OA18989A - Buoyant structure for petroleum drilling - Google Patents

Abstract

A buoyant structure having a hull, a planar keel defining a lower hull diameter, a lower cylindrical portion connected to the planar keel, a lower frustoconical portion disposed above the lower cylindrical portion with inwardly sloping wall at a first angle, an upper frustoconical portion directly connected to the lower frustoconical portion, and the upper frustoconical portion with outwardly sloping wall, the inwardly sloping wall abutting the outwardly sloping wall forming a hull neck with a hull neck diameter. The buoyant structure having a main deck, a moon pool, and propellers attached to the planar keel, which are operated by a motor or a generator. The buoyant structure connects over a chambered buoyant storage ring.

Description

BUOYANT STRUCTURE FOR PETROLEUM DRILLING

CROSS REFERENCE TO RELATED APPLICATIONS

The current application claims priorily to and the benefit of co-pending US Utility Patent Application Serial No.: 14/452,826 filed on August 06, 2014, which claims priority to and the benefit of co-pending US Provisional Patent Application Serial No.: 61/872,515 filed on August 30, 2013, both entilled “BUOYANT STRUCTURE FOR PETROLEUM DRILLING, PRODUCTION, STORAGE AND OFFLOADING”. These référencés are incorporated in their entirety.

FIELD

The present embodiments generally relate to a buoyant structure for petroleum drilling, production, storage and offloading.

BACKGROUND

A need exists for a highly stable buoyant structure that is a floaling vessel that can be lowed from drilling location to drilling location at sea or rnoves on its own power, and which additionally provides storage for tubulars in chambers, preventing lubulars front rolling off into the sea.

A need exists l'or a drilling vessel that does not easily list.

A further need exists for larger moon pool in a drilling vessel to provide safer drilling operations for handling of equipment and personnel and to provide a larger contained space for making up tubulars and performing topsides subsea drilling activity lhe present embodiments meet these needs.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description will be better understood in conjunction with the accompanying drawings as follows:

Figure l depicts the buoyant structure in a deballasted state.

Figure 2 depicts the buoyant structure in a ballasted state.

Figure 3 depicts a back view of a ballasted buoyant structure floating.

Figure 4 depicts a cross section of the hull.

Figure 5A depicts a plan view of the lower cylindrical portion of the buoyant structure.

Figure 5B depicts another plan view of the lower cylindrical portion.

Figure 6 depicts a detailed view of a plurality of displaceinent réduction devices.

Figure 7 depicts a buoyant structure with a derrick.

Figure 8 depicts a top view of tire watertight conipartments between the inner hull side and outer hull side of the buoyant structure.

l igure 9 depicts a detailed view of one of the heave control terraccs mounted to the wall portion.

Figure I0 depicts an embodiment of the buoyant structure supported over a chambered buoyant storage ring.

Figure 11 depicts a top view of the chambered buoyant storage ring.

Figure 12Λ depicts an embodiment of a bulkheaded storage section with two outer stabs.

Figure 12B depicts an embodiment of a bulkheaded storage section with an inner stab.

Figure I2C dcpicts an embodiment of a bulkheaded storage section with two outer stabs and one inner stab.

The present embodiments are delaiied below with reference to the listed Figures.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Before explaining the present apparatus in detail, it is to be understood that the apparatus is not limited to the particular embodiments and that il can be practiced or carried out in various ways.

The present embodiments relate to a buoyant structure for petroleum drilling, production, storage and offloading, that has a hull that is of a unique shape defining a vertical axis which can be ballasted and deballasted for drilling operation and nondrilling operation modes, respectively.

Ilte hull is characterized by circular horizontal cross-sections ai ail élévations.

'Ihe hull can be defined from the portion that would be closest to the sea fioor. This first portion is a planar keel defining a lower hull diameter shown as Di in the Figures.

The hull can hâve a lower cylindrical portion connected to the planar keel. The lower cylindrical portion diameter Dj can be the largest diameter of the hull,

The hull can further hâve a lower frustoconical portion disposed above the lower cylindrical portion.

The lower frustoconical portion can hâve inwardly sloping walls at a first angle. These inwardly sloping walls slope away from the circumference of the lower cylindrical portion towards the vertical axis.

The term “inwardly sloping” as used herein can refer to a slope that is away from the perimeter or circumfcrence and towards the vertical axis. The inwardly sloping walls slope at angles generally front 50 degrees lo 70 degrecs as measured against the vertical axis.

The hull can hâve an upper frustoconical portion directly connected to the lower 5 frustoconical portion.

The upper frustoconical portion can hâve outwardly sloping walls and the lowcr frustoconical portion can hâve an inwardly sloping wall sloping at a second angle relative lo the vertical axis.

The outwardly sloping wall can be al a second angle with respect to the vertical axis ³ from 3 degrecs to 45 degrees.

dite outwardly sloping wall abuts the inwardly sloping wall forming a hull neck with a hull neck diameter D₃.

The hull can hâve a hull height which is defined from the planar kecl to a main deck. The hull height defined from the planar keel to the main deck is from 45 percent to ’ 90 percent of lhe hull neck diameter D₃.

The hull height can range from 30 meters to 80 meters.

The hull neck diameter D₃ can be the smallest diameter D₃ of the hull. The hull neck diameter D₃ can bc from 75 percent to 90 percent of the upper hull diameter D₂.

In embodiments, the main deck can be a generally horizontal main deck thaï additionally defines an upper hull diameter D₂.

The main deck can be connected over the upper frustoconical portion and can hâve a navigation lower, héliport, receiving deck space for cargo, mooring Lie downs, shark jaws used for towing, and space for additional equipment not limited to a derrick, accumulator, hoisl, generators, top drives for the derrick, and devices for picking up j and making up lubulars.

The hull can hâve a lower cylindrical portion diameter Dj that is from 115 percent to 130 percent of the upper hull diameter Dj.

Within the hull, below the main deck and above the planar keel can be a moon pool.

