Abstract: A spar-buoy type boring device including a main pipe and a central pipe installed in the main pipe. The main pipe, which has a service deck at the top and a float near the top so that the float stays underneath the water, is anchored at the bottom to a sinker which is placed on the seabed, and the central pipe with the bottom end opening in the sea is used for guiding boring equipments to the seabed and collecting samples from the seabed.

Abstract: A system for transferring fluids from a piping system which is firmly connected with a ship's hull (2) to a turning device (5), and vice versa, in which the turning device is rotatably connected with said hull. The turning device has a through hole (7) coaxially with its axis of rotation, through which a drill string, a rigid riser, or the like may be run by the aid of a derrick (16). Furthermore, turning device is arranged for anchoring to the sea floor and connection with at least one flexible riser being connected with respective devices which are firmly connected with the sea floor, and with hoses which are connected with the piping system in the hull.

Abstract: A method is described for conducting well operations from a floating platform that may be moved to various locations above subterranean formations. Marine risers that have been previously connected to the platform flex sufficiently to allow this movement. The mobility of the platform allows well drilling, completion, producing, and workover activities to be conducted simultaneously through the risers attached to the platform. The mobility of the platform also allows new wells to be drilled at more preferable locations than those that would be available from a fixed bottom supported well template.

Abstract: An independent modular structure for providing lateral support for the well conductors of an offshore well platform and a method for designing and using such structure are disclosed. The modular structure can be inserted into a void in the jacket of the well platform. The vertical spacing between adjacent support points on the modular structure is determined by the lateral support requirements of the well conductors. Accordingly, the design of the platform jacket may be optimized without consideration of the lateral support requirements of the well conductors.

Abstract: A subsea drilling drive pipe apparatus for drilling offshore wells from a floating vessel into the ocean floor. An elongated drilling drive pipe including a plurality of locking pads which are circumferentially positioned about the drive pipe periphery. A foundation structure is removably engageable with the elongated drive pipe by one or more locking pins which detachably engage the drive pipe thereby permitting the assembled members to be lowered as a unit to the ocean floor in contemplation of a subsea well drilling operation.

Abstract: A floating/tensioned production system for use in deepwater drilling and production operations generally combining a relatively small tension leg platform with a semisubmersible platform. The semisubmersible platform is provided with a working deck supported above the water surface so that an air gap exists between the working deck and the water surface. The tension leg platform provides a heave-restrained production deck for near-surface wellhead equipment. The production deck is supported above the drill site but beneath the water surface by buoyancy members and held in place by one or more tethers. Most other drilling and production equipment is located on the semisubmersible working deck. A caisson, surrounding the production deck, is used to provide a substantially dry working area. In one embodiment, the caisson is retractably attached to the production deck.

Abstract: An improved wellhead casing hanger for suspension of successive casing strings with particularly small annular spacings having an adapter sleeve of double wall construction which is utilized with a load bearing shoulder on the inside of the inner member for receiving a conventional expanding type hanger, with the annulus between the inner and outer walls providing an improved fluid return path without restricting the bore of the sleeve, packoff for sealing the annulus at the appropriate time and an installation tool.

Abstract: There are disclosed several embodiments of a marine riser having means for disrupting smooth flow of seawater along its length of the riser and thus damping vertical oscillation of the riser when its lower end is released from a subsea wellhead.

Abstract: A process for oil well drilling and completing operations in deep water which allows an oil well drilled in deep water to start producing, the operations being conducted from a dynamically placed vessel, comprising: providing a permanent guide base (9) on the sea bottom containing a high pressure housing (13) having an upper free end (15) adapted to receive safety, drilling, and production (completion) equipment, the upper free end of the high pressure housing being covered by a protective cover (17) having an external conical part (18), the permanent guide base (9) also having attached thereto, by means of a releasing device, a releasable guide-funnel (10) which covers and protects the upper free end of the high pressure housing during drilling of the well but which prevents the production equipment from being installed because of its size and shape; withdrawing the releasable guide-funnel, after drilling operations are finished, by means of a remote control vehicle which activates the releasing device, thus

Abstract: The present invention relates to an improved caisson structure which is adapted to support a production platform above the water and has its base on bottom and has a foot print or base which will pass through the drilling slot of a jackup rig. The caisson structure includes a large diameter caisson supported in a base structure including at least three base columns through which piling is placed and bracing extending between the columns and the caisson, a platform supported at the upper end of the caisson with production tubing and its casing extending upward through the caisson, and where desired, filled with concrete surrounding the casing within the caisson. The improved caisson structure can be used to surround and support an existing conductor pipe extending from a subsea wellhead to the surface or to surround a wellhead at the surface and the conductor which extends to such wellhead from a subsea well bore.

