US3047078A - Method and apparatus for offshore drilling - Google Patents

Description

July 31, 1962 w. R. POSTLEWAITE 73,047,078

METHOD AND APPARATUS FOR OFFSHORE DRILLING 5 Sheets-Sheet 1 Filed Oct.

IIIIIIIH ATTRNEYS y 1962 w. R. POSTLEWAITE 3,047,078

METHOD AND APPARATUS FOR OFFSHORE DRILLING Filed Oct. 1, 1958 5 Sheets-Sheet 2 July 31, 1962 w. R. POSTLEWAITE METHOD AND APPARATUS FOR OFFSHORE DRILLING 5 Sheets-Sheet 3 Filed Oct.

0 ll llV INVENTOR WILLIAM R. POSTLEWA/TE July 31, 1962 w. R. POSTLEWAITE METHOD AND APPARATUS FOR OFFSHORE DRILLING 5 Sheets-Sheet 4 Filed Oct. 1, 1958 IIHHHIIII II FIG.7

at! 5:225.ii.iununlivusnululinlmy 9 IN V EN TOR WILL MM R. Pas TLEWA/TE July 31, 1962 w. R. POSTLEWAITE METHOD AND APPARATUS FOR OFFSHORE DRILLING 5 Sheets-Sheet 5 Filed Oct.

FIG.1O

FIG.H

F l G 13 INVENTOR WILLIAM R. POSTLEWA/TE 3,947,678 METHOD AND APPARATUS FOR OFFSHORE DRILLING William R. Pcstlewaite, Menlo Park, Calif., assignor to California Research Corporation, San Francisco, Calif,

a corporation of Delaware Filed Oct. 1, 1958, Ser. No. 764,574 17 Ciaims. (Cl. 175--7) This invention relates to a method and apparatus for ofishore drilling and more particularly to means for driling a well bore from a floating drilling platform into a well site submerged below a body of water and subsequently for introducing equipment into said well bore from said floating platform.

It has been suggested heretofore that well bores be drilled in submerged locations from floating drilling platforms by attaching the platform to a submerged well site by flexible guide lines, lowering the well drilling apparatus along the guide lines into contact with the submerged earth and subsequently drilling the well bore by operation of the drilling equipment from the floating vessel. The guide lines serve also as a means for guiding into the well bore apparatus used for servicing or surveying the well. The guide lines used in the aforesaid method of drilling are flexible members which permit a displacement of the floating drilling platform with respect to the submerged well site and hence accommodate the motion of the platform while maintaining the connection between it and the submerged well opening.

However, one difficulty experienced with this method of drilling results from the essential flexibility of the guide lines. It has been found that subsurface water currents may bear against the guide lines, and the apparatus being guided along them, with such force that they will be forced out of alignment with the submerged well bore, even though the guide lines are held under tension. Hence the apparatus being lowered along the guide lines may engage the submerged wellhead equipment at an angle which makes it diflicult, if not impossible, to introduce the apparatus into the well bore, or which may damage the submerged equipment. In waters too deep for divers to repair such damage, the result may be the forced abandonment of the well. It has been found also that subsurface water forces may bear against the apparatus being guided to the well bore with such force that the guide arms connected between the apparatus and the guide lines may be broken, resulting in lost time on the drilling rig while the equipment is being repaired.

It is an object of this invention to provide a method and apparatus for forcibly pulling drilling or other apparatus downwardly from a floating platform to a submerged well opening and into alignment with the well bore by a means which can exert enough force to overcome the eflect of subsurface water currents and which does not depend on the use of guide lines.

A further object of this invention is to provide novel equipment for performing drilling and servicing operations on a submerged well bore from a floating drilling platform.

A further object of this invention is to provide a method for pulling or towing in a positive manner well working apparatus from a floating platform downwardly through a body of Water to a submerged well site by a towline which is attached to the lower portion of the well working apparatus and actuated by a winch means on the drilling platform to exert the force necessary to overcome the lateral displacement effects of the water currents and force the towed well working apparatus into alignment with the well bore.

Other objects of this invention will become apparent as the description of it proceeds hereinafter.

atent The objects of this invention are achieved by afiixing a base assembly to the submerged earth at the well site and mounting a towline on a pulley or sheave arrangement which is a part of the assembly. One end of the towline is attached to a winch mechanism on the drilling platform, and the other end is brought to the surface of the water and attached to a towing head which can be detachably connected to the apparatus to be pulled downwardly to the well opening. The pulley arrangement may be devised to place the latter end of the towline in substantially axial alignment with the longitudinal axis of the well bore when the towline is placed under tension to pull the towing head and the well working apparatus downwardly in substantial alignment with the well bore. The upper portion of the base assembly and the towing head are constructed with complementary surfaces which will engage to bring the pants into concentric alignment. Hencethe well working apparatus will be placed in coaxial alignment with the well bore into which it can be lowered by manipulation from the drilling platform.

Of some pertinence to this method of operation is a means for clearing the towline and the connection between it and the towing head from the passage to the well bore to prevent these parts from interfering with the well working equipment when it subsequently is lowered into the well bore. 1

The following specification, together with the accompanying drawings which form part of it, describes several modifications of apparatus for accomplishing the objects of this invention.

With reference to the drawings:

FIG. 1 illustrates in side elevation and partly in section apparatus made in accordance with this invention as employed during the initial drilling of a well bore into a submerged location.

FIG. 2 illustrates in side elevation and partly in section apparatus used in the method of this invention and shows a procedure for connecting wellhead control equipment to the submerged well opening.

