US3411473A - Deepwater anchor - Google Patents

Description

Nov. 19, 1968 -r T 3,411,473

DEEP WATER ANCHOR Filed Dec. 19, 1966 2 Sheets-Sheet 1 Nov. 19, 1968 Filed Dec. 19, 1966 DEEP WATER ANCHOR 2 Sheets-Sheet 2 United States Patent 3,411,473 DEEPWATER ANCHOR George E. Mott, Metairie, and John T. Loggins, New Orleans, La., assignors to Texaco lnc., New York, N.Y., a corporation of Delaware Filed Dec. 19, 1966, Ser. No. 602,706 6 Claims. (Cl. 114206) ABSTRACT OF THE DISCLOSURE The apparatus consists of an anchor for use in deep water which comprises a tubular member having an open lower end and a closed upper end. A concrete-weight cap is bonded to the top of the tubular member. Means are provided for evacuating and pressurizing the inside of the tubular member so as to aid in inserting and removing the anchor from a relatively soft, penetrable ocean bottom respectively. A pad eye is located at the top of the concrete-weight cap and another is located along the longitudinal length of the tubular member for connecting mooring chains or cables thereto.

This invention relates to an anchor for use in deep water and more particularly, to an anchor which is capable of resisting both horizontal and vertical loads without corresponding movement, and which may be inserted in the relatively soft ocean bottom utilizing a simple work vessel rather than a pile driving or drilling barge.

The anchoring of supply vessels, crew boats, etc., drilling vessels and floating drilling platforms for drilling offshore wells can be readily seen to be critical in that lateral movement of the vessel to any substantial extent cannot be tolerated. In the situations requiring minimal lateral displacement of the floating structure, the well known fluke type anchors are generally designed for specific bottom conditions, i.e. sand or soft clays. Anchors designed for one set of soil condition are not eflicient in different soil 1 conditions. Accordingly, it has been the general practice in industry to use steel piles driven into the bottom in cases when anchor slippage could be expensive and/ or disastrous. Anchor piles have been proven efficient in widely ranging soil conditions. In the fluke type anchoring systern, cable or chain lengths are usually to times the water depth depending on the magnitude of the mooring loads and the weight of the chain or cable. Such lengths are required to keep vertical force components from being transferred to the fluke type anchor; for, the holding power of such anchors is radically reduced with application of vertical loads. The cost of a mooring system utilizing fluke type anchors becomes extremely high in deep water applications.

Shorter chains and cables can be utilized in a mooring system, if anchor piles are driven into the ocean bottom. Such anchor piles can take some vertical loads. However, the cost of driving pilings into the ocean bottom in deep \water is extremely expensive.

The present invention provides an underwater anchor of the pile type which is capable of maintaining its imbedded position' in the ocean bottom when subject to strong lateral and/ or vertical pull. The invention also provides a method of installing the apparatus of the invention without having to utilize a conventional derrick barge or pile driving vessel, etc.

It is an object of the present invention to provide a deep water anchor capable of maintaining its imbedded position within the ocean bottom under heavy lateral or vertical pulls.

It is another object of the present invention to provide a deep water anchor of the pile type which can be easily inserted into the ocean bottom while using only a simple working vessel.

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It is a further object of the present invention to provide an anchor which is easily insertable in very deep water locations.

It is another object of the present invention to provide a deep water anchor which can be wholly salvaged.

It is another object of the present invention to provide a less expensive mooring system than the fluke type or driven anchor pile type which are presently in general use.

According to the invention, there is provided a deep water anchor comprising a vertically positioned upright tubular member having an open lower end defined by a relatively thin penetrating edge adapted for sinking into the ocean bottom. The top of the tubular member is closed by a convex dish-shaped member to which is bonded a weight-cap. A pad eye forming a first connection means is provided extending from the top of the weight cap so that vertical forces can be applied thereto or the anchor can be suspended vertically thereby. A suction-fill pipe is provided extending from the outside into the interior of the tubular member. A suction-discharge line extends from the suction-fill pipe to the water surface. A quick opening connector is located at the outer end of said suction fill pipe by means of which the suction discharge line can be remotely disconnected from the suction-fill pipe. A pump means is located at the surface and is attached to the suction-discharge line for evacuating or pressurizing the tubular member. A second pad eye or connection means is provided connected to the tubular member part way down the length thereof and extending therefrom for connection to a mooring line so that the lateral forces exerted on the mooring line by a surface vessel can better be withstood without displacement of the anchor.

