Abstract: A method of installing or removing a subsea wellhead assembly is provided. The method comprising providing a suction anchor that in use acts as a subsea well foundation, wherein the suction anchor comprises an outer suction skirt; and an inner member, wherein the inner member comprises a high pressure wellhead housing; and installing or removing the suction anchor together with the high pressure wellhead housing on or from a seabed.

Abstract: Disclosed embodiments include a suction pile vent plug having a cylindrically-shaped body having a sealing element, a plurality of coupling features, and a handle connected to the cylindrically-shaped body. The sealing element is configured to form a watertight seal with walls of a suction pile vent into which the vent plug is installed. The plurality of coupling features are configured to engage with corresponding coupling features of the suction pile vent. The movable handle is configured to be moved into one or more locked configurations. Disclosed embodiments further include a suction pile vent having a hollow cylindrically-shaped body having coupling features. The coupling features are configured to engage with corresponding coupling features of a suction pile vent plug to thereby mechanically couple the suction pile vent plug to the suction pile vent. Disclosed embodiments further include a fluidic port that fluidically couples a suction pile to a removable fluidic coupling.

Abstract: A shaft sinking apparatus for sinking a concrete shaft in a pit includes at least one first steel beam disposed to span the concrete shaft, two second steel beams disposed on the first steel beam, at least two tightening units configured to force the second steel beams into abutment against the first steel beam, and at least two jack members provided among the first and second steel beams. When each of the jack members is actuated, the first steel beam is driven by the jack members to move downwardly away from the second steel beams to thereby force a lower surrounding edge of the concrete shaft to sink into a bottom surface of the pit.

Abstract: The present invention relates to a ground stabilization system and a support and a method of stabilizing ground, more particularly to soil below a building or foundation of a structure. A system for soil consolidation is disclosed. It comprises: a delivery channel (10) that is closed at one end and adapted to receive a grout or resinous liquid (99). The delivery channel (10) has a plurality of apertures (20) that are selectively openable and closable, ideally by way of a concentric member (40) in order to permit filler or resinous material (99) to exude/egress from the delivery channel (10) into selected regions of surrounding soil at desired times, in a controllable manner, so as to create a stabilized volume of soil bonded to the delivery channel.

Abstract: A trash container for holding trash which may include an inflatable frame a front flexible wall connected to the inflatable frame, a back flexible wall connected to the inflatable frame and opposed to the front flexible wall, a pair of side flexible walls connected to the inflatable frame and connected to the front flexible wall and the back flexible wall.

Abstract: A partially floating supported marine platform for offshore wind turbines, bridges and offshore buildings includes horizontal beams and hollow, cylindrically-shaped and vertically disposed buoyancy tubes interconnected to form the marine platform. A cone matching technique may be employed to fast fix the buoyancy tubes onto concrete beds in the seabed that are prepared in advance. Piling support to enhance the foundation of the platform may be used, to be installed within the buoyancy tube interior using small diameter piles that are driven down into the concrete beds and socketed into bedrock. The buoyancy tubes are capped at top and bottom ends, providing buoyancy to the platform at temporary and/or at permanent states. All manual operations for installing piling support are performed in dry conditions, thus expensive piling vessels are not required, thereby providing an economical and safe technology for the development of the ocean.

Abstract: A jack-up rig while in open water operates with the hull jacked up out of the water. However, in the event of ice conditions, the legs are held in place by cans embedded in the sea floor to resist lateral movement of the rig and the hull is lowered into the water into an ice defensive configuration. The hull is specifically shaped with an ice-bending surface to bend and break up ice that comes in contact with the hull while in the ice defensive configuration.

Abstract: An apparatus and method for securing subsea devices to a seabed are provided. The apparatus generally includes a mud can housing that defines a internal space that can be evacuated to drive the housing into the seabed and secured it thereto. At least one receiver is connected to the housing. Each receiver is configured to receive a subsea device so that each subsea device in each receiver is secured to the seabed in a vertical orientation when the mud can housing is secured to the seabed.

Abstract: Disclosed is a method for installing a support column under the water. The method includes: (step 1) installing a plurality of steel pipes to stand up at regular distance on the floor of a place with water; (step 2) inserting a drilling rod into each of the steel pipes, to excavate a bedrock with a bit attached to an end portion of the drilling rod and fixing the drilling rod on the bedrock; and (step 3) placing and curing an accelerating agent containing concrete or mortar inside each of the steel pipes. According to the disclosed method, the solar generating apparatus mounted on a floating plate can be more securely supported by firmly installing the support column.

