CA1042673A - Method of installing a subsea structure and recovering the structure from the sea floor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The installation and recovery of a structure or tem-plate which forms a tubular support structure for subsea equip-ment used in drilling and producing offshore oil and/or gas wells. The template contains production manifolding, remote and safety shut-in control, pump-separator, and pipeline connector subsystems. Certain of the structural tubes are segregated to form compartmented ballast chambers capable of being selectively flooded and dewatered. Certain other structural tubes form piling sleeves. The truss or framework of structural tubes include vertical and horizontal tubes, the latter forming circum-ferential members as well as interstitial supports. The upper-most of the circumferential members or "ring" also functions as a fender to protect the equipment within the template. The template is made negatively buoyant upon launch by flooding the compartmented ballast chambers, keelhauled (swung to a position underneath the keel of the drilling vessel), and then lowered to the subsea floor. Once it is positioned on the sea floor the subsea structure is oriented, pile founded and leveled. The template functions as a drilling and casing guide frame ensuring that drilled wells are connectable to the preinstalled manifold-ing. The template is recoverable by severing the piles and deballasting the compartmented ballast chambers.

Description

This application is a divisional application of application Serial No. 236,397, filed September 25, 1975.
The present invention concerns, broadly, maneuvering large and heavy equipments onto and from the sea floor. More particularly, th~ invention concerns a support structure for use in drilling and completing subsea oil and/or gas wells and methods for installing the structure on and removing the struc-ture from the sea floor.
In the past, most offshore drilling operations have been conducted from a fixed, bottom supported platform which rests on the sea floor and extends to the surface. However, as offshore oil development progresses to deeper waters, fixed platforms become prohibitively expensive to build. Generally, it becomes uneconomical to utilize fixed platforms as water depths approach 1000 feet. The present invention permits economic drilling operations to be conducted at water depths well in excess of 1000 feet by eliminating the need for a struc-ture which extends above the surface of the water. The present invention replaces the fixed platform with a completely sub-merged template which rests on the sea floor. The size of thetemplate is a small fraction of the size of conventional deep-water platforms and consequently, the template may be maneuvered into place on the sea floor by methods unlike the cumbersome installation procedures necessary to install a fixed platform.
As drilling and production water depths increase beyond the point of optimum diver utilization placing such structures on and removing such structures from the ocean floor must be conducted remotely from a floating vehicle. Motions induced by wind, wave and current create vessel-equipment interactions which, if not properly controlled, can render .' ~, _~ ~

~)42673 conventional handling techniques worthless. In addition, such structure placement and removal operations should include utilization of a minimum number of marine vessels, the ability to work under normal weather conditions, a relatively rapid completion of the operations to preclude extended waits for lengthy periods of good weather, and the ability to place the structure in the correct geographical location and attitude.
The structure should also be designed for easy installation, should be capable of withstanding the abnormal rigors of sea ; 10 floor existence, and should be retrievable at the conclusion of its working life. The structure and methods of the present invention meets all of the aforementioned requirements.

SUMMARY OF THE INVENTION
The present invention involves a subsea structure which comprises a plurality of horizontal and vertical struc-tural tubes arranged to provide support for the subsea oil and/or gas drilling and production equipment. Certain of the tubes are segregated to form compartmented ballast ,~ - 2a -1 chambers or tanks capable of belng selectively flooded

