Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/02—Surface sealing or packing
  • E21B33/03—Well heads; Setting-up thereof
  • E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/02—Surface sealing or packing
  • E21B33/03—Well heads; Setting-up thereof
  • E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
  • E21B33/038—Connectors used on well heads, e.g. for connecting blow-out preventer and riser
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
  • E21B41/0007—Equipment or details not covered by groups E21B15/00 - E21B40/00 for underwater installations
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
  • E21B41/04—Manipulators for underwater operations, e.g. temporarily connected to well heads
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
  • E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
  • E21B43/017—Production satellite stations, i.e. underwater installations comprising a plurality of satellite well heads connected to a central station
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/02—Surface sealing or packing
  • E21B33/03—Well heads; Setting-up thereof
  • E21B33/06—Blow-out preventers, i.e. apparatus closing around a drill pipe, e.g. annular blow-out preventers
  • E21B33/064—Blow-out preventers, i.e. apparatus closing around a drill pipe, e.g. annular blow-out preventers specially adapted for underwater well heads

Definitions

• the disclosure relates generally to systems and methods for tethering subsea structures. More particularly, the disclosure relates to systems and methods for enhancing the strength and fatigue performance of subsea blowout preventers, wellheads, and primary conductors during subsea drilling, completion, production, and workover operations.
• a blowout preventer BOP
• LMRP lower marine riser package
• the subsea BOP and LMRP are arranged one-atop-the-other.
• a drilling riser extends from a flex joint at the upper end of the LMRP to a drilling vessel or rig at the sea surface.
• the drill string is suspended from the rig through the drilling riser, LMRP, and BOP into the well bore. Drilling generally continues while successively installing concentric casing strings that line the borehole.
• Each casing string is cemented in place by pumping cement down the casing and allowing it to flow back up the annulus between the casing string and the borehole sidewall.
• drilling fluid or mud
• the cased well is completed (i.e., prepared for production).
• the horizontal subsea production tree is installed on the wellhead below the BOP and LMRP during completion operations.
• the subsea production tree, BOP, and LMRP are arranged one-atop-the-other.
• Production tubing is run through the casing and suspended by a tubing hanger seated in a mating profile in the inner wellhead housing or production tree.
• the BOP and LMRP are removed from the production tree, and the tree is connected to the subsea production architecture (e.g., production manifold, pipelines, etc.). From time to time, intervention and/or workover operations may be necessary to repair and/or stimulate the well to restore, prolong, or enhance production.
• subsea production architecture e.g., production manifold, pipelines, etc.
• a system for tethering a subsea blowout preventer may comprise an anchor disposed about the subsea BOP and secured to the sea floor.
• the system may further comprise a flexible tension member.
• the flexible tension member may have a first end including a releasable connector engaged to the anchor.
• the flexible tension member may extend horizontally and vertically from the first end to a second end to impart a lateral preload and a vertical preload to the subsea BOP.
• the system may further comprise a tensioning system.
• the tensioning system may include a releasable base removeably connected to the subsea BOP.
• the tensioning system may further include a gripping system coupled to the releasable base, or part of, or mounted on, the subsea BOP.
• the gripping system may be configured to selectively engage the flexible tension member to prevent pay out of the flexible tension member.
• the system may further comprise a winch reel coupled to the second end of the flexible tension member, and an interface configured for coupling to a remotely operated vehicle (ROV), wherein rotation of the interface causes rotation of the winch reel and paying in or out the flexible tension member.
• ROV remotely operated vehicle
• the system may further comprise a spool coupled to the second end of the flexible tension member, and a hydraulic cylinder coupled to the gripping system, wherein actuation of the hydraulic cylinder causes paying in or out the flexible tension member.
