Abstract: An improved total field calibration system and method is disclosed for reducing the rotational misalignment between magnetic and gravity sensors in a directional sensing system. The effect of variation of surface components of the Earth's magnetic field during the calibration process on magnetometer misalignment may be completely eliminated by requiring the magnetic dip derived from the sensing system to match that of the Earth's field obtained from a reference source. The calibration process can be performed without monitoring the declination change during the calibration process. Directional sensing systems can be calibrated accurately during a period when the Earth's magnetic field changes rapidly.

Abstract: A converter with adjustable output voltage is coupled to a first power source and a second power source. The converter comprises a transformer, a first conversion circuit, a second conversion circuit, a resonant circuit and a regulating circuit. The first conversion circuit has a plurality of first switch elements, each of the first switch elements is coupled to the transformer. The second conversion circuit has a plurality of second switch elements, and each of the second switch elements is coupled to the transformer. The resonant circuit comprises a first inductor, at least one first capacitor and a second inductor. The first inductor is coupled in series to the transformer, and the first capacitor is coupled in parallel to the second conversion circuit. The second inductor is coupled to the first capacitor. The regulating circuit is coupled between the second power source and the second conversion circuit.

Abstract: A steerable or non-steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resistivity in a particular azimuthal direction.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: An electromagnetic antenna for Measurement-While-Drilling (MWD) applications is disclosed. The antenna can include several array elements that can act alone or together in various measurement modes. The antenna elements can be disposed in tool body recesses to be protected from damage. The antenna elements can include a ferrite plate crossed or looped by independent current carrying conductors in two or more directions forming a bi-directional or crossed magnetic dipole. Although disclosed as a MWD system conveyed by a drill string, basic concepts of the system are applicable to other types of borehole conveyance.

Abstract: A drive circuit comprising: a direct current power source; a control unit for supplying control signals; a power switch topology comprising a first switch and a second switch each having an input terminal, an output terminal, and a control terminal, the input terminals being respectively connected to the power source, the control terminals being connected to the control unit for receiving the control signals there from, the output terminals being connected to a node; and an inductance connected with a capacitive load in series between the node and the power source, wherein the control signals control the switches to alternately conduct to thereby cause the node to output a pulse signal.

Abstract: A steerable or non-steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resitivity in a particular azimuthal direction.

Abstract: A steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna.

Abstract: A steerable or non-steerable, magnetic dipole antenna for Measurement-While-Drilling (MWD) or Logging-While-Drilling (LWD) applications. The antenna elements use a hole arrangement in addition to grooves in a steel tool body, which is typically a drill collar. This antenna embodiment is extremely robust, meaning that does not significantly reduce the structural integrity of the tool body in which it is disposed. The antenna embodiment is also relatively wear resistant. The resultant magnetic dipole generated by this antenna is also electrically steerable in inclination angle from a common origin. A variable dipole moment inclination angle combined with independently measured tool rotation orientation during normal drilling allows the antenna to generate a magnetic dipole moment that may be directed at any three dimensional angle and from a common origin point at the centroid of the antenna. The antenna can also be embodied to be more sensitive to resistivity in a particular azimuthal direction.

Abstract: A drive circuit comprising: a direct current power source; a control unit for supplying control signals; a power switch topology comprising a first switch and a second switch each having an input terminal, an output terminal, and a control terminal, the input terminals being respectively connected to the power source, the control terminals being connected to the control unit for receiving the control signals there from, the output terminals being connected to a node; and an inductance connected with a capacitive load in series between the node and the power source, wherein the control signals control the switches to alternately conduct to thereby cause the node to output a pulse signal.

Abstract: An electromagnetic antenna for Measurement-While-Drilling (MWD) applications is disclosed. The antenna can include several array elements that can act alone or together in various measurement modes. The antenna elements can be disposed in tool body recesses to be protected from damage. The antenna elements can include a ferrite plate crossed or looped by independent current carrying conductors in two or more directions forming a bi-directional or crossed magnetic dipole. Although disclosed as a MWD system conveyed by a drill string, basic concepts of the system are applicable to other types of borehole conveyance.