2 or dewatered to achleve deslred negatlve or posltlve

3 buoyancies, respectlvely, so that the weight of the sub-

4 merged structure can be controlled to facllitate carrying

5 out the varlous required operatlons. The elevated loca-

6 tlon of the uppermost clrcumferential rlng makes lt very

7 useful ln generatlng a large water plane area for yield-

8 lng excellent floating stabillty and provides, also, a

9 high center of buoyancy in the submerged condltlons which

10 also contrlbutes to stability. In addition, thls rlng

11 serves as a fender to protect the equlpment surrounded by

12 the rlng from damage by dragging anchors or other submer-J 13 ged ob~ects. Selected vertical structural tubes form plle 14 sleeves used ln securlng the structure to the sea floor.
15 Guide means are provided on the rlng to aid in guiding 16 equipment into the plle sleeves. Such equipment aids in 17 anchoring the subsea structure to the sea floor and for 18 releasing the subsea structure from the sea floor.
19 Orlentlng tubes are mounted on the periphery of the subsea 20 structure through which llnes are extendible to a surface 21 drllling vessel and to surface working vessels. The 22 drllllng and productlon equlpment on the subsea structure 23 lncludes a track for a manipulator which surrounds a 24 series of well bays, an antipollution pan, flowline 25 valves~ a framework for flowline connectors, electrical-26 hydraulic units, a separator and pump unit and a buoyancy 27 control manifold having flood and vent lines extending to 28 the ballast chambers.
29 The method involved in maneuvering the subsea 30 structure to install it on the sea floor comprises the 31 ~tep~ of towlng the structure to ad~acent a drilling 32 vessel; connectlng llnes between the vessel and the ~ 3 --- ~042673 1 structure and the structure and one or more working 2 ves~el~, ballastlng to trlm the structure level ~t the 3 surface;ballastlng the structure to a negatlve buoyancy;
4 keelhauling the structure to beneath the drilllng vessel;
lowering the structure to the sea floor; orienting the 6 structure geographlcally; pile founding the structure onto 7 the sea floor; cementing the plles in the sea floor and 8 then levellng the structure. The structure is removable 9 by ~everlng the piles and dewatering the structure to make lt posltively buoyant.

12 Flg. 1 is a schematic perspective view of the

13 subsea structure of the inventlon;

