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: 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 base 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 base 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: Exemplary embodiments include a method and a device for temporary storage of solid particles such as drill cuttings from a hole section for surface casing in a wellbore. In certain embodiments, the device having at least one collecting device placed on the seabed near a template over the mouth of a well. When the receptacle element in the collecting device is to be emptied, the collecting device is brought up to and on board a vessel on the surface of the sea.

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: A guide device suitable for use in an offshore drilling installation having at least one drilling riser extending from a floating support to the guide device on the seabed. The guide device includes a guide pipe in a buried position, wherein the guide pipe has a front end resting horizontally on the seabed, a curved intermediate portion buried in the subsoil of the seabed at a radius of curvature preferably being greater than 500 m, and an inclined substantially linear rear portion at the rear end of the guide pipe buried in the subsoil of the seabed at a given angle of inclination lying in the range 50° to 60°.

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.

Abstract: A power supply assembly, which is placed subsea and is connected to an umbilical from a platform, supplies electrical power to subsea equipment. The power supply assembly supplies power during drilling operations to a pump for pumping drilling fluid from the sea floor to the sea surface. During production operations, the power supply assembly provides power to a booster pump to pump the well fluid away from the subsea well for collection. The subsea power supply assembly optionally also provides power to electrically charged portions of subsea separators that remove water from the oil in the well fluid. The booster pump the pumps the oil from the separator away from the subsea wellhead for collection.

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 cased. 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. Seabed separation is configured upstream of a production choke valve.

Abstract: A system and method 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 deep water and ultra deep water applications. A base fluid of lesser density than the drilling mud required at the wellhead is used to produce a diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, a diluted riser mud density at or near the density of seawater may be achieved. The present invention also includes a wellhead injection device for injecting the base fluid into the rising drilling mud. The riser charging lines are used to carry the low density base fluid to the injection device for injection into the return mud. At the surface, the diluted return mud is passed through a treatment system to cleanse the mud of drill cuttings and to separate the heavier drilling mud from the lighter base fluid.

Abstract: A floating rig or structure for drilling in the floor of an ocean using a rotatable tubular includes a seal housing having a rotatable seal connected above a portion of a marine riser fixed to the floor of the ocean. The seal rotating with the rotating tubular allows the riser and seal housing to maintain a predetermined pressure in the system that is desirable in underbalanced drilling, gas-liquid mud systems and pressurized mud handling systems. The seal is contemplated to be either an active seal or a passive seal. A flexible conduit or hose is used to compensate for relative movement of the seal housing and the floating structure because the floating structure moves independent of the seal housing. A method for use of the system is also disclosed.

Abstract: A sub-sea mud pump system includes a plurality of pump units, and each pumping unit includes a plurality of pumping elements. Each pumping element includes a pressure vessel with a first and a second chamber, a separating member between the first and second chambers, a measurement device adapted to measure the volume of at least one of the first and second chambers, a hydraulic inlet control valve and a hydraulic outlet control valve coupled to the first chamber, a mud suction valve and a mud discharge valve coupled to the second chamber. The first chamber is hydraulically coupled to receive and discharge a hydraulic fluid, and the second chamber is hydraulically coupled to receive and discharge a drilling fluid. The separating member is adapted to move within its the pressure vessel in response to a pressure differential between the first and second chambers. The pump system also includes a hydraulic control unit adapted to control the plurality of pump units.

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: An end piece arrangement is mounted on an end of a pipe sleeve to close off the annular passage between the pipe sleeve and drill stem and to divert an upward flow of sludge, cuttings and gas into a conduit system to transport the flow to a remote location. In one embodiemnt, the arrangement is a self-contained unit that houses seal rings to seal against the drill stem. In another embodiment, the arrangement includes separate components; i.e. a housing mounted on the pipe sleeve to divert the upward flow and a seal unit mounted on the drill stem and rotatably mounted in the housing.

Abstract: A method and apparatus 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 deep water and ultra deep water applications combines a base fluid of lesser density than the mud required at the wellhead to produce a diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, a riser mud density at or near the density of seawater may be achieved. A wellhead injection device for attachment to the wellhead is used for injecting the base fluid into the rising drilling mud at a location below the seabed. The riser charging lines are used to carry the low density base fluid to the injection device for injection into the drilling mud below the seabed. The cuttings are brought to the surface with the diluted mud and separated in the usual manner. The diluted mud is then passed through a centrifuge system to separate the heavier drilling mud from the lighter base fluid.

