US3311168A - Well head assembly with means for effecting a preloaded seal - Google Patents

Description

March 28, 1967 E. K. PIERCE, JR 3,311,168

WELL HEAD ASSEMBLY WITH MEANS FOR EFFECTING A PRELOADED SEAL Filed Dec. 4, 1964 3 Sheets-Sheet 1 INVENTOR 1 waapfl BAT/76E MY ZM Wiw ATTORNEY5 March 28, 1967 PlERCE, JR 3,311,168

WELL HEAD ASSEMBLY WITH MEANS FOR EFFECTING A PRELOADED SEAL Filed Dec. 4, 1964 5 Sheets-Sheet 2 Egg? A230 A50 ZNVENTOR Z2 WOOD/K BERCE RNEYS March 28, 1967 K, PIERCE, JR 3,311,168

WELL HEAD ASSEMBLY WITH MEANS FOR EFFEGTING A PRELOADED SEAL Filed Dec. 4, 1964 5 Sheets-Sheet s INVENTOR ai 4M, wi 1 /W United States. Patent ()fiice 3,311,1fl8 Patented Mar. 28, 1967 3,311,168 WELL HEAD ASSEMBLY WITH MEANS FOR EFFECTING A PRELOADED SEAL Elwood K. Pierce, J12, Houston, Tex., assignor to Gray Tool Company, Houston, Tex., a corporation of Texas Filed Dec. 4, 1964, Ser. No. 416,072 19 Claims. (Cl. 166-89) The present invention relates to well head equipment and more particularly to a compact well head assembly including means for effecting a preloaded seal in a casing head throughbore.

In the drilling of petroleum wells, it has been the usual practice to being drilling a relatively large diameter hole, then as drilling progresses deeper to effect several reductions in the diameter of the well being drilled. Usually each stage of the hole must be lined with casing after it is drilled and cement run into the annulus between the exterior of the casing and the periphery of the hole. The casing seals off the hole from cave-ins, and the cement besides protecting the casing from corrosion, prevents migration of fluids from one formation to another and allows the oil and/or gas produced by the well upon completion to be segregated. The cement additionally aids in retaining the casing properly positioned with respect to the hole.

Usually, each casing extends upwardly to the surface of the well, each smaller casing being received within the casing set just before it.

In a conventional completion, the largest diameter outer casing usually called a surface casing receives at its upper end a casing head which has an internal, generally vertically extending throughbore. Means such as an upwardly facing tapered annular shoulder is usually provided in the casing head throughbore for receiving and supporting a casing hanger.

Accordingly, after the well has been deepened sufficiently to receive a second casing, of smaller diameter than the surface casing it is run into the well and a hanger secured to its exterior near the upper end thereof. The hanger may take several forms such as those commonly referred to as boll-weevils, slip-type or Wrap-around type. Each have in common provisions for gripping the exterior of the casing and seating on a shoulder or similar means provided in the casing head throughbore.

Often, means such as hold down wedges are provided in lateral ports in the casing head for wedging contact with the upper end of the casing hanger or the hung casing itself in order to prevent upward movement of the casing if down hole pressure should at any time suddenly increase.

Alternative provisions for holding down a casing include providing an upwardly, inwardly tapering annular surface on the casing hanger above the region thereof which seats on the casing head throughbore shoulder or the like. Such a double tapered hanger is exemplified in FIGURE 9 of the United States patent Mueller, 2,162,- 179 granted June 13, 1939.

The double-tapered casing hanger upwardly converging surface is adapted to be received against a complementarily curved surface at the lower extent of the throughbore of a second casing head or a tubing head which in a conventional well completion is supported on the first casing head. The two heads are secured to one another in some instances by bolts extending through radially outwardly directed flanges on each head, or by alternative means such as an expansible contractile segmented clamp secured over these flanges.

Drilling of the next smaller diameter segment of the hole is then conducted through the second mentioned casing head or tubing head, care being taken to prevent damage to the throughbore of this head by the drill string, drill collars or the like.

Conventionally, when the last-mentioned segment of the hole has been completed a casing is run into the Well through the throughbore of the last-mentioned head and seated and held down with respect thereto by means similar to those discussed in regard to the first casing head.

This procedure is repeated for each succeeding casing. The casings usually each being cemented in place just after being run into the well as above-mentioned. Such wells are completed by a tubing head and tubing hangers which receive one or a plurality of strings of tubing whose lower regions are adapted to receive oil and/or gas from one or a plurality of producing zones in the well.

