US2180680A - Casing head for pressure drilling - Google Patents

Description

NOV. 21, 1939. r I H|LD 2,180,680

CASING HEAD FOR PRESSURE DRILLING Filed Nov. 2, 1936 s Sheets-Sheet 1 Nov. 21, 1939. F, w, HM, 2.180580 CASING HEAD FOR PRESSURE DRILLING Filed Nov. 2, 1936 5 Sheets-Sheet 2 46 fl 7 20 5 C 5; 6! 16 5 jg a x x 36 467 42.

Nov. 21, 1939. F. -w. HILD 2,180,680 I CASING HEAD FOR PRESSURE DRILLING Filed Nov. 2, 1956 5 Sheets-Sheet 3 65 i i 6 -x E i x-gQf r: l i w 84 I 9e Nov. 21, 1939.

F. w. HILD I 2,180,680

CASING HEAD FOR PRESSURE DRILLING Filed Nov. 2, 1936 5 Sheets-Sheet 4 Nov. 21, 1939. F. w. HILDA 2.130580 CASING HEAD FOR PRESSURE DRILLING Filed Nov. 2, 1936 5 Sheets-Sheet 5 f Q X 14 Juan/WM 39 j I i 32% MM Patented Nov. 21, 1939 UNITED STATES PATENT OFFICE 2,180,880. CASING mam FOR rims'smm anama Frederic W. Hiid, Los Angeles, Calif. Application November 2, 1936, Serial No. 108,777

11 Claims.

My invention relates to equipment for placing and supporting the several casings in gas and oil wells, and pertains more particularly-to the supporting heads for the casings and to a novel method of landing and securing the casings and the heads in place duringfluid pressure conditions. I

Various forms and arrangements of casing heads for well casings have been proposed and used, but all of them require absence of fluid pressure at the heads whenlanding or securing them in position. Therefore the hole is usually filled with mud fluid of sufiicient density to kill the well and prevent flow from pressure formations during the period of landing and securing the casings. Obviously all of these forms require removal of the well control column comprising the master valve and the blowout preventer in order to secure and seal the upper end of the casing to the casing head.

But reliance upon mud fluid alone to hold the well pressure often has proved inadequate and dangerous and has resulted in some costly blowouts. Itisan object of my invention to provide a casing head having means for sealing against the casing or the casing terminal collar before removal of the well control column. Another object is to seal the casing with respect to the casing head before securing them to each other. The present invention provides a method and suitable equipment for placing casings and securing them together in a live well or during pressure flow of fluid therefrom. The economic importance and value-of this tothe petroleum industry may be seen upon consideration of the following: Experience has shown that most oil fields have several producing strata. But on account of the limitations of the casing head equipments, thepresent well practice has been based on producing from only one of the severalstrata Sometimes this formation may be abandoned for a lower sand; this requires drilling deeper. Occasionally a known upper producing sand may be utilized by plugging back which involves cutting and rearranging, the casings inthe well; but

. owing to the discouraging uncertainties involved v in this, such undertakings are quite exceptional.

.In addition to the diillculty and uncertainty of making a good pack ofiin the right place, there is the probability of little or no production-due of underground fluids 'to hand intrusion'during the drilling'period and I thereafter; and also to the-'nugratory character I ,hand the teethfof the i"slips must'cut I t e producer each productive rolfmatiqn a it v dent g: @3915 tne casing which accord ngly is encountered and also enables him to utilize in a single well any or all of the several producing sands, at the same time. Thus on drilling a well to the first upper sand, the producer may set a casing and flow the production through the intercasing space, and while it is flowing he may drill on down to the next pay sand, and bring this in similarly; and so on downward to the other productive horizons.

