US3556210A

US3556210A - Deep sea well drilling structure

Info

Publication number: US3556210A
Application number: US823074A
Authority: US
Inventors: Vincent C Johnson
Original assignee: Individual
Current assignee: Individual
Priority date: 1969-05-08
Filing date: 1969-05-08
Publication date: 1971-01-19
Anticipated expiration: 1988-01-19

Abstract

An underwater well head encasement wherein a long tubular caisson rests on a base on the ocean floor and is provided with a housing at the top located 100 to 200 feet below the water surface. Hollow diagonal tubes brace the caisson in upright position. Drill guides extend from a chamber in the housing downwardly through the base to accommodate a number of well drilling operations. A closure for the casing is lifted off during the drilling and setting of casings. The closure is replaced after this and a diver can enter the chamber through a manhole and there work on the floor of the housing for installing and manipulating the well head equipment under conditions where the chamber may be either full of water or with the water evacuated.

Description

United States Patent Primary Examiner-Marvin A. Champion Assistant ExaminerRichard E. F avreau Attorney-Beehler and Arant ABSTRACT: An underwater well head encasement wherein a long tubular caisson rests on a base on the ocean floor and is provided with a housing at the top located 100 to 200 feet below the water surface. Hollow diagonal tubes brace the caisson in upright position. Drill guides extend from a chamber in the housing downwardly through the: base to accommodate a number of well drilling operations. A closure for the casing is lifted off during the drilling and setting of casings. The closure is replaced after this and a diver can enter the chamber through a manhole and there work on the floor of the housing for installing and manipulating the well head equipment under conditions where the chamber may be either full of water or with the water evacuated.

1, DEEP SEA WELL DRILLING STRUCTURE During recent years there has been an accelerated interest in the drilling of oil wells ojtfshore in the ocean waters. To a great extent operations heretofore have: largely been confined to water depths such as permit the placing of legs for stationary platforms on the ocean bottom so that the structure is in effeet a man-made island from whichdrilling operations are first conducted and thereafter from which the drilled wells are produced. II he success 'offsuch installations has lead to explorations further out in "deeper water where it is notfeasible nor economical 'to. place the legs of such platforms'on the ocean bottom..

An additional economical manner to avoid submarginal operations which would make the production of deep sea offshore wells impractical.

It is commonly recognized that although commercial divers can work at depths inexcess of 100 to 200 feet, when a diver goes down to'depths below this, the working shift for a diver is very short because of the fatigue involved working at such great pressures and a great amount of time is consumed lowering the diverto the necessary depth and then raising him again by successive decompressing stages tolthe surface.

It is therefore amongthe objects of theinve ntion to provide .a new andimpro ved underwater well head'encasement structure which makes it possible to successfully drill oil wells at ocean depths far exceeding the depths at" which commercial divers can effectively work, and subsequently produce such wells by bringing casings up to a higher level, where divers can worlt effectively but stillfar enough beneath the surface to be entirely clear of ocean navigation and the adverse effects of storms at sea.

' Another object of the inventionis to provide anew and improved underwater well head encasement structure of such character that it can be prefabricat'edto a large degree on or near shore and then towed to a location in deep sea water where it can be readily stationed and anchored in place for the drilling of oil wells. v 5

Still another'object'of the invention is to provide a new and improved underwater well head encasement structure of such character that it can be tinnly secured at a selected location by means such as the driving and setting of steel or concrete piles and avoiding employment of permanent anchors attached to the structure by guys and cables the structure and its placement being such that it can be accomplished in a relatively minimum amount of time and by use of currently available floating equipment, and thereby made ready for a multiple well drilling operation withappreciable economy.

Still another object of the invention is to provide anew and improved underwater well head encasement structure which is capable of establishing a chamberfor the accommodation of the tops of oil well casings ata level where they not only can 1 be installed and serviced conveniently by a diver but also of such characterthat production linescan be manifolded and difficulty in water of greater depth is the ina- V 'bility of divers with equipmentpresently available to readily cap wells after they have been drilled and attach the'requisite With these and other objects in view the invention consists in the construction, arrangement, and combination of the variv ous parts of the device, whereby the objects contemplated are attained, as hereinafter set forth, pointed out in the appended claims, and illustrated in the accompanying drawings.

In the drawings: FIG. 1 is a view picturing tion whereit will ultimately be placed in position.

FIG. 2 is a schematic view showing the initial operation of placing the deep sea welldrilling structure on the ocean bottom by employment of a floating worllt vessel.