FIG. 3 illustrates in side elevation and partly in section apparatus in accordance with this invention, and shows the wellhead control equipment attached to the submerged well opening and drilling equipment being pulled downwardly to the wellhead for insertion into the well bore.

FIG. 4 illustrates in side elevation and partly in section apparatus in accordance with this invention being used to drill a well bore into subterranean formations while the well opening is controlled by wellhead control equipment operated from the floating drilling platform.

FIG. 5 illustrates in side elevation and partly in section details of a modification of portions of a base assembly and a towing head made in accordance with this invention.

FIG. 6 is a plan view taken along the line 6-6 of FIG. 5.

HO. 7 illustrates primarily a modification of a towing head made in accordance with this invention and is directed particularly to a bail arrangement by which the towline is connected to the towing head.

FIG. 8 is a plan view taken along the line 8-8 of FIG. 7.

FIG. 9 illustrates in side elevation and partly in section another modification of a base assembly and towing head made in accordance with this invention.

FIG. 10 is a view in side elevation and partly in section directed primarily to a modification of a towing head.

FIG. 11 is a plan View taken along the line 11-11 of FIG. 10.

FIG. 12 illustrates in side elevation and partly in section a further modification of apparatus made in accordance with this invention.

FIG. 13 is a plan view taken along the line 13-13 of FIG. 12..

Referring to the drawings, and particularly to FIG. 1, there is illustrated an offshore drilling vessel 20 which has been anchored in a body of water 22 at a site where a well is to be drilled into the ocean bottom 24. A drill string and bit are suspended from the derrick 26 on the vessel and through a rotary table 28, and a hole 39 is drilled into the submerged earth of sufficient diameter to accept a length of conductor casing 32. A base assembly 34, which forms part of the apparatus of this invention, is connected to the top portion of the conductor casing.

In a preferred method for carrying out the positioning of the base assembly on the land surface at the bottom of the water, the base assembly with a length of conductor casing 32 attached thereto is suspended in the water through a well 36 in the central portion of the drilling vessel by lines 38 and 40 which are wound on respective Winches 42 and 44 as indicated by the phantom lines designated by the numeral 46. While the base assembly is thus held suspended, a drill string with a bit attached to the end thereof is passed downwardly through it to drill the bore hole 30 in the submerged earth.

7 With the drill and drill string remaining in the bore hole, the base assembly is lowered along the drill string until it'is seated at the ocean bottom, after which the casing 32 is cemented to the well bore by forcing a cementing material downwardly through the drill string. Thus the base assembly is firmly established at the submerged well site. Preferably the support line 40 is removed from the base assembly prior to lowering it to bottom. The line 38, which then is used to lower the base assembly, remains connected to it by a system of sheaves and pulleys,

' to be used subsequently for towing or pulling tools and equipment downwardly through the water to the well opening in a manner to be described hereinafter.

, Referring to FIG. 2, the base assembly 34 comprises a base member '48 which is designed with sufl'icient lateral dimension to bridge over the opening of the bore hole, which has been formed to receive the conductor casing, and has sufficient bearing area to position'the assembly on the surface of the land underlying the water and to prevent it from being submerged in thetbottom sediments. The base member has a cylindrical projection '50 extending downwardly from it which is rigidly connected to the conductor casing 32, which in turn is cemented in the bore hole by the cement 52. The base member has a central opening 54 in axial alignment with the depending conductor casing and hence with the well bore.

A cylindrical support element 56 is afiixed to the upper surface of the base member and projects upwardly therefrom in axial alignment with the conductor casing. The top portion of this cylindrical support element is flared in a conical form 58 which functions as a centralizing means for the apparatus pulled downwardly into contact with the base assembly. It will be understood that the cylindrical form of the element 56 provides a simple structural shape for supportingthe centralizing portion 53 and the sheave and pulley components of the apparatus to be described hereinafter. However, the concept of this invention is not limited-to this specific support means, but embraces other forinsof support means which will perform these same functions. a

In the embodiment of the invention illustrated in FIG. 2 an arm. 69 is pivotally connected at one end to a bracket 62 on the outer surface of the conical portion 58 of the cylindrical element 56 by a pin 64. The other end of this arm supports a pulley 66 which rotatesabout an axle 68. The arm is positioned on the assembly to swing toward and away from an opening 70 in the circumferential wall of the cylindrical support element 56, and the parts are proportioned to dispose the pulley within the cylinder when the arm is swung radially inwardly of it and to retract the pulley fromthe cylinder when the arm is swung radially outwardly. A hydraulic piston 72 is pivotally connected at one end to the outer wall of the conical por tion 58 and pivotally connected at its other end tothearm 69. The hydraulic. cylinder is energized through the hydraulic lines 74 and 76 to swing the arm about its pivot point.

A sheave 78 is rotatably mounted on the arm in a position between the pivoted end and the pulley 66 with its axle offset from a line extending between the pivot pin 64 and the axle 68 of the pulley. The towline 38 is mounted over the sheave and pulley, and one end 81 of this line is disposed within the cylindrical support element 56 while the other end 82, which is disposed exteriorly of the cylinder, continues to the surface of the water and is wound on the winch mechanism 42 on the drilling vessel When the arm 60 is swung about its pivot to place the pulley 66 within the cylindrical support element, its in-' alignment with the longitudinal axis of the base assembly 7 and the conductor casing 32. When tension is placed on the towline, the reaction between it and the arm 60 operates to maintain the end 'of the towline in this coaxially aligned position.