• the system may further comprise a winch reel coupled to the second end of the flexible tension member, wherein the winch reel is located on a vessel.
• Figure 1 is a schematic partial cross-sectional side view of an offshore system for completing a subsea well including an embodiment of a subsea tethering system in accordance with the principles described herein;
• Figure 2 is an enlarged partial isometric view of the offshore system of Figure 1 illustrating the tethering system
• Figure 3 is a partial isometric view of an offshore system
• Figure 4 is an enlarged partial isometric view of the offshore system of Figure 3 illustrating the anchors
• Figures 5 and 6 are enlarged isometric views of one of the tensioning systems of Figure 3.
• Figure 7 is a side view of an alternate tensioning system.
• the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to... .”
• the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections.
• the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis.
• an axial distance refers to a distance measured along or parallel to the central axis
• a radial distance means a distance measured perpendicular to the central axis.
• system 10 includes a floating offshore vessel 30 at the sea surface 11, a horizontal production tree 40 releasably connected to a wellhead 50 disposed at an upper end of a primary conductor 51 extending into the wellbore 20, a subsea blowout preventer (BOP) 41 releasably connected to production tree 40, and a lower marine riser package (LMRP) 42 releasably connected to BOP 41.
• BOP subsea blowout preventer
• LMRP lower marine riser package
• Tree 40, BOP 41, and LMRP 42 are vertically arranged or stacked one-above-the-other, and are generally coaxially aligned with wellhead 50.
• Wellhead 50 has a central axis 55 and extends vertically upward from wellbore 20 above the sea floor 12.
• system 10 is shown configured for completion operations, and thus, includes tree 40, however, for drilling operations, tree 40 may not be included.
• vessel 30 is equipped with a derrick 31 that supports a hoist (not shown).
• vessel 30 is a semi-submersible offshore platform, however, in general, the vessel (e.g., vessel 30) can be any type of floating offshore drilling vessel including, without limitation, a moored structure (e.g., a semi-submersible platform), a dynamically positioned vessel (e.g., a drill ship), a tension leg platform, etc.
• a drilling riser 43 (not shown in Figure 2 of the '852 patent) extends subsea from vessel 30 to LMRP 42. During drilling operations, riser 43 takes mud returns to vessel 30.
• BOP 41 includes an outer rectangular prismatic frame 47.
• BOP 41 and LMRP 42 are configured to controllably seal wellbore 20 and contain hydrocarbon fluids therein.
• BOP 41 includes a plurality of axially stacked sets of opposed rams disposed within frame 47.
• BOP 41 can include any number and type of rams including, without limitation, opposed double blind shear rams or blades for severing the tubular string and sealing off wellbore 20 from riser 43, opposed blind rams for sealing off wellbore 20 when no string/tubular extends through BOP 41, opposed pipe rams for engaging the string/tubular and sealing the annulus around string/tubular, or combinations thereof.
• LMRP 42 includes an annular blowout preventer comprising an annular elastomeric sealing element that is mechanically squeezed radially inward to seal on a string/tubular extending through LMRP 42 or seal off wellbore when no string/tubular extends through LMRP 42.
• the upper end of LMRP 42 includes a riser flex joint 44 that allows riser 43 to deflect and pivot angularly relative to tree 40, BOP 41, and LMRP 42 while fluids flow therethrough.
• the hardware mounted to wellhead 50 proximal the sea floor 12, production tree 40 and BOP 41 in particular is relatively tall, and thus, presents a relatively large surface area for interacting with environmental loads such as subsea currents. These environmental loads can also contribute to the fatigue of BOP 41 , wellhead 50, and primary conductor 51. If the wellhead 50 and primary conductor 51 do not have sufficient fatigue resistance, the integrity of the subsea well may be compromised.
• an uncontrolled lateral movement of vessel 30 e.g., an uncontrolled drive off or drift off of vessel 30
• LMRP 42 laterally with riser 43, thereby inducing bending moments and associated stresses in BOP 41, wellhead 50, and conductor 51.
• Such induced bending moments and stresses can be increased further when the relatively tall and heavy combination of tree 40 and BOP 41 is in a slight angle relative to vertical.
