Abstract: The invention provides a control system and method for limiting vibrations in a tool string system. The system comprises a pump connected to a rotatable tool string driven by a drive system. The control system comprises feedback of both torque and rotational speed signals into a controller. An objective of said controller is to maintain the drive speed over torque ratio equal to the connected tool string impedance (Z). A secondary objective, for lower frequencies, is to approach and maintain a setpoint speed as drive rotation speed. The system includes a rotational speed sensor and a torque sensor, with the latter optionally replaced by a motor torque signal already available from a variable frequency drive (VFD) for an AC motor and the current safeguarding signal for a DC motor.

Abstract: The invention provides a control system and method for limiting vibrations in a tool string system. The system comprises a pump connected to a rotatable tool string driven by a drive system. The control system comprises feedback of both torque and rotational speed signals into a controller. An objective of said controller is to maintain the drive speed over torque ratio equal to the connected tool string impedance (Z). A secondary objective, for lower frequencies, is to approach and maintain a setpoint speed as drive rotation speed. The system includes a rotational speed sensor and a torque sensor, with the latter optionally replaced by a motor torque signal already available from a variable frequency drive (VFD) for an AC motor and the current safeguarding signal for a DC motor.

Abstract: A method of installing a sensor in a borehole drilled through underground formations, wherein the borehole is drilled with a hollow drill string formed from a series of pipe sections connected end-to-end, a drill bit being positioned at one end of the drill string and having a closure member that provides an opening between the borehole and the inside of the drill string, the method comprising: drilling the borehole to a predetermined; partially withdrawing the drill string from the borehole so that the drill bit is positioned above the predetermined depth; lowering a sensor inside the drill string by means of a cable; operating the closure so that the sensor can pass out of the drill string into the borehole; and progressively withdrawing the drill string and drill bit from the borehole over the cable so as to leave the sensor in the borehole.

Abstract: A drill bit comprises a bit body connectable to a drill string at an first end, which bit body is provided with a longitudinal passageway extending from an opening at the first end to a port at a second end. The drill bit further comprises a closure element for closing the passageway, and when the closure element is in a closing position, the closure element is removable. Further, the closure element comprises a first and a second member that are movable relative to each other between an expanded configuration and a collapsed configuration, in which collapsed configuration, the closure element is retractable through the passageway to the first end.

Abstract: A drill bit assembly comprising a bit body connectable to a tubular drill string, and provided with a longitudinal passageway for an operating tool; an externally removable closure element for closing the passageway for the operating tool; and a passage tool attached to or connectable to the closure element in its closing position, wherein the passage tool comprises a lower part to which the closure element is attached or connectable, which lower part is arranged so that it can be moved out of the bit body together with the closure element, and an upper tubular part which is arranged so that it can be moved along the passageway in the bit body, the upper tubular part forming a passage with a downstream opening for the operating tool when the lower part of the passage tool has been moved out of the bit body.

Abstract: A method of drilling a borehole in an earth formation using a drill string including a control system for controlling the borehole trajectory. The control system is operable to receive a selected signal, to determine the borehole depth from at least one length increment and the number of times the selected signal is received, and to use the borehole depth as input parameter for controlling the borehole trajectory in correspondence with a desired borehole trajectory. While drilling, for each length increment that the drill string is lowered into the borehole, transmitting the selected signal to the control system; inducing the control system to determine the borehole depth from said length increment and the number of times the selected signal is received; and operating the control system to use the borehole depth as input parameter for controlling the borehole trajectory in correspondence with the desired borehole trajectory.

Abstract: A method of installing a sensor in a borehole drilled through underground formations, wherein the borehole is drilled with a hollow drill string formed from a series of pipe sections connected end-to-end, a drill bit being positioned at one end of the drill string and having an closure that is operable to provide an opening between the borehole and the inside of the drill string, the method comprising: drilling the borehole to a predetermined depth using the drill string and bit; partially withdrawing the drill string from the borehole so that the drill bit is positioned above the predetermined depth; lowering a sensor inside the drill string by means of a cable; operating the closure so that the sensor can pass out of the drill string into the borehole; and progressively withdrawing the drill string and drill bit from the borehole over the cable so as to leave the sensor in the borehole.

Abstract: A drill bit comprising a bit body connectable to a drill string at an first end, which bit body is provided with a longitudinal passageway extending from an opening at the first end to a port at a second end a closure element for closing the passageway, when the closure element is in a closing position, which closure element is removable, and wherein the closure element comprises a first and a second member which are movable relative to each other between an expanded configuration and a collapsed configuration, in which collapsed configuration, the closure element is retractable through the passageway to the first end.

Abstract: A drill bit assembly comprising a bit body connectable to a tubular drill string, and provided with a longitudinal passageway for an operating tool; an externally removable closure element for closing the passageway for the operating tool; and a passage tool attached to or connectable to the closure element in its closing position, wherein the passage tool comprises a lower part to which the closure element is attached or connectable, which lower part is arranged so that it can be moved out of the bit body together with the closure element, and an upper tubular part which is arranged so that it can be moved along the passageway in the bit body, the upper tubular part forming a passage with a downstream opening for the operating tool when the lower part of the passage tool has been moved out of the bit body.

Abstract: A wellstring assembly comprising a tubular first wellstring part with a passageway; a second wellstring part co-operating with the first wellstring part; and a releasable wellstring-interconnecting means for selectively interconnecting the first and second wellstring parts; an auxiliary tool for manipulating the second wellstring part, which auxiliary tool can pass along the passageway in the first wellstring part to the second wellstring part, comprising a tool-connecting means for selectively connecting the auxiliary tool to the second wellstring part, and an operating means for operating the wellstring-interconnecting means.

