Abstract: A method for the extinction or oil well-killing or killing of an underwater well for the extraction of hydrocarbons under uncontrolled fluid discharge conditions, also called blowout, by assembling, in correspondence with the lower end portion of a string of pipes for the extinction or killing string, a constraint group for rigid connection between a plurality of remote-operated underwater vehicles and the killing string; detecting the position of a flow of fluids and positioning the killing string substantially in correspondence with said flow; lowering a plurality of remote-operated vehicles close to the lower end portion of the killing string; connecting the remote-operated vehicles to the constraint group; detecting in real time the relative position of the flow of fluids with respect to the vehicles and calculating the position of the outlet hole of the flow; on the basis of the calculated position of the outlet hole, coordinately piloting the vehicles so as to bring the lower end of the string in corres

Abstract: An arrangement and method for more accurately detecting well bore fluid kicks and/or losses by coupling a fluid flow measurement device to a substantially vertical tubular, such as a bell nipple or marine riser, to more accurately determine the flow rate of fluid flowing out of the well bore. Well bore fluid kicks and/or fluid losses are preferably detected by comparing the determined flow rate of fluid flowing out of the well bore and the flow rate of fluid injected into the well bore for any difference indicative of a well bore fluid kick or loss event.

Abstract: Casing segments and an expansion cone are positioned and cemented within a new section of a wellbore with a lower casing segment in an overlapping relationship with an upper casing segment. The lower casing segment is radially expanded such that an upper end of the lower casing segment comes into contact with the interior wall of the upper casing segment at the overlap region. The upper casing segment has an inward facing profile at the overlap region that includes a set of wickers that are driven into the lower casing exterior when it is expanded. This forms a metal-to-metal seal between the upper and lower casing segments at the overlap region.

Abstract: A system for pressure testing the joints and walls of a production pipe includes a fluid system component that can be disposed at a first end of the production pipe so as to seal off the first end of the production pipe. The fluid system component prevents the flow of fluid out of the first end of the production pipe when the pressure within the production pipe is below a predetermined level. The fluid system component includes a sacrificial element that is adapted for preferential failure when the pressure within the production pipe exceeds the predetermined level. Upon failure of the sacrificial element, fluid is able to flow out of the production pipe through the fluid system component. The system may also include a test plug that prevents the activation of a drain component in the production pipe during the pressure testing of the production pipe.

Abstract: A method for determining a location of a lost circulation zone in a wellbore having a first wellbore fluid therein that includes allowing loss of the first wellbore fluid to the lost circulation zone to stabilize; adding a volume of a second wellbore fluid having a density less than the first wellbore fluid to the wellbore on top of the first wellbore fluid to a predetermined wellbore depth; determining an average density of the combined first wellbore fluid and second wellbore fluid; mixing the first wellbore fluid and the second wellbore fluid together; pumping a volume of a third wellbore fluid having a density greater the average density of the combined first and second wellbore fluid into the wellbore bottom until fluid loss occurs; and determining the location of the lost circulation zone is disclosed.

Abstract: Disclosed herein is a safety valve with a chemical injection configuration. The device includes a hydraulic fluid pressure operated piston at the housing. The device further includes a flow tube in operable communication with the piston and a chemical injection configuration disposed within the housing. Further disclosed herein is a method of maintaining the operation of a safety valve by injecting chemical fluid through a configuration within the safety valve. Still further disclosed herein is check valve. The check valve includes a seal, a dart having a closed head and sealable against the seal, one or more flutes on the dart, and a spring applying a biasing force to the dart to a sealing position, that force being overcomeable by a fluid pressure acting in a direction opposing the spring force.

Abstract: A hydraulic overshot apparatus designed to slide over plain end tubing and set by applying hydraulic fluid, under pressure, via a hydraulic setting port, into a center chamber which allows pressure to direct to two different piston areas. The setting piston compresses packer elements and tubing slips against the outer diameter (O.D.) of the tubing. The test piston compresses tubing test elements against the inner diameter (I.D.) of the tubing. The setting pressure is ported through the upper setting and test portion to allow pressure to move from the center chamber to the lower outer portion. The lower outer portion includes a body lock ring and a setting piston for setting the packer elements. Setting pressure moves the setting piston down through the body lock ring. As the setting piston moves down, it ratchets down through the body lock ring.

