Abstract: A method to obtain a free induction decay signal using includes inducing a static magnetic field in a sample volume. A radio frequency (RF) magnetic field is then induced in the sample volume. The RF magnetic field has parameters selected to minimize the contribution of inhomogeneity to the static magnetic field to a free induction decay time. The free induction decay signal is then detected from the sample volume. In one example, prior to inducing the RF magnetic field, a reorienting radio frequency magnetic field is induced in the sample volume to reorient magnetic spins by a first selected angle. The inducing the RF magnetic field in this example has parameters selected to reorient spins by a second angle. The inducing the RF magnetic field and detecting the free induction decay signal are repeated until nuclear magnetic equilibrium is substantially attained.

Abstract: An NMR logging tool for conducting NMR measurements in a plurality of sensitive volumes ranging up to a meter from the tool. The tool comprises a magnetic assembly using one or more permanent magnets and at least one pole piece for extending a magnet pole and shaping the magnetic field to simulate a magnetic monopole in a sensitive volume within the formation. Different embodiments of a segmented antenna enable directional NMR logging. The tool embodiments and methods of their use are suitable for wireline or LWD logging, and can be used for directional drilling.

Abstract: A nuclear magnetic resonance (NMR) method is used to determine a velocity distribution or velocity image of a flowing fluid in a downhole environment. The method comprises applying a radio frequency pulse sequence; applying a magnetic field gradient magnetic field and a gradient pulse duration; measuring a NMR signal; determining a phase characteristic of the NMR signal; and determining the velocity distribution or image of the fluid using the determined phase characteristic, the magnetic field gradient pulse parameters, and a time delay between gradient pulses.

Abstract: A coil arrangement for a magnetic resonance apparatus has a number of coil elements that are capable of being operated independently of one another and are situated around a common central area. Each coil element of the coil arrangement is capacitively or inductively decoupled from the coil elements of the coil arrangement that are immediately adjacent to this coil element. In the central area, there is situated a capacitor network that connects the coil elements of the coil arrangement to one another. The capacitor network is fashioned and dimensioned such that it at least reduces the coupling of each coil element of the coil arrangement to at least one additional coil element of the coil arrangement that is not immediately adjacent to the respective coil element.

Abstract: A method for determining fluid saturation in a formation at a plurality of radial depths near a wellbore, the method including: obtaining multi-frequency nuclear magnetic resonance (NMR) response data for the formation; and processing the data to determine simultaneously the fluid saturation at each radial depth. A computer program product is provided.

Abstract: An instrument for investigating properties of an earth formation includes a body housing a nuclear quadrupole resonance (NQR) probe, the probe having at least one coil wound around a core material and an electronics coupling, the body being adapted for insertion into a wellbore within the earth formation. A method and computer program product are provided.

Abstract: The quality factor of a NMR-antenna depends upon mud conductivity, formation resistivity and the borehole size. The Q of the antenna is measured. From measurement of one of formation conductivity or borehole size, the other can be determined.

Abstract: A method and system for determining dynamic permeability of gas hydrate formations including deploying a tool within a wellhole configured for magnetic resonance measurements, determining permeability of a formation at or near zero saturation of the gas hydrate and deriving the relationship between permeability and gas hydrate saturation for the formation.

Abstract: A downhole nuclear magnetic resonance method for measuring a property of a formation, the method includes applying a polarizing magnetic field to the formation, the field including a spatial distribution of magnitude; selecting an investigation region of the formation; decaying the polarizing magnetic field according to a decay shape to provide for substantially exciting only nuclei in the investigation region; and measuring signals induced by precession of the nuclei in the investigation region.

Abstract: An induction logging tool having concentric transmitter and receiver antennas can be used to make measurements of earth formations at frequencies up to 500 MHz. The antennas may be mounted on the mandrel of a bottomhole assembly for MWD applications, or may be pad mounted for wireline applications. Litz winding is used in the coils to minimize eddy current losses. The antennas may be formed on a flexible circuit board.

