US20200190939A1 - Fault-Tolerant Pressure Relief System for Drilling - Google Patents
Fault-Tolerant Pressure Relief System for Drilling Download PDFInfo
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- US20200190939A1 US20200190939A1 US16/222,462 US201816222462A US2020190939A1 US 20200190939 A1 US20200190939 A1 US 20200190939A1 US 201816222462 A US201816222462 A US 201816222462A US 2020190939 A1 US2020190939 A1 US 2020190939A1
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Images
Classifications
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- 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
- E21B34/00—Valve arrangements for boreholes or wells
- E21B34/02—Valve arrangements for boreholes or wells in well heads
- E21B34/04—Valve arrangements for boreholes or wells in well heads in underwater 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
- E21B44/00—Automatic control systems specially adapted for drilling operations, i.e. self-operating systems which function to carry out or modify a drilling operation without intervention of a human operator, e.g. computer-controlled drilling systems; Systems specially adapted for monitoring a plurality of drilling variables or conditions
-
- 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
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/08—Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure
-
- 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
-
- 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
- E21B34/00—Valve arrangements for boreholes or wells
- E21B34/16—Control means therefor being outside the borehole
-
- 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
- E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
- E21B17/01—Risers
-
- 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
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/001—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor specially adapted for underwater drilling
-
- 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
- E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
- E21B21/10—Valve arrangements in drilling-fluid circulation systems
- E21B21/103—Down-hole by-pass valve arrangements, i.e. between the inside of the drill string and the annulus
-
- 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
- E21B34/00—Valve arrangements for boreholes or wells
- E21B34/06—Valve arrangements for boreholes or wells in wells
- E21B34/10—Valve arrangements for boreholes or wells in wells operated by control fluid supplied from outside the borehole
-
- 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
- E21B47/00—Survey of boreholes or wells
- E21B47/06—Measuring temperature or pressure
Definitions
- Flow of formation fluids into a wellbore during drilling operations is called an influx or “kick.”
- a fluid loss occurs when drilling fluid in the wellbore is lost to the formation. Both can have a number of detrimental effects. If a kick cannot be detected and controlled fast enough, it can escalate into an uncontrolled flow of formation fluids to the surface, which is called a “blow-out.” Consequences from a blow-out may vary from operational delays (non-productive time) to more severe damage to equipment.
- Hydrostatic pressure is a first conventional barrier for controlling the well from a “kick,” and blow out preventers (BOP) are a second barrier.
- BOP blow out preventers
- other equipment and techniques can detect and handle a kick during drilling operations to maintain proper hydrostatic pressure in the well.
- kick detection can be achieved by continuously monitoring the return flow (i.e., flow-out) in a closed-loop circulation system and comparing the flow-out to the flow-in to the closed-loop circulation system.
- controlled pressure drilling techniques include managed pressure drilling (MPD), underbalanced drilling (UBD), and air drilling (AD) operations.
- the drilling system uses a closed and pressurizable mud-return system, a rotating control device (RCD), and a choke manifold to control the wellbore pressure during drilling.
- RCD rotating control device
- the various MPD techniques used in the industry allow operators to drill successfully in conditions where conventional technology simply will not work by allowing operators to manage the pressure and flow in a controlled fashion during drilling.
- formation fluids i.e., gas
- the drilling system pumps this gas, drilling mud, and the formation cuttings back to the surface.
- the gas may expand, and hydrostatic pressure may decrease, meaning more gas from the formation may be able to enter the wellbore. If the hydrostatic pressure is less than the formation pressure, then even more gas can enter the wellbore.
- managed pressure drilling attempts to control such kicks or influxes of fluid.
- This can be achieved using an automated choke response in the closed and pressurized circulating system made possible by the rotating control device.
- a control system controls the chokes with an automated response by monitoring the flow-in and the flow-out of the well, and software algorithms in the control system seek to maintain a mass flow balance. If a deviation from mass balance is identified, the control system initiates an automated choke response that changes the well's annular pressure profile and thereby changes the wellbore's equivalent mud weight.
- This automated capability of the control system allows the system to perform dynamic well control or constant bottom hole pressure (CBHP) techniques.
- CBHP constant bottom hole pressure
- a typical overpressure configuration uses a pressure relief valve having a control console that detects an overpressure condition and opens the pressure relief valve to relieve the pressure.
- the overpressure configuration simply includes a first pressure relief valve having its control console and includes a second, separate pressure relief valve having its own control console.
- limited protection can be achieved even though the configuration has some redundancy.
- a fault of one pressure relief valve would negate its use, but the other pressure relief valve with its console could assume overpressure protection.
- a fault of one console would negate use of its pressure relief valve, but the other pressure relief valve with its console could assume overpressure protection.
- loss of rig power, loss of rig air supply, loss of sensor inputs, loss of communications, or any other number of faults could negate use of both pressure relief valves and/or consoles so overpressure protection would be lost.
- the subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
- an assembly is used for relieving pressure of fluid flow in a drilling system in response to a pressure level measurement of the drilling system.
- the assembly comprises: pressure relief valves, hydraulic circuits, and controllers.
- the pressure relief valves are disposed in fluid communication between the fluid flow and at least one discharge outlet. Each of the pressure relief valves is operable to open and close fluid communication of the fluid flow with the at least one discharge outlet.
- the hydraulic circuits are cross-connected to one another and are operably connected to the pressure relief valves. The hydraulic circuits provide hydraulic motive force respectively to the pressure relief valves.
- the controllers are operably connected to the hydraulic circuits. Each of the controllers receives the pressure level measurement of the drilling system. Both of the controllers in a standard condition simultaneously control the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to independently open and close the respective pressure relief valve in response to the pressure level measurement. In response to a first failure condition of either one of the controllers, the other one of the controllers independently controls the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the pressure level measurement.
- either one of the pressure relief valves can automatically fault closed regardless of the pressure level measurement.
- the assembly can comprise a manifold having the one or more flow inlets and having one or more flow outlets.
- the one or more flow inlets can be disposed in fluid communication with an upstream portion of the drilling system and can receive the fluid flow therefrom.
- the one or more flow outlets can be disposed in fluid communication with a downstream portion of the drilling system and can deliver the fluid flow thereto.
- the assembly can further comprise sensors communicatively connected to the controllers and providing readings for the pressure level measurement of the drilling system.
- the assembly can further comprise a plurality of sensors distributed in the hydraulic circuits and measuring a plurality of operational parameters. Both of the controllers can receive the operational parameters. Either one of the controllers can detect a second failure condition associated with the operational parameters from one of the hydraulic circuits and can automatically fault the respective pressure relief valve closed in response to the second failure.
- the hydraulic circuits can comprise pumps connected to a pneumatic supply and pumping the hydraulic motive force.
- a first of the sensors can comprise a first pressure transducer measuring pressure of the pneumatic supply as one of the operational parameters.
- the pumps connected to the pneumatic supply can pump the hydraulic motive force to a common hydraulic input for the hydraulic circuits, and a second of the sensors can comprise a second pressure transducer measuring the common hydraulic input as one of the operational parameters.
- One or more accumulators can be connected to the common hydraulic input.
- the hydraulic circuits can provide the hydraulic motive force in the event of failure of either one of the pumps.
- a third of the sensors can comprise a third pressure transducer measuring pressure of the hydraulic motive force to a first the pressure relief valves as one of the operational parameters. Either one of the controllers can detect the measured pressure below a first threshold as the second failure condition and can automatically fault the first pressure relief valve closed in response thereto.
- a fourth of the sensors can comprise a fourth pressure transducer measuring pressure of the hydraulic motive force to a second the pressure relief valves as one of the operational parameters. Either one of the controllers can detect the measured pressure below a second threshold as the second failure condition and can automatically fault the second pressure relief valve closed in response thereto.
- each of the controllers is communicatively connected to a position sensor of each of the pressure relief valves. Either one of the controllers can detect either one of the pressure relief valves failing to open as the second failure condition.
- each of the hydraulic circuits can comprise an electrically-driven directional control valve having a default no-flow state and an active flow state. Both of the electrically-driven directional control valves are connected to a common hydraulic input.
- each of the controllers can be communicatively connected to the electrically-driven directional control valves of both of the hydraulic circuits to provide a control signal thereto.
- either of the controllers can be configured to automatically fault a respective one of the pressure relief valves closed in response to a failure of the respective electrically-driven directional control valve; and/or the hydraulic motive force can be provided in the open circuit of a first of the hydraulic circuits in the event of a failure of the electrically-driven directional control valve in a second of the hydraulic circuits, where the pressure relief valve of the second hydraulic circuit defaults to a closed condition.
- each of the hydraulic circuits can comprise a pair of open and close hydraulically-driven directional control valves connected to the common hydraulic input.
- the open hydraulically-driven directional control valve can have a default closed state and an active opened state.
- the close hydraulically-driven directional control valve can have a default opened state and an active closed state.
- the active opened state can provide an open output of the hydraulic motive force to open the respective pressure relief valve.
- the default opened state can provide a close output of the hydraulic motive force to close the respective pressure relief valve.
- the open and close hydraulically-driven directional control valves can each have the respective default state in response to the electrically-driven directional control valve having the default no-flow state, and each can have the respective active state in response to the electrically-driven directional control valve having the active flow state.
- each of the hydraulic circuits can comprise a pair of discharge hydraulically-driven directional control valves.
- a first of discharge hydraulically-driven directional control valves can be connected to the open output and can have a default open state and an active close state. The default open state can communicate with a discharge.
- a second of the discharge hydraulically-driven directional control valves can be connected to the close output of the close hydraulically-driven directional control valve and can have a default closed state and an active opened state. The active opened state can communicate with the discharge.
- the discharge hydraulically-driven directional control valves can each have the respective default state in response to the electrically-driven directional control valve having the default no-flow state, and each can have the respective active state in response to the electrically-driven directional control valve having the active flow state.
- Each close output can comprise a pilot-operated check valve piloted by the respective open output.
- an assembly is used with a buffer manifold for relieving pressure of fluid flow in a drilling system.
- the drilling system has a pneumatic supply
- the buffer manifold has one or more flow inlets, one or more flow outlets, and first and second pressure relief valves.
- the one or more flow inlets are disposed in fluid communication with an upstream portion the drilling system and receive the fluid flow therefrom.
- the one or more flow outlets are disposed in fluid communication with a downstream portion the drilling system and deliver the fluid flow thereto.
- the first and second pressure relief valves are disposed in fluid communication between the one or more flow inlets and the one or more flow outlets and are disposed in fluid communication with at least one discharge outlet. Each of the first and second pressure relief valves is operable to open and close fluid communication with the at least one discharge outlet.
- the control assembly comprises a hydraulic arrangement, a plurality of sensors, and a pair of controllers.
- the hydraulic arrangement is operably connected to the first and second pressure relief valves and is connected to the pneumatic supply.
- the hydraulic arrangement is powered by the pneumatic supply and provides hydraulic motive force in two hydraulic circuits respectively to the first and second pressure relief valves.
- the two hydraulic circuits are cross-connected to one another.
- the sensors are distributed in the hydraulic arrangement and measure a plurality of operational parameters of the hydraulic arrangement.
- the controllers are operably connected to the hydraulic arrangement. Each of the controllers receives the operational parameters from the sensors and receives a pressure level measurement of the drilling system. Both of the controllers control the hydraulic motive force provided in the two hydraulic circuits respectively to the first and second pressure relief valves to open and close the first and second pressure relief valves in response to the pressure level measurement.
- a method of controlling fluid flow in a drilling system comprises: receiving the fluid flow from an upstream portion of the drilling system at one or more flow inlets of a manifold assembly; in response to a first pressure level measurement of the drilling system, flowing the fluid flow out one or more flow outlets of the manifold assembly to a first downstream portion of the drilling system in response thereto; in response to a second pressure level measurement of the drilling system, flowing the fluid flow out at least one discharge outlet of the manifold assembly to a second downstream portion of the drilling system, instead of out the one or more flow outlets, by simultaneously controlling, with controllers, hydraulic motive force provided in hydraulic circuits respectively to pressure relief valves to independently open the respective pressure relief valve; in response to a first failure condition of either one of the controllers, independently controlling, with the other one of the controllers, the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the first and second pressure level measurements; and in response to a second failure condition of either one of
- the method can comprise powering pumping of the hydraulic motive force in n the hydraulic circuits with a pneumatic supply.
- both of the pressure relief valves can be automatically faulted closed in response to a total loss of power.
- the method can comprise: measuring a plurality of operational pressures of the hydraulic arrangement using a plurality of pressure transducers distributed in the hydraulic arrangement; receiving the operational pressures from the pressure transducers at the controllers; and faulting the pressure relief valves closed in response to at least one of the operations pressure exceeding a pressure limit.
- the method can comprise routing the hydraulic motive force in the hydraulic circuits cross-connected to one another.
- the method can comprise communicating both of the pressure relief valves in fluid communication between the one or more flow inlets and the one or more flow outlets and in fluid communication with at least one discharge outlet, each of the pressure relief valves being operable to open and close fluid communication with the at least one discharge outlet, both of the controllers operably connected to the hydraulic arrangement controlling the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to open and close the pressure relief valves.
- FIG. 1 illustrates a drilling system according to the present disclosure.
- FIG. 2A illustrates a schematic view of a pressure relief system of the present disclosure for the drilling system.
- FIG. 2B illustrates an isolated view of a buffer manifold for the drilling system.
- FIG. 3 illustrates a graph of pressures used by the pressure relief system.
- FIG. 4 illustrates a cross-sectional view of a plug type valve for use as a pressure relief valve for the disclosed system.
- FIG. 5 illustrates a schematic view of a processing control unit for the disclosed pressure relief system.
- FIG. 6 illustrates a schematic view of a hydraulic control unit for the disclosed pressure relief system.
- FIG. 1 diagrams a drilling system 10 according to the present disclosure.
- this system 10 is a closed-loop system for controlled pressure drilling and can be a Managed Pressure Drilling (MPD) system and, more particularly, a Constant Bottomhole Pressure (CBHP) form of MPD system.
- MPD Managed Pressure Drilling
- CBHP Constant Bottomhole Pressure
- the teachings of the present disclosure can apply equally to other types of drilling systems, such as conventional drilling systems, other MPD systems (Pressurized Mud-Cap Drilling, Returns-Flow-Control Drilling, Dual Gradient Drilling, etc.) as well as to Underbalanced Drilling (UBD) systems, as will be appreciated by one skilled in the art having the benefit of the present disclosure.
- UDD Underbalanced Drilling
- the drilling system 10 is depicted for use offshore on a rig 12 , such as a floating, fixed, or semi-submersible platform or vessel known in the art, although teachings of the present disclosure may apply to other arrangements.