14 Fig. lA is a fragmentary view illustrating buo-yancy control means;
16 Flgs. 2, 3 &nd 4 are respectively plan, side 17 and front vlews of the subsea structure of Fig. l;
18 Figs. 5 to 11, inclusive, illustrate schemati-19 cally towlng the subsea structure into the launch area, launchlng the structure from the tow barge into the water, 21 connecting the structure to the drilling vessel and then 22 keelhauling the structure to a position for lowering it 23 to the sea floor;
24 Flg. 12 ls a schematic illustration of the lowerlng of the subsea structure to the sea floor;
26 Figs. 13 to 15 inclusive illustrate the pile 27 and means associated therewlth for placing the pile in 28 position and for cementing thereof;
29 Figs. 16 to 18 illustrate the pile sleeve and lifting tool for leveling the subsea structure;
31 Figs. 19 to 25 illustrate schematically the 32 steps employed in cementing the piling in the ground _ 4 -1 underlying the water and ln cementlng the plllng in the 2 plllng sleeve; and 3 Flgs. 26 to 33 lllustrate schematlcally the 4 steps employed in removlng the subsea structure from the ocean floor.
6 DESCRIPTION OF THE PREFER~ED EMBODIMENTS
7 As shown in Flgs. 1 and lA, a large boxlike 8 structure or template 10 designed for subsea use ln drlll-9 ing and produclng submerged oil and/or gas wells lncludes a truss or framework of interconnected vertical and hori-11 zontal qteel tubular members 11 and l2, respectively, 12 whlch are segregated to form compartmented tan~s which 13 function as ballast chambers, and other steel tubular mem-14 bers, which form pile sleeves 32 and cross support members 9 and 9a The large uppermost circumferential tubular 16 members 13 also form a protective ring or guard ~ender for 17 the equlpment supported on structure 10. That equlpment 18 includes production manlfoldlng 14 on whlch is mounted an 19 antlpollutlon pan 15 and which surrounds a number of well bays 16, a track 17 surrounding the productlon manlfoldlng 21 and having a stralght track section 18 on whlch ls posi-22 tioned an anchor 19 for a manlpulator and a releasable 23 buoy 20 for use in guiding the manlpulator to the track, 24 framework 21 for flowllne connectors, flowllne valves 22, a separator and pump unit 23, a buoyancy control manifold 26 24, flood (water) and vent (air) lines connected to buo-27 yancy control manifold 24 and the ballast chambers, 28 d eb a 1 la st t u b e ~1 0 m o u nt ed o n o ne o f 29 the corner B up p o rt tubes 9, and an electric-hydraulic unit 25. As shown particularly in F~gs 1 to 4 template 31 10 is rectangularly shaped and has a bow 26 and a stern 32 27. A space 28, is formed ln the bow side of tubular 1 ring 13 to accommodat~ ~ow~ine connector apparatus and 2 a space 29, is formed in the stern side of tubular ring 3 13 to accommodate a power cable which extends from the 4 surface to the separator and pump unit 23. Power for 5 control system purposes is delivered through a separate 6 umbilical cable 25a extending through space 28.
7 Two L-shaped orienting tubes 30, each having 8 funneled ends and each being located in opposite diagonal 9 corners of template 10, are used in orienting template 10 10 and orienting line 31 is threaded through each of the 11 orienting tubes 30 as shown.
12 Four of the vertical tubular members 32 form 13 pile sleeves. Adjacent each pile sleeve are two guide 14 post sleeves 33.
Vertical tubular members 34 at the extremities 16 of template 10 are flooded as necessary to level the tem-17 plate while it is floating at the surface to ensure that 18 it will submerge level. Preselected portions of the lower 19 horizontal tubular members 35 are flooded to change the 20 template from a positive to a negative buoyancy at which 21 buoyancy the wei~ht is maintained at a sufficiently low 22 value to permit handling of the template by conventional 23 apparatus. Thus, the template will remain at such nega-24 tive buoyancy during lowering operations, orienting, pile 25 setting, cementing and leveling. Divers operate the 26 valves on the buoyancy control manifold to control the 27 ballasting operations while the template is at or near 28 the water's surface prior to lowering it to the sea floor.
29 Tubular members not flooded prior to or during the keel-30 hauling and the change from positive to negative buoyancy, 31 including centrally located members 36 and buoyancy or 32 fender ring 13, are flooded after temp1ate 10 is on bottom, , ,' 1¢)42673 1 leveled and piles set. The manlpulator operates the 2 valves on the buoyancy control manlfold to control fill 3 and vent operatlons once the template is posltloned on 4 the sea floor Upon an acoustic command from the surface vessel, a buoy ls relea~ed from the template and the 6 manlpul~tor whlch ls positlvely buoyant upon launch hauls 7 it~elf down, lands, and latches on the track enclrcllng 8 the manl~old. Once latched on the track the manlpulator 9 ls ln a posltlon to remove malfunctlonlng parts of, ln-st~ll replacements parts of and resurface carrylng used 11 components of the pretested equlpment lnltially lnstalled 12 on the template.
J 13 As shown ln Figs. 2 and 3 more particularly a 14 slngle tllt angle beacon 37 used to measure the angular dlsplacement of template 10 durlng levellng ls positioned 16 ln an array wlth two locator beacons 38 whlch are used to 17 meaqure azimuth. Alternative similar arrays are shown 18 and may be deslrable as spares to forestall replacement 19 delays on deep-water systems. A backup hardware telemetry system 137, 138 is also shown.
21 Fig. 5 shows template 10 being towed on a barge 22 42 by a vessel 43 to the slte of launch. As seen in Flg.
23 6 template 10 is connected to a drilling vessel 44 by a 24 control line 45 and to a work boat, not shown, by another control line 46. As indicated, end tanks of barge 42 are 26 flooded to permit template 10 to sllde into the water.
27 In the position-shown in Fig. 7 the vertical trim tanks 28 34 are flooded, as necessary, to level template 10 at the 29 ~ter~s surface. As seen in Fig. 8 template 10 is warped 30 alongside drilling vessel 44. Pneumatic bumpers 47 are 31 po~tioned between template 10 and drilling vessel 44.
32 Keelhaul brldles l~3 and 49 are connected to the bow and 11~)42673 1 stern of the drilllng vessel and to the bow and stern of 2 the templ~te. The warplng lines are removed and the main 3 lowerlng sllng assembly 50 is attached to template 10.
4 ~he maln line 51 of sling assembly 50 ls keelhauled through the drllling well (moonpool) 52 of drllllng ves-6 sel 44 and connected to a preferably heave-compensated 7 hook 55 (as indlcated in Fig. 8) in the derrick. One 8 work boat 56 pulls template 10 away from drllllng vessel 9 44 a specified distance 53 to permlt template 10 to swlng under and clear vessel 44 as lt is submerged. A work boat 11 57 may be connected to template 10 by line 58 and lt may 12 proceed upstream to a current control anchor if local 13 current conditions demand such a`ddltional control.
