US3247672A - Underwater well head encasement structure - Google Patents

Description

April 26, 1966 v. c. JOHNSON 3,247,672

UNDERWATER WELL HEAD ENCASEMENT STRUCTURE Filed Aug. 29, 1962 2 Sheets-Sheet 2 WVCE/VT C. riomvsou I INVENTOR.

United States Patent 247,672 UNDERWATER WE LL HEAD ENCASEMENT STRUCTURE Vincent C. Johnson, 10377 Tennessee Ave, Los Angeles 64, Calif. Filed Aug. 29, 1962, Ser. No. 220,217 1 Claim. (Cl. 6146) This invention relates generally to underwater protective structures and relates more particularly to underwater well head encasement structures.

Various problems have been encountered in underwater oilwell drilling and oil well completion installations, particularly in areas of moderate to heavy navigation, primarily because of the extreme vulnerability of such installations to ships anchors and the possibility of deep draft collision in the shallow water areas. Damage resulting therefrom could lead to serious results, such as well blowouts, fire and pollution. Consequently such underwater oil well installations have been limited to relatively isolated areas.

Various methods have been used or proposed for underwater drilling and the production of oil fromsuch operations, including the ocean floor completion technique. The latter method presents serious difliculti'es. For example, the network of submarine lines and well head equipment greatly restricts the use of the area as an anchorage for ships. Such ocean floor well installations that presently exist and the previously known means for protecting these installations, include further disadvantages. Typically, complex well head attachments are made at ocean floor level and extend upwardly a minimum of approximately 12 feet. Any such installations are therefore restricted to a water depth of sufficient overhead clearance to allow for passing ships. Harbors, bays and near shore areas are generally not of sufficient water depth to safely permit oil well protrusions from the ocean floor.

Well head structures and the various means of encasement therefor now in existence merely extend the protrusion above the ocean floor and offer little or no safeguard from damage by ships anchors. Lateral forces also are often found prohibitive to the complete enclosure of the encasement being used, and one type known to be presently used is an open bird cage type encasement made of steel pipe materials. Obviously such an arrangement is vulnerable to ships anchors, even in isolated areas of comparatively deep water.

Further, such known types of protective structures are installed after the drilling and completing of the well which, of course, entails difliculties and problems, particularly in relatively deep water.

It is therefore an object of the present invention to provide protective means which will overcome the above difiiculties and solve the problems pointed out above.

Another object of the invention is to provide a structure of this character that is built in its enirety on land, with lifting lugs, etc., that may be required for installation built in the completed assembly.

Still another object of the invention is to provide a structure or apparatus of this character constructed to meet the requirements for a selected well location and exposures related thereto.

A further object of the invention is to provide structure of this character that is embedded in the ocean floor to such an extent that only a small portion is exposed above said floor, the portion exposed above the ocean floor being determined by the depth of the water in which the installation is made.

A still further object of the invention is to provide an encasement structure of this character which offers a deflective surface with no protrusions that might capture and/ or hold a dragging anchor or the like.

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It is another object of the invention to provide an encasement structure of this character having a contour that is least affected by lateral forces of wave and current.

Still another object of the invention is to provide a structure of this character that does not necessarily have to be water-tight and de-Watered, but whichvwill keep the interior free from foreign materials and provide a deterrent to marine growth.

A further object of this invention is to provide an encasement structure of this character which, in the event of leakage from the well head structure or structures, entrap the pollutant fluids and allow for early detection and corrective repairs.

Previous protective structures for underwater well heads have accommodated only a single well and it is another object of the present invention to provide an encasement structure which will accommodate a plurality of such well head structures.

A still further object of the invention .is to provide an encasement structure of this character that is sturdy, effective and reliable in protecting well head structures and the like from damage by ships anchors, other equipment and/ or factors. I It is another object of the invention to provide a structure of this character that is relatively easy to install.

It is still another object of the invention to provide an encasement structure of this character that is relatively inexpensive to manufacture.

The characteristics and advantages of the invention are further sufiiciently referred to in connectionwith the following detailed description of the accompanying drawings, which represent certain embodiments. After Con sidering these examples skilled persons will understand that many variations may be made without departing from the principles disclosed, and I contemplate the employment of any structures, arrangements, modes of operation or steps of the method that are properly within the scope of the appended claim.

Referring to the drawings, which are for illustrative purposes only:

FIG. 1 is a diagrammatic view of equipment installing an underwater well head encasement structure showing said structure being lowered into a hole previously excavated therefor;

FIG. 2 is a similar view showing the encasement structure resting on the bottom of the excavation or hole;

FIG. 3 is a view of the structure installed and marked by a buoy;

FIG. 4 is an enlarged vertical section through the encasement structure showing a well head structure therein; 4 F13. 5 is a sectional view taken on line 5-5 of FIG.

