US3678996A

US3678996A - Well completion and apparatus

Info

Publication number: US3678996A
Application number: US80192A
Authority: US
Inventors: David P Herd
Original assignee: Rockwell Manufacturing Co
Current assignee: Cooper Industries LLC; Rockwell Manufacturing Co
Priority date: 1970-10-12
Filing date: 1970-10-12
Publication date: 1972-07-25
Anticipated expiration: 1989-07-25

Abstract

A guide base and method of installing the same for underwater wells. The guide base comprises a tubular guide hub having structural support members radially projecting therefrom to which are affixed a plurality of vertical guide columns with cables extending upwardly therefrom. Near the top of the tubular hub is a support ring which seats on a support shoulder affixed to the conductor casing head of an underwater well. An orientation pin projects radially from the conductor casing to which it is affixed below the casing head. Above the pin a latch ring is affixed to the conductor having a downwardly facing slightly tapered surface. Longitudinal ribs are affixed at regular intervals around the conductor between the latch ring and the support shoulder affixed to the casinghead. Affixed to the bottom of the tubular guide hub by a bolted flanged joint is an orientation sleeve. The lower end of the sleeve is formed by cutting a left-hand helix and a right-hand helix so that they intersect in a lower tip and an apex near the flanged joint. At the apex a vertical pin slot is provided. A hold down latch assembly is provided on the tubular guide hub which has a latch member laterally engageable with the conductor latch ring when the orientation pin and pin slot are fully engaged. The guide base is installed after the conductor casing and its riser have been installed and after further drilling has proceeded.

Description

United States Patent Herd [451 July 25, 1972 [54] WELL COMPLETION AND APPARATUS Primary Examiner-Richard E. Moore [72] Inventor. David P. Herd, Houston, Tex. Assistant Examiner Richard E. Favreau [73] Assignee: Rockwell Manufacturing Company, A!!0rneyBill B. Berryhill, James A. Bargfrede, Murray Houston, Tex. Robinson, Ned L. Conley and Robert W. B. Dickerson [21] Appl' 80,192 A guide base and method of installing the same for underwater wells. The guide base comprises a tubular guide hub having Related Application Dam structural support members radially projecting therefrom to [63] Continuation of Ser. No. 743,782, Jul 10, 1968 which are affixed a plurality of vertical guide columns with cab do ed, bles extending upwardly therefrom. Near the top of the tubular hub is a support ring which seats on a support shoulder af- [52] U.S Cl... 166/5, 175/7 fixed to the conductor casing head of an underwater well. An [5 l] Int. Cl 15211; 7/12 orientation pin projects radially from the conductor casing to [58] Field of Search 166/5, .6; Y which it isafi'lxed below the Casing head- Above the P a latch 175 5 10 ring is affixed to the conductor having a downwardly facing slightly tapered surface. Longitudinal ribs are affixed at regu- 5 References Cited lar intervals around the conductor between the latch ring and the support shoulder afiixed to the casinghead. Afiixed to the UNITED STATES PATENTS bottom of the tubular guide hub by a bolted flanged joint is an orientation sleeve. The lower end of the sleeve is formed by 1 i l Hayes l 22 cutting a left-hand helix and a right-hand helix so that they in- /1 Jones tersectinalowertipand an apex neartheflangedjoinLAt the 3'252528 5/1966 Nlcolson 166/5 apex a vertical pin slot is provided. A hold down latch as- 3256'937 6/1966 et sembly is provided on the tubular guide hub which has a latch 3259l91 7/1966 Mcchnwck 5 X member laterally engageable with the conductor latch ring 330L709 2/1967 Postlewane when the orientation pin and pin slot are fully engaged. The 332L015 5/1967 guide base is installed after the conductor casing and its riser i g l'l 1 567; have been installed and after further drilling has proceeded. omas 3,474,858 10/1969 Gibson et al 166/.5 16 Claims, 5 Drawing Figures United States Patent P [151 3,678,996

" d 51 July 25, 1972 ma i I Patented July 25, 1972 3 Sheets-Sheet 1 0 K N J @MAW P g g w I d M L J M 2 p. N gg gam a-Hm Patented July 25, 1972 3 Sheets-Sheet 2 ZZLM 477' FIVE) WELL COMPLETION AND APPARATUS This application is a continuation of application, Ser. No. 743,782, filed July 10, 1968, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is related to well completion methods and apparatus. More specifically it is related to underwater completion of oil and gas wells.

