OA13023A - System and method of installing and maintaining anoffshore exploration and production system having an adjustable buoyancy chamber. - Google Patents

Abstract

A system and method of establishing an offshore exploration and production system is disclosed, in which a well casing (2) is disposed in communication with an adjustable buoyancy chamber (9) and a well hole (3) bored into the floor of a body of water. A lower connecting member (5) joins the well casing (2) and the chamber, and an upper connecting member (12) joins the adjustable buoyancy chamber (9) and a well terminal member (14). The chamber's adjustable buoyancy enables an operator to vary the height or depth of the well terminal member (14), and to vary the vertical tension imparted to drilling and production strings throughout exploration and production operations. Also disclosed is a system and method of adjusting the height or depth of a wellhead while associated vertical and lateral forces remain approximately constant. A variety of well isolation members (4), lateral stabilizers (6) and anchoring means (8), as well as several methods of practicing the invention, are also disclosed.

Description

013023

SYSTEM AND METHOD OFINSTALLING AND MAINTAINING ANOFFSHORE EXPLORATION AND PRODUCTION SYSTEM HAVINGAN ADJUSTABLE BUOYANCY CHAMBER

Related Application

The instant application is a continuation-in-part of prior provisionalapplication no. 60/606,335 fïled September 1, 2004.

Field of the Invention

The présent invention relates generally to oil and gas exploration andproduction, and in a spécifie, non-limiting embodiment, to a System and method ofinstalling and maintaining an offshore exploration and production System havingan adjustable buoyancy chamber.

Background of the Invention

Innumerable Systems and methods hâve been employed in efforts to findand recover hydrocarbon reserves around the world. At first, such efforts werelimited to land operations involving simple but effective drilling methods thatsatisfactorily recovered reserves from large, productive fields. As the number ofknown producing fields dwindled, however, it became necessary to search in evermore remote locales, and to move offshore, in the search for new resources.Eventually, sophisticated drilling Systems and advanced signal processingtechniques enabled oil and gas companies to search virtually anywhere in theworld for recoverable hydrocarbons.

Initially, deepwater exploration and production efforts consisted ofexpensive, large scale drilling operations supported by tanker storage andtransportation Systems, due primarily to the fact that most offshore drilling sites areassociated with difficult and hazardous sea conditions, and thus large scaleoperations provided the most stable and cost-effective manner in which to searchfor and recover hydrocarbon reserves. A major drawback to the large-scaleparadigm, however, is that explorers and producers hâve little financial incentive

DUPLICATA 1 to work smaller reserves, since potential financial recovery is generally offset bythe lengthy delay between exploration and production (approximately 3 to 7 years)and the large capital investment required for conventional platforms and relateddrilling and production equipment. Moreover, complex regulatory Controls and 5 industry-wide risk aversion hâve led to standardization, leaving operators with fewopportunities to significantly alter the prevailing paradigm. As a resuit, offshoredrilling operations hâve traditionally been burdened with long delays betweeninvestment and profit, excessive cost overruns, and slow, inflexible recoverystrategies dictated by the operational environment. 10 More recently, deepwater sites hâve been found in which much of the danger and instability présent in such operations is avoided. For example, off thecoast of West Africa, Indonesia and Brazil, potential drilling sites hâve beenidentified where surrounding seas and weather conditions are relatively mild andcalm in comparison to other, more volatile sites such as the Gulf of Mexico and the 15 North Sea. These recently discovered sites tend to hâve favorable producingcharacteristics, yield positive exploration success rates, and admit to productionusing simple drilling techniques similar to those employed in dry land or near-shore operations.

However, since lognormal distributions of recoverable reserves tend to be 20 spread over a large number of small fields, each of which yield less than wouldnormally be required in order to justify the expense of a conventional large-scaleoperation, these régions hâve to date been underexplored and underproducedrelative to its potential. Consequently, many potentially productive smaller fieldshâve already been discovered, but remain undeveloped due to économie 25 considérations. In response, explorers and producers hâve adapted theirtechnologies in an attempt to achieve greater profîtability by downsizing the scaleof operations and otherwise reducing expense, so that recovery from smaller fieldsmakes more financial sense, and the delay between investment and profîtability isreduced. 30 For example, in published Patent Application No. US 2001/0047869 Al and a number of related pending applications and patents issued to Hopper et al.,

DUPLICATA 2 013023 various methods of drilling deepwater wells are provided in which adjustments tothe drilling System can be made so as to ensure a better recovery rate than wouldotherwise be possible with traditional fixed-well technologies. However, theHopper System cannot be adjusted during completion, testing and production of thewell, and is especially ineffective in instances where the well bore starts at a mudline in a vertical position. The Hopper System also fails to support a variety ofdifferent surface loads, and is therefore self-limiting with respect to the flexibilitydrillers desire during actual operations.