FIG. 6 is a fragmentary view of the structure showing an alternative arrangement.

The encasement structure is built in its entirety on land with lifting lugs and any other equipment that may be needed built into the structure which is constructed in accordance with the requirements of any specific installation.

Referring to FIG. 4, the structure is shown as being of precast concrete with steel reinforcements.

More particularly the encasement structure comprises a floor, indicated generally at 10, the lower dome, indicated generally at 11, the lid, indicated generally at 12, and the manhole cover, indicated generally at 14.

In constructing the encasement structure or cell, a ring of structural steel beams, indicated at 16, are assembled for the floor and a series of horizontal beams are also set in for the floor supports. A predetermined number of pipe sections or conductor guides 17 are set in a pattern within the steel framework of the floor.

known mobile oil drilling platforms.

or barge hull 35 with legs 36 adjacent the ends.

Steel reinforcing bars 18 are also installed within the structural steel framework and lifting lugs 19 are installed at this time.

Forms for concrete are set up in the usual well known manner with spacers to allow the concrete to completely cover the steel framework from inside to the exterior. The concerete is then filled in, the Gunite process being one means that maybe used for this purpose. Thereafter the exterior surface is troweled to obtain the exact contour desired.

After the concrete has cured in the floor or principal structure, a steel framework, including the bar 20, is assembled and fitted. Concreting the dome follows the same procedure as the procedure followed in building the floor or principal structure.

The access cover 12 may be similarly formed as well as the manhole cover 14.

The dome 11 has internal reinforcing ribs 21 which may be located along the steel reinforcing members 20. The upper end of the dome is notched at the top to provide a horizontal shoulder 23 and a vertical shoulder 24 for reception of the lower peripheral edge portion 25 of the access cover, said portion 25 being so formed as to seat on the shoulder 23 and to be held against lateral displacement by the shoulder 24.

Adjacent the upper end of the access cover there is an opening 26 which is surrounded by a peripheral or annular horizontal shoulder 27 from the outer edge of which there is an upstanding annular shoulder 28. The periphery of the manhole cover 14 is formed so as to extend into the opening 26 with a peripheral portion resting on the shoulder 27. The manhole cover 14 is held against lateral displacement by the shoulder 28.

The floor and dome 11 are secured together by any suitable means. For example, reinforcing rods or the like may be left extending upwardly at the periphery of the floor so as to be embedded in the lower portion of the dome when constructed on said floor.

Means for raising and lowering or otherwise handling the floor and dome assembly comprise the lifting lugs 19. Lifting lugs 30 or other suitable means are provided for handling the access cover and there is a member 31 for handling the manhole cover, member 31 being shown as an eye. The lifting lugs 30 and the lifting lugs 19 may also be formed as eyes.

The first step of the installation procedure is to select the well location and then excavate a hole to rough dimensions. Various equipment may be used for making the excavation, such as clams, draglines, and/or jetting equipment operated from any suitable well known surface equipment. One type of such equipment is the George F. Ferris Marine Platform, typical of well Such equipment is shown in FIGS. 1 and 2.

Referring to FIGS. 1 and 2, the equipment has a float There is also a derrick 37 which is movable longitudinally and laterally of the barge hull.

After selection of the well location the barge is towed to such location and properly positioned. The legs 36 are then jacked down so that the lower ends rest on the ocean or underwater floor 38, where a continued jacking raising of the hull 35 above the water barge'is towed beneath the platform 35 and cables 41 of bridge cranes 42 aboard the platform are attached to the lifting lugs 19 of the concrete cell. It is to be understood that these lugs 19 are of sufiicient number and so arranged that the encasement structure will be held by the cables 41 in an upright manner so that the structure will not tilt.

After the cell or structure is lifted free the work barge is towed away and the concrete cell is then lowered into the excavation, being held suspended in the exact position for final resting. While in this position fill material is placed and firmly compacted underneath the structure and then around the perimeter thereof. In final position the main opening of the cell will'be a suitable predetermined distance above the fioor of the ocean. It has been found that having the main opening of the cell at approximately two feet above the ocean floor is a satisfactory arrangement, said main opening being the opening at the top of the dome.

Any suitable well known equipment may be used for compacting the fill material, indicated at 45 and 46 underneath and around the cell respectively.

With the encasement structure thus positioned and secured the access cover islifted from the dome and set to one side. Any of the usual methods of ocean drilling may then be followed, using either a fixed platform of the type shown in FIGS. 1 and 2 or a floating platform.

It will be noted that the derrick 37 is moved toward one end of the barge hull or platform when the encasement structure is being installed in the opening or hole 40. When drilling operations are conducted the derrick is moved to a position directly over the encasement structure and in alignment with the usual vertical opening, not shown, in such barge or platform.