In order to prevent damage or undue danger to life and property, at each stage during the completion of the well until it is finally completed, it has become the standard practice and often a requirement to provide blowout prevention devices at the well head. These devices in their more comprehensive form include a plurality of blowout preventers secured in a vertically stacked relationship to whichever well head element is topmost at that particular point in the completion procedure.

As again exemplified by the Mueller Patent No. 2,162,- 179, inasmuch as each successively upper casing head or tubing head conventionally has a throughbore which is reduced in diameter from that of the head on which it is mounted in order to provide a hanger seat therein, the upper flange of each head is usually of smaller diameter than the lower flange of the same head. This reduction in size is not merely a matter of choice or design, but one of necessity in the past in order to present a minimum of potential area for leakage to the fluid pressure with in the various conduits extending into the well. Characteristically, such pressures actually or potentially increase as the depth of the well increases. A typical blowout preventer stack, beside a master drilling valve characteristically includes a ram type preventer with blind rams for rapidly closing off exterior communication to the well at a time when no conduits or drill string extend through the stack and a ram type preventer with pipe rams for rapidly closing off exterior communication to the Well when casing, drill string or the like extend through the stack. The pipe rams when closed about a pipe prevent its upward movement when the pipe is subjected to a sudden increase in pressure from below. The two ram type preventers may be surmounted by a third preventer having an annularly contractile ram element which is useful in clamping against pipe as well as against wire lines and the like.

Because of the progressive reduction in size of the succeeding casing and tubing heads upon which the blowout preventer stack is to be mounted, it has been necessary in the past to provide a plurality of such stacks or at least a plurality of adapter hubs each of a size for mounting on the particular Well head element which was topmost at a particular stage of the completion of the well.

Usually the preventers of larger bore are rated for use at lower pressures and those of smaller bore for use at higher pressures so that even the use of adapters does not provide a complete solution to the duplication problem.

While the cost of such duplication of equipment and provision of special adaptors was tolerable in many instances in the past, it has become increasingly unjustifiable with the rise of drilling cost, the increasing depth of petroleum wells and especially with the advent of very large diameter casing. For instance, the cost of keeping on hand a first preventer stack for use on a 20 inch 0D. surface casing and a second stack for use on the 13% inch O.D. casing next run into the hole would be too excessive to be economically feasible in many instances.

It should also be apparent that in the conventional procedure as outlined even though other hold down means are provided before a preventer stack is removed preparatory to mounting a subsequent head on the one on which the preventers had been mounted, there is less certainty that a blowout could be prevented in the hiatus or that 'if a blowout occurred at this time the pipe could be stri ped back into the hole.

It has been proposed in the prior art to alleviate some of these disadvantages, particularly as they relate to underwater completions by providing a well head assembly where a casing having a relatively wide shoulder in its bore receives a hanger supporting a first casing and each succeeding string of conduit is hangingly supported on successively smaller hangers which nest with and are supported upon the first-mentioned hanger. While such an arrangement is acceptable where the total weight of conduit to be supported by the head is not great, the increase in the CD. of the head which such a construction necessitates when the supported weight is very great, for instance for deep wells, makes such an arrangement often unacceptable. As an example the resultant first casing hanger may have so large an CD. that it will not fit through the available blowout preventers, so that the stack must be removed in order to place the first casing hanger. On the other hand, if the hanger seat in the casing head is made more narrow than would otherwise be considered prudent, in order to reduce the OD. of the casing head to reasonable size, and the well later pushed to greater depth than had at first been contemplated, it is clearly apparent that bearing failure of the single casing hanger seat could easily occur with resultant loss of'conduit into the well.

Another unitary head arrangement of the prior art contemplates the provision of a plurality of vertically spaced seats within the head through bore, each for supporting a hanger and a string of conduit secured to the hanger. A disadvantage of such arrangements is that they are often little more compact than stacked individual heads and hangers and they are often more expensive because they involve large castings or forgings and are often not standard stocked items.

It is an important object of the present invention to provide a well head assembly which includes a casing head adapted to receive a plurality of hangers, supporting a portion of the weight of the hangers and casing suspended therefrom on a primary seat while transferring a predeterminable portion of the stress ensuing from the hanger and casing weight to the head at at least one region thereon above the primary seat.

A further object of the invention is the provision of a well head assembly which partakes of the advantages of deep bowl and multi-seat unitary heads while minimizing their disadvantages.