Abstract: Method and apparatus for optimizing mud pulse telemetry data rate by processing a sequence of measured pulses to minimize adverse effects of pressure pulse reflections, attenuations and distortions. A downhole telemetry unit cooperating with a sensor and disposed in a MWD or LWD logging tool generates a sequence of pulse within the mud column. The sequence is encoder to represent the response of the sensor disposed within the logging tool. The encoded pulse sequence is sensed at the surface of the earth using a pressure transducer. The output of the transducer yields an electrical signal that is typically attenuated and can contain reflections and distortions. This measured signal output is processed to minimize the effects of pulse reflections, attenuations and distortions thereby yielding a primary pulse sequence that is more representative of the response of the sensor and allowing an increase in mud pulse telemetry data rate.

Abstract: A directional sensor system that incorporates a single axis sensor element that is manipulated to a plurality of orientations. The resulting responses of the sensor element at these locations are combined to obtain a measure of orientation of the system. The system applicable for determining orientation of instrumentation within a well borehole such as measurement-while-drilling, wireline and tubing conveyed borehole instrumentation. The system can be used in other subsurface and surface applications.

Abstract: A directional sensor system that incorporates a single axis sensor element that is manipulated to a plurality of orientations. The resulting responses of the sensor element at these locations are combined to obtain a measure of orientation of the system. The system applicable for determining orientation of instrumentation within a well borehole such as measurement-while-drilling, wireline and tubing conveyed borehole instrumentation. The system can be used in other subsurface and surface applications.

Abstract: A method and apparatus is disclosed for improving the accuracy of directional surveys using magnetometers and accelerometers. The method corrects errors in bias, scale-factor, misalignment of cross-axial magnetometers, and bias or scale-factor of axial magnetometer by requiring the magnitude of measured cross-axial magnetic field to be as constant as possible over several tool face angles at a survey point in a wellbore and the magnitude of the measured total magnetic field and dip angle equal to the reference values, respectively. The axial component of the measured magnetic field is also determined. The method also corrects accelerometers similarly. The calibration parameters obtained at one survey point are applied to measurements at other survey points to improve the accuracy of surveys and the efficiency of drilling operations.

Abstract: A method and apparatus is disclosed for improving the accuracy of directional surveys using magnetometers and accelerometers. The method corrects errors in bias, scale-factor, misalignment of cross-axial magnetometers, and bias or scale-factor of axial magnetometer by requiring the magnitude of measured cross-axial magnetic field to be as constant as possible over several tool face angles at a survey point in a wellbore and the magnitude of the measured total magnetic field and dip angle equal to the reference values, respectively. The axial component of the measured magnetic field is also determined. The method also corrects accelerometers similarly. The calibration parameters obtained at one survey point are applied to measurements at other survey points to improve the accuracy of surveys and the efficiency of drilling operations.

Abstract: An electromagnetic wave propagation resistivity borehole logging system comprising multiple groups of electromagnetic transmitter-receiver arrays operating at three frequencies. The borehole logging tool component of the system employs eight transmitters and four receivers. The transmitters and receivers are disposed axially and symmetrically along the major axis of the tool to form four group pairs. Each group pair consists of a transmitter-receiver groups axially and symmetrically on opposing sides of a reference point on the tool. Each, transmitter-receiver group consists of one transmitter assembly and two receiver assemblies. Each transmitter-receiver group is operated at two of three operating frequencies which are 100 kHz, 400 kHz and 2 MHz. The transmitter and receiver assemblies are fabricated to yield azimuthally symmetrical resistivity measurements in a plane essentially perpendicular to the axis of the tool.

Abstract: The present invention provides a new and unique method, sensor, and apparatus for performing a seismic survey of an earth formation in relation to a borehole. The method includes arranging at least one strain seismic sensor in conjunction with a borehole structure, and mechanically coupling the borehole structure to the borehole to allow seismic data to be accurately transferred to the sensor. The sensor is preferably a fiber optic sensor, including a Fiber Bragg Grating which may be coupled to a relevant borehole structure in a number of ways.

Abstract: An electromagnetic wave propagation resistivity borehole logging system comprising multiple groups of electromagnetic transmitter-receiver arrays operating at three frequencies. The borehole logging tool component of the system employs eight transmitters and four receivers. The transmitters and receivers are disposed axially and symmetrically along the major axis of the tool to form four group pairs. Each group pair consists of a transmitter-receiver groups axially and symmetrically on opposing sides of a reference point on the tool. Each, transmitter-receiver group consists of one transmitter assembly and two receiver assemblies. Each transmitter-receiver group is operated at two of three operating frequencies which are 100 kHz, 400 kHz and 2 MHz. The transmitter and receiver assemblies are fabricated to yield azimuthally symmetrical resistivity measurements in a plane essentially perpendicular to the axis of the tool.