In U.S. Letters Patent No. 4,223,737 to O’Reilly, a method is disclosed inwhich the problems associated with traditional, vertically oriented operations areaddressed. The method of O’Reilly involves laying out a number ofinterconnected, horizontally disposed pipes in a string just above the sea floor(along with a blow out preventer and other necessary equipment), and then using adrive or a remote operated vehicle to force the string horizontally into the drillingmedium. The O’Reilly System, however, is inflexible in that it fails to admit topractice while the well is being completed and tested. Moreover, the methodutterly fails to contemplate functionality during production and workoveroperations. In short, the O’Reilly reference is helpful only during the initial stagesof drilling a well, and would therefore not be looked to as a systemic solution forestablishing and maintaining a deepwater exploration and production operation.

Other offshore operators hâve attempted to solve the problems associatedwith deepwater drilling by effectively “raising the floor” of an underwater well bydisposing a submerged wellhead above a self-contained, rigid framework of pipecasing that is tensioned by means of a gas filled, buoyant chamber. For example,as seen in prior U.S. Letters Patent No. 6,196,322 B1 to Magnussen, the AtlantisDeepwater Technology Holding Group has developed an artificial buoyant seabed(ABS) System, which is essentially a gas filled buoyancy chamber deployed inconjunction with one or more segments of pipe casing disposed at a depth ofbetween 600 and 900 feet beneath the surface of a body of water. After the ABSwellhead is fitted with a blowout preventer during drilling, or with a productiontree during production, buoyancy and tension are imparted by the ABS to a lower DUPLICATA 3 013023 connecting member and ail internai casings. The BOP and riser (during drilling)and production tree (during production), are supported by the lifting force of thebuoyancy chamber. Offset of the wellhead is reasonably controlled by means ofvertical tension resulting from the buoyancy of the ABS. 5 The Atlantis ABS System is déficient, however, in several practical respects.

For example, the ‘322 Magnussen patent specifïcally limits deployment of thebuoyancy chamber to environments where the influence of surface waves iseffectively negligible, i.e., at a depth of more than about 500 feet beneath thesurface, Those of ordinary skill in the art will appreciate that deployment at such 10 depths is an expensive and relatively risk-laden solution, given that installation andmaintenance can only be carried out by deep sea divers or remotely operatedvehicles, and the fact that a relatively extensive transport System must still beinstalled between the top of the buoyancy chamber and the bottom of an associatedrecovery vessel in order to initiate production from the well. 15 The Magnussen System also fails to contemplate multiple anchoring

Systems, even in instances where problematic drilling environments are likely to beencountered.. Moreover, the System lacks any control means for controllingadjustment of either vertical tension or wellhead depth during production andworkover operations, and expressly teaches away from the use of latéral stabilizers 20 that could enable the wellhead to be deployed in shallower waters subject tostronger tidal and wave forces.

Thus, there is plainly a widespread need for a System and method ofdisposing an offshore wellhead in a manner such that drillers can adjust both thedepth of a wellhead and the vertical tension applied to associated pipe casing 25 throughout the duration of exploration and production operations. There is also aneed for an adjustable buoyancy chamber System capable of maintainingapproximately constant vertical tension on an associated drilling or productionstring, and adjusting either the height of a wellhead at any time during explorationand production by releasing additional lengths of tension line fforn a buoyancy 30 chamber height adjustment member. There is also a need for an offshoreexploration and production System that flexibly admits to use in connection with DUPLICATA 4 013023 both deepwater and shallow target horizons, without necessarily being configuredto conform to any particular operational depth.

Brief Description of the Drawings 5 Figure 1 is a side view of an offshore exploration and production System in which an adjustable buoyancy chamber is employed to adjust the height or depthof an associated well terminal member.