Another object of the invention is the provision in a compact well head assembly of a casing head having a primary seat and a pair of differentially tapered sealing surfaces spaced above the primary seat and above and below a side port and a hanger having complementary sealing surfaces and a seat for mounting the hanger in said casing, the sealing surfaces being spaced from one another and the seat by an amount such that the uppermost seal begins to set before the lower seal and before the hanger has seated in the head thus providing prestressed seals both above and below said side port and making provision for transfer to the casing head, at points thereon above said seat, of at least a portion of the stress of well head parts subsequently mounted on said hanger.

These and other objects of the invention as well as the principles and scope thereof will become more clearly apparent during the course of the following detailed dlS- cussion relating to three exemplary embodiments of apparatus according to the invention, the embodiments being illustrated in the attached drawings.

In the drawings:

FIGURE 1 is a fragmentary longitudinal sectional view with portions in elevation, of a well head embodying principles of the present invention;

FIGURE 2 is a fragmentary elevation view of a second well head embodying principles of the present invention, portions being broken away to expose details otherwise hidden; and

FIGURE 3 is a fragmentary elevation view similar to FIGURE 2, of a third embodiment of the invention.

As shown in FIGURE 1, the well head assembly 10 includes a surface casing 12 secured to the well by means of conventional cement 14. The surface casing 12 is secured at its upper end to the lower end of a casing head 16, for instance by exterior threads 18 on the casing 12 adjacent its upper end and interior threads 20 in the longitudinal throughbore 22 of the casing head 16 adjacent the lower end thereof. In this manner, the head 16 is supported by the casing 12. Of course, the threaded joint 18, 20 is exemplary and could be replaced by equivalent means such as a slip-on joint welded in situ to the surface casing.

The casing head 16 proceeding from the upper end 24 of the throughbore 22 includes a first upwardly facing, tapered annular sealing surface 26, an annulus port 28 intersecting a cylindrically tapered region 30 of the bore just below the surface 26 and a second upwardly facing, tapered annular sealing surface 32 having a shallower taper angle with respect to a horizontal plane than the surface 26. The second sealing surface 32 at its upper extent joins the surface 30 below the annulus port 28.

A cylindrically curved surface 34 extends downwardly from the lower, inner extent of the surface 32 and terminates in a counterbore 36.

Besides being intersected by an annulus port 28, or a plurality of such ports 28 angularly spaced from one another, the throughbore 22 is shown also being intersected by a plurality of locking screw receiving, angularly spaced lateral ports 38 (only one being shown).

The port 38 isshown extending through the upper radial flange 40 of the head 16. A plurality of angularly spaced, radially extending wedge element receiving ports 42 (one being shown) intersect the bore 22 intermediate the upper -and lower extent of the surface 34. At least one radial outlet 44 intersects the counterbore 36.

The locking screw 46 is shown having a frusto-conical head 48, a threaded body 50 engaged in the threaded bore 38 and a stem 52 having wrench receiving means for effecting an advancement and retraction of the locking screw 46. The annulus port 28 is shown terminating at its outer extent in a boss 54 peripherally surrounding the port. In use suitable piping and valving may be secured to the boss 54 by conventional means such as bolts received in threaded sockets (not shown) in the boss, welding, or a threaded coupling. 7

The wedge 56 received in the port 42 is preferably of the non-rotating type having an eccentrically mounted drive stem 58, as disclosed in the commonly assigned, copending application of Pierce, Ser. No. 260,372, filed Feb. 25, 1963, now Patent No. 3,248,132. The outlet 44 may be connected to suitable piping and valving similarly to the port 28.

After the casing head 16 has been secured to the surface casing 12, drilling operations may be conducted through the bore 22 and the casing throughbore 60. A convention-a1 blowout preventer stack (not shown) may be secured to the casing head 16 upper flange 40 as by bolts either before or after the casing head 16 is mounted on the surface casing 12.

It is of interest to note that because the locking screws 46 and wedges 56 are retractable, drilling operations con ducted through the bore 22 have the advantage of the full bore, which would not be the case were the bore choked with a large annular hanger seat.

When the hole has been drilled sufliciently deep to receive the intermediate casing 62, the latter is lowered into the well, the upper end of the casing 62 being secured to a hanger 64. The casing 62 is shown secured to the hanger 64 by exterior threads 66 adjacent the upper extent of the casing and interior threads 68 adjacent the lower extent of the throughbore 70 of the hanger. Conventional alternative securement such as by welding could be utilized. As shown the hanger throughbore 70 is also interiorly threaded at 72 intermediate the ends thereof to removably receive a lowering nipple, test plug or the like.