Abstract: The present invention provides a skirted foundation that can be used in a jack-up rig for providing enhanced bearing capacity. The skirted foundation comprises a spudcan footing having an upper part and a base, wherein the upper part and the base are coupled at their peripherals to form an outer edge, wherein both the upper part and the base have a flat or conical configuration, and wherein the upper part supports one leg of a jack-up rig, and the base has a flat bottom or downward slope, and a skirt having an upper end being integrally coupled to the spudcan footing and downwardly projected to encircle the base and a lower end for penetrating seabed, wherein the skirt comprises a plurality of circumferential openings adjacent to the base of the spudcan footing and located within the top half of the skirt height.

Abstract: The invention relates to a guide frame for guiding a cutting apparatus within a pipe incorporated into the ground, having a framework body which can be inserted into the pipe and comprises a guide, along which the cutting apparatus can be displaced, a bracing means for tensioning and fixing the framework body in the pipe, and an adjusting means, with which the cutting apparatus can be adjusted within the pipe in a transverse direction relative to the pipe axis. The invention further relates to a method for anchoring a pipe in the ground.

Abstract: Embodiments of gravity base structures are disclosed that comprise first and second elongated base sections separated by an open region and configured to support the on-bottom weight of the structure on a seabed, and an upper section positioned above the open region and configured to extend at least partially above the water surface to support topside structures. Some embodiments further comprise first and second inclined sections coupling the base sections to the upper section. Some embodiments comprise a skirt structure below the base sections for facilitating engagement with the seabed. Some embodiments comprise selectively fillable internal fluid chambers to facilitate raising and lowering the structure in a sea and relocating the structure.

Abstract: The invention relates to an underwater work assembly and to a method for anchoring the underwater work assembly in a bed of a lake, sea or river. The work assembly comprises a service platform which can be lowered and a plurality of supporting feet which are mounted so that they can be adjusted on the service platform for positioning on the lake, sea or river bed and can be moved in and out relative to the service platform by means of an actuating cylinder. In order to improve anchoring it is provided that at least one supporting foot is mounted rotationally relative to the service platform and that a rotary drive facing the supporting foot is provided, with which the supporting foot is driven in rotation for screwing into the lake, sea or river bed.

Abstract: A method or corresponding apparatus in an example embodiment of the present invention relates to penetrating a particulate substrate using a compact, low-energy, reversible, and dynamic device for burrowing through particulate substrates. In one preferred embodiment, the apparatus includes at least one vessel and a displacement module coupled with the vessel. The actuation of the displacement module fluidizes the particulate substrate proximate to the vessel and thereby reduces resistance of the particulate substrate to movement of the vessel and causes further penetration of the apparatus through the particulate substrate. The example embodiment utilizes volume contraction and localized fluidizing to move through substrates.

Abstract: The present invention describes an offshore foundation system (10,10a,10b) that is operable for preloading after self-weight installation on a seabed without relying on additional or external ballasts. The foundation system (10,10a,10b) is also operable for extraction by reversing the process of preload operation. In one embodiment, the foundation system (10) comprises a reaction base (20) and suction compartment (60). In another, the foundation system (10a,10b) comprises a plurality of units of reaction base (20) and suction compartments (60), with the units being connected by bridging structures (21). In yet another, the foundation system comprises a reaction base (20) and a plurality of suction compartments (60). A closed-top of the suction compartment (60) projects above the reaction base (20) so that, in use, there is a gap h between a top of a soil plug inside a suction compartment (60) and its closed-top.

Abstract: Method of installing a bucket foundation structure comprising one, two, three or more skirts, into soils in a controlled manner. The method comprises two stages: a first stage being a design phase and the second stage being an installation phase. In the first stage, design parameters are determined relating to the loads on the finished foundation structure; soil profile on the location of installation; allowable installation tolerances, which parameters are used to estimate the minimum diameter and length of the skirts of the bucket. The bucket size is used to simulate load situations and penetration into foundation soil, in order to predict necessary penetration force, required suction inside the bucket and critical suction pressures, which penetration force, required suction, and critical suction pressures are used as input for a control system in the second stage, in which second stage the pa-rameters determined in the first stage are used in order to control the installation of the bucket.

