Abstract: The invention relates to a centralization and running tool (CTR) in a subsea installation in connection with offshore related oil and gas exploration, where the subsea installation (SCM) is arranged to be placed on the ocean bottom or a drilling template and comprises a pipe-formed body (10), at least partially open at the top and extended, arranged to receive and carry through a drill stem (12) from a drilling rig or a drilling vessel. The centralization and running tool (20) is arranged to surround the drill stem (12) and to be placed in the pipe-formed body (10), and the centralization and running tool (20) comprises, together with the drill stem (12), a rotary packing housing (22) with a number of seals (24,26) that lie against the drill stem (12), and the packing housing (22), in accordance with the movements of the drill stem (12), is arranged for radial movement to take up angular deviations of the drill stem (12).

Abstract: A method for handling a blow-out-preventer on a drilling platform and a drilling platform having a lower pontoon structure; a plurality of columns extending upwards from the lower pontoon structure; an upper deck structure connecting the upper deck structure connecting the upper portions of the columns to each other; a detachable rotary table assembly arranged in a rotary table opening in the upper deck structure; a derrick provided with a lifting arrangement and being arranged on the upper deck structure above the rotary table opening; and a detachable rotary table assembly a spider and a blow-out-preventer.

Abstract: A method for drilling a borehole in a producing subsea wellbore wherein a flexible conduit is connected at one end to a surface vessel and at the other end via a pressurized subsea wellhead to the producing wellbore such that a remotely operated electrical drilling device (RODD) can be deployed down the flexible conduit, the method comprising: directing a RODD to the location for drilling in the wellbore; and drilling a further wellbore section with the RODD; wherein the drilling comprises drilling in underbalanced conditions with respect to the formation; and using fluids produced from the formation to transport the drill cuttings away from the drilling device.

Abstract: The disclosure is drawn to methods of drilling wells utilizing blow out prevention components of differing pressure ratings. In the initial drilling phase, a lower pressure rated blow out prevention component is used. In a subsequent drilling phase where a reservoir of a natural resource is penetrated, a higher pressure rated blow out prevention component is used.

Abstract: At least a portion of a subsea well is drilled casing-while-drilling techniques. A landing shoulder is formed within an outer string of a casing. The outer string of casing is secured to an outer wellhead housing above the landing shoulder and lowered into the wellbore. A casing hanger is attached to an inner string of casing and lowered through the outer string of casing into the wellbore. A drill bit at the at the lower end of the inner string of casing is rotated to deepen the well. The string of inner casing moves downward as the well is being deepened until landing the casing hanger on the load shoulder. A tieback member is attached to an inner wellhead housing and lowered into sealing engagement with the casing hanger. The inner wellhead housing lands in the outer wellhead housing.

Abstract: Methods for deploying a subsea blowout preventer stack system comprising a lower marine riser package, a blowout preventer stack with a first ram blowout preventer, and an additional blowout preventer package releasably coupled to the blowout preventer stack and comprising a second ram blowout preventer. The subsea blowout preventer stack assembly can be deployed by coupling a drilling riser to the lower marine riser package that is releasably connected to the blowout preventer stack. The lower marine riser package and blowout preventer stack are then toward a subsea wellhead and then landed on the additional blowout preventer package that is coupled to the subsea wellhead.

Abstract: An erosion resistant surface using a dense array of elastic whiskers to slow the velocity of erosive particles before impacting with the surface. A carbon nanotube forest is grown on the surface to provide the erosion resistance. In the alternative, a carbon nanotube forest is grown on a flexible substrate that is bonded to the surface.

Abstract: A system and method is described for use and return of drilling fluid/cuttings from a well, which is drilled on the ocean floor, in connection with offshore related oil production and gas production, where, from a drilling rig or drilling vessel (10), a drill stem (12) runs down into the bore hole and where a blowout preventer (BOP) is placed on said well, without mounting a riser between the rig or the vessel and said blowout preventer. A sealing and pressure-regulating device (16) is arranged on the blowout preventer (14) arranged to regulate the level of the drilling fluid, and thus the outlet pressure of the drilling fluid in said sealing and pressure-regulating device, and a pump module (18) is set up at a suitable distance adjacent said sealing and pressure-regulating device, where the pump module is arranged to pump said drilling fluid up to the ocean surface via an external return pipe.

