Abstract: A wellbore drilling system includes a weight on bit controller configured to generate a normalized weight on bit output, a drilling torque controller configured to generate a normalized toque on bit output, and a differential pressure controller configured to generate a normalized differential pressure output. The system further includes a rate of penetration controller that is configured to multiply a rate of penetration setpoint with the normalized weight on bit output, the normalized torque on bit output, and the normalized differential pressure output to generate a rate of penetration output.

Abstract: A system for reverse circulation in a wellbore includes equipment for supplying drilling fluid into the wellbore bit via at least an annulus of the wellbore and returning the drilling fluid to a surface location via at least a bore of a wellbore tubular. The system also includes devices for controlling the annulus pressure associated with this reverse circulation. An active pressure differential device may increase the pressure wellbore annulus to at least partially offset a circulating pressure loss. Alternatively, the system may include devices for decreasing the pressure in the annulus of the wellbore.

Abstract: A steering tool has a controller configured to provide closed-loop control of blade pressure and position. In one embodiment, the controller is configured to execute a directional control methodology in which the drilling direction is controlled via control of the blade position. The pressure in each blade is further controlled within a predetermined range of pressures. This embodiment tends to prevent excessive borehole friction while at the same time reducing undesirable rotation of the blade housing. In another embodiment, the controller is configured to correlate blade pressure measurements and blade position measurements during drilling. The correlation is utilized as part of a secondary directional control scheme in the event of a downhole failure of a blade position and/or pressure sensor.

Abstract: One exemplary APD Device is used with a liner drilling assembly to control wellbore pressure. The APD Device reduces a dynamic pressure loss associated with the drilling fluid returning via a wellbore annulus. Another exemplary APD Device is used to control pressure in a wellbore when deploying wellbore equipment, including running, installing and/or operating wellbore tools. The APD Device is set to reduce a dynamic pressure loss associated with a circulating fluid. The APD Device can also be configured to reduce a surge effect associated with the running of the wellbore equipment. Still another APD Device is used to control pressure in a wellbore when completing or working over a well. Exemplary completion activity can include circulating fluid other than a drilling fluid, such as a gravel slurry. The APD Device can reduce the dynamic pressure loss associated with circulation of both drilling fluid and non-drilling fluid.

Abstract: A method for determining formation integrity during drilling of a wellbore includes determining an annulus fluid pressure in a wellbore during drilling thereof. The annulus pressure is adjusted by a predetermined amount. Flow rate of drilling fluid into the wellbore is compared to drilling fluid flow rate out of the wellbore. At least one of a formation pore pressure and a formation fracture pressure is determined from the annulus pressure when the compared flow rates differ by a selected amount. The method alternatively to determining pore and/or fracture pressure includes determining a response of the wellbore to the adjusted fluid pressure and determining the optimum annulus fluid pressure from the wellbore response.

Abstract: Aspects of this invention include a downhole tool and method for making a physical caliper measurement of a subterranean borehole. The tool is configured to make the physical borehole caliper measurement only when the measured pressure in each of three or more outwardly extendable blades is greater than a predetermined threshold pressure. Blade positions are measured and the borehole caliper calculated only when the pressure in each of the blades exceeds the threshold. Exemplary embodiments of the invention enable physical caliper measurements to be made with increased accuracy with each of the blades making firm contact with the borehole wall. Methods in accordance with the invention are especially well suited for use in directional drilling applications in that they tend to enable accurate caliper measurements to be made without repositioning the steering tool in the borehole.

Abstract: A well drilling system for use with a drilling fluid pump includes a flow control device regulating flow from the pump to a drill string interior; and another flow control device regulating flow through a line in communication with an annulus. Flow is simultaneously permitted through the flow control devices. A method of maintaining a desired bottom hole pressure includes dividing drilling fluid flow between a line in communication with a drill string interior and a line in communication with an annulus; the flow dividing step including permitting flow through a flow control device interconnected between a pump and the drill string interior; and the flow dividing step including permitting flow through another flow control device interconnected between the pump and the annulus, while flow is permitted through the first flow control device.

Abstract: A system and method is described for use and return of drilling fluid/cuttings from a well, which is drilled on the ocean floor, in connection with offshore related oil production and gas production, where, from a drilling rig or drilling vessel (10), a drill stem (12) runs down into the bore hole and where a blowout preventer (BOP) is placed on said well, without mounting a riser between the rig or the vessel and said blowout preventer. A sealing and pressure-regulating device (16) is arranged on the blowout preventer (14) arranged to regulate the level of the drilling fluid, and thus the outlet pressure of the drilling fluid in said sealing and pressure-regulating device, and a pump module (18) is set up at a suitable distance adjacent said sealing and pressure-regulating device, where the pump module is arranged to pump said drilling fluid up to the ocean surface via an external return pipe.

