US3398541A

US3398541A - Free flooding ballast system for offshore drilling rigs

Info

Publication number: US3398541A
Application number: US603845A
Authority: US
Inventors: Maurice B Thomas
Original assignee: Teledyne Inc
Current assignee: Teledyne Inc
Priority date: 1966-12-22
Filing date: 1966-12-22
Publication date: 1968-08-27
Anticipated expiration: 1985-08-27

Description

Aug. 27, 1968 M. B. THOMAS 3,398,541

FREE FLOODING BALLAST SYSTEM FOR OFFSHORE DRILLING RIGS Filed Dec, 1966 34- i L36, If 2\ I 3/ X. E

== nawm MGUf/C .49. 7770/7705 INVEN TOR United States Patent 3,398,541 FREE FLOODING BALLAST SYSTEM FOR OFFSHORE DRILLING RIGS Maurice B. Thomas, Houston, Tex., assignor to Teledyne, Ine., Hawthorne, Calif., a corporation of Delaware Filed Dec. 22, 1966, Ser. No. 603,845 7 Claims. (Cl. 6146.5)

ABSTRACT OF THE DISCLOSURE Generally, the present disclosure relates to apparatus utilized to insure the proper ballasting of an offshore drilling rig having an upper and lower hull in which the normally buoyant hull is to be lowered below the surface of water. This is accomplished by having an open inlet and outlet in the lower hull that communicates only with the atmosphere when the hull is in its raised position, but which becomes submerged as the hull is lowered to the bottom, thus allowing the inflow of water to ballast the hull.

The present invention relates to movable offshore platforms, and more particularly, to ballastin-g apparatus which are connected to the portion of the platforms which are to be lowered to the bottom of the body of water to act as a base for the support of the platform, the apparatus automatically flooding this portion as 1t 1s lowered and also preventing deballasting of this portion until it is again raised.

One popular embodiment of this type of offshore rig utilizes what are essentially two hulls, an upper and lower one. Both hulls are normally buoyant for greater stability while moving on and off location and while under tow. Upon arriving at the proposed well site, the upper hull which is floating on the surface lowers the lower hull to the bottom of the body of water. The lower hull rests on the bottom and forms a stabilizing base for the rig. The two hulls are connected by legs which are adjustably mounted on the upper hull for the raising and lowering of the lower hull. These legs support the upper hull which carries the drilling equipment, using the lower hull as a foundation or base.

As the lower hull is moved toward the bottom, it is, of course, necessary that it be properly ballasted to prevent the platform -from capsizing. It is also necessary to insure that the lower hull is not deballast as it begins its ascent from the ocean floor for the same reason. The problem presented is, therefore, to insure that the lower hull is not lowered to the ocean floor while retaining its buoyancy nor deballasted until it has been raised.

The present invention seeks to provide apparatus which will insure that, should the workmen forget to ballast the lower hull prior to its descent, it will be automatically ballasted as it begins its descent. This is achieved by having a normally open inlet and outlet in the lower hull and by having a casing or enclosure in fluid communication with the inlet and outlet but sealing them from the water itself. This casing or extension member extends from the lower hull in an upwardly direction a suflicient distance, whereby at least a portion of it is above the water surface when the lower hull is in its raised position, for example when it is being towed to the drill site. This portion contains an opening which is out of the water when the lower hull is in this raised position. As the hull and connected casing are lowered, however, this opening is submerged, allowing water to flow into the casing and through the inlet into the lower hull. In this manner the lower hull takes on water as it descends, the air in the hull escaping by means of the outlet. Since the opening in the casing and the inlet remain open at all times, flooding of the lower hull will be insured at 3,398,541 Patented Aug. 27, 1968 all times when the lower hull is a predetermined depth below the water level, whether it be ascending or descendmg.

It is, therefore, an object of the present invention to provide automatic ballasting apparatus to be used on olfshore platforms having upper and lower buoyant hull portions in which the lower hull portion is to be lowered from near the surface to form a supporting base for the platform.

It is a further object of the present invention to provide apparatus to insure free flooding of the lower hull or base portion of an offshore platform having upper and lower hulls when the lower hull is a predetermined distance below the surface of the water.