Figures 2A and 2B are side views of an offshore exploration and productionSystem, in which latéral and vertical forces on an adjustable buoyancy chamber are 10 held approximately constant while the height of an associated well terminalmember is adjusted by releasing additional lengths of tension line.

Summary of the Invention A System and method of establishing an offshore exploration and 15 production System is provided, in which a well casing is disposed incommunication with an adjustable buoyancy chamber and a well hole bored intothe floor of a body of water. A lower connecting member joins the well casing andthe chamber, and an upper connecting member joins the adjustable buoyancychamber and a well terminal member. The chamber’s adjustable buoyancy enables 20 an operator to vary the height or depth of the well terminal member, and to varythe vertical tension imparted to drilling and production strings throughoutexploration and production operations. Also provided is a System and method ofadjusting the height or depth of a wellhead while associated vertical and latéralforces remain approximately constant. A variety of well isolation members, latéral 25 stabilizers and anchoring means, as well as several methods of practicing theinvention, are also disclosed.

Detailed Description

Refening now to the spécifie, non-limiting embodiment of the invention 30 depicted in Figure 1, an offshore exploration and production System is provided,comprising a well casing 2 installed in communication with a submerged well 1 duplicata 013023 and an adjustable buoyancy chamber 9, wherein a lower connecting member 5 isdisposed between the well casing and the adjustable buoyancy chamber. In apresently preferred embodiment, the well 1 is accessed from above by means of awell hole 3 that has been bored into an associated sea floor surface. In a typical 5 embodiment, a well casing 2 is set into the hole in a firm and secure manner, andthen cemented into place using known downhole technology. In otherembodiments, a well casing is securely set into the well hole 3, and a fluidtransport member, such as a smaller-diameter pipe or pipe casing, is inserted intowell casing 2. Once a desired fit has been achieved, the outer surface of the fluid 10 transport member is cemented or set with a packer to the inner surface of the wellcasing. Those of ordinary skill in the art will appreciate that while the embodimentdescribed above refers to but a single well, the offshore exploration and productionSystem disclosed herein can be readily adapted to simultaneously work multipleneighboring wells without departing from the scope or spirit of the invention. 15 According to a one embodiment, a well isolation member 4 is disposed between well casing 2 and a lower connecting member 5. In some embodiments,well isolation member 4 comprises one or more bail valves, which, if lowerconnecting member 5 is removed, can be closed so that the well is effectively shutin. In further embodiments, well isolation member 4 comprises a blowout 20 preventer or a shear ram that can be maintained in either an open or closed positionin order to provide access to, or to instead shut in, the contents of well 1.

In other embodiments, lower connecting member 5 further comprises one ormore receiving members disposed to receive an attachment member disposed onwell isolation member 4. In an alternative embodiment, lower connecting member 25 5 comprises an attachment member for attaching said lower connecting member 5 to a receiving member disposed on well isolation member 4. Methods and meansof securely fastening lower connecting member 5 to well isolation member 4 areknown to those of ordinary skill in the art, and may comprise one or more of awide variety of fastening techniques, e.g., hydraulic couplers, various nut and boit 30 assemblies, welded joints, pressure fittings (either with or without gaskets),swâging, etc., without departing from the scope or spirit of the présent invention. DUPLICATA 6 013023

Likewise, lower connecting member 5 may comprise any known connectingmeans appropriate for the spécifie application contemplated by operators. Forexample, in various embodiments, lower connecting member 5 comprises one ormore of segments of riser, riser pipe, and/or pipe casing. In some embodiments,lower connecting member 5 comprises a concentric arrangement, for example, afluid transport member having a smaller outer diameter than the inner diameter ofa pipe casing in which the fluid transport member is housed.

In further embodiments, lower connecting member 5 is disposed incommunication with one or more latéral stabilizers 6, which, when deployed inconjunction a plurality of tension lines 7, effectively Controls horizontal offset ofthe System. By utilizing the buoyant forces of adjustable buoyancy chamber 9,lower connecting member 5 is drawn taut and held in a stable position.