- the drilling system 10 uses a riser 20 extending between a diverter 24 on the rig floor 14 to a blow-out preventer stack 40 on the sea floor.
- the riser 20 connects by a riser joint 22 from the diverter 24 and includes a rotating control device (RCD) 30 , an annular isolation device 32 , and a flow spool 34 disposed along its length.
- a drill string 16 having a bottom hole assembly (BHA) and a drill bit extends downhole through the riser 20 and into a wellbore 18 for drilling into a formation.
- BHA bottom hole assembly
- the riser 20 can direct returns of drilling fluids, wellbore fluids, and earth-cuttings from the subsea wellbore 18 to the rig 12 .
- the diverter 24 can direct the returns of drilling fluid, wellbore fluid, and earth-cuttings to a mud gas separator 90 and other element to separate out the drilling fluid for potential recycle and reuse, and to separate out gas.
- the BOP stack 40 can be operated to close off flow of the returns in the riser 20 .
- the BOP stack 40 may have one or more annular or ram-style blow out preventers on a subsea wellhead, and preventers on the BOP stack 40 can be controlled by various control lines (not shown) from equipment on the rig 12 .
- the riser 20 with its rotating control device 30 , annular isolation device 32 , and flow spool 34 can be configured to divert the uncontrolled wellbore fluid flow in a controlled fashion as described below.
- the rotating control device 30 In managed pressure drilling, the rotating control device 30 , which can include any suitable pressure containment device, keeps the wellbore 18 in a closed-loop at all times while the wellbore 18 is being drilled. To do this, the rotating control device (RCD) 30 sealingly engages (i.e., seals against) the drilling string 16 passing in the riser 20 and can contain and divert annular drilling returns through a flow line 31 c that connects to downstream flow controls on the rig 12 . In this way, the rotating control device 30 can complete the circulating system to create the closed-loop of incompressible drilling fluid.
- RCD rotating control device
- a hydraulic power unit 31 a on the rig 12 can connect by control lines 31 b to the rotating control device 30 to control its operation.
- the control lines 31 b can carry supply and/or return of hydraulic fluid to and from the rotating control device 30 for its operation.
- the annular sealing device 32 can be used to sealingly engage (i.e., seal against) the drillstring 16 or to fully close off the riser 20 when the drillstring 16 is removed so fluid flow up through the riser 20 can be prevented.
- the annular sealing device 32 can use a sealing element that is closed radially inward by hydraulically actuated pistons. Control lines 33 from rig controls 57 can be used for controlling the annular sealing device 32 .
- the flow spool 34 includes a number of controllable valves and connects by flow lines 35 to the downstream flow controls on the rig 12 described below.
- the controllable valves of the flow spool 34 can be opened and closed using control lines 33 from the rig controls 57 .
- the flow controls downstream of the rotating control device 30 , the annular sealing device 32 , and the flow spool 34 include a managed pressure drilling buffer manifold 60 and a choke manifold 70 .
- the buffer manifold 60 connects by the flow lines 31 c and 35 from the rotating control device 30 and the flow spool 34 and receives flow returns during drilling operations.
- a buffer manifold hydraulic power unit 55 operates the buffer manifold 60 .
- the buffer manifold 60 has pressure relief valves 64 a - b , pressure sensors (not shown), electronic valves (not shown), and other components to control operation of the manifold 60 .
- the choke manifold 70 is downstream from the buffer manifold 60 .
- the choke manifold 70 can produce surface backpressure to perform managed pressure drilling with the drilling system 10 and can measure parameters of the flow returns.
- the choke manifold 70 has flow chokes 72 , a flowmeter 74 , pressure sensors (not shown), a local controller (not shown), and the like to control operation of the manifold 70 .
- a hydraulic power unit (not shown) and/or electric motor of the choke manifold 70 can actuate the chokes 72 .
- the system 10 also includes mud pumps 42 ; a mud standpipe manifold 46 for a standpipe (not shown); a choke & kill manifold 80 having kill and choke lines 82 , 84 for the BOP stack 40 ; a mud gas separator 90 ; and various other components. During drilling operations, these components can operate in a known manner.
- a control system 50 of the drilling system 10 integrates hardware, software, and applications across the drilling system 10 and is used for monitoring, measuring, and controlling parameters in the drilling system 10 .
- the control system 50 can be integrated with or communicatively coupled to the RCD hydraulic power unit 31 a , the buffer manifold hydraulic power unit 55 , the buffer manifold 60 , the choke manifold 70 , and other components.
- the drilling control system 50 operates the various components to operate the drilling system 10 .
- control system 50 can further analyze pressure and flow data to detect kicks, losses, and other events. In turn, at least some operations of the drilling system 10 can then be automatically handled by the control system 50 .
- the control system 50 can use data from a number of sensors and devices in the system 10 .
- one or more sensors can measure pressure in the standpipe.
- One or more sensors (La, stroke counters) can measure the speed of the mud pumps 42 for deriving the flow rate of drilling fluid into the drillstring 16 . In this way, flow into the drillstring 16 may be determined from strokes-per-minute and/or standpipe pressure.
- One or more sensors can measure the volume of fluid in the mud tanks 44 and can measure the rate of flow into and out of mud tanks 44 . In turn, because a change in mud tank level can indicate a change in drilling fluid volume, flow-out of the wellbore 18 may be determined from the volume entering the mud tanks 44 .
- the control system 50 can use the flowmeter 74 , such as a Coriolis mass flowmeter, on the choke manifold 70 to capture fluid data—including mass and volume flow, mud weight (i.e., density), and temperature—from the returning annular fluids in real-time, at a sample rate of several times per second. Because the Coriolis flowmeter gives a direct mass rate measurement, the flowmeter 74 can measure gas, liquid, or slurry. Other sensors can be used, such as ultrasonic Doppler flowmeters, SONAR flowmeters, magnetic flowmeter, rolling flowmeter, paddle meters, etc.
- Additional sensors can measure mud gas, flow line temperature, mud density, and other parameters.
- a flow sensor can measure a change in drilling fluid volume in the well.
- a gas trap such as an agitation gas trap, can monitor hydrocarbons in the drilling mud at surface. To determine the gas content of drilling mud, for example, the gas trap mechanically agitates mud flowing in a tank. The agitation releases entrained gases from the mud, and the released gases are drawn-off for analysis. The spent mud is simply returned to the tank 44 to be reused in the drilling system 10 .
- the drill string 16 passing from the rig 12 can extend through the riser 20 and through the BOP stack 40 for drilling the wellbore 18 .
- the rotating control device 30 seals the annulus between the drillstring 16 and the riser 20 to conduct a managed pressure drilling operation. In this way, flow returns having drilling fluid, wellbore fluid, and cuttings flow up through the annulus between the drillstring 16 and the riser 20 to the rotating control device 30 , which diverts the flow returns through the flow line 31 c to the buffer manifold 60 .
- control system 50 which in turn operates drilling functions.
- control system 50 can operate the automated choke manifold 70 , which manages pressure and flow during drilling and which is incorporated into the drilling system 10 downstream from the rotating control device 30 and buffer manifold 60 and upstream from the gas separator 90 .
- the buffer manifold 60 can direct the flow returns in various way as needed.
- the buffer manifold 60 passes the flow returns to the choke manifold 70 .
- the automated choke manifold 70 measures the return flow (e.g., flow-out) and density using the flowmeter 74 installed in line with the chokes 72 .
- Software components of the control system 50 then compares the flow rate in and out of the wellbore 18 , the injection pressure (or standpipe pressure), the surface backpressure (measured upstream from the drilling chokes 72 ), the position of the chokes 72 , and the mud density, among other possible variables. Comparing these variables, the control system 50 then identifies minute downhole influxes and losses on a real-time basis and control surface backpressure with the chokes 72 to manage the annulus pressure during drilling.
- the control system 50 monitors circulation to maintain balanced flow for constant BHP under operating conditions and to detect kicks and lost circulation events that jeopardize that balance.
- the drilling fluid is continuously circulated through the system 10 , the buffer manifold 60 , the choke manifold 70 , and the flowmeter 74 .
- the flow values may fluctuate during normal operations due to noise, sensor errors, etc. so that the system 50 can be calibrated to accommodate such fluctuations.
- the control system 50 measures the flow-in and flow-out of the well and detects variations. In general, if the flow-out is higher than the flow-in, then fluid is being gained in the system 10 , indicating a kick. By contrast, if the flow-out is lower than the flow-in, then drilling fluid is being lost to the formation, indicating lost circulation.
- control system 50 introduces pressure and flow changes to the incompressible circuit of fluid at the surface to change the annular pressure profile in the wellbore.
- the control system 50 can produce a reciprocal change in bottom hole pressure. In this way, the control system 50 uses real-time flow and pressure data and manipulates the annular backpressure to manage wellbore influxes and losses.
- the drillstring 16 may be lifted out of the riser 20 , and the annular sealing device 32 may be actuated to close off the riser 20 .
- the controllable valves on the flow spool 34 can be operated to direct fluid in the riser 20 below the rotating control device 32 through the flow lines 35 to the buffer manifold 60 .
- the annular sealing device 32 can be actuated to seal off the annulus around the drillstring 16 (if present). The rotation of the drillstring 16 can be stopped during the event, or the annular sealing device 32 may be capable of sealing against the drillstring 16 while rotating. Either way, the controllable valves on the flow spool 34 can be operated to direct fluid in the riser 20 below the annular sealing device 32 through the flow lines 35 to the buffer manifold 60 .
- a pressure relief system 100 operates pressure relief valves 64 a - b on the buffer manifold 70 to divert the flow returns from the flow lines 31 c , 35 overboard, to trip tanks 44 , or to other fluid handling components. This diversion can then prevent the overpressure flow from damaging the riser 20 and passing on to the choke manifold 70 .
- the pressure relief system 100 can be incorporated into the buffer hydraulic power unit 55 , although separate configurations are possible.
- the pressure relief system 100 has an integrated PLC based control system and a hydraulic control unit (HCU) and is connected to the pressure relief valves 64 a - b and other components of the buffer manifold 60 by control lines 105 .
- the pressure relief system 100 can open and close the pressure relief valves 64 a - b simultaneously. When opened, the redundant pressure relief valves 64 a - b provide pressure relief in the event of over-pressurization of the wellbore 18 and/or surface equipment. Once opened, the pressure relief system 100 provides a further function of closing the pressure relief valves 64 a - b to prevent an induced kick from occurring after the relief of overpressure.
- the pressure relief valves 64 a - b are configured to nominally fail in the closed position. There may be several reasons for this. Primarily, the purpose of the MPD drilling system 10 is to impose dynamic backpressure on the wellbore 18 using the choke manifold 70 . If one of the pressure relief valve 64 a - b fails open, then backpressure cannot be maintained. Additionally, the wellbore 18 is normally in static or dynamic balance so a demand for overpressure protection of equipment is less likely to occur. Instead, the more likely cause of an open command to the pressure relief valves 64 a - b would be to protect the formation.
- the pressure relief system 100 can operate in a stand-alone mode to protect against process upsets during drilling with the drilling system 10 .
- the pressure relief system 100 includes a sensor arrangement 110 , a processing control unit 120 , and a hydraulic control unit 130 for the buffer manifold 60 .
- Power from a power supply 140 can be common to the three elements 110 , 120 , and 130 of the system 100 .
- each of the elements 110 , 120 , 130 , and 140 includes redundancies so that a fault of a component in one element does not fault other components of that element nor fault components of the other elements.
- the system 100 is more than just a combination of one pressure relief valve having its control console with another pressure relief valve having its own control console. In such an arrangement, limited fault protection would be achieved as discussed in the background section of the present disclosure.
- the pressure relief system 100 disclosed herein addresses multiple points of failure in the disclosed arrangement by providing a redundancy at that point of failure, by providing independent monitoring of that point of failure, and by preventing a fault at that point of failure from translating to a fault of the redundancy. In this way, the disclosed pressure relief system 100 provides a redundant, fault-tolerant integration of sensing, processing, hydraulic, and power elements 110 , 120 , 130 , and 140 for the redundant pressure relief valves 64 a - b.
- the sensor arrangement 110 includes sensors 112 , 116 and electrical buffers 114
- the processing control unit 120 includes two programmable logic controllers (PLCs) 122 a - b .
- PLCs programmable logic controllers
- the hydraulic control unit 130 provides hydraulic valve control for the two pressure relief valves 64 a - b of the manifold 60 .
- the sensors in the arrangement 110 include transducers 112 receiving pressure and other measurements from pneumatic and hydraulic sources. These transducers 112 can be distributed in the hydraulic control unit 130 in the manifold 60 .
- the sensors in the arrangement 110 also include sensors 116 receiving line or process pressures from the drilling system ( 10 ). These sensors 116 can be disposed on the flow line entering the inlet 62 a of the buffer manifold 60 . These sensors 116 measure redundant measurements of the process pressure, and voting between the sensor measurements can be used in decisions of the processing control unit 120 .
- the buffer manifold 60 in FIG. 2A is used for directing process flow in various ways.
- the manifold 60 includes one or more flow inlets 62 a disposed in fluid communication with an upstream portion of the drilling system ( 10 ) and receives the fluid flow therefrom.
- the manifold 60 also includes one or more flow outlets 62 b disposed in fluid communication with a downstream portion of the drilling system ( 10 ) and delivers the fluid flow thereto.
- the manifold 60 includes at least one discharge outlet 65 to relieve pressure.
- the pressure relief valves 64 a - b are used for relieving pressure of fluid flow in the drilling system ( 10 : FIG. 1 ) in response to a pressure level measurement, such as a flow line pressure from the sensors 116 , being over a limit.
- a pressure level measurement such as a flow line pressure from the sensors 116
- the manifold 60 has a number of inlets 62 a and receives fluid from the RCD ( 30 ) via flow lines 31 c , receives flow from the flow spool ( 34 ) via flow lines 35 , receives flow from the choke/kill manifold ( 80 ), etc.
- the manifold 60 has a number of outlets 62 b and delivers flow returns to the choke manifold ( 70 ), to the choke/kill manifold ( 80 ), trip tank ( 44 ), and other downstream portions of the drilling system ( 10 ) instead of to the choke manifold ( 70 ).
- the manifold 60 includes a number of solenoid actuated gate valves 66 , flow tees, manifold elements, piping, etc. for controlling flow between the inlets 62 a and the outlets 62 b during drilling operations.
- the buffer unit 55 interfaces with the solenoid actuated gate valves 66 for directing flow according to operational needs.
- the pressure relief system 100 which can part of the buffer unit 55 and which includes the elements 110 , 120 , 130 , 140 , of FIG. 2A interfaces with the pressure relief valves 64 a - b to relieve overpressure from the inlets 62 a to the discharge outlets 65 .