Abstract: The present disclosure is directed to methods and apparatuses for controlling pump power draw from an engine in horizontal directional drilling.

Abstract: A method for controlling a drilling apparatus comprising the steps of applying a rotation force to a drilling part of the drilling apparatus, applying a feed force to the drilling part with the feed force comprising a predetermined modulating frequency signal and predetermined feed force, wherein optimum predetermined feed force is determined periodically from sensed data relating to at least one of the rotation force and feed force to optimise the penetration rate of the drilling apparatus.

Abstract: In one embodiment, a method for drilling a wellbore includes an act of drilling the wellbore by injecting drilling fluid through a tubular string disposed in the wellbore, the tubular string comprising a drill bit disposed on a bottom thereof. The drilling fluid exits the drill bit and carries cuttings from the drill bit. The drilling fluid and cuttings (returns) flow to a surface of the wellbore via an annulus defined by an outer surface of the tubular string and an inner surface of the wellbore. The method further includes an act performed while drilling the wellbore of measuring a first annulus pressure (FAP) using a pressure sensor attached to a casing string hung from a wellhead of the wellbore. The method further includes an act performed while drilling the wellbore of controlling a second annulus pressure (SAP) exerted on a formation exposed to the annulus.

Abstract: A method of drilling a bore hole in a fractured formation. A drill pipe is deployed into the borehole, whereby an annular space is formed between the drill pipe and the borehole wall. A drilling fluid is pumped, by means of primary pumps, into the borehole via an internal conduit of the drill pipe and a drill pipe fluid outlet present in the vicinity of a distal end of the drill pipe. The annular space is pressure sealed using a pressure seal such as a rotating head on a BOP. A well control fluid is pumped into the annular space via a well control conduit that fluidly connects the annular space, in a location between the pressure seal and the drill pipe fluid outlet, to a backpressure system. The well control fluid is pressure-balanced against the pressure seal and the backpressure system.

Abstract: An APD Device provides a pressure differential in a wellbore to control dynamic pressure loss while drilling fluid is continuously circulated in the wellbore. A continuous circulation system circulates fluid both during drilling of the wellbore and when the drilling is stopped. Operating the APD Device allows wellbore pressure control during continuous circulation without substantially changing density of the fluid. The APD Device can maintain wellbore pressure below the combined pressure caused by weight of the fluid and pressure losses created due to circulation of the fluid in the wellbore, maintain the wellbore at or near a balanced pressure condition, maintain the wellbore at an underbalanced condition, reduce the swab effect in the wellbore, and/or reduce the surge effect in the wellbore. A flow restriction device that creates a backpressure in the wellbore annulus provides surface control of wellbore pressure.

Abstract: The invention relates to a gear unit, in particular for foundation engineering devices, comprising a gear housing and a pressure device for changing an internal pressure present in the gear housing. For a precise pressure balance to the environmental pressure it is intended that an active setting device is arranged which can be controlled by a control device in order to change the internal pressure. The invention further relates to a method for pressure balance related thereto.

Abstract: A method for creating a programmable pressure zone adjacent a drill bit bottom hole assembly by sealing near a drilling assembly, adjusting the pressure to approximately or slightly below the pore pressure of the well bore face to permit flow out of the formation, and, while drilling, adjusting by pumping out of, or choking fluid flow into, the drilling assembly between the programmable pressure zone and the well bore annulus to avoid overpressuring the programmable pressure zone unless required to control the well.

Abstract: A wellbore drilling system is disclosed herein, in which the system includes a weight on bit controller configured to generate a normalized weight on bit output, a drilling torque controller configured to generate a normalized toque on bit output, and a differential pressure controller configured to generate a normalized differential pressure output. The system further includes a rate of penetration controller that is configured to multiply a rate of penetration setpoint with the normalized weight on bit output, the normalized torque on pit output, and the normalized differential pressure output to generate a rate of penetration output.

Abstract: A method for determining formation integrity during drilling of a wellbore includes determining an annulus fluid pressure in a wellbore during drilling thereof. The annulus pressure is adjusted by a predetermined amount. Flow rate of drilling fluid into the wellbore is compared to drilling fluid flow rate out of the wellbore. At least one of a formation pore pressure and a formation fracture pressure is determined from the annulus pressure when the compared flow rates differ by a selected amount. The method alternatively to determining pore and/or fracture pressure includes determining a response of the wellbore to the adjusted fluid pressure and determining the optimum annulus fluid pressure from the wellbore response.