In an alternative embodiment, one or more stabilizers 6 control horizontaloffset of lower connecting member 5, and the height or depth of an associated wellterminal member 14 is adjusted by varying the length of upper connecting member 12. In some embodiments, the vertical tension of lower connecting member 5 isheld approximately constant while the height or depth of well terminal member 14is adjusted. In further embodiments, the height or depth of well terminal member14 is held approximately constant, while the vertical tension imparted byadjustable buoyancy chamber 9 on lower connecting member 5 is adjusted. In stillfurther embodiments, the height or depth of well terminal member 14 and thevertical tension applied to lower connecting member 5 are held approximatelyconstant, while latéral adjustments are performed using latéral stabilizer 6 and oneor more of tension lines 7.

In certain embodiments, one or more latéral tension lines 7 are individuallyadjustable, whereas in other embodiments, the tension lines 7 are collectivelyadjustable. In further embodiments, one or more tension lines 7 are bothindividually and collectively adjustable. In still further embodiments, the one ormore latéral stabilizers 6 are disposed in communication with a tension measuringmeans, so that a fixed or predetermined amount of latéral tension can be applied tolower connecting member 5 in order to better control System offset. In some DUPLICATA 7 013023 embodiments, the tension Unes 7 are anchored to the sea floor by means of ananchoring member 8, for example, a suction type anchor, or altematively, amechanical or conventional deadweight type anchor.

In a presently preferred embodiment, adjustable buoyancy chamber 9 isapproximately annular in shape, so that lower connecting member 5 can be passedthrough a void longitudinally disposed in a central portion of the device. In furtherembodiments, adjustable buoyancy chamber 9 further comprises a plurality ofinner chambers. In still further embodiments, each of the chambers isindependently opérable, and different amounts of air or gas (or another fluid) aredisposed in the chambers to provide greater adjustable buoyancy control. In oneexample embodiment, adjustable buoyancy chamber 9 further comprises a fluidballast that can be ejected from the chamber, thereby achieving greater chamberbuoyancy and lending additional vertical tension to lower connecting member 5.Those of ordinary skill in the art will appreciate that many appropriate fluid ballastcan be used to increase or retard buoyancy; for example, compressed air is anappropriate fluid that is both inexpensive and readily available.

In some embodiments, adjustable buoyancy chamber 9 further comprises aballast input valve, so that a fluid ballast can be injected into the chamber from anextemal source, for example, through an umbilical line run to the surface or aremote operated vehicle, so that an operator can deliver a supply of compressedgas to the chamber via the umbilical, thereby adjusting buoyancy characteristics asdesired. In other embodiments, the fluid input valve is disposed in communicationwith one or more pumps or compressors, so that the fluid ballast is delivered to thechamber under greater pressure, thereby effecting the desired change in buoyancymore quickly and reliably.

In other embodiments, adjustable buoyancy chamber 9 further comprises aballast output valve, so that ballast can be discharged from the chamber. Ininstances where air or another light fluid is injected into the chamber while wateror another heavy liquid is discharged, the chamber will become more buoyant andincrease vertical tension on lower connecting member 5. Conversely, if water oranother heavy liquid is injected into the chamber while air is bled out, the chamber DUPLICATA 8 013023 will lose buoyancy, thereby lessening vertical tension on lower connecting member 5. ' -

In alternative embodiments, the ballast output valve is disposed incommunication with one or more pumps or compressors, so that ballast is ejectedfrom the chamber in a more reliable and controlled manner. In someembodiments, the ballast output valve is disposed in communication with anumbilical, so that ballast ejected from the chamber can be recovered or recycled atthe surface. In any event, a principle advantage of the présent invention is thatadjustments to the chamber’s buoyancy and tensioning properties, and the abilityto control the height of the well terminal member 14, can be performed at any timeduring either exploration or production, due to the various ballast input and outputcontrol means disposed about the body of the chamber.

In further embodiments, adjustable buoyancy chamber 9 is further disposedin communication with one or more tension lines 10 provided to anchor theadjustable buoyancy chamber to the sea floor. As before, tension lines 10 areanchored to the seâ floor using known anchoring technology, for example, suctionanchors or dead weight type anchors, etc. The one or more tension lines 10 canalso provide additional latéral stability for the System, especially during operationsin which more than one well is being worked. In one embodiment, the one ormore tension lines 10 are run from the adjustable buoyancy chamber 9 to thesurface, and then moored to other buoys or a surface-vessel, etc., so that evengreater latéral tension and System stability are achieved. In further embodiments,the tension lines 10 are individually adjustable, whereas in other embodiments, thetension lines 10 are collectively controlled. In still further embodiments, the oneor more tension lines 10 are both individually and collectively adjustable.