Adjacent and leading to the upper end of the hanger 64, an upwardly facing tapered annular seat 74 is formed having a taper angle of, for instance, 15 degrees with respect to a vertical plane. The exterior of the hanger 64 is preferably tapered adjacent its upper end at 76 providing an upwardly facing tapered annular surface for engagement by the frustoconical locking screw heads 48. Adjacent and proceeding upwardly from its lower end the hanger 64 is circumferentially relieved to form a downwardly facing annular seat 78. A laterally extending opening 80 is formed through the hanger for communication with the port 28. Above and below the opening 80 sealing surfaces 82 and 84 having taper angles complementary with the differentially tapered sealing surfaces 26 and 32 are formed. Convention-a1 compressible, molded annular rings 86 of sealing material are shown received in annular recesses 88 in the surfaces 82, 84.

Using a conventional lowering bushing or the like the hanger 64 is lowered through the preventer stack toward the position shown, the screws 46 being retracted and the wedges 56 extended into the bore 22 as shown to provide a primary hanger seat. Because of the differential taper and spacing of the sealing surfaces 26, 82 and 32, 84, the more nearly vertical surface 82 begins toland at 26 substantially before the shoulder 78' contacts the wedges 56, shortly thereafter but still before the shoulder 78 contacts the wedges 56, the sealing surface 84 begins to land at 32.

By way of example, in an instance where the casing head bore 22 has a 13% inch ID. and is received on a casing 12 of 16 inch O.D., the largest CD. of the hanger 64 for hanging a 10% inch O.D. casing 62 is 13 /2 inch since the seat is provided by the retractable wedges 56.

While drilling for and running the 10% inch O.D. casing, the wedges 56 are retracted leaving 13% inch diameter bore 22 substantially fully open as above noted. The wedges 56 when run in choke the bore 22 to provide a shelf-like seat for the 10% inch O.D. casing 62.

In the example, the surfaces 26, 82 have a inch taper per foot (a 16:1 ratio vertical to lateral) and the surfaces 32, 84 a 2 inch taper per foot (a 6:1 ratio vertical to lateral). Accordingly, the seal 26, 82 begins to set when the casing hanger shoulder 78 is /2 inch to inch above the upper horizontal surface 90 of the Wedge 56 and the seal 32, 84 begins to set when the casing hanger shoulder 78 is about inch above the surface 90. By the time the shoulder 78 seats on the surface 90 the rings 88 have been compressed so that they are flush with the surfaces 82, 84 and the seals 82, 26 and 84, 32 are preloaded so as to carry a predeterminable proportion of the casing hanger 64 load directly to the head 16 adjacent the surfaces 26 and 32. It is important to note that this preloading additionally provides a greater assurance against leakage about the annulus port 26, 80 than would be the case if the seals were not preloaded.

After the casing 62 has been run and the hanger 64 seated, the locking screws 46 may be run in so that the heads 48 engage the surface 76 to hold down the hanger 64 and casing 62. The casing 62 may be conventionally cemented by pumping cement down the bore 92 of the casing 62 around its lower end and up the annulus between the casings 62 and 12. The cement forces the drilling fluid ahead of it upwardly and out through the outlet 44. When the cement has set, the drill string can be lowered through the preventer stack, into the casing 62, bore 92, the wiper plug, if used, drilled through and drilling operations recommenced. Upon reaching the desired depth, the drill string can be pulled and the oil string 94 of easing run into the well and hung for instance utilizing a double tapered hanger 96 of the type disclosed in the commonly assigned U.S. patents to Mueller et al., No. 2,620,880, granted Dec. 9, 1952; Mueller et al., No. 2,624,413, granted Jan. 6, 1953; Watts et al., No. 2,751,- 235, granted June 19, 1956; Watts et al., No. 2,754,134, granted July 10, 1956; or Phillips, No. 2,754,136, also granted July 10, 1956. As shown the hanger 96 has a lower, downwardly facing tapered annular surface 98 which includes a compressible ring 100 mounted in an annular recess 102 thereof and seats against the surface 74 of the hanger 64 so that .a substantial portion of the load of the hanger 96 and casing 94 is transmitted through the hanger 64 adjacent the surface 74 and to the casing head 16 adjacent the surface 26. Some additional proportion of the loading is transmitted through the hanger 64 at 84 to the head 16 and the only remaining portion is incumbent upon the wedges 56.

