Abstract: A method of determining the dielectric constant of a formation, comprising acquiring phase-related and amplitude-related measurements for electromagnetic signals propagating though the formation from a transmitter to a receiver; deriving a complex-valued quantity comprising terms relating to the phase shift and attenuation of the signals; defining a one-component complex-valued relationship relating the phase shift, attenuation and complex dielectric constant; and using the derived complex-valued quantity in the defined relationship to obtain a calculated value of the complex dielectric constant. An apparatus for determining the dielectric constant of a formation, comprises a transmitter for transmitting electromagnetic signals into the formation; a receiver for receiving the electromagnetic signals that have propagated from the transmitter through the formation; and means for determining the dielectric constant of the formation in accordance with a method according to the first aspect of the invention.

Abstract: The invention provides a method of receiving and/or transmitting information in a well drilled in a geological formation between a first location and a second location, the well comprising a casing communicating with the geological formation. The method comprises placing a first transducer at a first location, placing a second transducer at a second location. Transmitting an electric signal between the first and second transducers.

Abstract: A method of inverting induction logging data for evaluating the properties of underground formations surrounding a borehole, the data including induction voltage measurements obtained from a tool placed close to the formations of interest, the method includes: (a) defining a relationship relating the induction voltage to wave number, dielectric permittivity and conductivity; defining a cubic polynomial expansion of the relationship; and solving the cubic polynomial relationship using the voltage measurements to obtain values for conductivity that includes skin-effect correction, and apparent dielectric permittivity; and (b) using the obtained values for conductivity and apparent dielectric permittivity to derive a simulated value of induction voltage; determining the difference between the simulated value of the induction voltage and the measured induction voltage; and iteratively updating the values of conductivity and dielectric permittivity used for the derivation of the simulated value of induction voltag

Abstract: The invention provides a method of receiving and/or transmitting information in a well drilled in a geological formation between a first location and a second location, the well comprising a casing communicating with the geological formation. The method comprises placing a first transducer at a first location, placing a second transducer at a second location. Transmitting an electric signal between the first and second transducers.

Abstract: A gamma-ray detector comprising: a housing having a window through which gamma rays can enter; the housing comprising; a two-dimensional array of electrically conducting carbon nanotubes, which act as a cathode, on a substrate; a metal plate electrode, which acts as an anode, positioned opposite the substrate so that there is a gap containing a gas between the electrode and the nanotubes; and a voltage source connected to the substrate and the electrode such that when in use the voltage between the substrate and the electrode is maintained below the arc-threshold voltage so that no electric current can flow through the gap between the nanotubes and the electrode; wherein the electrode and the substrate are arranged such that when a gamma ray enters the housing and hits one of the nanotubes a spark discharge is triggered between the nanotubes and the plate electrode creating an electrical current that can be measured.

Abstract: A method of inverting induction logging data for evaluating the properties of underground formations surrounding a borehole, the data comprising induction voltage measurements obtained from a tool placed close to the formations of interest, the method comprises: (a) defining a relationship relating the induction voltage to wave number, dielectric permittivity and conductivity; defining a cubic polynomial expansion of the relationship; and solving the cubic polynomial relationship using the voltage measurements to obtain values for conductivity that includes skin-effect correction, and apparent dielectric permittivity; and (b) using the obtained values for conductivity and apparent dielectric permittivity to derive a simulated value of induction voltage; determining the difference between the simulated value of the induction voltage and the measured induction voltage; and iteratively updating the values of conductivity and dielectric permittivity used for the derivation of the simulated value of induction volt

Abstract: A gamma-ray detector comprising: a housing having a window through which gamma rays can enter; the housing comprising; a two-dimensional array of electrically conducting carbon nanotubes, which act as a cathode, on a substrate; a metal plate electrode, which acts as an anode, positioned opposite the substrate so that there is a gap containing a gas between the electrode and the nanotubes; and a voltage source connected to the substrate and the electrode such that when in use the voltage between the substrate and the electrode is maintained below the arc-threshold voltage so that no electric current can flow through the gap between the nanotubes and the electrode; wherein the electrode and the substrate are arranged such that when a gamma ray enters the housing and hits one of the nanotubes a spark discharge is triggered between the nanotubes and the plate electrode creating an electrical current that can be measured.

Abstract: A borehole tool, comprises: a tool body; a series of arms connected to the tool body and moveable radially relative thereto; and a series of pads mounted on the arms so as to be pivotable about a radial axis relative to the tool body. By allowing pivoting of the pads about a radial axis, elongate pads can be arranged to provide different circumferential coverage according to the orientation with respect to the longitudinal axis of the borehole.