In one example embodiment, adjustable buoyancy chamber 9 is disposed incommunication with a vertical tension receiving member 11. In anotherembodiment, the vertical tension receiving member 11 is equipped with a tensionmeasuring means (e.g., a load cell, strain gauge, etc.), so that vertical tensionapplied to lower connecting member 5 is imparted in a more controlled andefficient manner. In another embodiment, the buoyant force applied to tension DUPLICATA 9 013023 receiving member 11 is adjusted by varying the lengths of tension lines 10, whilethe buoyancy of adjustable buoyancy chamber 9 is held approximately constant.

In a further embodiment, the buoyancy of adjustable buoyancy chamber 9 iscontrolled by means of one or more individually selectable ballast exhaust portsdisposed about the body of the chamber, which vent excess ballast fluid to thesurrounding sea. In still further embodiments, the open or closed State of theballast exhaust ports are individually controlled using port controllers known tothose of ordinary skill in the art (e.g., plugs, seacocks, etc.)

In a presently preferred embodiment, the System is disposed so that a wellterminal member 14 installed above buoyancy chamber 9 is submerged to a depthat which maintenance and testing can be carried out by SCUBA divers usinglightweight, flexible diving equipment, for example, at a depth of about 100 to 300feet beneath the surface. In some embodiments, the well terminal member 14 issubmerged only to the minimum depth necessary to provide topside access to thehulls of various surface vessels servicing the well, meaning that well terminalmember 14 could also be disposed at a much shallower depth, for example, a depthof about 50 to 100 feet. In alternative embodiments, well terminal member 14 isdisposed at depths of less than 50 feet, or greater than 300 feet, depending upon theactual conditions surrounding operations. In still further embodiments, wellterminal member 14 is disposed either at the surface or above the surface of thewater, and a blowout preventer or a production tree is installed by workersoperating aboard a service platform or surface vessel. This “damp tree” modelavoids the need to assemble long subsurface riser stacks, as would generally berequired during deepwater operations. Moreover, disposing the well terminalmember at or near the surface also permits testing and maintenance to be carriedout by SCUBA divers or surface crews, without the need for expensive and time-consuming remote operated vehicle operations.

In some embodiments, well terminal member 14 further comprises either ablowout preventer or a production tree. In a presently preferred embodiment,however, well terminal member 14 further comprises a combined blowout

DUPLICATA 10 013023 preventer and production tree assembly confïgured so as to facilitate simplifîedwell intervention operations.

In some embodiments, lower connecting member 5 terminâtes within thevoid formed in a center portion of the annular chamber 9, at which point an upperconnecting member 12 becomes the means by which fluids are transported up tothe wellhead. In other embodiments, lower connecting member 5 does notterminate within the void formed in a center portion of the annular chamber, butinstead runs through the void and is subsequently employed as an upperconnecting member 12 disposed between the chamber and the wellhead. In otherembodiments, a vertical tension receiving member 11 is disposed between thebuoyancy chamber 9 and upper connecting member 12, so that the chamber’sbuoyant forces are transferred to the vertical tension receiving means 11, therebyapplying vertical tension to the drilling or production string extended below thechamber.

In further embodiments, upper connecting member 12 further comprises awell isolation member 13, e.g., one or more bail valves or blowout preventers,used to hait fluid flow in the event that well terminal member 14 is either removedor disabled, for example, during testing and maintenance operations. Those ofordinary skill in the art will appreciate that the précisé types and exact locations ofisolation valves 13 employed in the System are variable and flexible, the only realrequirement being that the valves are capable of allowing or preventing fluid flowfrom the well 1 during periods in which testing or maintenance, or even anemergency safety condition, are présent.

For example, well terminal member 14 can be equipped with a productiontree so that a production hose disposed on a surface vessel can be attached to theSystem and production can commence. Altematively, well terminal member 14can terminate in a blowout preventer, so that the well will not blow out duringdrilling operations. In other embodiments, well terminal member 14 terminâtes ina combined production tree and blowout preventer assembly to facilitate simplifîedwell intervention operations.