Abstract: A method for removing soils, particles or fluids from the seabed or from great sea depths, includes positioning a platform or a vessel above an offshore location, lowering a riser from the vessel or platform to the seabed or great depth, the riser being vented to the atmosphere, sucking soils, particles or fluids with inflow of fluid into the riser and removing them from the riser via an outlet in the riser, the outlet being at a level well below the water surface, by use of a pumping system with a flow return conduit running to a selected location, while keeping the level of the fluid in the riser at a level between the outlet and the surface corresponding with a pressure in the lower end of the riser substantially lower than the sea water pressure at the end of the riser.

Abstract: An anti-fouling system for offshore drilling structures which injects metallic ions into seawater pumping systems. An ion generator may be positioned at various positions including the strainer basket of one or more of the seawater pumps or at various positions in the system. As well, ion generators may be skid mounted and/or otherwise centrally located and connected by controllable valves to various treated water injection points, whereby the flow rates are determined and ion concentrations are maintained at desired levels throughout the system, regardless of different pumping rates.

Abstract: What is provided is a method and apparatus wherein a swivel can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve or housing can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve or housing of the swivel.

Abstract: A riserless mud recovery system including a mud return line secured by an anchor is disclosed. Some system embodiments for drilling a well bore in an offshore location having a water surface and a subsea formation include an offshore structure positioned on a platform at a water surface, a drill string for forming the well bore suspended from the offshore structure, a drilling fluid source on the platform for supplying drilling fluid through the drill string, a suction module for collecting the drilling fluid emerging from the well bore, a return pipe coupled to the suction module, a pump for receiving the drilling fluid from the suction module and pumping the drilling fluid through the return pipe to a location at the water surface, and an anchor for securing the return pipe, where the anchor is coupled to the return pipe and the subsea formation.

Abstract: Methods for deploying a subsea blowout preventer stack system comprising a lower marine riser package, a blowout preventer stack with a first ram blowout preventer, and an additional blowout preventer package releasably coupled to the blowout preventer stack and comprising a second ram blowout preventer. The subsea blowout preventer stack assembly can be deployed by coupling a drilling riser to the lower marine riser package that is releasably connected to the blowout preventer stack. The lower marine riser package and blowout preventer stack are then toward a subsea wellhead and then landed on the additional blowout preventer package that is coupled to the subsea wellhead.

Abstract: Systems and methods for drilling a well bore in a subsea formation from an offshore structure positioned on a water surface with a drill string that is suspended from the structure and includes a bottom hole assembly adapted to form a top hole portion of the well bore. A drilling fluid source on the offshore structure supplies drilling fluid through the drill string to the bottom hole assembly where the drilling fluid exits from the bottom hole assembly during drilling and returns up the well bore. A suction module is disposed at the sea floor and collects the drilling fluid emerging from the well bore. A pump module is disposed on a return line, which is in fluid communication with the suction module, at a position below the water surface and above the sea floor. The pump module is operable to receive drilling fluid from the suction module and pump the drilling fluid through the return pipe to the same offshore structure or a different offshore structure.

Abstract: What is provided is a method and apparatus wherein a swivel can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve or housing can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve or housing of the swivel.

Abstract: What is provided is a method and apparatus wherein a swivel can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve or housing can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve or housing of the swivel.

Abstract: A method and apparatus for drilling subsea wells is provided. A subsea shut off device including ball gripping mechanisms is latched to a template at surface. Drilled in casing can be suspended from the device at any position using the gripping mechanism so that the device is run to the sea floor on the casing string. The casing string is drilled into place and converted into a riser. This is all done on a single trip to speed up the operation and reduce the risk. The casing string is captured and sealed within the subsea shut-off device after installing and spacing out a surface BOP. For the event when emergency disconnection is required, dual shear rams in the device cut the casing and seal in the well. The system then allows a conventional subsea reconnection of the riser.

Abstract: An apparatus for storing tubulars on a floating semi-submersible drilling or production vessel. The apparatus comprises a storage device for storing tubulars in a submerged position, essentially below a splash zone. The storage device is generally open to the surroundings so that the tubulars are externally exposed to surrounding water. It is also described an apparatus for transporting tubulars between a storage and a derrick on an offshore drilling and/or production platform having a platform deck. The apparatus is situated below the platform deck and is adapted for movement under the platform deck. A method for disassembling a pipe string is also described.