As the base assembly 34 initially is lowered to the bottom of the water, as described heretofore, preferably the end seof the towline 38 is connected to a stationary portion of the drilling vessel as indicated at 86 in FIG. 1, to be attached subsequently .to a towing head. Alternatively the towing head may be mounted in the base assembly and the towline connected thereto prior to the initial lowering. The towline 33 is payed off from its Winch 42 and runs through the sheave-and-pulley arrangement on the base assembly while the lowering operation is proceeding. This towing head affords a means for attaching the end of the towline to tools and equipment which are to be forcibly pulled downwardly through the Water and subsequently inserted into the well bore.

One modification of a towing head 38 made in accordance with this invention is illustrated in FIGS. 2 and 3. This device is made with a cylindrical peripheral surface 96 which tapers at its bottom portion 100- in a conical form which is complementary to the conically flared portion 58 of the cylindrical support element 56 of the baseassembly. A ring 102 is rotatably mounted on antifriction hearings on the lower portion of the towing head in coaxial alignment with the longitudinal axis thereof. A

hinged bail 164- is pivotally mounted on the ring to swing' ina direction transverse to the longitudinal axis of the,

towing head.

The towing head is made with an inner cylindrical chamber 106 which is continuous through it and open at the top and bottom ends. The wall 1% of'this cylindrical chamber is sealed to the top wall 110 and the bottom 100 V towline to the surface of the water as the towline is' slacked off from its winch. This structure provides a means for retrieving the towing head and the towline from a submerged location if the towing head becomes disconnected from the equipment pulled downwardly through the water. a

The towing head has a cap portion 114 bolted to its top surface, and the cap is made with a radially inwardly projecting end portion 116 through which there is a central opening 118 in alignment with the cylindrical chamber 106. Preferably the cap portion is made in two half W sections 120 and 122 which can be assembled around a drill string or other tool inserted into the chamber 106 and then bolted to the towing head. The radially inwardly directed end portion 116 of the cap is constructed to abut a shoulder 124 on the tool 126 disposed Within the a towing head to prevent the tool from being withdrawn out of the head in an upward direction. The opening 11?; in the top portion of the cap is selected to fit snugly around the equipment inserted through it, but with sufiicient internal diam ter to permit this equipment to be lowered through the towing head when the latter engage the centralizing cone on the base assembly.

After the towing head has been pulled down into engagement with the base assembly the hydraulic cylinder 72 is energized to swing the arm 5% away from the opening 70 in the cylindrical support element 56. The end 80 of the towline and the bail 194 are thus displaced from axial alignment with the base assembly and removed from a position where they would interfere with the equipment lowered downwardly through the base assembly from the towing head. Suihcient tension is maintained in the towline 38 to hold the towing head in engagement with the base assembly.

Preferably the pivots 128 and 13%} of the bail are not located on a diameter of the ring, but are offset from the diameter to provide an eccentric loading on the ring when the bail is pulled outwardly by the towline. The eccentric loading will cause the ring to rotate in a direction to orient the pivot points of the bail transversely of the direction of pull on the towline 3i and thus permit the bail to be swung away from the longitudinal axis of the base assembly to the clearance position described'heretofore.

After the base assembly is secured to the submerged earth, the towline and towing head are used to pull a drill string 132 with a drill bit attached to the end of it down to the base assembly and in axial alignment with the conductor casing 32 in the manner illustrated in FIG. 1. A well bore is drilled into the earth to accept a string of surface casing 134, FIG. 2, which is pulled downwardly rorn the drilling vessel and into alignment with the well bore in the manner of the drill string as explained heretofore. The surface casing is supported in the derrick 26 by a string of tubing, to winch it is attached by a connection, such as a safety joint, which can be released by remote operation.

The surface casing has the mandrel 135 of a safety joint attached to its uppermost portion and may be supported in the base assembly by easing hangers 13% with the mandrel extending above the base plate and within the cylindrical support element 56. The string of tubing which connects the surface casing with the drilling vessel is used as a conduit to cement the surface casing in the well here. This string of tubing is then disconnected from the surface casing at the safety joint and returned to the drilling vessel along with the towing head which was used to pull it downwardly through the water. The towing head remains connected to the lower end of the tubing string through the abutting interengaging surfaces between the parts and, through the towline, provides a restraint to control the lower end of the tubing string as it ascends through the water.

The towing head is now used to pull down to the submerged well opening wellhead control equipment which is then latched and sealed onto the safety joint mandrel. As illustrated in FTGS. 2 and 3, this equipment may comprise a series of blowout preventers 1 -3 3, and a drilling head 1 52, which are connected together in axial alignment to provide a passage through the eguipment to the well bore. A length of casing 144 is connected to the lower portion of the control equipment, and the barrel or female portion of the safety joint, which in this instance corresponds to the tool 126 mentioned heretofore, is fixed to the lower end of this tubin g.

An assembly 145 comparable to the base assembly 34- described heretofore is fixed to the top portion of the drilling head when the wellhead control equipment is as sembled together at the surface of the water and prior to pulling it downwardly to the submerged well site. This assembly comprises a centralizing means for a second towing head and a sheave-and-pulley arrangement for 6 mounting a second towline. The second towline is used to pull well drilling or working apparatus downwardly through the water to the submerged wellhead control equipment, through which it can be lowered into the well bore.