- the redundant pressure relief valves 64 a - b are disposed in fluid communication between the one or more flow inlets 62 a and the one or more flow outlets 62 b and disposed in fluid communication with the at least one discharge outlet 65 .
- Each of the redundant pressure relief valves 64 a - b is operable to open and close fluid communication with the at least one discharge outlet 65 .
- the hydraulic control unit 130 in FIG. 2A has a hydraulic arrangement operably connected to the redundant pressure relief valves 64 a - b . Redundant hydraulic circuits of the unit 130 are cross-connected to one another and are operably connected to the redundant pressure relief valves 64 a - b . The redundant hydraulic circuits provide hydraulic motive force respectively to the redundant pressure relief valves 64 a - b.
- the transducers 112 are distributed in the redundant hydraulic circuits of the hydraulic control unit 130 and measure operational parameters of the hydraulic circuits to diagnose the unit 130 and its operation.
- the other sensors 116 are distributed to measure line or process pressure of the manifold's inlets 62 a as the pressure level measurement used in activating or deactivating the pressure relief system 100 .
- These sensors 116 can be disposed on the flow line 31 c from the RCD ( 30 ) leading into the inlet 62 a of the buffer manifold 60 .
- two or more of these sensors 116 can be used for redundancy.
- four sensors 116 can be used to measure the process pressure at the same point of the flow line to the inlet 62 a .
- Each of these sensors 116 can be the same as one another (i.e., have the same ratings, same sensitivities, etc.) for redundant verification of the pressure measurements.
- the sensors 116 can be identical.
- one or more of the sensors 116 may have different ratings, sensitivities, or the like from the other sensors 116 .
- the redundant controllers 122 a - b are operably connected to the redundant hydraulic circuits of the hydraulic control unit 130 .
- Each of the redundant controllers 122 a - b receives the operational parameters from the transducers 112 and also receives pressure level measurements of the drilling system ( 10 ) for the sensors 116 .
- Both of the redundant controllers 122 a - b in a standard operating condition then simultaneously control the hydraulic motive force provided in the redundant hydraulic circuits of the hydraulic unit 130 respectively to the redundant pressure relief valves 64 a - b to independently open and close the respective pressure relief valve 64 a - b in response to the pressure level measurement from the line pressure sensors 116 .
- FIG. 5 Additional details of the processing unit 120 are disclosed in FIG. 5 , and additional details of the hydraulic control unit 130 are disclosed in FIG. 6 .
- the system 100 is a redundant, fault tolerant, pressure protection system used in the operation of the two pressure relief valves 64 a - b intended for protection of process or line pressure in the drilling system ( 10 : FIG. 1 ).
- the pressure relief system 100 is operable in response to different failure or fault conditions.
- the other one of the redundant controllers 122 a - b independently controls the hydraulic motive force provided in the redundant hydraulic circuits of the hydraulic unit 130 respectively to the redundant pressure relief valves 64 a - b to simultaneously open and close the respective pressure relief valves 64 a - b in response to the pressure level measurement from the line pressure sensors 116 .
- a second failure condition of either one of the redundant hydraulic circuits of the hydraulic unit 130 however, either one of the redundant pressure relief valves 64 a - b automatically faults closed regardless of the pressure level measurement from the line pressure sensors 116 .
- one pressure relief valve 64 a - b and its associated electrical, hydraulic, or pneumatic controls is capable of relieving excess line pressure.
- the failed pressure relief valve 64 a - b fails closed allowing the remaining pressure relief valve 64 a - b and its associated electrical, hydraulic, or pneumatic controls to continue to maintain control over line pressure and relieve pressure as needed.
- having a valve “fail closed” refers to the failed valve closing, as opposed to the valve simply failing-in-place—i.e., the valve staying in its current position.
- the pressure relief system 100 is controlled by a user-defined setpoint 124 , which can be set over a pressure range to a coded equipment protection setpoint 126 .
- the user-defined setpoint 124 can be entered locally at a console or remotely by computer using an interface application. Under normal operation, exceeding the setpoint 124 for line pressure causes both pressure relief valves 64 a - b to open to relieve line pressure. Thereafter, when line pressure is reduced, both pressure relief valves 64 a - b then close.
- FIG. 3 illustrates a graph of pressure set points and values used by the pressure relief system 100 .
- the user-defined setpoint 124 to open the two pressure relief valve 64 a - b is a dynamic process protection level (PPL) setpoint 124 , which extends over a pressure range from 0 to a hard-coded equipment protection level (EPL) setpoint 126 .
- PPL dynamic process protection level
- EPL hard-coded equipment protection level
- the dynamic setpoint 124 is the “open” setpoint for the pressure relief valves 64 a - b , indicating the pressure level set for the pressure relief valves 64 a - b to open and relieve process pressure for overpressure protection.
- the dynamic setpoint 124 allows operators to limit the applied surface backpressure while (a) drilling narrow margin wells (well protection setpoint) and while (b) during short periods for make and break of drilling stands (connections setpoint.)
- the equipment protection setpoint 126 is hard-coded and is set based on the lowest pressure rating.
- the dynamic setpoint 124 (valve opens) may cover a range of pressure from 0 to 80% of riser (or surface equipment) maximum allowable operating pressure (MAOP).
- MAOP riser (or surface equipment) maximum allowable operating pressure
- the MAOP is separately hard coded into the programmable logic controllers 122 a - b to protect the riser ( 20 ) and surface equipment ( 60 , 70 , etc.).
- the process sensors ( 116 ) measure the process pressure at the inlet ( 62 a ) of the manifold ( 60 ) to provide the current line or process pressure 128 . Because multiple sensors 116 are used, a voting scheme between the sensors' measurements can be used to decide what the current line pressure 128 is. For example, the voting scheme can decide the pressure 128 from an average of the three closest measurements, or some other scheme can be used. Thus, if one sensor 116 makes a momentary erroneous measurement, it need not be relied upon.
- the current line pressure 128 is compared to the dynamic setpoint 124 , which can be changed, for example, (a) during drill-pipe make-and-break, (b) as the wellbore ( 18 ) is deepened and new geological structures are encountered, and (c) when conducting formation integrity tests (FIT) or leak off tests (LOT). Therefore, as the drilling process goes through different operations, the dynamic setpoint 124 is changed so overpressure protection is provided in the manner best suited to the drilling operations at the time.
- FIT formation integrity tests
- LOT leak off tests
- both pressure relief valves 64 a - b opening simultaneously in order to reduce pressure. Thereafter, both pressure relief valves 64 a - b close at a trailing setpoint 125 in order to prevent an induced kick from occurring due to the relief of pressure.
- the trailing setpoint 125 is the close setpoint for when the valves 64 a - b close after opening.
- the trailing setpoint 125 may be hard coded at 80% of the dynamic open setpoint 124 .
- the hard-coded equipment protection setpoint 126 simultaneously opens both pressure relief valves 64 a - b in order to protect the riser ( 20 ) and surface equipment from overpressure.
- one form of voting between the measurements of the pressure sensors ( 116 ) can be used to determine whether the current line pressure 128 has reached the equipment protection setpoint 126
- the equipment protection setpoint 126 is triggered by another form of voting when any one of the pressure sensors 116 reports a measured value exceeding the equipment protection setpoint 126 .
- both pressure relief valves 64 a - b then close at a trailing setpoint (not shown) in order to prevent an induced kick.
- the open equipment protection setpoint 126 is nominally set at 80% of maximum allowable operating pressure (MAOP).
- MAOP maximum allowable operating pressure
- the trailing close setpoint used after opening for the equipment protection may correspond to the dynamic close setpoint 124 . This may ensure that the well is bought back to a state previously identified as being required to drill the wellbore or make the connection.
- the dynamic setpoint 124 allows backpressure adjustment during make-and-break of drillpipe of the drillstring ( 16 ).
- the mud pumps ( 42 ) are stopped prior to making a connection. This results in a loss of equivalent circulating density (ECD), which in turn reduces downhole pressure.
- ECD equivalent circulating density
- the drilling system ( 10 ) is used to compensate for the loss of ECD by increasing the backpressure applied at the chokes ( 72 ) of the choke manifold ( 70 ).
- the increase in backpressure may be several hundred PSI, which means the dynamic setpoint 124 must be increased to a value equal to surface backpressure (SBP) plus a margin (M) that prevents the pressure relief valves ( 64 a - b ) from opening erroneously.
- SBP surface backpressure
- M margin
- the adjustment of the dynamic setpoint 124 may be reviewed with the connection every drillpipe stand. However, if the ‘open’ dynamic setpoint 124 is triggered, then there is a risk of an influx that could escalate to a loss of well control. For this reason, the processing unit ( 120 ) is programmed to close the pressure relief valves ( 64 a - b ) with the trailing ‘close’ setpoint 125 .
- the dynamic setpoint 124 also provides wellbore protection while drilling.
- the pressure relief valves ( 64 a - b ) must open at a dynamic setpoint 124 chosen by the driller whose goal is to protect the open formation against fracture. If the hydrostatic and applied backpressure from the column of drilling mud is too high, then drilling fluid may be lost into the formation.
- the dynamic open setpoint 124 may be up to 80% of MAOP (e.g. if RCD is rated for 2000 psi, 80% of the MAOP is 1600 psi), leaving no pressure margin and time-delay between relief for well protection, and equipment overpressure.
- both pressure relief valves ( 64 a - b ) results in a significant and rapid loss of surface back pressure, so both pressure relief valves ( 64 a - b ) preferably close at the trailing setpoint 125 to minimize an induced kick.
- the trailing close setpoint 125 may be set at 80% of the dynamic open setpoint 124 . If the dynamic setpoint 124 is set high and one or both pressure relief valves ( 64 a - b ) fails to close, then there is the risk of an induced kick that could escalate to blow out after a period of minutes or hours. In this situation, the driller would have to secure the well.
- the pressure relief system 100 operates in an equipment protection mode to open and close in emergency scenarios where high surface pressure (i.e., overpressure) is detected in the line pressure at the inlets ( 62 a ) of the manifold ( 60 ).
- high surface pressure i.e., overpressure
- the return flow path of the MPD system ( 10 ) is blocked (e.g. by an inadvertently closed valve).
- a gas kick has been transported or migrated to surface, resulting in a threat of equipment overpressure.
- the pressure relief valves ( 64 a - b ) open at the dynamic setpoint 124 to relieve pressure and then close at the trailing setpoint 125 to maintain backpressure on the well.
- the programming in the controllers ( 122 a - b ) for the dynamic setpoint 124 does not allow the operator to enter a value greater than the open setpoint 126 for equipment protection. This means the dynamic open setpoint 124 operates first, thereby preventing conflicting commands from the controllers ( 122 a - b ) (i.e., simultaneous close for dynamic setpoint 124 , and open for equipment protection 126 ).
- the pressure relief valves 64 a - b of the disclosed pressure relief system 100 can be a plug type valve rated for high-pressure service in drilling applications, although other types of valves, chokes, and the like can be used.
- FIG. 4 schematically illustrates a plug type valve that can be used for the system's pressure relief valve 64 .
- the valve 64 includes a body 150 , a plug 160 , and a hydraulic actuator 168 .
- An interior 152 of the valve body 150 has an inlet 154 and an outlet 156 with a seat 155 disposed therebetween.
- the plug 160 is sealed in the interior 152 and is movable relative to the seat 155 .
- the hydraulic actuator 168 is a piston connected to the plug 160 by a stem 162 .
- the actuator 168 is sealed in a hydraulic chamber 158 communicating with hydraulic ports 159 a - b .
- Other hydraulic arrangements, such as scroll screw actuators, choke actuators, or the like, can be used for the actuator 168 .
- Operation of the valve 64 is achieved via the hydraulic actuator 168 integral to the plug 160 .
- the air-driven hydraulic power unit ( 130 : FIG. 2A ) provides motive force to the actuator 168 via the ports 159 a - b .
- a position or proximity sensor 157 can be used with the actuator 168 to at least indicate that the valve 64 is open.
- the valve 64 is held closed by line pressure at the input 154 acting against the plug 160 and by application of the piston force of the actuator 168 . Reversing the hydraulic pressure acting across the actuator 168 , to a point where piston force exceeds well fluid force, opens the valve 64 . This moves the plug 160 off the seat 155 at which point downstream pressure assists opening, and line flow can pass from the inlet 154 to the outlet 156 .
- FIG. 5 illustrates a schematic of the processing control unit 120 for the disclosed pressure relief system 100 .
- the processing control unit 120 uses an electric control panel containing duplicate power input sources (AC- 1 , AC- 2 ), duplicate power supplies 140 , redundant failsafe programmable logic controllers (PLC) 122 a - b , and redundant sensor inputs via a communication interface 105 with the hydraulic control unit ( 130 ).
- AC- 1 , AC- 2 duplicate power input sources
- PLC redundant failsafe programmable logic controllers
- the processing unit 120 can further use fusing to prevent cascade electrical faults, a connection for a local HMI display 104 a , and a fiber optic interface for remote operation by other processing equipment 104 b , such as in a driller's cabin on the rig. Instrumentation can be included to reveal any electronic failure of components.
- the local and remote interfaces 104 a - b are redundant of one another so one could be used in the absence or failure of the other. In general, the interfaces 104 a - b can provide setup, configurations, alarms, diagnostics, and the like for both controllers 122 a - b.
- the two programmable logic controllers 122 a - b operate in a fully parallel, redundant configuration.
- the controllers 122 a - b can be powered by the duplicate AC power input sources (AC- 1 , AC- 2 ), and duplicate DC power supplies 140 .
- One power source (AC- 1 ) can be rig power, while the other power source (AC- 2 ) can be an uninterruptable power supply.
- a router for communications may or may not be necessary.
- the redundant sensor inputs of the interface 105 can be protected by the electrical barriers 114 having fuses to prevent a cascade of electrical faults.
- Each controller 122 a - b can be connected to the common, local HMI display 104 a .
- the fiber optic interface may support remote monitoring and basic process control via interface applications with remote processing equipment 104 b .
- the interface electronics configuration is redundant and fault tolerant.
- each controller 122 a - b receives input from the same sources.
- each controller 122 a - b receives input from the transducers 112 a - d distributed in the hydraulic power unit ( 130 ), receives position sensing input 107 a - b from the pressure relief valves ( 64 a - b ), and receives input from the process sensors 116 a - d of the manifold ( 60 ).
- Each of the various pressure transducers and sensors ( 112 a - d , 116 ) can be installed in a location and orientation designed to sense line blockage.
- Each controller 122 a - b uses a voting scheme for the measurements of the process sensors 116 a - d , and each controller 122 a - b processes the inputs with the identical logic.