Abstract: The present invention provides methods and systems for numerically computing tool response sensitivities of subterranean measurement tools such as resistivity logging tools. The methods and systems enable much faster computation of sensitivities than previously available for resistivity tools. For typical tools that apply dozens or hundreds of parameters, the methods of the present invention may reduce sensitivities computation time by a factor substantially equal to the number of parameters.

Abstract: A borehole tool, comprises: a tool body; a series of arms connected to the tool body and moveable radially relative thereto; and a series of pads mounted on the arms so as to be pivotable about a radial axis relative to the tool body. By allowing pivoting of the pads about a radial axis, elongate pads can be arranged to provide different circumferential coverage according to the orientation with respect to the longitudinal axis of the borehole.

Abstract: A method of determining alignment of first and second parts of a borehole tool system in which three mutually orthogonal signals are transmitted by a transmitter in the first tool part and each signal is received and measured in three mutually orthogonal directions at a receiver in the second tool part, the components of each signal in the three mutually orthogonal directions at the receiver being used to determine the alignment of the first and second parts. The method has applications in deep electromagnetic or acoustic measurements, either from a single well or in a cross-well system.

Abstract: A logging-while-drilling system is disclosed in which a first subassembly is included near the drill bit, and this subassembly comprises a conducting body with measuring means disposed in it and a first toroidal coil antenna disposed on the body, means for coupling a local communication signal generated from the measuring means to the first toroidal coil antenna, and where the measuring means includes means to energize the first toroidal coil antenna with a measurement signal and means mounted on the conductive body to receive the measurement signal after it passes through the formations to be measured.

Abstract: Measurement-while-drilling apparatus is disclosed for determining the resistivity of formations surrounding an earth borehole. An electrically conductive metal body, such as a drill collar on a drill string, is movable through the borehole. A transmitting toroidal coil antenna is disposed on the body and is energized to induce a current which travels in a path that includes the body and the formations. An electrode is disposed on the body, and an electrical signal resulting from said current is measured at the electrode to obtain an indication of the resistivity of the formations. In a disclosed embodiment, one or more electrodes can be mounted on a blade that is mechanically coupled to the body.

Abstract: The disclosed method is applicable for use in conjunction with an earth borehole drilling apparatus that typically includes: a drilling rig; and a drill string operating from said drilling rig for drilling an earth borehole, the drill string including a bottom hole arrangement comprising a drill bit and a downhole resistivity measuring subsystem for measuring downhole formation resistivity near the bit by propagating electromagnetic energy into earth formations near the bit, receiving electromagnetic energy that has propagated through the formations and producing measurement signals that depend on the received signals.

Abstract: Apparatus is disclosed for determining the resistivity of formations surrounding an earth borehole. An electrically conductive metal body, such as a drill collar on a drill string, is movable through the borehole. A transmitting toroidal coil antenna is disposed on the body and is energized to induce a current which travels in a path that includes the body and the formations. An electrode is disposed on the body, and an electrical signal resulting from said current is measured at the electrode to obtain an indication of the resistivity of the formations. In a disclosed embodiment, one or more electrodes can be mounted on a blade that is mechanically coupled to the body.

Abstract: A disclosed embodiment utilizes one or more toroidal coil antennas mounted, in an insulating medium, on a drill collar to induce currents which travel in a path that includes the drill collar and earth formations around the drill collar. At least one array of electrodes is provided on at least one stabilizer blade of the drill collar and is utilized to detect currents transmitted by toroidal coil antennas which return via the formations to the electrodes laterally; that is, approximately normal to the axis of the drill collar. Signal traces are obtained from measurements taken at respective ones of the transducers, and a dip characteristic of the formations is determined from the signal traces and from signals representing the rotational orientation of the drill collar.

Abstract: Well logging techniques and apparatus are disclosed for determining formation resistivity at different radial depths of investigation and with greater accuracy than prior techniques, for determining the existence, locations and properties of beds and caves, and for determining changes in the size of a borehole.

Abstract: A well logging apparatus is disclosed including a cylindrical housing with a transmitting antenna and first and second receiving antennas. The antennas are formed on insulating material in recesses in the housing and have a waterproof rubber covering. The receiving antennas have adjacent compartments containing signal conditioning circuits.

Abstract: Well logging techniques and apparatus are disclosed for determining formation resistivity at different radial depths of investigation and with greater accuracy than prior techniques, for determining the existence, locations and properties of beds and caves, and for determining changes in the size of a borehole.