Well control system for a riser, method of measuring at least one drilling fluid parameter or property in a subsea riser and method of managed pressure drilling in a subsea drilling operation

Abstract

WELL CONTROL SYSTEM AND METHOD OF USE. The invention provides a well control system for a riser. The well control system comprises a riser assembly and at least one flow meter. The at least one flow meter is configured to be mounted on the riser.

Description

1 / 41 “WELL CONTROL SYSTEM FOR A RISER, METHOD FOR MEASURING AT LEAST ONE PARAMETER OR PROPERTY OF A FLUID OF Drilling in a subsea riser and managed pressure drilling method in a subsea drilling operation.

[001] The present invention relates to wellbore control systems and method of use and, in particular, managed pressure drilling for subsea applications. A particular aspect of the invention relates to the conversion of existing drilling systems to enable managed pressure drilling operations. Fundamentals of the Invention

[002] Drilling operations typically use a rotary drill bit at the end of a drill string. Mud is pumped up the drill string from a rig mud pumping system and returned to the surface flowing in the annular space between the drill string and the well. The return mud exits the annular space above a BOP (Blowout Preventer) into a mud return line where it flows freely to the solids control equipment to allow sand and cuttings to be removed from the well. The mud is stored in holding tanks until it is pumped back into the well.

[003] The mud that is pumped through the drill string performs several functions, including providing hydraulic power to the drilling tools at the end of the drill string, stabilizing the well, and cooling the drill bit. The mud provides pressure in the well, which prevents an influx of pressurized gas or oil from any hydrocarbon-containing formations. Pressure is a function of mud density, wellbore friction caused by mud flow, and the vertical depth of the well. Mud density must be controlled to provide a bottomhole pressure that is above pore pressure (the pressure at which the well may collapse or allow an influx of hydrocarbons) but below fracture pressure (the pressure Petition 870250090587, dated 03 / 10 / 2025, page 11 / 103 2 / 41 where the well structure may fracture).

[004] Managed Pressure Drilling (MPD) is a form of drilling in which the pressure at the bottom of the well is controlled more precisely using various methods beyond mud density control. MPD is used to drill wells in conditions where the local geology makes conventional drilling difficult or impossible.

[005] For MPD operations, the mud circulation system becomes a closed loop with return mud from the wellbore flowing into an arrangement of valves or manifolds that can apply backpressure or direct the flow to other processing systems. The ring is capped above the BOP using a seal, typically a rotary control device (RCD).

[006] Offshore drilling relies on the use of a tubular structure, known as a drilling riser, which allows the ring to extend from the seabed to the surface. For floating drilling vessels, a riser section known as a sliding joint or telescopic joint is used to allow free movement of the drilling vessel caused by wave motion.

[007] Managed pressure drilling systems are known to utilize a managed pressure drilling manifold comprising metering, distribution, and throttling manifolds mounted in a bucket on the rig at the surface. However, these manifolds are bulky and occupy considerable space on a rig or drilling vessel. The manifolds also require several hoses and control lines to be run from the riser to the manifold. Summary of the Invention

[008] It is an object of one aspect of the present invention to avoid or at least mitigate the previous disadvantages of well control of the prior art and managed pressure drilling systems. Petition 870250090587, dated 03 / 10 / 2025, page 12 / 103 3 / 41

[009] Another object of an aspect of the present invention is to provide a robust, reliable and compact well control system suitable for deployment on riser assemblies used in a variety of drilling operations.

[010] It is another object of an aspect of the present invention to provide marine risers with a pressure-managed drilling system with improved reliability and affordability.

[011] Another object of an aspect of the present invention is to provide a marine riser conversion system for managed pressure drilling operations.

[012] Other objectives of the invention will become apparent from the description that follows.

[013] According to a first aspect of the invention, a well control system for a riser is provided comprising: a riser assembly; and at least one flow meter; where at least one flow meter is configured to be mounted on the riser.

[014] At least one flow meter may be configured to be mounted on or located on an external surface of the riser above or below a tension ring.

[015] At least one flow meter may be a differential pressure flow meter. At least one flow meter may be selected from the group comprising orifice plate, wedge, venturi, Coriolis, Pitot tubes and / or variable area flow meters.

[016] The system may comprise a control unit. The control unit may be configured to receive at least one measurement signal from at least one flow meter and analyze the measurement signal in the control unit to Petition 870250090587, dated 03 / 10 / 2025, page 13 / 103 4 / 41 Monitor the flow of drilling fluid in the riser and / or in at least one mud return line.

[017] The control unit can be configured to analyze the measurement signal to monitor at least one parameter or at least one property of the drilling fluid or drilling fluid flow in the riser and / or in at least one mud return line.

[018] The control unit can determine or calculate a Reynolds number for the drilling fluid flow. The control unit can be configured to correct the Reynolds number as the properties of the drilling fluid change. The fluid properties can change due to contaminants such as debris, hydrocarbons, cuttings, sand, water, etc.

[019] The control unit can be configured to compare at least one parameter with a desired range of operating parameters. The control unit can be configured to generate a control signal when at least one parameter is determined to be outside the desired range of operating parameters.

[020] The control unit can be configured to calculate, estimate, or predict the density and / or viscosity of the flowing drilling fluid. The control unit can be configured for gas determination.

[021] At least one flow meter may have a flow measurement range of 10 to 2000 USG / min.

[022] The system may comprise two or more flow meters. Each flow meter may have a different fluid flow range and / or fluid density range.

[023] Preferably, the system has two or more flow meters. The two or more meters can be arranged in series or in parallel. The two or more meters can be mounted on a meter manifold. A first meter of Petition 870250090587, dated 03 / 10 / 2025, page 14 / 103 A 5 / 41 flow meter may have a flow measurement range of 10 to 400 USG / min. A second flow meter may have a flow measurement range of 100 to 2000 USG / min.

[024] The internal diameters of the flow meters can be selected to determine a flow measurement range. A 2-inch diameter can be selected to have a flow measurement range of 10 to 400 USG / min. A 5-inch diameter can be selected for a flow measurement range of 100 to 2000 USG / min.

[025] Preferably, the riser assembly comprises a riser isolation device. At least one flow meter may be mounted on at least one meter collector. The riser isolation device and / or at least one flow meter collector may be located on a riser above a riser tension ring. The riser isolation device and / or at least one flow meter collector may be located on a riser below a riser tension ring.

[026] The riser assembly may comprise at least one choke assembly. The at least one choke assembly may be mounted on the riser. The at least one choke assembly may be a choke manifold. The at least one choke assembly may be located on a riser above or below a riser tension ring. The at least one choke assembly may be mounted on or located on the outer surface of a riser above or below a riser tension ring.

[027] The riser assembly may comprise a rotary control device. The rotary control device may be located on a riser above or below a riser tension ring.

[028] At least one throttling assembly and / or at least one flow meter assembly may form part of a managed pressure drilling manifold. The managed pressure drilling manifold may be Petition 870250090587, dated 03 / 10 / 2025, page 15 / 103 6 / 41 mounted on the riser. The managed pressure drilling manifold can be mounted on or located on the outer surface of a riser above or below a riser tension ring.

[029] At least one flow meter may be integrated with a flow spool and / or at least one choke assembly. The riser assembly may comprise an integrated flow spool, choke manifold and / or flow meter manifold in a riser joint or a riser slip joint. The riser slip joint may be a recoverable riser slip joint. The riser assembly may comprise an upper riser disconnect assembly. The upper riser disconnect assembly may be located above the riser tension ring.