In embodiments, a plurality of watertight compartments can be posîtioned between the outer hull side and the moon pool.

The moon pool can hâve a moon pool diameter that can be tapered and generally increasing inside toward the planar keel.

The moon pool can hâve a first or initial moon pool diameter proximale the main deck which can be small and then that diameter can gradually increase as the moon pool diameter approaches the planar keel.

In embodiments, the moon pool is in the shape of a hall ellipse with a minor radius of the ellipse being from 10 percent to 30 percent of the diameter of the upper hull diameter and a major radius of the ellipse being from 25 percent to 50 percent of the upper hull diameter.

In embodiments, the hull can contain a first tunnel thaï is an opening in the wall of the lower cylindrical portion and extends through to the moon pool.

The first tunnel can hâve a first tunnel side wall, a second tunnel side wall and a tunnel top connecting the tunnel side walls.

The tunnel serves to reduce friction of water during transport or transit of the buoyant structure.

A plurality of heave control terraces can be formed in a wall portion that surrounds the moon pool in the hull and adjacent the water of the moon pool. The plurality of heave control terraces can be in the wall portions around the moon pool and proximale to the planar keel adjacent the water in the moon pool.

The plurality of heave control terraces can exlend away from the wall portion for controlling heave in the moon pool by reducing up and downward duust of Lhe water in the moon pool area.

Propellers can be attached to the planar keel and operated by a motor, such as a diesel motor, with a diesel electric generator, wherein the motor and generator can 5 connect to a fuel tank. In embodiments the fuel tank can hold 75,000 barrels of diesel.

The propellers, motor, and generator area can contmunicate with a control center, such as in the pilot house, having a navigation System, such as a global positioning system (GPS), a dynaniic positioning system (DPS) or other navigation system. The 10 control center can use the navigation System to dynamically position the buoyant structure over a well for drilling or for propulsion for transit, such as to another location.

Λ plurality of ballast tanks, which can hâve punips, can be connected to lhe control center for ballasting and deballasting the hull on demand. The ballast tanks may 15 incorporate material of varions densities to affect pitch and roll.

The buoyant structure provides high reserve buoyancy due to a continuation of a symmeLrical water line.

The buoyant structure has a hull that protects personnel and equipment and drilling fluids from unexpecled instabilily by the use of controlled water ballast Systems 20 within the hull compartments.

The moon pool of the buoyant structure provides increased safe work environment for drilling personnel in ail weather conditions by enable workers to work on many levels of a moon pool without being exposed to arctic winds, or harsh rain, or gale force slorms.

The buoyant structure provides a stable power consumption régime as a floating drilling platform, as the hull is not required to weathervane. This buoyant structure allows lhe hull to use dynamic positioning and therefore be less sensitive to drastic environmental changes in directions, such as when hurricane force i winds are coming from the Southwest then magically swing around lo be coming from the northwest, this huit, using dynamic positioning, can more easily handle these wind changes compared lo a moored vessel.

In embodiments, the buoyant structure can be moored.

The design of the hull of lhe buoyant structure provides a high freeboard therefore reduces the likelihood of personnel being exposed to green water.

The buoyant structure provides a réduction in sensitive structural areas being exposed to wave slamming forces impacts during operational conditions,

The buoyant structure can be ballastcd and deballasted using a plurality of ballast compartmenls with connected waler pumps to partially iïll with ballast sea water to stabilize the hull, providing increased safety for personnel and equipment against any collisions by rogue floating objects. When compared to scmisubmersibles, the buoyant hull reduces the pemicability of spontaneous flooding in void spaees.

In embodiments, the buoyant structure can hâve an outer hull side and an inner hull side which can be separaled by waterlight compartments.

In embodiments, the buoyant structure can hâve an upper cylindrical portion connected between lhe deck and the upper frustoconical portion.

In embodiments, the buoyant structure can hâve a first tunnel and a second tunnel extcnding through the lower cylindrical portion to the moon pool.

Ifie second tunnel can be connected to the First tunnel at an angle from 180 degrees to 270 degrees in a first direction and al an angle from 180 degrees to 90 degrees in a second direction from lhe First tunnel.

The second tunnel can hâve a pair of second tunnel sides walls connected with a second tunnel top.

In embodiments, the buoyant structure can hâve a plurality of tunnels extending through the lower cylindrical portion. In other embodiments, the tunnels can form a peace sign of a first tunnel connected lo a second and third tunnel at an angle.

In embodiments, the buoyant structure can hâve the first and second tunnels fluidiy connected through the moon pool at a 180 degree angle.

The tunnels can each hâve boitoms that exlcnd the length of the tunnel. The reason for the bottoms for ihe tunnels is to reduce the buildup of hydrostatic résistance during transit speeds through the water column and the réduction of trappcd water within the moon pool to reduce displacemenl.

In embodiments, the moon pool can be centraliy disposed around the vertical axis. The moon pool can also be posilioned off center of the vertical axis, such as in a side of the hull.

The terni “bell shaped” as used herein means an elliptical shape that is spccifically a half elliptical shape; with the narrow end of the elliptical shape proximate the main deck.

ITie tenu “bell shaped” also refers to an elliptical shape transitioning to a cylindrical shape at the portion of the bell shape that is proximate the planar keel.

The tenu “bell shaped” as used herein also refers to a géodésie curve, which is known lo be a séries of straight lines connecting nodes positioned on a half elliptical curve creating inward sloping walls.

In metric geonietry, a géodésie shape is formed using a curve which is everywhere locally as a distance minimizer. More precisely, a curve γ: 7—► M from an interval l ol the reals lo the metric space M is a géodésie if there is a constant v > 0 such that for any i e 7 there is a neighborhood J of t in I such that for any r_h t₂ € J the formula is creaied 71 )ï7^— E’Rl ή?|·

In metric geonietry the géodésie considcred is often equipped with natural parameterization, thaï is, in the above identity y = l and = Ht - l₂|.