Abstract: A subsea well intervention vessel including a dynamically positionable tanker and direct well intervention equipment mounted on a deck of the tanker. The direct well intervention equipment is mounted on a superstructure above the main deck of the tanker and includes equipment for underbalanced non-rotating drilling and hydrocarbon liquid separation. The liquid separation equipment is coupled to storage tanks of the tanker so as to receive separated hydrocarbon liquids for storage purposes.

Abstract: An automated riser recoil control system (10) including a plurality of riser tensioners (20), a vessel heave measurement system (210) and a control processor (70) with each tensioner (20) having a piston travel indicator (27) which signals the processor (70) and a method of operation is disclosed.

Abstract: A boring device for producing a bore with a casing tube has a linkage, a boring tool, which can be fixed to the lower end of the linkage, a mounting frame for mounting on the casing tube, a drive and a connecting device, which is used for producing a rotary connection between the casing tube and the mounting frame. The linkage is hollow and has a first and a second flushing line. In the vicinity of the upper end of the link-age are provided a first connection for the supply of a fluid to the first flushing line and a second connection for removing the borings via the second flushing line. A boring method introduced the casing tube into the soil prior to an excavation.

Abstract: A floating rig or structure for drilling in the floor of an ocean using a rotatable tubular includes a seal housing having a rotatable seal connected above a portion of a marine riser fixed to the floor of the ocean. The seal rotating with the rotating tubular allows the riser and seal housing to maintain a predetermined pressure in the system that is desirable in underbalanced drilling, gas-liquid mud systems and pressurized mud handling systems. The seal is contemplated to be either an active seal or a passive seal. A flexible conduit or hose is used to compensate for relative movement of the seal housing and the floating structure because the floating structure moves independent of the seal housing. A method for use of the system is also disclosed.

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. Seabed separation is configured upstream of a production choke valve.

Abstract: An outer wellhead housing has an external locator member initially oriented in a desired direction. An inner wellhead housing lands in the outer wellhead housing. A BOP orientation spool with an external orientation member and an internal orientation member lands on the inner wellhead housing and orients via the external locator member. A tubing hanger with an orientation member and associated tubing hanger running tool with another orientation member lower through the BOP orientation spool and orient as they land in the inner wellhead housing. A production tree with an orientation member on a lower end lands on the inner wellhead housing. The orientation member of the production tree engages the orientation member of the tubing hanger to rotate the tree to a desired orientation.

Abstract: The invention is a multiple lift hoist system for a drilling vessel and use on land made of a mast with a top side and a base connected to a drilling vessel, wherein the mast has a hollow construction for supporting a first and second hoisting device at the top side, a lift system with a first hoisting device located in a first firing line that manipulates a first drill string and s second hoisting device located in a second firing line that manipulates a second drill string both hoisting devices move the strings in the longitudinal direction of the mast, and a plurality of cables and winches disposed in the hollow construction to manipulate the position of the first and second hoisting devices relative to the mast so the first and second firing lines are accessible from the outside of the mast.

Abstract: A closed system drill string compensator having a hydraulic fluid accumulator, at least one air pressure vessel, and a piston and a piston rod slidably engaged within a cylinder. The drill string compensator provides tensioning force for supporting a drill string and permits the drilling vessel to remain connected to the drill string during ocean level changes caused by wave action or ocean heave. In one embodiment, the accumulator surrounds the cylinder and at least one air pressure vessel is radially disposed around the accumulator and the cylinder. In another embodiment, the accumulator surrounds the cylinder and includes two ports, one port for permitting fluid communication between the cylinder and the accumulator and a second port for permitting fluid communication between the accumulator and the air pressure vessel, the first port including a shut-off valve disposed therein. Methods of compensating a drill string are also disclosed.

Abstract: A system for drilling wells includes a plurality of platform modules, which are interconnected to one another on site to form a unitary platform structure. The interconnected platform modules are elevated above a surface on plurality of legs coupled to at least some of the platform modules. The elevated interconnected platform modules support drilling and auxiliary equipment. The system is well adapted for use in arctic, inaccessible, shallow water or environmentally sensitive locations.