The conductor guides in the bottom or floor of the encasement structure are funnel shaped with the large end at the top and serve as guide means for various tools and equipment during the drilling operations. These conductor guides are arranged in a suitable pattern but are so arranged as to be in register with the main opening at the top of the dome so that drilling equipment may be arranged in axial alignment with the various guides 17.

When drilling operations are conducted from a fixed platform a conductor pipe or the drill stem extends from the platform down into the ocean floor, such conductor pipe being indicated at 48 in FIG. 2. Since the drilling operations may also be from a floating platform or vessel a sub-assembly is used at the underwater floor with exposed drill pipe extending from the vessel to the subassembly.

Alternatively, a floating vessel may be used and when used a sub-assembly is provided at the ocean floor with the exposed drill pipe extending from the vessel to the sub-assembly. This method of drilling is also well known and need not be described.

After the well has been completed it is provided with the usual well head attachments which are disposed within the encasement structure, such completions following the usual practice.

The manifold 52 is provided within the encasement structure and attached to the floor thereof by any suitable well known means. The manifold structure 52is used to gather the individual oil and gas lines, such as conduits 53, from each of the completed wells. There is an exit opening 54 in the wall of the dome adjacent the manifold 52 for the main lines for oil, gas and remote controls which are connected with the manifold or enter therein. These main lines are disposed in a trench excavated therefor from the cell or encasement structure to a shore station, the trench being deep enough so that these lines are buried to a depth sufficient for protection from ships anchors and the like.

After drilling and well completion operations are terminated, the access cover is placed back in position on the dome, as shown in FIGS. 1, 3 and 4, the manhole cover being in position on said access cover. Thereafter the well heads are kept free of silt, sand and other foreign material and will be protected from damage from anchors and the like. For example, anchors that may be dragging on the underwater floor would have nothing to engage and would merely pass over the smooth, rounded exposed portion of the encasement structure.

Consistent withother underwater well completion techniques, there is no particular purpose served in de-watering the encasement chamber. In other words, it is not necessary to maintain a dry chamber. However, with the small projection of the structure above the surface of the ocean floor, the chamber will be kept free of any foreign materials and will prove a deterrent to marine growth. It is to be noted that the access cover is joined to the dome and the manhole cover is joined to the access cover so as to provide a reasonably tight fit to keep such foreign materials out of the encasement structure and deter marine growth. If it is desired to provide a tighter fit between the parts, gaskets may be used.

Moreover, because of the tight connections between the access cover and the dome and the manhole cover and the access cover pollutant fluids resulting from leakage from the well head equipment in the structure will be entrapped and allow for early detection and corrective repairs.

Referring to FIG. 6, there is shown an arrangement wherein there is a depending annular flange 60 carried by the bottom or floor of the encasement structure. This arrangement is used in the event the encasement structure is supported by piles 61 where the underwater formation is too soft to permit the above described type of installation. The upper end of the piles 61 will extend into the area defined by the flange 60 and said flange will prevent the encasement structure from being displaced from the supporting piles 61, said bottom 10 resting on the upper ends of said piles.

In order to readily relocate any of the encasement structures a buoy 65 is attached to the eye 31 of the manhole cover by means of a rope or other suitable element 66.

While the present encasement structure has been shown and described as being of reinforced concrete, -it may be of steel or other suitable material.

The invention and its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement of the parts of the invention without departing from the spirit and scope thereof or sacrificing its material advantages, the arrangements hereinbefore described being merely for purposes of illustration.

I claim:

An underwater hollow oil well encasement structure, comprising:

' (A) a floor of concrete;

(B) annular structural steel elements embedded in the concrete, including an annular part adjacent the periphery of said floor;

(C) conductor guides set in a pattern in the floor, said 5 conductor guides extending through the floor and being funnel shape-d and having the larger diameter ends at the top;

(D) lifting lugs secured to the concrete floor at predetermined peripherally spaced positions;

of said lower dome section;

(F) an access cover comprising a terminated spherical segment open at both ends, the lower end of said access cover having an enlarged annular portion removably received in said recess at the upper end of the lower dome section whereby the access cover is held in position on the lower dome section;

(G) lifting lugs on the exterior of said access cover; (H) a shoulder about the opening in the upper end of 5 the access cover;

(I) a manhole cover for the opening at the upper end of the access cover, said manhole cover having its peripheral edge portion formed to the shape of said opening and engageable with said shoulder whereby said manhole cover is removably maintained in position in said opening;

(I) and means on said manhole cover, engageable by lifting means, for removal of said manhole cover.

References Cited by the Examiner UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

JACOB SHAPIRO, JACOB L. NACKEN'OFF, EARL I.

WITMER, Examiners.

(E) a dome comprising a lower terminated dome section secured to the concrete floor and having an access opening at the upper end, said lower dome section being of reinforced concrete with the larger diameter end attached to said floor, there being a groove about the access opening at the upper end

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