Abstract: A valve device and associated methods of selectively communicating between an interior and an exterior of a tubular string. A valve device includes an openable and closable flowpath for selectively permitting and preventing flow between an interior and exterior of the valve device, and a lock assembly which prevents the flowpath from being opened greater than a predetermined number of times. A method of testing at least one annular seal in an annulus formed between a tubular string and a wellbore wall includes the steps of: sealingly engaging the annular seal to thereby prevent flow through the annulus across the annular seal; and applying a pressure differential across the annular seal to thereby test the annular seal, the pressure differential being applied via a valve device interconnected in the tubular string.

Abstract: A method for the detection of a carbon dioxide leak from a plugged well extending from a surface of the earth to penetrate a subterranean formation which contains carbon dioxide by logging a collection chamber positioned in the plugged well.

Abstract: A method of producing a well utilizes a submersible pump run on a line, such as braided wire rope, that includes power conductors. The operator sets a packer in the casing, the packer having a check valve and a tieback receptacle. The operator pressure tests the integrity of the casing above the packer, and if it passes, then runs the pump assembly on the line. The pump assembly has a shroud with a downward extending extension that seals to the passage of the packer. If the pressure test of the casing fails, the operator runs a liner into the well and engages the tieback receptacle. A smaller diameter pump is then lowered on a line into the liner and into engagement with the packer.

Abstract: Downhole tools and methods for producing hydrocarbons from a wellbore. A downhole tool can include a body having a bore formed therethrough and at least one end adapted to threadably engage one or more tubulars. A sliding sleeve, adapted to move between a first position and a second position within the body, can be at least partially disposed within the body. A valve assembly including a valve member having an arcuate cross section wherein the valve member is adapted to pivot between an open and closed position within the body can be disposed within the body. A valve seat, having an arcuate cross-section adapted to provide a fluid tight seal with the valve member assembly can be disposed within the body.

Abstract: The present invention relates to an apparatus (1) for leakage testing and/or pressure testing a portion of a pipe (7), the apparatus (1) including at least two spaced-apart packer elements (3, 5) which are arranged to define a volume (10) of fluid in an annulus between said at least two packer elements (3, 5) and the internal jacket surface of the pipe (7), and the apparatus (1) being provided with a means for providing a differential pressure between the fluid volume (10) and a fluid located immediately upstream and downstream of the apparatus (1), and with a means for sensing the pressure of the fluid volume (10). The invention also relates to a method of using the apparatus.

Abstract: A valve device and associated methods of selectively communicating between an interior and an exterior of a tubular string. A valve device includes an openable and closable flowpath for selectively permitting and preventing flow between an interior and exterior of the valve device, and a lock assembly which prevents the flowpath from being opened greater than a predetermined number of times.

Abstract: A tool is employed with a subsea wellhead assembly for preventing the collapse of a wear bushing located in a drill-through tubular member due to external test forces being applied to it. The tool has a connector that connects to the drill-through tubular member. A stem extends downward from the connector and has a reacting member at its lower end. The reacting member engages an inner diameter of the wear bushing to resist inwardly directed forces due to fluid pressure on the exterior of the wear bushing. The tool can be incorporated with a running tool or with a blowout preventer isolation test tool.

Abstract: A fixed-point packoff element for a full-bore pressure isolation tool supports a primary seal and a test seal to permit the primary seal to be tested by injecting test fluid through a side port of a tubing head spool before the pressure isolation tool is rigged up for a well stimulation procedure.

Abstract: A method of detecting leakage from a drilling tool comprising putting at least one transmitter (110) in lubricant within the tool (26) and scanning for the transmitter (120) with a receiver (120) at the surface or in a downhole measurement and communications system (25). If the transmitter (110) is detected, then one can deduce that the lubricant has leaked from the tool (26). The method therefore provides an early warning of potential or impending tool failure.

Abstract: An arrangement is described of a plug with a sealing system for pressure testing of bore holes and the like in a formation or the like, comprising a pipe in which the plug is fitted in a plug-carrying chamber, and the plug closes the passage through the pipe in cooperation with sealing bodies, as the plug is arranged (rests) in a seat in the chamber. The arrangement is characterised in that the sealing bodies (23,25) are arranged in connection with the inner wall of the pipe (10) above (upstream) and/or below (downstream) of the chamber (30), and are arranged to form a seal against the respective cylindrical extensions (44,46) of the plug body (45) above and/or below the chamber.