14 Anchors are set in a line ~ultable for azlmuth positlon-ing of template 10 utilizing winches on drilling vessel 16 44. Figs. 10 and 11 show template 10 in position for 17 lowering relative to drilling vessel 44. The weight of 18 the template as it swings under drilling vessel 44 is 19 supported by lowering sling assembly 50. Template 10 is raised Qlightly by line 51 and sling assembly 50 and 21 keelhaul lines 48 and 49 are removed.
22 Fig. 12 shows the relationship between drllllng 23 vessel 44 and template 10 as it is lowered through the 24 water to the subsea floor 60. The lines from anchors 63 which are the aforementioned orlenting lines 31 are taken 26 from the work boats and passed through orienting tubes 30 27 bow and stern of the template and connected to winches on 28 the bow and stern on drilling vessel 44. A pendant line 29 61 connected to a buoy 62 at the sur~ace is connected to each anchor 63 as shown. ~ydrophones 64 located on the 31 underside of drill~ng vessel 44 in association wlth bea-32 cons 37 and 38 contlnuously monltor the azlmuth positions ~, , he temp:l~te 1~ l~wcr~ ~hr~u~h the wQter. A~m~th ~ ~ ading~ are made ~ust before ~ettlng the template on the 3 ocean floor. Tensloning on orienting lines 31 can rotate 4 template 10 to the desired orientation at which point tem-plate 10 can be set on the ocean floor.
6 When properly landed lowering sling assembly 50 7 may be removed from template 10 by hydraulic lines con-8 nected to pelican hooks (not shown) on the sling or by 9 mechanicRl release cables (not shown) operated from drill-ing vessel 4~. Control llnes 156 and 58, if used, are 11 removed by running go-devils down the lines to releasable 12 connection 157 for retrieval by the work boats. Orient-13 ing lines 31 are retrieved by picking up anchors 63 with 14 pendant llnes 61 and movlng towards template 10 while reeving ln llnes 31 with winches mounted on drllling ves-16 sel 44. As shackle 65 reaches drilllng vessel 44 the 17 upper segment of line 31 will be replaced with a synthetic 18 fiber rope 31a. The work boat will then proceed away from 19 template 10 drawing orlenting line 31 back down through orientlng tube 30. Line 31 will be tensioned with line 21 31a so as not to foul template 10. As line 31 clears the 22 template 10, llne 31a wlll be Jettlsoned wlth buoy 31b 23 attached to prevent llne 31a from fouling the template.
24 As buoy 31b implnges on orlenting tube 30, tensloning llne 31a will be stralned and parted. Llnes 31a and 31 26 will then be retrieved by work boat as will be buoy 31b.
27 The hea~lng for the drllling vessel mooring is 28 chosen to accommodate current and sea conditions at the 29 launch site. The drllllng vessel should be allgned with the surface cùrrent during keelhaullng. Selectlon of the 31 drilllng vessel~s heading ls made to permit turning the 32 vesgel in its moorlngs durine placement o~ the template 1~)42673 -1 to accommodate variables of current, wlnd, etc, Anticl-2 patlon of such varlables will establish whether the drill-3 lng ves~el is moored bow or stern to the current and the 4 relative position of the template, Referring to Figs. 13, 14 and 15 and wlth par-6 ticular reference to Fig, 13 there is shown the pile to 7 be inserted into and through plling sleeve 32 and the 8 means attached to the plle 70 for placing and cementing 9 plle 70 in place. Pillng 70 includes a cementing shoe ; 10 71, a lower retalner basket 72, an upper retainer basket 11 73, slips 74 and an upper funnel-shaped end 75, A spacer 12 plpe 76 ls connected into a collar 77 (see Flg, 14) to 13 whlch is connected a length of plastic plpe 78 which 14 extends down through plllng 72. Spacer pipe 76 has mount-ed on it a hang-off tool 79 to whlch ls attached drlll 16 plpe 80.
17 Referring now to Figs, 16 to 18 ln which the 18 lifting tool for levellng the template ls shown in oper~t-19 ing posltlon relatlve to the pile sleeve. Plling sleeve 32 has overflow slots 32a positioned ~ust below buoyancy 21 and fender ring 13, The top of pile sleeve 32 is provided 22 with two sets of J-slots 85 and a pile sleeve guide cone 23 86. The purpose of the overflow slots are to prevent 24 cement slurry from spilling over on production and other equipments 14-24 and from entering the upper end of the 26 plling sleeve ad~acent the J-slots, A lifting tool 87 27 havlng a sleeve portion 87a and tapered plate members 87b 28 thereon is attached to drill pipe 89, A pair of J-~ugs 29 87c positioned 180~ apart are flxed on and extend outward-ly from sleeve portion 87a, A strlnger or pipe 87d ex-31 tends downwardly from the lower end of tool 87. Plate 32 members 87b guide ~nd center the tool 87 into the cone-~6~4;~:673 1 shaped top 86 of plle sleeve 32 and allow the lugs 87c 2 to engage J-slots 85. Guide cables 90 extend to the 3 surface from guide posts 90a positioned in sleeves 33 and 4 guide frame members 91 posltioned about the cables 90 and connected to lifting tool 87 guide the lifting tool down 6 into pile sleeve 32, On larger templates only three level-7 ing pile sleeves may be used with several non-leveling 8 plle 61eeves.
9 The cementing and leveling operatlons are illus-trated ln Figs. 19 to 25 lncluslve. Referrlng to Flg. 19 11 operations are begun on the lowest sleeve as indicated by 12 tilt beacon 37. A drill string 100 including a drill bit 13 101, drlll collars 102 and drill pipe 103 is guided from 14 drllling vesse? 44 lnto plle sleeve 32 by means of the gulde means 91 and cables 90 and the plle hole 104 is 16 drilled to a desired depth, The hole is conditioned by 17 displaclng seawater with vlscous drllling fluid to pre 18 serve the hole. The drill string is then recovered to 19 the drill vessel. As illustrated in Figs. 20 and 21 the pile assembly shown ln Flg. 13 is run lnto the pile hole 21 through the plle sleeve on drill pipe untll hang-off tool 22 79 reaches pile cone 86. Sllps 74 engage the inner wall 23 of pile sleeve 32 and allows upward mo~ement of plling 24 sleeve 32 but prevents downward movement thereof. Spacer pipe (drlll plpe) 76 positions the top of the plle or 26 slips a distance D (approximately 10 feet) above the 27 bottom of pile sleeve 32. The spacer pipe 76 connects 28 into pile sleeve 32 by means of the adapter collar 77 29 (Flg. 14) which is threaded lnto plle 70 by left-hand threads. Plastlc pipe section 78 extends from the under-31 slde of the adapter collar 77. The upper and lower re-32 tainer baskets 73 and 72, re~pectively, prevent prlmary .