Abstract: A subsea suction pile crane system comprises a suction pile and a crane mounted on the suction pile. The crane comprises a rotatable mounting surface, a winch, and a boom having a proximal section attached to the rotatable mounting surface such that the boom can pivot with respect to the mounting surface, and a distal section opposite the proximal section. In embodiments, a plurality of suction piles may be sed. The crane system is typically hydraulically operated. A preferred embodiment of the invention may further comprise a remotely operated vehicle comprising a hydraulic power supply operatively coupled to the crane, and a manipulator arm mounted on the distal section of the boom and operatively coupled to the hydraulic power supply.

Abstract: A system includes a body portion having rear portion having a fluid intake port and a nose portion having a fluid discharge port. The body portion contains an omni-directional vibratory device, a pump, a fluid conduit that is coupled to the pump and the fluid discharge port, and a power source that is electrically connected to the vibratory device and the pump. The body portion may also contain control circuitry and two end caps rigidly fixed therein, wherein the fluid conduit passes through each end cap. The vibratory device and the pump may be activated by a sensor such as a hydrostatic pressure sensor, an accelerometer, or an altimeter. The body portion may also contain communications circuitry that remotely controls the vibratory device and the pump. The body portion is configured to house a payload such as a sensor system, a battery pack, or a ballast for anchoring.

Abstract: A cutoff device with a liquid bag includes a framed housing that supports a cover having a cutoff wall. The cutoff wall is opened at a lower end thereof with a liquid bag attached along the opened lower end of the cutoff wall. The housing includes telescopic columns, upper support frames coupled to the upper ends of the telescopic columns, and a lower support frame coupled to the lower ends of the telescopic columns. The upper end of the liquid bag may be fastened to the opened lower end of the cutoff wall using a zipper. The liquid bag contains liquid, such as water, therein, with a heavy substance, such as sand, soil and powdered or granulated metal, added to the liquid.

Abstract: A subsea suction pile crane system comprises a suction pile and a crane mounted on the suction pile. The crane comprises a rotatable mounting surface, a winch, and a boom having a proximal section attached to the rotatable mounting surface such that the boom can pivot with respect to the mounting surface, and a distal section opposite the proximal section. In embodiments, a plurality of suction piles may be used. The crane system is typically hydraulically operated. A preferred embodiment of the invention may further comprise a remotely operated vehicle comprising a hydraulic power supply operatively coupled to the crane, and a manipulator arm mounted on the distal section of the boom and operatively coupled to the hydraulic power supply.

Abstract: A method of removing a pipe, such as a caisson, from a body of water, after the platform has been removed which includes the steps of a high pressure head having a lifting padeye is secured to the upper end of the caisson; the caisson is then flooded with water; pressure is applied to the water column, so that a sufficient hydraulic force against the surface of the water bottom within the caisson to force the caisson to move upward; if the caisson moves upward to the level of the top of a crane, the caisson is cut off above the water line and the cut portion is removed; the process is repeated on the remaining portion of the caisson in the water, until the entire caisson is finally removed from the water. This process could also be used in removal of pilings from multi-leg jackets.

Abstract: A mudmat foundation for supporting an item of subsea equipment on the sea floor comprises a mudmat on which the item of subsea equipment may be supported and a plurality of legs which are pivotably connected to and depend downwardly from the mudmat. The legs are free to pivot outwardly relative to the mudmat upon insertion of the legs into the sea floor to thereby increase the load bearing capacity of the mudmat.

Abstract: There is disclosed improved mooring apparatus and method suitable for use with large offshore vessels. To avoid deploying an anchor with a full weight of mooring chain, they are deployed separately. An anchor, such as a suction anchor (1), is fitted with a short chain (C1) with one end permanently connected (6) thereto and its free end temporarily placed in a chain locator (8), which is positioned so as to be accessible after deployment of the anchor to the seabed, minimising the potential for seabed material to cause disruption. The anchor with its short chain is deployed to the seabed and at some stage the free end of a mooring chain (C2) is lowered to and accurately guided (100) into the chain locator, such that both free ends align. A pin (101) is inserted by an ROV to interconnect the two chains, after which the combined mooring chain (C) is tensioned, withdrawing it from the chain locator.