Abstract: An anchor handling/tug/supply (AHTS) vessel is employed to engage conductor casings with the seafloor. The conductor casings initially penetrate the seafloor to a first depth under their own weight. The conductor casings may optimally be further engaged with the seafloor to a second depth by the application of suction to the interiors thereof or by the use of a drop hammer. The conductor casings are driven to grade by a hydraulic pile driving hammer deployed from the deck of the AHTS vessel the previously deployed conductor casings to grade before being recovered to the deck of the AHTS vessel.

Abstract: A method for intervention in an underwater production well, in which the well head (1) of the production well is located on the seabed (2), and wherein a drilling rig (26), which comprises at least a robotized drill floor (32), is placed at the well head (1), after which necessary intervention operations are carried out in a remote-controlled manner by means of the drilling rig (26).

Abstract: An improved method and/or apparatus for completing a wellbore is provided. In one embodiment, a method of lining a pre-drilled wellbore is provided. The method includes the act of providing a casing assembly, the casing assembly including a string of casing; and a retractable joint comprising an inner tubular and an outer tubular. The method further includes the acts of running the casing assembly into the pre-drilled wellbore and actuating the retractable joint, thereby reducing the length of the casing assembly through movement between the inner and outer tubulars.

Abstract: A subsea drilling system comprises a pressurized drilling capsule that is sealed against the subsea environment and houses equipment for manipulating a drillstring that extends through an opening in the drilling capsule to the exterior of the capsule. A drilling fluid handling assembly is contained within the drilling capsule that communicates drilling fluid through the drillstring and returns the drilling fluid to the water's surface via a drilling fluid conduit. A seafloor unit engages the seafloor and the drilling capsule to position the drilling capsule relative to the seafloor, and includes an opening for passing the drillstring into the seafloor. A pressurized transport unit is movable between the drilling capsule and a support vessel at or near the water's surface for delivering personnel and supplies to the drilling capsule. A method of drilling using the subsea drilling system is disclosed.

Abstract: A riser assembly includes a rotating control housing connected between an upper portion and a lower portion of a riser assembly, and a packing element rotatable with respect to the rotating control housing, wherein the packing element is configured to isolate an annulus of the lower portion from the upper portion when a drillstring is engaged through the packing element, and wherein the packing element is configured to be retrieved and replaced through the upper portion.

Abstract: A method of reducing drilling fluid pressure during subsea drilling, where drilling fluid is pumped down into a borehole and then flows back to a drilling rig via the lined and/or unlined sections of the borehole and a liner, wherein the drilling fluid pressure is controlled by pumping drilling fluid out of the liner at the seabed, and where the liner annulus above the drilling fluid is filled with a riser fluid having a density different from that of the drilling fluid.

Abstract: A drilling rig device (1) situated on the seabed (11), where the drilling rig (1) is sealingly enclosed against the surroundings, wherein the drilling rig (1) is liquid-filled and provided with a separator (16) arranged to separate material (17) from the liquid.

Abstract: A method and apparatus for conducting simultaneous drilling and production are provided. The apparatus can include a ship shape floating vessel, wherein the ship shape floating vessel includes at least two drilling derricks, at least two drilling modules, and at least one production module, all situated on the upper surface of the ship shape floating vessel. The drilling modules are adapted for conducting drilling operations; the production module is adapted for conducting production operations. The apparatus can include at least two marine risers, wherein each marine riser depends from a drilling or production module toward a hydrocarbon bearing zone or sea floor and is adapted for conducting drilling and/or production operations; at least one production turret located on the lower surface of the ship shape floating vessel; and at least one production riser, wherein the production riser depends from the production turret, extends toward the sea floor, and is adapted for conducting production operations.

Abstract: A drilling placed on the seabed and arranged for drilling of oil and gas wells is remote controlled from a light drilling vessel (2) through pipes and signal cables (3). The main structure of the drilling rig is made up of two cylindrical structures (1 and 10), in connection with which there is provided a number of cylindrical silos (8) for storing drill pipe magazines (23). A complete drilling module (17) can be lowered and retrieved through hatchways (11) at the top of the first cylindrical structure 10 The drilling rig is anchored to a foundation frame (7) by hydraulic legs (9). A cylindrical skirt (34) encloses the BOP (33) to prevent pollution of the environment.

