Abstract: A method and apparatus for performing NMR measurements suppressing contribution to NMR signals from within the borehole. Within the region of examination, the RF magnetic field has a spatially varying intensity. NMR signals (free induction decay or spin echo signals) are inverted to give spin density as a function of field intensity. This inversion is then mapped to spatial positions using the known RF field variation. The effect of signals arising from within the borehole can be suppressed. It is also possible to obtain an azimuthal image of the spin density.

Abstract: A method for manufacturing NMR measurement-while-drilling tool having the mechanical strength and measurement sensitivity to perform NMR measurements of an earth formation while drilling a borehole, and a method and apparatus for monitoring the motion of the measuring tool in order to take this motion into account when processing NMR signals from the borehole. The tool has a permanent magnet with a magnetic field direction substantially perpendicular to the axis of the borehole, a steel collar of a non-magnetic material surrounding the magnet, antenna positioned outside the collar, and a soft magnetic material positioned in a predetermined relationship with the collar and the magnet that helps to shape the magnetic field of the tool. Due to the non-magnetic collar, the tool can withstand the extreme conditions in the borehole environment while the borehole is being drilled.

Abstract: An apparatus and method is discussed for characterizing a fluid sample downhole of aliphatic hydrocarbon compounds, aromatic hydrocarbon compound, or connate mud filtrates containing carbon-13 isotopes using an enhanced nuclear magnetic resonance (NMR) signal on a measurement-while-drilling device. To enhance the carbon-13 NMR signal these nuclei are being hyperpolarized. Either the Overhauser Effect (OE) or the Nuclear Overhauser Effect or optical pumping and the Spin Polarization Induced Nuclear Overhauser Effect (SPINOE) can serve as a mechanism for hyperpolarization of the carbon-13 nuclei.

Abstract: An NMR probe comprises a resonator formed of two separate conducting loops disposed on opposite sides of the sample, where one loop is driven and the other floats in a preferred operating mode. Slotted shields are disposed coaxially within said loops and outside the sample with slots aligned with gaps between the loops.

Abstract: Apparatus and method for providing in-situ data of formation fluids at true reservoir conditions. The apparatus has NMR chamber of the flow-through type, so it is no longer necessary to divert a sample for the basic NMR analysis or transfer it uphole for laboratory analysis. The apparatus is preferably modular and is compatible with wireline tools configurable for a variety of sampling, testing and monitoring purposes. Fluid properties such as viscosity can be derived from diffusivities and relaxation times, as measured by NMR. Additional accuracy is provided in the downhole sampling process, and in the interpretation of NMR logs in real time at true reservoir conditions.

Abstract: An expert system is included in a downhole processor designed to acquire and process NMR data downhole in real time. The downhole processor controls the acquisition of the NMR data based at least in part on instructions transmitted downhole from a surface location and at least in part on evaluation of downhole conditions by the expert system. The downhole conditions include drilling operation conditions (including motion sensors) as well as lithology and fluid content of the formation obtained from other MWD data. The wait time, number of echos, number of repetitions of an echo sequence, interecho time, bandwidth and shape of the tipping and refocusing pulses may be dynamically changed. Data processing is a combination of standard evaluation techniques. Selected data and diagnostics are transmitted uphole. The expert system may be implemented as a two stage neural net. The first stage does the formation evaluation and the second stage controls the NMR pulse sequence.

Abstract: Wireline NMR well logging measurements suffer from disadvantages of poor vertical resolution, logging speeds less than 20 ft/min, and power consumption in excess of 200 W. In spite of these disadvantages, NMR well logging is used because it is capable of providing estimates for a number of petrophysical parameters that are difficult to obtain from other wireline data. These include estimates of the bulk volume irreducible (BVI) of fluids in the formation. The present invention targets BVI and clay bound water (CBW) measurements. Logging speeds of up to 60 ft/min are attainable with little or no loss of resolution. In one preferred embodiment, the tool has four sensors circumferentially distributed around the logging tool and in contact with the borehole wall. A horseshoe like magnet is used to generate the static magnetic field.