Abstract: A method of drilling a borehole into a subsurface earth formation, using a tubular drill string which includes at its lower end a bottom hole assembly comprising a drill bit, a drill steering system, and a surveying system. The drill string includes a selectively closable passageway for passing an auxiliary tool from a first position interior of the drill string above the bottom hole assembly to a second position. In the second position, at least part of the auxiliary tool is exterior of the drill string below the bottom hole assembly. The drill string is progressed into the earth formation by drilling. When a tool operating condition is met the passageway is opened and the auxiliary tool is passed through the passageway from the first position to the second position, where the auxiliary tool is operated.

Abstract: A method and system for introducing a fluid into a borehole, in which there is arranged a tubular drill string including a drill bit, wherein the drill bit is provided with a passageway between the interior of the drill string and the borehole, and with a removable closure element for selectively closing the passageway in a closing position, and wherein there is further provided a fluid injection tool comprising a tool inlet and a tool outlet, the method comprising passing the fluid injection tool through the drill string to the closure element, and using it to remove the closure element from the closing position, passing the fluid injection tool outlet through the passageway, and introducing the fluid into the borehole from the interior of the drill string through fluid injection tool into the borehole.

Abstract: A rotary drill bit assembly suitable for directionally drilling a borehole into an underground formation, the drill bit assembly having a bit body extending along a central longitudinal bit-body axis, and having a bit-body face at its front end, wherein an annular portion of the bit-body face is provided with one or more chip-making elements; a pilot bit extending along a central longitudinal pilot-bit axis, the pilot bit being partly arranged within the bit body and projecting out of the central portion of the bit-body face, the pilot bit having a pilot-bit face provided with one or more chip-making elements at its front end; a joint means arranged to pivotably connect the pilot bit to the bit body so that the bit-body axis and the pilot-bit axis can form a variable diversion angle; and a steering means arranged to pivot the pilot bit in order to steer the direction of drilling.

Abstract: A well string assembly includes an upper tubular well string part having upper and lower ends between which there is formed a passageway, a lower well string part having upper and lower ends, which lower end is spaced apart from the lower end of the upper well string part and may include a drill bit. An auxiliary tool is arranged such that it can be passed along the passageway. It comprises an operating means for manipulating the well string interconnection means so as to disconnect the lower well string part from the upper well string part. The auxiliary tool can be passed, after disconnecting the upper and lower well string parts, through an opening at the lower end of the upper well string part, so as to reach a position in which at least part of the auxiliary tool is not radially surrounded by a part of the well string.

Abstract: A well drilling bit having a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway providing fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body; a closure element for selectively closing the passageway; and one or more chip-making elements, wherein the chip-making elements has one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position to an opening position, and wherein the closure element includes at least one of the roller-cones.

Abstract: A logging system that may be used in a wellbore formed in an earth. A tubular conduit extends from surface into the wellbore and contains a body of wellbore fluid. A logging tool string may be passed from a position within the conduit to a position outside the conduit at a lower end part thereof, and may be suspended by the conduit in the position outside the conduit. A pressure pulse device is arranged within the conduit in a manner that the pressure pulse device is in data communication with the logging tool. The pressure pulse device is capable of generating pressure pulses in the body of wellbore fluid, which pressure pulses represent data communicated by the logging tool string to the pressure pulse device during logging of earth formation by the logging tool string. The system further includes a control system in fluid communication with the body of wellbore fluid and arranged to receive the pressure pulses.

Abstract: A method for reducing longitudinal flow of fluids through an annular space surrounding a permeable well tubular, such as a slotted liner or a sandscreen, in an inflow region of an oil and/or gas production well having: arranging a series of collapsed resilient sealing rings at regular longitudinal intervals around the permeable tubular before lowering the tubular into the well by means of tape and/or a binder which dissolves downhole; placing the tubular in the inflow region of the well; and allowing the tape and/or binder to dissolve, thereby allowing the resilient sealing rings to expand radially in the annular space surrounding the permeable tubular.

Abstract: A well drilling bit having a bit body attachable to a tubular drill string, which bit body is internally provided with a passageway providing fluid communication, when the drill string is attached to the bit body, between the interior of the drill string and the exterior of the bit body; a closure element for selectively closing the passageway; and one or more chip-making elements, wherein the chip-making elements has one or more roller-cones, wherein the closure element is releasably connectable to the bit body, and outwardly movable from a closing position to an opening position, and wherein the closure element includes at least one of the roller-cones.

Abstract: A rotary drill bit assembly suitable for directionally drilling a borehole into an underground formation, the drill bit assembly having a bit body extending along a central longitudinal bit-body axis, and having a bit-body face at its front end, wherein an annular portion of the bit-body face is provided with one or more chip-making elements; a pilot bit extending along a central longitudinal pilot-bit axis, the pilot bit being partly arranged within the bit body and projecting out of the central portion of the bit-body face, the pilot bit having a pilot-bit face provided with one or more chip-making elements at its front end; a joint means arranged to pivotably connect the pilot bit to the bit body so that the bit-body axis and the pilot-bit axis can form a variable diversion angle; and a steering means arranged to pivot the pilot bit in order to steer the direction of drilling.

Abstract: A method and system for introducing a fluid into a borehole, in which there is arranged a tubular drill string including a drill bit, wherein the drill bit is provided with a passageway between the interior of the drill string and the borehole, and with a removable closure element for selectively closing the passageway in a closing position, and wherein there is further provided a fluid injection tool comprising a tool inlet and a tool outlet, the method comprising passing the fluid injection tool through the drill string to the closure element, and using it to remove the closure element from the closing position; passing the fluid injection tool outlet through the passageway, and introducing the fluid into the borehole from the interior of the drill string through fluid injection tool into the borehole.