[030] The riser isolation device, at least one flow meter, at least one choke assembly, rotary control device and / or managed pressure drilling manifold may be located on a riser and / or sliding joint above the upper riser disconnect assembly.

[031] Providing at least one flow meter on the riser allows for improved well control, as drilling fluid properties and returns can be accurately measured and / or monitored. It also provides improved hose management, as hoses and control lines do not need to run from the riser to flow meters located on the surface. Providing a flow meter directly on the riser also avoids the need for bulky measurement manifolds on the rig.

[032] Providing components of a riser assembly above an upper riser disconnect assembly above the tension ring can allow the components to be installed, removed or replaced easily.

[033] The upper riser assembly comprising a sliding joint, at least one flow meter, at least one throttling assembly, rotary control device and / or the pressure-managed drilling manifold may be Petition 870250090587, dated 03 / 10 / 2025, page 16 / 103 7 / 41 installed on the riser and the RCD and / or other MPD equipment kept offline during drilling and only brought online for a necessary MPD operation.

[034] At least one choke assembly may receive drilling fluid from the riser annulus below the RCD. At least one choke assembly may be an MPD choke.

[035] The upper riser disconnect assembly, riser isolation device, at least one flow meter, at least one choke assembly, rotary control device and / or the managed pressure drilling manifold can be remotely controlled.

[036] At least one flow meter may be an in-line flow meter. At least one flow meter may be configured to be connected to a distribution assembly comprising at least one valve assembly. The distribution assembly may be located on the riser. At least one flow meter and / or the distribution assembly may be connected to at least one choke assembly mounted on the riser. The distribution assembly may comprise at least one reel or hose connecting at least one flow meter and / or at least one choke assembly.

[037] At least one set of valves in the riser may be configured to open a path between the riser annulus and the distribution assembly, at least one flow meter and / or at least one throttling assembly.

[038] The tension ring may be arranged circumferentially around a portion of the riser, a portion of the RID, a portion of the sliding joint, an outer cylinder of a sliding joint, a portion of the upper riser disconnect assembly and / or a tension joint.

[039] The upper riser disconnect assembly may comprise an upper connector and a lower connector. The lower and upper connectors may be configured to disconnect from each other. The upper and lower connectors Petition 870250090587, dated 03 / 10 / 2025, page 17 / 103 Separate 8 / 41 units can be configured to connect to each other.

[040] The sliding joint may be a two-part sliding joint. Alternatively, the sliding joint may be a three-part or more-part sliding joint. The sliding joint may comprise at least one sealing assembly. The sliding joint may be a telescopic joint. The sliding joint may comprise two telescopic members. The sliding joint may comprise more than two telescopic members.

[041] According to a second aspect of the invention, a riser assembly is provided comprising: a riser; and a pressure-managed drilling manifold mounted on the riser.

[042] The managed pressure drilling manifold may comprise at least one flow meter module, at least one throttling module and / or at least one valve assembly.

[043] The managed pressure drilling manifold may comprise an integrated flow spool, choke manifold and / or metering manifold. The managed pressure drilling manifold may be mounted on a recoverable riser sliding joint.

[044] At least one flow meter module may comprise at least one flow meter. At least one flow meter may be an in-line flow meter. At least one flow meter may be configured to be connected to a distribution assembly comprising at least one valve assembly. The distribution assembly may be located on the riser. At least one flow meter and / or the distribution assembly may be connected to at least one choke assembly mounted on the riser. The distribution assembly may comprise at least one reel or hose connecting at least one flow meter and / or at least one choke assembly. Petition 870250090587, dated 03 / 10 / 2025, page 18 / 103 9 / 41

[045] At least one set of valves in the riser may be configured to open a path between the riser annulus and the distribution assembly, at least one flow meter and / or at least one throttling assembly.

[046] The riser assembly can be connected to or installed on a riser system to allow managed pressure drilling operation without requiring structural modifications to the riser. The upper riser assembly comprising a riser isolation device and a managed pressure drilling manifold can be connected to the upper riser disconnection assembly located above the tension ring.

[047] Embodiments of the second aspect of the invention may include one or more features of the first aspect of the invention or embodiments thereof, or vice versa.

[048] According to a third aspect of the invention, a well control system is provided comprising: an upper riser assembly comprising an upper riser disconnect assembly; and at least one flow meter assembly, wherein at least one flow meter assembly is mounted on the upper riser assembly.

[049] At least one flow meter assembly may be mounted on an external surface of the upper riser assembly. The upper riser assembly may comprise a riser isolation device. The upper riser assembly may comprise a sliding joint. At least one flow meter assembly may be mounted on an external surface of the sliding joint.

[050] The sliding joint and / or riser isolation device may be mounted on the upper riser disconnect assembly above the upper riser disconnect assembly.

[051] The upper riser assembly can be connected to a lower riser. The Petition 870250090587, dated 03 / 10 / 2025, page 19 / 103 The 10 / 41 upper riser assembly can be connected to a lower riser by connecting the upper riser disconnect assembly to the riser. The upper riser assembly can be connected to a riser above a riser tension ring.

[052] The system may comprise at least one choke assembly. At least one choke assembly may be mounted on the upper riser assembly. At least one choke assembly may be mounted on the sliding joint. The upper riser assembly may be a self-contained well control system.

[053] At least one flow meter and / or at least one throttling assembly may be integrated with a flow spool. The at least one integrated flow meter, at least one throttling assembly and integrated flow spool system may be mounted on a recoverable sliding joint.

[054] The riser assembly may comprise a rotary control device. The rotary control device may be located in the system between the sliding joint and the RID.

[055] At least one choke assembly and / or at least one flow meter assembly may form part of a managed pressure drilling manifold. The managed pressure drilling manifold may be mounted on the upper riser assembly and / or sliding joint.

[056] Embodiments of the third aspect of the invention may include one or more features of the first or second aspects of the invention or embodiments thereof, or vice versa.

[057] According to a fourth aspect of the invention, a system for managed pressure drilling in a riser is provided comprising: an upper riser assembly comprising: an upper riser disconnect assembly; a rotary control device; and Petition 870250090587, dated 03 / 10 / 2025, page 20 / 103 11 / 41 at least one flow meter assembly, wherein at least one flow meter assembly is mounted on the upper riser assembly.

[058] The upper riser assembly may comprise a sliding joint. The upper riser assembly may comprise a riser isolation device. The riser isolation device may be mounted on the upper riser disconnection assembly above the upper riser disconnection assembly.

[059] The upper riser assembly can be connected to a lower riser. The upper riser assembly can be connected to a lower riser by connecting the upper riser disconnect assembly to a riser. The upper riser assembly can be connected to a riser above a riser tension ring.

[060] The system may comprise at least one choke assembly. At least one choke assembly may be mounted on the upper riser assembly. At least one choke assembly may be mounted on the sliding joint.

[061] At least one choke assembly and / or at least one flow meter assembly may form part of a managed pressure drilling manifold. The managed pressure drilling manifold may be mounted on the upper riser assembly and / or sliding joint.

[062] The upper riser assembly and / or the sliding joint may comprise a self-contained well control system. The self-contained well control system may comprise at least one flow meter, at least one choke assembly and / or an integrated flow spool.

[063] The riser isolation device, at least one flow meter, at least one choke assembly, rotary control device and / or the managed pressure drilling manifold may be located above the upper riser disconnect assembly.

[064] Provide at least a flow meter and / or at least one set of Petition 870250090587, dated 03 / 10 / 2025, page 21 / 103 12 / 41 throttling and RCD in the upper riser assembly eliminates the need for surface MPD flow meters and throttling manifolds.