Abstract: A method of reducing ringing artifacts in a nuclear magnetic resonance measurement is provided. The method utilizes a new pulse sequence that offers ringing cancellation opportunities as well as compensation for otherwise accumulating spin dynamics errors. Ringing cancellation is accomplished by forming linear combinations of spin echoes induced as a result of the pulse sequence. Because the linear combinations are formed between closely spaced spin echoes (i.e., echoes within the same sequence), the likelihood that the ringing artifact will have changed between measurements is diminished.

Abstract: A logging while drilling (LWD) and measuring while drilling (MWD) method and device are disclosed for reducing the sensitivity of NMR measurements to tool motions. The invention is based on NMR relaxation measurements determining longitudinal relaxation times T1 instead of the standard T2 measurements, and involves saturating a relatively wide sensitive region of the formation and processing NMR echo signals which originate approximately from the center of the sensitive region. In another aspect, the invention uses novel pulse sequences and processing algorithms to reduce the time for the relaxation measurement and to provide real-time transfer of data uphole.

Abstract: A method for determining an earth formation property from nuclear magnetic resonance measurements includes applying suppression functions to spin echoes in at least one burst measurement set to produce a modified burst data set, the suppression functions to suppress contribution of spin echoes having non-negligible polarization correction; inverting the modified burst data set and at least one standard spin echo measurement set to produce a nuclear magnetic resonance parameter distribution, the at least one standard spin echo measurement set and the at least one burst measurement set being acquired on an earth formation sample; and computing the earth formation property from the nuclear magnetic resonance parameter distribution. The nuclear magnetic resonance parameter includes at least one selected from longitudinal relaxation time, transverse relaxation time, a ratio of longitudinal relaxation time to transverse relaxation time, and diffusion constant.

Abstract: Nuclear magnetic resonance well logging apparatus and method of use for geophysical examination of a borehole as the borehole is drilled. The apparatus is connected to the drill bit to follow it through the borehole as the borehole is formed. The apparatus comprises a non-magnetic protective collar with lateral protrusions or wings, which provide enhanced abrasion resistance, strength, and rigidity to the probe section. This collar is twisted about its longitudinal axis. The apparatus also comprises one or more permanent magnets within the metal collar and an antenna mounted outside of the collar. Both the magnet and the antenna are twisted about the longitudinal axis of the probe section to produce a generally helical static magnetic field and a radio frequency magnetic field that is substantially orthogonal to the static magnetic field.

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: A high vertical resolution antenna design is provided for use in an NMR measurement apparatus. Multiple coils are situated along the length of a magnet. A primary coil is energized to cause an oscillating magnetic field in a portion of earth formation surrounding a borehole. A secondary coil having smaller dimensions than the primary coil is operated to receive spin echoes from a depth of investigation associated with the secondary coil. A distance sufficient to minimize electrical coupling separates the coils. The separation distance can be reduced by selecting a secondary coil with orthogonal polarization to the primary coil. Alternatively, a cross coil configuration can be implemented where the orthogonal secondary coil at least partially overlaps the primary coil, thereby reducing the overall length necessary for the polarizing magnet.

Abstract: The present invention provides a method and apparatus for performing resistivity measurements for the purpose of geo-steering with 180-degree azimuth resolution. All the measurements represent a complementary set of data acquired in two operational modes. The directional mode providing sensitivity of the received signals to the azimuth characteristics of the formation. The deep mode provides a large depth of investigation for resistivity determination and bed boundary detection. The directional mode can be implemented using one receiving coil placed in between quadruple type transmitter. The deep mode represents either array induction measurements or multiple propagation resisitivity (MPR) measurements that provide high depth of investigation for resistivity determination and bed boundary detection.

Abstract: An NMR apparatus includes permanent magnets oppositely polarized in the axial direction and suitably arranged along the axis of the apparatus to produce a nearly radial static magnetic field in a toroidal examination region within the rock formation surrounding the wellbore. A first coil is wound around a cylindrical annulus core coaxial with the magnets, the core including high magnetic permeability material. The first coil produces pulsed RF magnetic fields oriented parallel to the axis of the apparatus and thus perpendicular to the static magnetic field in the toroidal examination region. This reorients certain nuclear spins and the bulk magnetization of the formation within the examination region resulting from them. The first coil picks up on component of the spin-echo signals of the precessing nucleii.