2. Description of the Prior Art An increasing proportion of drilling of oil and gas in the past several years has been at offshore locations. This has required the development of new drilling and completion equipment and techniques. Many offshore wells today are being completed with a Christmas tree on the ocean floor. Usually one or more flow lines emerge from the tree and run along the I relative to the well may be determined before it is aftixed'to ocean floor to a production storage location either on shore or e at a platform some distance away from the producing well.

In order to guide various components of the well into position it is necessary to provide a guide base which is usually anchored near the ocean floor in some manner in a fixed position relative to the wellhead or conductor casing. In most underwater completion methods the orientation of the flow line exits from the production tree is determined by the guide base since the tree is guided into position on cables extending vertically from the guide base to the drilling platform or vessel.

In the past the guide base has been installed prior to the conductor casing or it has been affixed to the conductor casing and lowered therewith into position as the conductor is jetted, driven or run in a drilled hole. In these methods it is not uncommon for the guide base to be damaged requiring expensive repair. Furthermore, if the well is a dry hole or is abandoned before completion, the guide base may not be removable, resulting in the loss of an expensive piece of equipment. Still further, the final orientation of the guide base is not always predictable. Since the guide base position controls the Christmas tree and flow line orientation, an unfavorable alignment may occur.

SUMMARY OF THE INVENTION The present invention comprises a method of drilling and completing an underwater well comprising the steps of: installing a conductor casing and wellhead assembly on the floor of a body of water; completing drilling operations; lowering a guide base through the body of water around the conductor and wellhead assembly; remotely affixing the guide base to the assembly in a predetermined angular orientation relative thereto; and completing the well. The guide base comprises: a hub member having a vertical passage therethrough telescopically positionable around the assembly; structural members projecting radially outward of the hub member; guide members attached to the structural members extending upwardly therefrom to the surface of the body of water; support means affixed to the hub member to cooperate with a portion of the assembly to support the guide base thereon; and hold down means affixed to the hub member engageable with a portion of the assembly to prevent longitudinal movement of the guide base relative thereto.

Since the guide base is not installed until the conductor and wellhead assembly have been installed and until drilling operations are complete it is not likely to be damaged. Furthermore, if the well should be a dry hole the guide base will never be installed and can be used at another location.

An orientation pin is provided on the conductor casing and an orientation sleeve is provided on the base of the guide base to cooperate in angular positioning of the guide base relative to the well. The orientation sleeve is so designed that on lowering of the guide base, it contacts the pin and automatically rotates the base to a predetermined position of orientation where it is held by a laterally acting latch.

The orientation sleeve may be affixed prior to the lowering of the guide base at sevcral'angular positions relative to the rest of the guide base so that the orientation of the guide base the conductor and wellhead assembly. Thus, subsequent flow exit and flowline orientation can be governed thereby.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages of the invention will become apparent fromthe following description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic view of an underwater wellhead assembly showing atypical guide base as used in the past;

FIG. 2 is a quarter section, partially in elevation of an underwater wellhead and conductor assembly and positionable guide base according to a preferred embodiment of the invention;

FIG. 3a is an elevational view of the orientation sleeve, partially shown in FIG. 2, of the guide base of that figure;

FIG. 3b is a half-section view of the orientation sleeve as taken along lines 35-3!) of FIG. 3a; and

FIG. 4 is a detailed section'view of the latch assembly and guide sleeve connection of the preferredembodiment shown in FIGS. 2, 3a and 3b. I

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, a typical underwater wellhead and guide base assembly, as used in the past, is shown. A conductor pipe and wellhead assembly 2 penetrates the ocean floor Affixed to the conductor 2 is a guide base 3 which in this drawing has four guide columns 4 extending upwardly therefrom. Guide cables 5, attached to the ends of guide columns 4, extend to the surface (not shown) where they are attached to a working platform during drilling completion or work-over operations. A Christmas tree 10 is shown lowered into position and connected to the well by a remote connector 20. Several such remote connections are commercially available. To guide the tree 10 and connector 20 into position, guide tubes 21 are connected by structural supports 22 to connector 20. Cables 5 pass through the tubes 21 and initially guide the tree 10 and connector 20 as they are lowered to the ocean floor. Bell bottoms 23 provide final alignment as tubes 21 en- 7 gage guide columns 4.