~42673 1 cement from entering the pile sleeve annulus and the 2 secondary cement from golng below retainer basket 73.
3 Plastlc plpe 78 permits the primary cement slurry to re-4 main free of seawater as lt ls pumped down the drill plpe and through the plastic plpe. In the event the plastic 6 plpe becomes cemented in it can be twisted off when the 7 adapter and drill pipe are removed and left in piling 70.
8 A logging tool 105 (or detector) is run through the drill 9 plpe and through the piling assembly to detect cement as lt passes uphole ln the piling annulus 106. The cement 11 slurry is mixed with radioactive material ln the first 12 batch thereof sufficient to provide a reading on the de-13 tector when the cement passes the detector and also when 14 it moves up in the annulus 106. Thls assures that the slurry is not being lost to formations. Cement ls then 16 pumped down the drill pipe and through the piling and the 17 cement shoe as illustrated in Figs. 24 and 25 until the 18 cement ls ~ust below the top of hole 104 as indicated by 19 raising logging tool 105. The cement is then permltted to set and the drill pipe and adapter plus the plastic 21 pipe, if not cemented in, are removed from the hole. If 22 the plastic pipe is cemented in then it ls twlsted off 23 and left in the pile.
24 As lllustrated ln Figs. 22 and 23 lifting tool 87 is run on drill pipe with a stinger and stabbed into 26 pile sleeve 32 to engage lugs 87c into J-slots 85. The 27 drill pipe is then pulled up to raise the lowest corner of 28 template 10 while taking readings indicated by tilt beacon 29 37. A~ter each upward mo~ement of khe template the tilt beacon i~ allowed to steady and is again read. The tem-31 plate pile sleeve ls raised until template 10 is as near 32 level as can be achieved with the first or lowest sleeve 1~)4Z673 1 32. AB shown in Fig. 23 the first sleeve 32 has been 2 ralsed a distance D'. Llfting tool 87 and drill pipe 89 3 are then removed. The pipe slips 74 will support the tem-4 plate 10 in this position. The same operations are then performed on the next lowest pile sleeve 32 as indicated 6 by the tilt beacon readlngs. The procedure for leveling 7 i9 repeated for each remainlng plle sleeve until the tem-8 plate is level.
9 Figs. 24 and 25 illustrate the secondary cement-ing procedure. Secondary cementing is begun in the last 11 plle used to level template 10. Cement is pumped through 12 the drill pipe connected to the lifting tool through the 13 lifting tool and into the top of piling 70 from which the 14 secondary cement overflows and fills the upper end of plle sleeve 32 until the cement flows out slots 32a in 16 the plle below the fender ring 13. Cement also surrounds 17 slips 74 and the upper portion of pillng 70 down to the 18 top of retalner basket 73. The cement is permitted to 19 equalize and then the J-tool and pipe are raised up and flushed with seawater. Then aballer is run through the 21 drill plpe to detect and sample the top of the cement.
22 The secondary cementing operatlons are repeated on each 23 of the remaining pile sleeves. The secondary cement acts 24 as a plug in the top of the pile sleeve and above the p1le and also acts as a backup for slips 74. The secondary 26 cement permits recovery of the upper portion of the piles 27 70 and 51ip units 74 when the template is salvaged after 28 its use in that particular locatlon has terminated. In 29 addltlon, the secondary cement prevents the template from moving off piles 70 during deballasting operations when 31 cutting or severing the piles as hereinafter described.