Abstract: A method for detecting hydrocarbon-bearing zones in a formation penetrated by a wellbore includes acquiring at least two nuclear magnetic resonance measurements, each of the at least two nuclear magnetic resonance measurements acquired from a volume of investigation at a different radial depth from the wellbore; and determining whether the formation bears hydrocarbons by comparing the at least two nuclear magnetic resonance measurements. A method for detecting fines invasion in a formation surrounding a wellbore includes acquiring at least two nuclear magnetic resonance measurements, each of the at least two nuclear magnetic resonance measurements acquired from a volume of investigation at a different radial depth from the wellbore; and determining whether the fines invasion has occurred by comparing the at least two nuclear magnetic resonance measurements.

Abstract: A method for determining properties of a mixture of fluids includes: (a) acquiring a plurality of nuclear magnetic resonance measurements from the mixture of fluids, each of the plurality of nuclear magnetic resonance measurements having a different value in an acquisition parameter for which at least one relaxation selected from the group consisting of longitudinal relaxation and transverse relaxation affects magnitudes of the nuclear magnetic resonance measurements; (b) generating a model of the mixture of fluids; (c) calculating a synthesized nuclear magnetic data set based on the model; (d) comparing the synthesized nuclear magnetic data set with the nuclear magnetic resonance measurements; and (e) adjusting the model and repeating (c) and (d), if difference between the synthesized nuclear magnetic data set and the nuclear magnetic measurements is greater than a minimum.

Abstract: A method for evaluating formation fluids includes measuring a nuclear magnetic resonance property related to a total volume of the formation fluids, measuring a dielectric property related to an electromagnetic wave travel time, measuring a bulk density, and solving a set of linear response equations representing a reservoir fluid model to determine fractional fluid volumes from the nuclear magnetic resonance property, the dielectric property, and the bulk density.

Abstract: Stochastic pulsing using random or pseudo-random sequences is used for determination of nuclear spin properties of earth formations. This reduces the power requirements. Processing of the received signals may include linear or nonlinear cross-correlation with the excitation pulse sequence. Inversion of the results of the processing gives the desired nuclear spin property.

Abstract: A method for detecting hydrocarbon-bearing zones in a formation penetrated by a wellbore includes acquiring at least two nuclear magnetic resonance measurements, each of the at least two nuclear magnetic resonance measurements acquired from a volume of investigation at a different radial depth from the wellbore; and determining whether the formation bears hydrocarbons by comparing the at least two nuclear magnetic resonance measurements. A method for detecting fines invasion in a formation surrounding a wellbore includes acquiring at least two nuclear magnetic resonance measurements, each of the at least two nuclear magnetic resonance measurements acquired from a volume of investigation at a different radial depth from the wellbore; and determining whether the fines invasion has occurred by comparing the at least two nuclear magnetic resonance measurements.

Abstract: A method for detecting hydrocarbons in a fluid sample includes deriving a difference measurement from a first nuclear magnetic resonance measurement and a second nuclear magnetic resonance measurement, wherein the first nuclear magnetic resonance measurement and the second nuclear magnetic resonance measurement have difference values in an acquisition parameter such that molecular diffusion affects the first nuclear magnetic resonance measurement and the second nuclear magnetic resonance measurement to a different extent; and determining a presence of hydrocarbons from the difference measurement.

Abstract: A method for acquiring nuclear magnetic resonance measurements of a material uses a modified CPMG sequence with a refocusing pulse having a tipping angle less than 180 °. The results of using the shortened refocusing pulse with reduced power requirements are comparable to those obtained with a conventional CPMG sequence.

Abstract: The distribution of shales, sands and water in a reservoir including laminated shaly sands using vertical and horizontal conductivities is derived from nuclear, NMR, and multi-component induction data. The multicomponent data are inverted and an estimate of the laminated shale volume from this inversion is compared with an estimate of laminated shale volume from nuclear logs. The bulk water volume determined from the inversion is compared with a bulk irreducible water volume from NMR measurements. NMR data are then used to obtain a sand distribution in the reservoir and this sand distribution is used in a second inversion of the multicomponent data. Alternatively, a bulk permeability measurement is used as a constraint in inverting the properties of the anisotropic sand component of the reservoir. From the resistivities of the sand laminae, empirical relations are used to predict anisotropic reservoir properties of the reservoir.