If lhe last equality is satisfied for ail z₂ G/, the géodésie is called a mininiizing géodésie or shortest path. Such a géodésie shape with a mininiizing path is used in this invention.

In embodiments, the buoyant structure has a first moon pool diameter proximale the main dcck that gradually increases towards a sea bottom at a plurality of variable rates. The moon pool can connect with lower decks first then the main deck.

The moon pool diameter can increase at a different rate for different sections of heights from the first moon pool diameter to a second moon pool diameter.

In embodiments, the buoyant structure can hâve multiple connected heave control terraces. In embodiments, the heave control lerraces can be staggered as they are positioned around the wall portion of the moon pool.

In embodiments, the heave control terraces can each hâve a length from l meler to 20 meters, a width from 0.5 meters to 3 melers, and a height from 3 centimeters to 20 centimeters. In other embodiments, the heave control terraces can hâve different dimensions within the above ranges.

In embodiments, lhe heave control terraces can each hâve a plurality of perforations. The term “perforations” as used herein can refer to holes made in the heave control terraces. In embodiments, some heave terraces can hâve perforations while others do not.

In embodiments, the buoyant structure can hâve heave control terraces made from either 3 centimeters thick corrugated Steel plate creating waves from l centimeler to 15 centimeters in height or smooth Steel plate.

In embodiments, the buoyant structure can hâve a first displacement réduction device formed in either the upper frusloconical portion or the lower frustoconical portion. The term “displacement réduction device” can refer to a bucket shaped device having a bucket bottom, a bucket first side, and a bucket second side connected to the bucket bottom.

In embodiments, the buoyanl structure can hâve a second displacement réduction device formed in the frustoconical portion which does not contain the first displacement réduction device.

In embodiments, the buoyant structure can hâve a plurality of displacement réduction devices formed in the upper frustoconical portion, the lower frustoconical portion or combinations thereof.

In embodiments, the buoyanl structure can hâve a plurality of decks formed in the hull between the main deck and lower frustoconical portion. Each deek can extend from the moon pool to the inner hull side, except for the main deck which can extend to the outer wall. Examples of whal is on the decks can include mezzanine deck and cellar deck.

In embodiments, the buoyant structure can hâve a water Light storage chamber for storing tubulars usable in drilling operations.

The tubulars can be drill pipe, casing, marine risers, and combinations thereof.

In embodiments, the vertical storage chamber can be disposed in parallel to the vertical axis and the vertical storage chamber can be accessible from one or more of the plurality of decks, the moon pool and combinations thereof.

In embodiments, the buoyant structure can hâve multiple propellers mounted to the planar keel, connected to diesel-electric motors with connected fuel powered generators, and a control center having a navigation system. The propellers with motors and generators can be connected to the navigation system providing propulsion and dynamic positioning. The navigation system can connect to a satellite dynamic positioning system allowing for remote dynamic positioning of the vessel.

In embodiments, the planar keel can be a planar horizontal keel. The keel can be slightly rounded in embodiments, for faster transiting and lower fuel consomption.

In embodiments, the moon pool can hâve a constant diameter portion wherein the constant diameter is from the keel to up to 16 meLers from the keel.

In an embodiment, the buoyant structure can be positioned over and connected to a ehambered buoyant storage ring formed from a plurality of interlocking sections or segments.

In embodiments, the ehambered buoyant storage ring can be towable and modular with each section being individually ballasted. The ehambered buoyant storage ring ¹ θ can croate a semi-permanent subsea landing platform for the buoyant structure.

'Fhe ehambered buoyant storage ring can, in embodiments, safely dock and lock, beneath the buoyant structure allowing drilling through an opening in both the buoyant structure and in the ehambered buoyant storage ring thereby creating an environmentally safe, operationally containable environment.

The coupled buoyant structure with interlocking modular ehambered buoyant storage ring can be particularly usable for arctic, shallow water conditions.

In an embodiment, multiple ehambered buoyant storage rings can be connected in sériés thereby daisy-chaining storage and flow lines together to optimize subsea architecture to support the production for full field development.

Prcset flanges and piping can be used on the ehambered buoyant storage ring for connecting to the buoyant structure and between sections of the storage ring.

Preset intakes, internai piping, and prcset out-lakes can be used enabling the towable modular interlocking ehambered buoyant storage rings lo hâve quick connect, and inter-connectability, enabling the units lo be enlarged as drilling occurs.

One of lhe benefits of the towable modular inierlocking ehambered buoyant storage ring is spill containment for a well Lhal erupts.

| Preset out-takes can be used enabling the modular intcrlocking chambered buoyanl ring to siphon off (such as transfer) hydrocarbons from the storage ring to an adjacent floating storage vessel by means of a pre-connected flow line attached to one of the preset Ranges on the storage ring.

| A benefil of the invention is that the buoyanl structure can be posilioned over a damaged well, allowing hydrocarbons including volatile organic carbons, to be sucked away and transferred to a tanker or barge, for nearby correct environmental containment and storage.

| In an embodiment, each towable modular interlocking chambered buoyanl storage ring can contain from 4597 cubic meters to 305614 cubic melers of fluid storage, such as hydrocarbon storage.

i In an embodiment, the chambered buoyanl storage ring can hâve 3 to 4 bulkheaded storage sections interlocking as jigsaw puzzle pièces.

| Dimensionally, the towable modular interlocking chambered buoyant storage rings can hâve a heighl from 10 feet to 60 feet, can hâve a deballasted depth, which is known as transit depth, of 10 feet to 20 feet, and can hâve a ballasted depth of 20 feet to 40 feet.

ΊΊΐβ towable modular interlocking chambered buoyanl storage ring can be ballasted to float completely underwater. Each bulkheaded storage section can be ballasted to individually float underwater.

Tuming now to the Figures, Figure 1 depicts the buoyanl structure in a deballasted state, such as when in transit. Figure 2 depicts the buoyant structure in a ballasted state, such as an operational condition for drilling a well or working over a well.