The production tree 10 shown in FIG. 1 is a dual completion tree. A single completion or other multiple completion may just as easily be performed with the present invention, the dual tree being used for descriptive purposes only. Production tree 10 includes master valves. 11, swab valves 12, diverter valves 13, and a valve selector 14 which is connected to a remote control station for selective operation of the various valves.

Connected to the dual production strings of tree 10 are flow loops 25 with wye valves 26 and cross-over valve 27. Crossover valve 27 is normally closed; but, during pigging operations it may be opened to allow reversal of flow in flow loops 25 so a pig" which has entered the flow loops may be returned to its launching point on shore. Flow loops 25 may be connected in several different ways to flow lines 30. There have been a number of remote flow line connectors developed only recently. However, for purposes of description only, simple pipe couplings 31 are shown.

Flow lines 30 may run along the ocean floor to a storage location either on shore or at a platfonn some distance away from the well. In any event, it is clear that flow loops 25 should be properly placed in order to mate with flow lines 30 to provide a smooth flow path. This is particularly true when the use of through-flowline tools is contemplated. It is also clear that the orientation of guide base 3 determines the orientation of tree 10 and the locationof flow loops 25. However, since the typical guide base of the past was affixed to the conductor casing before the conductor was installed, the final orientation of the guide base was uncertain. In addition, the guide base was subject to damage during installation and further drilling.

The guide base of the present invention is not installed until after the conductor is installed and after it is relatively certain that the well will not be a dry hole. Then it may be installed in a number of positions around the conductor allowing flow lines to exit in a 360 range of directions relative to the well. The guide base is also less likely to be damaged since the conductor is already firmly set before the base is installed.

Referring now-to FIG. 2, one embodiment of the invention will be described for use with an underwater extended casing method of completion. The first step in the extended casing method is to drive, jet or set in a drilled hole on the ocean floor a conductor casing 40. Attached to the upper end of conductor 40 is a casing head 41 which is provided on its interior with a support shoulder 42 for the subsequent suspension of other casing and tubing strings. The conductor 40 is installed with a riser 44 connected thereto through a connector joint 45. Riser 44 extends upwardly to the working platform (not shown). Connector 45 and casing head 41 are prevented from premature disengagement by a shear pin 46.

An orienting pin 50 is welded to conductor 40 at a point below casing head 41. A guide base support ring 52 is welded around the exterior of casing head 41 and another ring 53 is welded to conductor 40 slightly above pin 50. A number of longitudinal guide ribs 54 are radially disposed around con-' ductor 40 and head 41 between

rings

52 and 53. When the conductor 40 and riser 44 are run, riser 44 is marked so that the angular position of orienting pin 50 will be known when the conductor is finally set. It is, therefore, important not to use clamps, threads or other type riser joints which may turn during installation.

After the conductor and riser are run, casing 60 and other casing (not shown) are run during further drilling operations. Casing 60 is connected to hangerhead 61 which is supported on conductor casing head support shoulder 42. Other hangerheads such as 62 may also be concentrically supported within the well. After drilling is completed pack-offs may be installed in some of the annular spaces between casing strings and preparation made to install a tubing head and finally a Christmas tree.

If the tubing head does not have a side outlet it may be installed before installation of a guide base and removal of riser 44. At this point the guide base designated generally at 100 may be placed around riser 44 at the water surface and lowered into its final position shown in FIG. 2.

Guide base 100 comprises a tubular guide hub 101, a support ring 102 affixed to the upper end of hub 101 and a base ring 103 affixed to the lower end of hub 101. A number of

structural support members

105 and 106 projecting outwardly of hub 101 are radially disposed at regular intervals thereabout. Rigidly attached near the outer ends of

support members

105 and 106 are guide columns 108 projecting upwardly therefrom. Any number of guide columns may be used in any desired geometrical arrangement. It is quite common to use four columns in a square configuration. The axes of guide columns 108 are substantially parallel to the axis of the well. Guide cables 109 are attached to the top of columns 108 and pass upwardly therefrom through the water to the surface.