FIG. 3 is a schematic view similar to FIG. 2 showing the structure after it has been anchored in position and in which a well drilling operation can take place.

FIG. 4 is a view similar to FIGS. 2 and 3 showing in operation. t

FIG. 5 is a fragmentary longitudinal sectional view of the upper end of the tubular caisson and-the housing at the top. I

FIG. 6 is a cross-sectional viewtalten on the line 6-6 of FIG.

device In the embodiment of the invention chosen for the purpose ofillustration the ocean bottom has been indicated by the reference character 10 and the water surface by the reference character 11. For purposes of illustration it may be assumed that the level of the bottom-is somewhere in the neighborhood of 600 feet or more below the surface ll, namely at a depth much deeper than a commercial diver with currently available equipment could readily operate. g

The structure consists of a central elongated tubular'caisson 12 having'a central bore 13 extending through it. At the lower end of the caisson is a base 14 which may, if desiredybe of steel or reinforced concrete, side portions'of which extend outwardly from the wall of the caisson 12 an appreciable distance to provide an acceptable degree of stability. When the base 14 is of concrete as suggested, the lower end 15 of the .of conventional construction are adapted to extend between the tubular columns and also the caisson. The tops ofthe tubular columns 16 may be attached more or less midway between upper andlower-ends of the caisson l2 and be directed outwardly at an angle of some 10 to 209' more or less from perpendicular to provide adequate diagonal bracing, taking into consideration the overall height of the caisson which may differ from time to time as the depth of the water varies. A number of anchoring projections 18 may be constructed as part of the base 14 or' secured to it having such length that they project downwardly into the ocean bottom 10 to ensure against horizontal shifting of the base and the bottom of the caisson.

At the upper end of the caisson 112 is a housing indicated generally by the reference character 20. The housing 20 may be of boiler plate or may on occasions be of reinforced concrete as generally shown and described in US. Pat. No. 3,247,672. In the chosen embodiment the housing has a body 21. which encloses a chamber 22, the body being annular with a smoothly curved exterior wall. Reinforced concrete material has been suggested in which are placed a structural steel frame and reinforcing rods 23. At the lower end of the housing 20 is a horizontal bottom 24, shown as constructed of the same material, the bottom extending over and substantially closing an upper end 25 of the caisson l2. Extending diagonally downwardly and inwardly from a perimetral edge 26 of the body 21 is a perimetral diagonal bracing structure 27 the upper end of which is attached to the edge 26 and the lower end of which is attached to the wall of the caisson l2.

Extending through thebottom 254 are drill guides 28 which number seven in the presentembodiment and which are northe towing of the device to a localength of the drill guides is such that they extend throughout the full height of the caisson l2 and protrude through the base 14 as shown in FIG. 5.

Around the upper end of the body is a perimetral rim 29 of shouldered construction forming an opening 30 which, when of circular construction, has a diameter at least as large as the diameter of the caisson 12 or preferably appreciably larger. Seated on the shoulder rim 29 is a closure 31 in the form of a spherical segment at the top of which is a manhole 32 closed by a removable manhole cover 33. The manhole is provided with a lifting ring 34 and similar lifting rings 35 are provided on-:.the closure 31, so that the closure can be removed and replaced as well as the manhole cover.

In placing the structure use is made of a floating work vessel 40,fprovide d as suggested with a crane 41 for manipulating a cable 42 at the lower end of which is a hook 43 engaging a sling 44 attached to appropriate lifting rings 45 on the body 21. The structure is lowered to the ocean bottom 10, whereupon the weight of the structure will tend to embed lower ends 46 of the tubular columns 16 into the ocean bottom while the base 14 rests on the ocean bottom. Once in this position, a drill (not shown) may be sent down through openings 47 and biased into the respective tubular columns 16, thereby to drill holes 48 into the ocean bottom through the lower ends 46 of the tubular columns. After the holes 48 have been drilled,

' concrete piles 49 can be set in them, thereby to firmly anchor the tubular columns 16 in place. After the structure has been effectively anchored in the position shown in H6. 3, the central drill guide 28 may be extended through the bottom 24 and into an appropriate bore 50 in the base 14. By use of a derrick 51 on the vessel and appropriate conventional well drilling equipment, the wells may be drilled by extending a drill rod through one or another of the drill guides 28 to drill appropriate wells 52 in the ocean bottom, after which well casiiig' lengths 53 are set in the well by extending them downwardly progressively from the vessel 40 into the wells 52. Upon completion of the setting of an appropriate number of casings 53, the drilling and casing setting operation is suspended and a diver 60 supported by a line 61 lowered from I the service vessel 40 so that he can enter the chamber 22 and attach the well head equipment suggested by the Christmas tree 63 and manifold piping 64. As further suggested in FIG. 4,

the manifold piping, namely production piping, is attached to a common accumulator casing 65, if all of the wells are to be produced through one common production line 66 through which all of the production may pass to an appropriate delivery point (not shown).