The assembly 146 shown in H63. 2 and 3 is a -modification of the base assembly 34 described heretofore. In it, 'a cylindrical support element 148 has an opening 156 in its circumferential wall. A pulley 152 is rotatably mounted on one end of an arm 154, the other end of which is connected to a bracket on the exterior of the cylindrical support by the pivot pin 156. The arm is swung about its pivot pin by the hydraulic cylinder 158 to move the pulley through the opening 15% to a position within the cylindrical support element and to retract it therefrom. A sheave 16% is rotatably mounted on a bracket 162 secured to the exterior of the cylindrical support element, and a towline 164 is mounted over the sheave and pulley with one end portion 166 disposed within the cylindrical support and the other end portion 168 disposed exteriorly of it and connected to a winch mechanism on the drilling platform. This winch mechanism may be the winch 44 employed initially in supporting the base assembly 34 in a suspended position below the drilling vessel.

The end portion 166 of the towline is connected to a towing head 17%. In this modification the towing head is constructed with a cylindrical central element 172 which has a lower end of reduced diameter on whi h is mounted on antifriction bearings a rotatable ring 174. The ring supports. a hinged bail 176 on diametrically disposed pivots 178 and 189. centralizing rib projections 182 are affixed to the outer surface of the central cylindrical element 172, and a radially extended circular structure 184 is affixed to its top portion. The top opening of the central cylindrical element has aflixed to it a split flange 186 through the central portion of which is an opening 188 of sufficient diameter to accept a string of tubing or the like. The flange extends radially inwardly of the inner wall of the central cylindrical element to form a shoulder 19% which will abut a complementary shoulder 192 on a well working tool 1% when the towing head is pulled in a downwardly direction. The flange is formed with a collar 194 which projects downwardly into the cylindrical element 172 and fits snugly around the outer circumference of the tool to centralize the latter within the towing head.

In this modification of the invention the axis of diametrically disposed pivots 17$ and 18d of the bail is brought forcibly into alignment transversely of the direction of displacement of pulley 15% by a cam 1% which is secured within the cylindrical support 172. The has similar carnming surfaces 198 which are symmetrically disposed on each side of a transverse axis of it. Each c amming surface engages a cam follower, such as a respective roller 2%, mounted on the ends of the bail pivots. The interaction between the rollers and the surfaces rotates the ring 174 to place the rollers within respective detents 202 as the towin head is pulled downwardly into engagement with the cam. During this operation the centralizing rib projections 182 will place the towing head in axial alignment with the longitudinal axis of the cylindrical support 172, and the radially extended projecting structure 1% ultimately will contact the conically dared upper por tion 294 to assist in centralizing the towing head in position and to limit the amount of its downward travel.

When the bail pivot rollers 2% move into the detents 2&2, the axis of the bail mounting is positioned transversely of the direction of the lateral pull of the towline. Thus, when the pulley 152 is retracted from the cylindrical support element by the hydraulic cylinder 153, the bail and the end of the towline connected to it swing laterally. to clear the vertical passage through the support element, an the tool 1% can be lowered through the assembly and through the wellhead control equipment and into the well bore without interference.

When the wellhead control equipment and the tow-in assembly described heretofore are assembled together at the surface of the water, the towing head 38 is connected to the lower end of the length of casing 144, and the assembly is pulled downwardly through the water by the towline 38 into contact with the base assembly 34. During this procedure the wellhead control assembly is sup ported fiom the drilling vessel primarily by the string of tubing 266, and this tubing is now lowered by a hoist means 298 on the drilling vessel until the barrel 126 of the safety joint engages the mandrel 136 and automatically latches onto it. Thus, the well control equipment is securely connected to the well opening. As illustrated in FIG. 3, the towline 38 now remains idle while the towline 164 is used to pull apparatus subsequently used for drilling or working the well downwardly from the drilling vessel to the submerged wellhead.

The wellhead control equipment is actuated by remote operation from the drillin'g vessel through the hydraulic lines designated generally as 210, FIG. 4. As shown in FIG. 3, mud returnline 212 is connected to the assemderstood in the art.

FIG. 4 illustrates the arrangement of the drilling apparatus when the procedures described heretofore have been accomplished. The drilling vessel 20 is anchored over the submerged well site, and the base assembly 34 has been secured to the underwater bottom. The well control equipment with the towing apparatus mounted on the top of it has been connected to the string of surface casing 134 by the safety joint to achieve control of the flow of drilling mud and to afford control of the well if high pressure gas pockets or oil formations are penetrated by the drill bit. A string of drill tubing 206, to the end of which a drill bit 218 is attached, has been pulled downwardly to the wellhead assembly by the towline 164 and inserted into the Well bore by further lowering it from the drilling platform by the hoist means 208. 'The drill string is rotated by the' rotary table 28 aboard the drilling platform to drill the Well.

bore.

When it becomes necessary to change a drill bit, the drill string is raised by the hoist means on the drilling vessel. As the drill bit moves upwardly it enters the towing head 170, to assume the position shown in FIG. 3, with the radially projecting shoulder 192 on the drilling equipment engaging the flange member 186. A restraining tension, less than the lifting force exerted on the drill string, is held on the towline 164 while the drill string continues to be raised to control the ascent of the h equipment. The drill string carries the towing head to the surface of the water and thence aboard the drilling a applies also to other well working equipment than drill strings which it is desired to insert into the well bore.