- each controller 122 a - b provides control signals through outputs 106 a - b to the pressure relief valves ( 64 a - b ). Therefore, the controllers 122 a - b should operate the same and should produce the same processing results. In this way, the controllers 122 a - b simultaneously operate the two pressure relief valves 64 a - b , yet do their processing independently.
- Diagnostics from each individual controller 122 a - b may or may not be included in the logic. Such diagnostics may or may not be communicated between the controllers 122 a - b . If diagnostics are shared, each controller 122 a - b can operate according to an appropriate voting scheme to resolve conflicts between any processing results. Alternatively, the controller 122 a - b with superior diagnostics may override the other. In fact, one controller 122 a - b may operate on standby, awaiting its need to assume control from the other controller 122 a - b . Preferably, however, both controllers 122 a - b as noted herein simultaneously process the inputs and provide their independent results, which should be identical or nearly identical under the circumstances.
- both controllers 122 a - b and their associated electronics can operate both pressure relief valves ( 64 a - b ) simultaneously, but independently. As shown, each controller 122 a - b shares a first control output 106 a to open the first pressure relief valve ( 64 a ), and each controller 122 a - b shares a second control output 106 b to open the second pressure relief valve ( 64 b ). Each valve ( 64 a - b ) is, however, independently capable of the needed open/close functions. In the event of a failure of either one of the controllers 122 a - b or its associated electronics, the remaining controller 122 a - b and associated electronics can continue to operate both pressure relief valves 64 a - b.
- each controller 122 a - b also shares the communication interface 105 connected to the transducers 112 a - d of the hydraulic control unit ( 130 ).
- the interface 105 includes connections to a first transducer 112 a for measuring the pneumatics for the manifold ( 60 ) and connections to other transducers 112 b - d for measuring the hydraulics for the manifold ( 60 ), as described later.
- the communication interface 105 includes a connection to a level indicator 112 e for receiving an indication of hydraulic level of the hydraulic control unit ( 130 ). In this way, the transducers 112 a - e provide diagnostics of the hydraulic unit ( 130 ).
- each controller 122 a - b also shares communication with the sensors 116 , which can be pressure transducers that redundantly measure the line pressure to detect an overpressure condition requiring pressure relief by the pressure relief system 100 .
- These pressure transducers 116 can have the same or different ranges, alarms, sensitivities, etc.
- the communication interface 105 also includes a first connection (PRV 1 ZT 1 ) to a first position sensor ( 157 ) for the first pressure relief valve ( 64 a ), and includes a second connection (PRV 2 ZT 2 ) to a second position sensor ( 157 ) for the second pressure relief valve ( 64 b ).
- the position sensors ( 157 ) can indicate if the associated valve 64 a - b is fully open.
- FIG. 6 illustrates a schematic of a hydraulic control unit 130 for the disclosed pressure relief system ( 100 ).
- the hydraulic control unit 130 consists of redundant hydraulic, pneumatic, and electrical components.
- Field deployment uses bulkhead connections 170 for rig air supply 172 , sensors connections 112 a - d , and hydraulic connections 174 a - b .
- Hydraulics controls consist of dual air driven pumps 186 a - b , dual accumulators 188 a - b , and hydraulic circuits 180 a - b cross-connected for redundancy. Each half of the duplicated components is sized to operate both pressure relief valves 64 a - b simultaneously.
- the two hydraulic circuits 180 a - b operate the pressure relief valves 64 a - b independently.
- Each circuit 180 a - b includes a spring-biased (to default close) solenoid operated directional control valve (DCVs) 192 a - b .
- DCVs solenoid operated directional control valve
- Each electrically-operated valve (DCVs) 192 a - b in turn energizes four (4) hydraulically-operated directional control valves (DCVs) 194 a - d , 196 a - d .
- each circuit 180 a - b delivers open pressure 174 a and close pressure 174 b for the motive force of the pressure relief valves ( 64 a - b ).
- rig air supply 172 for the circuits 180 a - b is split and passes through filter-regulator-lubricator components 181 a - b to pneumatic pumps 186 a - b .
- Hydraulic fluid from a hydraulic source 182 is drawn by the pneumatic pumps 186 a - b through suction lines 184 a - b .
- the hydraulics pass components 187 a - b of pressure relief valves, check valves, and the like. The hydraulics then combine together in a common hydraulic input 188 and pass connections to the accumulators 188 a - b .
- the accumulators 188 a - b can take over in maintaining the hydraulic pressure should the rig air supply 172 fail or both of the pumps 180 a - b fail. Moreover, one of the accumulators 188 a - b can take over for the other should it fail.
- the combined pumped hydraulic input 188 then pass to split controls 190 a - b , each having an electrically-driven directional control valve 192 a - b .
- the first electrically-driven valve 192 a operates to open/close the first of the pressure relief valves ( 64 a ) and receives first control signals ( 106 a : FIG. 5 ) from either of the controllers 122 a - b of the processing control unit ( 120 ).
- the second electrically-driven valve 192 b operates to open/close the second of the pressure relief valves ( 64 b ) and receives first control signals ( 106 b : FIG. 5 ) from either of the controllers ( 122 a - b ) of the processing control unit ( 120 ).
- each electrically-driven valve 192 a - b receives an input signal from both of the controllers 122 a - b . In this way, an input signal to actuate the electrically-driven valves 192 a - b and open the pressure relief valve 64 a - b can be received from one or both of the controllers 122 a - b . Because each of the electrically-driven valves 192 a - b shares two electrical connections with the controllers 122 a - b , each connection needs to be isolated from the other so that a short of one connection does not translate to a short of the other.
- a short of the electrical connection of one controller 122 a to the electrically-driven valve 192 a should not cause a short of the electrical connection of the other controller 122 b to the electrically-driven valve 192 a .
- each of the electrical connections between components of the control unit ( 120 ) and the hydraulic control unit 130 for the various shared sensors, signals, inputs, outputs, and the like are likewise isolated to prevent a short of one translating to a short of another.
- Each electrically-driven valve 192 a - b has a set of four hydraulically-operated directional control valves (DCVs) 194 a - d , 196 a - d , which are stacked as piloted valves with reduced leakage in the hydraulic arrangement.
- DCVs hydraulically-operated directional control valves
- the combined pumped hydraulics pass to both the electrically-driven valves 192 a - b and also split to pass to the open and close hydraulically-driven valves 194 a - b , 196 a - b .
- Respective output from the split controls 190 a - b pass pilot-operated check valves 198 a - b before reaching the open connections 174 a and the close connections 174 b on the bulkhead 170 for the two pressure relief valves 64 a - b.
- the first electrically-driven valve 192 a has a default state, including (3 closed) closing off communication of the pumped hydraulics and including (1-2 pass) connecting the pressure inputs (3) of the hydraulically-operated valves 194 a - d to the discharge line 185 .
- the first electrically-driven valve 192 a has an active state, including (3-2 pass) and including (1 closed) directing the pumped hydraulics to the pressure inputs (3) of the hydraulically-operated valves 194 a - d.
- the open hydraulically-driven valve 194 a has a default closed state (2 closed, 1 closed) and has an active opened state (2-1 pass) when hydraulically driven by pressure input (3).
- the close hydraulically-driven valve 194 b has a default opened state (2-1 pass) and has an active closed state (2 closed, 1 closed) when hydraulically driven by pressure input (3) shared with the open hydraulically-driven valve 194 a.
- the other hydraulically-driven valves 194 c - d control communication from the open and close hydraulically-driven valve 194 a - b to the discharge line 185 .
- These valves 194 c - d share pressure inputs (3) selectively connected by the electrically-driven valves 192 a to the discharge line 185 or the combined pumped hydraulics.
- One of these valves 194 c has a default state, including (2-closed, 1-closed) preventing communication of the output from the close valve 194 b to the discharge line 185 , and has an active state, including (1-2 pass) communicating the output from the close valve 194 b to the discharge line 185 .
- the other of these valves 194 d has a default state, including (1-2 pass) communicating the output from the open valve 194 a to the discharge line 185 , and an active state, including (2-closed, 1-closed) preventing communication of the output from the open valve 194 a to the discharge line 185 .
- the electrically-driven valve 192 b and hydraulically-driven valves 196 a - d for the second circuit 180 b are similarly configured. Therefore, the above discussion is reincorporated here, applying to the connections between the electrically-driven valve 192 b and the hydraulically-driven valves 196 a - d for the second circuit 180 b.
- Instrumentation is included to monitor critical pneumatic and hydraulic functions to reveal any hydraulic or pneumatic component or circuit failure.
- the instrumentation includes the transducers 112 a - d , which connect via buffers ( 114 ) to the processing unit's interface ( 105 : FIG. 5 ) for the controllers ( 122 a - b ) of the processing control unit ( 120 ).
- the first transducer 112 a measures the air supply 172 for the pumps 186 a - b .
- the second transducer 112 b measures the hydraulic power unit's pressures for the two circuits 180 a - b .
- the third transducer 112 c measures the pressure relief valve's pressure for the first circuit 180 a
- the fourth transducer 112 d measures the pressure relief valve's pressure for the second circuit 180 b
- the level indicator 112 e measures the level of hydraulic fluid in the hydraulic source 182 .
- the pressure relief system 100 is configured so that no component failures would cause one of the pressure relief valves 64 a - b to fail open. Instead, certain component failures cause one of the pressure relief valves 64 a - b to fail closed. Examples of component failures that can cause one pressure relief valve 64 a - b to fail closed (after opening) include: (a) failures of certain electrical fuses; (b) failures of one of the directional control valves 192 a - b (DCV 1 or DCV 2 ); or (c) failure of one of the pilot operated check valves 198 a - b . An example of component failures that can cause both pressure relief valves 64 a - b to fail closed (after opening) includes a total loss of power (blackout).
- component failures may occur that require operations to be stopped.
- certain component failures may potentially cause one or both the pressure relief valves 64 a - b to fail in place or fail open, at which point operations would be stopped.
- These component failures could include failure of the hydraulically-operated control valves 194 a - d , 196 a - d (DCV 1 A to DCV 1 D or DCV 2 A to DCV 2 D), failure of analog inputs, failures of accumulator bleed valves, and the like.
- the pressure relief system 100 of the present disclosure can be used for the buffer manifold 60 in a managed pressure drilling system 10 .
- the equipment protection provided by the pressure relief system 100 is applied with the pressure relief valves 64 a - b at the buffer manifold 60 to protect the riser 20 , the choke manifold 70 , the formation, etc.
- overpressure protection of surface equipment for scenarios where the source of overpressure is from the standpipe manifold 46 , the choke & kill manifolds 80 , or other equipment.
- teachings of the present disclosure can be applied to rapid acting pressure protection for other interconnects of the drilling system 10 , such as interconnects of the standpipe manifold 46 , the choke and kill manifold 80 , and discharge of the mud pumps 42 .
- the pressure relief system 100 can be used elsewhere in a drilling system 10 and can be used in processes where protection from overpressure is desired.
- FIG. 1 illustrates where a pressure relief system 100 ′ can used in another location of the drilling system 10 .
- the pressure relief system 100 ′ is used for the overpressure protection at the discharge of the mud pumps 42 .
- the details of the pressure relief system 100 ′, including the pressure relief valves, controllers, sensors, hydraulic circuits, etc., are similar to those disclosed above so that the description of these details are incorporated here. Redundant sensors measure the discharge pressure of the mud pumps 42 for overpressure protection so the pressure relief system 100 ′ can be opened to relieve overpressure when needed.
- the disclosed pressure relief system 100 ′ can be used for overpressure protection in the standpipe manifold 46 .
- the disclosed pressure relief system can be used in other drilling configurations and systems.
- the drilling system can include a flowline from the wellbore.
- the pressure relieve system can use a pressure relief valve and a choke on the flowline from the wellbore. The flow passes through the pressure relief valve and passes to the choke before passing on to further downstream equipment.
- the pressure relief system in this arrangement can relieve overpressure so equipment can be protected, while still being able to be dynamically adjusted for the current needs of an operation.
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Abstract
Description
- Flow of formation fluids into a wellbore during drilling operations is called an influx or “kick.” By contrast, a fluid loss occurs when drilling fluid in the wellbore is lost to the formation. Both can have a number of detrimental effects. If a kick cannot be detected and controlled fast enough, it can escalate into an uncontrolled flow of formation fluids to the surface, which is called a “blow-out.” Consequences from a blow-out may vary from operational delays (non-productive time) to more severe damage to equipment.
- Hydrostatic pressure is a first conventional barrier for controlling the well from a “kick,” and blow out preventers (BOP) are a second barrier. In addition to these, other equipment and techniques can detect and handle a kick during drilling operations to maintain proper hydrostatic pressure in the well.
- For example, kick detection can be achieved by continuously monitoring the return flow (i.e., flow-out) in a closed-loop circulation system and comparing the flow-out to the flow-in to the closed-loop circulation system. Several controlled pressure drilling techniques have been used to drill wellbores with such closed-loop drilling systems. In general, the controlled pressure drilling techniques include managed pressure drilling (MPD), underbalanced drilling (UBD), and air drilling (AD) operations.
- In the Managed Pressure Drilling (MPD) technique, for example, the drilling system uses a closed and pressurizable mud-return system, a rotating control device (RCD), and a choke manifold to control the wellbore pressure during drilling. The various MPD techniques used in the industry allow operators to drill successfully in conditions where conventional technology simply will not work by allowing operators to manage the pressure and flow in a controlled fashion during drilling.
- As the bit drills through a formation, for example, pores become exposed and opened. As a result, formation fluids (i.e., gas) from an influx or kick can mix with the drilling mud. The drilling system then pumps this gas, drilling mud, and the formation cuttings back to the surface. As the gas rises up the borehole, the gas may expand, and hydrostatic pressure may decrease, meaning more gas from the formation may be able to enter the wellbore. If the hydrostatic pressure is less than the formation pressure, then even more gas can enter the wellbore.
- As a primary function, managed pressure drilling attempts to control such kicks or influxes of fluid. This can be achieved using an automated choke response in the closed and pressurized circulating system made possible by the rotating control device. A control system controls the chokes with an automated response by monitoring the flow-in and the flow-out of the well, and software algorithms in the control system seek to maintain a mass flow balance. If a deviation from mass balance is identified, the control system initiates an automated choke response that changes the well's annular pressure profile and thereby changes the wellbore's equivalent mud weight. This automated capability of the control system allows the system to perform dynamic well control or constant bottom hole pressure (CBHP) techniques.
- Even though pressure can be controlled during drilling operations using such controlled pressure drilling techniques discussed above, components and processes are needed to relieve overpressure to either protect the formation or to prevent damage to drilling equipment. A typical overpressure configuration uses a pressure relief valve having a control console that detects an overpressure condition and opens the pressure relief valve to relieve the pressure.