Abstract: An apparatus for deflecting a tubular string preferably comprising at least one side nozzle near the lower end of a first tubular string. The nozzle permits passage of a fluid therethrough from the first tubular string bore and deflects the first tubular string in a substantially horizontal direction. A second tubular string may be lowered over the deflected first tubular string. The second tubular string and the first tubular string are preferably lowered into the sea floor for maintaining their deflection. A method for deflecting a first tubular string and securing the first tubular string in the deflected state preferably comprises lowering the first tubular string axially so that the lower end of the first tubular string is near the sea floor. Preferably, a fluid, such as seawater, is propelled down through the bore of the first tubular string and through at least one side nozzle near the lower end of the first tubular, wherein the fluid moving through the side nozzle deflects the first tubular string.

Abstract: An underwater drilling rig (1) in modular form, which can be simply assembled underwater and in which standard tubulars and tubular assemblies are stored in a novel arrangement within containers (6) and can be added to, and removed from, the string in the well bore, whilst there is continuous circulation of drilling fluid and also continuous segregation of drilling fluid from the seawater.

Abstract: The invention relates to a method for subsea hydrocarbon recovery in which a wellbore is drilled using a base installed on the seabed, said base comprising a drilling guide, in which at least one pipeline is to be connected to a network for storage and/or processing operations. The method according to the invention includes the following steps: preparing a pre-assembly of a base and one or more pipelines, lowering and positioning the pre-assembly on the seabed, drilling the wellbore through the base, placing a connecting element between the wellbore and the pipeline.

Abstract: A method for removing soils, particles or fluids from the seabed or from great sea depths, includes positioning a platform or a vessel above an offshore location, lowering a riser from the vessel or platform to the seabed or great depth, the riser being vented to the atmosphere, sucking soils, particles or fluids with inflow of fluid into the riser and removing them from the riser via an outlet in the riser, the outlet being at a level well below the water surface, by use of a pumping system with a flow return conduit running to a selected location, while keeping the level of the fluid in the riser at a level between the outlet and the surface corresponding with a pressure in the lower end of the riser substantially lower than the sea water pressure at the end of the riser.

Abstract: A process for extracting hydrocarbon gases from marine sediment hydrates. In one embodiment, the process includes drilling from a sea floor into a hydrate rich subsea sediment to form at least one opening therein. Electrical heaters are inserted into the opening or openings. The hydrate rich subsea sediment is heated with the electrical heaters in order to release hydrocarbon gas therefrom. The released hydrocarbon gas is collected in an overhead receiver. The hydrocarbon gas forms hydrates again when moving through the cold sea water and inside the overhead receiver. The overhead receiver is raised to a sea depth where pressure and temperature permit the hydrates to dissociate and to release the hydrocarbon gas. The hydrocarbon gas is then gathered from the top of the overhead receiver.

Abstract: An arrangement and a method to control and regulate the bottom hole pressure in a well during subsea drilling at deep waters: The method involves adjustment of a liquid/air interface level in a drilling riser. The arrangement comprises a drilling riser with an outlet at a depth below the water surface. The outlet is connected to a subsea pumping system with a flow return conduit back to a drilling vessel. The intention of the system is to transport the drilling fluid and the formation particles to the surface on the drilling unit prior to setting structural pipe on the seabed and when drilling at least one hole section after the first surface structural casing have been set. The apparatus is used in order to drill all surface hole sections with the riser installed in order to avoid “pump & dump” procedures and to recover all mud and chemicals.

Abstract: An arrangement and method for controlling and regulating bottom hole pressure in a well during subsea drilling in deep water involves adjustment of a liquid/gas interface level in a high pressure drilling riser up or down to change the slope and offset of the pressure gradient in the well. The arrangement may include a surface BOP and gas bleeding outlet at the upper end of the drilling riser, a lower BOP with a by-pass line, and an outlet at a depth below the water surface that is connected to a pumping system with a flow return conduit running back to a drilling vessel or platform.

Abstract: An apparatus for deflecting a tubular string preferably comprising at least one side nozzle near the lower end of a first tubular string. The nozzle permits passage of a fluid therethrough from the first tubular string bore and deflects the first tubular string in a substantially horizontal direction. A second tubular string may be lowered over the deflected first tubular string. The second tubular string and the first tubular string are preferably lowered into the sea floor for maintaining their deflection. A method for deflecting a first tubular string and securing the first tubular string in the deflected state preferably comprises lowering the first tubular string axially so that the lower end of the first tubular string is near the sea floor. Preferably, a fluid, such as seawater, is propelled down through the bore of the first tubular string and through at least one side nozzle near the lower end of the first tubular, wherein the fluid moving through the side nozzle deflects the first tubular string.