Abstract: For use in logging downhole in an earth borehole, a method for determining a characteristic of oil that may be present in a downhole measurement region, includes the following steps: providing a plurality of crude oil samples; determining the viscosities of the crude oil samples; performing test measurements, using a predetermined operating mode, on media including the crude oil samples to obtain test data; applying a test processing procedure to the test data to obtain an output test parameter relating to the test data and the predetermined operating mode; deriving, for the plurality of crude oil samples, a correlation relating the output test parameter to the viscosities of the crude oil samples; performing downhole measurements in the measurement region with a logging device, operated with substantially the predetermined operating mode, to obtain logging data, and applying a measurement processing procedure to the logging data to obtain an output logging parameter; and determining the oil characteristic us

Abstract: A compact and integrated portable device is provided for the analysis of dispersions by low-field pulsed NMR including: an NMR probe module, a means for generating radio frequency and magnetic field gradient pulses, a signal processor, and a master controller. Also provided are methods for using the device to measure one or more characteristics of phases or particles comprising a dispersion such as surface area, solid/liquid ratio, particle size, and elemental analysis.

Abstract: A method and apparatus useful to determine characteristics of fluid flow, such as fluid holdup and flow velocity. The apparatus comprises a flow tube, a permanent magnet, a first set of coils, and a second set of coils. The first set of coils creates a radio frequency magnetic field within the flow tube with a series of refocusing pulses. The second set of coils encodes velocity information onto the fluid molecules using rotating frame zeugmatography that is later decoded and used to estimate the fluid flow velocity.

Abstract: NMR spin echo signals are acquired downhole. An independent component analysis is used to determine parameters of a parametric model of the T2 distribution whose output matches the measurements. The model parameters are telemetered to the surface where the properties of the formation are reconstructed. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Abstract: The present disclosure provides a downhole tool that includes a magnetometer and a nuclear magnetic resonance (NMR) sensor. One or more compensating magnets are provided on the tool to cancel or offset the effect of the magnetic field of the magnets of the NMR sensor on the magnetometer measurements made during drilling of a wellbore. The compensating magnets may have the same magnetic field characteristics as the sensor magnets and may be made of the same material.

Abstract: A method for measuring the wettability of rocks by low-field nuclear magnetic resonance is described which has application for hydrocarbon reservoir engineering or development, or in civil engineering. The method essentially determines the water wet pore surface and the oil wet pore surface when the sample is saturated with water and oil, by measurements of relaxation times (T1, T2) of the sample placed in a nuclear magnetic resonance device, previously brought to various water or oil saturation states, and calculating the wettability index by combination of values the relaxation times obtained for said surfaces.

Abstract: A nuclear magnetic resonance apparatus that may be used in connection with a variety of different tools, including a down-hole side-wall coring tool as well as with manufacturing process controllers. In one embodiment, the nuclear magnetic resonance apparatus may include a magnet assembly constructed around a sample chamber. The magnet assembly is constructed and arranged to provide a non-uniform magnetic field having a known magnetic field gradient inside the sample chamber. The use of gradient fields may allow for a more flexible and robust magnet assembly design that may be suitable for a variety of different applications.

Abstract: A method to determine one or more properties of a substance in a downhole region of investigation is disclosed. The method includes obtaining NMR measurements from the region of investigation, obtaining at least one additional well log measurement from the region of investigation, expressing the NMR measurements in terms of NMR subcomponents, expressing the additional well log measurement in terms of well log subcomponents, and simultaneously inverting the expressed NMR measurements and the expressed additional well log measurement for the NMR subcomponents to yield one or more properties of a substance.

Abstract: Certain embodiments are directed to devices, systems and methods for determining a penetration depth of an induced oscillation in a porous medium. In certain examples, the devices, systems and methods are designed to detect a magnetic resonance signal in the presence of an induced oscillatory fluid flow in a porous medium to determine penetration depth of the induced oscillation in the porous medium. In some examples, the mobility of a fluid in the porous medium may be determined from the determined penetration depth.

Abstract: A method is disclosed for interpretation of multi-dimensional nuclear magnetic resonance data taken on a sample of an earth formation. Specifically, a set of NMR data is acquired for a fluid sample located either in a borehole or in a laboratory environment. From the set of NMR data, a multi-dimensional distribution is calculated using a mathematical inversion that is independent of prior knowledge of fluid sample properties. The multi-dimensional distribution is graphically displayed on a multi-dimensional map. Each fluid instance or artifact visible on the graph is identified as representing a probable existence of a detected fluid. One or more quantitative formation evaluation answers for one or more fluid instances is computed based on the multi-dimensional distribution associated with the respective fluid instance.