According to the invention, there is also provided a method of inserting and removing a salvageableanchor which includes a tubular member having an open lower end for insertion in the ocean bottom at deep water location. The tubular member has a closed upper end and is capable of withstanding both vertical and horizontal pulls when located in the ocean bottom. The anchor is lowered in a vertical position from the water surface so that the open end of the tubular member of the anchor contacts the ocean bottom for insertion therein. When it is desired to insert the anchor, the interior of the tubular member is evacuated so as to create a downwardly directed pressure differential across the top thereof to sink said tubular member into the ocean bottom by utilizing the weight of the water above. When it is desired to remove the anchor, an upward pulling force is applied to the anchor from the water surface location, and in addition the interior of the tubular member is pressurized by pressure means to obtain an upwardly directed pressure differential, opposite to the previously obtained pressure .differential, concurrent with the pulling thereof to remove the anchor from the ocean bottom.

The above mentioned and other features and objectives of this invention and the manner of obtaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a schematic representation showing the anchor in place in the ocean bottom after having been lowered from a working vessel.

FIGURE 2 is a partial vertical cross sectional view of the anchor of FIG. 1.

Referring to FIG. 1, there is shown a work boat 12 anchored in position inthe body of water 14 over the location where the anchor 16 is to be inserted in the penetrable ocean bottom 18. The actual anchor structure 16 may be assembled at some on-shore location and brought to the mooring site. The vessel to be moored may be a drilling vessel or drilling barge which necessarily has to be maintained at a predetermined floating position within very close tolerances, for example, when drilling a well. Accordingly, a number of such anchors 16 would be located around the vessel or structure to provide the mooring of the required tolerance.

The anchor structure 16 consists of an uprightly positioned elongated tubular member 20 made preferably of steel or concrete which has an open lower end 21 defined by a relatively thin peripheral lip, usually having a thickness at the least the thickness of the metallic tubular member wall for easy insertion into the ocean bottom 18. Referring now to FIG. 2, the top of the tubular member 20 is closed by a plate, preferably a convex member 22 which is essentially dish-shaped and which correspondingly is preferably made of steel or concrete. If steel is used for the tubular member 20 and convex member 22, the dishshaped closure member 22 would be welded or joined to the upper edge of elongated tubular member 20 in a fluid tight, presure resisting seal and then imbedded in a weighted piece such as a concrete cap 24 to add additional weight to the tubular member 20. The concrete-weight cap 24 is bonded to the dish-shaped closure member 22. Short metal bars 26 are connected to and extend from the dishshaped closure member 22 into the concrete to improve the bond therebetween. The concrete-weight cap 24 need not assume a specific configuration, but as herein shown is hemispherical in shape with the curved portion facing upwardly toward the ocean surface when the anchor 16 is in place in the ocean bottom 18. The diameter of this hemispherical concrete-weight cap 24 is preferably greater than the diameter of the tubular member 20, having at least a portion thereof overhanging the latter and extend ing out therefrom to serve as a seat 28 on the mud line 30 when the anchor 16 is in place. Also, the upwardly facing spherical configuration of the concrete-weight cap 24 provides a strong structural shape to better withstand the extreme pressures applied thereto at deep water locations. It will be appreciated that the added weight of the concrete-weight cap 24 at the top of the tubular member 20 causes the lower thin edge end of the tubular mem- 20 when in contact with the penetrable ocean bottom 13 to sink therein to some degree thus forming a seal which is necessary for the subsequent evacuation step of the evacuable chamber defined by the member 20, closure member 22, and the ocean floor. A pad eye 32 is attached to and extends into the concrete-weight cap 24 to the dish-shaped closure member 22 where it is attached thereto by welding or some other suitable means. The pad eye 32 extends from the middle of the outer surface of the upwardly curved concrete weight cap 24 such that the entire anchor 16 can be hung from a chain or cable 34 attached thereto in a vertical position, that is, with the tubular member 20 vertical. Also, imbedded in the concrete-weight cap 24 and passing through the dish-shaped closure member 22 is a suction'fill pipe 36 which communicates the interior of the tubular member 20 with the exterior thereof. The suction-fill pipe 36 has connected at the top thereof a quick opening connector 38 to which is connected a suction-discharge line 40 which extends to the ocean surface and is connected to a pump 42 on the working vessel 12. The pump 42 removes the water from the inside of the tubular member 20 and creates a vacuum therein, thus producing a pressure differential across the concrete-weight cap 24 and thereby utilizing the weight of the water above the concrete-weight cap 24 to help in driving the tubular member 20 of the anchor 16 into the ocean bottom 18. It will be appreciated that the pump 42 can be reversed and thus water or other fluid can be pumped into the tubular member 20, thus pressurizing the interior to provide an opposite pressure differential across the concrete-weight cap 24 than was provided for inserting the anchor 16 to accordingly provide an uplift tending to remove the anchor 16 from the ocean bottom location. The evacuation or pressurizing of the interior of the tubular member 20 by pumping a fluid such as water out or in provides a hydraulic advantage wherein the vertical force operating on the tubular member 20 is proportional to the ratio of the areas of the tubular member 20 and the suction-fill pipe 36. Of course, the walls of the tubular member 20 and the concrete-weight cap 24- and suction-fill pipe 36 are designed to withstand the pressures necessary to insert or remove the tubular member 20 of the anchor 16 from the deep water location. The type of matter forming the ocean bottom 18, and, more particularly, the retaining force that has to be overcome to remove the anchor 16 from the ocean bottom 18 obviously have to be taken into consideration in designing the anchor 16.