a Manifestly by means of the present invention the'cost of drilling for oil and gas will be greatly reduced. Also the output per well in a field of multiple sands will be vastly increased. Moreover it will not be necessary to defer for an indefinite later time the endeavor to obtain fluid from another sand, which may then prove abortive. The invention provides other advantages. It is well understood that a minor portion of the weight of a string of casing may be borneby its lower-end and that the major portion should be suspended from the terminal collar at the upper end. The lower end of the casing string is therefore in compression and the upper part is in tension. It is important to suitably apportion these loadings, and to hold the casing straight in the hole.- For supporting the upper part of the easing each casing head 'of the usual type contains a terminal collar which either is threaded onto the casing at the-top, or else'is a set of serrated slips which grip the casing. In both types, the

seated position of the terminal .collar in the cas- But it necessitates quite accurate knowledge of the location of the bottom end of the casing and also that the final upper joint of easing be cut and threaded to exact length. v I

I The tapered slip type of terminal collar enables lifting or stretching the casing to the desired tension as it is landed infthe slips, after which the casing is'cut oiT flush at the top of the casin hea Thus it is. less dependent upon accurate knowledge of casing point or upon the exact length of the inn r "joint; On the other the e'quivae is subjected to combined crushing and tensile stresses continuously. Moreover movement or changeof position due to well disturbances is more likely with this type than with the threaded type.

It is an object of my invention to provide a casing head having a terminal collar which may be threaded or welded to the final joint of casing and which provides a substantial range of vertical position for the terminal collar, so that the casing may be stretched through said range to the desired tension.

For forcing pipe into a well against pressure, suitable snubbing equipment is essential. The present invention includes a unique yet 'very simple hydraulic snubbing jack capable of snubbing into or out of the well some 45 to 80 feet of drill pipe without stopping, and with only one grasping of the drill pipe.

Other objects and advantages of my invention will be apparent from the following description and the accompanying drawings:

Figure 1 shows the equipment embodying the invention installed in a derrick.

Figure 2 shows in part section the casing head assembly for several concentric casings.

Figure 3 is a view in horizontal section taken on the line 33 of Figure 2.

Figure 4 shows a slip head and slips in a rotary drilling machine for holding drill pipe against vertical movement.

Figure 5 shows the snubbing jack locked to the slip head of Figure 4.

Figure 6 is a horizontal section taken on the line 6-6 of Figure 5.

Figure '7 is a longitudinal section on line 1-1 of Figure 5.

Figure 8 shows in part section the equipment and the first stage of the method for landing casing against well pressure.

Figure 9 shows in part section the equipment including thelanding tool in the later stage of the method for landing casing against pressure.

Figure 10 shows the final stage of the method illustrated in Figures 8 and 9 and shows the casing secured in its casing head.

Figure 11 is a fragmentary view showing an alternative arrangement of a portion of the easing head assembly of Figure 2.

Referring to the drawings, the casings I4 and I5 are suspended from casing head I! while casing I6 is suspended from casing head l8. Superimposed upon these in fluid tight connection are the roller valves l9 and 29, the nipple 2|, flow cross 22, nipple 23 and control head 24 respectively. Above these on the derrick floor beams is the rotary machine 25 which contains the stripper bushing 26, the latter extending into the control-head 24. The last named contains the hollow resilient packer 24a together with a wear packer 24b which bears in sealing contact against the lower part of the stripper bushing 26. The rotary machine and the control head are connected by the expansion joint 21. All of the apparatus-listed in this paragraph with the exception of casing heads I! and 3 are shown and described in my co-pending application Nos. 86,140 and'91,554 filed June 19 and July 20, 1936, respectively.

Secured to the stripper bushing 26 is sliphead 28, and breech locked to the latter is the lower end of snubbing jack 29. The upper end of the snubbing jack is linked onto the hook of traveling block 30 which is suspended from the crown block (not shown) of derrick 3| by means i. 0&-

ble 32. Extending upwardly into snubbing jack, and downwardly through the sliphead, the stripper bushing, the casings, the casing heads and the intervening apparatus is the drill pipe 33 having tool joints or collars 34.