DUPLICATA 11

Tuming now to the spécifie, non-limiting embodiments of the inventiondepicted in Figures 2A and 2B, a System and method of establishing a height-variable well terminal member is provided, comprising a lower fluid transport pipe21, an inner well casing 22, an outer well casing 23, and a wellhead 24. In someembodiments, a well isolation member 25 is disposed above the wellhead 24, sothat the well can be closed off or shut in if desired.

In the example embodiment depicted in Figure 2A, well isolation member25 further comprises one or more bail valves that can be adjustably opened orclosed as desired by an operator. A lower connecting member 26 having one ormore interior seals 27 and an interior polished bore 28 houses a fluid transportmember 29 such that the height of fluid transport member 29 is variably adjustablewithin a body portion of lower connecting member 26 in response to verticallifting forces imparted by adjustable buoyancy chamber 30. Various lengths ofpipe defïne the height of an upper connecting member disposed between thebuoyancy chamber 30 and a well terminal member 36. In some embodiments, anupper well isolation member 35, such as a bail valve or a blowout preventer, isdisposed in communication with the upper connecting member between buoyancychamber 30 and well terminal member 36.

In some embodiments, the System is moored to the sea floor using one ormore mooring lines 31 connected to a fïrst vertical tension receiving means 32a,while buoyancy chamber 30 is raised or lowered by either spooling-out or reeling-in lengths of one or more tension lines 37 disposed between a second verticaltension receiving means 32b and a chamber height adjustment means 33. Asadjustable buoyancy chamber 30 rises, vertical tension is applied to verticaltension receiving member 34, which in tum lifts well terminal member 36 uptoward the surface.

As seen in the example embodiment depicted in Figure 2B, the height ofboth the well terminal member 36 and fluid transport member 29 are verticallyadjusted by increasing the length of tension lines 37 using chamber heightadjustment means 33, even as vertical and latéral tension on mooring lines 31 andtension lines 37 remains approximately constant. In one embodiment, vertical

DUPLICATA 12 013023 tension on lower connecting member 26 is also kept approximately constant duringthis process, since fluid transport member 29 is moved vertically within a bodyportion of lower connecting member 26. In another embodiment, a second, loweradjustable buoyancy chamber is added to the System to maintain tension on lower 5 connecting member 26, while the height of the well terminal member is adjusted asdescribed above.

The foregoing spécification is provided for illustrative purposes only, and isnot intended to describe ail possible aspects of the présent invention. Moreover,while the invention has been shown and described in detail with respect to several 10 exemplary embodiments, those of ordinary skill in the pertinent arts will appreciatethat minor changes to the description, and various other modifications, omissionsand additions may also be made without departing from either the spirit or scopethereof.

DUPLICATA 13

Claims (13)