Abstract: Measurements from many logging instruments such as Gamma ray counts from a pulsed neutron instrument, and amplitudes of spin-echo signals from a NMR instrument, typically have a spectrum that contains a plurality of exponentially decaying components. The slowest decaying component is obtained by fitting a single exponential over the tail end of the data and selecting a beginning for the fitting window that minimizes the product of the chi-square and the standard error of the fit. The single determined component may be subtracted from the data and the process repeated to give additional components. The determined components are indicative of thermal neutron capture cross-sections (in the case of a pulsed neutron instrument) and of the distribution of relaxation times and fluids within the pores of a rock in the case of a NMR instrument.

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: An NMR instrument for determining formation fluid properties includes a housing adapted to move in a wellbore; a magnet disposed in the housing adapted to induce a static magnetic field; an antenna assembly disposed in the housing adapted to resonate at a first frequency and a second frequency, the first frequency corresponding to a resonance frequency of a first nucleus, the second frequency corresponding to a resonance frequency of a second nucleus, wherein the first nucleus is different from the second nucleus; means for inducing an RF magnetic field; and means for detecting NMR signals at the first frequency. A method of NMR measurement includes inducing a static magnetic field having a selected magnetic field strength in an earth formation sample; acquiring NMR measurements having J coupling information; and deriving the J coupling information from the NMR measurements.

Abstract: A method and system are disclosed for NMR echo-train data acquisition and processing for enhanced tracking of the error in the signal due to magnetoacoustic effects, known as ringing, that are not cancelled out or otherwise corrected. In one aspect, the method enables correction of ringing signals in a single pass by way of collecting a composite signal that includes echoes due to pulses at least at two different frequencies. The choice of one or more of the frequencies, the phase of the pulses, and the recovery period enable cancellation of the ringing signal from the echoes, including the echo from an excitation pulse. In another aspect, the method encompasses providing protection against errors due to tool motion by saturating a relatively wide sensitive region with the echo signals collected from within this relatively wide sensitive signal. Preferred embodiments of the invention include one or more of the aforementioned aspects.

Abstract: A method for determining downhole reservoir wettability includes acquiring a first set of NMR measurements of formation fluids in earth formations at a selected axial depth; inverting the first set of the NMR measurements to produce a first distribution of a spin relaxation parameter for a fluid component in the formation fluids; acquiring a second set of NMR measurements of a formation fluid sample removed by a formation fluid testing tool at the selected axial depth, the formation fluid sample being kept at a substantially same pressure and temperature as those of the formation fluids in the earth formations at the selected axial depth; inverting the second set of NMR measurements to produce a second distribution of the spin relaxation parameter for the fluid component in the formation fluid sample; determining the reservoir wettability from a comparison of the first and second distributions of the spin relaxation parameter.

Abstract: The invention is related methods for nuclear magnetic resonance measurements; the methods include the steps of applying a first static magnetic field to polarize the sample; radiating a radio frequency pulse onto the sample. Subsequently, applying a second magnetic field such that when combined with the first static magnetic field; a third static magnetic field is produced. Finally, during the application of the second static magnetic field or after removing it, the NMR signal emitted by the sample is measured. Finally, the methods can be used for making nuclear magnetic resonance measurements in wells.

Abstract: An apparatus and method for determining a parameter of interest of a formation composed of carbonate rock. A nuclear magnetic resonance (NMR) sensor assembly produces a pulsed RF field designed for obtaining measurements indicative of the parameter of interest of the formation. A downhole processor processes the measurements for obtaining BVI and BVM using a cutoff time based on classification of the carbonate. Further processing is done to estimate the permeability of the carbonate.

Abstract: Measurements from many logging instruments such as Gamma ray counts from a pulsed neutron instrument, typically have a spectrum that contains a plurality of exponentially decaying components. The slowest decaying component is obtained by fitting a single exponential over the tail end of the data and selecting a beginning for the fitting window that minimizes the product of the chi-square and the standard error of the fit. The single determined component may be subtracted from the data and the process repeated to give additional components. The determined components are indicative of thermal neutron capture cross-sections.