Abstract: A test plug tool for use in testing a pressure integrity of a pressure control stack mounted to a wellhead, including a joint between a casing and a casing support in the wellhead. The test plug tool includes a test plug of an appropriate diameter used to pressure test the pressure control stack as well as a joint between any one of a surface casing and the wellhead, an intermediate casing and an intermediate casing mandrel, and a production casing and a production casing mandrel. The pressure integrity of the wellhead is ensured at each stage of well drilling and well completion, and safety is improved. Optionally, a backpressure valve permits pressurized fluid that leaks below the test plug tool to flow upwardly through a central bore in a landing tool that is secured to the test plug tool to permit detection of the leak.

Abstract: Downhole tools and methods for producing hydrocarbons from a wellbore. A downhole tool can include a body having a bore formed therethrough and at least one end adapted to threadably engage one or more tubulars. A sliding sleeve, adapted to move between a first position and a second position within the body, can be at least partially disposed within the body. A valve assembly including a valve member having an arcuate cross section wherein the valve member is adapted to pivot between an open and closed position within the body can be disposed within the body. A valve seat, having an arcuate cross-section adapted to provide a fluid tight seal with the valve member assembly can be disposed within the body.

Abstract: This disclosure relates in general to a method and system for monitoring a conduit, a wellbore or a reservoir associated with hydrocarbon production or transportation and/or carbon dioxide sequestration. More specifically, but not by way of limitation, embodiments of the present invention provide for using an optical fiber as a distributed interferometer that may be used to monitor the conduit, wellbore or reservoir.

Abstract: A technique that is usable with a well includes deploying at least one sensing device in the well and during a leak off test, communicating a signal that is indicative of a measurement that is acquired by the sensing device(s) over a wired infrastructure of a drill string. The technique includes controlling the leak off test based at least in part on the communication.

Abstract: A test plug tool for use in testing a pressure integrity of a pressure control stack mounted to a wellhead, including a joint between a casing and a casing support in the wellhead. The test plug tool includes a test plug of an appropriate diameter used to pressure test the pressure control stack as well as a joint between any one of a surface casing and the wellhead, an intermediate casing and an intermediate casing mandrel, and a production casing and a production casing mandrel. The pressure integrity of the wellhead is ensured at each stage of well drilling and well completion, and safety is improved. Optionally, a backpressure valve permits pressurized fluid that leaks below the test plug tool to flow upwardly through a central bore in a landing tool that is secured to the test plug tool to permit detection of the leak.

Abstract: The present invention includes a method and system for detecting and locating a breach of a pipe in nested multi-pipe petroleum wells through the use and measurement of pressure valves and pressure sensors. The system “locates” breaches in the sense that it determines in which pipe or pipes, if any, in a nested multi-pipe production well the breach exists. The method comprises the steps of, first, connecting at least two of the well pipes of a nested multi-pipe production well to a collection reservoir to allow fluid communication from the well into the reservoir; second, sealing the well pipes to maintain the pressure therein; third, measuring a pressure parameter within each of said at least two well pipes until said pressure parameter indicates a stabilization of pressure therein; fourth, altering the pressure within one of the well pipes; fifth, measuring a pressure parameter within the other well pipes; and sixth, stabilizing the pressure in the well pipe within which the pressure was previously altered.

Abstract: Methods and apparatus are provided for performing an expedited shoe test using an expandable casing portion as an annular fluid barrier. Such an expandable annular fluid barrier may be used in conjunction with cement if so desired but cement is not required. Further provided are methods and apparatus for successfully recovering from a failed expansion so that a shoe test can be completed without replacement of the expandable casing portion.

Abstract: An embodiment of the present invention comprises an apparatus for engaging with an outside diameter of a tubular comprises a device body having an internal surface that defines an internal diameter in a first position and allowing the tubular to pass therethrough and an actuator operable to move the internal surface of the device body from the first position to a second position, the second position defining an internal diameter less than the first position internal diameter. The internal surface of the device body is sized with a predetermined grip length for engaging with the outside diameter of the tubular. The grip length is determined by a function of the outside diameter of the tubular and the coefficient of friction between of the outside diameter of the tubular and the interior surface of the device body and the device body is operable to engage with a tubular having a predetermined range of outside diameters.