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: 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 apparatus for deployment of mooring systems for buoyant marine structures such as mobile offshore drilling units (MODU's) and for connecting the same to the mooring lines thereof. An anchor handling vessel carries one or more anchors each having a deployment connection and a mooring connection and individually moves each anchor over its stem roller and deploys it to the sea bottom for installation. A handling line is disconnected by ROV from the deployment connection and is moved from the deployment connection to the mooring connection so as to become the main mooring line. Syntactic buoys are then mounted on the main mooring line for elevating it above the sea bottom for recovery. When MODU stationing is desired the anchor handling vessel then recovers the surface buoy and connects to the rig mooring line using a short section of mooring chain. A J-chaser stopper device is then installed in the mooring string and is connected to the mooring line of the MODU by a short section of chain.

Abstract: A method and apparatus for deployment of mooring systems for buoyant marine structure such as mobile offshore drilling units (MODU's) and for connecting the same to the mooring lines thereof. An anchor handling vessel carries one or more anchors each having a deployment connection and a mooring connection and individually moves each anchor over its stern roller and deploys it to the sea bottom for installation. A handling line is disconnected by ROV from the deployment connection and is moved from the deployment connection to the mooring connection so as to become the main mooring line. Syntactic buoys are then mounted on the main mooring line for elevating it above the sea bottom for recovery. When MODU stationing is desired the anchor handling vessel then recovers the surface buoy and connects to the rig mooring line using a short section of mooring chain. A J-chaser stopper device is then installed in the mooring string and is connected to the mooring line of the MODU by a short section of chain.

Abstract: The invention relates to a method for installing anchors on the bottom of the sea. Wires (4) and a suction anchor (2) are attached to a frame (1). Through the centre of the frame's vertical axle a mounting device (6) for an anchor holder (7) is placed. The frame (1) works as a driving ramp for different shaped anchor holders and anchors (5, 15, 20). With the mounting device (6) the anchor penetrates the bottom of the sea at a certain position. A remote operated vehicle (ROV) and/or a hydraulic motor and pump gives a hydraulic torque for boring screwing, pressing and stamping effects. A helical screw-anochor is used for rotary screwing into the bottom of the sea (3). The span and the gradient are varied given to geological data for achieving holding forces. After use the anchor is released with a releasing mechanism (13, 14) and is left on the bottom of the sea.

Abstract: A mudmat assembly for supporting a portion of a subsea offshore platform on a soft, unconsolidated underwater surface is described. The mudmat assembly includes at least one fiberglass plank, a mudline framing plane that is attached to and provides support for the fiberglass plank, and integral framing beams attached to and providing support for the fiberglass plank. The fiberglass mudmat assembly of the present invention requires minimal cathodic protection, has a high flexural strength, and is lighter than conventional mudmats.

Abstract: A device for creating a localized water jet within a body of water allows for the displacement of material from the floor of the body of water. The device includes two powered screws within a jet pipe. The screws are arranged coaxially and their direction of rotation, pitch, and speed of rotation are arranged such that the torque produced by one of the screws tends to counteract the torque produced by the other, allowing for improved control of the device.

Abstract: A mudmat in which the bearing plates of the mudmat are fabricated of a non-corrosive, man-made structural material such as plastic. The plates, formed of such a material, are lightweight, easily fabricated and generally less expensive than the prior art plates and their associated support structure. In one preferred embodiment, the plates are formed of extruded polyvinyl chloride (PVC) or a fiber reinforced composite such as thermoset resin reinforced with glass fibers (GRP). The individual plates are supported by standard frame members. The PVC or GRP plates are of such a size, shape and weight that they can easily be transported to, assembled and attached to the offshore jacket at the jacket fabrication site. Being formed of such materials, the plates are corrosion resistant, eliminating the need for cathodic protection.

Abstract: A method to provide a stoichiometric mixture of water, lime and cement for making an in-site piling. Water to supplement existing ground water is supplied by an augur as it drills into the ground so that a substantially uniform concentration of water exists for the full depth. Then the augur, while turning, returns to the surface while it injects and stirs into the wet soil the stoichiometric amounts of lime and cement.

Abstract: Apparatus such as a cofferdam 1, intended to be partially buried in ground beneath water comprises a hollow structural framework. The framework includes chambers 12 which have inlets 29 via which pressurized water can be supplied to the chambers. Each chamber 12 communicates with a plurality of nozzles 36 from which jets of the pressurized fluid issue to break up the ground below. Each chamber 12 also communicates with a plurality of water operated pumps 25 via inlets 24. The pumps 25 are operated by the pressurized water to draw or suck water-suspended solids from below through the pumps via the inlets 32 and discharged from the pumps via outlets 28.