Referring to Figures I and 2, the buoyant structure 10 can include a hull 12 with a vertical axis 14 and an upper hull diameter D2.

The hull 12 can hâve an outer hull side connected to an inner hull side. The outer hull side can be characterized by an outer hull shape selected from die group; circular, elliptoid, and géodésie in horizontal cross-sections at ail élévations. The inner hull side can be characterized by a shape selected from the group: circular, elliptoid, and géodésie.

In embodiments, the hull 12 can include a planar keel 20 defining a lower hull diameter Dj, and a lower cylindrical portion 22 connected to the planar keel 20.

In embodiments, the lower cylindrical portion 22 can hâve a diameter identical to the lower hull diameter Dj. and both diaineters can be the largest diameter of the hull. ^ΓΙ1ιο lower hull diameter Dj can be from 101 percent to 130 percent of the upper hull diameter D2.

In embodiments, a lower frustoconical portion 24 can be disposed above the lower cylindrical portion 22. The lower frustoconical portion 24 can hâve an inwardly sloping wall 25 that is created at a first angle 26. l’he first angle 26, with respect to the vertical axis 14, can range from 50 degrces to 70 degrees.

The hull 12 can include an upper frustoconical portion 28, which can be directly connected to the lower frustoconical portion 24. The upper frustoconical portion 28 can hâve an oulwardly sloping wall 29 at a second angle 30. The second angle can be from 3 degrees to 45 degrces from the vertical axis. The second angle can be particularly advantageous for ice breaking conditions in the arctic.

The lower frustoconical portion can hâve an inwardly sloping wall 25 that abuls the oulwardly sloping wall 29. The intersection of the two walls can form a hull neck 32 with a hull neck diameter D3. The hull neck diameter can be at least 10 percent less than the lower hull diameter.

The buoyant structure can hâve a hull height 34 measured from the planar keel 20 to a main deck 36. In embodiments, the main deck 36 can be connected over the upper frustoconical portion 28. In embodiments, the main deck 36 can bc round, square or reclangular in shape.

In embodiments, the lower cylindrical portion 22 can hâve a diameter from 115 percent to 130 percent of the upper hul 1 diameter D₂.

In embodiments, the buoyant structure can hâve a moon pool centrally formed around the vertical axis or offset from the vertical axis.

The buoyant structure 10 can hâve a first tunnel 64 which can extend through the lowcr cylindrical portion to the moon pool. The first tunnel can hâve a first tunnel side wall 66, a second tunnel side wall 68, and a first tunnel top 70 connecting the tunnel side walls. In embodiments, the first tunnel can hâve a first tunnel bottom 72 that connects the tunnel sides. The first tunnel can be square or rectangular in cross section, and can hâve another usable geonietry that allows egress of beats, material or both from the moon pool.

The water level 96 can be at a height between the planar keel 20 and the lower frustoconical portion 24 when the hull is deballasted and ready for transit, as shown in Figure 1.

The water level 96 can be al a height between the upper frustoconical portion 28 and the main deck 36 when the buoyant structure is ballasted and ready for drilling operation, as shown in Figure 2.

An upper cylindrical portion 62 can be between the main deck 36 and the upper frustoconical portion 28. The upper cylindrical portion 62 can be used for storing machines and bulk materials.

The buoyant structure 10 can hâve a motor 46 connected to a generator 48, connected to a fuel tank 50 positioned below the main deck in the upper cylindrical portion 62. In embodiments, the motor can be a diesel-electric motor. In embodiments, there can be more than one motor. In embodiments, each motor can produce 9000 hp. In embodiments the generator can be a diesel operated generator, such as a generator from Wartsilla or Siemens lhal can be used with a capacity of 36+ mégawatts of power.

Ilie motor 46 and generator 48 can be in communication with a control center 52 mounted above the main deck. The control center 52 can hâve a navigation system 54 in communication with lhe motor and generator. In embodiments, the total capacity of the motors can be 38 mégawatts. A pilot house can act as the control center 52 which can contain a computer with software to provide a navigation System 54 used for navigation with satellites of a dynamic positioning system or with another network, such as a global positioning system network.

Propellers can be secured to lhe planar keel and can be operated by lhe motor. The control center can use Lhe navigation system 54 to dynamically position the ballasted buoyant structure over a well for drilling. In embodiments, the control center can use the navigation system 54 to drive and slcer the buoyant structure using the propellers for propulsion during transit when deballastcd.

ITte buoyant structure can be moored to the sea bed or to structures positioned under water.

The control center can control a plurality of ballast tanks connected to the main deck or mounled on the buoyant vessel above the planar keel for ballasting and deballasting the hull. fhe buoyant structure can define a center of gravity and a center of buoyancy with Lhe center of gravity being below lire center of gravity.

The buoyant structure can include a lower keel frustoconical portion 23 extending from the lower cylindrical portion 22 in a direction away from the vertical axis. In embodiments, the lower keel frustoconical portion 23 can extend from 4Ü percent to 95 percent lhe vertical height of the lower cylindrical portion and can extend ai an angle from 30 degrees to 70 degrees from the vertical axis.

Figure 3 depicts a back view of a ballasted buoyant structure Clearing.

Figure 3 has all the sanie parts as Figures 1 and 2 excepl a second tunnel is depicted.

The buoyant structure 10 is shown with the hull 12 with a vertical axis 14; planar keel 20 with a lower cylindrical portion 22, lower frustoconical portion 24 and lower keel frustoconical portion 23; inwardly sloping wall 25 of the lower frustoconical 5 portion is at a first angle 26; outwardly sloping wall 29 of the upper frustoconical portion 28 at a second angle 30; hull neck 32; total hull height 34; main deck 36; motor 46; generator 48; fuel tank 50; control center 52 with a navigation system 54; upper cylindrical portion; water level 96; lower hull diameter Dj; upper hull diameter D_2; and hull neck diameter D₃.

