Abstract: A sealing method and sealing arrangement is described. The sealing arrangement comprises a body and first and second sealing elements mounted thereon. The sealing elements are each movable between a retracted configuration and an extended configuration and are configured to move from the retracted configuration to the extended configuration in response to an axial compression. The second sealing element is however maintained in its retracted configuration until the first sealing element has moved from its retracted configuration to its extended configuration. The sequential extension of the sealing elements can deform to assume the extended configuration under compression and the progression and the form of the deformation can be arranged to improve the quality of the seal achieved. An extended sealing element in engagement with the bore wall may also serve as an anchor or retainer and facilitate application of a compression force to an intermediate sealing element.

Abstract: A plug apparatus comprises a wedge, a sealing ring, and a slip. The wedge comprises an axial wedge bore. A seat is defined in the wedge bore. The seat is adapted to receive a ball. The wedge has a tapered outer surface which decreases in diameter from the upper to the lower extent of the tapered outer surface. The sealing ring is received around the tapered outer surface of the wedge. The sealing ring has an axial ring bore and is radially expandable. The slip comprises an axial slip bore having a tapered inner surface. The tapered inner surface decreases in diameter from the upper to the lower extent of the tapered inner surface. The inner surface is adapted to receive the wedge. The wedge is adapted for displacement from an unset position generally above the slip to a set position wherein the wedge is received in the slip bore.

Abstract: A method and apparatus for sealing and filling at least a portion of a well is disclosed. This may form a part of a well abandoning operation. In particular, according to the present disclosure, a tube containing well filler material is connected to a bridge plug by a tube-plug connector wherein the bridge plug can be positioned by moving the tube and then anchored. Once the bridge plug is anchored, the tube is disconnected and the well filler may be discharged into the well above the anchored bridge plug. In this way, the bridge plug anchoring and the filling of at least a portion of the well can be performed in a single run.

Abstract: A flow system for use at a hydraulic fracturing well site, including a tree attached to a wellhead, an inlet head in fluid communication with at least one hydraulic fracturing pump at the well site, and an adjustable fluid conduit providing fluid communication between the inlet head and the tree. The flow system further includes a valve in the fluid conduit and having an open position and a closed position, the valve permitting fluid flow through the fluid conduit when in the open position, and preventing fluid flow through the fluid conduit when in the closed position, at least a portion of the fluid conduit positioned between the valve and the tree.

Abstract: A valve comprises a housing including a first chamber, a second chamber, and a neutral chamber. In addition, the valve comprises a stem disposed within the housing. Further, the valve comprises a first valve member at least partially disposed in the first chamber and connected to the stem and a second valve member at least partially disposed in the second chamber and connected to the stem. The first valve member has a closed position seated in a first annular valve seat and an open position spaced apart from the first valve seat. The second valve member has a closed position seated in a second annular valve seat and an open position spaced apart from the second valve seat. Moreover, the valve comprises a biasing member configured to bias the second valve member to the closed position and the first valve member to the open position.

Abstract: A downhole valve includes a stationary sleeve for connection to a production string or a downhole tool, which includes one or more slots in the body of the stationary sleeve open to the interior of the stationary sleeve. A microcontroller is connected to a conducting cable and configured to control a flow of electrical power independently to a coil connected to an electrical power source at the surface. An inner sleeve is configured to fit within the stationary sleeve. The inner sleeve has an internal or external magnetized portion and one or more ports open to the interior of the inner sleeve. The sleeve is moveable within the stationary sleeve under power provided by a magnetic field generated by electrical current passing through the coil to align the ports with the slots to open the valve or to remove alignment of the ports with the slots to close the valve.

Abstract: A wellbore servicing tool comprising a housing comprising one or more ports and generally defining a flow passage, an actuator disposed within the housing, a magnetic signature system (MSS) comprising a magnetic sensor in signal communication with an electronic circuit disposed within the housing and coupled to the actuator, and a sleeve slidably positioned within the housing and transitional from a first position to a second position, wherein, the sleeve is allowed to transition from the first position to the second position upon actuation of the actuator, and wherein the actuator is actuated upon recognition of a predetermined quantity of predetermined magnetic pulse signatures via the MSS.