• a tethering system 100 is provided to reinforce BOP 41, wellhead 50, and primary conductor 51 by resisting lateral loads and bending moments applied thereto.
• system 100 offers the potential to enhance the strength and fatigue resistance of BOP 41, wellhead 50, and conductor 51.
• tethering system 100 includes a plurality of anchors 110, a plurality of pile top assemblies 120, and a plurality of flexible tension members 160.
• One pile top assembly 120 is mounted to the upper end of each anchor 110, and one tension member 160 extends from each pile top assembly 120 to frame 47 of BOP 41.
• each pile top assembly 120 includes a tensioning system 140 that can apply tensile loads to the corresponding tension member 160.
• each tensioning system 140 is a winch, and thus, may also be referred to as winch 140.
• winch 140 can pay in and pay out the corresponding tensioning member 160.
• Each tension member 160 includes a first or distal end 160a coupled to frame 47 of BOP
• each distal end 160a is coupled to frame 47 of BOP 41 at a height H measured vertically from the sea floor 12 and at a lateral distance D measured radially and horizontally from central axis 55.
• height H of each end 160a is the same
• lateral distances D to each end 160a is the same.
• lateral distance D is preferably between 5.0 and 15.0 feet, and more preferably about 10.0 ft.
• lateral distance D may depend, at least in part, on the available connection points to the frame 47 of BOP 41.
• each height H is preferably as high as possible but below LMRP
• a tensile preload L is applied to each tensioned span 161.
• the actual tension in each span 161 is the same or substantially the same as the corresponding tensile preload L.
• the actual tension in each span 161 can be greater than or less than the corresponding tensile preload L.
• Winches 140 are positioned proximal to the sea floor 12, and ends 160a are coupled to frame 47 of BOP 41 above winches 140.
• each span 161 is oriented at an acute angle a measured upward from horizontal. Since portions 161 are in tension and oriented at acute angles a, the tensile preload L applied to frame 47 of BOP 41 by each span 161 includes an outwardly oriented horizontal or lateral preload Li and a downwardly oriented vertical preload Ly.
• the lateral preload Li and the vertical preload L v applied to BOP 41 by each tension member 160 are a function of the corresponding tensile load L and the angle a.
• the lateral preload Li and the vertical preload L v increase as the tensile load L increases, and decrease as the tensile load L decreases.
• the lateral preload Li decreases and the vertical preload L v increases as angle a increases, and the lateral preload Li increases and the vertical preload L v decreases as angle a decreases.
• angle a of each span 161 is preferably between 10° and 60°, and more preferably between 30° and 45°.
• each height H is preferably as high as possible but below LMRP 42, and may depend on the available connection points along frame 47 of BOP 41.
• ends 160a are coupled to frame 47 proximal the upper end of BOP 41 and just below LMRP 42.
• system 100 By tethering frame 47 of BOP 41 at this location, system 100 restricts and/or prevents BOP 41 , tree 40, wellhead 50, and primary conductor 51 from moving and bending laterally, thereby stabilizing such components, while simultaneously allowing LMRP 42 to be disconnected from BOP 41 (e.g., via emergency disconnect package) without any interference from system 100.
• the tensile preload L in each span 161 is preferably as low as possible but sufficient to pull out any slack, curve, and catenary in the corresponding span 161.
• the tensile preload in L in each span 161 is preferably the lowest tension that results in that span 161 extending linearly from the corresponding winch 140 to its end 160a.
• Such tensile loads L in tension members 160 restrict and/or prevent the initial movement and flexing of BOP 41 at the onset of the application of an external loads and/or bending moments, while minimizing the tension in each span 161 before and after the application of the external loads and/or bending moments. The latter consequence minimizes the potential risk of inadvertent damage to BOP 41, tree 40, and LMRP 42 in the event one or more tension members 160 uncontrollably break.
• each tension member 160 can include any elongate flexible member suitable for subsea use and capable of withstanding the anticipated tensile loads (i.e., the tensile preload L as well as the tensile loads induced in spans 161 via the application of external loads to BOP 41) without deforming or elongating.
