form a nut and ratchet mechanism. After the packer II has been fully expanded, continued rotation of the member 30 breaks the rod 32 at the weakened portion 32', thus preventing damage to the bore hole casing or the packer material from excess pressure.

It will be noted that even if an undue load is thrust upon the motor 2! by sand or other foreign matter getting into the equipment, force will be applied to the packer 4| until the rod 32 breaks so that the packer ll will be set properly.

Inasmuch as bridging plugs are generally set in the cased portion of a bore hole, the invention described in the foregoing specification has been illustrated as applied in cased holes. It is to be understood, however, that the equipment is equally applicable to operations conducted in the uncased portion of a hole. It is also within the purview of one skilled in the art to suspend the above described bridging plugs and setting tools by means of drill pipe or tubing, the electrical conductor for controlling the operation of the equipment being lowered through or alongside the pipe; so while several specific embodiments of the invention have been described above in detail, these are intended to be illustrative and not restrictive, and they are susceptible of numerous changes in form and detail within the scope of the following claims.

I claim:

1. A bridging plug for'use in bore holes, comprising a support adapted to extend longitudinally in a bore hole, a sleeve of flexible material mounted on the support, upper and lower sleeve retaining members slidably mounted on the support, an upwardly and inwardly tapered member secured to said support at the lower end thereof, a downwardly and inwardly tapered member movably mounted on said support at the upper end thereof, a plurality of slips mounted between said tapered members and said upper and lower sleeve retaining members, respectively, said slips being adapted to slide longitudinally and laterally relatively to the said tapered members, and means for moving said support relatively to said upwardly tapered member. 4

2. A bridging plug for use in bore holes, comprising a support adapted to extend longitudinally in a bore hole and having a laterally extending stop member formed at the lower extremity thereof, a packing member mounted on the support, upper and lower packing member retainers slidably mounted on the support. a downwardly and inwardly tapered member slidably mounted on said support, a plurality of slips slidably mounted between said tapered member and the laterally extending member on the support, an upwardly and inwardly tapered member slidably keyed to the upper end of said support, a second laterally extending member slidably mounted on said support above said upwardly and inwardly tapered member, a plurality of slips slidably mounted between said second laterally extending member and the upwardly and inwardly tapered member, and means for moving said support relatively to said last named laterally extending member.

3. A bridging plug for use in bore holes, comprising a support adapted to extend longitudinally in a bore hole and having a laterally extending stop member formed at the lower extremity thereof, a packing member mounted on the support, upper and lower packing member retainers slidably mounted on the support, a downwardly and inwardly tapered member slidably mounted on said support, a plurality of slips slidably mounted between said tapered member and the laterally extending member on the support, an upwardly and inwardly tapered member slidably mounted to the upper end of said support, a second laterally extending member slidably mounted on said support above said upwardly and inwardly tapered member, a plurality of slips slidably mounted between said second laterally extending member and the upwardly and inwardly tapered member, means for securing said last-named slips temporarily to said upwardly and inwardly tapered member, and means for moving said support relatively to said second laterally extending member.

4. A bridging plug for use in here holes. comprising a support adapted to extend longitudinally in a bore hole and having a laterally extending stop member formed at the lower extremity thereof, a packing member mounted on the support, upper and lower packing member retainers slidably mounted on the support, a downwardly and inwardly tapered member slidably mounted on said support, a plurality of slips slidably mounted between-said tapered member and the laterally extending member on the support, an upwardly and inwardly tapered member slidably mounted to the upper end of said support, a second laterally extending member slidably mounted on said support above said upwardly and inwardly tapered member, a plurality of slips slidably mounted between said second laterally extending member and the upwardly and inwardly tapered member, means for securing said last named slips temporarily to said upwardly and inwardly tapered member, means for moving said support relatively to said second laterally extending member, and means for preventing movement of said support in one direction relatively to said second laterally extending member.