An actuating line 43 is connected to the quick opening connector 38 at the top of the suction-fill pipe 36 and extends to the working vessel 12 at the ocean surface. This actuating line 43 when tightened can be utilized to operate the quick opening connector 38 and thereby disconnect the suction-discharge line 40. Referring now to FIG. 1, once the anchor 16 is imbedded in place in the ocean bottom 18 the suction-discharge line 40 is disconnected from the cable or chain 34 from the pad eye 32 in the middle of the cement-weight cap 24 can be attached to a float similar to 48 to mark the pile for possible later removal. The work boat 12 is then moved to a further location possibly to insert another anchor 16. After the anchor 16 is no longer needed it can be fully salvaged by again connecting the suction-discharge line 40. In the present arrangement this has to be done by a diver or other underwater means. If however removal of the anchor is contemplated, the suction-discharge line 40 and quick disconnect actuating line 43 may be secured at proper intervals to cable or chain 34 used to install the anchor and left in place for subsequent use in removing the anchor without the use of divers.

The tubular member 20 of the anchor 16 has located in the outer wall and along the longitudinal periphery thereof, a second pad eye 44. This pad eye 44 is preferably located mid-Way between the top and the bottom of the tubular member 20- so that any lateral pull applied thereto, such as by a vessel attached to the mooring chain or cable 46, will tend to pull the whole anchor 16 sideways rather than tend to cause a turning moment, which would result if the pad eye 44 should be located nearer to the top or bottom of the tubular member 20. If this pad eye 44 were located close to or at the top of the tubular member 20 and a lateral force were applied thereto, most of the pressure would be applied against the softer mud which exists near the surface of the bottom of the ocean thus causing more strain in the anchor 16 and increasing the possibility of some lateral slippage or bending thereof. The mooring chain 46 is shown, in the drawing of FIG. 1, connected to a float 48. However, it will be appreciated that the chain 46 is to be connected to a floating structure such as a drilling vessel along with possibly other chains from anchors of the same design to maintain the structure in a predetermined location so that drilling etc., can be carried on. The top pad eye 32 can be used not only for lowering the anchor 16 into the ocean bottom 18 position but may also be utilized as a mooring connection if predominately vertical forces are to be imposed upon the anchor.