Abstract: Ball valve assembly (100) including a truncated sphere (140) anchored in a two cylindrical retaining members (48, 50) of the ball valve assembly (100), the truncated sphere (140) having a spherical cap sealing face (142). The ball valve assembly (100) also includes a pair of concentrically oriented, tubular sealing pistons (120, 130), each piston (120, 130) exclusively actuable, one relative to the other, into fluid pressured sealing engagement with the spherical cap sealing face (142) in dependence upon whether an experienced fluid pressure at the ball valve assembly (100) is from a top side (102) or an opposite bottom side (104) of the ball valve assembly (100).

Abstract: A downhole valve (26) comprises a valve body (32) defining a sealing surface (34) and a flow port (36), a valve member (50) mounted within the valve body and including a sealing arrangement (60), and a protection sleeve (72) mounted within the valve body (32). The valve member is moveable within the valve body from a closed position in which the flow port is closed and the sealing arrangement sealingly engages the sealing surface of the valve body, towards an open position in which the flow port is opened and the sealing arrangement is disengaged from the sealing surface and received within the protection sleeve.

Abstract: Drilling flow control tools may include a tool body having a central bore and bypass ports that allow flow of fluid to an outer surface of the tool body. The drilling flow control tool may also include a control sleeve within the central to bore. The control sleeve may restrict fluid flow through the bypass ports when in an inactive state and allow the fluid flow through the bypass ports when in an active state. The drilling flow control tool may further include a release subassembly movably coupled to the tool body. Packer cups coupled to the tool body can act as packoff devices that control passage of fluid along the outer diameter of the tool body. Using the packer cups and control sleeve, fluid flow may be circulated within an inner annulus of a wellbore, an outer annulus of a wellbore, or both.

Abstract: An apparatus for monitoring the condition of a seal, such as a seal in a blowout preventer or in another oilfield device, is provided. In one embodiment, the apparatus includes a blowout preventer including a seal and a blowout preventer seal-monitoring system that includes a sensor positioned within a body of the seal and a data analyzer. The data analyzer has a processor and is configured to monitor a condition of the seal through analysis of data received by the data analyzer from the sensor positioned within the body of the seal. Additional systems, devices, and methods are also disclosed.

Abstract: An overtensioning fastening tool to maintain control of oil and gas equipment and prevent migration upon failure. The overtensioning fastening tool is comprised of one or more flapper components, housed in a primary enclosure, a hydraulic deployment system and/or electric deployment system, housed in a secondary enclosure, a sensor, and a manual activation component. The overtensioning fastening tool is designed to grip and hold equipment and tooling, such as cables, to prevent loss into the wellbore and to maintain the safety and integrity of the rig and surrounding rig environment.

Abstract: An assembly and method for completion of lateral wellbores is disclosed. The completion assembly includes a junction fitting with main and lateral legs, and a lateral completion string and anchoring device connected to the downhole end of the lateral leg and the uphole end of the junction fitting, respectively. A working string, positioned within the lateral leg, anchoring device, and lateral completion string, includes a setting tool that is removably connected to the anchoring device and a completion tool assembly located within the lateral completion string. The completion assembly is run by the working string into the wellbore. After setting the anchoring device, the working string conveys the completion tool assembly within the lateral completion string for gravel packing, fracturing, frac-packing, acidizing, cementing, perforating, and inflating packers, for example. After wellbore completion, the completion tool assembly is removed through the lateral leg of the junction fitting.

Abstract: A lateral junction for a multilateral wellbore having a main bore and a lateral leg which extends away from the main bore. The lateral junction includes a seal bore diverter and a hanger that is insertable into the seal bore diverter to form the junction. An engagement mechanism interlocks the hanger and seal bore diverter together at the crux of their joining.

Abstract: A flow control apparatus for a borehole comprises a basepipe, a screen, a sleeve, and at least one baffle. The basepipe has a bore for conveying fluid and defines at least one opening for communicating fluid into the bore. The screen is disposed on the basepipe and screens fluid from outside the basepipe. The sleeve is disposed on the basepipe adjacent the screen and has at least one flow passage for communicating the fluid from the screen to the at least one opening in the basepipe. A shelf of the sleeve extends downstream from the at least one flow passage and covers at least a portion of the basepipe upstream from the at least one opening. The at least one baffle is disposed on the shelf and changes a direction of the flow exiting from the at least one flow passage.

Abstract: Applying shock waves using a plasma pulse generation system or other comparable systems, including an acoustic/pressure oscillatory system, would help to enhance the complexity of the far field hydraulic fracture during fracturing shale formation. It would also help in avoiding pre-mature screen out. The critical factor to maximize the desired results is to apply the shock waves at the correct time. By combining shock wave technology with the newly developed fracturing pressure data analysis, it is possible to achieve maximum results.