A still further object of the present invention is to utilize a continuously open inlet and outlet in the lower hull portion, which are sealed from the surrounding water by enclosure means when the hull portion is in its raised position.

An additional object of the present invention is to provide as part of the enclosure means, an opening in the enclosure means a predetermined distance above the lower hull, whereby, when the lower hull is this predetermined distance or a greater distance below the water surface, water is admitted to the enclosure means and hull.

A still further object of the present invention is to utilize a pump on the upper hull or platform portion having an intake opening removed from the pump and extending into the enclosure means when the lower hull is in its raised position for the removal of water or other ballasting substances.

Other and further objects, features and advantages will be apparent from the following description of a presently preferred embodiment of the invention given for the purpose of disclosure, and taken in conjunction with the accompanying drawing, where:

The figure discloses a side elevation of the present invention attached to a movable offshore platform having an upper and lower hull, portions thereof being in section for purposes of illustration.

The present invention will be described as utilized on an offshore drilling rig for drilling wells in the ocean floor. It is to be understood, of course, that the present invention may be utilized with any other type drilling rig or floating vessel having a portion which is usually buoyant and which is lowered in the water with respect to its rig or vessel.

Turning now to the drawing, there is shown a portion of a drilling rig as arranged for towing. A buoyant upper hull or platform 10 floats on the surface of the water 12. A lower hull 14 is located beneath, but adjacent to, the upper hull. Although when in this position, the lower hull possesses buoyancy, it is beneath the water level 12 due to the weight of the rig. The upper and lower hulls are connected to each other by a leg 16 which extends through a well 18 in the upper hull. A suitable raising and lowering mechanism is provided such as recessed teeth 20 which co-act with the toothed or sprocket members 22. The sprocket members 22 are driven by the engines 24 to provide means for raising and lowering the leg 16 and in turn the lower hull 14. Only one leg is shown in the drawing but such a rig will normally have at least three or usually four such legs.

Turning now to the lower hull 14, this hull is generally hollow and may be divided into compartments, An inlet opening 26 is located near the bottom of the lower hull, as can be seen in the drawing. Located near the top of the hull 14 is a second opening which is an outlet or vent 28.

A casing 30 contains passageway 31 which is in fluid communication with the

openings

26 and 28 by means of the

conduits

32 and 34, respectively. The casing 30 is also supported by these conduits although additional support ing structure may be desirable. The casing extends upwardly from the lower hull a suflicient distance to insure that a portion of the casing is above the water level 12 where hull 14 is in its raised position as shown in the drawing. The passageway 31 terminates at its uppermost end in opening 36.

A flooding valve 38 is located on the casing 30 beneath the water level. This valve opens and shuts the openended pipe 39 which communicates with the passageway 31. The valve 38 is controlled by the reach rod 40 which extends above the water level a distance sufiicient to allow a workman to open and close the valve from the upper hull or platform 10.

Mounted on the platform 42 is the motor 44 for the deep well pump, generally indicated at 46. The intake 48 for the pump is removed from the motor 44 a distance suflicient to allow it to reach almost to the bottom of the casing 30 when the lower hull 14 is in its raised position. The pipe 54 connecting the intake 48 to the motor 44 may be a relatively rigid member fixedly disposed and located to be received by the casing 30 whenever the lower hull is raised. Alternatively, it may be flexible and be inserted into or taken from the casing whenever desired.

Turning now to the operation of the disclosed apparatus, the upper and lower hulls 1t) and 14 are in the position shown in the drawing while being towed to the location at which the well will be drilled. The compactness of this arrangement and the combined buoyancy of the two hulls provide a relatively stable vessel for transportation purposes.

After the platform has been towed to the well site, the lower hull 14 is lowered to the ocean floor where it forms a stabilizing base for the upper hull.

To lower the hull 14, the motors 24 allow the sprocket members 22 to slowly rotate and co-act with the recessed teeth 20 to lower the hull beneath the water surface. After the hull 14 has reached the ocean floor, and has been securely positioned, the motors 24 continue to rotate members 22, thereby raising the upper hull 10 above the water level 12 a desired distance. Thus, the upper hull or platform is supported free of the water by the legs 16 which are securely positioned by the lower hull 14 resting on the bottom. Provision may be made in the lower hull to allow spuds to be driven through the hull and into the ocean floor for added stability.