- For redundancy in a drilling system, the overpressure configuration simply includes a first pressure relief valve having its control console and includes a second, separate pressure relief valve having its own control console. In such an arrangement, limited protection can be achieved even though the configuration has some redundancy. For instance, a fault of one pressure relief valve would negate its use, but the other pressure relief valve with its console could assume overpressure protection. In like manner, a fault of one console would negate use of its pressure relief valve, but the other pressure relief valve with its console could assume overpressure protection. Yet, loss of rig power, loss of rig air supply, loss of sensor inputs, loss of communications, or any other number of faults could negate use of both pressure relief valves and/or consoles so overpressure protection would be lost.
- The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.
- According to the present disclosure, an assembly is used for relieving pressure of fluid flow in a drilling system in response to a pressure level measurement of the drilling system. The assembly comprises: pressure relief valves, hydraulic circuits, and controllers.
- The pressure relief valves are disposed in fluid communication between the fluid flow and at least one discharge outlet. Each of the pressure relief valves is operable to open and close fluid communication of the fluid flow with the at least one discharge outlet. The hydraulic circuits are cross-connected to one another and are operably connected to the pressure relief valves. The hydraulic circuits provide hydraulic motive force respectively to the pressure relief valves.
- The controllers are operably connected to the hydraulic circuits. Each of the controllers receives the pressure level measurement of the drilling system. Both of the controllers in a standard condition simultaneously control the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to independently open and close the respective pressure relief valve in response to the pressure level measurement. In response to a first failure condition of either one of the controllers, the other one of the controllers independently controls the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the pressure level measurement.
- In response to a second failure condition of either one of the hydraulic circuits, either one of the pressure relief valves can automatically fault closed regardless of the pressure level measurement.
- In one configuration, the assembly can comprise a manifold having the one or more flow inlets and having one or more flow outlets. The one or more flow inlets can be disposed in fluid communication with an upstream portion of the drilling system and can receive the fluid flow therefrom. The one or more flow outlets can be disposed in fluid communication with a downstream portion of the drilling system and can deliver the fluid flow thereto.
- In one configuration, the assembly can further comprise sensors communicatively connected to the controllers and providing readings for the pressure level measurement of the drilling system.
- In one configuration, the assembly can further comprise a plurality of sensors distributed in the hydraulic circuits and measuring a plurality of operational parameters. Both of the controllers can receive the operational parameters. Either one of the controllers can detect a second failure condition associated with the operational parameters from one of the hydraulic circuits and can automatically fault the respective pressure relief valve closed in response to the second failure.
- For this configuration, the hydraulic circuits can comprise pumps connected to a pneumatic supply and pumping the hydraulic motive force. A first of the sensors can comprise a first pressure transducer measuring pressure of the pneumatic supply as one of the operational parameters. The pumps connected to the pneumatic supply can pump the hydraulic motive force to a common hydraulic input for the hydraulic circuits, and a second of the sensors can comprise a second pressure transducer measuring the common hydraulic input as one of the operational parameters. One or more accumulators can be connected to the common hydraulic input. The hydraulic circuits can provide the hydraulic motive force in the event of failure of either one of the pumps.
- For this configuration having the sensors, a third of the sensors can comprise a third pressure transducer measuring pressure of the hydraulic motive force to a first the pressure relief valves as one of the operational parameters. Either one of the controllers can detect the measured pressure below a first threshold as the second failure condition and can automatically fault the first pressure relief valve closed in response thereto. Further, a fourth of the sensors can comprise a fourth pressure transducer measuring pressure of the hydraulic motive force to a second the pressure relief valves as one of the operational parameters. Either one of the controllers can detect the measured pressure below a second threshold as the second failure condition and can automatically fault the second pressure relief valve closed in response thereto.
- In one configuration, each of the controllers is communicatively connected to a position sensor of each of the pressure relief valves. Either one of the controllers can detect either one of the pressure relief valves failing to open as the second failure condition.
- In one configuration, each of the hydraulic circuits can comprise an electrically-driven directional control valve having a default no-flow state and an active flow state. Both of the electrically-driven directional control valves are connected to a common hydraulic input.
- In this configuration, each of the controllers can be communicatively connected to the electrically-driven directional control valves of both of the hydraulic circuits to provide a control signal thereto. In the second failure condition, either of the controllers can be configured to automatically fault a respective one of the pressure relief valves closed in response to a failure of the respective electrically-driven directional control valve; and/or the hydraulic motive force can be provided in the open circuit of a first of the hydraulic circuits in the event of a failure of the electrically-driven directional control valve in a second of the hydraulic circuits, where the pressure relief valve of the second hydraulic circuit defaults to a closed condition.
- In this configuration comprising electrically-driven directional control valves, each of the hydraulic circuits can comprise a pair of open and close hydraulically-driven directional control valves connected to the common hydraulic input. The open hydraulically-driven directional control valve can have a default closed state and an active opened state. The close hydraulically-driven directional control valve can have a default opened state and an active closed state. The active opened state can provide an open output of the hydraulic motive force to open the respective pressure relief valve. The default opened state can provide a close output of the hydraulic motive force to close the respective pressure relief valve. The open and close hydraulically-driven directional control valves can each have the respective default state in response to the electrically-driven directional control valve having the default no-flow state, and each can have the respective active state in response to the electrically-driven directional control valve having the active flow state.
- In this configuration comprising electrically-driven directional control valves, each of the hydraulic circuits can comprise a pair of discharge hydraulically-driven directional control valves. A first of discharge hydraulically-driven directional control valves can be connected to the open output and can have a default open state and an active close state. The default open state can communicate with a discharge. A second of the discharge hydraulically-driven directional control valves can be connected to the close output of the close hydraulically-driven directional control valve and can have a default closed state and an active opened state. The active opened state can communicate with the discharge. The discharge hydraulically-driven directional control valves can each have the respective default state in response to the electrically-driven directional control valve having the default no-flow state, and each can have the respective active state in response to the electrically-driven directional control valve having the active flow state. Each close output can comprise a pilot-operated check valve piloted by the respective open output.
- According to the present disclosure, an assembly is used with a buffer manifold for relieving pressure of fluid flow in a drilling system. The drilling system has a pneumatic supply, and the buffer manifold has one or more flow inlets, one or more flow outlets, and first and second pressure relief valves. The one or more flow inlets are disposed in fluid communication with an upstream portion the drilling system and receive the fluid flow therefrom. The one or more flow outlets are disposed in fluid communication with a downstream portion the drilling system and deliver the fluid flow thereto. The first and second pressure relief valves are disposed in fluid communication between the one or more flow inlets and the one or more flow outlets and are disposed in fluid communication with at least one discharge outlet. Each of the first and second pressure relief valves is operable to open and close fluid communication with the at least one discharge outlet.
- The control assembly comprises a hydraulic arrangement, a plurality of sensors, and a pair of controllers. The hydraulic arrangement is operably connected to the first and second pressure relief valves and is connected to the pneumatic supply. The hydraulic arrangement is powered by the pneumatic supply and provides hydraulic motive force in two hydraulic circuits respectively to the first and second pressure relief valves. The two hydraulic circuits are cross-connected to one another.
- The sensors are distributed in the hydraulic arrangement and measure a plurality of operational parameters of the hydraulic arrangement. The controllers are operably connected to the hydraulic arrangement. Each of the controllers receives the operational parameters from the sensors and receives a pressure level measurement of the drilling system. Both of the controllers control the hydraulic motive force provided in the two hydraulic circuits respectively to the first and second pressure relief valves to open and close the first and second pressure relief valves in response to the pressure level measurement.
- According to the present disclosure, a method of controlling fluid flow in a drilling system comprises: receiving the fluid flow from an upstream portion of the drilling system at one or more flow inlets of a manifold assembly; in response to a first pressure level measurement of the drilling system, flowing the fluid flow out one or more flow outlets of the manifold assembly to a first downstream portion of the drilling system in response thereto; in response to a second pressure level measurement of the drilling system, flowing the fluid flow out at least one discharge outlet of the manifold assembly to a second downstream portion of the drilling system, instead of out the one or more flow outlets, by simultaneously controlling, with controllers, hydraulic motive force provided in hydraulic circuits respectively to pressure relief valves to independently open the respective pressure relief valve; in response to a first failure condition of either one of the controllers, independently controlling, with the other one of the controllers, the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to simultaneously open and close the respective pressure relief valves in response to the first and second pressure level measurements; and in response to a second failure condition of either one of the hydraulic circuits, automatically faulting either one of the pressure relief valves closed regardless of the first and second pressure level measurements.
- To provide the hydraulic motive force in the hydraulic circuits of the hydraulic arrangement respectively to the pressure relief valves controlled by the controllers, the method can comprise powering pumping of the hydraulic motive force in n the hydraulic circuits with a pneumatic supply.
- In automatically faulting either one of the pressure relief valves closed, both of the pressure relief valves can be automatically faulted closed in response to a total loss of power.
- To automatically fault either one of the pressure relief valves closed, the method can comprise: measuring a plurality of operational pressures of the hydraulic arrangement using a plurality of pressure transducers distributed in the hydraulic arrangement; receiving the operational pressures from the pressure transducers at the controllers; and faulting the pressure relief valves closed in response to at least one of the operations pressure exceeding a pressure limit.
- To provide the hydraulic motive force in the hydraulic circuits of the hydraulic arrangement respectively to the pressure relief valves controlled by the controllers, the method can comprise routing the hydraulic motive force in the hydraulic circuits cross-connected to one another.
- To open the at least one pressure relief valve with the at least one controller in response to the second pressure level measurement, the method can comprise communicating both of the pressure relief valves in fluid communication between the one or more flow inlets and the one or more flow outlets and in fluid communication with at least one discharge outlet, each of the pressure relief valves being operable to open and close fluid communication with the at least one discharge outlet, both of the controllers operably connected to the hydraulic arrangement controlling the hydraulic motive force provided in the hydraulic circuits respectively to the pressure relief valves to open and close the pressure relief valves.
- The foregoing summary is not intended to summarize each potential embodiment or every aspect of the present disclosure.
-
FIG. 1 illustrates a drilling system according to the present disclosure. -
FIG. 2A illustrates a schematic view of a pressure relief system of the present disclosure for the drilling system. -
FIG. 2B illustrates an isolated view of a buffer manifold for the drilling system. -
FIG. 3 illustrates a graph of pressures used by the pressure relief system. -
FIG. 4 illustrates a cross-sectional view of a plug type valve for use as a pressure relief valve for the disclosed system. -
FIG. 5 illustrates a schematic view of a processing control unit for the disclosed pressure relief system. -
FIG. 6 illustrates a schematic view of a hydraulic control unit for the disclosed pressure relief system. -
FIG. 1 diagrams adrilling system 10 according to the present disclosure. As shown and discussed herein, thissystem 10 is a closed-loop system for controlled pressure drilling and can be a Managed Pressure Drilling (MPD) system and, more particularly, a Constant Bottomhole Pressure (CBHP) form of MPD system. Although discussed in this context, the teachings of the present disclosure can apply equally to other types of drilling systems, such as conventional drilling systems, other MPD systems (Pressurized Mud-Cap Drilling, Returns-Flow-Control Drilling, Dual Gradient Drilling, etc.) as well as to Underbalanced Drilling (UBD) systems, as will be appreciated by one skilled in the art having the benefit of the present disclosure. - The
drilling system 10 is depicted for use offshore on arig 12, such as a floating, fixed, or semi-submersible platform or vessel known in the art, although teachings of the present disclosure may apply to other arrangements. Thedrilling system 10 uses ariser 20 extending between adiverter 24 on therig floor 14 to a blow-out preventer stack 40 on the sea floor. Theriser 20 connects by a riser joint 22 from thediverter 24 and includes a rotating control device (RCD) 30, anannular isolation device 32, and aflow spool 34 disposed along its length. Adrill string 16 having a bottom hole assembly (BHA) and a drill bit extends downhole through theriser 20 and into awellbore 18 for drilling into a formation. - During operations, the
riser 20 can direct returns of drilling fluids, wellbore fluids, and earth-cuttings from thesubsea wellbore 18 to therig 12. In some conventional forms of operation, thediverter 24 can direct the returns of drilling fluid, wellbore fluid, and earth-cuttings to amud gas separator 90 and other element to separate out the drilling fluid for potential recycle and reuse, and to separate out gas. - In certain situations, the
BOP stack 40 can be operated to close off flow of the returns in theriser 20. TheBOP stack 40 may have one or more annular or ram-style blow out preventers on a subsea wellhead, and preventers on theBOP stack 40 can be controlled by various control lines (not shown) from equipment on therig 12. In certain situations of an uncontrolled release of wellbore fluids (e.g. high-pressure liquid and/or gas streams) during drilling, theriser 20 with itsrotating control device 30,annular isolation device 32, and flowspool 34 can be configured to divert the uncontrolled wellbore fluid flow in a controlled fashion as described below. - In managed pressure drilling, the