[065] At least one flow meter assembly may form part of a managed pressure drilling manifold. The managed pressure drilling manifold may comprise at least one flow meter module, at least one choke module and / or at least one valve assembly. The at least one flow meter module, at least one choke module and / or at least one valve assembly are mounted on the upper riser assembly.

[066] At least one flow meter, valve manifold and / or at least one valve assembly may be mounted on an external surface of the sliding joint on the upper riser assembly.

[067] Embodiments of the fourth aspect of the invention may include one or more features of the first, second or third aspects of the invention or embodiments thereof, or vice versa.

[068] According to a fifth aspect of the invention, a system for managed pressure drilling in a riser is provided comprising: a riser assembly comprising a rotary control device; and at least one flow meter assembly, wherein at least one flow meter assembly is mounted on the riser.

[069] The riser assembly may comprise a slip joint. At least one flow meter may be mounted on the slip joint. The riser assembly may comprise a riser isolation device. The riser may comprise an upper riser disconnect assembly. The slip joint may be a recoverable slip joint.

[070] The system may comprise at least one set of Petition 870250090587, dated 03 / 10 / 2025, page 22 / 103 13 / 41 choke. At least one choke assembly may be mounted on the riser. At least one choke assembly may be mounted on the sliding joint.

[071] The system may comprise an integrated flow spool, throttling manifold and / or measuring manifold in the sliding joint.

[072] At least one choke assembly and / or at least one flow meter assembly may form part of a managed pressure drilling manifold. The managed pressure drilling manifold may be mounted on the upper riser assembly and / or sliding joint.

[073] At least one set of flow meter, valve manifold and / or at least one valve may be mounted on an external surface of the sliding joint on the riser.

[074] The riser isolation device, rotary control device and / or managed pressure drilling manifold may be located on a riser above a riser tension ring.

[075] The upper riser disconnect assembly can be configured to be connected to a tension joint above the tension ring.

[076] Preferably, the upper riser assembly comprising riser isolation device, rotary control device and managed pressure drilling manifold can be removablely connected to the lower riser assembly via the upper riser disconnect assembly.

[077] Embodiments of the fifth aspect of the invention may include one or more features of the first to fourth aspects of the invention or embodiments thereof, or vice versa.

[078] According to a sixth aspect of the invention, a measuring manifold is provided for use in a riser comprising: at least one flow meter; Petition 870250090587, dated 03 / 10 / 2025, page 23 / 103 14 / 41 where the measuring manifold is mountable on the riser.

[079] The measuring manifold may be mountable on the sliding joint. The measuring manifold may be connected to at least one choke assembly that is mountable on the riser and / or sliding joint. The measuring manifold may be connected to at least one flow spool. The measuring manifold, at least one choke assembly and at least one flow spool may be an integrated unit. The integrated unit mountable on the riser and / or sliding joint.

[080] Embodiments of the sixth aspect of the invention may include one or more features of the first to fifth aspects of the invention or embodiments thereof, or vice versa.

[081] According to a seventh aspect of the invention, a managed pressure collector for managed pressure drilling is provided comprising: at least one flow meter; where the managed pressure manifold is mounted on the riser.

[082] The managed pressure manifold may comprise at least one throttling assembly. The managed pressure manifold may comprise at least one flow spool. The at least one throttling assembly, at least one flow meter and at least one flow spool may be an integrated unit.

[083] The managed pressure manifold can be mounted on the sliding joint. The integrated flow spool, choke assembly and flow meter manifold can be mounted on a sliding joint.

[084] Embodiments of the seventh aspect of the invention may include one or more features of the first to sixth aspects of the invention or embodiments thereof, or vice versa.

[085] According to an eighth aspect of the invention, a method is provided for installing a well control riser system on a subsea riser. Petition 870250090587, dated 03 / 10 / 2025, page 24 / 103 15 / 41 comprising: Provide a riser assembly and install at least one flow meter assembly on the riser.

[086] The method may involve installing at least one choke assembly on the riser.

[087] The method may comprise installing a riser isolation device above a tension ring on the riser. The method may comprise installing a riser isolation device on the riser column above the tension ring.

[088] The method may comprise supplying a valve assembly and / or a distribution assembly.

[089] The method may comprise making a tension ring. The method may comprise connecting the tension ring to the riser, riser isolation device, sliding joint and / or the upper riser disconnection assembly.

[090] The method may comprise mounting at least one flow meter assembly and at least one choke assembly on at least one component of the upper riser assembly. The method may comprise installing the upper riser assembly connected with at least one flow meter assembly and / or at least one choke assembly on the riser.

[091] The method may comprise mounting at least one flow meter assembly and at least one throttling assembly on the sliding joint.

[092] The method may comprise installing the upper riser disconnect assembly on the riser string above the tension ring.

[093] Embodiments of the eighth aspect of the invention may include one or more features of the first to seventh aspects of the invention or embodiments thereof, or vice versa.

[094] According to a ninth aspect of the invention, a method is provided for installing a pressure-managed drilling system on a riser. Petition 870250090587, dated 03 / 10 / 2025, page 25 / 103 16 / 41 submarine comprising: provide a riser assembly; Install a rotary control device; and install at least one flow meter assembly on the riser.

[095] The method may comprise installing an upper riser disconnect assembly above the tension ring. The method may comprise installing the rotary control device and at least one flow meter assembly above the upper riser disconnect assembly.

[096] The method may involve installing a riser isolation device above the voltage ring.

[097] The method may comprise installing at least one throttling assembly, at least one valve assembly and / or one distribution assembly. The method may comprise installing at least one integrated flow meter, at least one throttling assembly and a flow spool on the riser or sliding joint. The method may comprise making the tension ring. The method may comprise connecting the tension ring to the riser below the upper riser disconnect assembly.

[098] The method may comprise installing the upper riser disconnect assembly on the riser string and then installing the rotary control device on the upper riser disconnect assembly.

[099] The upper riser assembly including sliding joint, managed pressure drilling manifold, RCD and RID can be installed on the lower riser by locking removablely onto the upper riser disconnect assembly.

[0100] Embodiments of the ninth aspect of the invention may include one or more features of the first to eighth aspects of the invention or embodiments thereof, or vice versa.

[0101] According to a tenth aspect of the invention, a method is provided. Petition 870250090587, dated 03 / 10 / 2025, page 26 / 103 17 / 41 conversion of a marine riser for well control operations comprising: Provide a riser assembly and install at least one flow meter assembly on the riser.

[0102] The method may comprise installing at least one choke assembly on the riser. The method may comprise installing an upper riser assembly on the riser with at least one flow meter assembly and / or at least one choke assembly mounted on the upper riser assembly.

[0103] The method may comprise installing a sliding joint on the riser with at least one flow meter assembly, at least one choke assembly and / or an integrated flow spool mounted on the outer surface of the sliding joint. The method may comprise removing an existing sliding joint and / or an inner cylinder of the existing sliding joint on the subsea riser.

[0104] Embodiments of the tenth aspect of the invention may include one or more features of the first to ninth aspects of the invention or embodiments thereof, or vice versa.

[0105] According to an eleventh aspect of the invention, a method is provided for converting a marine riser for MPD operations enabling managed pressure subsea drilling operations comprising: Install a rotary control device; and at least one flow meter assembly on the riser.

[0106] The method may comprise installing at least one choke assembly on the riser and / or the sliding joint.