The hanger 96 is temporarily sealed to the casing 94 by the resilient seal 104 as disclosed in the last-mentioned patents and permanently sealed thereto by the deposition of welding material as at 106. Hold down means such as additional locking screws (not shown) may be provided to hold the casing 94 and hanger 96 down while the preventer stack is removed. An upper, upwardly facing tapered annular shoulder 108 provided onthe hanger seals against a complementary surface 110 on a conventional tubing head 112. The tubing head 112 is shown having a lower radially extending flange 114 which is bolted as by bolts 116 to the flange 40 of the casing head 16 in order to secure the tubing head 112 in place and hold down the hanger 96. An API ring 118 is shown received in complementary annular recesses 120 in the upper and lower ends of the casing head 16 and tubing head 112 respectively to seal between these members. Alternately opposed flexible tapered lip hard metal sealing rings such as are disclosed in the commonly assigned U.S. patents'to Watts et al., 2,766,829, 2,766,998, and 2,766,999, all granted Oct. 16, 1956, and using clamping arrangements as shown in those patents in place of the bolted flanges 40, 114, 116. The Well may then be conventionally completed with tubing, tubing hangers, Christmas tree cap, Christmas tree and perforated, packed off, and otherwise completed as desired.

The embodiments shown in FIGURES 2 and 3 are intended to illustrate the broad range of applicability of the principles of the present invention.

In FIGURE 2, a first casing head 120, having a longitudinal throughbore 122 is shown received via a welded slip on joint at 124 on a surface casing 126. The next smaller diameter casing 128 is shown supported in the head 120 by a split hanger 130 of the type generally shown in the U.S. patent to Watts et al., No. 3,051,513, granted Aug. 28, 1964, and more particularly as shown in the commonly assigned copending application of Watts et al., Ser. No. 65,064,'filed Oct. 26, 1960, now Patent No. 3,257,130. As more completely described in the just-mentioned patent and application, the hanger 130 comprises a lower hanger element 132 preferably formed from a plurality of sets of arcuate segments 134, 136 and a bonnet 138. Each segment set 134, 136 is interdigitated and the segments 134 and 136 are arcuately movable with respect to one another between a first position wherein they are arcuately coterminous and the segment sets can be individually inserted in the casing head and a second position wherein each upper segment 134 extends arcuately beyond the lower segment on which it is carried in its first position and is interdigitated with an adjacent lower segment to form an annular hanger element 132. The slips 140 of the hanger element 132 grip and support the casing 128 and the element 132 is in turn supported on the upwardly facing tapered annular load shoulder 142 in the bore 122.

As explained in the aforementioned Watts et a1. application, the bonnet 138 first provides temporary sealing at 144, then permanent sealing by virtue of the deposition of welding material at 146. The downwardly facing ,frusto-conic sealing and seating surface 148 on the bonnet 138 is received on the upwardly facing tapered annular shoulder and sealing surface 150 formed in the bore 122 adjacent and leading to the upper extent thereof.

, The welding material 146 may be deposited in such a manner for instance while holding the casing 128 in tension, that when positioned as shown, a portion of the weight of the casing 128 is carried through the weld to the bonnet 138 and through the seat 148 into the casing head 120.

The bonnet 138 has an upwardly facing tapered annular sealing surface 152 sealingly received against a downwardly facing tapered annular sealing surface 154 formed in the throughbore 156 of a second casing head 158- received on'the casing head 120 and secured thereto as by bolted flanges 168 as shown sealed by an API ring 162. Alternate securement and sealing such as the opposed, defiectable, hard metal tapered lip annular sealing rings and clamps as shown in the aforementioned patents to Watts et al., 2,766,829, 2,766,998 and 2,766,999 may be employed.

The engagement of the surfaces 154 and v152 additionally serves to hold down the bonnet 138 and conduit 128.

Above the annulus port 164, the bore 156 is enlarged to form an upwardly facing tapered annular load shoulder 166, having a taper of for instance 45 degrees to the horizontal. Alternately, means such as the ports 42 and retractable wedges 56, 58 of FIGURE 1 could be provided at this point to maximize the diameter of the bore 156. Upwardly of the shoulder 166, the bore 156 includes a cylindrically curved region 168, a relatively steeper tapered, annular upwardly facing sealing surface .170 corresponding to the surface 32 in FIGURE 1, an annular recess 172 concentric with the bore 156, a cylindri-cally curved region 174, a more shallow tapered, annular, upwardly facing sealing surface 176 relative to the surface 170 and corresponding to the surface 26 of FIG- URE l, a cylindrically curved region 178 and an upwardly facing, frusto-conic bonnet seat and sealing surface 1-80 adjacent and leading to the upper end of the bore 156.'