Abstract: An offshore well drilling assembly includes a drilling facility or support platform for location at sea. A drilling platform connects to the support platform so the drilling platform is cantilevered from the support platform. The drilling platform extends from the support platform, for positioning over a subsea well. The well drilling assembly includes a staging platform for use in loading and unloading of wellhead equipment. The staging platform is mounted to the drilling platform. The staging platform moves along a side of the drilling platform in directions toward and away from the support platform to a distance over the sea. A method of conveying wellhead equipment uses the staging platform for conveying wellhead equipment between the support platform and a distance over the sea by moving the staging platform along the drilling platform.

Abstract: A pile based braced caisson structural support device includes a number of legs. These legs are configured in a teepee type configuration such that the footprint of the base is larger than the footprint of the opposing end. This structural support can be used as a base for an offshore drilling platform in that the support reduces the lateral forces on the support caused by wave action.

Abstract: Method for drilling and lining a well wherein at least one liner (1, 2, 32) with a larger external diameter than the substantial part of a drilling riser (10) is pre-installed at a point below the substantial part of the drilling riser (10). A bore hole section (21) is drilled after the drilling riser (10) has been installed, the bore hole section having a larger diameter than the at least one pre-installed liner (1, 2, 32). The at least one pre-installed liner (1, 2, 32) is subsequently lowered into the bore hole section (21, 22). A drilling and liner system for implementing the method is also described.

Abstract: What is provided is a method and apparatus which can be detachably connected to an annular blowout preventer thereby separating the drilling fluid or mud into upper and lower sections and allowing the fluid to be displaced in two stages, such as while the drill string is being rotated and/or reciprocated. In one embodiment the sleeve can be rotatably and sealably connected to a mandrel. The swivel can be incorporated into a drill or well string and enabling string sections both above and below the sleeve to be rotated in relation to the sleeve. In one embodiment the drill or well string does not move in a longitudinal direction relative to the swivel. In one embodiment, the drill or well string does move longitudinally relative to the sleeve of the swivel.

Abstract: A method for drilling riserless that includes providing a drilling fluid to a drilling assembly for drilling a borehole on a seafloor, the drilling assembly comprising a drill string and a bottomhole assembly, and wherein the drilling fluid includes a brine, and a non-hydratable clay, wherein the drilling fluid is substantially free of hydrating clays, and flowing the drilling fluid and cuttings through an annulus formed by the drill string and the borehole into sea water is disclosed.

Abstract: A pipeline installation and maintenance method and system is disclosed in which a number of interconnectible platform modules are assembled into drilling platforms from which a segmented pipeline route is flexibly installed. Using modified push/pull rigs to carry out a transverse drilling process established between platforms, successive portions of the pipeline are installed such that equipment used to create completed segments is moved down line and re-used in subsequent drilling and installation stages. Further segments of the line are similarly constructed, using one or more of the modified directional drilling techniques and transverse reaming processes disclosed herein. Ultimately, a long series of adjacent pipeline segments are installed along a desired pipeline route, while only minimal and temporary disturbance is caused to associated ground surfaces during installation and maintenance operations.

Abstract: A drilling system for drilling subsea wellbores includes a tubing-conveyed drill bit that passes through a subsea wellhead. Surface supplied drilling fluid flows through the tubing, discharges at the drill bit, returns to the wellhead through a wellbore annulus, and flows to the surface via a riser extending from the wellhead. A flow restriction device positioned in the riser restricts the flow of the returning fluid while an active fluid device controllably discharges fluid from a location below to just above the flow restriction device in the riser, thereby controlling bottomhole pressure and equivalent circulating density (“ECD”). Alternatively, the fluid is discharged into a separate return line thereby providing dual gradient drilling while controlling bottomhole pressure and ECD. A controller controls the energy and thus the speed of the pump in response to downhole measurement(s) to maintain the ECD at a predetermined value or within a predetermined range.