[0107] The method may comprise installing at least one choke assembly on the riser. The method may comprise installing an upper riser assembly on the riser with at least one flow meter assembly and / or at least one choke assembly mounted on the upper riser assembly. Petition 870250090587, dated 03 / 10 / 2025, page 27 / 103 18 / 41

[0108] The method may comprise installing a sliding joint on the riser with at least one flow meter assembly, at least one throttling assembly and / or an integrated flow spool mounted on the outer surface of the sliding joint.

[0109] The method may comprise removing an existing sliding joint and / or an existing sliding joint inner cylinder in the subsea riser.

[0110] Embodiments of the eleventh aspect of the invention may include one or more features of any of the first through tenth aspects of the invention or embodiments thereof, or vice versa.

[0111] According to a twelfth aspect of the invention, a method is provided for measuring at least one parameter or property of drilling fluid in the subsea riser comprising: to provide a riser assembly comprising: at least one set of flow meters; where at least one set of flow meters is mounted on the riser; to measure at least one parameter or at least one property of the drilling fluid in the riser.

[0112] The method may comprise generating a measurement signal to a control unit. The method may comprise analyzing the measurement signal in the control unit to compare at least one parameter with a desired range of operating parameters.

[0113] The method may comprise generating a control signal from the control unit when at least one parameter is determined to be outside the desired range of operating parameters.

[0114] The method may comprise analyzing the measurement signal in the control unit to monitor the flow of drilling fluid in the riser and / or in at least one mud return line. Petition 870250090587, dated 03 / 10 / 2025, page 28 / 103 19 / 41

[0115] The method may comprise monitoring at least one parameter or at least one property of the drilling fluid or drilling fluid flow in the riser and / or in at least one mud return line.

[0116] At least one flow meter may be a differential pressure flow meter.

[0117] The method may comprise measuring a differential pressure using a differential pressure flow meter ΔP. The method may comprise measuring a line pressure drop due to friction APf along a length L of pipe.

[0118] The method can understand and calculate the quantity APf / ΔP and thus calculate one or more properties of the drilling fluid flow.

[0119] The method may comprise determining or calculating a friction factor. The method may comprise calculating the flow discharge coefficient, Reynolds number, density, viscosity and / or flow rate of the drilling fluid.

[0120] The method may involve calculating a corrected operational value of the calculated Reynolds number. The method may involve calculating the discharge coefficient of the Reynolds number, where the Reynolds number is determined from the calculated friction factor.

[0121] The method may comprise determining or calculating a Reynolds number for the drilling fluid flow. The method may comprise making additional measurements to monitor a change in the drilling fluid. The method may comprise correcting the corrected Reynolds number as the fluid properties change. The method may comprise correcting the corrected Reynolds number based on the minimum of additional measurements taken.

[0122] The method may involve comparing at least one parameter with a desired range of operational parameters.

[0123] The method may involve calculating, estimating, or predicting density. Petition 870250090587, dated 03 / 10 / 2025, page 29 / 103 20 / 41 and / or viscosity of the drilling fluid in flow.

[0124] The method may comprise measuring at least one parameter or at least one property of the fluid using two or more flow meters. The method may comprise switching between a first flow meter having a first flow measurement range to a second flow meter having a second flow measurement range.

[0125] The method may comprise the use of knowledge of riser geometry, geometry of at least one flow meter, pipe or tubing geometry, prior knowledge of the discharge coefficient as a function of the friction factor and / or Reynolds number to calculate or estimate information on the drilling fluid. The method may include estimating or calculating the friction factor, Reynolds number, discharge coefficient, density, viscosity, and corrected flow rate.

[0126] Embodiments of the twelfth aspect of the invention may include one or more features of any of the first to eleventh aspects of the invention or their embodiments, or vice versa.

[0127] According to a thirteenth aspect of the invention, a method for measuring a property of drilling fluid in a subsea drilling operation is provided, comprising: to provide a riser assembly comprising; a riser isolation device; a rotary control device; at least one flow meter mounted on the riser; and divert drilling fluid from the riser to at least one flow meter.

[0128] The method may comprise diverting drilling fluid from the riser below the rotary control device. The method may comprise diverting, measuring and / or throttling returns of drilling fluid from the riser below the rotary control device back into the riser through at least one flow meter. Petition 870250090587, dated 03 / 10 / 2025, page 30 / 103 21 / 41

[0129] The method may involve the use of the existing sludge return system. The method may involve the use of the existing diversion system and flow lines to reach the agitators.

[0130] Embodiments of the thirteenth aspect of the invention may include one or more features of any of the first to twelfth aspects of the invention or embodiments thereof, or vice versa.

[0131] According to a fourteenth aspect of the invention, a method of managed pressure drilling in a subsea drilling operation is provided comprising: to provide a riser assembly comprising; a riser isolation device; a rotary control device; at least one flow meter mounted on the riser; at least one choke assembly mounted on the riser; Measure flow properties and activate the throttle to control flow.

[0132] The method may comprise diverting drilling fluid below the rotary control device. The method may comprise diverting, metering and / or throttling the drilling fluid returns from the riser below the rotary control device and back into the riser (low pressure) via external low lines including at least one flow meter and at least one throttling assembly.

[0133] The method may comprise the use of the existing slurry return system. The method may comprise the use of the existing diversion system and flow lines to reach the agitators. The method may comprise diverting high-pressure MPD returns from below the RCD back into the riser (low pressure) via flow lines including at least one flow meter and at least Petition 870250090587, dated 03 / 10 / 2025, page 31 / 103 22 / 41 a choke point assembly. The method can utilize existing mud return lines for agitators.

[0134] Embodiments of the fourteenth aspect of the invention may include one or more features of any of the first to thirteenth aspects of the invention or embodiments thereof, or vice versa.

[0135] According to a fifteenth aspect of the invention, a method is provided for measuring at least one parameter or property of drilling fluid in a subsea riser comprising: to provide a well control system for a riser comprising a riser assembly; at least one flow meter; wherein at least one flow meter is located on an external surface of the riser assembly above a riser tension ring; and measures at least one parameter or at least one property of the drilling fluid in the riser.

[0136] Embodiments of the fifteenth aspect of the invention may include one or more features of any of the first to fourteenth aspects of the invention or their embodiments, or vice versa.

[0137] According to a sixteenth aspect of the invention, a method of managed pressure drilling in a subsea drilling operation is provided comprising providing a well control system for a riser assembly comprising a riser assembly; at least one flow meter; wherein at least one flow meter is located on an external surface of the riser assembly above a riser tension ring; and provides a rotary control device; and Petition 870250090587, dated 03 / 10 / 2025, page 32 / 103 23 / 41 measure at least one drilling fluid flow property using at least one flow meter.

[0138] Embodiments of the sixteenth aspect of the invention may include one or more features of any of the first to fifteenth aspects of the invention or their embodiments, or vice versa. Brief Description of the Drawings

[0139] Several embodiments of the invention will now be described, by way of example only, with reference to the drawings, of which: Figure 1 is a representation of a managed pressure drilling (MPD) riser assembly according to the prior art; Figure 2 is a schematic representation of a riser system for MPD according to a first embodiment of the invention; Figures 3A to 3F are schematic representations of an upper riser assembly for the riser system shown in Figure 2; Figure 4 is a schematic cross-sectional view of a flow meter used in the riser assembly of Figure 2; Figure 5 is a flow diagram of the mud flow measurement and monitoring process according to an embodiment of the invention; and Figure 6 is a flow diagram of the process for measuring different mud flow parameters according to an embodiment of the invention. Detailed Description of Preferred Options

[0140] Figure 1 shows a schematic representation of a drilling system for managed pressure drilling of a known subsea reservoir in the prior art.