When the casing 182 is to be hung in the well, it is secured to a hanger 184 similar to the hanger 64 of FIGURE 1 for instance by exterior threading 186 on the casing 182 leading to the upper end thereof and interior threading 188 in the bore 190 adjacent and leading to the lower end thereof.

The exterior of the hanger 184 includes a tapered annular seat 192 complementary to the load shoulder 166 and first and second downwardly facing tapered annular sealing surfaces 194 and 196 respectively complementary to the surfaces 170 and 176 of the casing head 158. Each of the surfaces 194, 196 preferably has a pair of vertically spaced annular recesses 198 therein which receive conventional packing material 200. The latter projects beyond the surfaces 194, 196 before seating of the hanger 184 but is compressed to flushness as shown upon seating. An annular recess 202 is formed in the exterior of the hanger 184 between the sealing surfaces 194 and 196. The recess 202 is positioned on the hanger to form, complementarily wit-h recess 172, a generally toroidal chamber 204, between the hanger 184 and head 158 when the hanger 184 is seated. The chamber 204 is preferably communicated at at least one point 206 to the bore 190 of the hanger 184 and to the exterior of the head 158, for instance by an annulus port 208 comprising an arrangement similar to the arrangement 54, 28, 80 of FIGURE 1.

The hanger 184 and casing 182 can be lowered to the position shown utilizing a conventional lowering nipple (not shown) removably securable to the hanger 184- for instance, to the threads 210 in the bore 198. Similarly to the procedure discussed in regard to the embodiment of FIGURE 1, as the hanger 184 is lowered by virtue of the differential taper and placement of the sealing surfaces 194 and 196 a seal begins to be made at first at 176, 196 and second at 170, 194 before the seat 192 lands on the load shoulder. Also similarly, the seals 194, 196 and 170, 194 are prestressed in the sense that they are sequentially set so that each carry a predeterminable load resulting from the weight of the casing 182 and hanger 184 to the casing head .158. According to the present invention because of the prestressed seal above and below the chamber 204, the likelihood of extremely high subterranean pressure communicated to the interior of the casing 182 leaking upwardly or downwardly from the chamber 204 rather than being controllable from the annulus port arrangement 206, 208 is greatly reduced.

A further casing 212 can be received in the well and hung via a hanger assembly 214 similar to the hanger assembly 130. The lower hanger element 216 of the assembly 214 is shown gripping the exterior of the casing 212 and being seated on an upwardly facing, tapered annular load shoulder 218. The provision of the seals 176, 196 and 170, 194 ensures that a predeterminable portion of the load resulting from the weight of the casing 212 and lower hanger element 216 will be transferred through the hanger 182 directly to the casing 158 adjacent these seals rather than being fully incumbent upon the load shoulder 166.

An upper hanger element or bonnet 220 similar to the bonnet 138 is sealed and secured to the casing 212 above the element 216 and is seated via a downwardly facing frusto-conic shoulder 222, on the seat 180. The upwardly facing tapered annular surface 224 on the bonnet 220 is sealingly received against a complementary tapered annular surface 224 in the throughbore 228 of a conventional tubing head 230 or the like secured to the head 158 by a bolted flange arrangement 232 or the like. Additional hold down means such as a plurality of latch screws 234 are shown received in arcuately spaced laterally extending openings 236 in .the head 158. The inner ends of the lower row of screws 234 engage an outer, upwardly facing tapered annular surface 238 leading from the upper extent of the hanger 184. The inner ends of the upper row of screws 234 are received in an annular groove in the exterior of the bonnet 220. These hold down means 234 are of special aid in preserving control of the well at the time the blowout preventer stack is being removed from the head 158 preparatory to the mounting of the head 230 thereon. Numerals 242 indicate conventional test ports.

The well head shown in FIGURE 2 may be further completed by the installation of production equipment such as tubing, valving, Christmas tree cap, Christmas tree and the like.

By way of example, the program of casing shown in FIGURE 2 may include a 20 inch O.D. casing 126, a 13% inch O.D. casing 128, a 9 inch O.D. casing 182 and a 5 inch O.D. casing 212, the latter two being sustained in the head 158 by the hanger 184.