FIG. 5 shows a further modification of structure made in accordance with this invention; In this modification,

a pulley 220 is supported on a pivoted arm 222 which is retracted from the opening 224 in the cylindrical support member 226 by' a spring 228 when tension is released from the towline 230. The towline is mounted over the pulley and thence over a sheave 232 which is supported on the outer Wall of the support element 226 wardly of the axle 236 of the pulley when the arm 222 s is in its retracted position. The towline continues over a a r o second sheave 238 which is mounted on a bracket 24%) supported on the exterior wall of the support element This arrangement of sheaves and pulleys produces a resultant force on the pulley 226 when the towline is placed under tension which causes the arm 222 to swing inwardly to dispose the pulley within the interior of the cylindrical support element 22-6 with the end 242 of the towline in coaxial alignment with the axis of the wellhead assembly. This aligned position automatically is maintained by the towline as long as there is sufficienttension on it. However, when tension is released from the towline, the spring 228 swings the arm 222 radiallyoutwardly and clears the vertical opening through the wellhead equipment for passage of the tools lowered from the drilling platform. j

The plan view of FIG. 6 illustrates the disposition of the bail pivots 244 and 246 for the bail 248 These pivots, as explained heretofore, are, in this modification of the invention, displaced from the diametrical axis of the supporting ring 250 by a distance indicated by the letter x to produce an eccentric unbalancing force on the ring to cause it to turn to place the axis of the bail pivots transversely of the direction of pull of the towline to I insure that the bail will always swing laterally away from the vertical passageway through the assemblage to leave it unobstructed. I The end 242 of the towline is slidably engaged by a friction slip brake means 251 which is mounted on the arm 222 to contact the towline when it passes over the pulley 220. The frictional engagement between the brake means and the towline causes the end portion'of the latter to be moved laterally with the arm as it is swung to a retracted position.

The towing head 252 in the modification of the invention shown in FIG. 5 includes a buoyancy chamber 254 which projects outwardly from the exterior wall of a cylindrical shell 256 and is designed with suflicient buoyant force to return the end portion 242 of the towline to the surface as the towline is unreeled from the winch mechanism aboard the drilling platform.

A split flange 258 is detachably securedto the upper end of the towing head, and a complementary split sleeve 260 is aflixed to the flange and projects downwardly into the interior chamber of the outer shell 256. 'The flange is extended radially inwardly to closely approach a string of tubing 262 .or other apparatus inserted through a central opening in it, but with sufficient clearance to allow the tubing string to be moved downwardly through the towing head after the latter lands in final position in the element 226. The flange forms an abutment 264 to engage a shoulder 266 on the drilling tool when the latter is raised upwardly, and the sleeve 26! forms a centralizing means for the tool to place it in alignment with the longitudinal axis of the Well bore when the tool is.

pulled downwardly to the wellhead under the action'of the towline 230. The two halves of the flange 258 and its afiixed sleeve are made to be assembled around a tubing string after the drilling tool is inserted through the towing head. Various flanges and sleeves having different internal diameters of their openings maybe made available to accommodate different sizes of drilling tools.

The lower end of the towing head has fixed to it a nose portion 268 of reduced external diameter to providea surface 270 on which the ring 250, which holds the bail in a position in vertical alignment with the pulley, but

with the axle 234 of the'sheave displaced radially in-' 248, is mounted on antifriction bearings 272. V

FIGS. 7, 8 and9 illustrate another modification of apparatus made in accordance with this invention. In this 7 modification a pulley 274 is rotatably mounted on an axle 276 which is fixed to a bracket'structure 273 secured to the cylindrical support element 280. The pulley is positioned on. the support element with a portion of its inner rim projecting through the opening 2%2 in the circumferential wall of the element to be disposed within the interior chamber 284 thereof.

A sheave 286 is mounted on a bracket 288 extending from the exterior cated by the numeral 300, FIG. 9. The curved bail, in

contact with the top of the support element 28! acts as a camming means for placing the bail pivot axis transversely of the direction of the lateral component of tension in the end portion of the towline which is mounted over pulley 274. As best seen in FIGQ8, the moment arm y between the axis of rotation of ring 293 and the radial force point of contact of the curved bail with the flared upper portion of the support element produces a force which invariably will cause the ring 25 3 to rotate in a direction to align the pivot axis of the bail transversely of the direction of towline pull.

In this modification, the fixed position of the pulley 274 is selected to pull the bail clear of the vertical passageway through the wellhead equipment when the towing head is seated on the support element and the towline is held under tension.

The towing head illustrated in this modification of the invention comprises a cylindrical shell 3% which has centralizing projections 366 on its outer surface and a radially projecting, reinforced plate structure 3% afiixed to its upper portion to engage the conically flared upper end 302 of the support element to help center and to limit the downwardtravel of the towing head. A split flangeand-sleeve arrangement 31% similar to that described heretofore with relation to FIG. 5 is employed to engage and center the drilling tool as it is pulled downwardly through the water to the well head equipment.

FIGS. and 11 illustrate a further modification of apparatus made in accordance with this invention. In this modification the towing head 312 has a U-shaped torque arm element 314 affixed to and projecting radially outwardly from its outer surface toward and surrounding the towline 315. This U-shaped element is positioned to maintain the pivot axis 318 of the bail 32% aligned transversely to the direction of towline pull when the towing head is seated in the support element 3-22. Thus the bail is positioned to be swung clear of the opening through the wellhead equipment when the arm 324 retracts the pulley 326 from the opening 328'in the side of the support element through the action of the hydraulic cylinder 33%.

The modification of the invention illustrated in FIGS. 12 and 13 illustrates another means for attaching the towline 332 to the towing head 334 in a manner to cause the towing head to be centralized with the cylindrical support element 336 as it is pulled into engagement with latter. The towline is mounted over a fixed pulley 333 head are eccentric to the longitudinal axis of the well-,

head equipment.