The closure 31, in company with the manhole cover 33, is then lowered into position over the body 21 so that there is a sealed joint between a lower supporting edge 67 of the closure 31 and the rim 29 at the top of the body 21. The seating of the manhole cover on the manhole may also be a sealed joint.

Thereafter, whenever it may be necessary to service the equipment at the top of the casing, located as it is in the chamber 22 above the floor 24, all that is necessary is to lift the manhole cover 33 from its position by engagement of suitable tackle in the lifting ring 34 thereby to provide access to the chamber 22 so that a diver can be lowered through the manhole to where he can walk about on the floor 24 for what- 'ever servicing may be required of him.

To insure against accidental contamination of ocean water by crude oil escaping from either a newly drilled well or a completed well under production, there is provided an overflow conduit 68 extending from the chamber 22 downwardly through the caisson 12 and then to a suitable disposal (not shown) on shore of capacity such thatit'can dispose of spillage from one or more of the'drilled wells'52. lclaim: w w a 1. An underwater well head encasement structure for mounting below the water surface and o'nthe ocean bottom by use of a floating work vessel comprisingm a tubular caisson having a lower endadjacent the ocean floor and having an upper end at a de th below the water surface within which a diver service by said vessel can operate; a base at the lower end of said tubular caisson; lateral supports for said tubular caisson comprising a plurality of diagonal braces having upper ends in engagement with the wall of the caisson intermediate upper and lower ends, lower ends of said braces being secured in the ocean bottom; i

a housing mounted on the upper end of the caisson including a side wall structure forming a chamber over said upper end, a bottom wall closing the lower side of said housing and extending over the upper end of said caisson, a plurality of drill guides extending from said bottom wall to said base, said wall structure having an upper perimetral rim forming an opening at least as large as the interior of said caisson to enable the drilling of wells through said drill guides and the setting of well casings in said wells; and g 1 a substantially annular closure for said housing having a supporting edge on the lower side in removable sealed position on said rim. V

2. An underwater well head encasement structure as in claim 1 wherein said diagonal braces comprise tubular columns having upper ends opening into the interior of the caisson and pilings extending from within the lower ends of respective columns downwardly into the ocean floor.

3. An underwater well head encasement structure as in claim 1 wherein said closure has a manhole on the upper side and a manhole cover in removable sealed position on said closure at a location covering said manhole.

4. An underwater well head encasement structure as in claim 1 wherein there are anchoring projections extending from said base downwardly into the ocean floor to prevent lateral shifting of said base.

5. An underwater well head encasement structure as in claim 1 wherein said base is at a location resting on the ocean floor.

6. An underwater well head encasement structure as in claim 3 wherein there are lifting attachments respectively on said annular closure and on said manhole cover to facilitate placing and removal of said annular closure and said manhole cover by operation from said floating work vessel.

7. An underwater well head encasement structure as in claim 1 wherein there is a perimetral diagonal bracing structure between the outside of said caisson and outer portions of said housing.

8. An underwater well head encasement structure as in claim 4 wherein said piling and said anchoring projections are of concrete poured in place.

Claims

1. An underwater well head encasement structure for mounting below the water surface and on the ocean bottom by use of a floating work vessel comprising: a tubular caisson having a lower end adjacent the ocean floor and having an upper end at a depth below the water surface within which a diver serviced by said vessel can operate; a base at the lower end of said tubular caisson; lateral supports for said tubular caisson comprising a plurality of diagonal braces having upper ends in engagement with the wall of the caisson intermediate upper and lower ends, lower ends of said braces being secured in the ocean bottom; a housing mounted on the upper end of the caisson including a side wall structure forming a chamber over said upper end, a bottom wall closing the lower side of said housing and extending over the upper end of said caisson, a plurality of drill guides extending from said bottom wall to said base, said wall structure having an upper perimetral rim forming an opening at least as large as the interior of said caisson to enable the drilling of wells through said drill guides and the setting of well casings in said wells; and a substantially annular closure for said housing having a supporting edge on the lower side in removable sealed position on said rim.