Abstract: Methods and control systems are provided for a wellbore drilling system having an active differential pressure device (APD device) in fluid communication with a returning fluid. The APD Device creates a differential pressure across the device, which reduces the pressure below or downhole of the device. In embodiments, a control unit controls the APD Device in real time via a data transmission system. In one arrangement, the data transmission system includes data links formed by conductors associated with the drill string. The conductors, which may include electrical wires and/or fiber optic bundles, couple the control unit to the APD Device and other downhole tools such as sensors. In other arrangements, the data link can include data transmission stations that use acoustic, EM, and/or RF signals to transfer data. In still other embodiments, a mud pulse telemetry system can be used in transfer data and command signals.

Abstract: A method of downlinking to a downhole tool located in a borehole is provided. The downhole tool detects transitions in the flow velocity of fluid circulating in the borehole at the downhole tool. To provide for the detection of the transitions fluid is pumped into the drillstring so that it circulates in the borehole at the downhole tool and the pumping rate of fluid into the drillstring is either increased to a rate which overshoots a steady state pumping rate needed to produce a transition or is decreased to a rate which undershoots a steady state pumping rate needed to produce a transition.

Abstract: A method for determining a track of a geographical trajectory which has predetermined start and locations. A data collection device, which has onboard synchronized sensors, is moved between the start and end locations, and physical measurement data such as pitch, heading, roll and distance, is obtained and stored. Thereafter, the stored data is retrieved and mapped to determine error compensation. The physical measurement data, after error compensation, is used to determine the pitch profile, heading profile, distance profile and roll profile to ascertain the geographical trajectory track.

Abstract: A purely mechanical hydraulic control system includes at least one drilling fluid chamber and a hydraulic fluid chamber. A system pressure spring is deployed in one of the drilling fluid chamber(s) between a positioning piston and a system pressure piston. The spring is disposed to pressurize oil in the hydraulic fluid chamber via applying a spring force to the system pressure piston. When the system is actuated (e.g., via turning on the mud pumps), the positioning piston is urged in place against a stop (e.g., a shoulder) thereby compressing the system pressure spring and pressurizing oil in the hydraulic chamber. The invention advantageously converts highly variable drilling fluid pressure to a near constant pressure hydraulic fluid.

Abstract: A downhole tool including a purely mechanical stabilizer is disclosed. The stabilizer includes a plurality of fixed blades, each of which includes at least one automatically extendable and retractable piston. In use, a balance of forces determines the radial position of each piston; a hydraulic force urging the piston outward, a spring force urging the piston inward, and external forces acting on the tool (e.g., the force of the borehole wall urging the pistons inward). The stabilizer is further configured such that a balance of forces between the pistons causes the tool to be advantageously automatically and continuously centered during rotation of the tool in the borehole. As such, the invention is suitable for use in boreholes that rapidly change size and shape.

Abstract: A method for controlling formation pressure during drilling includes pumping a drilling fluid through a drill string in a borehole, out a drill bit at the end of the drill string into an annular space. The drilling fluid is discharged from the annular space proximate the Earth's surface. At least one of a flow rate of the drilling fluid into the borehole and a fluid flow rate out of the annular space is measured. Pressure of the fluid in the annular space proximate the Earth's surface and pressure of the fluid proximate the bottom of the borehole are measured. Pressure of the fluid proximate the bottom of the borehole is estimated using the measured flow rate, annular space pressure and density of the drilling fluid. A warning signal is generated if difference between the estimated pressure and measured pressure exceeds a selected threshold.

Abstract: An anti-stall tool in an oil well drilling assembly that controls reciprocation of the drill bit by controller that alters weight-on-bit (WOB) depending upon measured downhole pressure or torque. The downhole controller keeps the drill bit rotating by maintaining WOB during normal drilling operations, increasing WOB if sensed working pressure indicates that drill bit loading or torque is undesirably low, and reversing WOB by applying a spring force for retracting the drill bit if excessive working pressure or torque is sensed.

Abstract: An anti-stall tool in an oil well drilling assembly that controls reciprocation of the drill bit by a controller that alters weight-on-bit (WOB) depending upon measured downhole pressure or torque at the downhole motor. The controller receives preset high and low working pressure limits for the downhole motor and keeps the drill bit rotating by maintaining WOB during normal drilling operations, increasing WOB if sensed working pressure indicates that drill bit loading or torque is undesirably low, and reversing WOB by retracting the drill bit if excessive working pressure or torque is sensed.