Attached to the bottom of base ring 103 by a plurality of bolts is orientation sleeve 1 10. The construction of orientation sleeve 110 can be best understood with reference to FIGS. 3a and 3b. The sleeve comprises a tubular portion 111 surrounded at the top by an annular ring or flange 112 which is welded thereto. The lower end of tubular portion 111 is defined by a left-hand and right-hand helix intersecting at a lower tip 113 and apex 114, the top and apex being displaced from one another by an angle of 180. A vertical pin slot 1 is machined at apex 114. The helix cuts provide

cam surfaces

116 and 117 so that upon contacting a pin such as pin 50 in FIG. 2, sleeve 110 will rotate relative to the pin and move downwardly on one of the cam surfaces until the pin 50 engages pin slot 1 15. If cam surface 1 16 contacts the pin, sleeve 110 will rotate in a right-hand direction. If cam surface 117 contacts the pin, the sleeve 110 will rotate in a left-hand direction.

Looking also now at FIG. 4, flange 112 is provided with a number of bolt holes 120 through which orientation sleeve 110 is attached by bolts 121. These bolts 121 may be removed and orientation sleeve 110 rotated with respect to guide hub 101 to give the desired general annular position of guide columns 108 with respect to the well head before lowering the guide base into position. Then the entire guide base assembly 100 is lowered on cables 109 around riser 44 and conductor 40 until one of the cam surfaces 116, 117 of orienta tion sleeve contacts pin 50. Further lowering will cause the entire guide base to rotate due to the cooperation of pin 50 and one of the cam surfaces until it comes to rest on pin 50 engaging slot 115.

To prevent upward movement of the guide base assembly 100, a plurality of latch assemblies are provided around base ring 103. The latch assembly comprises housing 131 welded to ring 103, spring 132, laterally movable latch 133, spring retainer 134 connected to housing 131 by bolt 135, and latch retainer pin 136. A lateral slot 137 is provided in the wall of housing 131 which prevents rotation of latch 133 but allows it to be retracted from the inwardly projected position shown in FIG. 2 to a position not penetrating the inner diameter of base ring 103. Latch 133 has a lower cam surface 138 which on lowering of the guide into position cooperates with an upwardly facing cam surface 139 on ring 53 to retract latch 133 until it is in position to engage the lower surface 140 of ring 53. Latch 133 and surface 140 are provided with a cooperating locking taper 141 so that an upward force against the guide base assembly 100 will not cause latch 133 to be retracted. Should it be desired to subsequently remove the guide base 100, the removal of bolt and retainer 134 would allow retraction of latch 133 and consequently the release of the guide base 100.

After the guide base 100 is firmly attached, riser 44 would be removed and the well would be completed by running tubing, installing a Christmas tree and connecting flow lines. Since the orientation of the Christmas tree will be governed by the guide base, it is also necessary, in a multiple completion well, to orient the tubing strings in a proper relationship with the guide base. This assures proper registration of the Christmas tree bores and tubing strings when the Christmas tree is connected to the wellhead. In order to properly orient the strings a connector and riser are first remotely attached to the tubing head. The connector is provided with an internal alignment means such as a vertical slot. The connector and slot are prepositioned with respect to the guide base by guide arms which engage the guide base guide columns. The tubing strings and their respective hangers are then lowered into the tubing head on a special tool. The tool is provided with a means for engaging the alignment slot in the connector at a predetermined angular relationship with the guide base. Such connectors and tools are presently known in the petroleum industry. Therefore, the details of their construction will not be described herein.

After the tubing strings have been properly installed, the connector and riser would be removed. Then the Christmas tree would be lowered into position for connection to the wellhead with remote connection means. Guide arms would be attached to the tree cooperating with the guide base column to properly orient the tree in relationship to the guide base and tubing strings.

As previously stated, the foregoing procedure would be followed if the tubing head has no side outlet. However, if the tubing head does have a side outlet, the tubing head might not be installed until after the guide base has been installed and the conductor riser removed. The tubing strings and Christmas tree would be oriented and installed in the same manner as previously described.

Thus, an easily and properly oriented guide base may be installed at an underwater well. Since it is not installed until after the conductor casing, it is less likely to be damaged and should the well be a dry hole, it might not be installed at all, preventing the loss of an expensive guide base.

Although only one preferred embodiment has been described herein, it is obvious that one skilled in the art aided by this disclosure could devise alternative designs. For instance, the orientation pin could be affixed to the orientation sleeve and made engageable with a cam surface provided around the conductor and wellhead assembly. Or, the orientation sleeve could be attached to the upper part of the guide base. Other cam configurations could also be used. In any event, these alterations would only be variations utilizing the principles of and in the spirit of the invention.