The embodiment shown in FIGURE 3 is in most respects identical to that shown in FIGURE 2 and is similarly numeraled. The major difference between the two is that in the program of FIGURE 3, the casing 212 is used as a liner and is not brought to the surface. It is not shown in FIGURE 3. Instead of the casing hanger 214, of FIGURE 2, the hanger 184 in an inner, upwardly facing tapered annular seat 244 leading to the upper end thereof supportingly and sealingly receives a tubing hanger 246 held thereagainst by the upper row of latch screws 234.

9 The tubing hanger supportingly receives a string of tubing 248 for instance by the tightening of the gland 250 which flexes the V-rings 252 into sealing engagement with the tubing exterior and the threaded securement of a special bushing 254 at its upper end to the tubing head 256 and at its lower end to the upper end of the tubing.

The manner of effecting this exemplary completion ismore fully set forth in the US. patent to Yancey, 2,241,- 288, granted May 6, 1941.

Of course, the completion having a single tubing shown in FIGURE 3 could be modified to include a plurality of tubing strings as is known in the art.

From the foregoing detailed explanation relating to exemplary embodiments of the invention, it should be clear that the invention disclosed efiiciently accomplishes each of the objects set forth at the outset of the specification. It should be apparent that the specific embodiments shown can be considerably modified Within the purview of the inventions principles and therefore, the invention should be understood as encompassing all such modifications as are within the spirit and scope of the following claims.

I claim:

1. A well head assembly including a housing having means defining a longitudinal throughbore therein; means defining a lateral outlet in said housing communicating with the throughbore intermediate the ends thereof; means defining a first upwardly facing shoulder in said throughbore above the juncture of said outlet therewith; means defining a second upwardly facing shoulder in said throughbore below the juncture of said outlet therewith; a hanger received in said housing throughbore and at least partially supported on said first and second shoulders, said shoulders being so spaced and configured that said hanger begins to engage said first shoulder before engaging said second shoulder as said hanger is received in said throughbore whereby a predeterminable portion of the load resulting from the weight of the hanger is transferred to the housing at said first shoulder.

2. A well head assembly as set forth in claim 1 including primary load shoulder means in said housing below said second shoulder for supporting the majority of the weight of said hanger.

3. A well head assembly as set forth in claim 2 wherein the primary load shoulder means comprises a side outlet communicating with said throughbore and means received in said side outlet and advanceable therein into constricting relationship with said throughbore.

4. A well head assembly as set forth in claim 3 wherein said first and second upwardly facing shoulders comprise first and second tapered annular surfaces concentric with the housing throughbore, the first tapered annular surface being tapered at a more acute angle with respect to the longitudinal axis of the housing throughbore than the second tapered annular surface.

5. A well head assembly as set forth in claim 4 wherein said second tapered annular surface is spaced above the means received in said side outlet sufiiciently that as said hanger is being received in said housing said hanger begins to seat first on said first tapered annular surface above said lateral outlet and second on said second tapered annular surface below said lateral outlet before seating on the means received in said side outlet.

6. A well head assembly as set forth in claim 5 wherein said hanger includes three downwardly facing, vertically spaced annular surfaces the uppermost and intermediate of which are respectively tapered correspondingly to the first and second tapered annular surfaces of said housing; said three hanger surfaces being received abuttingly adjacent said housing first and second tapered annular surfaces and the means received in said side outlet to support said hanger in said housing.

7. A well head assembly as set forth in claim 6 further including annular resilient sealing means received between said housing first tapered annular surface and the uppermost of said hanger annular surfaces and at least one annular resilient sealing ring received between said housing second tapered annular surface and the intermediate of said hanger annular surfaces for providing a preloaded seal above and below said lateral outlet.

8. A well head assembly as set forth in claim 7 further including means defining a throughbore in the hanger and means defining a lateral opening in the hanger communicating with the throughbore thereof and with the housing lateral outlet.

9. A well head assembly as set forth in claim 2 wherein the primary load shoulder means comprises an upwardly facing tapered annular surface concentric with said throughbore.

10. A well head assembly as set forth in claim 9 wherein said first and second upwardly facing shoulders comprise first and second tapered annular surfaces concentric with .said throughbore, the first tapered annular surface being tapered at a more acute angle with respect to the longitudinal axis of the throughbore than the second tapered annular surface.

11. A well head assembly as set forth in claim 10 wherein said second tapered annular surface is tapered at a more acute angle with respect to the longitudinal axis of the throughbore than said primary load shoulder whereby as said hanger is being received in said housing said hanger begins to seat first on said first tapered annular surface above said lateral outlet and second on said second tapered annular surface below said lateral outlet before seating on said primary load shoulder.