Abstract: Method of determining the permeability of an underground medium from NMR logs of the permeability of rock fragments from the medium, based on prior calibration of the permeability resulting from this measurements, from direct measurement on rock fragments, such as cuttings for example. The method mainly comprises measuring permeability (k) from rock fragments, measuring the signal produced by a device allowing NMR analysis of the rock fragments previously saturated with a protonated liquid (brine for example), obtaining optimum values for the parameters of a relation giving the permeability as a function of the NMR signal, and applying this relation to the well zones that have already been subjected to NMR logging but for which no direct permeability measurements are available. One example of one of the applications for the present invention is the evaluation of a hydrocarbon reservoir.

Abstract: An apparatus and methods that can be used to determine various qualitative parameters of an earth formation from nuclear magnetic resonance (NMR) measurements. One embodiment provides a method of NMR-based remote sensing in which a nuclear spins in fluid of interest are encoded while inside an earth formation and then withdrawn into a tool module and analyzed by a sensor located in the tool module. Separate encoding and detection systems may be used, allowing each system to be independently optimized. In particular, because detection of the encoded spins may occur while the spins are inside the detector system, rather than within the earth formation (where they are encoded), the detector system may be constructed to employ a highly uniform magnetic field. This may facilitate various NMR measurements.

Abstract: A system and method for measuring fluid flow in a wellbore in an earth formation using time-of-flight (TOF) sensing and remote detection nuclear magnetic resonance (NMR) techniques, by applying a magnetic field to the formation to polarize spins present in a portion of the formation, providing an encoding shell in the formation, selecting an encoding volume from the encoding shell, applying an encoding signal to excite the spins in the encoding volume, introducing a time delay to the encoding signal, providing a detection shell in the formation, applying a detection signal to the detection shell, detecting an NMR signal generated by the migration of spins from the encoding shell to the detection shell, and collecting TOF data corresponding to time elapsed from when a spin is encoded to when the spin reaches the detection shell.

Abstract: Methods and systems are described for estimating of the level of contamination of downhole fluid using physical property measurements, and mathematical modeling of contamination functions and fluid property mixing laws. The proposed approaches enable computation of estimates of the pumping time needed to achieve a certain contamination threshold level.

Abstract: A method and apparatus useful to determine characteristics of fluid flow, such as fluid holdup and flow velocity. The apparatus comprises a flow tube, a permanent magnet, a first set of coils, and a second set of coils. The first set of coils creates a radio frequency magnetic field within the flow tube with a series of refocusing pulses. The second set of coils encodes velocity information onto the fluid molecules using rotating frame zeugmatography that is later decoded and used to estimate the fluid flow velocity.

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: The grain size of a pore-scale geometric model of a clastic earth formation are adjusted so that the NMR relaxation time distribution output of the model matches a measured NMR distribution. Fluid drainage and imbibing can be simulated. Additional properties of the earth formation are predicted using the pore-scale model. The additional properties may be based on additional measurements of properties of a fluid in the formation.

Abstract: Methods and systems are provided for displaying and forecasting the lithology and wellbore conditions to be encountered while conducting drill string operations in a wellbore. A method and system is described for predicting and modeling lithology while operating a drill string in a wellbore, comprising: developing a 3-D lithological model of a subsurface area; projecting a well path through said subsurface area; determining an open cylinder lithology display of said projected well path; and recording said determined open cylinder display. The open cylinder lithology display (the Predictive Stratigraphy Image) may be displayed with geological or structural cross-sections to compare the well path and the predicted well path, with the actual subsurface environment. Data acquired during drilling operations can be used in real time to update the model or the Predictive Stratigraphy Image, and the results compared with Predictive Image Logs and other wellbore images and data.

Abstract: NMR spin echo signals are corrected for axial motion of the borehole logging tool. The correction is applied to an averaged echo train using an average velocity determined from surface measurements over the duration of averaging of the echo trains. An additional correction may be applied to correct for excess polarization or incomplete polarization of nuclear spins due to an insufficient wait time between pulse sequences.