The buoyant structure can have a second tunnel 74. The second tunnel can hâve a first second tunnel side wall 76, a second second tunnel side wall 78 and a second tunnel top 80 that connects between the second tunnel side walls. In embodiments, the second tunnel 74 can have a second tunnel bottom 82 connected between the second tunnel side walls.

In embodiments, the second tunnel can be at an angle from 180 degrees to 270 degrees from the first tunnel. In embodiments, the second tunnel bottom can extend the entire lengdi of the second tunnel. In embodiments, the water can fi 11 the first or second tunnel to any height from dry to the maximum height of the tunnel. In embodiments a plurality of tunnels can be created between the outside walls of the buoyant structure and the moon pool. The tunnels can be used to reduce the résistance of lhe hull through a water column when the buoyant structure is in transit.

Figure 4 depicts a cross section of lhe hull.

Ihe buoyant structure is shown ballasted down with 50 percent of lhe hull 12 below 25 lhe water level 96 for operations, such as drilling or working over wells.

The hull 12 can have an outer hull side 16 and an inner hull side 18. 'Ihe hull sides can be formed front Steel plates. The planar keel 20 can be made from the same sleel as the outer hull side and inner hull side.

Propellers 44a and 44b can extend from the planar keel. The propellers can be four bladed and can be azimuth thruslers in an embodiment. The propellers can be mounted and dismounted without the nced for dry dock.

'Ihe lower cylindrical portion 22 can extend above the planar keel and can hâve a diametcr of 112 meters. The lower frustoconical portion can hâve inwardly sloping wall 25 at an angle of 60 degrees.

The buoyant structure can include lower decks 37a and 37b that can support bulk storage, such as for drilling muds and cernent. In embodiments, the lower decks can be used l’or handling equipment for blow out preventers or tubulars.

'ITie buoyant structure can include a moon pool 38. The moon pool can be bell shaped. The moon pool can be formed by the inner hull side characterized by a shape selected from the group: circular, elliptoid, and géodésie,

The moon pool can hâve a first moon pool diameler 40 proximale the main deck 36 which can increase to a second moon pool dianieter 42 proximale the planar keel. The second moon pool dianieter can be smaller than the upper hull dianieter.

In embodiments wherein the moon pool has an elliptoid shape, the moon pool can hâve a moon pool minor radius 84 and a moon pool major radius 86. The moon pool minor radius can be 10 percent to 30 percent Üie dianieter of the main deck, and the moon pool major radius can be 25 percent to 50 percent the dianieter of the main deck.

The moon pool can hâve a moon pool height 88.

The moon pool can hâve a constant dianieter section 90 formed in the lowcr cylindrical portion 22 extending to the planar keel 20. In embodiments, the constant diametcr section 90 can hâve a dianieter of 9 nieters. In embodiments, the constant diameter section can exlend up to 16 meters from the planar keel.

The buoyant structure can hâve a plurality of heave control terraccs 92a-92f. Each heave control tcrrace does not hold water. Each heave control terrace can act as a baffle and générâtes drag on the water to stop inslability of the buoyant structure. In 5 embodiments, the heave control lerraces can be staggered or can be identical in length. A minimum of three heave control lerraces can be used in an embodiment.

The heave control lerraces can be attached to a wall portion 94 of the moon pool, 'lhe wall portion can be attached to the lower decks 37a and 37b.

Ai least one ballast tank 58a can bc mounted within the hull in communication with the control conter, lhe ballast tank can bc used for ballasting and deballasling the hull.

Figure 5A depicts a plan view of the lower cylindrical portion of the buoyant structure.

The lower cylindrical portion 22 can hâve a first tunnel 64 and second tunnel 74 15 formed therein with the buoyant structure in a ballasted operational condition.

A first hydro transit diverter bulkhead 75a can be fonned between a side wall of lhe first tunnel and a side wall of the second tunnel. The first hydro transit diverter bulkhead can be solid and can align and mirror the curve of the inner hull side 18 forming the moon pool 38. 3he hydro transit diverter bulkhead can mirror a curve 20 that is a circular, elliptoid or géodésie.

A second hydro transit diverter bulkhead 75b can be formed between a side wall of a first tunnel and a side wall of a second tunnel and fonned in a straight line across lhe moon pool 38.

In an embodiment, the second hydro transit diverter bulkhead 75b can be solid and 25 can cross from one side of Lhe first tunnel to an opposite side of the second tunnel across the moon pool 38.

In the embodiment, the second hydro transit diverter bulkhead can contain ballast tank compartments 79a and 79b in communication with the control center ibr use in stabilizing the buoyant structure.

In an embodiment, the hydro transit diverter bulkhead can be formed between a side wall of a first tunnel and simply extend partiaîly into the moon pool from an inner hull side. In embodiments, at least one of lhe hydro transit diverter bulkheads can be attached to lhe planar keel.

Figure 5B depicts another plan view of the lower cylindrical portion 22.

¹⁰ At least a portion of lhe inner hull side 18 can hâve a géodésie shape. In embodiments, the moon pool 38 into which the first tunnel 64 and second tunnel 74 conncct can be 100 percent géodésie in shape, or 100 percent curved completely surrounding the moon pool.

Figure 6 depicts a detailed view of a plurality of displacement réduction devices.

A first displacement réduction device 9la can be in the upper frustoconical portion of lhe hull. A second displacement réduction device 9lb can be in the lower cylindrical portion 22 with a lower keel frustoconical portion 23 extending from the lower cylindrical portion.

In embodiments, the first displacement réduction device can eliminate an amount of ²⁰ friction from the outer water column and the entrapped displacement in the moon pool area. In embodiments, only one displacement réduction device can be used.

The lower cylindrical portion 22 can hâve a second displacement réduction device 91 b opposite the first displacement réduction device 91. The displacement réduction devices can be identical in size and shape or can vary in size and shape. The 25 displacement réduction devices can be installed in groups around the outer hull side, such as groups of three or four.