Abstract: A system for determining kelly-to-riser position on floating drilling platforms is presented. The system removes (e.g. filters) uncompensated heave from surface sensor measurements so that bit depth can be accurately calculated. During operation, surface sensors on the drilling platform measure heave compensator action and kelly movements. Each heave sensor reading is then added to a kelly sensor reading in order to obtain a value termed kelly-to-riser. Each kelly-to-riser value is fed (inputted) into the system of the present invention and a filtered reading is returned for use in calculating bit depth and rate of penetration (ROP). The filtering system is termed a linear extrapolative filter (LEF). The LEF generates filtered readings by performing a linear regression on measurements taken over its pre-specified filter interval. It then predicts the current kelly-to-riser position from the resultant trend line.

Abstract: A leveling wafer for a subsea hydrocarbon production platform having two wedge portions which can be rotated in relation to each other to vary the degree of taper. The wafer supports a machinery supporting template having a wedge shaped key projecting downwardly therefrom to engage an opening in the top of the wafer to ensure rotational (azimuth) orientation of the template.

Abstract: A floating drilling platform having dual work stations is disclosed for performing deep sea drilling and/or hydrocarbon production operations. The structure of the platform is designed to accommodate replaceable modules which facilitate the installation and removal of either a drilling derrick or production equipment. Thus, during the drilling phase of a reservoir's development, the platform may be outfitted with dual drilling derricks while at later times the platform may be outfitted with a drilling derrick and a full production facility. Various expedients are available to permit the equipment of one work station to be used in conjunction with the equipment of one other. Simultaneous management of dual conductors is enabled by a dual riser management system which models in real time riser behavior under varying environmental and other operational conditions. The dual riser management system includes a riser analysis subsystem, a mooring analysis subsystem and a vessel stability analysis subsystem.

Abstract: A tendon installation for anchoring a semisubmersible platform to a sea bed foundation, wherein said tendons are tensioned by the updrift of the platform. The tendons are prefabricated in dimensions adpated to the depth of the sea bed foundation, expected tension load and in order to be substantially weightless in water. The tendons are connected in groups at each of their ends at a distance corresponding to the distance between anchoring points in the foundation and the platform respectively. The groups of tendons are towed out to the anchoring site and they are positioned vertically above the foundation. The tendons are fastened to the anchoring points in the foundation. The platform is positioned above the groups of tendons and connected to these via wire ropes. The platform is ballasted down onto the tendons under guidance by said wire ropes. The upper ends of the tendons are mounted internally in the legs of the platform.

Abstract: A drill ahead tool for drilling the initial portion of a subsea well allows an operator to drill ahead after running conductor pipe. The running tool locates in the wellhead housing secured to the upper end of the string of conductor pipe. The running tool has a mandrel that connects into the string of drill pipe. The mandrel locates in a sleeve. The sleeve locates in a body of the running tool. The body has dogs which engage a groove in the wellhead housing to secure the running tool to the wellhead housing while the conductor pipe is being run. The sleeve has a cam on its exterior for maintaining the dogs in the extended position. The drill pipe rotates the sleeve to advance the cam to allow the dogs to be retracted. The mandrel and sleeve have a J-slot and pin that allow the mandrel to be released from the sleeve to continue drilling ahead.

Abstract: A method and apparatus for drilling subsea wells in water depths exceeding 3000 feet (preferably exceeding 4000 feet). Drilling mud returns are taken at the seafloor and pumped to the surface by a centrifugal pump that is powered by a seawater driven turbine. A low-differential pressure rotating head seats in the upper tapered portion of the longitudinal throughbore of an upper stack package which is attached to the top of the blowout preventer stack and seals against the drill string as it is run in and out of the borehole. The method and apparatus of the present invention enable higher mud weights to be used than can be used in conventional techniques which allows kicks to be more easily controlled, fewer casing strings to be run, and overall drilling time reduced by up to 40%.