Abstract: Methods are provided in which reliance is placed on a first and second barrier respectively positioned in a well 10 to provide well control during well suspension, completion and/or workover operations. Each of the barriers is below the depth of the lowermost end of a completion string when that string is installed in the well. By not placing either barrier higher up in the well-bore, both of the barriers can remain in place during suspension and completion and workover operations, thus obviating the need to use a BOP stack to supplement well control. This results in a considerable saving in drill rig time and thus significantly reduces the cost of constructing a well.

Abstract: A method for the detection of a carbon dioxide leak from a plugged well extending from a surface of the earth to penetrate a subterranean formation which contains carbon dioxide by logging a collection chamber positioned in the plugged well.

Abstract: Certain embodiments provide a method that includes placing a heater element in an opening in a subsurface formation. The heater element is in a conduit. A pressure is reduced inside the conduit to a pressure below the vapor pressure of water at the temperature in the conduit.

Abstract: A method and apparatus is disclosed for testing a blowout preventer (BOP) by: using a drillpipe to install a test plug into one end of the throughbore of a (BOP); using a valve in the BOP to isolate the opposite end of the throughbore of the BOP, using piping to connect the output of a cementing unit to the throughbore of the BOP; using the cementing unit to increase the pressure in the throughbore of the BOP to a predetermined level; displaying the pressure in the piping as a function of time; and displaying the pressure in the piping as a function of time for the same blowout preventer system at an earlier time when leakage was deemed to be within predetermined acceptable limits. The pressure decline caused by a leak can be detected reliably and efficiently with high-resolution pressure data.

Abstract: The present invention provides methods and apparatus for obtaining downhole well pressure during wellbore operations. One method comprises providing a well intervention tool comprising a straddle sealing assembly having upper and lower annulus sealing elements and a fluid injection port positioned therebetween, the well intervention tool comprising a fluid injection bore having positioned therein a pressure measurement tool; placing the tool in straddle position about a wellbore region to be intervened, with the pressure measurement tool fluidly connected to a wellbore region below the lower annulus sealing element; and performing the wellbore intervention operation while communicating fluid from below the lower annulus sealing element to the pressure measurement tool, thus obtaining a pressure measurement below the lower annulus sealing element during the wellbore intervention operation. This abstract will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Abstract: A method for the detection of a fluid leak from a plugged well extending from a surface of the earth to penetrate a subterranean formation which contains fluid by logging a collection chamber positioned in the plugged well.

Abstract: Methods of improving the pressure containment integrity of subterranean well bores are provided. The methods include pumping a fracture sealing composition into the well bore that rapidly converts into a high friction pressure sealing composition which is impermeable, deformable, extremely viscous and does not bond to the faces of fractures. Thereafter, the fracture sealing composition is squeezed into one or more natural fractures or into one or more new fractures formed in the well bore to thereby increase the pressure containment integrity of the well bore. The methods also include the prediction of the expected increase in pressure containment integrity.

Abstract: A liner hanger test packer assembly includes an axially translated liner top dressing mill having a calibrated shear mechanism for securing the mill at a first, top dressing position. Tool string load on the mill bearing upon the liner top in excess of the calibrated shear mechanism allows the mill to shift to a second axial position where abutment edges around the Mill base engage a tripping mechanism to drive slips against the casing wall above the liner hanger. The tripping mechanism also expands the packer seal against the casing I.D. above the liner hanger. No additional load may be imposed on the liner hanger after the anchor slips have engaged.

Abstract: A test plug tool for use in testing a pressure integrity of a pressure control stack mounted to a wellhead, including a joint between a casing and a casing support in the wellhead. The test plug tool includes a test plug of an appropriate diameter used to pressure test the pressure control stack as well as a joint between any one of a surface casing and the wellhead, an intermediate casing and an intermediate casing mandrel, and a production casing and a production casing mandrel. The pressure integrity of the wellhead is ensured at each stage of well drilling and well completion, and safety is improved. Optionally, a backpressure valve permits pressurized fluid that leaks below the test plug tool to flow upwardly through a central bore in a landing tool that is secured to the test plug tool to permit detection of the leak.