Referring more particularly to Figures 2, 3 and 11, the outermost casing I4 is suitably secured as by welding to the casing head I! which rests upon a suitable foundation, and is the landing and anchorage base of the apparatus and the members superimposed upon it. A pair of vent pipes 35 are threaded into the sides of the casing head for conducting fluid laterally away from casing l4. The upper end of the casing head is flanged radially outward as at 36. The

upper face of the flange is grooved as at 31 to receive a temporary gasket for packing against a control device during drilling such as roller valve l9.

The casing head has a large central bore 38 coaxial with and the same diameter as the inner diameter of easing l4. A groove in the bore 38 contains the hollow resilient expansible packer 39 which may be similar to packer 24a in control head 24, illustrated and described in my co-pending application No. 91,554. The packer 39 when expanded by a suitable pump 39a constiutes an effective, controllable seal against the terminal collar 40 of the next casing l for preventing escape of well fluid from outer casing I4. The

bore 38 is counterbored at the flange 36 to re-- ceive a gasket 4| preferably metallic which is a second seal against terminal collar 40 for the same purpose. The outer surface of the terminal collar is cylindrical and fits metal to metal in the bore 39 of casing head H.

A gland 42 bears against the metallic gasket 4|. The outer cylindrical surface of the terminal collar is recess grooved at 43 to receive the split holding ring 44 which may bear on the gland 42 through shims 45 which may be interposed between the gland and the holding ring, or through the adjusting screw 45a which is threaded through the holding ring. The terminal collar is inner threaded at both ends, the lower end receiving the casing l5 and the upper end receiving the casing head l8. The bolts 46 tie the holding ring 44 to casing head H at flange 38, and prevent radial displacement of the ring. Spacers 46a surrounding the bolts '46 may be interposed between the holding ring and the flange thereby transmitting to the casing head the weight carried by the ring. The adJusting screw 45a bearing on the gland 4| may vary and adjust the packing efiect of gasket 4|.

The collar .40 at the upper end of its upper thread has counterbore 41 which forms a seat for casing head I8. During the drilling stage prior to setting casing head l8, the collar 40 may receive in seat 41 an adapter similar to adapter 48 to which may be secured a master gate or blowout preventer exemplified herein by the roller valve.

The casing head l8 at its lower end 49 is threaded and shouldered to fit snugly into the thread and seat 41 of terminal collar 40 thereby efiecting metal to metal seal against the escape of well fluid from casing l5. A gasket 50 between the seat 41 and the shoulder of easing head l8 provides additional effective seal for the same purpose. The casing head I8 in other respects is similar to casing head I'I. Thus casing head l8 has the lateral vent pipes 5|, the upper flange 52, the hollow packer 53, the metallic gasket 54, the gland 55, the split holding ring 56 and shims 51. Likewise the terminal collar 58 is similar to terminal collar 48. The inner casing I8 is threaded into terminal collar 88 which fits snugly into the central bore of casing head I8, the collar being engaged and held by holding ring 56.

The adapter 48 has the threaded and shouldered lower portion which with suitable gasket flts snugly into the terminal collar 58. The upper portion of the adapter is flanged radially outward and to it may be secured a control device such as roller valve 58.

For setting or cementing casing either in the absence of well pressure or against it, the collar may receive in its upper thread a length of pipe serving as a landing and cementing tool. It is obvious that the arrangement allows considerable range of vertical movement of the terminal collar, the shims 45 and/or the adjusting screw 45a enabling a substantial range.

The stripper bushing 28 in the rotary machine 25 contains the resilient packer 68 through which extends in fluid tight seal the drill pipe 88. The upper part of the bushing 28 forms the radial flange 8| and the taper bored slip bowl 82, the last named being adapted to receive the usual downslips for gripping and holding the drill pipe against downward movement.