[0141] The drilling system 10 comprises a riser assembly 12 located between a drilling rig 13 and a wellhead. The system 10 has a riser flow spool (RFS) 16, a riser isolation device (RID) Petition 870250090587, dated 03 / 10 / 2025, page 33 / 103 24 / 41 18, a rotary control device (RCD) 20 mounted on the riser.

[0142] Riser 12 is connected to a sliding joint 14. The sliding joint 14 is configured to respond to the lifting motion of the platform during dynamic sea conditions.

[0143] A portion of platform 13 is shown, which may be a floating rig or drilling vessel. The platform supports the drilling system 10. A plurality of tensioning cylinders 19 are fixed to the platform and exert an upward force on the rods or cables 22. The lower end of each rod or cable 22 is connected to a riser tensioning ring 24 which is connected to maintain the stability of the drilling system 10 in the offshore environment.

[0144] External auxiliary lines 26 are connected to the BOP (not shown) and circulate fluids and provide control lines to the BOP. A termination ring 28 is circumferentially arranged around a portion of the sliding joint 14. The auxiliary lines 26 terminate at the termination ring. Flexible hoses 30 are connected to the termination ring 28 and extend the coupling upwards to the platform. The hoses 30 have been truncated in these drawings for clarity. The termination joint 28 provides fluid communication between the auxiliary lines 26 and the flexible hoses 30.

[0145] The RFS 16 has two drilling fluid return flow lines 32 and 34 in fluid communication with a distribution manifold 40 that directs the flow to an MPD manifold 41 located on the surface to allow back pressure of the applied drilling fluid.

[0146] The MPD 41 collector includes a debris collector 42 to capture and trap debris in the fluid, a measuring collector 44 to measure fluid flow rates and density, and a throttling collector 46 to control balanced and unbalanced fluid return rates and wellhead pressure during MPD operations. Petition 870250090587, dated 03 / 10 / 2025, page 34 / 103 25 / 41

[0147] Fluid returns are processed through a gas mud separator (MGS) or rig gas mud separator that separates the gas from the drilling fluid. The gas is vented to be flared or stored in an underground formation.

[0148] The fluid is then returned to the drill string in the riser assembly by means of a mud pump (not shown) to be recirculated in the drilling rig.

[0149] During a managed pressure drilling operation, the RCD 20 provides a rotating internal sealing element that seals against the drill string to create a watertight barrier to establish a closed system and divert the flow from the riser to the surface MPD manifold. The closed system allows dynamic adjustments to well pressure, precise flow rate measurement, and safer separation of gas from mud. The measuring manifold 44 measures fluid flow rates, and the throttling manifold 46 allows control of annular pressure by increasing or decreasing the annular flow.

[0150] Figure 2 schematically shows characteristics of a pressure drilling management system 100 according to a first embodiment of the present invention. It will be evaluated that the drilling system can adopt different configurations depending on the type of riser system in which it is being installed and the type of drilling operation. Figure 2 represents one possible configuration that the MPD system can adopt.

[0151] The drilling system 100 comprises a riser assembly 112. The system 100 has a riser isolation device (RID) 118, a rotary control device (RCD) 120 and an upper riser disconnection assembly (URD) ​​150 mounted on the riser below a sliding joint 114. The sliding joint 114 is configured to respond to the lifting motion of the platform during dynamic sea conditions. Petition 870250090587, dated 03 / 10 / 2025, page 35 / 103 26 / 41

[0152] The 150 top riser disconnect assembly allows for quick separation of the 112a top riser section including RID, RCD and sliding joint from the 112b bottom riser section.

[0153] Tension ring 124 is arranged circumferentially around a tension joint 125 located between the quick disconnect assembly 150 and the lower riser section 112b. Although in this example the tension ring 124 is connected to the tension joint 125, it may alternatively be connected to an existing external probe cylinder located between the quick disconnect assembly 150 and the riser 112. In this example, the riser isolation device, a rotary control device 120, and an upper riser disconnect assembly 150 are arranged above the tension ring 124.

[0154] Tension cylinders are fixed to the platform and exert an upward force on the rods or cables 122. The lower end of each rod or cable 122 is connected to a riser tension ring 124 which is connected to maintain the stability of the riser column. For clarity, the cables 122 are truncated and the platform is not shown in Figure 2.

[0155] In this example the sliding joint is a three-part telescopic sliding joint. However, it is appreciated that other types of sliding joints can be used. The sliding joint allows the riser system to adjust in length as the platform rises in response to wave motion.

[0156] External auxiliary lines 126 are connected to the BOP (not shown) and circulate fluids and provide control lines to the BOP. A termination ring 128 is circumferentially arranged around a portion of the lower riser section 112b. The auxiliary lines 126 terminate at the termination ring 128. Flexible hoses 130 are connected to the termination ring 28 and extend the coupling upwards to the platform. The hoses 130 have been truncated in these drawings for clarity. The termination joint 128 provides fluid communication between the Petition 870250090587, dated 03 / 10 / 2025, page 36 / 103 27 / 41 auxiliary lines 126 and flexible hoses 130.

[0157] An MPD manifold system 141 is located on an external surface of the riser string above the quick disconnect assembly 150 as best shown in Figures 3A to 3E. In this example, the managed pressure manifold 141 is located on the external surface of part of the sliding joint 114. The MPD manifold system is a well control system.

[0158] The MPD manifold system comprises flow lines 132 and 134. Flow line 132 comprises spool 162a, double isolation valve 164a, an in-line flow meter 166a, choke 168a and return spool 170a in the riser bore. Flow line 132 comprises spool 162b, double isolation valve 164b, an in-line flow meter 166b and choke 168b and return spool 170b in the riser bore.

[0159] During MPD, MPD 141 collector system directs drilling fluid from the riser hole below the RID and RCD (high pressure upstream RCD) into MPD 132 and 134 flow lines, respectively.

[0160] The MPD 141 manifold system includes in-line flow meters 166a, 166b and choke assemblies 168a, 168b in flow lines 132, 134 respectively which are mounted on the riser and connected to the riser bore below RCD 120. The in-line flow meters 166a, 166b measure drilling fluid flow rates and density. The choke assemblies 168a, 168b allow control of annular pressure by increasing or decreasing the annular flow. The MPD collector system 141 diverts flow below RCD 120, meters and throttles MPD returns back to the riser via external MPD flow lines 132 and 134. This allows fluid returns to utilize existing mud return systems in an upper riser section 112a including the diverter system and flow lines to agitators.

[0161] The flow meter and throttle assemblies are Petition 870250090587, dated 03 / 10 / 2025, page 37 / 103 28 / 41 sized so that they can be mounted on the sliding joint without affecting the operation of the sliding joint.

[0162] MPD manifold system components including flow meters and throttling assemblies are remotely controlled. The flow meters and throttling assemblies can be automatically controlled by electronic or hydraulic monitoring equipment and / or slimline actuators.

[0163] Drilling fluid re-enters the riser bore at the bottom of the slip joint 114 and flows into the riser return system including the diverter.

[0164] The MPD 141 collector system has a third 180° return flow line with a bypass installation shown in Figure 3E. The 180° flow line is a safety system to operate as a riser overpressure protection (VRP) line with automated choke controls. This flow line allows the flow meter and choke assembly on flow lines 132 and 134 to be isolated and bypassed when not needed, such as when drilling the shoe.

[0165] During a managed pressure drilling operation, the RCD 20 provides a rotating internal sealing element that seals against the drill string to create a watertight barrier to establish a closed system and divert flow from the riser to the surface MPD collector. The closed system allows for dynamic adjustments to well pressure, precise flow measurement, and safer separation of gas from mud.