Abstract: A steering tool has a controller configured to provide closed-loop control of blade pressure and position. In one embodiment, the controller is configured to execute a directional control methodology in which the drilling direction is controlled via control of the blade position. The pressure in each blade is further controlled within a predetermined range of pressures. This embodiment tends to prevent excessive borehole friction while at the same time reducing undesirable rotation of the blade housing. In another embodiment, the controller is configured to correlate blade pressure measurements and blade position measurements during drilling. The correlation is utilized as part of a secondary directional control scheme in the event of a downhole failure of a blade position and/or pressure sensor. This embodiment tends to provide a stable and reliable backup directional control mechanism in the event a sensor failure and therefore may save considerable rig time.

Abstract: A method and apparatus for down hole abrasive jet-fluid cutting, the apparatus includes a jet-fluid nozzle and a high pressure pump capable of delivering a high-pressure abrasive fluid mixture to the jet-fluid nozzle, an abrasive fluid mixing unit capable of maintaining and providing a coherent abrasive fluid mixture, a tube to deliver the high pressure coherent abrasive mixture down hole to the jet-fluid nozzle, a jetting shoe adapted to receive the jet-fluid nozzle and directing abrasive jet-fluid mixture towards a work piece, a jetting shoe controlling unit that manipulates the jetting shoe along a vertical and horizontal axis and a central processing unit having a memory unit capable of storing profile generation data for cutting a predefined shape or window profile in the work piece and coordinating the operation of various subsystems.

Abstract: A method for fracturing a wellbore while drilling a wellbore includes inserting a drill string into a wellbore. A fluid is pumped into at least one of an interior passage in the drill string and an annular space between a wall of the wellbore and the drill string. At least one of a pressure and a temperature of the fluid proximate a lower end of the drill string is measured and the measurements are transmitted to the surface substantially contemporaneously with the measuring. At least one of a flow rate and a pressure of the fluid is controlled in response to the measurements to selectively create fractures in formations adjacent to the wellbore.

Abstract: A pressure compensation system for a wellbore instrument coupled to a drill string includes a shaft rotatably mounted with respect to an instrument housing. A lubrication chamber included in the instrument has at least one bearing for rotatably supporting the shaft. The lubrication chamber includes a face seal coupled on one face to the shaft and on another face to the housing. A pressure compensator establishes hydraulic communication between the lubrication chamber and the interior of the drill string. The compensator includes a barrier to fluid movement between the lubrication chamber and the interior of the drill string. The barrier enables pressure communication therebetween. The compensator includes a pressure communication port extending between the barrier and a portion of the shaft exposed to the interior of the drill string.

Abstract: The present invention relates to a device for controlling the Blow out preventer (BOP) used in well drilling operations comprising: BOP control unit, master control panel connected to the BOP unit for acquisition of data and processing the said data, comprising an input module, an output module and analog I/P module; a plurality of slave panels connected to master panel through the connecting means comprising input module, output module for controlling the BOP control unit; wherein the said slave panel is a programmable logic controller(PLC) for controlling BOP control unit.

Abstract: A method for controlling a drilling apparatus comprising the steps of applying a rotation force to a drilling part of the drilling apparatus, applying a feed force to the drilling part with the feed force comprising a predetermined modulating frequency signal and predetermined feed force, wherein optimum predetermined feed force is determined periodically from sensed data relating to at least one of the rotation force and feed force to optimise the penetration rate of the drilling apparatus.

Abstract: According to the invention, a bottom hole assembly for drilling a cavity is disclosed. The bottom hole assembly may include a chassis configured to rotate. The chassis may include a primary fluid conduit, a secondary fluid circuit, a pressure transfer device, a plurality of pistons, a plurality of valves, and a plurality of cutters. The primary fluid conduit may be accept a first fluid flow. The secondary fluid circuit may have a second fluid flow. The pressure transfer device may be configured to transfer pressure between the flows. The pistons may be operably coupled with the secondary fluid circuit, and each piston may be configured to move based at least in part on a pressure of the secondary fluid circuit at that piston, with the valves possibly configured to control a pressure of the secondary fluid circuit at each piston. Each cutter may be coupled with one of the pistons.