Abstract: A method and apparatus for setting an underwater conductor pipe in which the conductor pipe is lowered into the wellhole on a drill string as the borehole is being formed by a drill bit and underreamer positioned at the end of the drill string below the end of the conductor pipe. The drill string and conductor pipe are detachably interconnected by a housing latch which includes means for detachably securing the drill string and drilling assembly to the conductor pipe. The drill string is provided with an upper latch sub, which retains and supports the drill string in its fully extended position within the conductor pipe, and a lower latch sub which retains and supports the drill string in the retracted position. As the apparatus is lowered a drill motor actuates the drilling assembly such that the well hole is formed in the ocean floor. Drilling continues until the permanent guide base of the conductor pipe engages the ocean floor.

Abstract: A subsea drilling template has a plurality of drilling guides disposed at various angles relative to the plane of the template. The drilling guides cause angular deviation of the drill string passing into the guides resulting in wide spacing of the boreholes drilling through the template. The widespread boreholes allow efficient production of shallow subsea hydrocarbon producing formation without the need of satellite wells.

Abstract: A device for submarine foundation drilling includes: a drilling unit including a head and body interconnected by at least one cylinder, the body being equipped with at least one cutter, the drilling unit being equipped with at least one excavating pump, and hydraulic motors to operate the cutter and the pump; a rigid tubular assembly (2) containing at least one discharge pipe, and pipes for feeding hydraulic fluid to the cylinder and the motors; connecting means (12) between the head of the drilling unit and the lower part of the tubular construction; support means (13) able to be placed at the ocean bottom in front of the head of the drilling unit, means for clamping the tubular assembly; means for suspending the device from a ship, means (5) being provided to furnish hydraulic power, and connecting pipes being provided between the means of furnishing fluid and the upper end of the tubular assembly.

Abstract: A method and apparatus for protecting an isolated well conductor of a shallow-water well by installing a reinforcing frame against the well conductor near the water line and another frame on the ocean floor and then driving piles through aligned legs of the two frames and into the ocean floor, and subsequently operatively connecting the frames to the piles and the well conductor.

Abstract: An adjustable riser top joint for connecting an offshore subsurface well to a deck mounted welltree. A first plurality of generally annular protrusions on the riser top joint section affords a plurality of connecting points for the wellhead tree using either a unitary or a split collar type attachment. A second plurality of protrusions positioned below deck afford a second plurality of connecting points for riser tensioning means that may also, preferably, be attached using either a unitary or a split collar. The generally annular protrusions are formed as a continuous spiral groove on an external surface of the riser section in a first preferred embodiment and as a series of generally cylindrical protrusions of equal length and spacing in a second preferred embodiment.

Abstract: A mooring system is provided, which can be rapidly installed and which is of relatively low cost. The system includes a transfer structure attached to a vessel, an anchor line extending from the transfer structure to a chain table near the sea floor, and catenary chains extending from the chain table to the sea floor. A weight hangs from the chain table to help in setting up the system and in mooring a vessel thereafter. The transfer structure includes a platform that can rotate with respect to the vessel, and a direction sensor for controlling a motor that rotates the platform opposite to rotation of the vessel, to avoid twist of the anchor line.

Abstract: Wellhead supported subsea template apparatus and methods of installing such template apparatus are provided. The template apparatus are each comprised of a central support member adapted to be positioned into engagement with an upper portion of an existing wellhead and to be supported thereon above the sea floor. Attached to the template are a plurality of laterally spaced guide slot members, mechanisms for removably connecting the central support member to a running tool, and mechanisms for preventing the support member from rotating on the wellhead after being positioned thereon.

Abstract: A method and apparatus are provided for reducing the force required to move a pipe through a J-tube attached to an offshore platform. The J-tube is provided with at least two spaced-apart sections and at least the pipe and/or one section is oscillated as the pipe is moved through the J-tube, thereby reducing the force required to move the pipe.

Abstract: An off-shore floating oil production system is provided with an improved riser support.The oil production system comprises a floating vessel 2 having a moonpool 3 and a support system for supporting a riser 16 running through the moonpool 3. The support system comprises guides 7 in the moonpool 3, a carriage 6 which runs on the guides 7 and means 11 for supporting the carriage 6 which contains a pivoted support (12,13) for the riser 16. Means 17 are also provided for permitting rotation between a section of the riser 16 and the carriage 6.Vertical movement of the carriage compensates for heaving of the vessel, movement of the pivoted support for pitching and rolling and movement of the rotatable means for "weathervaning".

Abstract: The present invention relates to an undersea template for the drilling of wells for the exploitation of hydrocarbon pools under the sea, which template is of variable dimensions and form so as to be able to adapt to any spacing and number of wells, and which is anchored to the seabed by mooring piles and provided with suitable well slots, characterized by the fact that the vertical restraint between the template and the well slots, or between the well slots and the anchorage column of the drill, or between the template and its mooring piles, consists of a flexible member which allows the weight bearing on the template to be reduced to the sole weight of the anchorage columns, with consequent weight reduction of the template itself.