[0166] Fluid returns are processed through a gas mud separator (GMS) or the platform's gas mud separator which separates the gas from the drilling fluid. The gas is vented, flared, or stored in an underground formation. The fluid is then returned to the drill string via the mud pump to be recirculated in the drilling rig.

[0167] In the event of a gas kick, the annular BOP (not shown) located Petition 870250090587, dated 03 / 10 / 2025, page 38 / 103 Valve 29 / 41 on the lower riser is closed to seal around the drill string. Valve 118 is closed around the drill string to isolate the upper riser system and allow any gas in the riser to be contained.

[0168] Any isolated gas can be circulated through flow lines 132 and 134 via the choke manifold to maintain back pressure in the riser, allowing the gas to circulate in a controlled manner to the MGS to capture and separate large volumes of free gas from the mud. The gas, once separated from the mud, is then safely vented.

[0169] As best shown in Figure 3D, a flow line 172 is directed from the annular body and vents at the lower end of the sliding joint 114 outer barrel 114a to allow bleeding and equalization of RCD 120.

[0170] Figure 3F shows an optional 190 booster line inlet manifold with 192 and 194 valves for 196 booster line on a lift joint (or telescopic joint outer barrel). The booster line inlet manifold allows non-intrusive pumping 'through the top' of the lift string for Pressurized Mud Cap Drilling (PMCD) using existing booster pump and booster line. The 190 booster line inlet manifold allows flushing of the RCD and the upper end of the riser during connections. This manifold does not require an additional Coflexip booster hose (for MPD or PMCD).

[0171] Although in the example above the MPD manifold including the flow meters and choke assemblies are described as being located or mounted on an external surface of the riser telescopic joint, it will be assessed that the MPD manifold, flow meters and / or choke assemblies may be located or mounted, located or connected to a riser joint.

[0172] Figure 4 shows a schematic cross-sectional view of an in-line flow meter for use in the MPD manifold mounted on or located in the riser assembly. The flow meter is a differential pressure flow meter. Petition 870250090587, dated 03 / 10 / 2025, page 39 / 103 30 / 41 which relies on the use of flow adjustment elements such as an obstruction or expansion in the pipe, to create a pressure drop for measuring the volume of fluid passing through a flow meter. The flow adjustment can be created by an orifice plate, wedges, venturi, Coriolis, cones and / or hole reduction as in process equipment. By measuring the differential pressure between a point immediately upstream of the obstruction / expansion and a point downstream of the obstruction / expansion where the pressure has changed due to the obstruction / expansion, the volumetric or mass flow rate can be determined.

[0173] In this example, the flow meter is a venturi flow meter. However, it will be evaluated what other types of flow meters can be used.

[0174] The volumetric or mass flow rate can be derived from the differential pressure using Bernoulli's theorem, which is based on the conservation of energy within a flowing fluid and a discharge coefficient. The flow meter has a reduced cross-sectional area in the fluid flow path, thus creating a pressure differential on opposite sides of the flow-adjusting member, i.e., the venturi member.

[0175] The pressure differential created on opposite sides of the flow adjustment member has a known mathematical relationship with the flow rate of the fluid passing through it and, provided the cross-sectional area at the venturi opening is constant, fluid flow measurements are very accurate.

[0176] For all types of differential pressure flow rate meters, the density of the fluid being measured is also required to complete the calculation of the mass or volumetric flow rate.

[0177] The flow restrictor member is mounted on an inner surface of the pipe to restrict fluid flow through the pipe and process a pressure drop in the fluid as it flows through the flow restrictor member.

[0178] Figure 4 shows a schematic cross-sectional view of Petition 870250090587, dated 03 / 10 / 2025, page 40 / 103 31 / 41 flow meter 200 for use in MPD drilling system. The flow meter 200 has a tubular housing 210 having an internal bore 212 extending longitudinally through it providing a fluid passage 213 in which a flow adjustment member 214 is mounted on the inner surface 211a of the wall 211 of the housing 210. In this example, the flow adjustment member is a venturi member 214 comprising a venturi section 220.

[0179] Venturi section 220 has an upstream section 222 that converges into a coaxial reduced-diameter venturi throat section 224 that expands into a coaxial diverging downstream section 226.

[0180] The flow meter 200 has four ports 228a, 228b, 228c and 228d in the wall of the housing 211 which are in fluid communication with the flow through passage 213. Port 220a is located in wall 211 at a position 227 upstream of venturi section 220, port 228b is located in wall 211 of venturi section upstream 222, port 228c is located in wall 211 of throat section and port 228d is located in wall 211 of downstream section.

[0181] Ports 228a, 228b, 228c and 228d are pressure ports to receive a pressure sensing device to measure the pressure of the fluid flowing through the venturi which allows the detection and measurement of a pressure differential induced by the fluid flow through the reduced diameter venturi throat section 224.

[0182] A temperature measuring device 230 is mounted on the wall of the housing 211 in fluid communication with the flow through the passage 213. In the example shown, the temperature measuring device is located downstream of the venturi, but it will be considered that the temperature measuring device may be located upstream of the venturi. The temperature measuring device may be located in the upstream, downstream or throat section of the flow meter. The flow meter may have several temperature measuring devices located in a different section of the flow meter. Petition 870250090587, dated 03 / 10 / 2025, page 41 / 103 32 / 41

[0183] Changes in temperature and / or pressure of the fluid being measured can cause the inner diameter of the passage to expand or contract. Changes in the size of the inner diameter of the passage through the flow rate meter can have a substantial change in the pressure drop of the fluid flowing through the venturi. This can result in inaccurate measurements.

[0184] In use, the fluid flows in the direction indicated by arrow A. Although the fluid in Figure 4 is shown flowing in direction A, it will be appreciated that the flow meter can also operate in the opposite direction. The flow meter can be installed in a riser pipe or hose in any orientation without affecting the operation or accuracy of the measurement readings.

[0185] The tubular body 210 has a flange 213 at each longitudinal end 210b of the body 210. The flanges 213 have connection means, such as holes, for connecting the flow meter 200 to piping tubes or piping hoses.

[0186] The diameter of the throat section is smaller than the diameter of the upstream or downstream section, thus restricting the flow of fluid through the passage. In use, the flow meter is connected to a hose to measure the flow of drilling fluid through it.

[0187] It will be appreciated that different flow adjustment devices can be used as an alternative to a venturi. It will also be appreciated that different restrictor shapes, sizes, and configurations can be used to adjust and optimize the conditions and performance of the fluid flow meter.

[0188] Pressure measurements are taken at pressure ports 228a and 228b to calculate the line pressure drop due to friction ΔPf along a length L of pipe. Pressure measurements taken at pressure ports 228b and 228c allow a pressure differential ΔPt to be measured. Pressure measurements taken at pressure ports 228c and 228d allow a differential of Petition 870250090587, dated 03 / 10 / 2025, page 42 / 103 33 / 41 pressure ΔΡγ should be measured.

[0189] The quantity ΔPί / ΔPί can be calculated later, allowing the online calculation of various flow properties. The pressure drop due to friction in the pipe can be expressed as equation 1 and is valid for all Reynolds numbers. ΔρWl > 2D

[0190] Equation 1 where λ is the friction factor, ρ is the density in kg / m3, μ is the tube velocity, D is the tube diameter.

