Abstract: NMR data are acquired with variable spacing between refocusing pulses, giving data with a variable interecho time TE. Under certain conditions, diffusion effects can be neglected and data acquired with a multiple TE spacing may be used to obtain a T2 distribution with increased resolution and reduced power requirements. In gas reservoirs, the maximum TE may be determined from diffusion considerations using a dual wait time pulse sequence and this maximum TE is used to acquire data with dual TE.

Abstract: NMR data are acquired with variable spacing between refocusing pulses, giving data with a variable interecho time TE. Under certain conditions, diffusion effects can be neglected and data acquired with a multiple TE spacing may be used to obtain a T2 distribution with increased resolution and reduced power requirements. In gas reservoirs, the maximum TE may be determined from diffusion considerations using a dual wait time pulse sequence and this maximum TE is used to acquire data with dual TE. By proper selection of TE, echos can be obtained with significantly reduced ringing.

Abstract: A slotted NMR antenna cover for improved mechanical ruggedness during transmission and reception of NMR signals in a down hole environment during either MWD or wire line operations. A NMR slotted antenna cover is provided comprising an elongated tubular structure with longitudinal gaps or slots filled with a RF transmissive or non-conductive material. The slots can befilled at the slot ends with soft magnetic material to improve efficiency of the antenna. The slots are radial concave to reduce eddy currents induced by alternating magnetic flux entering and leaving the slots surrounding the antenna. In another embodiment, the antenna cover is RF transmissive on only a portion of the antenna, via slots or transmissive material, so that the antenna cover can be used to allow RF transmission from the antenna in a side looking or beam pattern restricted mode only.

Abstract: A loop-gap resonator for providing an excitation pulse in a down hole nuclear magnetic resonating (NMR) tool for determining a parameter of interest in a formation adjacent a borehole. The loop-gap resonator is constructed having one or more capacitive gaps formed in a nonmagnetic conductive loop. The loop-gap resonator may be deployed down a bore in a measurement while drilling (MWD) configuration or in a wire line configuration. The MWD configuration may utilize a non-rotating sleeve rotationally associated with the drill string.

Abstract: The excitation and/or refocusing pulses used in a CPMG sequence have a nonlinear phase and an envelope with no zero crossings and a corresponding frequency spectrum with sidelobes suppressed. As a result of this, peak power requirements are reduced. Pulse shaping is used for reducing the peak power requirements of a NMR logging tool.

Abstract: The present invention provides a novel use of a material having a high internal magnetostrictive damping and/ or using material with explicitly low magnetostriction as a NMR probe core material. The probe structural geometry facilitates the use of material, which has a relatively low magnetic permeability.

Abstract: NMR data are acquired with variable spacing between refocusing pulses, giving data with a variable interecho time TE. Under certain conditions, diffusion effects can be neglected and data acquired with a multiple TE spacing may be used to obtain a T2 distribution with increased resolution and reduced power requirements. In gas reservoirs, the maximum TE may be determined from diffusion considerations using a dual wait time pulse sequence and this maximum TE is used to acquire data with dual TE. By proper selection of TE, echos can be obtained with significantly reduced ringing.

Abstract: NMR data are acquired with variable spacing between refocusing pulses, giving data with a variable interecho time TE. Under certain conditions, diffusion effects can be neglected and data acquired with a multiple TE spacing may be used to obtain a T2 distribution with increased resolution and reduced power requirements. In gas reservoirs, the maximum TE may be determined from diffusion considerations using a dual wait time pulse sequence and this maximum TE is used to acquire data with dual TE.

Abstract: A NMR device is presented that includes a drill collar having non-rotating sleeve containing permanent magnets. The non-rotating sleeve is clamped against a borehole wall and decoupled from drilling vibrations during NMR measurements. The transmitter and receiver are located on the rotating part of the drill collar. Alternatively the permanent magnets and the RF receiver antenna and/or receiver electronics are placed on the non-rotating sleeve which is clamped against the borehole wall and decoupled from drilling vibrations, with the transmitting antenna located on the rotating drill collar. Alternatively a non-rotating stabilizer is provided above or below a NMR sensor. A stabilizer is activated to stabilize the rotating NMR sensor located on the drilling collar in the bore hole.

Abstract: A method of detecting the presence of a particular substance in a given sample. According to the method, nuclear resonance is excited in a substance and response signals are detected from the substance using a probe. The probe is adjusted in dependence on the character of the sample. A method of detecting the presence of a sample which gives rise to interfering signals, not due to nuclear resonance, comprises exciting nuclear resonance in the sample, and detecting and processing the response signal from the sample in such a way as to at least partially filter out the interfering signals arising from the sample.

Abstract: A method of Nuclear Quadrupole Resonance testing a sample containing a given species of quadrupolar nucleus, the sample being subjected to an inhomogeneous distribution of an extrinsic parameter having a variation over the sample over a particular range, comprises applying excitation to the sample at a plurality of different excitation frequencies to excite nuclear quadrupole resonance, such frequencies falling within the resonance frequency range for the nucleus corresponding to the range of the extrinsic parameter, and detecting the resonance response signal.

Abstract: A method of Nuclear Quadrupole Resonance testing a sample containing a given species of quadrupolar nucleus, the sample being subjected to an inhomogeneous distribution of an extrinsic parameter having a variation over the sample over a particular range, comprises applying excitation to the sample at a plurality of different excitation frequencies to excite nuclear quadrupole resonance, such frequencies falling within the resonance frequency range for the nucleus corresponding to the range of the extrinsic parameter, and detecting the resonance response signal.

Abstract: Apparatus for Nuclear Quadrupole Resonance testing a sample comprises: means for applying excitation to the sample to excite NQR resonance, the excitation comprising at least one excitation pulse, the or each pulse covering a selected excitation frequency range, for the or each pulse the phase of the excitation varying generally non-linearly with the excitation frequency over the selected range; and means for detecting the NQR response signal.

Abstract: A method and apparatus for imaging within a sample space an object containing quadrupolar nuclei comprises irradiating the object to excite nuclear quadrupole resonance, applying to the object a magnetic field gradient having a profile Bo(x) such that the square of the profile Bo(x))2 varies linearly with distance (x), detecting resonance response signals from the nuclei, and deriving an image from the response signals. A method of and apparatus for nuclear quadrupole resonance testing an object, and a method of and apparatus for detecting the presence of a particular substance containing a given species of quadrupolar nucleus, are also disclosed.

Abstract: A variable temperature NMR probe having a RF coil surrounding a sample position and a fluid jacket for conveying fluid to control the temperature at the sample position. An RF electromagnetic shield prevents fluid in a fluid conveyor from affecting a NMR signal from the sample position.