As the lower hull 14 is lowered, it should be ballasted so as not to retain buoyancy in the lower hull. To provide this, the manually operated flooding valve 38 has been inserted in the casing 30. Prior to the lowering of the hull, but after the rig has been towed to the well site, a workman rotates the handle on the valve reach rod 40 to open the valve 38, allowing water to flow into the casing. This water will pass through the conduit 32 and opening 26 and into the lower hull. Air which is in the lower hull will be forced out of the vent or opening 28 and conduit 34 to casing 30. It will then rise and pass out of the Opening 36. In this manner, the lower hull is filled with water either completely or to the extent desired prior to its being lowered.

The problem, however, develops when the workmen forget to flood the lower hull 14 before lowering it. This problem is overcome in the present invention by the use of the normally opened intake 26 and outlet 28 communicating with the casing 30. As the lower hull begins its descent, the opening 36 in the upper end of the casing 30 will travel only a relatively short distance before it is submerged. When submerged, water will flow into the opening 36, down the casing 30 and through the intake 26. Once again, air in the lower hull will be forced out of the vent or outlet 28 by the incoming water and through the opening 35.

After the drilling operation is complete and the lower hull 14 has been raised from the ocean floor for movement of the drilling rig, it is desirable to remove the water from the lower hull for ease in towing the rig. For this purpose, the pump 46 is mounted on the upper hull 10. As was mentioned, the hose 50 connecting the intake 48 to the pump motor 44 may be either .a flexible or a rigid member If it is rigid, the platform 42 is so positioned that the intake end 48 is received within the casing as the lower hull 14 approaches the upper hull. In such an arrangement, the intake 48 would be automatically inserted into the casing 30 as the hull 14 is raised.

An alternative embodiment is to have the tubular member 50 comprised of flexible material, such as a hose, whereby the intake 48 may be inserted into the casing after the hull is completely raised and taken therefrom whenever desired. In either embodiment, the intake 48 extends into the casing a distance sufficient to remove essentially all of the water from the lower hull 14. However, it is to be noted that the lower hull 14 cannot be prematurely deballasted until the hull 14 is in the raised position thereby preventing overturning of the rig 10.

It is also anticipated that the free flooding system may operate through a well in the upper hull similar to the well 18 for the leg 16. This would prevent the free flooding apparatus from extending over the edge of the rig, thereby protecting it from possible damage by being struck against other vessels, docks or the like.

The use of several of the disclosed free-flooding ballast systems is preferable in movable platforms of substantial size. Also the lower hull 14 may be divided into watertight compartments. In such cases, it would be necessary to have inlets and outlets for each compartment. These may be operated from one free-flooding system by running several conduits, such as 32 and 34, off of a single casing. Several of the free-flooding ballast systems may be spaced about the rig for each compartment.

As can be seen, therefore, the present invention achieves the objectives set forth at the outset. Apparatus has been devised which insures the automatic flooding or ballasting of the base or lower hull portion of movable offshore platforms as they are lowered to the ocean floor. Provision has been made for manual flooding of the lower hull, but should this be overlooked, ballasting of the lower hull will automatically take place. Furthermore, the lower hull cannot be accidently deballasted until it has been raised to a safe position. Control of the system takes place from the upper hull or platform, thereby reducing or eliminating the necessity of sending personnel into deep water to the lower bull or through the legs into the lower hull.

The present invention is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein. While the presently preferred embodiment of the invention has been given for the purpose of disclosure, numerous changes in the detail of construction and the combination, shape, size and arrangement of parts may be resorted to without departure from the spirit and scope of the invention as hereinafter claimed.

