An underbalanced drilling system is provided. A bottomhole assembly includes a drill bit drilling a wellbore in a formation underbalanced. The bottomhole assembly includes a telemetry sub. A telemetry component transmits signals in real-time between the telemetry sub of the bottomhole assembly and a controller on the surface. A drill string is coupled with the bottomhole assembly, and the drill string includes a plurality of drill collars. The drill collars form a channel through which drilling fluid flows from the surface to the bottomhole assembly. The drill string is inserted into the wellbore by a hydraulic work over unit. A continuous circulation component provides continuous circulation of the drilling fluid while a new drill collar is coupled to the drill string. The continuous circulation component substantially maintains a wellbore density at a predetermined density.

An underbalanced drilling system is provided. A bottomhole assembly includes a drill bit drilling a wellbore in a formation underbalanced. The bottomhole assembly includes a telemetry sub. A telemetry component transmits signals in real-time between the telemetry sub of the bottomhole assembly and a controller on the surface. A drill string is coupled with the bottomhole assembly, and the drill string includes a plurality of drill collars. The drill collars form a channel through which drilling fluid flows from the surface to the bottomhole assembly. The drill string is inserted into the wellbore by a hydraulic work over unit. A continuous circulation component provides continuous circulation of the drilling fluid while a new drill collar is coupled to the drill string. The continuous circulation component substantially maintains a wellbore density at a predetermined density.

A method for geosteering while drilling a well in a subterranean formation using a downhole assembly having a toolface comprises measuring at least one motion-related downhole parameter relative to the toolface angle so as to generate azimuthally-associated data, using the azimuthally-associated data to assess formation anisotropy, and using the anisotropy assessment to manually or automatically steer a well while drilling the well. The motion-related downhole parameter may relate to motion of an asymmetric bit or bent housing or bent housing section. The downhole parameter may be selected from the group consisting of angular velocity, angular acceleration, tangential acceleration, radial acceleration, axial acceleration, cross-axial acceleration, total acceleration, high-frequency torsional oscillation (HFTO) severity, band-pass-filtered root-mean-square (RMS) acceleration, band-pass-filtered peak acceleration and the azimuthally-associated data may comprise azimuthally-associated measurements of any of the motion-related parameters and/or azimuthally-associated calculations of compressive strength, Young's modulus, Poisson's ratio, stress, and fracture measurement.

A method for geosteering while drilling a well in a subterranean formation using a downhole assembly having a toolface comprises measuring at least one motion-related downhole parameter relative to the toolface angle so as to generate azimuthally-associated data, using the azimuthally-associated data to assess formation anisotropy, and using the anisotropy assessment to manually or automatically steer a well while drilling the well. The motion-related downhole parameter may relate to motion of an asymmetric bit or bent housing or bent housing section. The downhole parameter may be selected from the group consisting of angular velocity, angular acceleration, tangential acceleration, radial acceleration, axial acceleration, cross-axial acceleration, total acceleration, high-frequency torsional oscillation (HFTO) severity, band-pass-filtered root-mean-square (RMS) acceleration, band-pass-filtered peak acceleration and the azimuthally-associated data may comprise azimuthally-associated measurements of any of the motion-related parameters and/or azimuthally-associated calculations of compressive strength, Young's modulus, Poisson's ratio, stress, and fracture measurement.

A method for controlling a MWD tool in a bottom hole assembly in a borehole includes the steps of installing a plurality of firmware in the MWD tool, turning a mud pump on an earth surface ON or OFF according to a pre-determined sequence; determining a mud flow in the borehole to be ON or OFF so as to form a binary signal; and sending the binary signal to the MWD tool. The plurality of firmware are pre-programmed to perform a plurality of tasks while the binary signal executes one of the plurality of firmware in the MWD tool.

A method for controlling a MWD tool in a bottom hole assembly in a borehole includes the steps of installing a plurality of firmware in the MWD tool, turning a mud pump on an earth surface ON or OFF according to a pre-determined sequence; determining a mud flow in the borehole to be ON or OFF so as to form a binary signal; and sending the binary signal to the MWD tool. The plurality of firmware are pre-programmed to perform a plurality of tasks while the binary signal executes one of the plurality of firmware in the MWD tool.

A near-bit multi-parameter downhole measurement and control system while drilling, including a ground device and a downhole assembly. The downhole assembly includes a drill bit, a multi-parameter acquisition and signal transmission sub, a positive displacement motor or drilling tool, a receiving and transmitting module, a wireless communication sub, and a non-magnetic drill collar which are connected in sequence. The multi-parameter acquisition and signal transmission sub is provided with the near-bit measuring instrument. The receiving and transmitting module is configured to receive signals from the near-bit measuring instrument and transmit the signals to the wireless communication sub. The wireless communication sub is configured to transmit the received signals to the ground device through a mud pulse generator in a form of pulse signal, and the ground device decodes and analyzes downhole data. The system can monitor and adjust the real-time changes of downhole engineering parameters timely.

A near-bit multi-parameter downhole measurement and control system while drilling, including a ground device and a downhole assembly. The downhole assembly includes a drill bit, a multi-parameter acquisition and signal transmission sub, a positive displacement motor or drilling tool, a receiving and transmitting module, a wireless communication sub, and a non-magnetic drill collar which are connected in sequence. The multi-parameter acquisition and signal transmission sub is provided with the near-bit measuring instrument. The receiving and transmitting module is configured to receive signals from the near-bit measuring instrument and transmit the signals to the wireless communication sub. The wireless communication sub is configured to transmit the received signals to the ground device through a mud pulse generator in a form of pulse signal, and the ground device decodes and analyzes downhole data. The system can monitor and adjust the real-time changes of downhole engineering parameters timely.

A pulser for generating pressure pulses propagating through a column of drilling fluid in the drill string to the surface during drilling. The pulser may include a screen in the surface of a tubular housing to permit mud from the mud stream to enter into the pulser; an adjustable servo valve configured to receive the mud and including a removable servo poppet and a removable servo orifice member positioned in the tubular housing, wherein the adjustable servo valve is configured to allow the removable servo poppet and the removable servo orifice member to be replaced by another removable servo poppet and another removable servo orifice member to alter an inner diameter of an orifice of the adjustable servo valve to accommodate drilling conditions to increase a performance of the pulser generating pressure pulses for the mud stream returning to the surface.

Systems and methods for generating pulses in a drilling fluid are described. The systems are configured to be positioned along a tubular string through which a drilling fluid flows. The systems include a housing supported along the string. A valve stator is supported by the housing and has at least one flow path that extends from an upstream end to a downstream end of the valve stator. A valve rotor is positioned adjacent the valve stator and configured to selectively obstruct the at least one flow path. An axial gap is present between the valve rotor and the valve stator. A motor is coupled to the valve rotor to rotate the valve rotor relative to the valve stator and an axial release assembly having a rotational element is configured to adjust the axial gap between the valve rotor and the valve stator based on a rotation of the rotational element.