.

1~4Z673 1 After all of the piles have been set and 2 cemented in, tubular structure members thus far remain-3 lng dry on the template can be flodded to bring the tem-4 plate to full submerged welght. Drilling o~ the wells 5 through the well bays in the template i9 commenced and 6 completion and productlon operations are carried out.
7 The remaining Figs. concern salvaging the tem-8 plate. The wells are plugged and the well casings are 9 cut loose from the submerged productlon system equipment 10 on template 10. Referring to Fig. 26 then the secondary 11 cement is drilled out of pile sleeve 18 to ad~acent the 12 top of pile 70 ln the plle sleeve which is nearest to the 13 deballRsting tube 110 (see Fig. 29) which connects to the 14 ballast manifold 24. The pile is then drilled out to 10

15 feet below the cutoff point of the pile as illustrated in

16 Fig. 27. The drill pipe is then pulled and a cutting tool

17 assembly 112 on which is mounted a marine swivel 113 for

18 seatlng in pile cone 75 i8 run into pile 70 and the pile

19 is cut off as indicated at 114. The drlll pipe 103 and

20 cutting tool 112 attached to it are then pulled.
r 21 Before proceeding to cut a second pile debal-22 lasting operations are begun. Referring to Fig. 29 a 23 compressed air adapter stab unit 115 is connected to the 24 lower end of a drill pipe 116 (which contains a ~ar 117 25 ~ust above adapter 115) on the drilling vessel. The air 26 hose 118 to the work boat is keelhauled from the compres-27 sor on the work boat under the drilling vessel through the 28 moon well and attached to the adapter unit then the ada-29 pter 115 and drill pipe 116 are lowered together with 30 guide frame 119 and the adapter is stabbed and locked 31 into the deballast tube 110. Air is then pumped through 32 tube 110 to the bu-,yancy control mani~old 24 and then to ,', , ~4;~673 1 the ballast tanks formed by the tubular members to force 2 water out of the.n, A release sub 120 contalns a shear 3 pln, That shear pln ls sheared by ~ar 117 to release the l~ drill plpe connectlon from the adapter 115 and the drill pipe 116 i8 removed, As seen in Fig. 30 the air continues 6 to deballast the ballasting tanks, 7 Then the diagonally positioned pile sleeve 32 8 and the pile thereln are drilled out as dis~ ssed above 9 and the plle ls cut and removed ln the same manner as dis-cussed above, 11 The remalnlng two plles are preferably cut ex-12 plosively. Referring to Figs, 31 and 32 after drilllng J 13 out the cement as descrlbed above a telescoping tool or 14 locater sleeve 120 provlded wlth at lts upper end a land-ing head 121 and having a shear pin connection 122 to the 16 lower end of lifting tool 87 to whlch ls connected a re-17 lease sub 123 on drill pipe 124 is run into pile 70 until 18 landing head 121 lands on the pile cone 75 as shown. An 19 electrical cable 125 extends from the wbrk boat lnto the locater sleeve 120 and a cable 126 connects the lifting