The displacement réduction devices can be eut outs in the hull to change the displacement, like a window in the hull without glass. The size of the displacement réduction devices can hâve a length from lü feet to 20 feet and a height from 10 feet 5 to 20 feet.

Figure 7 depicts a buoyant structure with a derrick.

The buoyant structure 10 can hâve a derrick 2 mounted on the main deck. In embodiments, the derrick can be incorporated into die hull.

The buoyant structure can hâve a lower center of gravity 400 than the center of 10 buoyancy 402. The center of gravity and center of buoyancy can occur in the moon pool 38.

The buoyant structure 10 can include the outer hull side 16, inner hull side 18, planar keel 20, propellers 44a and 44b, helipad 57, ballast tanks 58a and 58b, heave control terraces 92, wall portion 94 of the moon pool, vertical axis 14, lower keel 15 frustoconical portion 23, and control center 52 with navigation system 54.

The navigation system 54 can be in communication with the motor 46 and the generator 48. ITic navigation System 54 for dynamic positioning can be a unit from Raytheon.

Up ^t0 eight propellers or thrusters can be used for good dynamic positioning. 'ITie fuel tank 50 can be connected to the generator. In embodiments, the fuel tank can engage both the motor and generator simultaneously.

Λ pilot house can include the control center, which can additionally hâve Controls for not only the motor, but also Controls for safety equipment, Controls for the ballast 25 system, communications such as to the Internet and satellite Systems, and aviation communication.

The buoyanl structure, in embodiments, can include accommodations 53 for crew which can include galleys, statcrooms, salons, office space, hospital, radio, machine shops and lest labs.

Ifre well 56 to be drilled by the buoyanl structure can be an oil well or a natural gas well.

In embodiments, from 10 ballast tanks to 40 ballast tanks can be used in the buoyanl structure, each of which can also be controlled from the control center 52.

In embodiments, buoyanl structure can include sanilation Systems, Pire control equipment, and emergency évacuation equipment, such as lifeboats.

'ITic buoyant structure can also accommodate a flare, a crâne, a bulk connection station, blowout protection and marine riser Systems, and a remotely operated vehicle station.

In embodiments, the derrick can be a single hoist or dual hoist derrick with associated top drives and hcave compcnsators along with tubular make up and break oui equipment.

In embodiments, the hull can accommodate 30,000 metric tons of variable deck load to accommodate a drilling operation of a well thaï has a 40,000 foot well deplh and is in 12,000 feel of water.

Figure 8 depicts a top view of the walertight compartments 60a-60d between the inner hull side 18 and outer hull side 16 of the buoyanl structure.

In an embodiment the total height of the hull from keel to main deck can be 52 meters. ’llie height to the top of the drill floor can be 60 meters. The height to the top of the helipad can be 64 meters. The height to the top of the derrick can be 130 meters.

Figure 9 dcpicts a detailed view of one of the heave control terraces 92 mounted to the wall portion 94. 'lhe heave control lerraces can hâve a plurality of perforations 98a-98f.

The perforations can range in diameter from 50 centimeters to 60 cenlinieters. The perforations can be randomly positioned on the heave control terraccs. The perforations can be used to allow flow through of water and reduce a maximum buildup of water pressure in the moon pool.

Figure 10 depicts an embodiment of the buoyant structure 10 supported over a chambered buoyant storage ring 300 formed from a plurality of bulkheaded storage sections 302a-302d.

In an embodiment, the chambered buoyant storage ring 300 is positionable and lockable beneath the buoyant structure allowing drilling using the buoyant structure simukaneously with lhe chambered buoyant storage ring through the moon pool of the buoyant structure and through a central opening 303 in lhe chambered storage ring establishing an cnvironmentally safe containcd environment for operations.

The chambered buoyant storage ring 300 can hâve a plurality of bulkheaded storage sections 302a-302d each having a roof 306 over a chamber 304 for storing at least one of: fluids, solids, and gasses, such as hydrocarbons including oil. The bulkheaded storage sections can be intcrconnccted and double walled.

Figure 11 depicts a top view of the chambered buoyant storage ring.

The chambered buoyant storage ring 300 can provide a semi-permanent subsea landing platform for the buoyant structure.

In embodiments, the chambered buoyant storage ring can provide a flush engagement with the planar keel or an engagement using outer stabs and inner stabs, enabling at least one of: a subsea operation and a reservoir operation through the moon pool and lhe central opening simukaneously.

When the chambered buoyant storage ring and the buoyant structure are connected, an environmenlally saie condition for subsea or réservoir operations can be created.

Each bulkheaded storage section 302a-302d can hâve an inlet port 3O8a-3O8d and outlet port 3O9a-3O9d l’or flowing al least one of: fluids, solids and gases into or out of the chamber.

Each bulkheaded storage section 302a-302d can hâve a réceptacle 31 la-31 Id on one side and an interlocking finger 3l2a-3l2d on the other side for engaging the réceptacle of an adjacent bulkheaded storage section, allowing the bulkheaded storage sections to inlerlock together.

Figure 12A depicts an embodiment of a bulkheaded storage section 302a with two θ outer stabs 3l0a and 3 lüb. The outer stabs can rise in parallel on one side, to an outer périmeter of the bulkheaded storage sections.

Figure 12B depicts an embodiment of a bulkheaded storage section 302b with an inner stab 313.

Figure 12C depicts an embodiment of a bulkheaded storage section 302c with two 15 outer stabs 310a and 3l0b and one inner stab 313.

The chambered buoyant storage ring storage ring 302c can further hâve a continuous scouring prévention stabilizer 320. In embodiments, a continuous prévention scouring stabilizer can be connected lo each interlocking segment of the chambered buoyant storage ring on an outer wall.