Abstract: Compositions and methods for triggering an exothermic reaction of an exothermic reaction component are provided. A method includes the steps of mixing the exothermic reaction component in an aqueous solution to achieve a pre-selected solution pH, where the aqueous solution operably delays triggering of the exothermic reaction upon reaching a pre-determined temperature of a hydrocarbon-bearing formation; disposing the exothermic reaction component within the hydrocarbon-bearing formation; applying microwaves to the exothermic reaction component, where the microwaves are operable to trigger the exothermic reaction of the exothermic reaction component; and generating heat and gas in situ by the exothermic reaction to increase pressure and temperature of the hydrocarbon-bearing formation proximate the exothermic reaction component.

Abstract: A system and method of forming a horizontal well for use in environmental remediation is provided. The method includes forming a bore hole to a desired location. A fracturing tool is moved to the end of the bore hole. The fracturing tool is rotated to arrange a nozzle at a desired orientation for directing energy into the soil. The energy directed into the soil generates fractures that improve the efficiency of environmental remediation of the soil.

Abstract: Apparatus and methods for spatially orienting a subterranean pressure pulse to a hydrocarbon-bearing formation are provided. The apparatus includes an injection body with a fixed shape, where the injection body is operable to hold an exothermic reaction component prior to triggering an exothermic reaction of the exothermic reaction component, and where the injection body maintains the fixed shape during and after triggering of the exothermic reaction component. The injection body includes a chemical injection port, where the chemical injection port is operable to feed components of the exothermic reaction component to the injection body. The injection body includes a reinforced plug, where the reinforced plug is operable to direct a pressure pulse generated by the exothermic reaction component within the injection body to a perforation to generate a spatially-oriented fracture, where spatial orientation of the spatially-oriented fracture is pre-determined.

Abstract: A method can include manufacturing particulate material during an operation at a well, injecting the particulate material into the well during the manufacturing, and changing a dimension of the particulate material during the injecting. Another method can include manufacturing particulate material during an operation at a well, injecting the particulate material and a proppant into the well during the manufacturing, and then the particulate material degrading in the well. Another method can include manufacturing particulate material during an operation at a well, fixing a shape of the particulate material by cooling the particulate material, and then injecting the particulate material into the well. A particulate material production and injection system for use with a well can include an extruder, and a pump connected between the extruder and the well. The pump pumps the particulate material into the well.

Abstract: A method is taught for producing hydrocarbons from a reservoir by drilling two or more wells located proximal a bottom of said reservoir. The method comprises initiating one or more high-mobility zones connecting said wells along the bottom of the reservoir and producing the reservoir from the bottom of said reservoir upwards.

Abstract: There is provided a system for producing formation fluids. The system includes an apparatus for effecting production, from a subterranean formation, of a produced formation fluid including a liquid component and a gas component. The system may also include an apparatus configured for energizing produced formation fluid using a Venturi effect to produce an energized formation fluid. The system may also be configured to control flow of gaseous material being re-injected into the wellbore.

Abstract: A system includes an optical fiber and an interrogator to provide source light to the optical fiber. The system also includes a receiver coupled to the optical fiber. The receiver includes at least one fiber optic coupler that receives backscattered light and that produces one or more optical interferometry signals from the backscattered light. The receiver also includes photo-detectors that produce an electrical signal for each of the one or more optical interferometry signals. The system also includes at least one digitizer that digitizes each electrical signal. The system also includes at least one processing unit that processes each digitized electrical signal to obtain a distributed sensing signal and related energy spectrum information.

Abstract: An apparatus for monitoring the condition of a seal, such as a seal in a blowout preventer or in another oilfield device, is provided. In one embodiment, the apparatus includes a blowout preventer including a seal and a blowout preventer seal-monitoring system that includes a sensor positioned within a body of the seal and a data analyzer. The data analyzer has a processor and is configured to monitor a condition of the seal through analysis of data received by the data analyzer from the sensor positioned within the body of the seal. Additional systems, devices, and methods are also disclosed.

Abstract: A dimensional characteristic of a borehole is determined from a rotary drilling system having a housing and an anti-rotation device with one or more drag members that engage a borehole wall. A sensor detects a biasing force on the drag members and transmits a signal representative of the force on the drag member to a control unit. The control unit determines a dimensional characteristic of the borehole based on the force on the drag member of the anti-rotation device.

