A transmitter antenna assembly for transient electromagnetic well logging instrument comprises an antenna coil coupled with a current source and a magnetic core having residual magnetization. Switching current in the antenna coil results in magnetization reversal in the magnetic core and change in magnetic dipole moment of the antenna. After the magnetization reversal is complete the current is removed and the new vector of magnetic dipole of the antenna maintains constant (steady-state phase of the antenna dipole) due to magnetic hysteresis of magnetic material employed for the magnetic core. No power expenditure during the steady-state phase of the magnetic dipole facilitates highly effective generation and fast switching of a large magnetic dipole. The magnetic core also serves as a shield between the antenna coil and any conductive part of the antenna assembly. Embodiments suitable for measurement-while-drilling or measurements through casing make use of residual magnetization of magnetic drill collar or magnetic casing respectively.

Method and apparatus of using magnetic material with residual magnetization in transient electromagnetic measurement

An electromagnetic flow meter and method of operating the same. There is provided a flow measurement duct, a magnetic circuit including pole pieces for generating a magnetic field in fluid flowing in a direction in the duct across the direction of flow, and an electrical circuit including at least one sensing electrode for measuring a voltage thereby induced in the fluid to provide an output indicative of the flow. The method comprises measuring a series of pairs of outputs of the electrical circuit, each pair of outputs comprising an output when the magnetic field is present and an output when the magnetic field is absent, and determining from the measured series of pairs of outputs whether fluid is present or absent in the duct.

Electromagnetic flowmeter having low power consumption

Sensors for measuring the flow rate of fluids flowing through or around a chamber The chamber is formed using electrically insulating material through which there is an orthogonal alternating magnetic field provided by a mechanically repositioned permanent magnet and at least a pair of electrodes in line with and orthogonal to the magnetic field This provides an electrical potential with a magnitude proportional to flow rate The alternating magnetic field may also be provided by a stationary multiple electromagnet Various embodiments are disclosed which make use of electromagnetics, stepper motors and other modifications for adapting the flow sensor to a wide variety of applications and environmental conditions

Magnetic flow sensor

An apparatus for determining a distance between a first borehole and a second borehole is provided that in one embodiment includes a rotating magnet on a tool configured for placement in the second borehole for inducing magnetization in a magnetic object in the first borehole, a first coil and a second coil placed radially symmetrically with respect to an axis of the tool, the first coil providing a first signal and second coil providing a second signal responsive to a magnetic flux resulting from the magnetization in the magnetic object in the first borehole, and a controller configured to combine the first signal and the second signal and determining distance between the first borehole and the second borehole using the combined signal.

Method and apparatus for well-bore proximity measurement while drilling

PURPOSE:To form a transmission path between a detecting portion and a converting portion into a single system being a flow signal transmission path, by transmitting a flow signal, which is overlapped with a synchronous signal serving as a trigger, from the detecting portion to the converting portion. CONSTITUTION:An exciting power source oscillating part 14 in a detecting part 10 is controlled by a timing signal generating part 16, and generates an exciting signal such as rectangular wave whose polarity reverses at intervals of a given time. In an overlapping part 17, the exciting signal is overlapped with a synchronous signal, and with a coil 2 excited, a flow signal is fetched from electrodes 13a and 13b of a conduit 11. The flow signal is transferred to a converting part 20 through a transmission path 30, and a converting flow signal, synchronizing with the detecting part 10 and being sampled, is outputted through a sampling gate 23 controlled by means of a sampling signal, a trigger of which an overlapping synchronous signal from a sampling signal generating part 22 serves as. As a result, a transmission path 30 between the detecting part 10 and the converting part 20 can be formed into a single system being a transmission path of a flow signal from the detecting part 10, and the converting part can be installed at a remote place without a trouble.

Electromagnetic flow meter

An electromagnetic flow meter with less power consumption in which an instantaneous pulsate current with alternately changing polarity at given intervals is fed into an exciting coil, and a velocity of flow of fluid is calculated by using a voltage produced between electrodes in accordance with a residual magnetic flux of a magnetic circuit and a flow velocity of the fluid when no exciting current flows.

Kazuo Ueno

Papers

Electromagnetic flow meter