Abstract: Methods and apparatus are disclosed for the open hole drilling of a borehole from an offshore platform and through a cased borehole at the seafloor. The drilling assembly includes a guide assembly extending from the platform to the seafloor and having a lower end extending into the cased borehole; and a bottomhole assembly disposed on a lightweight drill string extending through the guide assembly for drilling the borehole. The guide assembly is a pipe string and preferably includes a casing and a riser attached to the casing. The lightweight drill string may be a jointed pipe, a metal coiled tubing, or preferably a composite coiled tubing. The bottomhole assembly includes a formation displacement member adapted to drill a borehole having a diameter greater than the diameter of the guide assembly.

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: An underwater well system in which an initially vertical drilling riser conduit is fixed by a template at the seabed in a non-vertical orientation. Drilling is carried out through wellhead in the template which also includes a valve tree allowing the production fluid to be brought to the surface along a line separate from the drilling riser conduit. The template may be a junction template allowing several wells to be drilled from a single template, or allowing the template to be connected by one or more drilling conduits to further templates such that a wide area of the seabed can be covered for a single drilling riser conduit.

Abstract: A method of preparing and operating a subsea well (23), comprising the steps of: locating a drill-through subsea tree (24) on a subsea wellhead; sealingly connecting a high pressure drilling riser (22) between the tree and a drilling platform at the sea surface; mounting a blow out preventer (16) at the top of the riser (22); drilling the well through the drilling riser and the subsea tree; and establishing a production connection between the tree (24) and a production collection facility at the sea surface through a production riser (52) which is separate from the drilling riser (22).

Abstract: An apparatus and method for offshore riserless drilling are disclosed. The preferred embodiments comprise a system for riserless drilling of a subsea borehole from a platform and through a cased borehole, the system comprising 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: 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 base 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 base 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: A subsea return fluid recovery system for recovering drilling fluid and cuttings (“return fluid”) from a subsea wellbore in one embodiment includes a hub at the opening of the subsea wellbore that directs fluid into a transport device. In one embodiment, the hub includes a stand pipe that forms a return fluid column, the hydrostatic pressure of which causes return fluid to flow into the transport device rather than up the stand pipe. One or more buoyant members attached to the transport device convey the transport device toward the surface. A preferred recovery method includes collecting return fluid at the seabed, passively transporting the collected fluid to the surface, and processing the collected fluid at a local (offshore) or land based treatment facility. The retrieval and processing of the return fluid is done outside the critical path of the drilling activities at an offshore platform.

Abstract: A suction substructure (2) is for the setting of one or more conductor casing strings (14) in connection with drilling of at least one underwater well, preferably a petroleum well. Use of the suction substructure (2) renders possible the installation of conductor casing by means of known piling technique and by means of a suitable surface vessel, e.g. a suitable boat. The suction substructure (2) consists of a substructure body, which is joined in a pressure sealing manner, and which is shaped with a downwards open end part (8), which is set some way down in the seabed sediments (22). Thereupon water is pumped out of the suction substructure (2), which causes a negative pressure in the suction substructure (2), and where the suction substructure (2) thereby is pressed further down into the seabed sediments (2).

Abstract: A method and associated equipment are disclosed which allow drilling at least a portion of a well and subsequently cementing casing in a single trip. The method is particularly suited for deep-water offshore operations where the drill string can be run through a section of casing leaving a bit and an under-reamer extending out below. The casing is equipped with ports through which cement can be pumped as well as an external casing packer to prevent the uncured cement in the annulus from U-tubing. Several casing sections can be run in during drilling and cemented succession using the one trip method.

Abstract: A method 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 deep water and ultra deep water applications are disclosed. The mud recirculation system may be used in conventional drill bit drilling operations or with drilling with casing operations. The present invention combines a base fluid of lesser density than the mud required at the wellhead to produce a diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, a riser mud density at or near the density of seawater may be achieved. The present invention also includes a wellhead injection device for attachment to the wellhead and for injecting the base fluid into the rising drilling mud at a location below the seabed. The riser charging lines are used to carry the low-density base fluid to the injection device for injection into the drilling mud below the seabed.