rotating control device 30, which can include any suitable pressure containment device, keeps thewellbore 18 in a closed-loop at all times while thewellbore 18 is being drilled. To do this, the rotating control device (RCD) 30 sealingly engages (i.e., seals against) thedrilling string 16 passing in theriser 20 and can contain and divert annular drilling returns through aflow line 31 c that connects to downstream flow controls on therig 12. In this way, therotating control device 30 can complete the circulating system to create the closed-loop of incompressible drilling fluid. - A
hydraulic power unit 31 a on therig 12 can connect bycontrol lines 31 b to therotating control device 30 to control its operation. The control lines 31 b can carry supply and/or return of hydraulic fluid to and from therotating control device 30 for its operation. - The
annular sealing device 32 can be used to sealingly engage (i.e., seal against) thedrillstring 16 or to fully close off theriser 20 when thedrillstring 16 is removed so fluid flow up through theriser 20 can be prevented. Typically, theannular sealing device 32 can use a sealing element that is closed radially inward by hydraulically actuated pistons.Control lines 33 from rig controls 57 can be used for controlling theannular sealing device 32. - The
flow spool 34 includes a number of controllable valves and connects byflow lines 35 to the downstream flow controls on therig 12 described below. The controllable valves of theflow spool 34 can be opened and closed usingcontrol lines 33 from the rig controls 57. - As shown in
FIG. 1 , the flow controls downstream of therotating control device 30, theannular sealing device 32, and theflow spool 34 include a managed pressuredrilling buffer manifold 60 and achoke manifold 70. Thebuffer manifold 60 connects by theflow lines rotating control device 30 and theflow spool 34 and receives flow returns during drilling operations. A buffer manifoldhydraulic power unit 55 operates thebuffer manifold 60. Among other components, thebuffer manifold 60 haspressure relief valves 64 a-b, pressure sensors (not shown), electronic valves (not shown), and other components to control operation of the manifold 60. - The
choke manifold 70 is downstream from thebuffer manifold 60. Thechoke manifold 70 can produce surface backpressure to perform managed pressure drilling with thedrilling system 10 and can measure parameters of the flow returns. Among other components, for example, thechoke manifold 70 has flow chokes 72, aflowmeter 74, pressure sensors (not shown), a local controller (not shown), and the like to control operation of the manifold 70. A hydraulic power unit (not shown) and/or electric motor of thechoke manifold 70 can actuate thechokes 72. - In addition to these components, the
system 10 also includes mud pumps 42; amud standpipe manifold 46 for a standpipe (not shown); a choke & killmanifold 80 having kill and chokelines BOP stack 40; amud gas separator 90; and various other components. During drilling operations, these components can operate in a known manner. - Finally, a
control system 50 of thedrilling system 10 integrates hardware, software, and applications across thedrilling system 10 and is used for monitoring, measuring, and controlling parameters in thedrilling system 10. For example, thecontrol system 50 can be integrated with or communicatively coupled to the RCDhydraulic power unit 31 a, the buffer manifoldhydraulic power unit 55, thebuffer manifold 60, thechoke manifold 70, and other components. During standard operating conditions, thedrilling control system 50 operates the various components to operate thedrilling system 10. - In the contained environment of the closed-
loop drilling system 10, for example, minute influxes or losses in thewellbore 18 are detectable at the surface, and thecontrol system 50 can further analyze pressure and flow data to detect kicks, losses, and other events. In turn, at least some operations of thedrilling system 10 can then be automatically handled by thecontrol system 50. - To monitor operations, the
control system 50 can use data from a number of sensors and devices in thesystem 10. For example, one or more sensors can measure pressure in the standpipe. One or more sensors (La, stroke counters) can measure the speed of the mud pumps 42 for deriving the flow rate of drilling fluid into thedrillstring 16. In this way, flow into thedrillstring 16 may be determined from strokes-per-minute and/or standpipe pressure. - One or more sensors can measure the volume of fluid in the
mud tanks 44 and can measure the rate of flow into and out ofmud tanks 44. In turn, because a change in mud tank level can indicate a change in drilling fluid volume, flow-out of thewellbore 18 may be determined from the volume entering themud tanks 44. - Rather than relying on conventional pit level measurements, the
control system 50 can use theflowmeter 74, such as a Coriolis mass flowmeter, on thechoke manifold 70 to capture fluid data—including mass and volume flow, mud weight (i.e., density), and temperature—from the returning annular fluids in real-time, at a sample rate of several times per second. Because the Coriolis flowmeter gives a direct mass rate measurement, theflowmeter 74 can measure gas, liquid, or slurry. Other sensors can be used, such as ultrasonic Doppler flowmeters, SONAR flowmeters, magnetic flowmeter, rolling flowmeter, paddle meters, etc. - Additional sensors can measure mud gas, flow line temperature, mud density, and other parameters. For example, a flow sensor can measure a change in drilling fluid volume in the well. Also, a gas trap, such as an agitation gas trap, can monitor hydrocarbons in the drilling mud at surface. To determine the gas content of drilling mud, for example, the gas trap mechanically agitates mud flowing in a tank. The agitation releases entrained gases from the mud, and the released gases are drawn-off for analysis. The spent mud is simply returned to the
tank 44 to be reused in thedrilling system 10. - During operations, the
drill string 16 passing from therig 12 can extend through theriser 20 and through theBOP stack 40 for drilling thewellbore 18. As thedrillstring 16 is rotated, therotating control device 30 seals the annulus between the drillstring 16 and theriser 20 to conduct a managed pressure drilling operation. In this way, flow returns having drilling fluid, wellbore fluid, and cuttings flow up through the annulus between the drillstring 16 and theriser 20 to therotating control device 30, which diverts the flow returns through theflow line 31 c to thebuffer manifold 60. - The fluid data and other measurements noted herein are transmitted to the
control system 50, which in turn operates drilling functions. In particular, thecontrol system 50 can operate theautomated choke manifold 70, which manages pressure and flow during drilling and which is incorporated into thedrilling system 10 downstream from therotating control device 30 andbuffer manifold 60 and upstream from thegas separator 90. - In general, the
buffer manifold 60 can direct the flow returns in various way as needed. During standard operating conditions, thebuffer manifold 60 passes the flow returns to thechoke manifold 70. Theautomated choke manifold 70 measures the return flow (e.g., flow-out) and density using theflowmeter 74 installed in line with thechokes 72. Software components of thecontrol system 50 then compares the flow rate in and out of thewellbore 18, the injection pressure (or standpipe pressure), the surface backpressure (measured upstream from the drilling chokes 72), the position of thechokes 72, and the mud density, among other possible variables. Comparing these variables, thecontrol system 50 then identifies minute downhole influxes and losses on a real-time basis and control surface backpressure with thechokes 72 to manage the annulus pressure during drilling. - By identifying the downhole influxes and losses during drilling, for example, the
control system 50 monitors circulation to maintain balanced flow for constant BHP under operating conditions and to detect kicks and lost circulation events that jeopardize that balance. The drilling fluid is continuously circulated through thesystem 10, thebuffer manifold 60, thechoke manifold 70, and theflowmeter 74. As will be appreciated, the flow values may fluctuate during normal operations due to noise, sensor errors, etc. so that thesystem 50 can be calibrated to accommodate such fluctuations. In any event, thecontrol system 50 measures the flow-in and flow-out of the well and detects variations. In general, if the flow-out is higher than the flow-in, then fluid is being gained in thesystem 10, indicating a kick. By contrast, if the flow-out is lower than the flow-in, then drilling fluid is being lost to the formation, indicating lost circulation. - To then control pressure, the
control system 50 introduces pressure and flow changes to the incompressible circuit of fluid at the surface to change the annular pressure profile in the wellbore. In particular, using thechoke manifold 70 to apply surface backpressure within the closed loop, thecontrol system 50 can produce a reciprocal change in bottom hole pressure. In this way, thecontrol system 50 uses real-time flow and pressure data and manipulates the annular backpressure to manage wellbore influxes and losses. - During operations, certain events may occur that require reconfiguring of flow controls. For example, the
drillstring 16 may be lifted out of theriser 20, and theannular sealing device 32 may be actuated to close off theriser 20. The controllable valves on theflow spool 34 can be operated to direct fluid in theriser 20 below therotating control device 32 through theflow lines 35 to thebuffer manifold 60. - In other examples, certain events or failures, such as an uncontrolled release of wellbore fluids, may occur. In this case, the
annular sealing device 32 can be actuated to seal off the annulus around the drillstring 16 (if present). The rotation of thedrillstring 16 can be stopped during the event, or theannular sealing device 32 may be capable of sealing against thedrillstring 16 while rotating. Either way, the controllable valves on theflow spool 34 can be operated to direct fluid in theriser 20 below theannular sealing device 32 through theflow lines 35 to thebuffer manifold 60. - Additional events may occur requiring the
pressure relief system 100 to divert fluid flow overboard, to triptanks 44, or to other fluid handling components. For example, an uncontrolled release of wellbore fluids may occur, and the annular flow in theriser 20 captured by therotating control device 30 or theannular sealing device 32 may need to be relieved to protect the formation or to protect the equipment of the system. To relieve thesystem 10 of overpressure, apressure relief system 100 operatespressure relief valves 64 a-b on thebuffer manifold 70 to divert the flow returns from theflow lines tanks 44, or to other fluid handling components. This diversion can then prevent the overpressure flow from damaging theriser 20 and passing on to thechoke manifold 70. - As schematically shown, components of the
pressure relief system 100 can be incorporated into the bufferhydraulic power unit 55, although separate configurations are possible. As discussed in more detail below, thepressure relief system 100 has an integrated PLC based control system and a hydraulic control unit (HCU) and is connected to thepressure relief valves 64 a-b and other components of thebuffer manifold 60 bycontrol lines 105. Thepressure relief system 100 can open and close thepressure relief valves 64 a-b simultaneously. When opened, the redundantpressure relief valves 64 a-b provide pressure relief in the event of over-pressurization of thewellbore 18 and/or surface equipment. Once opened, thepressure relief system 100 provides a further function of closing thepressure relief valves 64 a-b to prevent an induced kick from occurring after the relief of overpressure. - The
pressure relief valves 64 a-b are configured to nominally fail in the closed position. There may be several reasons for this. Primarily, the purpose of theMPD drilling system 10 is to impose dynamic backpressure on thewellbore 18 using thechoke manifold 70. If one of thepressure relief valve 64 a-b fails open, then backpressure cannot be maintained. Additionally, thewellbore 18 is normally in static or dynamic balance so a demand for overpressure protection of equipment is less likely to occur. Instead, the more likely cause of an open command to thepressure relief valves 64 a-b would be to protect the formation. - As hinted to above, the
pressure relief system 100 can operate in a stand-alone mode to protect against process upsets during drilling with thedrilling system 10. As schematically shown inFIG. 2A , thepressure relief system 100 includes asensor arrangement 110, aprocessing control unit 120, and ahydraulic control unit 130 for thebuffer manifold 60. Power from apower supply 140 can be common to the threeelements system 100. - As described in more detail below, each of the
elements system 100 is more than just a combination of one pressure relief valve having its control console with another pressure relief valve having its own control console. In such an arrangement, limited fault protection would be achieved as discussed in the background section of the present disclosure. Instead, thepressure relief system 100 disclosed herein addresses multiple points of failure in the disclosed arrangement by providing a redundancy at that point of failure, by providing independent monitoring of that point of failure, and by preventing a fault at that point of failure from translating to a fault of the redundancy. In this way, the disclosedpressure relief system 100 provides a redundant, fault-tolerant integration of sensing, processing, hydraulic, andpower elements pressure relief valves 64 a-b. - As briefly shown here and described in more detail below, the
sensor arrangement 110 includessensors electrical buffers 114, and theprocessing control unit 120 includes two programmable logic controllers (PLCs) 122 a-b. Thehydraulic control unit 130 provides hydraulic valve control for the twopressure relief valves 64 a-b of the manifold 60. - The sensors in the
arrangement 110 includetransducers 112 receiving pressure and other measurements from pneumatic and hydraulic sources. Thesetransducers 112 can be distributed in thehydraulic control unit 130 in themanifold 60. The sensors in thearrangement 110 also includesensors 116 receiving line or process pressures from the drilling system (10). Thesesensors 116 can be disposed on the flow line entering theinlet 62 a of thebuffer manifold 60. Thesesensors 116 measure redundant measurements of the process pressure, and voting between the sensor measurements can be used in decisions of theprocessing control unit 120. - The
buffer manifold 60 inFIG. 2A is used for directing process flow in various ways. The manifold 60 includes one ormore flow inlets 62 a disposed in fluid communication with an upstream portion of the drilling system (10) and receives the fluid flow therefrom. The manifold 60 also includes one ormore flow outlets 62 b disposed in fluid communication with a downstream portion of the drilling system (10) and delivers the fluid flow thereto. Finally, the manifold 60 includes at least onedischarge outlet 65 to relieve pressure. - In the context of the present disclosure, the
pressure relief valves 64 a-b are used for relieving pressure of fluid flow in the drilling system (10:FIG. 1 ) in response to a pressure level measurement, such as a flow line pressure from thesensors 116, being over a limit. For instance, as shown inFIG. 2B , the manifold 60 has a number ofinlets 62 a and receives fluid from the RCD (30) viaflow lines 31 c, receives flow from the flow spool (34) viaflow lines 35, receives flow from the choke/kill manifold (80), etc. The manifold 60 has a number ofoutlets 62 b and delivers flow returns to the choke manifold (70), to the choke/kill manifold (80), trip tank (44), and other downstream portions of the drilling system (10) instead of to the choke manifold (70). - Internally, the manifold 60 includes a number of solenoid actuated
gate valves 66, flow tees, manifold elements, piping, etc. for controlling flow between theinlets 62 a and theoutlets 62 b during drilling operations. Thebuffer unit 55 interfaces with the solenoid actuatedgate valves 66 for directing flow according to operational needs. For its part, thepressure relief system 100, which can part of thebuffer unit 55 and which includes theelements FIG. 2A interfaces with thepressure relief valves 64 a-b to relieve overpressure from theinlets 62 a to thedischarge outlets 65. - As can be seen in the manifold 60 as shown in
FIGS. 2A-2B , the redundantpressure relief valves 64 a-b are disposed in fluid communication between the one ormore flow inlets 62 a and the one ormore flow outlets 62 b and disposed in fluid communication with the at least onedischarge outlet 65. Each of the redundantpressure relief valves 64 a-b is operable to open and close fluid communication with the at least onedischarge outlet 65. - The