. What is claimed is:

1. In a movable platform to be used on a body of water, including a buoyant upper hull, a buoyant lower hull, means interconnecting the hulls for movement of the lower hull from .a position adjacent the upper hull to the bottom of the body of water where said lower hull forms a supporting base for the upper hull, said interconnecting means coacting with said base to support, in a stationary manner, said upper hull on or above the surface of said body of water, the improvement comprising, automatic ballasting means for said lower hull, including,

an opening in said lower hull, at least a portion of said opening being adjacent the top of the lower hull,

means connected to the lower hull for movement therewith and enclosing said opening in a water tight manner, preventing the flow of water through said opening when the hulls are adjacent,

a portion of said means extending above the water a predetermined distance when the hulls are adjacent, and

inlet means in said portion of said connecting means in fluid communication with said openings whereby when said lower hull moves from its position adjacent the upper hull toward the bottom of a body of water a distance equal to said predetermined distance, said inlet means is submerged, thereby allowing water to flow therethrough and into said opening, the air in said buoyant lower hull passing out of said opening and said inlet means.

2. In a movable platform to be used on a body of water, including a buoyant upper hull, a buoyant lower hull, means interconnecting the hulls for movement of the lower hull from a position adjacent the upper hull to the bottom of the body of water where said lower hull forms a supporting base for the upper hull, said interconnecting means coacting with said base to support, in a stationary manner, said upper hull on or above the surface of said body of water, the improvement comprising, automatic ballasting means for said lower hull, including,

at least two openings on said lower hull, one of which is normally under water,

means connected to the lower hull for movement therewith and enclosing said openings for preventing the inflow of water when the hulls are adjacent,

inlet means in said portion in fluid communication with said openings, whereby when said lower hull moves from its position adjacent the upper hull toward the bottom of the body of water a distance equal to said predetermined distance, said inlet means is submerged, thereby allowing water to flow therethrough, thus flooding the lower hull.

3. The invention of claim 2 wherein,

said opening which is normally under water comprises an inlet for water to flow into said lower hull,

said other opening comprises an outlet for the escape of air from said lower hull as is flooded, and said extension means is further defined as including,

an essentially vertically extending casing attached to said lower hull for movement therewith,

the lower portion of said casing connected in a watertight manner to said inlet and outlet, and said inlet means is further defined as including,

an opening in said casing, and

a passageway within said casing connecting in fluid communication said last-mentioned opening to the inlet and outlet.

4. The invention of claim 3 and including,

flooding means in fluid communication with said inlet,

and

control means for operating said flooding means, said control means being controlled from said upper hull, at least when said hulls are adjacent.

5. The invention of claim 4 wherein the flooding means is further defined as including,

a second opening in said casing which is normally underwater and,

a valve for opening and closing said second opening operatively connected to said control means,

said control means being manually operated, a portion thereof extending upwardly a distance suflicient to be operated from the upper hull when the lower hull is adjacent thereto.

6. The invention of claim 5 and including,

a pump on said upper hull, and

a pump intake removed from the pump a suflicient distance to extend through said opening and passageway to the lower portion of said casing when said lower hull is adjacent the upper hull for the removal of water from said lower hull.

7. In a movable offshore platform for use on a body of water, having buoyant and adjacent upper and lower hulls, legs interconnecting the hulls for movement of the lower hull to the bottom of the body of water to act as a supporting base for the upper hull, the improvement comprising automatic ballasting means for the lower hull including,

an inlet near the bottom of the lower hull and being normally under water,

an outlet near the top of the lower hull,

an elongate casing connected to said lower hull, one

end of said casing extending a predetermined distance above the water surface,

an opening in said one end,

a passageway in said casing,

nates in said opening,

conduit connecting in a watertight manner the inlet and outlet in fluid communication with said passageway, whereby when the lower hull is moved toward the bottom of the body of water, the opening becomes submerged when said lower hull has traveled a distance equal to said predetermined distance, thus allowing water to flow into said opening and flood the lower hull,

a second opening on said casing in fluid communication with the passageway said second opening being normally underwater,

a manually operated valve for opening and closing said second opening,

control means for operating said valve operatively connected to the valve and extending above the water level a distance suflicient to be reached from the upper hull for operative purposes, when the hulls are adjacent,

a pump attached to the upper hull, and

an intake connected to said pump but removed therefrom a sutficient distance for insertion into the passageway a depth equal to the inlet for removal of water from the lower hull.

one end of which termi- References Cited UNITED STATES PATENTS JACOB SHAPIRO, Primary Examiner.