1. 013023 Claims

   1. An offshore exploration and production System, the System comprising: a. a well casing (2) disposed in communication with an offshore well (i); b. an adjustable buoyancy chamber (9); and c. a lower connecting member disposed between said well casing (2)and said adjustable buoyancy chamber (9).
2. 2. The System of claim 1, further comprising: a. one or more adjustable buoyancy chambers (9); or b. a well casing (2) disposed in communication with a hole (3) boredinto an associated sea floor surface; or c. a well isolation member (4) disposed between said adjustablebuoyancy chamber (9) and said lower connecting member (5); i. said well isolation member (4) preferably furthercomprises one or more bail valves or a blowoutpreventer preferably comprising a shear ram; or ii. said lower connecting member (5) preferably furthercomprises a receiving member for receiving anattachment member disposed on said isolation member(4) or an attachment member for attaching said lowerconnecting member (5) to a receiving memberdisposed on said isolation member (4).
3. 3. The System of claim 1, wherein said lower connecting member (5) furthercomprises: a. a riser; or b. a riser pipe; or c. a casing; or DUPLICATA 14 013023 d. a fluid transport member disposed within an interior portion of saidlower connecting member, said fluid transport member is preferablyheight adjustable in response to a buoyant force imparted by saidadjustable buoyancy chamber (9).
4. 4. The System of claim 1, wherein said lower connecting member (5) isdisposed in communication with one or more latéral stabilizers (6); a. said one or more latéral stabilizers (6) preferably further comprisesone or more adjustable latéral stabilizers; or b. said one or more latéral stabilizers (6) is preferably disposed incommunication with one or more tension lines (7); i. said one or more tension lines (7) preferably furthercomprises one or more individually adjustable tensionlines; or ii. said one or more tension lines (7) are preferablydisposed in communication with one or moreanchoring members (8).
5. 5. The system of claim 2, wherein said one or more adjustable buoyancychambers (9) further comprises one or more approximately annularadjustable buoyancy chambers, said lower connecting member (5) ispreferably longitudinally disposed through a void formed in said one ormore approximately annular adjustable buoyancy chambers.
6. 6. The system of claim 2, wherein one or more of said one or more adjustablebuoyancy chambers (9) further comprises a plurality of inner chambers.
7. 7. The system of claim 1, wherein said adjustably buoyancy chamber furthercomprises: a. a fluid ballast preferably comprising a supply of compressed gas; or b. a ballast input valve; duplicata 15 i. said ballast input valve is preferably disposed incommunication with one or more of an umbilical and aremote operated vehicle; or ii. said ballast input valve is preferably disposed incommunication with a pump; or iii. said ballast input valve is preferably disposed incommunication with a compressor; or c. a ballast output valve: i. said ballast input valve is preferably disposed incommunication with one or more of an umbilical and aremote operated vehicle; or ii. said ballast input valve is preferably disposed incommunication with a pump; or iii. said ballast input valve is preferably disposed incommunication with a compressor.
8. 8. The System of claim 1, wherein said adjustable buoyancy chamber is: a. disposed in communication with one or more tension lines (10); i. said one or more tension lines (10) preferably furthercomprises one or more individually adjustable tensionlines; or ii. said one or more tension lines (10) is preferablydisposed in communication with one or moreanchoring members; or b. disposed in communication with a vertical tension receiving member(11), said tension receiving member is preferably disposed incommunication with a tension measuring means preferablycomprising a load cell; or c. submerged in a body of water at a depth of between about 100 feetand about 300 feet; or DUPLICATA 16 013023 d. submerged in a body of water at a depth of less than about 100 feet;or e. submerged in a body of water at a depth of greater than about 300feet; or f. disposed in communication with an upper well isolation member; i. preferably comprising a bail valve; or ii. preferably comprising a blowout preventer preferablycomprising a shear ram; or g. disposed in communication with an upper connecting member (12),said upper connecting member (12) is preferably disposed incommunication with a well terminal member (14) preferablycomprising; i. a production tree; or ii. a blowout pre venter; or iii. a combined production tree and blowout preventerassembly. The system of claim 1, wherein a well terminal member (14) disposedabove said adjustable buoyancy chamber (9) is disposed above a surface ofa body of water. A method of installing and maintaining an offshore exploration andproduction system, the method of comprising the steps of: a. disposing a well casing (2) in communication with an offshore well;and b. disposing a lower connecting member (5) between said well casing(2) and an adjustable buoyancy chamber (9). The method of claim 10, further comprising the steps of: a. disposing one or more adjustable buoyancy chambers (9) in communication with said well casing (2), the method preferably DUPLICATA 17 013023 further comprising cementing said well casing (2) into a hole (3)bored into a sea floor surface; b. disposing a well isolation member between said adjustable buoyancychamber (9) and said lower connecting member (5), preferablyfurther comprising: i. disposing a well isolation member (4) having one ormore bail valves; ii. disposing a well isolation member (4) having ablowout preventer, said disposing a blowout preventerpreferably further comprises disposing a blowoutpreventer having a shear ram; or iii. disposing a well isolation member (4) having anattachment member for attaching said well isolationmember