The continuous scouring prévention stabilizer can extend in a direction away from the vertical axis when the buoyant structure is mounted lo the chambered buoyant storage ring. The continuous scouring prévention stabilizer, in embodiments, can extend from 40 percent to 95 percent the vertical height of one of lhe bulkheaded storage sections. lhe continuous scouring prévention stabilizer, in embodiments, can 25 extend from the outer wall of the bulkheaded storage section at an angle from 30 degrees to 70 degrees from the outer wall.

The outer slabs can be formed front Steel and rise from l foot to 15 feet from the roof. Each outer stab can hâve a width across the roof from l foot to 15 feet. In embodiments, the outer stabs can be square or rectangular. The inner stabs can be identical to Lhe outer stabs.

The following describes lhe sequence of steps usablc in the method that utilizes the buoyanl structure.

The buoyant structure can be used in three phases, phase l : load oui, phase 2: transit and phase 3: operations.

The following describes the sequence of steps for phase l : load out.

θ lhe method can include conditioning the buoyant structure’s hu11, drilling equipment and ballast tanks with seawater to provide a minimum draft, from 4 mcters to 15 meters in this embodiment, to accotmnodate mobilization of the marine equipment and drilling equipment in préparation for offshore drilling areas.

This allows the buoyant structure to be made ready in shallow water ports thaï are 15 not usable by semisubmcrsibles or drill ships thaï require greater drafts. In this step, the bell shaped moon pool contains the least amount of water enabling physical inspection of the hull, and rigging up equipment prior to use offshore.

The method can include loading lhe drilling equipment necessary for a full campaign onto the buoyanl structure while the buoyant structure is debaliasted and in port. lhe θ drilling equipment can include drilling pipes, marine risers, casings, and single/dual blowout preventers.

The following describes the sequence of steps for phase 2: transit.

The method can include identifying a drilling location for destination, starting lhe thrusters, and leaving port in a deballasted/transil condition.

The method can include arriving at the identified drilling location and engaging the dynamic positioning system to maintain the buoyanl structure over die subsea drilling location.

The method can include ballasling the buoyanl structure to operational draft al the drilling location while the dynamic positioning System is operating, ensuring that the lower cylindrical portion, the lower frustoconical portion and a portion of the upper frustoconical portion arc underwater and the ballast tanks are full or at least partially filled to lower the center of gravity and contribute to maintaining a positive stability curve for the buoyanl structure at ail times.

Lf tunnels are used in an embodiment, the tunnels will significantly reduce water drag while the buoyant structure is in transit or while the buoyanl structure is in operation and allow positive water flow through the horizontal water collar, effeetively reducing the hydrodynamic résistance (drag force) and négative effect on displacement caused by water trapped inside the huli.

Once on drilling location, the structure will initiate the distribution of seawater ballast within the structure, thereby allowing the structure to adjust from transit draft to operational draft.

Ihe ballasted unit will lower the centcr of gravity and contribute to a maintaining al ail times a positive stability curve.

Ihe power distribution and control of the thruster, coupled with State of the art computerized dynamic station-keeping of the structure and the drilling equipment located in and on top ol the moon pool and on the deck will be centered over the selected subsea drilling location.

The performance of the drilling equipment and highesl safety of operability attributes are the allowable offset tolérances of the buoyant structure, its moon pool and the influence of the environment in any operational theater.

The buoyant structure operating envelope is dictated by wind speed, current, hydrodynamic environment, coupled with thruster utilizalion and dynamic allowances. Those results are couplet! with operational displacemenl parameters of the structure underwater hulL

The following describes the sequence of steps for phase 3: operations. Operations include the operation of the ballastcd buoyant structure while at a subsea drilling location.

'ITie method can include coupling compulerized dynamic station keeping of the buoyant structure with power management and initiating operation of drilling equipment located in and on top of the moon pool and on the deck while the buoyant structure is centcred over the subsea drilling location using an onboard processor and data storage in the control center, wherein the onboard data storage has computer instructions to manage the structure operating envelope including using sensed wind speed, sensed current, and actual dynamic positîoning thrusler ulilization compared to preset operational displacemenl parameters of the buoyant structure while operating drilling equipment.

The following steps can be performed while the buoyant structure is in the operational condition. In the operational condition, the buoyant structure has been bailasted and also displacemenl réduction devices engaged.

The method can include placing the displacemenl réduction devices sufficiently below the surface water, allowing the trapped water within the moon pool to communicate with the external hydrodynamic environment l'or enhanced stability while operating drilling equipment.

The method can include using tunnels to improve the overall displacement of moon pool water thus increasing the stability and operational envelope of the buoyant structure.

The method can include attaching the heave control lerraces to the walls of the moon pool to break up the water column inside the moon pool, liais operation will reduce the buoyant struclure’s heave and also allow access to walkways and safety steps within the circumfercnce of the moon pool.

While thèse embodiments hâve bcen described with emphasis on the embodiments, it should be understood that within the scope of the appended claims, the embodiments might be practiced other than as specifically described herein.

Claims (25)

1. Whal is claimed is:

   l. Λ buoyant structure for at least one of: petroleum drilling, production, storage, and offloading, wherein the buoyant structure comprises:

   a. a hull defining a vertical axis, whereby the hull has an outer hull side connected to an inner hull side, and the outer hull side is characterized by an outer hull side shape selected from lhe group: circular, elliptoid, and géodésie in horizontal cross-sections at ail élévations; and the hull has an upper hull diameter and the inner hull side characterized hy a shape selected from the group: circular, elliptoid, and géodésie;

   b. a planar keel defining a lower hull diameter;

   e. a lower cylindrical portion connected to the planar keel, wherein an lower cylindrical portion diameter is identical to the lower hull diameter, and the lower hull diameter is the largest diameter of the hull, and further wherein the lower cylindrical portion diameter is from 105 percent to 130 percent of the upper hull diameter;

   d. a lower frustoconical portion disposed above the lower cylindrical portion formed with an inwardly sloping wall at a first angle ranging from 50 degrees to 70 degrees with respect to the vertical axis;