Abstract: Disclosed is a system and device relating to flow pulsing for use in down-hole drilling rate of penetration (ROP) enhancement and measurement while drilling (MWD) using a pulse drilling device (PDD) with a fast acting valve in conjunction with a pilot valve to produce high pressure, high amplitude, low duration pressure pulses.

Abstract: A system and method is provided for a low profile rotating control device (LP-RCD) and its housing mounted on or integral with an annular blowout preventer seal, casing, or other housing. The LP-RCD and LP-RCD housing can fit within a limited space available on drilling rigs.

Abstract: The present disclosure is directed to methods and apparatuses for controlling pump power draw from an engine in horizontal directional drilling.

Abstract: A method and apparatus for predicting and controlling secondary kicks, while dealing with a primary kick experienced when drilling an oil and gas well. The method includes a step of determining whether a different pressure per cubic meter of mud pit volume has been caused by a secondary kick by subtracting shut in drill pipe pressure (SIDPP) from shut in casing pressure (SICP) and dividing the derived sum by a kick volume in KPa per cubic meter from the primary kick. A further step is then taken of increasing casing pressure until casing pressure equals pit gain times (X) rate of change in casing pressure per cubic meter of pit gain plus (+) SIDPP.

Abstract: A cased hole pressure test tool is used to determine the integrity of cement between two points in a borehole in terms of permeability or transmissibility. The test tool drills at least one probe hole through the casing up to the cement. In one embodiment, two probes are set and the dissipation of a pressure pulse through the cement initiated by the first probe is observed by the second probe. In another embodiment, one probe hole is in hydraulic communication with the borehole fluid and a single offset probe is set in another probe hole. Fluid (water) is then added to the borehole to cause a pressure increase in the borehole fluid. Detection of the pressure increase through the cement by the offset probe is indicative of a loss of hydraulic isolation. Packers may be used to isolate the portion of the borehole under test. A mechanism for generating a pressure pulse of known magnitude is also described.

Abstract: Aspects of this invention include a steering tool having a controller configured to provide closed-loop control of hydraulic fluid pressure. In one exemplary embodiment, closed-loop control of a system (reservoir) pressure may be provided. In another embodiment, closed-loop control of a blade pressure may be provided while the blade remains substantially locked at a predetermined position. Other exemplary embodiments may incorporate rule-based-intelligence such that pressure control thresholds may be determined based on various measured and/or predetermined downhole parameters. The invention tends to reduce the friction (drag) between the blades and the borehole wall and thereby also tends to improve drilling rates. Moreover, the invention also tends to improve the service life and reliability of downhole steering tools.

Abstract: A method and system for controlling drilling mud density in drilling operations. The mud required at the wellhead is combined with a base fluid of a different density to produce diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, riser mud density at or near the density of seawater may be achieved, thereby permitting greater control over the pressure in the wellbore and various risers. Blowout preventers may also be used in combination with the process to control these pressures. Concentric risers are disclosed, wherein an annulus defined within one riser is utilized to carry the different density base fluid to the injection point for injection into the drilling mud, while an annulus defined within another riser is utilized to carry the combination fluid and cuttings back to the drilling rig. Cuttings are separated in the usual manner at the surface.

Abstract: A method and system for controlling drilling mud density in drilling operations. The mud required at the wellhead is combined with a base fluid of a different density to produce diluted mud in the riser. By combining the appropriate quantities of drilling mud with base fluid, riser mud density at or near the density of seawater may be achieved, thereby permitting greater control over the pressure in the wellbore and various risers. Blowout preventers may also be used in combination with the process to control these pressures. Concentric risers are disclosed, wherein an annulus defined within one riser is utilized to carry the different density base fluid to the injection point for injection into the drilling mud, while an annulus defined within another riser is utilized to carry the combination fluid and cuttings back to the drilling rig. Cuttings are separated in the usual manner at the surface.

Abstract: A testing apparatus comprising: a chamber (5) having an inlet (6) and an outlet (16); a measuring device (4), at least a part of which is provided within said chamber; wherein the inlet is arranged to direct fluid onto said part of the measuring device within the chamber in order to clean the measuring device during start up. Thus the density or viscosity of drilling mud may be continuously monitored. Preferred embodiments include an outlet valve such as a ball valve (7) with a bore defined therein. The bore allows fluid to flow therethrough even in a valve “closed” position and so generates the preferred back pressure whilst minimising the risk that the valve will block. A pressure activated drain valve (9) is also provided to substantially empty the chamber when not in use. When the apparatus is reactivated, an inlet tube is adapted to jet air and then fluid at the measuring device in order to remove debris therefrom. Thus the apparatus has the important benefit of self cleaning during start-up.