1 claim:

l. A method of drilling and completing an underwater well comprising the steps of:

installing a conductor casing and wellhead assembly in the floor of a body of water;

completing drilling operations;

lowering a guide base through said body of water around said conductor and wellhead assembly;

remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and completing the well; characterized by afiixing a riser to said wellhead and conductor assembly, lowering a tubing head through said riser and installing said tubing head within said wellhead prior to said lowering of said guide base.

2. A method of drilling and completing an underwater well comprising the steps of:

installing a conductor casing and wellhead assembly on the floor of a body of water;

completing drilling operations;

remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and completing the well; characterized by the further steps of:

affixing a riser to said wellhead and conductor assembly prior to lowering said guide base through said body of water, said riser being surrounded by said guide base as said guide base is lowered through said body of water; removing said riser; and

installing a tubing head after said guide base is lowered and affixed to said conductor and wellhead assembly.

3. A method of drilling and completing an underwater well comprising the steps of:

completing drilling operations;

lowering a guide base through said body of water around said conductor and wellhead assembly; remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and

completing the well; characterized by the further steps of: affixing a first orientation means to said conductor and wellhead assembly prior to said installation thereof; and prior to lowering of said guide base, angularly positioning a second orientation means on said guide base relative to said first orientation means to automatically cause said guide base to seek said predetermined angular orientation on said first and second orientation means engaging each other as said guide base is lowered around said conductor and wellhead assembly.

4. An underwater well guide base for remotely affixing to a conductor and wellhead assembly located on the floor of a body of water comprising:

a hub member having a vertical passage therethrough telescopically positionable around said assembly; structural members projecting radially outward of said hub members;

guide members attached to said structural members for ex tending upwardly therefrom to the surface of said body of water;

support means afiixed to said hub member to cooperate with a portion of said assembly to support said guide base thereon; and

hold down means affixed to said hub member self-engageable with a portion of said assembly on lowering said guide 5. An underwater well guide base for remotely affixing to a 4 conductor and wellhead assembly located on the floor of a body of water comprising:

a hub member having a vertical passage therethrough telescopically positionable around said assembly;

structural members projecting radially outward of said hub members;

guide members attached to said structural members for ,ex-

tending upwardly therefrom to the surface of said body of water;

support means affixed to said hub member to cooperate with a portion of said guide base thereon; and

hold down means affixed to said hub member engageable with a portion of said assembly to prevent longitudinal movement of said guide base relative thereto; characterized in that said guide base and said assembly are each provided with orientation means engageable with each other whereby said guide base is automatically positioned around said assembly in a predetermined angular relationship thereto as it is lowered into said support position, said orientation means comprising a pin member projecting radially from one of said guide base and said assembly and a substantially 360 cam means surrounding the other of said guide base and said assembly, said pin contacting said cam means as said guide base is lowered toward said support position causing said guide base to rotate less than 180 into said predetermined angular position.

6. The guide base according to claim 5 characterized in that said pin member is affixed to said assembly and said 360 cam means is defined by right and left hand helix cuts on the base of a tubular sleeve attached to said guide base, said helix cuts intersecting at a lower tip and an upper apex angularly displaced from each other on said sleeve by approximately 180, said apex opening into a pin slot engageable by said pin when said guide base is rotated to said predetermined angular position.

7. The guide base according to claim 6 characterized by said tubular sleeve being positionable on said guide base in a plurality of angular positions relative thereto.

8. Underwater well drilling and completion apparatus comprising:

a conductor casing and wellhead assembly positioned on the floor of a body of water, said assembly having an upwardly facing support shoulder, a downwardly facing latch shoulder and orientation means on the exterior thereof; and

a guide base having a hub member with a vertical passage therethrough telescopically positionable around a portion of said assembly, rigid structure members radially projecting from said hub member, guide means connected to said structure members extending upwardly therefrom, a downwardly facing support shoulder engageable with said assembly support shoulder to limit downward movement of said guide base, orientation means attached to said hub engageable with said assembly orientation means to orient said guide base relative to said assembly in a predetermined angular position on said guide base being lowered around said assembly, said hub orientation means being removable from the rest of said guide base for reconnection at any one of several angular positions relative thereto through a range of 360, and latch means attached to said hub, engageable with said assembly latch shoulder to hold said guide base to said assembly in said predetermined angular position.