• suitable devices for tension members 160 can include, without limitation, chain(s), wire rope, and Dyneema® rope available from DSM Dyneema LLC of Stanley, North Carolina USA.
• each tension member 160 comprises Dyneema® rope, which is suitable for subsea use, requires the lowest tensile preload L to pull out any slack, curve, and catenary (- 1.0 ton of tension), and is sufficiently strong to withstand the anticipated tensions.
• an alternate tethering system 200 includes a plurality of anchors 220, a plurality of tensioning systems 240, a plurality of flexible tension members 260.
• a tension member 260 is connected to the top of each of the plurality of anchors 220 and extends from each anchor 220 to a tensioning system 240 mounted on frame 47 of BOP 41.
• each tensioning system 240 includes a winch or spool 242 that can pay in and pay out the corresponding tension member 260 and a gripping mechanism 244 to engage the tension member 260.
• a winch refers to a reel having sufficient tensioning capacity to apply to the tension member 260 a tensile preload L as discussed in the description of Figure 1.
• a spool refers to a reel having a tensioning capacity to apply at least a tension sufficient to avoid sagging of the tension member 260, but the tension member 260 may remain slack.
• a spool may, however, have a tensioning capacity larger than the tension required to prevent sagging and may have as much tensioning capacity as a winch.
• FIG 4 illustrates one embodiment of an anchor 220 to which a tension member 260 is connected.
• Anchor 220 may be a driven piling, a clump weight, a suction piling, plate anchor, or any other structure used to affix a base to the sea floor.
• the top of the anchor 220 includes a connecting ring 270, or other feature that provides a location for affixing an end of a tension member 260.
• tension member 260 includes a releasable connector 280 that allows an ROV to selectively engage and disengage the tension member 260 from the anchor 220.
• the gripping system 310 may be coupled to the BOP frame 47 or be part of or mounted on the BOP 41.
• Figures 5 and 6 illustrate one embodiment of a tensioning system 240 including a frame 300, gripping system 310, winch reel 320, and ROV interface 330.
• the tensioning system 240 is removeably connected to the BOP frame 47 at connection points 340.
• An ROV, or other equipment can be used to install each tensioning system 240 onto the BOP frame 47 subsea by flying the tensioning system 240 into place and connecting it to the connection points 340. The ROV can then be used to rotate winch reel 320 paying in or out tensioning member 260 as needed.
• gripping system 310 can be activated to grip the tensioning member 260 and maintain any tension in the tension member 260.
• Gripping system 310 can be any type of gripping system that can apply a fixing force to the tensioning member 260, such as a hydraulic slip system, a locking ring, or a brake mechanism.
• the hydraulic slip may be used for paying in or out tension member 260.
• the hydraulic slip includes one or more hydraulic cylinders and a slip or gripper that may have a first configuration for paying in the tension member 260, applying to the tension member 260 a tensile preload L as discussed in the description of Figure 1, preventing pay out of the flexible tension member 260, and/or maintaining any tension in the tension member 260.
• the one or more hydraulic cylinders and the slip or gripper may have a second configuration for paying out the tension member 260.
• an alternative tensioning system 400 is shown that includes a frame 300 and gripping system 310 connected to a BOP frame 47 at connection points 340.
• the winch assembly 410 is located remote from the tensioning system 400, such as at the surface on the drilling or service vessel. Winch assembly 410 is used to apply pay in or out to tension member 260 as needed to achieve the desired tension. Once the tension member 260 is properly tensioned, gripping system 310 can be activated to grip the tension member 260 and maintain any tension in the tension member 260.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Earth Drilling (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (3)

Cited By (4)

Families Citing this family (5)

Citations (6)

Family Cites Families (1)

• 2018
  • 2018-02-05 EP EP18748787.1A patent/EP3577307A4/en active Pending
  • 2018-02-05 US US16/481,731 patent/US20200003025A1/en not_active Abandoned
  • 2018-02-05 WO PCT/US2018/016821 patent/WO2018144985A1/en unknown

Patent Citations (6)

Non-Patent Citations (1)

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