Abstract: A riser pipe construction for a drilling connection from a drilling vessel to a valve previously provided on a sea floor comprises a riser pipe through which drilling means can be passed by means of which an oil well can be drilled as well as pressure pipes extending along the riser pipe to operate the valve, and floating elements disposed around the riser pipe and the pressure pipes to limit the load on the drilling vessel. The riser pipe and the pressure pipes are built up from modules capable of being coupled together, the floating elements are formed by steel tubular chambers closed so as to be gastight, disposed around the relevant modules and firmly connected thereto. The invention also relates to a riser pipe module.

Abstract: A method for controlling subsea drilling operations including, in at least certain aspects, controlling the subsea drilling operations with a control system having three subsea pod containers of a control system, each with apparatus for controlling the subsea drilling operations, the system also having activation apparatus for activating a chosen one of the subsea pod containers and maintenance apparatus for maintaining the two subsea pod containers other than the chosen one in a standby mode providing triple redundancy of control of the subsea drilling operations.

Abstract: A floating platform system supports one or more decks (14) above the water surface for accommodating equipment to process oil, gas and water recovered from a subsea hydrocarbon formation. The platform is secured to the seabed by one or more tendoms (17). A central column (12) of the platform includes a moonpool (19) extending axially through the central column (12). The moonpool (19) is open at the lower and upper ends thereof. Riser lateral restraint members (32) are supported within the moonpool (19) for laterally restraining risers (16) disposed in the moonpool (19) and minimizing riser spacing and riser deflection.

Abstract: A method and apparatus for controlling drilling mud density at or near the seabed of wells in deep water and ultra deep-water applications combines a base fluid of lesser density than the mud required at the wellhead to produce a diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, a riser mud density at or near the density of seawater may be achieved. No additional hardware is required below the surface. The riser charging lines are used to inject the low-density base fluid at or near the BOP stack on the seabed. The cuttings are brought to the surface with the diluted mud and separated in the usual manner. The diluted mud is then passed through a centrifuge system to separate the heavier drilling mud from the lighter base fluid.

Abstract: A horizontal spool tree wellhead system 10 utilizes a casing 18, 19 installed in a well bore and a wellhead housing 20 at the upper end of the casing. A spool 23 of the horizontal tree 22 is connected to the upper end of the wellhead housing, and includes at least one radially extending side port. The BOP 28 is also installed at the upper end of the housing with a bore aligned with the wellhead housing bore. After drilling the well, the casing string 19 carrying a casing hanger 42 may be lowered through the bores of the BOP, the spool tree, and the wellhead housing and into the well. An orientation/isolation sleeve 60 may be installed in a predetermined rotational orientation with the spool tree. A tubing hanger 70 having a side port is landed onto the orientation sleeve and is automatically oriented to align the tubing hanger side port with the spool side port.

Abstract: An underwater well system in which an initially vertical drilling riser conduit (5A) is fixed by a template (7,13,15) at the seabed (6) in a non-vertical orientation. Drilling is carried out through wellhead (30) in the template which also includes a valve tree (28) allowing the production fluid to be brought to the surface along a line separate from the drilling riser conduit. The template may be a junction template allowing several wells to be drilled from a single template, or allowing the template to be connected by one or more drilling conduits (12,14) to further templates such that a wide area of the seabed can be covered for a single drilling riser conduit.

Abstract: An underwater well system in which an initially vertical drilling riser conduit (5A) is fixed by a template at the seabed in a non-vertical orientation. Drilling is carried out through wellhead in the template which also includes a valve tree allowing the production fluid to be brought to the surface along a line separate from the drilling riser conduit. The template may be a junction template allowing several wells to be drilled from a single template, or allowing the template to be connected by one or more drilling conduits to further templates such that a wide area of the seabed can be covered for a single drilling riser conduit.

Abstract: A method of conducting operations to an offshore field from multiple separated drill centers using a floating vessel having a turret-mounted mooring element and a workstation separate from the mooring element in which the vessel is moored at a central mooring element location and operations are sequentially carried out at separate drill centers associated with the mooring element location by allowing the vessel to weathervane to a heading associated with a subsequent drill center once operations have been completed at a first drill center.

Abstract: A process and an apparatus for sinking drill holes, in particular exploration and extraction drill holes, with a drill pipe, which at its end facing the floor to be mined is provided with a guide point fixed in the longitudinal direction of the drill pipe and a drill head with at least one cutting element. The drill head can be moved in the longitudinal direction of the drill pipe between a top position, in which the guide point projects beyond the at least one cutting element, and a bottom position in which the at least one cutting element is positioned at the same height as the end of the guide point or projects beyond same in the operating direction. When the drill head is in the top position, the drill pipe is moved in the direction of the drill hole to be produced until the guide point by cooperating with the floor fixes it in position. Then the drill head is moved into its bottom position in order to produce the drill hole.