9. Underwater well drilling and completion apparatus as set forth in claim 8 characterized by a conductor riser connected to said assembly and extending upwardly therefrom to the surface of said body of water, said guide base being positionable over the end of said riser for lowering thereabout to said assembly.

l0. Underwater well drilling and completion apparatus as set forth in claim 8 characterized in that said assembly orientation means comprises pin means radially projecting from said assembly and said guide base orientation means comprises a tubular sleeve affixed to said hub and concentric therewith, said sleeve having a cam means about its circumference engageable with said pin on lowering of said guide base around said assembly to rotate said guide base into said predetermined angular position regardless of its position on initial engagement.

ll. Underwater well drilling and completion apparatus a set forth in claim 10 characterized in that said cam means comprises two opposite hand spiral surfaces intersecting at a point registering with said pin means when said guide base is in said predetermined angular position.

12. Underwater well drilling and completion apparatus comprising:

a conductor casing embedded in the floor of a body of water;

wellhead means connected to said casing near the floor of said body of water having an annular upwardly facing support surface thereon;

a guide base surrounding a portion of said conductor supported on said wellhead support surface, said guide base comprising a tubular guide hub, structural members radially projecting from said hub and guide means linked to said structural means extending upwardly therefrom; and

orientation means comprising a pin member radially projecting from said conductor and a tubular sleeve attached at the base of said guide base, said tubular sleeve having a cam means thereabout engageable with said pin member on lowering said guide base from above said body of water to position said guide base in a predetermined angular orientation relative to said wellhead.

13. The apparatus set forth in claim 12 characterized in that said tubular sleeve may be connected to the base of said hub in a number of angular positions relative thereto for predetermining said orientation of said guide base relative to said wellhead.

14. The apparatus set forth in claim 12 characterized by hold down means comprising a ring attached to said conductor having a downwardly facing annular shoulder and latch means mounted on said guide base for lateral movement to engage said downwardly facing annular shoulder only when said guide base is at said predetermined angular position to hold said guide base against displacement therefrom.

15. The apparatus set forth in claim 15 characterized by a vertical slot in said tubular sleeve communicating with said cam means and engageable by said pin member only when said guide base is at said predetermined angular position.

16. Apparatus as set forth in claim 15 characterized by longitudinal guide ribs radially disposed around said conductor and connected between said wellhead annular support surface and said hold down ring, the upper face of said hold down ring being tapered to cooperate with a tapered portion of said latch means cooperating to retract said latch means on said guide base being lowered around said conductor until it reaches said predetermined angular orientation and said position of support on said wellhead support surface.

Claims

1. A method of drilling and completing an underwater well comprising the steps of: installing a conductor casing and wellhead assembly in the floor of a body of water; completing drilling operations; lowering a guide base through said body of water around said conductor and wellhead assembly; remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and compLeting the well; characterized by affixing a riser to said wellhead and conductor assembly, lowering a tubing head through said riser and installing said tubing head within said wellhead prior to said lowering of said guide base.

2. A method of drilling and completing an underwater well comprising the steps of: installing a conductor casing and wellhead assembly on the floor of a body of water; completing drilling operations; lowering a guide base through said body of water around said conductor and wellhead assembly; remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and completing the well; characterized by the further steps of: affixing a riser to said wellhead and conductor assembly prior to lowering said guide base through said body of water, said riser being surrounded by said guide base as said guide base is lowered through said body of water; removing said riser; and installing a tubing head after said guide base is lowered and affixed to said conductor and wellhead assembly.

3. A method of drilling and completing an underwater well comprising the steps of: installing a conductor casing and wellhead assembly on the floor of a body of water; completing drilling operations; lowering a guide base through said body of water around said conductor and wellhead assembly; remotely affixing said guide base to said assembly in a predetermined angular orientation relative thereto; and completing the well; characterized by the further steps of: affixing a first orientation means to said conductor and wellhead assembly prior to said installation thereof; and prior to lowering of said guide base, angularly positioning a second orientation means on said guide base relative to said first orientation means to automatically cause said guide base to seek said predetermined angular orientation on said first and second orientation means engaging each other as said guide base is lowered around said conductor and wellhead assembly.