Abstract: A system for directly sensing a position of a movable part of a hydrocarbon drilling and production includes a housing having a body with an inner cavity and a body wall with a wall thickness defined between an inner surface of the inner cavity and an outer surface of the body. The inner cavity has a fluid flow path for hydrocarbon development fluids. A moveable member is located within the inner cavity. A sensor assembly is located within one of the body wall and the moveable member, the sensor assembly being positioned within a port. An indicator feature is on the other of the body wall and the moveable member, the indicator feature sensable by the sensor assembly when the moveable member is in a set position.

Abstract: A clearing or unjamming process utilizes bidirectional agitation and non-deterministic behavior to clear debris that is jamming a downhole rotary tool. In accordance to at least one embodiment the clearing or unjamming process uses irregular oscillation of the jamming debris which may be produced by varying pause times in a bidirectional movement of the rotor. In some embodiments the rate of acceleration and deceleration of the rotor is maintained constant during the unjamming process.

Abstract: A cutter disc for a tunnel boring machine includes a middle disc portion defining a radially outer surface or edge for engaging a surface, a left toothed portion defining a first set of teeth set back from the outer edge, and a right toothed portion defining a second set of teeth set back from the outer edge. In an embodiment, a central bore through the cutter disc is configured to attach the cutter disc to a hub for rotatably mounting the cutter disc on a shaft. In an embodiment, the hub is formed integrally with the cutter disc. The left and right toothed portions provide structural support to the middle portion and facilitate rotation of the cutter disc when boring in soft or mixed conditions, but do not interfere with boring in hard rock conditions.

Abstract: A longitudinally yieldable support for underground roof support includes a first support section with a first elongate outer shell partially filled with a solid compressible filler material and a second support section at least partially filled with a second solid compressible filler material. The second support section is at least partially disposed within the first elongate outer shell and is telescopically extendable relative thereto. A bladder is interposed between the first and second support sections that is fillable in situ to cause extension of the second support section relative to the first support section when filled under pressure with a filler material.

Abstract: An air motor (10) that has opposing chambers (16, 17) to which compressed air is alternatively delivered to drive the motor (10). The motor (10) has a primary valve (52) that governs deli very of the compressed air to the chambers (16, 17) so at least part of the compressed air is transferred to the other chamber to aid in driving the pistons (18).

Abstract: A clean energy system, a renewable energy system or a zero emission energy system (ZEES) to utilize CO2 waste. The energy system may include a fuel processor, an energy catalytic reactor, and a power generator. The fuel processor may catalytically convert the CH4 component in the natural gas, biogas or syngas into a reformate including H2, CO, CO2 and H2O species. The energy reactor may convert the reformate in gas form into a liquid fuel. The power generator may generate power using an output of the fuel processor and/or an output of the energy reactor.

Abstract: Disclosed herein is an indexing system for a rotor assembly where in one example the indexing system regulates the rotational location of drive rotors. In one example the rotors are configured to rotate about a shaft.

Abstract: Provided are a vane unit and a steam turbine. A vane unit in which an outer ring and an inner ring are connected by a plurality of vanes arranged at predetermined intervals in a circumferential direction is provided with: a steam outer ring inlet portion provided in a first heating chamber of the outer ring; a steam outer ring outlet portion provided in the first heating chamber of the outer ring so as to be separated from the steam outer ring inlet portion in the circumferential direction; and a first steam passage that makes the steam outer ring inlet portion and the steam outer ring outlet portion communicate with each other in the first heating chamber of the outer ring. Thus, steam is efficiently used, and erosion due to wet steam is suppressed and a decrease in thermal efficiency is suppressed.

Abstract: An edge guard apparatus for an airfoil includes: a body having a nose with spaced-apart first and second wings extending therefrom, the body defining a cavity between the first and second wings; and an energy absorbing structure disposed in the cavity.

Abstract: An airfoil for a turbine engine includes an airfoil that has pressure and suction sides that extend in a radial direction from a 0% span position at an inner flow path location to a 100% span position at an airfoil tip. The airfoil has a relationship between a leading edge dihedral and a span position. The leading edge dihedral is negative from the 0% span position to the 100% span position. A positive dihedral corresponds to suction side-leaning, and a negative dihedral corresponds to pressure side-leaning. The airfoil has a relationship between a trailing edge dihedral and a span position. The trailing edge dihedral is positive from the 0% span position to the 100% span position. A positive dihedral corresponds to suction side-leaning and a negative dihedral corresponds to pressure side-leaning.