Abstract: Subsea wells are drilled and completed with an offshore floating platform in a manner that allows simultaneous work on more than one well. A first well is drilled and casing. Then a tubing hanger is run through a drilling riser and landed in the wellhead housing. Then, with the same floating platform, the drilling riser is disconnected and moved to a second well. While performing operations on the second well, the operator lowers a production tree from the floating platform on a lift line, and connects it to the first wellhead housing. An ROV assisted subsea plug removal tool is used for plug removal and setting operations required through the production tree.

Abstract: A riser assembly for offshore drilling has an inner conduit suspended within an outer riser. A seal assembly seals an annular space between the inner conduit and the riser at the lower end of the inner conduit. The seal assembly has a pressure area that is independent of the inner conduit, so that any forces acting on the assembly due to pressure in the annulus below the seal assembly pass through the assembly to the riser and not to the inner conduit.

Abstract: An offshore riserless drilling system drills a subsea borehole from a platform and through a cased borehole. The system comprises a lightweight drill string suspending a bottomhole assembly and extending from the platform downwardly through a depth of water into the cased borehole; a first limiter limiting the range of motion of the drill string adjacent the platform; and a second limiter limiting the range of motion of the drill string adjacent the cased borehole. The preferred methods include lowering a bottomhole assembly suspended on a lightweight drill string from a platform through a depth of water; limiting the bend radius of the drill string adjacent the platform; guiding the bottomhole assembly into a cased borehole; limiting the bend radius of the drill string adjacent the cased borehole; maintaining the bottomhole assembly in the cased borehole, and drilling the subsea borehole.

Abstract: The invention relates to a vessel (1) provided with a deck (2) and with a device (3) for removing and/or installing a sub-structure (4) of a drilling or production platform, wherein said device comprises a supporting structure (5) which is capable of tilting movement in a direction transversely to an edge (6) of the deck (2), hoisting means (7) connected to said supporting structure for hoisting said sub-structure, and supporting means for supporting said sub-structure mainly during tilting movement of said supporting structure, wherein said supporting means are provided separately from the supporting structure and capable of tilting movement with respect to the edge of the deck.

Abstract: A system for controlling drilling mud density at a location either at the seabed (or just above the seabed) or alternatively below the seabed of wells in offshore and land-based drilling applications is disclosed. The present invention combines a base fluid of lesser/greater density than the drilling fluid required at the drill bit to drill the well to produce a combination return mud in the riser. By combining the appropriate quantities of drilling mud with a light fluid, a riser mud density at or near the density of seawater may be achieved to facilitate transporting the return mud to the surface. Alternatively, by injecting the appropriate quantities of heavy fluid into a light return mud, the column of return mud may be sufficiently weighted to protect the wellhead. At the surface, the combination return mud is passed through a treatment system to cleanse the mud of drill cuttings and to separate the drilling fluid from the base fluid.

Abstract: The present invention generally relates to methods for drilling a subsea wellbore and landing a casing mandrel in a subsea wellhead. In one aspect, a method of drilling a subsea wellbore with casing is provided. The method includes placing a string of casing with a drill bit at the lower end thereof in a riser system and urging the string of casing axially downward. The method further includes reducing the axial length of the string of casing to land a wellbore component in a subsea wellhead. In this manner, the wellbore is formed and lined with the string of casing in a single run. In another aspect, a method of forming and lining a subsea wellbore is provided. In yet another aspect, a method of landing a casing mandrel in a casing hanger disposed in a subsea wellhead is provided.

Abstract: Improved method for the drilling of the initial phase of deep water oil wells with an underwater well head consisting in the positioning and cementation of the conductor pipe and anchorage casing by means of a single drilling phase. A tapered hole (with a double diameter) is drilled using a drill string consisting of a motor driven pilot bit and a reaming bit.

Abstract: A method of drilling and completing an underwater well entails installing conductor casing from a floating vessel into a seabed; drilling a bore through the conductor casing to a defined depth in the seabed; and installing surface casing through the conductor casing. A high pressure wellhead and mudline suspension system engages the surface casing and are disposed on the first end. The lower stress joint is connected to a lower saver sub that connects to the casing riser's lower end. The casing riser on an upper end is connected to an upper saver sub that engages a upper stress joint. The method ends by connecting the upper stress joint to a surface wellhead in fluid communication with a surface BOP; and connecting the surface BOP and the surface wellhead to a tensioning system on the floating vessel; and using a telescoping joint.