4. An underwater well guide base for remotely affixing to a conductor and wellhead assembly located on the floor of a body of water comprising: a hub member having a vertical passage therethrough telescopically positionable around said assembly; structural members projecting radially outward of said hub members; guide members attached to said structural members for extending upwardly therefrom to the surface of said body of water; support means affixed to said hub member to cooperate with a portion of said assembly to support said guide base thereon; and hold down means affixed to said hub member self-engageable with a portion of said assembly on lowering said guide base therearound to prevent longitudinal movement of said guide base relative thereto; characterized in that said guide base and said assembly are each provided with orientation means engageable with each other whereby said guide base is automatically positioned around said assembly in a predetermined azimuthal relationship relative to the vertical axis of said wellhead assembly as said guide base is lowered into said support position.

5. An underwater well guide base for remotely affixing to a conductor and wellhead assembly located on the floor of a body of water comprising: a hub member having a vertical passage therethrough telescopically positionable around said assembly; structural members projecting radially outward of said hub members; guide members attached to said structural members for extending upwardly therefrom to the surface of said body of water; support means affixed to said hub member to cooperate with a portion of said guide base thereon; and hold down means affixed to said hub member engageable with a portion of said assembly to prevent longitudinal movement of said guide base relative thereto; characterized in that said guide base and said assembly are each provided with orientation means engageable with each other whereby sAid guide base is automatically positioned around said assembly in a predetermined angular relationship thereto as it is lowered into said support position, said orientation means comprising a pin member projecting radially from one of said guide base and said assembly and a substantially 360* cam means surrounding the other of said guide base and said assembly, said pin contacting said cam means as said guide base is lowered toward said support position causing said guide base to rotate less than 180* into said predetermined angular position.

6. The guide base according to claim 5 characterized in that said pin member is affixed to said assembly and said 360* cam means is defined by right and left hand helix cuts on the base of a tubular sleeve attached to said guide base, said helix cuts intersecting at a lower tip and an upper apex angularly displaced from each other on said sleeve by approximately 180*, said apex opening into a pin slot engageable by said pin when said guide base is rotated to said predetermined angular position.

8. Underwater well drilling and completion apparatus comprising: a conductor casing and wellhead assembly positioned on the floor of a body of water, said assembly having an upwardly facing support shoulder, a downwardly facing latch shoulder and orientation means on the exterior thereof; and a guide base having a hub member with a vertical passage therethrough telescopically positionable around a portion of said assembly, rigid structure members radially projecting from said hub member, guide means connected to said structure members extending upwardly therefrom, a downwardly facing support shoulder engageable with said assembly support shoulder to limit downward movement of said guide base, orientation means attached to said hub engageable with said assembly orientation means to orient said guide base relative to said assembly in a predetermined angular position on said guide base being lowered around said assembly, said hub orientation means being removable from the rest of said guide base for reconnection at any one of several angular positions relative thereto through a range of 360*, and latch means attached to said hub, engageable with said assembly latch shoulder to hold said guide base to said assembly in said predetermined angular position.

10. Underwater well drilling and completion apparatus as set forth in claim 8 characterized in that said assembly orientation means comprises pin means radially projecting from said assembly and said guide base orientation means comprises a tubular sleeve affixed to said hub and concentric therewith, said sleeve having a cam means about its circumference engageable with said pin on lowering of said guide base around said assembly to rotate said guide base into said predetermined angular position regardless of its position on initial engagement.

11. Underwater well drilling and completion apparatus a set forth in claim 10 characterized in that said cam means comprises two opposite hand spiral surfaces intersecting at a point registering with said pin means when said guide base is in said predetermined angular position.

12. Underwater well drilling and completion apparatus comprising: a conductor casing embedded in the floor of a body of water; wellhead means connected to said casing near the floor of said body of water having an annular upwardly facing support surface thereon; a guide base surrounding a portion of said conducTor supported on said wellhead support surface, said guide base comprising a tubular guide hub, structural members radially projecting from said hub and guide means linked to said structural means extending upwardly therefrom; and orientation means comprising a pin member radially projecting from said conductor and a tubular sleeve attached at the base of said guide base, said tubular sleeve having a cam means thereabout engageable with said pin member on lowering said guide base from above said body of water to position said guide base in a predetermined angular orientation relative to said wellhead.