Abstract: A semisubmersible multipurpose unit (MPU) having a deck, a multipurpose tower secured to the deck, supports, pontoons connected to the supports with each pontoon adapted for ballast transfer, at least two hawsers connected to the MPU for connecting the MPU to an object at sea having a mooring system, a hawser guidance system to direct each hawser to the object at sea, a crane secured to the deck of a semisubmersible MPU, and at least an 6-point mooring system, wherein the combination of the semisubmersible MPU, hawsers and 6-point mooring system create a global equilibrium between the mooring system of an object at sea and the at least 6-point mooring system and the hawsers have both an elasticity sufficient to accommodate the wave frequency between the object at sea and the MPU and a stiffness adequate to synchronize the average and low frequency movements during a 10-year storm.

Abstract: A method of drilling an offshore underwater well comprising the steps of installing a riser conduit so that it is substantially vertically supported at a production deck. The riser conduit deviates progressively further from the vertical with increasing sea depth, so that its end can be anchored at the seabed by a skid either at an oblique angle so that drilling into the seabed can be carried out at the oblique angle, or horizontally, so that the riser conduit can extend some considerable distance across the seabed before drilling is carried out.

Abstract: An improvement in a side element of a drilling template for wells at sea for extracting hydrocarbons, wherein the side element is connected to a central section of the drilling template and projects horizontally out therefrom. The side element is arranged to carry equipment of various types. According to the invention the side element comprises a coupling section for releasable connection with a coupling section of the equipment.

Abstract: A surface vessel is anchored almost geostationarily by a turret rotatable relative to the vessel about a vertical axis and having mooring cables extending to the seabed. A well is drilled from a drilling section in the vessel at a distance from the axis of rotation of the turret. The drilling is performed using a drill string through a riser extending from the seabed to the drilling section, which riser can be broken and shut off between the seabed and the vessel. By manipulating (hauling in and slackening) the mooring cables, the vessel is held in position so that the derrick is kept almost geostationary relative to the well during drilling operations. The system includes a surface vessel, a turret rotatable relative to the vessel about a vertical axis and which can be anchored to the seabed by a plurality of mooring cables, and a riser extending from the seabed to the vessel through which the well can be drilled with a drill string from a derrick in a drilling section on board the vessel.

Abstract: An apparatus and method are provided for controlling hydrostatic pressure in drilling fluid in a subsea well. A main pump forces drilling fluid down the drill pipe, out of the end of the drill pipe, and upward in an annulus surrounding the pipe. A rotating drilling head is attached to a wellhead assembly at the sea floor. The drilling head has an inner body rotatably carried in an outer body landed in a bore of a housing. An energizable gripper in a bore of the inner body grips an outer surface of the drill pipe. The drilling head diverts the drilling fluid into a lateral passage in the sidewall of the housing. An auxiliary pump forces seawater through a venturi into a conduit, creating a lower pressure to draw drilling fluid into the conduit to be carried back to the surface vessel. Pressure and flow rate measurements are sent to a control system that modulates the speed of each pump to control hydrostatic pressure.

Abstract: A drilling riser for use at great sea depths for drilling of wells in the seabed using a drill string, with the drilling riser arranged to be connected between a wellhead at the seabed and a vessel, and arranged for use with a drilling fluid with sufficiently high density to balance the fluid pressure from the geological formations, with a sensor arranged to detect the level of the drilling fluid's level in the drilling riser, and a return riser pipe with an adjustable return riser pump. The return riser pipe extends up to the vessel, from an outlet on the riser, from a depth which is substantially below the sea surface, and at the same time at a height substantially above the seabed.

Abstract: A dual riser assembly for use with an offshore multi-activity drilling assembly to conduct drilling operations from a deck above the surface of a body of water into the bed of the body of water utilizing two risers, a first and a second, which extend from a location above the surface of a body of water to a common location adjacent to the bed of the body of water. Each riser terminates, at a distal end, into a dual riser assembly, allowing for selective open internal communication between each of the two risers and a single wellhole.