Abstract: A method and apparatus are provided for measuring a parameter such as capillary pressure in porous media such as rock samples. The method comprises mounting a sample in a centrifuge such that different portions of the sample are spaced at different distances from the centrifuge axis, rotating the sample about the axis, measuring a first parameter in the different portions of the sample, and determining the value of a second parameter related to the force to which each portion is subjected due to rotation of the sample. In one embodiment, the first parameter is relative saturation of the sample as measured by MRI techniques, and the second parameter is capillary pressure.

Abstract: NMR spin echo signals are corrected for axial motion of the borehole logging tool. The correction is applied to an averaged echo train using an average velocity determined from surface measurements over the duration of averaging of the echo trains. An additional correction may be applied to correct for excess polarization or incomplete polarization of nuclear spins due to an insufficient wait time between pulse sequences. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: NMR data are acquired using a phase-alternation of the tipping pulse. Averaged properties are estimated over a window length. The averaged properties are inverted to undo the effects of the averaging. A matrix defined in terms of Walsh functions is used in the inversion.

Abstract: A novel magnetic resonance imaging method is presented for forming an image of an object from a plurality of signals acquired by an array of receiver antennae, whereas prior to imaging a sensitivity map of each of the receiver antennae is provided, at least two adjacent antennae record signals originating from the same imaging position and the image intensity is calculated from the signals measured by different antennae, wherein the number of phase encoding steps is reduced with respect to the full set thereof.

Abstract: A method for determining a characteristic of earth formations from measurements taken on the formations, includes the following steps: producing a data base that includes a multiplicity of data points, each data point representing a stored formation characteristic output related to a stored input measurement; deriving, from the data base, a mapping function; deriving an input formation measurement value; and determining an output formation characteristic value from the data base, the mapping function, and the input formation measurement value.

Abstract: Data from a string of multiple formation evaluation data sensor are evaluated by an expert system. Based on the analysis, the logging speed is increased if all the sensors justify it, and is reduced if any of the sensors require a reduced logging speed. Alternatively, the sensitive volume of a NMR sensor is altered based on a determination of a fraction of the sensitive volume that includes a borehole fluid.

Abstract: An apparatus and method of obtaining information about a property of interest relating to an earth formation resulting in reduced ringing effects is discussed. A Nuclear Magnetic Resonance (NMR) logging tool is conveyed into a borehole in the earth formation. A first pulse sequence is applied having a first associated measurement frequency, and first NMR signals are measured. The first NMR signals include non-formation signals resulting from an excitation pulse and a refocusing pulse in the first pulse echo sequence. A second and third pulse sequence, at different frequencies from each other and from the first frequency, is applied, and corresponding second and third NMR signals are measured. A phase of the non-formation signals resulting from the first pulse echo sequence and a phase of the non-formation signals resulting from the second and third pulse echo sequences are substantially evenly distributed around a unit circle.

Abstract: A method for estimating a concentration of a substance in a test sample of formation fluid, comprising measuring an NMR parameter of a first sample of formation fluid to obtain a first measurement, adding a known quantity of the substance to the first sample to produce a modified sample, measuring the NMR parameter of the modified sample to obtain a second measurement; and determining a relation between the concentration of the substance and a function of the NMR parameter using the first and second measurements and the NMR parameter of the substance.

Abstract: A method and apparatus for obtaining a parameter of interest relating to a region proximate a nuclear magnetic resonance (NMR) logging tool suitable for subterranean well logging is disclosed. The nuclei of the region are subjected to a pulsed NMR technique and are productive of NMR logging data, the nuclei of the region characteristically having a longitudinal relaxation time T1 distribution and an apparent transverse relaxation time T2app distribution. In response to the NMR logging data, an R distribution is defined as R=T1/T2app, the T2app and R distributions are processed as separate bins, along with the NMR logging data, according to a two-dimensional inversion model, and a signal intensity map of R versus T2app is provided that is representative of the parameter of interest relating to the region. In response to a high-intensity signal on the map being within a first range of T2app values and a first range of R values, the presence of a light hydrocarbon within the region is identified.

Abstract: NMR measurements are made with a MWD tool having azimuthal sensitivity. The permanent magnet may be a U-shaped magnet or may have an opposed pair of magnets with axial orientation. The tool is designed for pulsing with short sequences for estimating BVI and CBW and minimizes the effect of tool motion.