Abstract: Conductor guides for use in drilling wells in an offshore body of water wherein the wells are positioned in close proximity one to the other. A first clamping member is removably attached to a well which includes a conductor or well head protruding therefrom. A conductor guide is spaced a predetermined distance from the clamping by means of a connecting beam that extends therebetween. The connecting beam is adjusted to properly position the conductor guide on the ocean floor at a fixed distance and directional relationship with the first conductor.

Abstract: A method for handling an underwater wellhead assembly by means of an offshore jack-up drilling rig or platform wherein the wellhead assembly is prepared on the shore or quay and is carried on the drilling rig to a preselected drilling location and lowered down therefrom to the ocean floor.

Abstract: A method of alleviating problems with high stresses above fatigue failure levels due to vibrations modes caused by vortex shedding during the lowering and jetting-in of a large diameter surface string in deep water having a current characterized by the inclusion of a moment reducing device in the suspension conduit holding the surface string of conduit during lowering and jetting-in. Also disclosed are preferred embodiments where the moment reducing device is either a ball joint or a flex joint.

Abstract: A buoyancy system for a tension leg platform tether 10 or other element extending a significant vertical distance through a body of water. A series of bulkheads 25 divide the interior of the tether 10 into individual buoyancy cells 31. A central access tube 32 extends along the central axis of the tether 10, passing through a sealed penetration in each bulkhead 25. A series of cascade conduits 42 are provided the lower portion of each buoyancy cell 31 in fluid communication with the buoyancy cell 31 immediately above. A tool 82 is provided for injecting air into a selected buoyancy cell 31. As air is injected, water exists through the central access tube 32 until the buoyancy cell 32 is emptied of water, at which point air passes through the cascade conduit 42 into the adjacent upper buoyancy cell. The tool 82 can also be used to selectively flood individual buoyancy cells 31.

Abstract: An installation comprising a base frame 1 having four locations 2 for well heads 20 and a manifold frame 10 disposed in overhanging fashion inside the zone defined by frame 1. Frame 10 has four locations 17 for a stacked pair of connecting 30 and monitoring 40 modules, as well as a central location 17' for a central control module 50. Each module is provided with guide members 26, 32, 41, 52, for example sleeves, whose geometry corresponds to that of guide devices 3, 18 placed either on guide bases 2 of the frames 1, 10 or on the underlying module, such as guide columns 18. Each module comprises on its lower face a mechanical connector 16 cooperating with a mandril 12 carried on the upper face of the underlying module. The control of locking of the connector is provided by an internal multiconnector receptacle 24, 34, 43, 57 which each module comprises.

Abstract: A pressure balanced tether buoyancy system 12 useful for reducing the load imposed on a tension leg offshore platform 24 by the tethers 10 securing it to the ocean bottom. The tether 10 has tubular tether walls 11 defining a central cavity 15 isolated from the surrounding seawater. A series of bulkheads 25 extend laterally across the interior of the tether 10, dividing it into a series of individual buoyancy cells 31. Each bulkhead 25 is provided with a differential pressure valve 34 establishing selective fluid communication between the two buoyancy cells 31 separated by the bulkhead 25. Preferably, each differential pressure valve 34 is adapted to open in response to a differential pressure across the bulkhead 25 exceeding the differential hydrostatic existing across the vertical distance separating adjacent bulkheads 25. This permits a pressure gradient to be established interior to the tether 10 approximating that of the seawater in which the tether 10 is located.

Abstract: A subsea drilling and production system where the production unit is removably connected onto a drilling template and operatively connected to one or more Christmas trees so that the production unit may be disconnected from the trees and removed from the template without first removing any of the trees and so that any of the trees may be disconnected from the production unit and removed from the underwater site without removing the production unit.

Abstract: A riser tensioning and recoil system for a riser extended between a floating platform and a submerged riser base comprises at least one riser tensioning cable which is operatively connected to the riser and to a collar which is slidably arranged around the riser. To establish a controlled recoil of the riser, stop means are provided that restrict axial movement of the collar relative to the riser after the riser has been lifted from the riser base, thereby enabling the collar to gradually decelerate the vertical movement of the riser.