As the towing head is pulled downwardly through the water, it may assume the position. illustrated by the phantom lines designated by the numeral 350, in which case it is in axial alignment with the wellhead equipment, or by the phantom lines designated by the numeral 352, which represents the maximum eccentricity which the towing head canassume as it is pulled into engagement with the support element. towing head first contacts the conicmly flared upper portion 354 of the support element a vector couple acts, on the ring 34s as an effect of the reaction between the point of contact with the centralizing cone and the eccentric pull of the towline. This causes the ring 346 to rotate as it proceeds downwardly along the inner wall of the flared portion of the support element. The rotation continues until the towing head has moved into axial alignment with the base element. The centralizing rib projections 356 and the radially extended top portion 358 assist in bringing the towing head into coaxial alignment with the wellhead structure as it is seated in place under the downward pull of the towline.

it is apparent from the foregoing description that the apparatus of this invention achieves the objects as set forth heretofore and provides a means for forcibly pulling Well working tools and equipment downwardly from a floating platform on the surface of the Water into a submerged wellhead through the force imposed by a towline. The apparatus is constructed to permit towline tensions in the range of thousands of pounds to be used. Thus, a means has been provided to align the well working equipment with the submerged wellhead in a positive manner and with sufiicient force to overcome the effects of subsurface water currents which heretofore have. proved troublesome in offshore drilling operations.

It is apparent that other modifications than those described herein may be made to the apparatus of this inven-.

tion without departing from the inventive concept. Therefore, it is intended that the invention embrace all equivalents within the scope of the appended claims.

I claim:

l. The method of drilling a well in submerged earth comprising anchoring a floating drilling platform at the surface of a body of water overlying a submerged well site, supporting at the surface of the water a base assembly having pulley means mounted thereon, operatively mounting one end portion of a towline on said pulley means and detachably connecting the end of said one end portionto saidplatform, connecting the other end portion of said towline to a winch means on said platform, sub merging said base assembly to the surface of the earth underlying said body of Water in a position substantially vertically below said platform while paying out said other end portion of said towline from said winch means, securing said base assembly to the submerged earth by casing means projected vertically downwardly through said base assembly and affixed to said base assembly and said earth with said towline comprising the only connection between said platform and said base assembly, detaching the said end of said one end portion of said towline from said platform and connecting said one end of said towline to a towing head, connecting said towing head to a drill string having a drill bit attached thereto, operating said winch means to forcibly pull said drill string and drill bit vertically downwardly through the water to said base assembly and into axial alignment with said casing means While supporting the upper end of said drill string by said drilling platform, further lowering said drill string from said drilling platform to place said drill bit in contact with the submerged earth, and operating said drill string by operating means on said drilling platform to drill a well into said submerged earth.

2. The method of drilling a well in submerged earth comprising anchoring a drilling vessel at the surface of a body of water overlying a submerged well site, securing to the submerged earth a base assembly having pulley means mounted thereon with a first towline mounted over said pulley means, said first towline comprising a flexible connection between the submerged fixed base assembly and said drilling vessel which permits said drilling vessel to move on said surface of said body of water relative to the said base assembly while remaining connected to In the latter case, when the,

1 l 7 said base assembly, connecting one end of said first towline to'a winch means on said platform and the other end of said first towline to the lower end of a drill string with a drill bit attached thereto, using said first towline to pull said drill string and drill bit downwardly to the tact with the submerged earth, operating said drill string from said vessel to drill a well bore into said submerged earth, retracting said drill string and drill bit from said well bore and raising them together with the said other end of said first towline to said vessel, using said first towline to pull a string of casing downwardly from said vessel to said submerged well site and into alignment with said base assembly with sufiicient force to overcome lateral displacement effect of water currents, further lowering said string of casing from said vessel and into said well bore with the upper end of said string of easing projecting upwardly from said well bore and terminating at said base assembly, cementing said string of casing to said well bore, using said first towline to pull wellhead control apparatus having a pulley means mounted onthe top portion thereof with a second towline mounted thereon downwardly through the said body of water to the submerged well site and into alignment with said base assembly with sufficient force to overcome lateral displacement effects of water currents, connecting said wellhead control apparatus to the said upper end of said string of casing, connecting one end of said second towline to a winch means on said vessel and the other end of said second towline to equipment to be introduced into the submerged well, using said second towline to pull said equipment downwardly through said body of water to said wellhead control apparatus and into alignment line into engagement with said conically flared portion of 7 with said submerged well with sufficient force to overcome lateral displacement efiects ofwater currents, and further lowering said equipment through said wellhead control 7 apparatus and into said submerged well.

' means, a winch means, said winch means supported by said platform, one end portion of said towline connected to said winch means for pulling on said towline, a towing head, the other end portion of said towline connected to said'towing head, means for detachably connecting said towing head to equipment to be pulled downwardly through the water, means on said platform for'supporting said ment, means for 'moving said pulley means toward the longitudinal axis of said well bore to dispose the said other end portion of said towline in substantially axial relationship with the longitudinal axis of said well bore and for moving said pulley means away from the longitudinal axis of said well bore to displace the said other end of said towline from axial relationship withthe longitudinal axis of said wellbore, a centering means on said support means, and means on said towing head engaging said centering means on said support means and placing said equipment in coaxial alignment with said well bore when said towing head is pulled into engagement with said support.

