Abstract: An NMR measurement apparatus is potentially subject to relative motion between the apparatus and a sample. The measurement apparatus includes at least one magnet, at least one coil and circuitry that is coupled to the magnet(s) and coil(s). The circuitry is adapted to use the magnet(s) and coil(s) to perform at least one NMR measurement and indicate the results of the NMR measurement(s). The results are then analyzed to determine an effect of the motion on the measurement(s).

Abstract: A permeability estimation technique for use with spin echo signals that are received from a sample includes summing indications of the amplitudes of the spin echo signals. The results of the summing are used to determine an indication of a permeability of the sample, without using a distribution of relaxation times in the determination. The products of indications of the amplitudes of the spin echo signals may be summed, and the results of the summing may be used to determine an indication of a permeability of the sample, without using a distribution of relaxation times in the determination.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: Systems and methods for determining characteristics of geologic formations between conductively lined wellbores. At least one transmitter is axially disposed at a selected depth in a first wellbore and is attached to an external surface of a conductive liner. At least one receiver is axially disposed at a selected depth in a second wellbore and is attached to an external surface of a conductive liner. Both the transmitter and the receiver are attached to a surface control station. The transmitter generates a first magnetic field, and a formation magnetic field induced by the first magnetic field is detected by the receiver. The detected formation magnetic field is used to determine characteristics of the geologic formations.

Abstract: Apparatus and methods are described for isolating in a drillstring a device from acoustic noise by introducing between the device and a source of acoustic vibration an noise isolating apparatus, wherein the noise isolating apparatus has adjacent zones of different acoustic impedance. The zones are preferably created by zones of different thickness and designed such that noise suppression occurs in a predetermined range of acoustic frequencies. In a preferred application the apparatus and method is used in combination with drillstring telemetry.

Abstract: The present invention provides methods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: The present invention provides met hods and apparatus for determining flow velocity within a formation utilizing nuclear magnetic resonance (NMR) techniques in which the shape of the resonance region is restricted so that sensitivity to radial flow or vertical flow is obtained (or both when more than one NMR tool is used). Flow velocity using these NMR tools is determined using decay amplitude, frequency displacement or stimulated echoes (where the spins are stored along the magnetic field instead of the transverse plane to exploit echo decays and frequency displacements) based on the application of adiabatic pulses. Based on the described NMR measurement of flow velocity, additional wellbore parameters may be obtained such as a direct measurement of permeability, an assessment of drilling damage to the wellbore, formation pressure, invasion rate of the mud filtrate or the migration of fine mud particles during sampling operations.

Abstract: A downhole NMR measurement apparatus for use in a borehole includes at least one magnet, at least one RF transmission coil, at least one gradient coil and circuitry. The magnet(s) establish a magnetic field in a region of a formation that at least partially surrounds the measurement apparatus. The RF transmission coils(s) transmit RF pulses pursuant to an NMR pulse sequence into the region to, in combination with the magnetic field, induce the generation of spin echo signals from a resonance volume within the region. The gradient coil(s) establish a pulsed gradient field in the resonance volume, and the circuitry is coupled to the gradient coil(s) to control the generation of the pulsed gradient field to phase encode the spin echo signals for purposes of high resolution imaging of the formation.

Abstract: A method for performing phase encoded inside-out magnetic resonance imaging. The phase of the nuclear spin is advanced by applying a magnetic field gradient between application of each of several refocusing pulse sequences so that echoes are detected during refocusing pulse sequences for different phase advances. The echoes detected for each refocusing sequence are added together and averaged. An image is then generated from the averaged echoes, such as by Fourier transform techniques. In addition, a method is provided for eliminating ringing while measuring a nuclear magnetic resonance property of a volume of earth formation surrounding a borehole. The phase of the refocusing pulses is changed so that pairs of echoes in the echo train have opposite ringing phase. Echoes in the echo train having opposite ringing phase are added to cancel ringing in the echo train. The echo train can then be analyzed for amplitude and/or decay characteristics.

Abstract: A method for reducing ringing in nuclear magnetic resonance measurements is disclosed. The method includes inducing a static magnetic field in a sensitive volume to orient nuclear magnetic spins of nuclei in the sensitive volume. The nuclear spins are reoriented by a first selected angle. An amplitude of the static magnetic field is then adjusted to cause a first selected phase shift in a spin echo signal measured subsequently to the reorienting by the first angle. The spins are then reoriented by a second selected angle, and a first spin echo signal is detected. After a selected wait time, reorienting by the first selected angle is repeated. Adjusting the amplitude of the static magnetic field is then repeated to cause a second selected phase shift in a subsequently measured spin echo. The first and second selected phase shifts have a difference between them of an odd numbered multiple of 180 degrees. Reorienting by the second selected and detecting a second spin echo signal are then repeated.

Abstract: A magnet assembly for nuclear magnetic well logging apparatus includes two diametrically opposed magnets which produce a static and substantially homogeneous magnetic field. Each magnet has a magnet axis and is partitioned into a first and a second magnet segment by a plane substantially parallel to the magnet axis.