Abstract: The present invention provides a method for remedying minute seal leaks in downhole tools and equipment. The various embodiments of the present invention utilize pressure activated liquid sealants stored in local reservoirs to remedy such leaks.

Abstract: A system and method for transferring data across a component in a well, according to which a first module receives the data and transmits the data, via electromagnetic waves, through the component, and a second module receives the transmitted data from the first module.

Abstract: A method for determining formation pressure at a depth region of formations surrounding a borehole, including: keeping track of the time since cessation of drilling at the depth region; deriving formation permeability at the depth region; causing wellbore pressure to vary periodically in time and determining, at the depth region, the periodic and non-periodic component of pressure measured in the formations; determining, using the time, the periodic component and the permeability, the formation pressure diffusivity and transmissibility and an estimate of the size of the pressure build-up zone around the wellbore at the depth region; determining, using the time, the formation pressure diffusivity and transmissibility, and the non-periodic component, the leak-off rate of the mudcake at the depth region; determining, using the leak-off rate, the pressure gradient at the depth region; and extrapolating, using the pressure gradient and the size of the build-up zone, to determine the formation pressure.

Abstract: A drill-through spool body sleeve assembly comprises a test sleeve removably installed within a drill-through spool body having a bore with the terminal ends of the outer diameter of the test sleeve sealingly engaging the bore wall. The sleeve assembly also comprises a wear bushing removably installed in the bore between the bore wall and the test sleeve. The test sleeve is of sufficient thickness to pressure test the spool body outlets, ports, and valves before drilling and production. The test sleeve seals the bore from the outside of the spool body during the pressure testing. After the pressure tests are completed, the test sleeve is removed from the spool body, leaving the wear bushing in place. The wear bushing protects the bore wall, outlets, ports, and valves while allowing equipment such as drilling and wellhead equipment to pass through the spool body.

Abstract: In accordance with a method of this invention, formation integrity problems are discovered, diagnosed and corrected in successively drilled subterranean well bore intervals. If one or more of well bore fluid outflows, formation fluid inflows or inadequate well bore pressure containment integrity are discovered in a drilled well bore interval, well logs are run and other relevant well bore data is collected in the drilled well bore interval and analyzed to provide a specific treatment using a specific pumpable sealing composition for sealing and increasing the pressure containment integrity of the well bore. Thereafter, the sealing composition is pumped into the drilled well bore interval whereby the well bore interval is sealed or the pressure containment integrity is increased, or both.

Abstract: A test technique and mechanism includes lowering a junction assembly to a junction between at least two bores of a well. The junction assembly includes one or more sealed connections that are tested by the generation of a test flow of fluid. The distal ends of the junction assembly are blocked so that a pressure increase in the junction assembly can be monitored. The level of this pressure increase is used to determine if there is any leakage in the junction assembly. To reduce the costs associated with a faulty junction assembly, the testing is performed during an installation procedure of the junction assembly. Thus, if a faulty junction is detected, it can be quickly removed and replaced with another junction assembly.

Abstract: One embodiment of the present disclosure describes a test assembly including an inflatable packer. An internal control sleeve controls flow of drilling fluid through an inflation port to inflate and deflate the packer. A shifting tool run on a slick line moves the sleeve. The packer has one end attached to an external sliding sleeve which moves upon packer inflation to expose a formation fluid port through which formation testing is performed. After testing and packer deflation, a circulation port may be opened to recover produced fluids up the drill string. A second sleeve controls flow through the circulation port and is controlled by a second shifting tool run on slick line. Other embodiments include a circulation assembly with a sliding sleeve opened and closed by one shifting tool to control circulation and the sliding sleeve itself and its operation.

Abstract: A drill-through spool body sleeve assembly comprises a test sleeve removably installed within a drill-through spool body having a bore with the terminal ends of the outer diameter of the test sleeve sealingly engaging the bore wall. The sleeve assembly also comprises a wear bushing removably installed in the bore between the bore wall and the test sleeve. The test sleeve is of sufficient thickness to pressure test the spool body outlets, ports, and valves before drilling and production. The test sleeve seals the bore from the outside of the spool body during the pressure testing. After the pressure tests are completed, the test sleeve is removed from the spool body, leaving the wear bushing in place. The wear bushing protects the bore wall, outlets, ports, and valves while allowing equipment such as drilling and wellhead equipment to pass through the spool body.