[0191] Combining Equation 1 with the Hagen-Poiseuille equation and rearranging the velocity in terms of pressure drop, it is possible to derive the friction factor in laminar flow as λ = —

[0192] Equation 2Rewhere Re is the Reynolds number

[0193] Equation 2 shows that in laminar flow, the friction factor is inversely proportional to the Reynolds number only. This suggests that measuring the friction factor in the laminar flow region will allow a direct calculation of the Reynolds number. It follows that if the discharge coefficient is repeatable in laminar flow, it can be accurately correlated with the Reynolds number or the friction factor itself to provide in-line corrections.

[0194] It is not only laminar flow where the friction factor is dependent on the Reynolds number. There are several well-known correlations for the friction factor in turbulent flows, for example, the Colebrook-White equation, which would play a similar role to equation 2. In these cases, the dependence on the Reynolds number is not linear, but the same process can be used to calculate the discharge coefficient.

[0195] The friction factor and differential pressure flow measurement are important contributors to the invention. Petition 870250090587, dated 03 / 10 / 2025, page 43 / 103 34 / 41

[0196] The beta ratio β of the flow rate meter is the ratio between the pipe diameter and the throat diameter. The inclusion of a parameter known as the Discharge Coefficient helps to remove errors associated with the location of pressure measurements.

[0197] Finally, a term to correct for fluid expansibility ε is included with ε equal to 1 for incompressible fluids.

[0198] The volume flow through the venturi of the flow meter (in this case) is therefore,

[0199] Equation 3 nd2I------Q = Çd£ ~ Where Q is the flow volume, and Cd is the discharge coefficient.

[0200] Providing a flow meter measurement system that combines the differential pressure flow equation (equation 3) with the friction factor equation (equation 2) allows the fluid properties to be calculated.

[0201] The pressure measurement reading is used to measure a pressure drop, APt, across the differential pressure gauge. In addition, the pressure drop, APf, due to friction along a straight length of pipe is measured. The use of these two measurements can facilitate the calculation of various fluid properties.

[0202] By measuring the pressure drop ΔΡΧ through the differential pressure gauge and the pressure drop APf along a length of pipe, and with knowledge of the geometry of the pipe and the gauge, it is possible to calculate the in-line friction factor using equations 4 and 5 &Pr λ Equation 41

[0203] Equation 4 shows two terms, one a ratio of two differential pressure measurements and two a constant relating to the geometry of the meter, tube length and discharge coefficient. Petition 870250090587, dated 03 / 10 / 2025, page 44 / 103 35 / 41 _ D(l- / ?4) Equation 5

[0204] Equation 5 provides a repeatable correlation for the friction factor that is independent of the physical properties of the fluid.

[0205] In practice, this calculation method can only be performed using two real-time differential pressure measurements. The low uncertainty of these measurements is subject to regular calibrations and maintenance procedures.

[0206] This can be done by calibrating and characterizing the flow rate meter and the measurement system.

[0207] Knowledge of the geometry of the piping and the flow adjustment member is also necessary, as well as an indication of the system performance, i.e., the discharge coefficient over the usable Reynolds number range and therefore the friction factor range.

[0208] Characterization and calibration allows the establishment of an equation or similar to relate the discharge coefficient as a function of the friction factor or to relate the discharge coefficient (Cd) as a function of the Reynolds number (Re).

[0209] Using the relationship established between the flow coefficient and the friction factor or Reynolds number with equation 4, it is possible to determine the friction factor, Reynolds number, and flow coefficient for the measurement system.

[0210] This can be achieved using an iterative approach. Alternatively, this can be obtained using the calculated friction factor or the Reynolds number value with the theoretical or reference value.

[0211] A simple ratio between the calculated and reference values ​​allows the calculation of a corrected friction factor and a corrected Reynolds number, as shown in equations 6 and 7, respectively. This allows the alignment or matching of measured values ​​with calculated values. Petition 870250090587, dated 03 / 10 / 2025, page 45 / 103 36 / 41 τ _ içhe τ Άογ—τAcalcAcahb Equation 6

[0212] Where Àcaiib is the friction factor value calculated during calibration, Àcaic is the friction factor calculated during operation, Àthe is the theoretical friction factor for the reference Reynolds number. Reco,. =-^-Reca / c Equation 7

[0213] Re caiib is the Reynolds number calculated during calibration, Recaic is the Reynolds number calculated during calibration and Reref is the Reynolds reference number during calibration.

[0214] Using the friction factor method, the correct discharge coefficient can be calculated independently of the physical properties of the drilling fluid. Equation 3 can now be used to calculate the corrected volumetric flow rate of the fluid.

[0215] Figure 5 is a flow diagram of the process steps in determining the flow properties of drilling fluid using a flow meter according to an embodiment of the invention.

[0216] Referring to Figure 5, firstly, a known relationship between the discharge coefficient and the Reynolds number is obtained for the meter geometry (Step 1). Using the flow meter, the differential pressure, APt, across the differential pressure gauge and the pressure drop APf along a length of pipe are measured (Step 2).

[0217] The friction factor is calculated using equation 4 (Step 3). In some implementations, this may involve calculating a corrected value of the friction factor as set out in equation 6.

[0218] The friction factor is used to calculate a value for the Reynolds number of the flow, for example, using equation 2. In some implementations, this may involve calculating a corrected value of the Reynolds number as Petition 870250090587, dated 03 / 10 / 2025, page 46 / 103 37 / 41 established in equation 7 (Step 4).

[0219] The discharge coefficient is calculated using the calculated or corrected Reynolds number value (Step 5). Step 6 shows an iterative process for calculating the discharge coefficient value, using the friction factor from Step 3 in some embodiments.

[0220] The fluid density is established by sampling, consulting tables or another appropriate method (Step 7). The established density value is used to calculate a fluid flow rate using equation 3 (Step 8).

[0221] If the friction factor and discharge coefficient are known, then it is possible to infer the density of the drilling fluid in real time using equation 1. In this equation, the unknowns are the density and velocity of the drilling fluid; the equation can be rearranged in terms of density. The velocity can be measured using a known measuring device, such as an ultrasonic meter. The measured velocity can then be used to calculate the density.

[0222] Alternatively, by combining equations 1 and 3, there are two equations with two unknowns. It is possible to iterate over these two values ​​to provide a density and a volumetric flow rate correction. This can be applicable when indications of a target density are known.

[0223] As with the friction factor, density correction can be done during the initial calibration of the meter using equation 9. Pref Pcor ~ PcalcΛPcalib Equation 9 where pcor is the corrected density, pref is the reference density during calibration, pcaiib is the density calculated during calibration, and pcaic is the density calculated during operation.

[0224] When the density of the drilling fluid is known, it is still possible to calculate the viscosity of the drilling fluid (μ). Knowledge of the density, pipe diameter, velocity and Reynolds number (derived from the factor of Petition 870250090587, dated 03 / 10 / 2025, page 47 / 103 38 / 41 friction) allows viscosity to be calculated using the standard Reynolds number (Re) calculation equation, as shown in equation 10. μ=^ Re Equation 10

[0225] Figure 6 shows a flow diagram of the calculation of additional flow properties of the drilling fluid using the techniques shown above.

[0226] Steps 1 to 6 and 8 of Figure 6 will be understood from the description in Figure 5 above. However, Step 7 differs because the density is calculated from knowledge of a target density or a velocity measurement using equation 1 (Step 9). In some embodiments, the value of the flow rate calculated in Step 8 can be iterated back into the density calculation in Step 7.

[0227] In Step 10, viscosity is calculated using equation 10. This calculation can use a measured velocity or the equivalent flow rate velocity calculated in Step 8. Typically, the calculation would also use the Reynolds number calculated in Step 4 and the density value in Step 7.