Abstract: Borehole NMR logging apparatus and methods. A multifrequency method using triple-wait-time is disclosed for determining gas- and light-oil-filled porosity over a broad range of reservoir conditions. The method improves the signal-to-noise ratio and the determination of T1 values for the hydrocarbons, especially when the reservoir contains different fluid types. A set of conditions is derived for the selection of optimum acquisition parameters for logging applications. The data acquisition and processing method enables accurate determination of the pore volumes occupied by each hydrocarbon phase as well as the pore volume occupied by water, as well as accurate T1. A set of conditions is developed to aid in the selection of wait-time combinations appropriate for logging conditions.

Abstract: A pulsed field gradient NMR (=nuclear magnetic resonance) method using stimulated echoes for determining the translational isotropic or anisotropic diffusion coefficient of a molecule or supra-molecular assembly or the flow rate and direction of fluids containing such molecules is characterized in that the molecule or supra-molecular assembly contains one or several isotopes (X) of non-zero nuclear spin other than protons having longitudinal relaxation times T1(X) that are longer than the longitudinal relaxation times T1(H) of the protons, and that the information about the localization of the molecule or supra-molecular assembly during the diffusion or flow interval is temporarily stored in the form of longitudinal magnetization of said isotope or isotopes. Thus, the determination of translational diffusion coefficients or flow rates of supra-molecular assemblies or molecules with short T1(H) values, in particular of supra-molecular assemblies or molecules with M≧50 kDa is accomplished.

Abstract: A contactless rotary shaft position sensor provides for precision computation of shaft angle for a wide range of input shaft rotational angles. The sensor includes two annular two-pole magnets which are connected by a precision, motion-transmitting gear train. An optional second gear train between one of the magnets and the input shaft can provide additional angular rotation scaling to accurately measure either fractional or a large number of multiple turns of the input shaft. The gear ratios are selected such that one of the magnets does not rotate more than one revolution. Pairs of ratiometric Hall-effect or magnetoresistive sensors provide differential voltage signals which are used for sensing angular position of each magnet over a full 360 degrees of rotation. The single-turn magnet provides an absolute, coarse indication of input shaft rotation with a typical accuracy of 2%. The gear ratio between the magnets produces several turns of the second magnet for each turn of the single-turn magnet.

Abstract: Novel pulse sequences are used to probe the properties of porous media, such as are found in subterranean formations and core samples. This use allows diffusion effects to be uncoupled from the overall T2 relaxation time of the sample. Properties such as internal field gradient and distribution of diffusion coefficients may be determined. A series of pulse sequences are applied to the media to be evaluated. The series of pulse sequences include first and second windows. The first windows include pulse sequences have varying characteristics, such as increasing echo spacing, while the second windows preferably utilize similar pulse sequences which have very small echo spacing. Apparent internal field gradient distribution and apparent diffusion coefficient may be determined as a function of T2 relaxation time.

Abstract: A method for determining an earth formation property from nuclear magnetic resonance measurements includes applying suppression functions to spin echoes in at least one burst measurement set to produce a modified burst data set, the suppression functions to suppress contribution of spin echoes having non-negligible polarization correction; inverting the modified burst data set and at least one standard spin echo measurement set to produce a nuclear magnetic resonance parameter distribution, the at least one standard spin echo measurement set and the at least one burst measurement set being acquired on an earth formation sample; and computing the earth formation property from the nuclear magnetic resonance parameter distribution. The nuclear magnetic resonance parameter includes at least one selected from longitudinal relaxation time, transverse relaxation time, a ratio of longitudinal relaxation time to transverse relaxation time, and diffusion constant.

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: An apparatus is disclosed for generating a magnetic field of high field strength, spatial uniformity and minimal drift of magnetic field intensity over a temperature range of about 0° C. to 175° C. This apparatus may be used in a standard modular logging tool for direct downhole NMR measurements of various parameters of fluid samples of geologic formations near the walls of a borehole. In one embodiment, the apparatus is composed of two tubular permanent magnets made of different magnetic materials with different magnetic temperature coefficients to provide temperature compensation. The apparatus preferably also utilizes a pressure barrel that surrounds the magnets and provides a return path for magnetic flux lines, thereby increasing flux density within the measurement volume.

Abstract: A method for processing Nuclear magnetic resonance (NMR) well logging data in the presence of coherent transient signals and offsets is disclosed. The method comprises the addition of R and X-Channel transients and offsets to the relaxation model appropriate for a user selected pulse sequence. The effects of the ringing and offsets are automatically compensated for by fitting R and X-Channel spin-echo data to the relaxation model.