Abstract: Disclosed is a device and method and/or system for generating pulses to improve drilling rates, the ability to drill straighter and farther or fracturing or injection efficiencies in a geological formation that may contain desirable hydrocarbons. This system may also be used in other types of drilling or fracturing operations, whether to unclog arteries or to open formations for underground storage in conjunction with pulsing/fracturing. Alternately, this system could be used to create large pulses downhole for seismic purposes in that they are of such magnitude that they could be readily received in nearby wells or several of uphole locations.

Abstract: A method for creating a programmable pressure zone adjacent a drill bit bottom hole assembly by sealing near a drilling assembly, adjusting the pressure to approximately or slightly below the pore pressure of the well bore face to permit flow out of the formation, and, while drilling, adjusting by pumping out of, or choking fluid flow into, the drilling assembly between the programmable pressure zone and the well bore annulus to avoid overpressuring the programmable pressure zone unless required to control the well.

Abstract: An anti-surge/reverse thrusting tool for reducing the forces on a drill bit used in subterranean well drilling operations is provided along with methods for drilling wells using a drill string employing the tool. The tool utilizes the pressure differential between drilling fluid flowing through the tool and the fluid located in the well bore annulus proximate the tool to reduce the likelihood of drill bit stall. The tool generally comprises an outer housing and a piston assembly that is axially shiftable relative to the housing.

Abstract: A method of dynamically controlling open hole pressure within a wellbore having a drill string positioned therein. The method comprising the steps of pumping a fluid down the drill string, into an annulus formed by the drill string and the interior of the wellbore, and then subsequently up the annulus to the surface of the ground; selectively applying wellhead pressure to the annulus through selectively pumping an additional quantity of the fluid or a quantity of a secondary fluid across the annulus; and, controlling the application of wellhead pressure applied to the annulus by controlling one, or both, of (a) the operation of a wellhead pressure control choke, and (b) the flow rate of the additional quantity of fluid or the secondary fluid pumped across the annulus, to thereby maintain open hole pressure within a desired range.

Abstract: A drill fluid supply device includes a drill fluid container. A pump is fluidly coupled to the drill fluid container. The pump configured to move drill fluid from within the container. A drill fluid supply receiver is configured to receive wireless signals to control at least the pump.

Abstract: The present invention generally provides apparatus and methods for reducing the pressure of a circulating fluid in a wellbore. In one aspect of the invention an ECD (equivalent circulation density) reduction tool provides a means for drilling extended reach deep (ERD) wells with heavyweight drilling fluids by minimizing the effect of friction head on bottomhole pressure so that circulating density of the fluid is close to its actual density. With an ECD reduction tool located in the upper section of the well, the friction head is substantially reduced, which substantially reduces chances of fracturing a formation.

Abstract: A method of controlling one or more operating pressures within a subterranean borehole that includes a choke assembly comprising a housing having an inlet passage, an axial bore, and a chamber, wherein a portion of the axial bore forms an outlet passage, and a choke member adapted for movement in the housing to control the flow of a fluid from the inlet passage to the outlet passage. The method may include applying a closing force to move the choke member toward a closed position, and applying a bias force to the choke member when in the closed position to reduce an overpressure required to initiate movement of the choke member from the closed position.

Abstract: A method of responding to an anomalous change in downhole pressure in a bore hole comprises detecting the anomalous change in downhole pressure, sending a signal along the segmented electromagnetic transmission path, receiving the signal, and performing a automated response. The anomalous change in downhole pressure is detected at a first location along a segmented electromagnetic transmission path, and the segmented electromagnetic transmission path is integrated into the tool string. The signal is received by at least one receiver in communication with the segmented electromagnetic transmission path. The automated response is performed along the tool string. Disclosed is an apparatus for responding to an anomalous change in downhole pressure in a downhole tool string, comprising a segmented electromagnetic transmission path connecting one or more receivers and at least one pressure sensor.

Abstract: An arrangement and a method to control and regulate the bottom hole pressure in a well during subsea drilling at deep waters: The method involves adjustment of a liquid/gas interface level in a drilling riser up or down. The arrangement comprises a high pressure drilling riser and a surface BOP at the upper end of the drilling riser. The surface BOP havs a gas bleeding outlet. The riser also comprises a BOP, with a by-pass line. The drilling riser has an outlet at a depth below the water surface, and the outlet is connected to a pumping system with a flow return conduit running back to a drilling vessel/platform.