Abstract: Apparatus for use in drilling a well from a floating vessel by means of a riser, which connects the vessel's drilling equipment to a wellhead assembly adjacent to the ocean floor. The riser moves substantially vertically in relation to the vessel, as the vessel responds to wave action. The present riser position indication apparatus is comprised of a load cell and a chain attached beneath the load cell. Movement of the riser relative to the vessel alters the length of chain suspended from the load cell, thereby altering the signal from the cell. The signal can be subsequently calibrated to represent riser position.

Abstract: A method and apparatus for establishing the rate at which fluid is transferred between an offshore well 16 and the formations 20 surrounding the well 16 in the course of drilling the well 16 from a floating drilling rig 14. A drilling fluid handling system 31 is used to inject drilling fluid into the well 16. A marine riser 22 extending from the sea bottom 18 to the rig 14 is provided to return the drilling fluid to the rig 14. The riser 22 is provided with a slip joint 26 to accommodate wave induced heave of the rig 14. Inflow and outflow flowmeters 42,44 are provided to monitor the rates at which drilling fluid is injected into the well 16 and returned to the rig 14. The return flow rate signal is filtered to mitigate the cyclical variations resulting from extension and contraction of the slip joint 26. A signal processing system 46 is provided to maintain the time constant applied in the filtering process at an optimum level as the rate and magnitude of rig heave varies with time.

Abstract: A jackdown tension leg platform is set forth which may be used for processing a commodity liberated from the ocean floor by one or more wells. The platform includes a closed buoyant hull which houses production equipment and at least one connector disposed on the hull for vertical relative movement. The connector has one end secured to the ocean floor and is moved upwardly relative to the hull to submerge the hull to a depth below the majority of the ocean's hydrostatic forces and, at the same time, tension the connector to hold and stabilize the hull over the wells. Conduits are connected between the wells and the submerged hull and between the hull and the surface. A crew module may be provided above the surface atop the connector with a trunk disposed between the module and submerged hull to provide access therebetween.

Abstract: A combination offshore drilling rig which combines the desirable features of a slot-type drilling rig and a cantilever-type drilling rig while eliminating the limitations and undesirable features associated with either type of such rigs. The combination offshore drilling rig mounts the derrick and drilling equipment on a movable cantilever structure which may be positioned over a slot of sufficient area to permit the drilling operation to be carried out through the slot or may be moved outboard of the peripheral boundary of the rig hull to perform a drilling or workover operation outside the peripheral boundary of the rig hull.

Abstract: An anchored submerged marine structure commonly referred to as a well template is located at the bottom of a body of water and used in the directional drilling of underwater wells. The well template carries curved well conductors, each conductor capable of deviating well drilling equipment passed through the conductor so that each well may reach reservoirs located a further distance away from the template. The template's upper surface is formed to aid in the installation of the well conductor through the template.

Abstract: Method and apparatus for use in drilling a well from an offshore drilling vessel having a riser extending from the vessel down to a subsea wellhead. The apparatus of the invention comprises a flexible coupling installed in the riser's upper elements, with a tensioned cable connected between the flexible coupling and the vessel. The angle of misalignment of the riser's upper elements due to ocean currents impacting the riser and/or vessel may be maintained within acceptable limits by adjusting the tension applied to the flexible coupling.

Abstract: A marine heave compensating device comprises a hydraulic piston and cylinder unit (15,16) with its cylinder (15) secured to a support (10,11). The piston is connected via a piston rod (16) to a cross-head (17) on which a first set of pulleys (18) are rotatably mounted. Chains (19) secured at one end to the support (10,11) are entrained around pulleys (18) and support a yoke (20) on which is mounted a crown block (21). A cable (22) is reeved around crown block (21) and around a travelling block (23) which carries a tool carrier (24). The two ends of cable (22) are reeved around two second pulleys (26A,26B) rotatably mounted on the cross-head (17). End (22A) of cable (22) is connected to a draw-works and end (22B) of cable (22) is connected to a tie-down.

Abstract: A readily portable seabed penetration system for conducting cone penetrometer tests or the like from a support disposed above the water over the portion of the seabed to be penetrated. The system includes a casing string connected at its upper end to the support and at its lower end to a suction anchor. A string of push rods encased within the casing string is provided at its lower end with a penetrometer cone. With the suction anchor evacuated, the lower end of the casing is securely anchored to the seabed. Upward tension is then applied to the casing while downward force is applied to the rod string to drive the penetrometer cone into the seabed. The rod string is supported against buckling by the tensioned casing string.