5. In apparatus for plugging a bore hole, the combination of a support adapted to extend longitudlnally in a bore hole, said support having a threaded portion at the upper end thereof, an upwardly and inwardly tapered member secured at the lower end of said support, a packing member slidably mounted on said support above said tapered member, resilient means urging said tapered member away from said packing member, slip means mounted between the lower end oi said packing member and said tapered member, and adapted to slide on said tapered member, a downwardly and inwardly tapered member slidably mounted on said support above said packing member, resilient means urging said downwardly and inwardly tapered member away from said packing member, second slip means mounted between the upper end of said pac member and said downwardly and inwardly tapered member and adapted to slide on said downwardly and inwardly tapered member, a nut threaded on said threaded portion of the support above said downwardly and inwardly tapered member, a reversible electric motor for turning the nut on said support, unidirectional clutch means disposed be-, tween said motor and nut, a source of electrical,

energy at the surface of the earth, electric circuit means connecting said source and motor, and switching means associated with said circuit means for controlling the direction of rotation of said motor.

6. In apparatus for plugging a bore hole, the combination of a support adapted to extend longitudinally in a bore hole, said support having a threaded portion at the upper end thereof, laterally extending stop means secured at the lower end of said support, a packing member slidably keyed to said support, said packing member having downwardly and inwardly and upwardly and inwardly tapered members at the lower and upper ends, respectively, slip means mounted between said stop means on the support and said downwardly and inwardly tapered member and adapted to slide on said downwardly and inwardly tapered member, a laterally extending member slidably mounted on said support above said packing member, second slip means mounted between said laterally extending member and said upwardly and inwardly tapered member and adapted to slide on said upwardly and inwardly tapered member, a nut threaded on said threaded portion oi the support above said laterally extending member, an electric motor for turning said nut on the support, unidirectional clutch means between said motor and nut, a source of electrical energy at the surface of the earth, electric circuit means connecting said source and motor, and switching means associated with said circuit means for controlling the direction of rotation of said motor.

'7. In apparatus for plugging a bore hole, the combination of a support adapted to extendlongitudinally in a bore hole, said support having a threaded portion at the upper end thereof, laterally extending stop means secured at the lower end of said support, a packing member slidably mounted on said support, said packing member having downwardly and inwardly and upwardly and inwardly tapered members at the lower and upper ends, respectiveh', slip means mounted between said stop means on the support and said downwardly and inwardly tapered member and adapted to slide on said downwardly and inwardiy tapered member, a laterally extending member slidably mounted on said support above said packing member, second slip means mounted between said laterally extending member and said upwardly and inwardly tapered member and adapted to slide on said upwardly and inwardly tapered member, shearabie means for temporarily securing said second slip means to said upwardiy and inwardly tapered member, pawl and rack means for preventing relative movement in one direction between said support and upwardly and inwardly tapered member, a nut threaded on said threaded portion of the support above said laterally extending member, an electric motor for turning said nut on the support unidirectional clutch means between said motor and nut, a source or electrical energy at the surface of the earth, electric circuit means connecting said source and motor,'and switching means associated with said circuit means for controlling the direction of rotation of said motor.

8. An apparatus for plugging a bore hole, comprising a support adapted to be disposed longitudinally of a bore hole and having a threaded upper end portion, a radially expansible packing aseavee member mounted on said support, a nut member threaded on said threaded portion and movable toward said packing member for expanding the latter radially, electric power means detachably connected to said support for rotating said nut, and means actuated by said power means for connecting said power means to said support and detaching said power means from said support.

9. An apparatus for plugging a bore hole comprising a support adapted to be disposed longitudinally of a bore hole and having a threaded end portion, radially contractable and expansible packing means mounted on said support, a nut threaded on said threaded end portion and movable axially of said support to expand said packing member, a casing containing a reversible electric motor, threaded means driven by said motor engageable with said threaded portion to detachably connect said casing to said support. and unidirectional clutch means connecting said nut and said threaded means, whereby said packing member can be expanded and said casing and said support disconnected by said motor.

10. In apparatus for plugging a bore hole, the combination of a support adapted to be disposed longitudinally of a bore hole, said support having a threaded portion at the upper end thereof, a radially expansible. packing member mounted on the support, a nut threaded on said threaded portion of the support, means actuated by said nut for expanding said packing member, reversible electric power means for turning said nut on the support, a source of electrical energy for said power means, an electric circuit connecting said source to said electric power means, and means for controlling the direction of rotation of said electric pbwer means.