4. Apparatus forpulling equipment downwardly from a surface platform to a well opening submerged under o ,a body of water-comprising a base member engaging the surface of the land under said body of water, a cylindrical element afrixed to and projecting vertically upwardly from said base member and terminating at its upper end fiO ' portion, an opening formed through the circumferential wall of said element, a pulley means mounted to move toward and away from said opening in said cylindrical element, a towline mounted over said pulley means with tap in a conically flared portion, an opening formed through V the circumferential wall of said cylindricalelement, a pulley means mounted on said cylindrical element and positioned to project through said opening to dispose at least a portion of the rim of saidpulley means within said cylindrical element, a towline mounted over said pulley means and having one end portion thereof disposed operatively within said cylindrical element, a power means on said platform for pulling on said towline and having the other end portion of said towline connected thereto, a towing head, said towing head being connected to the said one end portion of said towline and formed to engage said cylindrical element in concentric relationship, an axially disposed passage through said towing head, means on said towing head to detachably engage equipment extended through said passage to pull said equipment into concentric relationship with said cylindrical element when said towing head is pulled by said towsaid cylindrical element, and means on said platform to support said equipment as said equipment is being pulled downwardly from said platform. 7

5. Apparatus for pulling equipment downwardly from a surface platform me well opening submerged under a body of water comprising a base member engaging the surface of the land under said bodyof water, a hollow cylindrical element affixed to and projecting vertically through the circumferential wall of said cylindrical ele ment, a pulley means mounted on said cylindrical element,

to move toward and away from said opening to project said pulley means through said opening and withdraw it therefrom, a towline mounted over said pulley means and having one end portion thereof disposed operatively within said cylindrical element, a surface platform, means supported by said platform for releasably pulling on said towline and having the other end portion of said towline connected thereto, a towing head for-med to detachably engage said cylindrical element in concentric relationship, a bail pivotally mounted on the lower end of said towing head, means connecting the said one end portion of said towline to said bail to pull said towing head into engagement with said cylindrical element when said other end portion of said towline is pulled, and means to move said pulley means away from said opening to swing said bail and displace the said one end portion of said towline laterally of the longitudinal axis of said cylindrical element when said towing head is in engagement with said cylindrical element. t l

6. Apparatus for' pulling equipment downwardly from a surface platform to a well opening submerged under a body of water comprising abase member engaging the surface of the land under said body of water at a submerged well opening, said base member having an opening therethrough in vertical alignment with said submerged well opening, a hollow cylindrical element afiixed to and projecting vertically upwardly from said base member in alignment'with the submerged well opening and terminating at its submerged upper end in a conically flared one end portion thereof passing through the'interior of said cylindrical element, a towing head, the said one end releasablypulling on the other end portion ofsaid tow- 7 line and havingsaid other end' portion of said towline operatively connected thereto, means to move said'pulley I means toward and into said opening in said cylindrical element when a pull is placed on said towline to place the said oneend portion of said towline in substantially coaxial alignment with said cylindrical element, and means a 13 to move said pulley means out of and away from said opening in said cylindrical element when the pull is released from said towline.

7. A towline assembly for use on a submerged wellhead comprising a base member forming a portion of a submer ed wellhead apparatus and having an opening therethrough in alignment with a submerged well bore, a hollow cylindrical element secured to said base member and projecting upwardly therefrom in alignment with said opening, an opening in the circumferential wall of said cylindrical element, an arm pivotally mounted at one end on the exterior surface of said cylindrical element and positioned to swing toward and away from said opening in the circumferential wall of said cylindrical element, a pulley rotatably mounted on the other end of said arm and disposed to pass through said opening in the circumferential wall of said cylindrical element when said arm is swung about its pivot, a towline mounted over said pulley with a first end portion of said towline disposed within and passing axially through the interior of said cylindrical element and a second end portion thereof disposed exteriorly of said cylindrical element, a winch means, said second end portion of said towline connected to said winch means, a surface platform supporting said winch means, means to connect the said first end portion of said towline to submersible apparatus to be pulled downwardly through a body of water to said submerged wellhead apparatus, means on said platform for supporting said submersible apparatus, means to swing said pulley to a position within said cylindrical element to place said first end portion of said towline in substantially coaxial alignment with the longitudinal axis of said cylindrical element when tension is placed on said towline, means centering said submersible apparatus in axial alignment with said cylindrical element when said towline pulls said submersible apparatus into engagement therewith, and means to swing said pulley outwardly of said cylindrical element to displace said first end portion of said towline from coax al alignment with the longitudinal axis of said cylindrical element when said submersible apparatus is in engagement with said cylindrical element.

8. A towline assembly in accordance with claim 7 wherein said means to connect said towline to apparatus to be pulled downwardly through the water comprises a towing head detachably connected to said submersible apparatus, a pivot axis on said towing head, a bail pivotally mounted on said pivot axis, said towline connected to said bail, and means to rotate the pivot axis of said bail to a position transverse to the direction of the pull of said towline as said towing head is pulled into engagement with said cylindrical element.

9. A towline assembly in accordance with claim 8 wherein the said means to rotate the pivot axis of said bail comprises a cam secured within said cylindrical element, a cam follower at each end of said pivot axis, said cam positioned to engage said cam followers as said towing head is pulled into engagement with said cylindrical element.

10. A towline assembly in accordance with claim 7 wherein the said means to swing said pulley into and out of said opening in the wall of said cylindrical element comprises a power means connected to and between said cylindrical element and said arm to swing said arm about its pivot, and control means connecting said power means with said platform.