12. A well head assembly as set forth in claim 11 wherein said hanger includes three downwardly facing vertically spaced tapered annular surfaces respectively tapered correspondingly to the first and second tapered annular surfaces and primary load shoulder of said housing, said three hanger surfaces being received abuttingly adjacent said housing first and second tapered annular surfaces and primary load shoulder to support said hanger in said housing.

13. A well head assembly as set forth in claim 12 further including annular resilient sealing means received between said housing first tapered annular surface and the uppermost of said hanger three tapered annular surfaces and at least one annular resilient sealing ring received between said housing second tapered annular surface and the intermediate of said hanger three tapered annular surfaces for providing a preloaded seal above and below said lateral outlet.

14. A well head assembly as set forth in claim 13 further including means defining annular grooves in said hanger uppermost and intermediate tapered annular surfaces, said annular resilient sealing means being received in said grooves.

15. A well head assembly as set forth in claim 13 further comprising a throughbore in said hanger; a first larger diameter conduit string; means supporting said first conduit string adjacent the upper end of said first conduit string in said hanger throughbore, a second smaller diameter conduit string received in said hanger throughbore and within said first conduit string; and means supporting said second conduit string adjacent the upper end of said second conduit string in said hanger throughbore.

16. A well head assembly as set forth in claim 15 wherein said first and second conduit strings comprise well casing and the means supporting the second casing includes means defining an upwardly facing annular shoulder in said hanger throughbore and a casing hanger supportingly received on the last-mentioned shoulder and secured to the second casing.

17. A well head assembly as set forth in claim 15 wherein the first conduit string comprises well casing and said second conduit string comprises well tubing, and wherein the means supporting the well tubing includes means defining an upwardly facing annular shoulder in said hanger throughbore and a tubing hanger supportingly received on the last-mentioned shoulder and secured to thewell tubing 18. A well head assembly as set forth in claim 15 further comprising means defining a lateral opening in said hanger communicating with said hanger throughbore and the exterior of said hanger; and means communicating the hanger lateral opening with the lateral port in said housing for providing communication between the annulus defined between the first and second conduit strings and the exterior of said housing.

'19. A Well head assembly as set forth in claim 18 wherein said communicating means comprises a circumferential groove in the exterior of said hanger and intersecting the opening therethrough, and a circumferential groove in the throughbore of said housing intersecting the juncture of the lateral port therewith; said circumferential grooves being positioned radially adjacent one another to define a generally toroidal chamber.

References (Iited by the Examiner UNITED STATES PATENTS Howard 285143 Penick et al. 2774 Shaffer et a1. 285-143 X McDonough et al. 16689 X Lemley 16688 Baker et al. 285142 X Raulins et al. 166-89 Peterson 16688 Rector 285137 Great Britain,

CHARLES E. OCONNELL, Primary Examiner.

I. A. CALVERT, Assistant Examiner.

Claims (1)

1. A WELL HEAD ASSEMBLY INCLUDING A HOUSING HAVING MEANS DEFINING A LONGITUDINAL THROUGHBORE THEREIN; MEANS DEFINING A LATERAL OUTLET IN SAID HOUSING COMMUNICATING WITH THE THROUGHBORE INTERMEDIATE THE ENDS THEREOF; MEANS DEFINING A FIRST UPWARDLY FACING SHOULDER IN SAID THROUGHBORE ABOVE THE JUNCTURE OF SAID OUTLET THEREWITH; MEANS DEFINING A SECOND UPWARDLY FACING SHOULDER IN SAID THROUGHBORE BELOW THE JUNCTURE OF SAID OUTLET THEREWITH; A HANGER RECEIVED IN SAID HOUSING THROUGHBORE AND AT LEAST PARTIALLY SUPPORTED ON SAID FIRST AND SECOND SHOULDERS, SAID SHOULDERS BEING SO SPACED AND CONFIGURED THAT SAID HANGER BEGINS TO ENGAGE SAID FIRST SHOULDER BEFORE ENGAGING SAID SECOND SHOULDER AS SAID HANGER IS RECEIVED IN SAID THROUGHBORE WHEREBY A PREDETERMINABLE PORTION OF THE LOAD RESULTING FROM THE WEIGHT OF THE HANGER IS TRANSFERRED TO THE HOUSING AT SAID FIRST SHOULDER.

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