Referring particularly to Figures 4, 5, 6 and 7, the sliphead 28 has a body 68 the lower portion of which forms the neck 84, which is bored to fit snugly on the outer cylindrical surface of bowl 82 of the stripper bushing 28. The flanged base 55 of the body 88 radiates outwardly from the lower end of neck 84 and rests upon flange 8| of the stripper bushing, being held firmly thereto by the hold down brackets 88 of the rotary machine 25. A gasket 81 between the flanges aids in making fluid tight the connection of the sliphead 28 to the stripper bushing 28. The upper portion of body 88 forms the female half of breech lock 88 and also the tapered head 88 the latter having a gasket 18 on its external tapered surface.

Within the body 88 are the downslips II and the upslips 12 for gripping the drill pipe. Downslips 'II co-operate with the tapered bowl 82 of the stripper bushing 28. Upslips l2 co-operate with the tapered head 88 the inner surface of which is taper bored to' conform with the slips. For moving the slips into and out of gripping position, duplicate means are provided. Thus slip ring I8 surrounding the downslips 1| has inwardly projecting lugs 14 which engage the downslips II. The slip ring has trunnions 15 which are engaged by the ends of a shifter yoke 18. The yoke is pivoted by means of shaft II in bearings I8 and I8 in the side of body 88. One end of the shaft projects outside the body at bearing 18 and is flat faced to receive a wrench or lever. A closure plug in bearing 18 and a stufling box 88 in bearing I8 prevent escape of fluid but permit rotative movement of the shaft 'I'I. Rotation of the shaft and the yoke imparts vertical movement to the slip ring thereby moving the downslips II into or out of the tapered bowl 82 of the stripper bushing. Likewise by means of shaft 8i with similar yoke and slip ring arrangement, the upslips I2 may be moved vertically into or out of the tapered head 88 of sliphead Sometimes slipheads must be rotated and as all slipheads are subject to vertical thrust in both directions, provision for thrust bearings must be made for such rotative service. Sliphead 28 transmits the thrust to the rotary maand independent shifting to flt on the taper head 58 of sliphead 28; the

bottom of the base forms the male half of the breech lock 88. Thus by setting the snubbing jack on the slip head and giving the jack a quarter turn, both are connected tightly together, the gasket helping to effect fluid tight seal. Within the base 83 is formed the interceptor 84 as part thereof.

The tubular cylinder 82 contains the piston 85 from which are suspended the grab hooks 88.

The piston 85 has the body 81 on which is suitable packing 88 which bears against the inner wall of tubular cylinder 82. Within the piston body are twovopposing valves 88 and 88, urged to their seats by a light spring 8i. Fluid pressure on the upper side of piston 85 tends to open valve 88 and to force valve 88 into its seat. Conversely fluid pressure below the piston acts to open valve 88 and to close valve 88.

The lower portion of piston body 81 forms the shank 82 in which the pin 88 at right angles to the piston axis serves as trunnion for suspending the grab hooks 88. 'Also suspended on pin 88 in a central slot of shank 82, is the valve stem 84 for the valve 88. The valve stem has an elongated slot through which the pin passes such that upward vertical movement of the stem with respect to the piston body 81 will lift valve 88 from the seat and thus open it.

The grab hooks 88- are bored to two diameters thereby forming the shoulder 85 near the lower end, such that the grab hooks may surround the collar or tool joint 84 of the drill pipe 88, the shoulders 85 being adapted to intercept the under shoulder of the tool joint for holding or suspending the drill pipe. The inner lower ends of the grab hooks are flared outwardly. The outer diameter of the lower ends is only slightly less than the inner diameter of tubular cylinder 82, so that when the'grab hooks are closed around the tool joint, the hooks cannot open within the tubular cylinder and cannot release the drill pipe. When the piston 85 approaches its lowest position in the cylinder 82 the lower ends of the grab hooks meet theintercepter 84 in the base 88. The intercepter is so shaped and positioned in the base 88 that the flared inner ends of the grab hooks are the first to meet the interceptor, so that continued downward movement of the piston forces the grab hooks apart away from the drill pipe and tool joint, thereby releasing the drill pipe.