Abstract: A subsea abandoned wellhead protection system which may be installed underwater without the need for underwater assistance from divers or the like, the system allowing full site preparation and installation from the surface. The present invention teaches a new and unique system for the lowering and centering of the shelter over the wellhead, as well as a new system for the preparation of the installation site, including the removal of debris from the site and excavation of the ground surface area about the abandoned wellhead via a remote, fluid actuated, integrated excavation system.

Abstract: A cantilevered jack-up rig having a support for supporting the free ends of the rig's cantilever beams when said beams are extended over a platform to be serviced by the rig, thereby maximizing the lateral reach of the rig and increasing the load capacity at the maximized reach. The support is positioned between the top of the platform and the bottoms of the extended cantilever beams. The top of the support is provided with a motion block to facilitate lateral and rotational motion of the extended cantilever beams relative to the support.

Abstract: A structure that is floatable on a ocean surface and that is fixable relative to an ocean bottom. The structure includes an array of floatable, submersible caissons and a floatable box girder capable of supporting a modular superstructure. The box girder is floated to a position on the ocean surface above the submerged array of caissons. The array of caissons is then raised to engage and connect with the box girder. The caissons may also be secured to the ocean bottom.

Abstract: A support device on the sea-bed for legs of a self-elevating oil-rig platform are characterized in that it comprises an individual and independent shoe (3) intended to be fixed on the lower end of the leg (2) and fitted with a detachable and adjustable locking means (20), for fitting rigidly on the said lower end of the leg (2) .

Abstract: Method and apparatus for lowering a heavy hollow column into hard soil and rock at the bottom of a body of water which column has a downwardly widening outer surface and a sharp lower edge. By means of plurality of suction nozzles erosive water flows are generated alongside and below the lower edge which sharp lower edge due to the erosive effect of the water flows and the local tensions generated in the soil by the weight of the column disintegrates the soil.

Abstract: An artificial submerged structure and underwater wellhead protection system for sheltering a submerged, permanently or temporarily abandoned wellhead utilizing a sloped structure configured to prevent nets, anchors, and the like from entangling or otherwise damaging the wellhead. The exemplary embodiment of the present invention is in the form of a pyramidal structure which is designed to rest on the sea floor, enveloping the wellhead. The present invention is prefabricated and designed to be assembled on the vessel above the well site before installation on the sea floor. The wellhead protector is designed to protect the wellhead from any anchoring, trawling or related activities, as well as protecting any nets or the like from becoming damaged due to entanglement with the wellhead. Anchoring means is also disclosed for providing a firm placement of the shelter relative the wellhead in those cases where large anchors, oyster dredges, trawl boards and the like might tend to knock over the structure.

Abstract: The invention is related to a submarine vehicle for the deep ocean research. This vehicle is composed of a penetrator (1) and of a support structure (2 to 7). The vehicle descends by gravity due to a ballast disposed in the lower part (11) of the penetrator. Apart from this ballast, the vehicle can be recovered due to a discoupling of the ballast by an explosive bolt (13). After discoupling, the float clusters (8) located in the upper part of said support structure supply the mounting thrust necessary for transferring the vehicle up to the ocean surface. If this thrust is insufficient, a pyrotechnical device (15) can be provided, which inflates a bag and thus creates an additional thrust directed to the upside.The invention is particularly useful in the investigation at the deep ocean sea-bottom.

Abstract: A wellhead apparatus and a method for positioning the apparatus on the ocean floor in combination with means for sinking it into the ocean floor. The wellhead apparatus is equipped with a venturi suction device and a central opening for receiving a well conductor pipe. The apparatus provides a well base structure that is highly stable, capable of taking high vertical and lateral loads, and can be controlled during installation to be either truly plumb or positioned at a predetermined angle relative to the vertical.

Abstract: A method for removal of large metal objects such as offshore platforms that may be embedded in or substantially immobile and lying on the seabed. The environment should be dislodged from at least a portion of the supporting pile embedded below the mud line. A liquified gas is injected into the environment in contact with the pile to embrittle the pile. Upon embrittlement, the pile is fragmented. Thereafter, the pile may be removed from the seabed.A cannister for use in the above method has a body shaped to conform to the pile or object to be fragmented and contains liquified gas to be sprayed from nozzles by a pressurized gas to chill the object to be fragmented upon embrittlement. A support is positioned on the body for raising and lowering the cannister within the pile.