   e. an upper frustoconical portion directly connected to the lower frustoconical portion, lhe upper frustoconical portion with an outwardly sloping wall sloping at a second angle with respect to the vertical axis from 3 degrees to 45 degrees, and wherein the lower frustoconical portion with the inwardly sloping wall, abuls lhe outwardly sloping wall forming a hull neck with a hull neck diameter;

   f. a main deck connected over the upper frustoconical portion;

   g. a moon pool formed by the inner hull side characterized by a shape selected from the group: circular, elliptoid, and géodésie having a first moon pool diameter proximate the main deck which increases to a second moon pool diameter proximate the planar keel wherein llie second moon pool diameter is less than the upper hull diameter; and

   h. at least one ballast tank in communication with a control center in the hull, the at least one ballast tank is for ballasting and deballasting the hull; and wherein the buoyant structure delînes a center of gravity below a center of buoyancy in the moon pool.
2. 2. The buoyant structure of claim 1, further comprising propellers attached to the planar keel operated by a motor, connected to a generator, with the motor and the generator connected to a fuel tank, with the propellers, the motor, and the generator communicating with a navigation system in a control center mounted above the main deck with the control center using the navigation system to dynamically position the ballasted buoyant structure over a well for drilling or for propulsion during transit when deballasted.
3. 3. The buoyant structure of claim 1, comprising a plurality of waterlight compartiments between the outer hull side and the inner hull side.
4. 4. Ihe buoyant structure ol claim 1, comprising an upper cylindrical portion connected between the main deck and the upper frustoconical portion.
5. 5. l'he buoyant structure of claim 1, comprising a first tunnel extending through the lower cylindrical portion to the moon pool, wherein the first tunnel has a first tunnel first side wall, a lirst tunnel second side wall and a first tunnel top connecting the first tunnel side walls.
6. 6. The buoyant structure of claim 5, comprising a first tunnel bottom connected between the first tunnel side walls.
7. 7. The buoyant structure of claim 5, comprising a second tunnel extending through the lower cylindrical portion into the nioon pool, the second tunnel comprising a pair of second tunnel side walls connected with a second tunnel top.
8. 8. 'Ihc buoyant structure of claim 7, comprising a second tunnel botlom in the second tunnel connected between the second tunnel side walls.
9. 9. The buoyant structure of claim l, wherein the moon pool is centrally formed around the vertical axis.
10. 10. The buoyant structure of claim l, wherein an elliptoid moon pool has a minor radius which is 10 percent to 30 percent the diameter of the main deck and a major radius which is 25 percent to 50 percent the diameter of the main deck.
11. 11. The buoyant structure of claim l, comprising a constant diameter portion for the moon pool that extends up to 16 meters from the planar keel and is formed in the lower cylindrical portion extending to the planar keel.
12. 12. The buoyant structure of claim l, comprising a plurality of heave control terraces formed in a wall portion of the moon pool.
13. 13. The buoyant structure of claim l, comprising a lower keel frustoconical portion extending from the lower cylindrical portion in a direction away front the vertical axis.
14. 14. The buoyant structure of claim 12, comprising a plurality of perforations in each of the plurality of heave control terraces.
15. 15. ITie buoyant structure of claim l, comprising a first displacement réduction device formed in the upper frustoconical portion or the lower frustoconical portion.
16. 16. The buoyant structure of claim 15, comprising a second displacement réduction device formed in the upper frustoconical portion or lower frustoconical portion opposite the first displacement réduction device.
17. 17. The buoyant structure of claim 1, comprising a plurality of lower dccks formed in the hull between the main deck and the lower frustoconical portion.
18. 18. The buoyant structure of claim 1, comprising: a chambered buoyant storage ring with an opening mounted to the hull of the buoyant structure, the chambered buoyant storage ring providing a semi-permanent subsea landing platform for a buoyant vessel, wherein the

    5 chambered buoyant storage ring provides an engagement with the planar keel enabling at least one of: a subsea operation and a reservoir operation through the moon pool and the opening, simultaneously, creating an environmenlally safe condition for the subsea operation, the reservoir operation, or both the subsea operation and the reservoir operation.
19. 19. Ihe buoyant structure of claim 18, wherein the chambered buoyant storage ring comprises a plurality of bulkheaded storage sections, wherein each bulkheaded storage section comprises:

    a. a chamber for storing fluids, solids, gases, or combinations thereof;

    b. a roof over the chamber;

    ¹⁵ c. an inlet port and an outlet port for flowing fluids, solids, gases, or combinations thereof into or out of the chamber;

    d. a réceptacle on each bulkheaded storage section; and

    e. an interlocking finger on each bulkheaded storage section for engaging a réceptacle on an adjacent bulkheaded storage section allowing bulkheaded storage sections to interlock together.
20. 20. Ihe buoyant structure ol claim 19, wherein each bulkheaded storage section comprises an outer stab, an inner stab, or both the outer stab and the inner stab.

    Ihe buoyant structure of claim 18, wherein the chambered buoyant storage ring has a capacity from 4597 cubic meters to 305614 cubic meters.

    The buoyant structure of claim 18, wherein the chambered buoyant storage ring comprises from three to four bulkheaded storage sections interlocking as jigsaw puzzle pièces.
21. 23. The buoyant structure of claim 19, wherein each bulkheaded storage section is ballasted to float underwater.

    5
22. 24. The buoyant structure of claim 5, comprising a hydro transit diverter bulkhead formed between al least one of the first tunnel side walls of the first tunnel exlending into the moon pool attached to the planar keel.
23. 25. The buoyant structure of claim 18, comprising a continuous scouring prévention stabilizer connected around the chambered buoyant storage ring.
24. 26. The buoyanl structure of claim 1, comprising a derrick, a helipad, accommodations, or combinations thereof.
25. 27. The buoyanl structure of claim 24, comprising al least one ballast tank compartment formed in the hydro transit diverter bulkhead.