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: System and method for characterizing formation properties based on NMR measurements. NMR clay measurements of this invention distinguish between interstitial pore water and the water adsorbed by the clay minerals. The measurements can be used to determine the quantity of adsorbed water in different clays and correct previously available data obtained using conventional density and neutron porosity logs. A new petrophysical parameter wetness clay is defined as an intrinsic parameter for clays, and its value is computed for members of the smectite group of clays, such as montmorillonite. The wet clay values for the density, neutron logs based on the adsorbed water in clays are used to enhance the quality and accuracy of the overall log interpretation.

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: An method and system are disclosed for NMR echo-train data acquisition and processing for enhanced vertical resolution for a given signal to noise ratio. In one aspect, the method is based on providing an estimate of non-formation signal components and removing the estimate from the NMR signals. Computation of the estimate is done from the data itself or using a direct measurement of non-formation signals. In another aspect, the functions of reducing coherent noise components is separated from the function of reducing the random noise components, to enhance the resolution of the NMR pulse echo data for a given signal to noise ratio (SNR) of the data. Combination processing is disclosed, which enables efficient filtering of the input NMR data for both relatively high and relatively low SNR of the formation data.

Abstract: In one embodiment of the present invention, a method of measuring the molecular displacement of a fluid is disclosed comprising: (a) applying a strong magnetic field gradient to the fluid; (b) applying a sequence of oscillating magnetic field pulses to the fluid wherein the sequence includes a first portion followed by a second portion, wherein the first portion spatially modulates the magnetization state of the fluid and the second portion monitors the evolution of the modulation; (c) detecting magnetic resonance signals from the fluid; and (d) analyzing the detected signals to determine the molecular displacement of the fluid. This method may be used to determine the diffusion of the fluid or the restricted diffusion of the fluid through the porous media if the fluid is within a porous media (such as earth formation, bone, wood or other material). Also disclosed is a logging tool configured to implement this methodology.

Abstract: The present invention discloses a diffusion edited pulse technique that allows information about a fluid to be extracted, comprising: a) obtaining a fluid sample; b) generating a sequence of magnetic field pulses in the fluid, the sequence comprising an initial magnetic field pulse, a first portion that follows the initial magnetic field pulse, and a second portion that follows the first portion; c) detecting magnetic resonance signals using the second portion of the sequence; d) modifying the first portion of the sequence, and repeating steps (b) and (c); and e) extracting information about the fluid by determining relaxation and diffusion characteristics and their correlation based on the signals detected in steps (c) and (d). Also disclosed is a logging tool equipped with a processor to implement the diffusion edited pulse technique.

Abstract: An NMR measurement apparatus includes at least one magnet, at least one antenna, an RF pulse transmitter and a controller. The magnets) establish a static magnetic field, and the RF pulse transmitter is coupled to the antenna(e). The controller is coupled to the transmitter and the antenna(e). The controller is adapted to cause the RF transmitter to transmit RF pulse sequences into a sample and for each different RF pulse sequence, vary an estimated pulse width for producing a predetermined flip angle by a different scaling factor to produce flip angles near the predetermined flip angle. The controller is adapted to receive spin echo signals in response to the transmission of the RF pulse sequences; determine a property of the sample in response to the spin echo signals; and use the spin echo signals to determine an optimal pulse width for producing the predetermined flip angle.

Abstract: In an operating method for a magnetic resonance tomography apparatus a sequence of digital signals is transmitted to the digital-analog converter. An analog signal is emitted from the digital-to-analog converter for each digital signal to a coil system for producing a gradient magnetic field. A signal processor produces a processed digital signal which is supplied to the digital-to-analog converter to produce the analog signal. A difference between the incoming digital signal and the processed digital signal Is determined by the signal processor and is added to the next incoming digital signal or at least for a portion thereof.

Abstract: The present invention relates to a method and apparatus for determining the wettability of a porous media, such as bone, plant, food, wood or molecular sieves, etc., having two or more fluids. The method of the present invention correlates a diffusion-relaxation calibration function representative of at least one fluid in the porous media with a 2-D function developed using diffusion-editing to determine wettability of the porous media.

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.