hydraulic control unit 130 inFIG. 2A has a hydraulic arrangement operably connected to the redundantpressure relief valves 64 a-b. Redundant hydraulic circuits of theunit 130 are cross-connected to one another and are operably connected to the redundantpressure relief valves 64 a-b. The redundant hydraulic circuits provide hydraulic motive force respectively to the redundantpressure relief valves 64 a-b. - The
transducers 112 are distributed in the redundant hydraulic circuits of thehydraulic control unit 130 and measure operational parameters of the hydraulic circuits to diagnose theunit 130 and its operation. Theother sensors 116 are distributed to measure line or process pressure of the manifold'sinlets 62 a as the pressure level measurement used in activating or deactivating thepressure relief system 100. Thesesensors 116, for example as shown inFIG. 2B , can be disposed on theflow line 31 c from the RCD (30) leading into theinlet 62 a of thebuffer manifold 60. - In general, two or more of these
sensors 116 can be used for redundancy. In a particular arrangement, foursensors 116 can be used to measure the process pressure at the same point of the flow line to theinlet 62 a. Each of thesesensors 116 can be the same as one another (i.e., have the same ratings, same sensitivities, etc.) for redundant verification of the pressure measurements. In fact, thesensors 116 can be identical. In other arrangements, one or more of thesensors 116 may have different ratings, sensitivities, or the like from theother sensors 116. - In the
processing unit 120, the redundant controllers 122 a-b are operably connected to the redundant hydraulic circuits of thehydraulic control unit 130. Each of the redundant controllers 122 a-b receives the operational parameters from thetransducers 112 and also receives pressure level measurements of the drilling system (10) for thesensors 116. Both of the redundant controllers 122 a-b in a standard operating condition then simultaneously control the hydraulic motive force provided in the redundant hydraulic circuits of thehydraulic unit 130 respectively to the redundantpressure relief valves 64 a-b to independently open and close the respectivepressure relief valve 64 a-b in response to the pressure level measurement from theline pressure sensors 116. - Additional details of the
processing unit 120 are disclosed inFIG. 5 , and additional details of thehydraulic control unit 130 are disclosed inFIG. 6 . - The
system 100 is a redundant, fault tolerant, pressure protection system used in the operation of the twopressure relief valves 64 a-b intended for protection of process or line pressure in the drilling system (10:FIG. 1 ). For fault tolerance, thepressure relief system 100 is operable in response to different failure or fault conditions. In response to a first failure condition of either one of the redundant controllers 122 a-b, for example, the other one of the redundant controllers 122 a-b independently controls the hydraulic motive force provided in the redundant hydraulic circuits of thehydraulic unit 130 respectively to the redundantpressure relief valves 64 a-b to simultaneously open and close the respectivepressure relief valves 64 a-b in response to the pressure level measurement from theline pressure sensors 116. In response to a second failure condition of either one of the redundant hydraulic circuits of thehydraulic unit 130, however, either one of the redundantpressure relief valves 64 a-b automatically faults closed regardless of the pressure level measurement from theline pressure sensors 116. - In the configuration of the manifold 60, one
pressure relief valve 64 a-b and its associated electrical, hydraulic, or pneumatic controls is capable of relieving excess line pressure. In case of single point failure failing onepressure relief valve 64 a-b, the failedpressure relief valve 64 a-b fails closed allowing the remainingpressure relief valve 64 a-b and its associated electrical, hydraulic, or pneumatic controls to continue to maintain control over line pressure and relieve pressure as needed. (As to be understood herein, having a valve “fail closed” refers to the failed valve closing, as opposed to the valve simply failing-in-place—i.e., the valve staying in its current position.) - For overpressure protection, the
pressure relief system 100 is controlled by a user-definedsetpoint 124, which can be set over a pressure range to a codedequipment protection setpoint 126. The user-definedsetpoint 124 can be entered locally at a console or remotely by computer using an interface application. Under normal operation, exceeding thesetpoint 124 for line pressure causes bothpressure relief valves 64 a-b to open to relieve line pressure. Thereafter, when line pressure is reduced, bothpressure relief valves 64 a-b then close. - For additional reference,
FIG. 3 illustrates a graph of pressure set points and values used by thepressure relief system 100. The user-definedsetpoint 124 to open the twopressure relief valve 64 a-b is a dynamic process protection level (PPL)setpoint 124, which extends over a pressure range from 0 to a hard-coded equipment protection level (EPL)setpoint 126. - The
dynamic setpoint 124 is the “open” setpoint for thepressure relief valves 64 a-b, indicating the pressure level set for thepressure relief valves 64 a-b to open and relieve process pressure for overpressure protection. Thedynamic setpoint 124 allows operators to limit the applied surface backpressure while (a) drilling narrow margin wells (well protection setpoint) and while (b) during short periods for make and break of drilling stands (connections setpoint.) - The
equipment protection setpoint 126 is hard-coded and is set based on the lowest pressure rating. The dynamic setpoint 124 (valve opens) may cover a range of pressure from 0 to 80% of riser (or surface equipment) maximum allowable operating pressure (MAOP). Typically, the MAOP is separately hard coded into the programmable logic controllers 122 a-b to protect the riser (20) and surface equipment (60, 70, etc.). - During operation, the process sensors (116) measure the process pressure at the inlet (62 a) of the manifold (60) to provide the current line or
process pressure 128. Becausemultiple sensors 116 are used, a voting scheme between the sensors' measurements can be used to decide what thecurrent line pressure 128 is. For example, the voting scheme can decide thepressure 128 from an average of the three closest measurements, or some other scheme can be used. Thus, if onesensor 116 makes a momentary erroneous measurement, it need not be relied upon. - The
current line pressure 128 is compared to thedynamic setpoint 124, which can be changed, for example, (a) during drill-pipe make-and-break, (b) as the wellbore (18) is deepened and new geological structures are encountered, and (c) when conducting formation integrity tests (FIT) or leak off tests (LOT). Therefore, as the drilling process goes through different operations, thedynamic setpoint 124 is changed so overpressure protection is provided in the manner best suited to the drilling operations at the time. - Under normal operation, having the
current line pressure 128 exceed thedynamic setpoint 124 results in bothpressure relief valves 64 a-b opening simultaneously in order to reduce pressure. Thereafter, bothpressure relief valves 64 a-b close at a trailingsetpoint 125 in order to prevent an induced kick from occurring due to the relief of pressure. The trailingsetpoint 125 is the close setpoint for when thevalves 64 a-b close after opening. The trailingsetpoint 125 may be hard coded at 80% of the dynamicopen setpoint 124. - For its part, the hard-coded
equipment protection setpoint 126 simultaneously opens bothpressure relief valves 64 a-b in order to protect the riser (20) and surface equipment from overpressure. Although one form of voting between the measurements of the pressure sensors (116) can be used to determine whether thecurrent line pressure 128 has reached theequipment protection setpoint 126, preferably theequipment protection setpoint 126 is triggered by another form of voting when any one of thepressure sensors 116 reports a measured value exceeding theequipment protection setpoint 126. - After opening due to triggering from the
equipment protection setpoint 126, bothpressure relief valves 64 a-b then close at a trailing setpoint (not shown) in order to prevent an induced kick. As noted, the openequipment protection setpoint 126 is nominally set at 80% of maximum allowable operating pressure (MAOP). The trailing close setpoint used after opening for the equipment protection may correspond to the dynamicclose setpoint 124. This may ensure that the well is bought back to a state previously identified as being required to drill the wellbore or make the connection. - The
dynamic setpoint 124 allows backpressure adjustment during make-and-break of drillpipe of the drillstring (16). When making connections in the system (10) ofFIG. 1 , for example, the mud pumps (42) are stopped prior to making a connection. This results in a loss of equivalent circulating density (ECD), which in turn reduces downhole pressure. The drilling system (10) is used to compensate for the loss of ECD by increasing the backpressure applied at the chokes (72) of the choke manifold (70). The increase in backpressure may be several hundred PSI, which means thedynamic setpoint 124 must be increased to a value equal to surface backpressure (SBP) plus a margin (M) that prevents the pressure relief valves (64 a-b) from opening erroneously. In practice, the adjustment of thedynamic setpoint 124 may be reviewed with the connection every drillpipe stand. However, if the ‘open’dynamic setpoint 124 is triggered, then there is a risk of an influx that could escalate to a loss of well control. For this reason, the processing unit (120) is programmed to close the pressure relief valves (64 a-b) with the trailing ‘close’setpoint 125. - The
dynamic setpoint 124 also provides wellbore protection while drilling. For example, the pressure relief valves (64 a-b) must open at adynamic setpoint 124 chosen by the driller whose goal is to protect the open formation against fracture. If the hydrostatic and applied backpressure from the column of drilling mud is too high, then drilling fluid may be lost into the formation. The dynamicopen setpoint 124 may be up to 80% of MAOP (e.g. if RCD is rated for 2000 psi, 80% of the MAOP is 1600 psi), leaving no pressure margin and time-delay between relief for well protection, and equipment overpressure. Opening the pressure relief valves (64 a-b) results in a significant and rapid loss of surface back pressure, so both pressure relief valves (64 a-b) preferably close at the trailingsetpoint 125 to minimize an induced kick. The trailingclose setpoint 125 may be set at 80% of the dynamicopen setpoint 124. If thedynamic setpoint 124 is set high and one or both pressure relief valves (64 a-b) fails to close, then there is the risk of an induced kick that could escalate to blow out after a period of minutes or hours. In this situation, the driller would have to secure the well. - Other than the modes of operation for making connections and well protection, the
pressure relief system 100 operates in an equipment protection mode to open and close in emergency scenarios where high surface pressure (i.e., overpressure) is detected in the line pressure at the inlets (62 a) of the manifold (60). There are two primary scenarios. First, the return flow path of the MPD system (10) is blocked (e.g. by an inadvertently closed valve). Alternatively, a gas kick has been transported or migrated to surface, resulting in a threat of equipment overpressure. In both cases, the pressure relief valves (64 a-b) open at thedynamic setpoint 124 to relieve pressure and then close at the trailingsetpoint 125 to maintain backpressure on the well. - The programming in the controllers (122 a-b) for the
dynamic setpoint 124 does not allow the operator to enter a value greater than theopen setpoint 126 for equipment protection. This means the dynamicopen setpoint 124 operates first, thereby preventing conflicting commands from the controllers (122 a-b) (i.e., simultaneous close fordynamic setpoint 124, and open for equipment protection 126). - The
pressure relief valves 64 a-b of the disclosedpressure relief system 100 can be a plug type valve rated for high-pressure service in drilling applications, although other types of valves, chokes, and the like can be used. As a brief example,FIG. 4 schematically illustrates a plug type valve that can be used for the system'spressure relief valve 64. Thevalve 64 includes abody 150, aplug 160, and ahydraulic actuator 168. - An interior 152 of the
valve body 150 has aninlet 154 and anoutlet 156 with aseat 155 disposed therebetween. Theplug 160 is sealed in the interior 152 and is movable relative to theseat 155. As shown here, thehydraulic actuator 168 is a piston connected to theplug 160 by astem 162. Theactuator 168 is sealed in ahydraulic chamber 158 communicating with hydraulic ports 159 a-b. Other hydraulic arrangements, such as scroll screw actuators, choke actuators, or the like, can be used for theactuator 168. - Operation of the
valve 64 is achieved via thehydraulic actuator 168 integral to theplug 160. The air-driven hydraulic power unit (130:FIG. 2A ) provides motive force to theactuator 168 via the ports 159 a-b. A position orproximity sensor 157 can be used with theactuator 168 to at least indicate that thevalve 64 is open. - The
valve 64 is held closed by line pressure at theinput 154 acting against theplug 160 and by application of the piston force of theactuator 168. Reversing the hydraulic pressure acting across theactuator 168, to a point where piston force exceeds well fluid force, opens thevalve 64. This moves theplug 160 off theseat 155 at which point downstream pressure assists opening, and line flow can pass from theinlet 154 to theoutlet 156. -
FIG. 5 illustrates a schematic of theprocessing control unit 120 for the disclosedpressure relief system 100. Theprocessing control unit 120 uses an electric control panel containing duplicate power input sources (AC-1, AC-2),duplicate power supplies 140, redundant failsafe programmable logic controllers (PLC) 122 a-b, and redundant sensor inputs via acommunication interface 105 with the hydraulic control unit (130). - The
processing unit 120 can further use fusing to prevent cascade electrical faults, a connection for alocal HMI display 104 a, and a fiber optic interface for remote operation byother processing equipment 104 b, such as in a driller's cabin on the rig. Instrumentation can be included to reveal any electronic failure of components. The local and remote interfaces 104 a-b are redundant of one another so one could be used in the absence or failure of the other. In general, the interfaces 104 a-b can provide setup, configurations, alarms, diagnostics, and the like for both controllers 122 a-b. - The two programmable logic controllers 122 a-b operate in a fully parallel, redundant configuration. The controllers 122 a-b can be powered by the duplicate AC power input sources (AC-1, AC-2), and duplicate DC power supplies 140. One power source (AC-1) can be rig power, while the other power source (AC-2) can be an uninterruptable power supply. A router for communications may or may not be necessary.
- The redundant sensor inputs of the
interface 105 can be protected by theelectrical barriers 114 having fuses to prevent a cascade of electrical faults. Each controller 122 a-b can be connected to the common,local HMI display 104 a. The fiber optic interface may support remote monitoring and basic process control via interface applications withremote processing equipment 104 b. The interface electronics configuration is redundant and fault tolerant. - Identical logic can run on each controller 122 a-b. Thus, each controller 122 a-b receives input from the same sources. For example, each controller 122 a-b receives input from the
transducers 112 a-d distributed in the hydraulic power unit (130), receives position sensing input 107 a-b from the pressure relief valves (64 a-b), and receives input from theprocess sensors 116 a-d of the manifold (60). Each of the various pressure transducers and sensors (112 a-d, 116) can be installed in a location and orientation designed to sense line blockage. - Each controller 122 a-b uses a voting scheme for the measurements of the
process sensors 116 a-d, and each controller 122 a-b processes the inputs with the identical logic. In turn, each controller 122 a-b provides control signals through outputs 106 a-b to the pressure relief valves (64 a-b). Therefore, the controllers 122 a-b should operate the same and should produce the same processing results. In this way, the controllers 122 a-b simultaneously operate the twopressure relief valves 64 a-b, yet do their processing independently. - Diagnostics from each individual controller 122 a-b may or may not be included in the logic. Such diagnostics may or may not be communicated between the controllers 122 a-b. If diagnostics are shared, each controller 122 a-b can operate according to an appropriate voting scheme to resolve conflicts between any processing results. Alternatively, the controller 122 a-b with superior diagnostics may override the other. In fact, one controller 122 a-b may operate on standby, awaiting its need to assume control from the other controller 122 a-b. Preferably, however, both controllers 122 a-b as noted herein simultaneously process the inputs and provide their independent results, which should be identical or nearly identical under the circumstances.