The upper end of the tubular cylinder is closed by the cap 88 which has the bale 81 for linking onto the traveling block 88. A pipe 88 having the valves 88 and I88 connect the base 88 of the snubbing jack to the cap 88. A flexible hose I8I connecting to pipe 88 between the valves leads to a pipe I82 which has a valve I88 and leads to a suitable source of fluid pressure supply such as the boiler feed pump. A pipe I84 having valve I85 connects pipe I 82 to the wellpressure. A valve I88 controls a drain from the base 83. Gages I81 and I88 indicate fluid pressure on either side of piston 85.

When the snubbing jack 29 is not in use, it stands in a. corner of the derrick, the piston 85 being at its lowest position. The valve stem 94 therefore has been pushed upward and the valve 90 is lifted from its seat. The weight of the liquid in the tubular cylinder 82 is ample to overcome the light spring 9| so that both valves being open the liquid drains out of the snubbing jack.

During pressure drilling, the well pressure tends to urge the drill pipe upwardly. For several hundred feet below -the surface depending upon the well pressure, it is necessary to hold the drill pipe against upward movement. Below this depth the weight of the drill pipe with collar and bit is enough to overcome the well pressure and the pipe moves downwardly by its own weight. For example: with 250$; well pressure at or near the surface, the drill pipe must be held against upward movement until some 400 feet of pipe is in the hole; below that the pipe will move downwardly unless restrained at the surface. Similarly for 1000# well pressure it is necessary to hold or snub for some 1400 to 1500 feet depth. It is well understood that the upper part of the hole is drilled most rapidly and that the time required per foot of hole increases with depth. It is therefore apparent that upslips and the snubbing jack are needed for the less portion of the total drilling work and time, and that the stripper bushing 26 with ordinary downslips will sufilce for much the greater part of the time.

Figure 4 shows the roller valve I9 closed as master gate thereby shutting off the well fluid. The bit, the drill collar or drill pipe and the stripper bushing 26 may then be inserted into and through the rotary machine 25 and the control head 24, whereupon seal is effected on the drill pipe and the stripper bushing. As the bit rests upon the closed rollers of valve I9, the ordinary slips need not be applied in the taper bowl 62 of the stripper bushing except it be to prevent rotative movement while adding drill pipe so. that a double (two lengths) projects above the stripper bushing. On very high derricks this may be a thribble or even a fourble. The ordinary slips if they were used are then removed and the sliphead 28 is put in place. The well pressure gage will indicate whether to apply downslips II or upslips I2 before opening roller valve I9. If sufficient well pressure is indicated the slips need not be applied, but the snubbing jack 29 is then picked up by the traveling block 39 and hoisteduntil it is above the tool joint at the top of the drill pipe. Upon lowering the snubbing jack the valve stem 94 enters the tool joint and drill pipe, and the grab hooks 86 being wide open, the piston 85 approaches the tool joint until the shank 92 meets the tool joint. Then as the snubbing jack continues its descent, the grab hooks close around the tool joint and when the snubbing jack is resting on and locked to the sliphead 28, the piston 85 is at the top of tubular cylinder 82. The space between the piston and the packer 60 of the stripper bushing 26 now forms a fluid tight chamber.

As a precaution against sudden lessening or loss of well pressure such as may occur when well flow is by heads, liquid may be admitted below the piston 85 through valve 99, so as to partially fill the cylinder because the air trapped therein will provide a resilient cushion for the piston, should the drill pipe move downward by its own weight. Of course the gage I81 will indicate this condition. Obviously if external pressure be applied to the fluid under the piston the latter with its suspended drill pipe load may be moved upwardly.