Abstract: A system includes a turbine airfoil configured to be disposed in a turbine. The airfoil includes a suction side, a pressure side, and a first protrusion disposed on the suction side, a second protrusion disposed on the pressure side, or both. The suction side extends between a leading edge of the turbine airfoil and a trailing edge of the turbine airfoil in an axial direction and transverse to a longitudinal axis of the turbine airfoil, and extends a height of the turbine airfoil in a radial direction along the longitudinal axis. The pressure side is disposed opposite the suction side and extends between the leading edge of the turbine airfoil and the trailing edge of the turbine airfoil in the axial direction, and extends the height of the airfoil in the radial direction. The first protrusion is disposed on the suction side of the turbine airfoil and protrudes relative to the other portion of the suction side in a first direction transverse to both the radial and axial directions.

Abstract: A shrouded turbine blade including a blade body having an operationally upstream face, an operationally downstream face, a root end and a tip end and a shroud segment provided at the tip end, the blade having an inlet in the root end and a cooling passage passing from the inlet to the tip end, the shroud segment comprising an arcuate platform and a seal fin arranged towards an operationally upstream end of the shroud platform and extending away from the blade body and circumferentially across the shroud platform, a fin cooling passage in fluid communication with the tip end of the blade cooling passage, the fin cooling passage having at least one outlet on an operationally downstream facing side of the fin, and a flow discourager arranged towards an operationally downstream end of the shroud platform.

Abstract: An article and a component are provided. The article includes a base portion arranged and disposed to be positioned within a component, and an arrangement of apertures formed in the base portion, each of the apertures extending through the base portion. The arrangement of apertures is arranged and disposed to provide shadowless cooling of an inner surface of the component. The component includes a body portion having an inner surface and an outer surface, the inner surface defining an inner region, and an article positioned within the inner region, the article comprising a base portion and an arrangement of apertures formed in the base portion, each of the apertures extending through the base portion. The arrangement of apertures is arranged and disposed to provide shadowless cooling of the inner surface of the body portion. Also provided is a method of cooling a component including an article positioned therein.

Abstract: An airfoil of a gas turbine engine is provided. The airfoil includes an airfoil body having at least one internal flow passage, the body having a first surface and a second surface, the first surface defining a wall of the at least one internal flow passage and a bleed port fluidly connecting the at least one internal flow passage to the second surface. The bleed port includes a bleed orifice extending from the second surface toward the internal flow passage and a bleed port cavity extending from the first surface toward the second surface, the bleed port cavity and the bleed orifice fluidly connected. The bleed port cavity is defined by a bleed port cavity wall and a base wall surrounding the bleed orifice. The bleed port cavity wall extends from the first surface to the base wall.

Abstract: A method of forming a passage in a turbine component that includes using an additive manufacturing process to form a first support structure on a first surface of the turbine component; and forming a passage through the first support structure and the turbine component.

Abstract: A component is provided and comprises at least one wall comprising a first and a second surface. At least one film cooling hole extends through the wall between the first and second surfaces and has an outlet region at the second surface. The film cooling hole includes a first expansion section being a side diffusion portion and a second expansion section being a layback diffusion portion, wherein the side diffusion portion is upstream and spaced from the layback diffusion portion.

Abstract: A turbine blade assembly for a gas turbine engine is provided. The turbine rotor blade assembly includes a turbine rotor blade and an attachment pin, and the turbine rotor blade and attachment pin have features for providing a surface interface between the blade and pin. In particular, the attachment pin has a triangular cross-sectional shape, and the blade defines a pin hole for receipt of the attachment pin. An attachment pin for attaching a turbine rotor blade to a turbine rotor disk of a gas turbine engine also is provided. The attachment pin includes a body defining at least one planar surface, and the planar surface provides a surface contact interface between the attachment pin and the turbine rotor blade.

Abstract: A gas turbine has a compressor, a central housing, at least one combustion chamber, an expansion turbine, and a heat exchanger. Each combustion chamber is fluidically connected to the expansion turbine via an inner housing which is guided through the interior of the central housing. The compressor is fluidically separated from the interior of the central housing by an annular collection chamber connected to an outlet of the compressor and which has a number of discharge lines which are connected to the cold side of the heat exchanger during operation. Each combustion chamber is designed as a silo combustion chamber, and each silo combustion chamber has an inner wall, which delimits a combustion chamber, and an outer wall, and the outer wall surrounds the inner wall, thereby forming a cavity. The inner wall transitions into the inner housing, and the cavity transitions into the interior of the central housing.