Abstract: Measurements made with porosity and density logging tools in a gas reservoir may differ due to invasion effects. The effects are particularly large on measurement-while-drilling applications where invasion is minimal. Using a Monte-Carlo method, a relationship is established between true formation porosity and porosity estimates from density and porosity tools. This relationship is used on real data to get an improved estimate of formation porosity and of gas saturation.

Abstract: An apparatus and method for compensating for the effect of tool motion in NMR MWD measurements. Signals obtained from a directionally sensitive receiver are compensated for the effects of tool motion. In an alternative embodiment, directional transmitters and receivers are used, with the pulsing of the transmitter controlled by the output of motion sensors. In another embodiment, the transmitters and receivers may be axisymmetric and the received signals are corrected using results of a NMR simulation program that takes account of the recorded motion of the apparatus.

Abstract: A Toroid Cavity Detector (TCD) is provided for implementing nuclear magnetic resonance (NMR) studies of chemical reactions under conditions of high pressures and temperatures. A toroid cavity contains an elongated central conductor extending within the toroid cavity. The toroid cavity and central conductor generate an RF magnetic field for NMR analysis. A flow-through capillary sample container is located within the toroid cavity adjacent to the central conductor to subject a sample material flowing through the capillary to a static magnetic field and to enable NMR spectra to be recorded of the material in the capillary under a temperature and high pressure environment.

Abstract: A method for determining a property of a substance in a downhole measurement region includes the following steps: providing a static magnetic field having a static magnetic field gradient in the measurement region; applying, in the measurement region, a pulse sequence that includes a tipping pulse, a re-focusing pulse, and a pulsed field gradient pulse train; wherein the pulsed field gradient pulse train includes a first portion and a second portion; the first portion comprising a first pulse or set of pulses having a first polarity and a second pulse or set of pulses having a second polarity, the second polarity being opposite to the first polarity, and wherein the first portion occurs before the re-focusing pulse; the second portion comprising a third pulse or set of pulses having the first polarity and a fourth pulse or set of pulses having the second polarity, and wherein the second portion occurs after the re-focusing pulse; and receiving one or more spin echoes from the measurement region.

Abstract: A method for obtaining a parameter of interest relating to a region investigated by a nuclear magnetic resonance (NMR) tool and a non-NMR tool is disclosed. Data arising from the NMR tool is acquired, and data arising from the non-NMR tool is acquired. A solution equation is utilized for NMR signal intensity, the solution equation being functionally related to the NMR data, and a solution constraint is utilized based at least partially on the non-NMR data. The solution equation is solved for the signal intensity subject to the solution constraint, wherein the solving provides information relating to the parameter of interest.

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 an antenna core material for NMR and resistivity devices in a borehole. The probe stuctural geometry facilitates the use of material, which has a relatively low magnectic permeability.

Abstract: Spin echo signals measured with a multifrequency NMR logging tool are analyzed to determine if one or more of the regions of examination associated with each of the frequencies has signal contamination from borehole fluids. A variety of different methods can be used for analysis. Corrected spin echo signals can be obtained and processed to give improved estimates of formation parameters.

Abstract: System and methods for estimating properties of a geologic formation are disclosed. A preferred embodiment includes a method for estimating properties of a geologic formation, comprising the steps of: measuring a property of the formation in two or more directions along a path in the formation; obtaining directional property values for at least one spatial unit along the path in the formation based on the property measurements; and providing an anisotropy estimate of the formation from the obtained directional property values.

Abstract: Permeability determinations are made from NMR measurements of a logging tool. The NMR measurements are used to find an observed critical spin—spin relaxation time which is used in conjunction with an in situ determination of surface relaxivity of a rock in order to generate permeability determinations.

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: A method for characterizing a fluid sample withdrawn from an earth formation. The method includes performing nuclear magnetic resonant spin echo measurements on the fluid sample at a nuclear magnetic resonant frequency of carbon-13. Amplitudes of the spin echo measurements are summed. The summed measurements are spectrally analyzed. The fluid is characterized by determining whether aromatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 130 part per million shift from the carbon-13 frequency. The fluid is also characterized by determining whether aliphatic hydrocarbons are present by measuring an amplitude of the spectrally analyzed spin echo measurements at about 30 parts per million frequency shift.