11. In apparatus for plugging a bore hole, the combination of a support adapted to be disposed longitudinally of a bore hole, said support having a threaded portion at the upper end thereof, a packing member mounted on said support, radially movable slip means slidably mounted on said support below the lower end of said packing memher, a second radially movable slip means mounted on said support above said packing member, a nut threaded on the threaded portion of said support above said second slip means and movable axially of said support for moving said slip means radially and expanding said packing member, a reversible electric motor for turning and moving said nut axially of said support, unidirectional clutch means disposed between said motor and said nut, a source of electrical energy at the surface of the earth, electric circuit means connecting said source and motor, and switching means associated with said circuit means for controlling the direction of rotation of said motor,

12. In apparatus for plugging a bore hole, the combination of a support adapted to be disposed longitudinally of a bore hole, said support having a threaded portion at the upper end thereof, laterally extending stop means secured at the bottom end of said support, an expansibie and contractable packing member slidably mounted on said support, said packing member having downwardly and inwardly and upwardly and inwardly tapered members at its lower and upper ends, respectively, radially movable slip means mounted between said stop means and said downwardly and inwardly tapered member and adapted to slide on said downwardly and inwardly tapered member, a second member slid-- ably mounted on said support above said packing member, radially movable slip means mounted between said second member and said upwardly and inwardly tap red member and adapted to slide on said upwardly and inwardly tapered member, a nut threaded on said threaded portion of the support for moving said second member axially oi said casing. an electric motor for turning said nut on the support to move said nut axially oi said support and move said slip means radially. unidirectional clutch means connecting said motor and nut. a source oi electrical energy at surface of the earth, electric circuit means connecting said source and motor, and switching means associated with said circuit for controlling the direction of rotation of said motor.

13. Apparatus for setting in a bore hole a bridging plug having a rotatable clutch element mounted on a threaded support for expanding a packing member, comprising a housing adapted to be lowered into a bore hole, a member rotatably mounted in said housing and having threads engageable with said threaded support and adapted to extent longitudinally in a bore hole, means mounted on the housing ior maintaining the axis of the housing parallel to the axis oi the bore hole, a clutch element in said threaded member for cooperation with the rotatable clutch element of said bridging plug, electric power means mounted in the housing for turning said threaded member about its axis, and means for controlling the direction of rotation 01' said electric power means.

14. Apparatus for setting in a bore hole a bridging Plug having a rotatable clutch element mounted on a threaded support for expanding a packing member, comprising a housing adapted to be lowered into a bore hole, means for maintaining the axis of the housing parallel to the axis of the bore hole, a downwardly extending, rotatable member journaled in said housing and having threads engageable with said threaded support, a reversible electric motor in the housing ior turning said threaded member about its axis, a clutch element on said threaded member for cooperation with said rotatable clutch element, and switching means ior controlling the direction of rotation of said motor.

15. Apparatus for setting in a bore hole a bridsine plug having a rotatable clutch element mounted as a threaded support tor expanding a member, comprising a housing adaptedtobelower'edintoaborehole.anincompressible fluid in the housing. means for equalising the fluid pressures inside and outside of said housing. a downwardly extending rotatable member iournaied in the housing and havin threads engageable with said threaded support, a clutch element on said rotatable member cooperable with said rotatable clutch element, a

reversible electric motor in the housing for turnin: said threaded member about its axis, and switching means associated with said circuit means for controlling the direction of rotation of said motor.

18. A brid in plug for use in bore holes comprising a support adapted to extend longitudipally in a bore hole, a radially expansible sleeve of flexible material on the support, upper and lower retaining members for the sleeve, a irustoconical expanding member secured at the lower end of said support, a second irusto-conical expanding member movably mounted at the upper end of said support or movement axially of said support to compress said sleeve axially and expand it radially. a plurality of slips slidably secured to said frusto-conical members. means hicluding a rotatable member mounted on said support or movement axially of said support in response to relative rotation between said member and said support (or moving said support relatively to said second expanding memher, and a clutch element on said rotatable member for connecting said member to a source of power and disconnecting said member from said source oi power.

17. In apparatus for plugging a bore hole, the combination of a support adapted to extend longitudinally in a bore hole, said support having a threaded portion at the upper end thereof and stop means at its lower end, a radially expansible packing member mounted on said' support. slip means slidably mounted on said support between the lower end of said packing member and said stop means, second slip means mounted on said support above said packing member, a nut threaded on the threaded portion of said support above said second slip means, a reversible electric motor (or turning said nut on said support, unidirectional clutch means disposed between said motor and said nut, a source or electrical energy at the surface oi the earth,

electric circuit means connecting said source and motor. and switching means associated with said circuit means tor controlling the direction of rotation of said motor.

mm B. STEWARD.