Abstract: A transition duct system (100) for routing a gas flow from a combustor (102) to the first stage (104) of a turbine section (106) in a combustion turbine engine (108), wherein the transition duct system (100) includes one or more converging flow joint inserts (120) forming a trailing edge (122) at an intersection (124) between adjacent transition ducts (126, 128) is disclosed. The transition duct system (100) may include a transition duct (126, 128) having an internal passage (130) extending between an inlet (132, 184) to an outlet (134, 186) and may expel gases into the first stage turbine (104) with a tangential component. The converging flow joint insert (120) may be contained within a converging flow joint insert receiver (136) and disconnected from the transition duct bodies (126, 128) by which the converging flow joint insert (120) is positioned. Being disconnected eliminates stress formation within the converging flow joint insert (120), thereby enhancing the life of the insert.

Abstract: A gas turbine includes a turbine and an axial-radial diffuser. The turbine includes a last stage airfoil section, which includes a first inner annular wall, a plurality of airfoils, a tip shroud including a first outer annular wall, and a stationary shroud including a second outer annular wall. The first inner annular wall is angled at a first inner angle average, the first outer annular wall is angled at a first outer angle average, and the second outer annular wall is angled at a second outer angle average. The axial-radial diffuser includes a third inner annular wall and a third outer annular wall, wherein the first diffuser section is disposed immediately downstream from the last stage airfoil section, wherein the third inner annular wall is angled at a third inner angle average, and the third outer annular wall is angled at a third outer angle average.

Abstract: A stator vane removal system includes a reaction platform configured to couple between opposing sides of a slot defined in an inner surface of a casing of a rotary machine. At least one stator vane is retained in the slot. The reaction platform includes at least one wedge surface. The system also includes an actuator configured to couple to the reaction platform. The at least one wedge surface facilitates inducing a coupling force exerted by the reaction platform to the opposing sides of the slot when the actuator applies a pushing force to the at least one stator vane in the slot.

Abstract: A cooling system (10) for a turbine airfoil (12) of a gas turbine engine is disclosed, whereby the cooling system (10) includes spanwise extending midflow blockers (14) positioned within one or more cooling channels (16) to maintain an internal through flow channel Mach number. One or more cooling channels (16) may have a larger cross-sectional area proximate to an outer end (18) of the airfoil (12) than at an inner end. One or more cooling channels (16) may include midflow blockers (14) extending into the cooling channel (16). In at least one embodiment, the midflow blocker (14) may extend radially inward from the outer end (18) of the airfoil (12). The midflow blocker (14) may limit movement of cooling fluid from the pressure side (36) to the suction side (38) or vice versa. The midflow blocker (14) may increase in size moving radially outward as the cross-sectional area of the cooling channel (16) increases as well.

Abstract: A method of forming a structure in a turbine component having a seal slot, the slot including walls defining an opening therebetween, the method includes the step of using an additive manufacturing process to form a neck structure on a wall so as to reduce a size of the opening.

Abstract: A shroud hanger assembly or shroud assembly is provided for a gas turbine engine wherein a hanger includes a radially depending and axially extending arm. The arm or retainer engages a pocket formed in a shroud so as to retain the shroud in a desired position relative to the hanger. An aft retaining structure is provided on the hanger and provides a seat for a seal structure which biases the retainer so that the arm of the hanger maintains engagement in the shroud pocket. A baffle may be utilized at the hanger to cool at least some portion of the shroud.

Abstract: In a gas turbine engine stage, a labyrinth seal has a layer of abradable material arranged on a static part and radially delimited by a cylindrical surface, which is continuous and has a constant diameter in an initial assembly configuration; the seal has at least three tabs, which are arranged on the rotating part, radially facing the abradable material, and are constituted by two side tabs and an intermediate tab having a smaller radial height; this height still allows the abradable material to be engraved, due to the effect of thermal expansion and of the relative rotation during operation; the tabs are positioned axially in such a way that, in the running operational configuration, the layer of abradable material has two seats, which have been fretted by the tips of the two side tabs during operation, and are axially separated by a step, while the intermediate tab is arranged at said step.