Abstract: The present invention provides a sealing assembly for protecting a downhole connection. The sealing assembly comprises independently energized metal-metal seals and a housing that prevents the energization of individual seals from affecting other seals.

Abstract: A test technique and mechanism includes lowering a junction assembly to a junction between at least two bores of a well. The junction assembly includes one or more sealed connections that are tested by the generation of a test flow of fluid. The distal ends of the junction assembly are blocked so that a pressure increase in the junction assembly can be monitored. The level of this pressure increase is used to determine if there is any leakage in the junction assembly. To reduce the costs associated with a faulty junction assembly, the testing is performed during an installation procedure of the junction assembly. Thus, if a faulty junction is detected, it can be quickly removed and replaced with another junction assembly.

Abstract: A well testing system and well testing method is described which can be operated as a closed system with no production of hydrocarbons outside the well or gas can be separated and flared at surface giving minimal environmental impact with the liquid hydrocarbon being re-injected. This is achieved by providing a string with at least two well conduits which may be arranged in a concentric or non-concentric parallel configuration. One conduit is used to produce formation fluids to surface or to produce/store unrepresentative initial flow products and the other conduit is used to store formation fluid. The storage conduit can be filled from the top (surface) or the bottom of the well. In a preferred arrangement a valve is provided between the storage conduit and the well annulus for well pressure control, and a shut-in or test valve, which is controllable from surface, is disposed in the non-storage production conduit.

Abstract: Methods and apparatus for monitoring and controlling the pressure in a wellbore characterized by a drilling system utilizing real-time bottom hole pressure measurements and a control system adapted to control parameters such as well shut-in, drilling fluid weight, pumping rate, and choke actuation. In the preferred embodiments, the control system receives input from the bottom hole pressure sensor as well as pressure sensors, mud volume sensors, and flowmeters located at the surface. The control system then adjusts one or more of drilling fluid density, pumping rate, or choke actuation to detect, shut-in, and circulate out wellbore influxes. The preferred system operates automatically without any manual intervention in well control processes.

Abstract: A unitary, forward buckling rupture disc is provided that is adapted to be mounted in a holder in which the disc is in closing relationship to a tubing string in an oil well and has greatest utility for testing the integrity of the connection between the sections of oil well tubing strings. The disc is designed to withstand the fluid pressure head in the string and a leak test pressure, and to then burst and fully open under a predetermined overpressure. The concavo-convex bulged section of the disc has a non-circular, continuous score line formed in the concave face thereof. The score line is of continuously varying depth around its circumference and includes an outwardly projecting cam segment which is of greatest depth that ruptures first and is in direct opposition to a lesser depth score line portion forming a hinge area for the burst region of the disc.

Abstract: A liner hanger test packer assembly includes an axially translated liner top dressing mill having a calibrated shear mechanism for securing the mill at a first, top dressing position. Tool string load on the mill bearing upon the liner top in excess of the calibrated shear mechanism allows the mill to shift to a second axial position where abutment edges around the Mill base engage a tripping mechanism to drive slips against the casing wall above the liner hanger. The tripping mechanism also expands the packer seal against the casing I.D. above the liner hanger. No additional load may be imposed on the liner hanger after the anchor slips have engaged.

Abstract: A method and a device for testing of a well, such as in a well liner, a newly drilled hole, and the like, is disclosed. The method is characterised in that a plug is directed down into the well, that the plug is fixed towards the wall of the well the sealing means of the plug is activated to seal against the wall of the well, and after the testing has ceased the sealing function is removed by disintegrating the plug. Preferably a plug of a disintegratable material is used, such as a ceramic material, glass or the like.

Abstract: Apparatus and methods for gravel packing, isolating and testing a sand screen completion of a wellbore in a single trip are disclosed. One method comprises inserting into the wellbore a sand screen assembly, an isolation pipe, and a test assembly on a workstring. A gravel pack operation is performed, and the isolation pipe is shifted to a position in sealing contact with the sand screen assembly, thereby isolating the sand screen assembly. The test assembly is then shifted to a configuration that provides hydraulic communication between the interior of the isolation pipe and the workstring-wellbore annulus above the test assembly. Imposing pressure on the workstring-wellbore annulus then hydraulically tests the integrity of the seal between the isolation pipe and the sand screen assembly.