11. A towline assembly in accordance with claim 7 wherein the said means to swing said pulley to a position within said cylindrical element comprises said towline when placed under ension reacting with said pulley to produce a force on said arm to swing said arm toward the said opening in the circumferential wall of said cylindrical element, and wherein the said means to swing said pulley outwar ly of said cylindrical element is a retracting means connected between said arm and said cylindrical element which swings said arm away from the opening in the circumferential wall of said cylindrical element when the tension in said towline is released.

12. A towing head for pulling well apparatus downwardly through a body of water from a surface platform to a submerged well opening comprising a cylindrical member having an axially disposed cylindrical chamber therethrough, a radially enlarged upper exterior portion in said member, a buoyancy chamber within said enlarged portion of sufiicient buoyant capacity to make the towing head positively buoyant when said towing head is submerged, a radially reduced lower exterior portion on said member, a ring element rotatably mounted on said lower exterior portion of said member for rotation relative to said member in a plane transverse to the longitudinal axis of said member, means to connect a towline to said ring element, a top element detachably secured to said member, an opening through said top element in axial alignment with said cylindrical chamber, said top element having a flange portion extending radially inwardly of the inner walls of said cylindrical chamber to provide a shoulder adjacent the upper end of said cylindrical chamber.

13. A towing head for pulling well apparatus downwardly through a body of water from a surface vessel to a submerged well opening comprising a cylindrical member having an axially disposed cylindrical chamber therethrough, a radially enlarged upper exterior portion in said member, a radially reduced lower exterior portion on said member, a ring element rotatably mounted on said lower exterior portion of said member for rotation relative to said member in a plane transverse to the longitudinal axis of said member, a bail pivotally mounted on said ring element for swinging movement in a direction transverse to the longitudinal axis of said member, means to connect a towline to said bail, a top element detachably secured to said member, said top ele ment comprising a cylindrical sleeve fitting within said cylindrical chamber and afiixed at its upper end to a flange, an opening through said flange in axial alignment with said cylindrical sleeve, said flange extending radially inwardly of the inner walls of said sleeve to provide a shoulder at the upper end of said sleeve, and means to secure said flange to the top portion of said cylindrical member with said sleeve concentric with said cylindrical chamber.

14. A towing head in accordance with claim, 13 wherein said bail is mounted on a pivoted axis which is displaced laterally from a diameter of said ring element to produce an eccentric force on said ring when a towline connected to said bail is placed under tension in a direction laterally disposed relative to the longitudinal axis of said member.

15 A towing head in accordance with claim 13 wherein said bail is curved in a lateral direction from a plane passing between the pivot axis thereof and a central point of towline attachment on said bail to provide a camming surface on said bail in coaction with a relatively stationary element engaged thereby to rotate said ring about the longitudinal axis of said member.

16. The method of drilling a well in submerged earth comprising anchoring a floating drilling platform at the surface of a body of water overlying a submerged well site, supporting at the surface of the water a base assembly having pulley means mounted thereon, operatively mounting one end portion of a towline on said pulley means, connecting the end of said one end portion of said towline to a buoyant element detachably engaged with said base assembly, connecting the other end portion of said towline to a winch means on said platform, submerging said base assembly to the surface of the earth underlying said body of water in a position substantially vertically below said platform while paying out said other end portion of said towline from said winch means and while holding said towline under sufiicient tension to maintain the engagement between said buoyant element and said base assembly, securing said base assembly to the submerged earth by casing means projected vertically downwardly through said base assembly and afiixed to said base assembly and said submerged earth, releasing the tension in said towline to buoy the said end of the said one end portion of said towline to the surface of said water by said buoyant element, connecting said buoyant element to a drill string having a drill bit attached thereto, operating said winch means to forcibly I ,pull said drill string and drill bit vertically downwardly through the water to said base assembly and into axial alignment with said casing means while supporting the upper end of said drill string by said drilling platform, further lowering said drill string from said drilling platform to place said drill bit in contact with said submerged earth, and operating said drill string by operatsubmerged at the bottom of the water at said well site,

a casing means projecting vertically downwardly into the earth from said base assembly and afiixed to said base assembly and said earth, a pulley means mounted on said base assembly, a single towline mounted over said and connected to said towing head and with the other end portion thereof connected to said winch means, a

string of tubing supported in a vertical position by said platform, means connecting said towing head to 'said' string of tubing, said winch means being operable to pull said towing head and said string of V tubing downwardly through said water to said base assemblywith sufiicient tfOI'CE to overcome lateral displacement effects of Water currents on said towing head and said stringof tubing as they progress downwardly through said water, a first concentric centering means on said towing head and complementary second centering means on said a base assembly and concentric with said casing means, said pulley means and disposed with one end portion thereof in substantially axial alignment with said casing means first and said second centering meansbeing constructed to be pulled into axial alignment with each other to seat said towing head on said base assembly with said tubing in axial alignment with said casing means as said towline pulls said towing head into engagement with said base assembly.

References Cited in the file of this patent UNITED STATES PATENTS 955,812 Kuhlman Apr. 19, 1910 1,697,649 Hansen Jan. 1, 1929 1,734,223 Melott Nov. 5, 1929 2,808,229 Bauer'et al. Oct. 1, 1957 2,984,308.

1 Bauer et a1. May 16, 1961 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,047,078 July 31, 1962 William R. Postlewaite It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 11, line 56, for "ment," read equipment column 12, line 68, after "platformiflitirst occurrence, insert a comma Signed and sealed this 12th day of February, 1963.

ERNEST w. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

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