21 tool to the work boat, A sub 127 on the locater sleeve

22 120 is provided with outlet ports 128, Locater sleeve

23 120 con$ains an explosive compounds such as a plastic

24 explosive compound, The locater sleeve 120 positlons the outlet ports at the deslred cutoff point in pile 70, 26 After head 121 lands in cone 75 pin 122 is sheared and 27 lifting tool 87 is lowered until lugs 86c on the lifting 28 tool are locked in the J-slots of the pile sleeve. This 29 downward movement forces the explosive compound through the ports into dlrect contact wlth the inner wall of pile 31 sleeve 32. Such telescopic movement also arms the unit 32 for firlne, The e~plosive compound is moved through _ 15 -.

16)4Z673 1 outlet ports 128 as indicated in Fig. 32. Thereafter the 2 drill pipe 124 is released from sub 1~3 above lifting tool 3 87. A slmilar operatlon ls performed in the diagonally 4 positioned pile sleeve, i.e. the pile sleeve is cleaned out and another locater sleeve containing explosive is 6 run into that pile. Both the electric cable and the other 7 cable 126 are connected at the surface to a second work 8 boat.
9 Deballastlng operatlons are halted. The drill-ing vessel ls removed from the area. The deballasting is 11 brought to a desired state. The charges are fired remote-12 ly from the work boats at short intervals. The released 13 template is controlled by control lines and the work boats.
14 As shown in ~ig. 33 the template rises to the water sur-face. When template 10 is afloat all the valves are 16 manually closed by divers and the template is towed to 17 port.
18 Changes and modifications may be made in the 19 ~pecific illustratlve embodiments of the invention shown and/or described herein without departing from the scope 21 of the inventlon as deflned in the appended claims. Thus, 22 as mentloned previously, instead of four piles two or 23 three piles or more than four piles may be used. In 24 additlon,the manner of ballasting and deballasting the manlfold may vary according to desired operations.
26 Further the manner of salvaging the template may be 27 changed. All of the piles may be explosively cut or all 28 may be mechanically cut.
29 Having fully described the method, apparatus, ob~ects and advantages of our invention we claim:

_ 16 -

Claims (12)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for maneuvering a subsea structure having intercon-nected vertical and horizontal structural tubes which form a box-like frame-work support for subsea hydrocarbon drilling and production equipment com-prising the steps of:
arranging said structure to float in water adjacent a drill-ing vessel;
ballasting said structure to trim said structure level at the water surface;
ballasting said structure to a negative buoyancy;
keelhauling said structure to beneath said drilling vessel;
lowering said structure to the sea floor; and orienting said structure geographically.

2. A method as recited in claim 1 including pile founding said structure onto the sea floor; and cementing said piles in the sea floor,

3. A method as recited in claim 2 including leveling said structure.

4. A method as recited in claim 3 including:
severing said piles;
deballasting said structure; and floating said structure to the water surface.

5. A method for maneuvering a subsea structure having inter-connected vertical and horizontal structural tubes which form a box-like framework support for subsea hydrocarbon drilling and production equipment comprising the steps of:
arranging said structure to float in water adjacent a drill-ing vessel;
connecting lines between said vessel and said structure;
keelhauling said structure to beneath said vessel;
ballasting said structure to level it in the water;
lowering said structure to the sea floor;