Abstract: The invention relates to a method and apparatus for increasing the capacity of a tubular driven pile. A refrigeration unit is lowered into the pile and grouted in place above a cement plug. The area between the refrigeration unit and the plug is filled with a secondary refrigerant. Seawater fills the pile above the refrigeration unit and is used for refrigeration unit cooling. The refrigeration unit cools the brine until the soil surrounding the pile is frozen. The adfreeze strength of the frozen soil and the pile increase the pullout resistance of the pile. Further, the end-bearing capacity of the pile is increased as a result of the large frozen mass surrounding the pile.

Abstract: A light weight pile having increased load bearing capacity for being embed in the ocean floor. Two cones are welded together at their base. An opening of about one third the diameter of the base is made in the apex of each of the cones to provide an opening for a hollow pile to pass through. The double cone is attached to the pile so that it can be water jetted into the ocean floor.

Abstract: A device and method for severing the piles, grout and structural sleeves of vertical marine structures, from the inside of the structural member or the outside of the structural member. The device will sever the pile, grout or sleeve without jamming even though the weight of the marine structure is bearing down on the pile, grout or sleeve. The device is first lowered into the pile at the desired elevation and further locked onto the wall of the pile. Once the device is locked onto the pile, the cutter is lowered and proceeds to cut into the pile, grout and sleeve. When a sufficient section of the pile, grout or sleeve has been cut, spacers with barbs are forced into the slot formed by the cutter blade and are held in place by the barbs. After the spacers are in place, the remainder of the pile is severed with the cutter blade and a continuity check is made of the pile.

Abstract: A universal footing and jetting system for marine platforms and structures comprises a spud-can forming an enlarged footing base to distribute loadings over a large soil area and thus increase bearing load capacity while reducing required pile penetration depth, a conical spike means for supporting the structural weight on and indenting into coral or rock type seafloors, and an internal jetting system to fluidize the soil around the footing for ease in penetration of the footing into the seafloor and the removal of the footing therefrom.

Abstract: A method and apparatus for installing marine silos to a desired depth into the seabed such that the interior of the silos is void of seabed material to a desired depth. A submergable silo positioning template operatively supports a silo and excavation modules during surface transportation to the intended site and is capable while floating and submerged of raising and lowering the silo relative to the template and maintaining vertical alignment of the silo. The submergable excavating module incorporates apparatus for loosening and removing sea bed material within the silo thus permitting the silo and excavating module to descend to a desired depth in the seabed. The template and the excavating module are separated from the silo after silo installation and are reused for other silo installations. During silo installation the influence of hydrostatically stimulated force may be employed to assist forcible insertion of the silo into the soil of the seabed.

Abstract: A method for installing an offshore jack-up structure having a buoyant platform to be towed and a plurality of legs, the method comprising the steps of:(a) providing a pair of ultrasonic transmitter-receivers on a longitudinal and horizontal center line of the platform,(b) providing of ultrasonic transmitters on a longitudinal and horizontal center line of a target structure to which the rig is approached; and(c) receiving signals transmitted from the ultrasonic transmitters of the target structure by the ultrasonic transmitter-receivers of the platform to determine a relative distance between the rig and the target structure.

Abstract: A wellhead apparatus and a method for positioning the apparatus on the ocean floor. The wellhead apparatus is equipped with a removable pump and a central opening for receiving a well conductor pipe. The apparatus provides a well base structure that is highly stable, capable of taking high vertical and lateral loads, and can be controlled during installation to be either truly plumb or positioned at a predetermined angle relative to the vertical.

Abstract: A marine operations structure for use in arctic seas having steel/concrete composite ice walls positioned to permit multi-year ice ridges to be broken up with lower vertical forces imposed on the structure than heretofore possible. The structure provides for simultaneous contacting and fracturing of both surface ice floe and multi-year ice ridges by proportioning of the ratio of the annular dimension of a first sloped surface to the radius of the structure within the range of about from 0.15 to 0.30. The structure is fabricated by modular construction techniques which lowers total construction costs. The structure is in the form of a sixteen-sided polygonal sloped walled marine structure with internal ballast tanks for providing gravity founding of the structure on the sea floor. Modular drilling equipment is provided for and supported by the structure for use through two rectangular shaped moon pools extending vertical throughout the central core of the structure.