Abstract: System for drilling from a water surface, of the type having means for exerting and maintaining on the drilling tool a bearing stress, which is constant and normal to the surface to be perforated, no matter what the effect of the swell, wherein it comprises in combination: a base having a central passage for the drill pipe string of a drilling apparatus, which is intended to rest on the sea bed and is elastically connected to means for receiving a cylindrical box; a column formed by a cylindrical tubular central guide, for permitting the passage and guidance of the drill pipe string of the drilling apparatus, the column being surrounded by an external cylindrical tubular envelope, the hollow annular space formed between the central guide and the envelope being subdivided into a tight member constituting the lower ballast, a tight intermediate member of variable length determined as a function of the mean value of the section of water under which drilling takes place, a tight member constituting an upper balla

Abstract: An aqueous slurry of spent drilling mud and/or produced water is diluted prior to free discharge into a body of receiving water by expelling a jet stream of such slurry into an open-ended submerged mixing conduit. The jet stream aspirates and entrains the surrounding water within the conduit and is then passed through a mixer stage prior to exiting the opposite end of the tube.

Abstract: A method and apparatus for remotely replacing damaged guideposts attached to a subsea structure are provided. A receptacle is permanently attached to the subsea structure. The guidepost is inserted into the receptacle and is releasably connected thereto by one or more radially-oriented, spring loaded lock pins. Damaged guideposts are removed by applying an upward vertical force to the guidepost sufficient to shear the lock pin or lock pins. The upward vertical force is applied by a replacement tool capable of being remotely operated from the surface of the body of water. Following removal of the damaged guidepost, a new guidepost is inserted into the receptacle. Lock pins mounted in the new guidepost retract into the guidepost as it is being inserted. When fully inserted, the lock pins extend and engage a retaining groove formed in the receptacle thereby firmly locking the new guidepost in place.

Abstract: A temporary guide base for use in drilling underwater wells in areas where the bottom conditions are unstable comprises a plurality of boxes opened at the bottom having a centrally disposed hole for casing, and vent means to allow retrieval of the guide bases without causing a suction effect, the guide bases being open to the sea on the bottom to fill the sea water but float in the mud on the bottom.

Abstract: An oscillatable marine installation comprises a concrete and steel lattice shaft supported by means of a demountable pivot joint on a base fixed to the-sea-bed and including an anti-torque device. The pivot joint is made up of three parts: a casing fixed to the shaft, a part-spherical housing fixed to the base, and a pivot member. The pivot member has an upper part cooperating with the casing, a flange which can be fixed to the casing, and a lower part-spherical part housing which supports a resilient assembly and a bush fixed on the housing. The anti-torque device comprises a universal joint, concentric with the pivot joint. Two opposite pivots of the crosspiece of the universal joint are supported by the lower part of the shaft and the other two pivots by the base. At least two opposite pivots have damping devices and the pivots supported by the base are mounted on supports the height of which can be adjusted.

Abstract: A drilling rig comprises a platform (10) supported above a sea surface (14) by legs which extends to the sea bottom (16). A drill guide (30) of rigid open framework construction extends down from the platform to the sea bottom. The drill guide is only minimally affected by turbulent sea conditions because of its open framework construction. A hardenable substance such as concrete (54) is poured into a flexible bag (50) at the lower end of the drill guide to form a solid structure conforming to the uneven sea bottom and having a substantially flat upper surface. Drilling takes place through the hardenable substance and into the underlying sea bottom.

Abstract: A motion compensator for disposition between an offshore support structure and an offshore well structure movable with respect thereto comprises a compensator assembly interconnected with the support structure and the well structure such that relative movement between said structures will cause movement within the compensator assembly, and a position indicator including a cam assembly for measuring the relative movement within the compensator assembly, and a transducer operatively associated with the cam assembly for translating its measurements into a signal.

Abstract: A method and apparatus is disclosed for eliminating vertical motion of a downhole tool in a subsea borehole as the tool is being operated by a drill string from a floating vessel. A vertical motion elimination means is incorporated into the drill string at a point which will be adjacent a blowout preventer stack on the marine bottom when the downhole tool is positioned at a desired point in the borehole. The vertical motion elimination means is comprised of a sleeve which is rotatably mounted on the drill string at a fixed vertical position. The sleeve is adapted to be engaged by the blowout preventer stack to fix the sleeve against vertical movement with respect to the preventer. Since the sleeve, itself, is fixed against vertical movement on the drill string, that portion of the drill string which lies below the preventer (hence, the downhole tool) will also be fixed against vertical motion within the borehole.