geographically orienting said structure prior to placement of it on the sea floor;
sinking piles through said structure to anchor it to the sea floor;
cementing said piles in place;
leveling said structure; said structure including cylindrical pile sleeves located at peripheral points on said structure through which said piles are sunk; the steps of cem-enting said piles in place and leveling said structure including:
lowering a drill string containing a drill bit through the lowest one of said pile sleeves and drilling a pile hole to a desired depth;
removing said drill string and drill bit to said vessel;
lowering a first pipe containing slips into said pile hole through said pile sleeve and engaging said slips with the inner wall of said pile sleeve to permit upward movement of said pile sleeve but not downward movement thereof relative to said first pipe;
pumping cement down said first pipe and up the annulus of said pile hole surrounding said first pipe until said cement is just below the bottom of said pile sleeve;
removing the upper portion of said first pipe above said slips to said vessel;
lowering a second pipe containing a lifting tool into said pile sleeve and engaging the lifting tool with said pile sleeve;
pulling up on said second pipe to raise said pile sleeve and thereby said structure until said structure is as near level as can be achieved;
removing said lifting tool and said second pipe;

repeating the above cementing and leveling opera-tions on each of said other pile sleeves until said structure is level; and pumping cement through the second pipe into the top of each of said pile sleeves until cement fills said pile sleeves.

6. A method as recited in claim 5 including:
conditioning said pile hole by displacing sea-water with viscous drilling fluid to preserve said pile hole prior to the step of removing said drill string and drill bit to said vessel; and running a logging tool through said first pipe to detect cement as it moves uphole in the first pipe-pile hole annulus, said cement containing radioactive material suffi-cient to provide a reading on a radioactive detector logging tool.

7. A method as recited in claim 5 including the steps of:
drilling out cement in each of said pile sleeves;
cutting off each of said pile sleeves;
deballasting said structure; and floating said structure to the water surface.

8. A method as recited in claim 7-in which said structure is rectangular and said pile sleeves are positioned at each corner of said rectangle and including the steps of:
drilling out cement in two of the diagonally positioned pile sleeves and then cutting off those pile sleeves;
initiating deballasting of said structure;
drilling out cement in the remaining two pile sleeves;
locating explosive compounds at the point of severance of said other two pile sleeves and then explosively severing said other two pile sleeves; and floating said structure to the water's surface.

9. A method as recited in claim 3 in which said structure includes cylindrical pile sleeves located at peripher-al points on said structure through which said piles are sunk and the steps of cementing said piles in place and leveling said structure include:
lowering a drill string containing a drill bit through the lowest one of said pile sleeves and drilling a pile hole to a desired depth;
removing said drill string and drill bit to said vessel;
lowering a first pipe containing slips into said pile hole through said pile sleeve and engaging said slips with the inner wall of said pile sleeve to permit upward movement of said pile sleeve but not downward movement thereof relative to said first pipe;
pumping cement down said first pipe and up the annulus of said pile hole surrounding said first pipe until said cement is just below the bottom of said pile sleeve;
removing the upper portion of said first pipe above said slips to said vessel;
lowering a second pipe containing a lifting tool into said pile sleeve and engaging the lifting tool with said pile sleeve;
pulling up on said second pipe to raise said pile sleeve and thereby said structure until said structure is as near level as can be achieved;
removing said lifting tool and said second pipe;
repeating the above cementing and leveling operations on each of said other pile sleeves until said struc-ture is level; and pumping cement through the second pipe into the top of each of said pile sleeves until cement fills said pile sleeves.

10. A method as recited in claim 9 including:
conditioning said pile hole by displacing seawater with viscous drilling fluid to preserve said pile hole prior to the step of removing said drill string and drill bit to said vessel; and running a logging tool through said first pipe to detect cement as it moves uphole in the first pipe-pile hole annulus, said cement containing radioactive material sufficient to provide a reading on a radioactive detector logging tool.

11. A method as recited in claim g including the steps of:
drilling out cement in each of said pile sleeves;
cutting off each of said pile sleeves;
deballasting said structure; and floating said structure to the water surface.

12. A method as recited in claim 9 in which said structure is rectangular and said pile sleeves are positioned at each corner of said rectangle and including the steps of:
drilling out cement in two of the diagonally posi-tioned pile sleeves and then cutting off those pile sleeves;
initiating deballasting of said structure;
drilling out cement in the remaining two pile sleeves;
locating explosive compounds at the point of severance of said other two pile sleeves and then explosively severing said other two pile sleeves; and floating said structure to the water's surface.