to a receiving member disposed on said lowerconnecting member; or iv. disposing a well isolation member (4) having areceiving member for receiving an attachment memberdisposed on said lower connecting member (5). The method of claim 10, wherein said disposing a lower connectingmember (5) further comprises the steps of: a. disposing a riser; b. disposing a riser pipe; or c. disposing a casing; or d. disposing a fluid transport member housed within an interior portionof said lower connecting member, the method preferably furthercomprising adjusting the length of one or more associated tensionlines so as to variably adjust the height of said fluid transportmember; or DUPLICATA 18 013023 e. disposing a lower connecting member in communication with one ormore latéral stabilizers (6), the method preferably further comprisingthe steps of: i. disposing a lower connecting member (5) incommunication with one or more adjustable latéralstabilizers; or ii. disposing said one or more latéral stabilizers incommunication with one or more tension lines (7), themethod preferably further comprising disposing saidone or more later stabilizers (6) in communication withone or more adjustable tension lines or the methodpreferably further comprising disposing said one ormore tension lines (7) in communication with one ormore anchoring members (8).
9. 13. The method of claim 11, further comprising the steps of: a. disposing one or more approximately annular adjustable buoyancychambers (9), the method preferably further comprising disposingsaid lower connecting member (5) longitudinally through a voidformed in said one or more approximately annular adjustablebuoyancy chambers; or b. disposing one or more adjustable buoyancy chambers (9) having aplurality of inner chambers.
10. 14. The method of claim 10, further comprising disposing an adjustablebuoyancy çhamber (9) having; a. a fluid ballast, said disposing an adjustable buoyancy chamber (9)having a fluid ballast preferably further comprises disposing anadjustable buoyancy chamber (9) having a supply of compressed gas;or b. a fluid input valve, the method preferably further comprising; DUPLICATA 19 013023 i. disposing said fluid input valve in communication withone or more of an umbilical and a remote operatedvehicle; ii. disposing said fluid input valve in communication witha pump; or iii. disposing said fluid input valve in communication witha compressor; or c. a fluid output valve, the method preferably further comprising thesteps of; i. disposing said fluid input valve in communication withone or more of an umbilical and a remote operatedvehicle; ii. disposing said fluid input valve in communication witha pump; or iii. disposing said fluid input valve in communication witha compressor.
11. 15. The method of claim 10, further comprising disposing an adjustablebuoyancy chamber in communication with; a. one or more adjustable tension lines (10), the method preferablyfurther comprising the steps of: i. disposing an adjustable buoyancy chamber (9) incommunication with one or more individuallyadjustable tension lines; or ii. disposing said one or more tension lines (10) incommunication with one or more anchoring members;or b. a tension receiving member (11), the method preferably furthercomprising disposing said tension receiving member (11) incommunication with a tension measuring means, said disposing saidtension receiving member (11) in communication with a tension DUPLICATA 20 013023 measuring means preferably further comprises disposing said tensionreceiving member in communication with a load cell; or c. submersing an adjustable buoyancy chamber in a body of water to adepth of between about 100 feet and about 300 feet; or d. submersing an adjustable buoyancy chamber in a body of water to adepth of less than about 100 feet; or e. submersing an adjustable buoyancy chamber in a body of water to adepth of greater than about 300 feet; or f. disposing a well terminal member (14) above said adjustablebuoyancy chamber (9) in a manner such that said well terminalmember (14) is disposed above a surface of a body of water; or g. disposing an adjustable buoyancy chamber (9) in communicationwith a well isolation member (4), the method preferably furthercomprising: disposing an adjustable buoyancy chamber in communication with a well isolation member (4) having a bail valve; or disposing an adjustable buoyancy chamber in communication with a well isolation member (4) having a blowout preventer, the method preferablyfurther comprising disposing an adjustable buoyancychamber (9) in communication with a blowoutpreventer having a shear ram; or h. disposing an adjustable buoyancy chamber (9) in communicationwith an upper connecting member (12), the method preferablyfurther comprising disposing said upper connecting member (12) incommunication with a well terminal member (14), the methodpreferably further comprising; i. disposing said upper connecting member (12) incommunication with a blowout preventer; or DUPLICATA 21 013023 ii. disposing said upper connecting member (12) incommunication with a production tree; or iii. disposing said upper connecting member (12) incommunication with a combined production tree and 5 blowout preventer assembly;.
12. 16. The use of an offshore exploration and production System, wherein saidSystem comprises: a. a well casing (2) disposed in communication with an offshore well 10 (i); b. an adjustable buoyancy chamber (9); and c. a lower connecting member (5) disposed between said will casing (2)and said adjustable buoyancy chamber (9), the use of said System being for the exploration and production of oil and 15 gas.
13. 17. Oil and gas obtained from a method of installing and maintaining anoffshore exploration and production System, wherein the method comprisesthe steps of: 20 a. disposing a well casing (2) in communication with an offshore well (1) ; and b. disposing a lower connecting member (5) between said well casing (2) and an adjustable buoyancy chamber (9). DUPLICATA 22