However with adequate well pressure and upon opening the roller valve I9, the bit and drill pipe will tend to move upwardly. Then by admitting liquid from a pressure source through valve I to the upper side of piston 85, the

drill pipe will be forced downward against the well pressure and then the upslips I2 in sliphead 28 may be applied. The snubbing jack is then given a quarter turn thereby freeing it from the sliphead; the traveling block will place the jack in its corner in the derrick, the valve 98 will open automatically and the liquid in cylinder 82 will drain therefrom as previously described. The operation for snubbing out of the well is quite similar, the fluid and the pressure on the upper side of piston 85 together with the control valves regulate the upward movement of the drill pipe.

Referring to Figures 8, 9, and 10 which illustrate the method of landing casing against Well pressure, the block I99 is substituted for the rotary machine 25. Thestripper bushing III] is adapted to receive casing I5 and is threaded into the control head 24 in substitution for the wear packer 24b. The hollow packer 24a is then expanded against stripper bushing IIU thereby effecting seal against escape of well fluid. The sliphead III differs only in size from the similar sliphead 28. The other control equipment including the casing head H are the same as for the drilling cycle previously described.

The casing I5 is shown to have at its lower end a conventional valved float shoe H2 for cementing service. The elevator II3 of Figure 8 is replaced by a snubbing jack of larger size but otherwise the same as snubbing jack 29. The casing is then forced into the well in the same manner as previously described for drill pipe 33. When the casing moves down of its own weight, the snubbing jack is set aside and the elevator H3 is used for the remaining depth. The sliphead is removed and the ordinary slips are used in the taper bowl of the stripper bushing.

Just before adding the terminal collar 40 to the last length of the casing I5, the string is held fluid tight in the roller valve I9, the last ordinary collar supporting the string on the rollers. The stripper bushing I I8 is then removed and the conventional slip spider II 4 is substituted. The terminal collar is now added to the casing, and into the upper end of the collar is threaded a landing and cementing tool I I5, which may be a length of casing.

The next step may be one of several alternatives. Thus it is possible to lubricate the terminal collar 40 into the casing head I! by means of roller valves I9 and 29 if the latter are provided with rollers for engaging the casing.

The simple and preferred way is to expand the packer 39 of the casing head against the casing I5, thereby efiecting seal and then lowering the string until the terminal collar is in the casing head preferably somewhat below its final position. Also, optionally, the packer 24a in control head 24 may be expanded for effecting additional seal on the casing string.

The casing I5 may now be cemented in the usual manner, the cement being forced through the landing tool II5 which thus serves as a cementing head. After the cement has set, the

casing may be liitedpor stretched to give the desired tension, and the slip spider raised and supported on blocks. Then by disconnecting roller valve l9 irom the casing head, the control column, comprising the two roller valves, the control head 24 and the intervening devices, may be lifted as a unit and likewise supported on temporary blocks. Now the metallic gasket I, the gland 42, the shims (ifneeded or preferred) and .the holding ring 44 are put in place, and the landing tool H5 is removed.

A suitable adapter like adapter 48 is inserted and screwed into the upper thread of the terminal collar-140. The roller valves and the control devices above them are lowered and bolted to the adapter. Meanwhile, rollers suitable for the next drilling cycle and casing string it have been placed in the valves l9 and 20.

If after the outer casing ll had been landed and cemented-the drill had found a productive sand below the casing, the fluid irom this formation would'have been available at the flow cross 22 and also at the vent pipes 35. With the system herein described, drilling could continue, circulating as much of the fluid as might be needed for bringing'out the drill cuttings, until setting casing I5. Then the flow will be up between the casings I4 and I5 and out through the vent pipes 35, the flow cross 22 then receives the fluid which may flow or be circulated through the casing ii. In like manner production from a second formation and a third formation and so on may be brought in the one well.

Although I have described several specific embodiments of my invention, it will be obvious to those skilled in the art, that various modifications may be made'in the details of construction, the general arrangement, the association of the several co-operating parts and the application of my invention without departing from the spirit thereof or the principles herein set forth.