[0228] With knowledge of the geometry of the meter and piping and prior knowledge of the discharge coefficient as a function of the friction factor or Reynolds number, it is possible to calculate information including friction factor, Reynolds number, discharge coefficient, density, viscosity and / or a corrected flow rate on the fluid flow from two differential pressure measurements and an indicative pipe velocity only.

[0229] The system may comprise two or more flow meters. Each flow meter may have a different fluid flow range and / or fluid density range. The system may have a flow measurement range of 10 to 2000 USG / min. The system may have a switching mechanism to alternate between different flow meters having different measurement ranges. Petition 870250090587, dated 03 / 10 / 2025, page 48 / 103 39 / 41

[0230] Throughout the specification, unless the context requires otherwise, the terms 'comprises' or 'includes', or variations such as 'comprises' or 'comprises', 'includes' or 'including' will be understood as implying the inclusion of a declared integer or group of integers, but not the exclusion of any other integer or group of integers.

[0231] Furthermore, relative terms such as lower, upper, up, down, above, below and the like are used in this document to indicate directions and locations as they apply to the accompanying drawings and shall not be construed as limiting the invention and its features to particular arrangements or orientations. The term mounted may include installed, fitted, fixed or located on a surface thereof. The terms collector and assembly may be interchangeable.

[0232] The invention provides a well control system for a riser comprising a riser assembly and at least one flow meter, wherein the flow meter manifold is mounted on the riser.

[0233] The invention can facilitate the conversion of marine riser assemblies for MPD operations that allow conventional and / or managed pressure drilling operations.

[0234] The invention provides a complete autonomous managed pressure drilling system for connection to the riser. It avoids the need for MPD surface equipment and major modifications to the drilling riser equipment. It also reduces the need for any return flow hoses from the riser back to the platform / surface.

[0235] The invention mitigates the need for independent piping upgrades for MPD mud flow and utilizes the existing rig fluid circulation / mud return system and well control procedures. Petition 870250090587, dated 03 / 10 / 2025, page 49 / 103 40 / 41

[0236] By providing a self-contained MPD system on an upper riser string and an upper riser disconnect assembly above the tension ring, the drilling MPD components, flow meter, choke, and distribution manifolds can be installed and / or removed quickly, safely, and easily from the riser assembly without requiring the BOP to be disconnected and the riser string pulled to the surface. This configuration can allow components of a riser assembly and drilling MPD system to be installed only when needed.

[0237] The invention allows a conventional drilling riser to be converted to managed pressure drilling without requiring significant modification to the rig's choke and stop manifolds and vertical pipes. It also avoids the installation of additional return hoses and multiple control lines in the moonpool or the bulky location of distribution, choke, and metering manifolds on the rig. The system also allows high-pressure MPD returns to be diverted from below an RCD back to the riser (low pressure) via flow lines and flow meter and choke assembly.

[0238] The invention provides an integrated flow spool, choke manifold and metering manifold in a recoverable riser sliding joint that can be easily installed and / or removed from a riser assembly.

[0239] The preceding description of the invention has been presented for illustrative and descriptive purposes and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The embodiments described have been chosen and described to better explain the principles of the invention and its practical application, thereby enabling other persons skilled in the art to better utilize the invention in various embodiments and with various modifications suitable for the particular use contemplated. Petition 870250090587, dated 03 / 10 / 2025, p. 50 / 103 41 / 41 Therefore, other modifications or improvements may be incorporated without departing from the scope of the invention intended herein. Petition 870250090587, dated 03 / 10 / 2025, p. 51 / 103

Claims

1 / 4 CLAIMS 1. Well control system (100) for a riser, CHARACTERIZED in that it comprises: a riser assembly (112); and a pressure managed drilling manifold (141) comprising: at least one flow meter (166a, 166b, 200); and at least one choke assembly (168a, 168b); wherein at least one flow meter of the pressure managed drilling manifold (141) is located on an external surface of the riser assembly (112).

2. Well control system (100), according to claim 1, CHARACTERIZED in that the riser assembly (112) comprises at least one valve assembly (164a, 164b, 192, 194) located in the riser assembly (112).

3. Well control system (100), according to claim 1 or 2, CHARACTERIZED in that the riser assembly (112) comprises a rotary control device (120).

4. Well control system (100), according to any one of claims 1 to 3, CHARACTERIZED in that at least one flow meter (166a, 166b, 200) and at least one choke assembly (168a, 168b) are integrated with a flow spool in a riser sliding joint (114).

5. Well control system (100), according to any one of claims 1 to 4, CHARACTERIZED in that at least one flow meter (166a, 166b, 200) is selected from the group comprising orifice plate, wedge, venturi, Coriolis, Pitot tubes, differential pressure flow meter and / or variable area flow meters.

6. Well control system (100), according to any one of claims 1 to 5, CHARACTERIZED in that it comprises a control unit configured to receive at least one measurement signal from at least one flow meter (166a, 166b, 200) to measure at least one parameter or at least one property of drilling fluid or drilling fluid flow in the riser (112) and / or in at least one mud return line.

7. Well control system (100), according to claim 6, CHARACTERIZED in that the control unit is configured to monitor drilling fluid flow in the riser and / or in at least one mud return line.

8. Well control system (100), according to claim 8 or 7, CHARACTERIZED in that the control unit is configured to calculate, estimate or predict the density and / or viscosity of the flowing drilling fluid.

9. Well control system (100), according to any one of claims 1 to 8, CHARACTERIZED in that at least one flow meter (166a, 166b, 200) has a flow measurement range of 10 to 2000 USG / min.

10. Method for measuring at least one parameter or property of drilling fluid in a subsea riser, CHARACTERIZED in that it comprises: providing a well control system (100) for a riser comprising a riser assembly (112); and a pressure-managed drilling manifold (141) comprising: at least one flow meter (166a, 166b, 200); and at least one choke assembly (168a, 168b); wherein the at least one flow meter (166a, 166b, 200) is located on an external surface of the riser assembly (112); and measuring at least one parameter or at least one property of the drilling fluid in the riser. Petition 870260060903, dated 06 / 22 / 2026, page 9 / 15 3 / 4 11. Method, according to claim 10, CHARACTERIZED in that it comprises comparing at least one parameter or at least one property of the drilling fluid with a desired range of parameters or operating properties of the drilling fluid.

12. Method, according to claim 10 or 11, CHARACTERIZED in that it comprises generating a control signal from the control unit when at least one parameter or at least one property of the drilling fluid is determined to be outside the desired range of operating parameters or properties.

13. Method, according to any one of claims 10 to 12, CHARACTERIZED in that it comprises measuring a differential pressure through a differential pressure flow meter ΔP.

14. A method, according to any one of claims 10 to 13, CHARACTERIZED in that it comprises determining or calculating a friction factor, a flow discharge coefficient, Reynolds number, density, viscosity and / or a flow rate of the drilling fluid.

15. Managed pressure drilling method in a subsea drilling operation, CHARACTERIZED in that it comprises: providing a well control system (100) for a riser assembly (112) comprising: a riser assembly (112); and a managed pressure drilling manifold (141) comprising at least one flow meter (166a, 166b, 200); and at least one choke assembly (168a, 168b); wherein at least one flow meter (166a, 166b, 200) is located on an external surface of the riser assembly (112); and providing a rotary control device (120); and Petition 870260060903, dated 06 / 22 / 2026, p. 10 / 15 4 / 4 measure at least one drilling fluid flow property using at least one flow meter (166a, 166b, 200). Petition 870260060903, dated 06 / 22 / 2026, page 11 / 15

Images