Once the work vessel 12 is located over the anchor site, the anchor 16 is lowered from the working vessel 12 by means of a chain or cable 34 connected to the top pad eye 32. When the ocean bottom 18 is reached the open end 21 defined by the thin peripheral edge of the tubular member 20 of the anchor 16 will sink into the soft bottom 18 a distance dependent on the softness of the ocean bottom, the weight of the anchor 16 itself, and the seat 28. As the anchor 16 sinks into the ocean bottom 18, the water trapped within the tubular member 20- will pass out therefrom through the suction-fill pipe 36 and suction-discharge line 40. The pump 42 on the working vessel 12 is then utilized to pump the water from within the tubular member 20 and to create a vacuum therein which causes a pressure differential across the concrete-weight cap 24. Thus, the pressure differential and the weight of the anchor 16 itself is utilized to sink the anchor 16 into the bottom 18 the required distance. Once the anchor 16 is in place the suction-discharge line 40 is disconnected by operating the quick opening connector 38. The structure to be moored can then be connected to either the chain or cable connected to the lateral pad eye 44 or the vertical pad eye 32.

The anchor .16 is removed by reconnecting the suction- .discharge line 40 and reversing the pumps 42 so that water or air is pumped into the interior of the tubular member 20 to create pressure therein for the removal. Simultaneously with the pressurizing of the interior of the tubular member 20 of the anchor 16, a cable or chain 34 can be used to add a pull from the surface vessel 12 to aid in the removal of the anchor 16. Thus, the anchor 16 is entirely salvageable for further use. The insertion and removal of the anchor 16 in a deep water location without having to use a conventional pile driving means or drilling vesesl of some type is a decided advantage.

We claim:

1. A salvageable anchor for use in deep water by insertion thereof into a penetrable ocean floor, which anchor is capable of resisting vertical as well as horizontal forces exerted thereagainst, and which anchor comprises;

(a) an uprightly positioned tubular member (20) having an open lower end defined by a relatively thin penetrating edge adapted to penetrate an oceans floor,

(b) a closure plate (22) carried at the upper end of said tubular member,

(c) a weighted piece (24) supported against said closure plate and having a portion thereof extending radially beyond the upper edge of said tubular member,

(d) connection means (44) depending from an outer wall of said uprightly positioned tubular member and adapted to engage a mooring line extending toward the surface of said deep water, said connection means being disposed on said outer wall intermediate said closure plate and said thin penetrating edge,

whereby, when said tubular member is imbedded in said penetrable ocean floor, said connection means will be disposed beneath the surface of said ocean bottom.

2. An anchor as defined in claim 1 wherein said connection means (44) depending from the outer wall of said tubular member is disposed approximately midway between said closure plate and said penetrating edge.

3. A salvageable anchor as defined in claim 1 wherein said weighted member (24) comprises a cap carried on said closure member, and said portion of said weighted member extending radially beyond the outer edge of said tubular member comprises a peripheral lip defining a seat for resting against the surface of the penetrable ocean bottom to limit imbedment of said tubular member.

4. A salvageable anchor as defined in claim 1 wherein said closure plate (22) comprises a convex, dish shaped plate having a peripheral edge thereof fastened to the upper edge of said tubular member to form a fluid tight seal therewith, thereby defining an evacuable chamber in said tubular member when the penetrating edge of the latter contacts the ocean floor.

5. A salvageable anchor as defined in claim 4 wherein said closure plate includes a plurality of bar members (26) depending from said closure plate and engaging at least a portion of said weighted piece in supporting relation to the latter.

6. A salvageable anchor as defined in claim 4 including a valved connection opening externally to said tubular member and communicated with said evacuable chamber to define a passage for controlling the flow of fluid through said evacuable chamber.

References Cited UNITED STATES PATENTS 2,583,965 1/1952 Page et a1. 3,263,641 8/1966 Stimson 114 --206 OTHER REFERENCES 229,563 2/ 1925 Great Britain.

MILTON BUCHLER, Primary Examiner.

TRYGVE M. BLIX, Assistant Examiner.

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