What is claimed is:

1. In a snubbing jack for engaging a drill string or casing in a well, an elongated fluid pressure cylinder closed atone end and having an open end for detachable connection to the top of a well column, a piston therein, means for passing fluid under pressure to either side of the piston, and valve means for automatically drain-- ing the cylinder and operated, after removal of the cylinder from the well column, upon standing the cylinder on its bottom,

2. In a snubbing jack for controlling the lowering or raising of pipe in a well, a cylinder adapted to be attached to the top of a well column, a piston therein, means controlling the fluid pressure on either side of the piston, and means carried by the piston for engaging a string of pipe, comprising pivoted grabhooks, and means carried by the cylinder for releasing the hooks when the piston is lowered to a predetermined extent in the cylinder.

3. A hydraulic jack for controlling the insertion or withdrawal of a pipe in a well having confined fluid pressure, comprising: a cylinder adapted to surround the pipe susbtantially coaxially and to be attached fluid tight to the top of the well column, pipe engaging means and a piston in the cylinder, said means being adapted to hold the pipe to the piston for forcing the pipe to move in either direction in accordance with the movement of the piston, and means for pass ing fluid under pressure into the cylinder for moving the piston and pipe engaging means in either direction.

4. A snubbing jack for controlling the lowering or raising of a string oi pipe in a well having confined fluid pressure, comprising: a cylinder adapted to surround the pipe substantially co-' axially and to be supported in substantially coaxial relation to the well, a piston in the cylinder, and grab hooks carried by the piston for loosely and at least partly embracing the pipe and engaging an outwardly projecting member of said string for checking said movement.

5. In well equipment, a snubbing jack for controlling the lowering or raising of pipe in a well, comprising a cylinder and a piston, means for passing fluid under pressure above or below the Q for controlling the lowering or raising of pipe in a well, comprising: a cylinder and a piston, means for passing fluid under pressure above or below the piston, and means carried by the piston for draining the fluid from above the piston.

7. A snubbing jack for eiIecting, against conflned well pressure, the longitudinal movement of a string of pipe having collars of larger diameter than the pipe, comprising: a' cylinder adapted to surround said pipe and collars sub stantially coaxially, means, including a piston movable longitudinally in the cylinder, adapted to engage one of said collars, and means for passingfluid under pressure into the cylinder for compelling said movement in either direction,

8. In well equipment, apparatus for controlling the longitudinal movement of a string of pipe in a well having confined fluid pressure, said pipe having collars of larger diameter than the pipe, comprising: means forming a fluid tight continuous, cylindrical column'having sealing means at its lower end to seal against said pipe string and adapted to pass said pipe and said collars, oppositely directed slips in the column adapted to engage the pipe for optionally preventing said movement in either direction, and means, including a piston, in said column adapted to engage and move said pipe string in either direction.

9. Equipment adapted to control the insertion and withdrawal of a pipe in a well having conflned fluid pressure, comprising: a cylindrical column adapted to. surround said pipe substantially coaxially, said column being closed at its upper end against emergence of the pipe, and having sealing means at its lower end adapted to eflect fluid tight closure on the pipe, whereby said column is adapted to form a continuous fluid tight chamber, oppositely disposed slips in said chamber adapted to engage the pipe for preventing its movement, and pipe engaging means and a piston movable longitudinally in said chamber for effecting said insertion or withdrawal.

10. In well derrick equipment, means for controlling the longitudinal movement of a pipe in either direction comprising in combination: a

rotary drilling machine having a sealing memher for effecting closure on said pipe, a substanclosure on said pipe, a sliphead secured to the preventer and having means adapted to optionally engage and hold the pipe against longitudinal movement in either direction, a cylinder secured to the sliphead, said preventer, said sliphead and said cylinder forming a continuous fluid tight chamber adapted to surround the pipe substantially coaxially, and means, including a piston, in the cylinder adapted to engage the pipe and to effect said insertion or withdrawal with or without the aid of well pressure.

' FREDERIC W. HILD.

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