- During normal operation with no faults, both controllers 122 a-b and their associated electronics can operate both pressure relief valves (64 a-b) simultaneously, but independently. As shown, each controller 122 a-b shares a
first control output 106 a to open the first pressure relief valve (64 a), and each controller 122 a-b shares asecond control output 106 b to open the second pressure relief valve (64 b). Each valve (64 a-b) is, however, independently capable of the needed open/close functions. In the event of a failure of either one of the controllers 122 a-b or its associated electronics, the remaining controller 122 a-b and associated electronics can continue to operate bothpressure relief valves 64 a-b. - As shown, each controller 122 a-b also shares the
communication interface 105 connected to thetransducers 112 a-d of the hydraulic control unit (130). Theinterface 105 includes connections to afirst transducer 112 a for measuring the pneumatics for the manifold (60) and connections toother transducers 112 b-d for measuring the hydraulics for the manifold (60), as described later. Thecommunication interface 105 includes a connection to alevel indicator 112 e for receiving an indication of hydraulic level of the hydraulic control unit (130). In this way, thetransducers 112 a-e provide diagnostics of the hydraulic unit (130). - As shown, each controller 122 a-b also shares communication with the
sensors 116, which can be pressure transducers that redundantly measure the line pressure to detect an overpressure condition requiring pressure relief by thepressure relief system 100. Thesepressure transducers 116 can have the same or different ranges, alarms, sensitivities, etc. Thecommunication interface 105 also includes a first connection (PRV1 ZT1) to a first position sensor (157) for the first pressure relief valve (64 a), and includes a second connection (PRV2 ZT2) to a second position sensor (157) for the second pressure relief valve (64 b). In general, the position sensors (157) can indicate if the associatedvalve 64 a-b is fully open. -
FIG. 6 illustrates a schematic of ahydraulic control unit 130 for the disclosed pressure relief system (100). As shown inFIG. 6 , thehydraulic control unit 130 consists of redundant hydraulic, pneumatic, and electrical components. Field deployment usesbulkhead connections 170 forrig air supply 172,sensors connections 112 a-d, and hydraulic connections 174 a-b. Hydraulics controls consist of dual air driven pumps 186 a-b,dual accumulators 188 a-b, and hydraulic circuits 180 a-b cross-connected for redundancy. Each half of the duplicated components is sized to operate bothpressure relief valves 64 a-b simultaneously. - The two hydraulic circuits 180 a-b operate the
pressure relief valves 64 a-b independently. Each circuit 180 a-b includes a spring-biased (to default close) solenoid operated directional control valve (DCVs) 192 a-b. Each electrically-operated valve (DCVs) 192 a-b in turn energizes four (4) hydraulically-operated directional control valves (DCVs) 194 a-d, 196 a-d. Based on the control of these valves 192 a-b, 194 a-b, 196 a-b, each circuit 180 a-b deliversopen pressure 174 a andclose pressure 174 b for the motive force of the pressure relief valves (64 a-b). - To do this, rig
air supply 172 for the circuits 180 a-b is split and passes through filter-regulator-lubricator components 181 a-b to pneumatic pumps 186 a-b. Hydraulic fluid from ahydraulic source 182 is drawn by the pneumatic pumps 186 a-b through suction lines 184 a-b. From the pneumatic pumps 186 a-b, the hydraulics pass components 187 a-b of pressure relief valves, check valves, and the like. The hydraulics then combine together in a commonhydraulic input 188 and pass connections to theaccumulators 188 a-b. Theaccumulators 188 a-b can take over in maintaining the hydraulic pressure should therig air supply 172 fail or both of the pumps 180 a-b fail. Moreover, one of theaccumulators 188 a-b can take over for the other should it fail. - The combined pumped
hydraulic input 188 then pass to split controls 190 a-b, each having an electrically-driven directional control valve 192 a-b. The first electrically-drivenvalve 192 a operates to open/close the first of the pressure relief valves (64 a) and receives first control signals (106 a:FIG. 5 ) from either of the controllers 122 a-b of the processing control unit (120). The second electrically-drivenvalve 192 b operates to open/close the second of the pressure relief valves (64 b) and receives first control signals (106 b:FIG. 5 ) from either of the controllers (122 a-b) of the processing control unit (120). - As noted herein, each electrically-driven valve 192 a-b receives an input signal from both of the controllers 122 a-b. In this way, an input signal to actuate the electrically-driven valves 192 a-b and open the
pressure relief valve 64 a-b can be received from one or both of the controllers 122 a-b. Because each of the electrically-driven valves 192 a-b shares two electrical connections with the controllers 122 a-b, each connection needs to be isolated from the other so that a short of one connection does not translate to a short of the other. In other words, a short of the electrical connection of onecontroller 122 a to the electrically-drivenvalve 192 a should not cause a short of the electrical connection of theother controller 122 b to the electrically-drivenvalve 192 a. As will be appreciated, each of the electrical connections between components of the control unit (120) and thehydraulic control unit 130 for the various shared sensors, signals, inputs, outputs, and the like are likewise isolated to prevent a short of one translating to a short of another. - Each electrically-driven valve 192 a-b has a set of four hydraulically-operated directional control valves (DCVs) 194 a-d, 196 a-d, which are stacked as piloted valves with reduced leakage in the hydraulic arrangement. The combined pumped hydraulics pass to both the electrically-driven valves 192 a-b and also split to pass to the open and close hydraulically-driven valves 194 a-b, 196 a-b. Respective output from the split controls 190 a-b pass pilot-operated check valves 198 a-b before reaching the
open connections 174 a and theclose connections 174 b on thebulkhead 170 for the twopressure relief valves 64 a-b. - Looking at the
first circuit 180 a, the first electrically-drivenvalve 192 a has a default state, including (3 closed) closing off communication of the pumped hydraulics and including (1-2 pass) connecting the pressure inputs (3) of the hydraulically-operated valves 194 a-d to thedischarge line 185. The first electrically-drivenvalve 192 a has an active state, including (3-2 pass) and including (1 closed) directing the pumped hydraulics to the pressure inputs (3) of the hydraulically-operated valves 194 a-d. - The open hydraulically-driven
valve 194 a has a default closed state (2 closed, 1 closed) and has an active opened state (2-1 pass) when hydraulically driven by pressure input (3). The close hydraulically-drivenvalve 194 b has a default opened state (2-1 pass) and has an active closed state (2 closed, 1 closed) when hydraulically driven by pressure input (3) shared with the open hydraulically-drivenvalve 194 a. - The other hydraulically-driven
valves 194 c-d control communication from the open and close hydraulically-driven valve 194 a-b to thedischarge line 185. Thesevalves 194 c-d share pressure inputs (3) selectively connected by the electrically-drivenvalves 192 a to thedischarge line 185 or the combined pumped hydraulics. One of thesevalves 194 c has a default state, including (2-closed, 1-closed) preventing communication of the output from theclose valve 194 b to thedischarge line 185, and has an active state, including (1-2 pass) communicating the output from theclose valve 194 b to thedischarge line 185. The other of thesevalves 194 d has a default state, including (1-2 pass) communicating the output from theopen valve 194 a to thedischarge line 185, and an active state, including (2-closed, 1-closed) preventing communication of the output from theopen valve 194 a to thedischarge line 185. - The electrically-driven
valve 192 b and hydraulically-driven valves 196 a-d for thesecond circuit 180 b are similarly configured. Therefore, the above discussion is reincorporated here, applying to the connections between the electrically-drivenvalve 192 b and the hydraulically-driven valves 196 a-d for thesecond circuit 180 b. - Instrumentation is included to monitor critical pneumatic and hydraulic functions to reveal any hydraulic or pneumatic component or circuit failure. In particular, the instrumentation includes the
transducers 112 a-d, which connect via buffers (114) to the processing unit's interface (105:FIG. 5 ) for the controllers (122 a-b) of the processing control unit (120). Thefirst transducer 112 a measures theair supply 172 for the pumps 186 a-b. Thesecond transducer 112 b measures the hydraulic power unit's pressures for the two circuits 180 a-b. Thethird transducer 112 c measures the pressure relief valve's pressure for thefirst circuit 180 a, and thefourth transducer 112 d measures the pressure relief valve's pressure for thesecond circuit 180 b. Thelevel indicator 112 e measures the level of hydraulic fluid in thehydraulic source 182. - In the event of failure of any critical hydraulic or pneumatic component (worst case), only one
pressure relief valve 64 a-b fails and remains closed while the otherpressure relief valve 64 a-b continues to operate normally and relieves line pressure as needed. Preferably then, no single point failure in the electrical, hydraulic, or pneumatic controls of the processing unit (120) and hydraulic control unit (130) prevents operation of at least onepressure relief valve 64 a-b when needed. - The
pressure relief system 100 is configured so that no component failures would cause one of thepressure relief valves 64 a-b to fail open. Instead, certain component failures cause one of thepressure relief valves 64 a-b to fail closed. Examples of component failures that can cause onepressure relief valve 64 a-b to fail closed (after opening) include: (a) failures of certain electrical fuses; (b) failures of one of the directional control valves 192 a-b (DCV1 or DCV2); or (c) failure of one of the pilot operated check valves 198 a-b. An example of component failures that can cause bothpressure relief valves 64 a-b to fail closed (after opening) includes a total loss of power (blackout). - Other component failures may occur that require operations to be stopped. For example, certain component failures may potentially cause one or both the
pressure relief valves 64 a-b to fail in place or fail open, at which point operations would be stopped. These component failures could include failure of the hydraulically-operated control valves 194 a-d, 196 a-d (DCV1A to DCV1D or DCV2A to DCV2D), failure of analog inputs, failures of accumulator bleed valves, and the like. - As discussed above, the
pressure relief system 100 of the present disclosure can be used for thebuffer manifold 60 in a managedpressure drilling system 10. In particular, the equipment protection provided by thepressure relief system 100 is applied with thepressure relief valves 64 a-b at thebuffer manifold 60 to protect theriser 20, thechoke manifold 70, the formation, etc. Separate consideration can be given to overpressure protection of surface equipment for scenarios where the source of overpressure is from thestandpipe manifold 46, the choke & killmanifolds 80, or other equipment. Therefore, the teachings of the present disclosure can be applied to rapid acting pressure protection for other interconnects of thedrilling system 10, such as interconnects of thestandpipe manifold 46, the choke and killmanifold 80, and discharge of the mud pumps 42. - Accordingly, the
pressure relief system 100 can be used elsewhere in adrilling system 10 and can be used in processes where protection from overpressure is desired. As one example,FIG. 1 illustrates where apressure relief system 100′ can used in another location of thedrilling system 10. Here, thepressure relief system 100′ is used for the overpressure protection at the discharge of the mud pumps 42. The details of thepressure relief system 100′, including the pressure relief valves, controllers, sensors, hydraulic circuits, etc., are similar to those disclosed above so that the description of these details are incorporated here. Redundant sensors measure the discharge pressure of the mud pumps 42 for overpressure protection so thepressure relief system 100′ can be opened to relieve overpressure when needed. As another example, the disclosedpressure relief system 100′ can be used for overpressure protection in thestandpipe manifold 46. - The disclosed pressure relief system can be used in other drilling configurations and systems. For example, the drilling system can include a flowline from the wellbore. The pressure relieve system can use a pressure relief valve and a choke on the flowline from the wellbore. The flow passes through the pressure relief valve and passes to the choke before passing on to further downstream equipment. As disclosed herein, the pressure relief system in this arrangement can relieve overpressure so equipment can be protected, while still being able to be dynamically adjusted for the current needs of an operation.
- The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the inventive concepts conceived of by the Applicants. It will be appreciated with the benefit of the present disclosure that features described above in accordance with any embodiment or aspect of the disclosed subject matter can be utilized, either alone or in combination, with any other described feature, in any other embodiment or aspect of the disclosed subject matter.
- In exchange for disclosing the inventive concepts contained herein, the Applicants desire all patent rights afforded by the appended claims. Therefore, it is intended that the appended claims include all modifications and alterations to the full extent that they come within the scope of the following claims or the equivalents thereof.
Claims (20)
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US16/222,462 US20200190939A1 (en) | 2018-12-17 | 2018-12-17 | Fault-Tolerant Pressure Relief System for Drilling |
CA3031116A CA3031116A1 (en) | 2018-12-17 | 2019-01-23 | Fault-tolerant pressure relief system for drilling |
BR102019002030-0A BR102019002030A2 (en) | 2018-12-17 | 2019-01-31 | fault tolerant pressure relief system for drilling |
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US16/222,462 US20200190939A1 (en) | 2018-12-17 | 2018-12-17 | Fault-Tolerant Pressure Relief System for Drilling |
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US20200190939A1 true US20200190939A1 (en) | 2020-06-18 |
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US16/222,462 Abandoned US20200190939A1 (en) | 2018-12-17 | 2018-12-17 | Fault-Tolerant Pressure Relief System for Drilling |
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US (1) | US20200190939A1 (en) |
BR (1) | BR102019002030A2 (en) |
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CN112628231A (en) * | 2021-01-29 | 2021-04-09 | 中铁工程装备集团有限公司 | Automatic drilling control valve group, control system and control method thereof |
US20220282586A1 (en) * | 2021-03-05 | 2022-09-08 | Weatherford Technology Holdings, Llc | Flow measurement apparatus and associated systems and methods |
US20220298874A1 (en) * | 2021-03-16 | 2022-09-22 | Nabors Drilling Technologies Usa, Inc. | Side saddle rig design with integrated mpd |
WO2023027944A1 (en) * | 2021-08-23 | 2023-03-02 | Schlumberger Technology Corporation | Automatically switching between managed pressure drilling and well control operations |
US11661805B2 (en) | 2021-08-02 | 2023-05-30 | Weatherford Technology Holdings, Llc | Real time flow rate and rheology measurement |
US20230193742A1 (en) * | 2021-04-01 | 2023-06-22 | Opla Energy Ltd. | Internet of things in managed pressure drilling operations |
US11873685B2 (en) | 2020-09-01 | 2024-01-16 | Nabors Drilling Technologies Usa, Inc. | Side saddle traversable drilling rig |
-
2018
- 2018-12-17 US US16/222,462 patent/US20200190939A1/en not_active Abandoned
-
2019
- 2019-01-23 CA CA3031116A patent/CA3031116A1/en not_active Abandoned
- 2019-01-31 BR BR102019002030-0A patent/BR102019002030A2/en not_active IP Right Cessation
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
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US11873685B2 (en) | 2020-09-01 | 2024-01-16 | Nabors Drilling Technologies Usa, Inc. | Side saddle traversable drilling rig |
CN112628231A (en) * | 2021-01-29 | 2021-04-09 | 中铁工程装备集团有限公司 | Automatic drilling control valve group, control system and control method thereof |
US20220282586A1 (en) * | 2021-03-05 | 2022-09-08 | Weatherford Technology Holdings, Llc | Flow measurement apparatus and associated systems and methods |
US11702896B2 (en) * | 2021-03-05 | 2023-07-18 | Weatherford Technology Holdings, Llc | Flow measurement apparatus and associated systems and methods |
US20220298874A1 (en) * | 2021-03-16 | 2022-09-22 | Nabors Drilling Technologies Usa, Inc. | Side saddle rig design with integrated mpd |
US20230193742A1 (en) * | 2021-04-01 | 2023-06-22 | Opla Energy Ltd. | Internet of things in managed pressure drilling operations |
US11885213B2 (en) * | 2021-04-01 | 2024-01-30 | Opla Energy Ltd. | Internet of things in managed pressure drilling operations |
US11661805B2 (en) | 2021-08-02 | 2023-05-30 | Weatherford Technology Holdings, Llc | Real time flow rate and rheology measurement |
WO2023027944A1 (en) * | 2021-08-23 | 2023-03-02 | Schlumberger Technology Corporation | Automatically switching between managed pressure drilling and well control operations |
GB2623733A (en) * | 2021-08-23 | 2024-04-24 | Schlumberger Technology Bv | Automatically switching between managed pressure drilling and well control operations |
Also Published As
Publication number | Publication date |
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CA3031116A1 (en) | 2020-06-17 |
BR102019002030A2 (en) | 2020-07-07 |
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