Abstract: Systems and methods are provided for investigating a downhole formation using a nuclear magnetic resonance (NMR) tool. While the tool is moving through the borehole, the formation is magnetized and resulting signals are obtained. In accordance with the present approach, the acquired signals can be resolved azimuthally and/or laterally and can be reconstructed to obtain an indication of a parameter of the formation at multiple locations along the length of the borehole.

Abstract: Methods and systems for characterizing a subterranean formation using nuclear magnetic resonance (NMR) measurements are described herein. One method includes locating a downhole logging tool in a wellbore that traverses the subterranean formation, and performing NMR measurements to obtain NMR data for a region of the subterranean formation. The NMR data is processed by employing sparse Bayesian learning (SBL) to determine a multi-dimensional property distribution of the NMR data (e.g., T1-T2, D-T2, and D-T1-T2 distributions). The sparse Bayesian learning can utilize Bayesian inference that involves a prior over a vector of basis coefficients governed by a set of hyperparameters, one associated with each basis coefficient, whose most probable values are iteratively estimated from the NMR data. The sparse Bayesian learning can achieve sparsity because posterior distributions of many of such basis coefficients are sharply peaked around zero.

Abstract: A methods are provided for investigating a sample containing hydrocarbons by subjecting the sample to a nuclear magnetic resonance (NMR) sequence using NMR equipment, using the NMR equipment to detect signals from the sample in response to the NMR sequence, analyzing the signals to extract a distribution of relaxation times (or diffusions), and computing a value for a parameter of the sample as a function of at least one of the relaxation times (or diffusions), wherein the computing utilizes a correction factor that modifies the value for the parameter as a function of relaxation time for at least short relaxation times (or as a function of diffusion for at least large diffusion coefficients).

Abstract: Systems and methods are provided for investigating a downhole formation using a nuclear magnetic resonance (NMR) tool having two or more radio frequency receiving coils. While the tool is moving through the borehole, the formation is magnetized and resulting signals are obtained. In accordance with the present approach, the acquired signals can be resolved azimuthally and can be reconstructed to obtain an indication of a parameter of the formation at multiple locations along the length of the borehole.

Abstract: Methods are provided for identifying one or more transition characteristics in a hydrocarbon fluid such as asphaltene onset pressure (AOP), bubble point or dew point. A transition characteristic is determined by subjecting the fluid to different pressures or temperatures, conducting NMR tests at the different pressures or temperatures to obtain signals, processing the signals to obtain values of a function of an NMR parameter as a function of pressure or temperature, and analyzing the values to find a discontinuity that identifies the transition characteristic. In embodiments, the NMR parameters may include at least one of a relaxation parameter such as T2 or a T1-T2 ratio, a diffusion parameter and an initial magnetization parameter. In embodiments, dual linear fitting, Bayesian change point detection algorithms, and instantaneous slope analysis may be utilized to analyze the values in order to find a discontinuity.

Abstract: A methods are provided for investigating a sample containing hydrocarbons by subjecting the sample to a nuclear magnetic resonance (NMR) sequence using NMR equipment, using the NMR equipment to detect signals from the sample in response to the NMR sequence, analyzing the signals to extract a distribution of relaxation times (or diffusions), and computing a value for a parameter of the sample as a function of at least one of the relaxation times (or diffusions), wherein the computing utilizes a correction factor that modifies the value for the parameter as a function of relaxation time for at least short relaxation times (or as a function of diffusion for at least large diffusion coefficients).

Abstract: Adsorbed gas in a formation may be estimated. Nuclear magnetic resonance (NMR) data for a subsurface geological formation is obtained, and at least a portion of the NMR data is corrected to produce corrected NMR data. A NMR-based estimate of formation porosity is determined using the corrected NMR data. Dielectric permittivity data for the subsurface geological formation is obtained, and a dielectric permittivity-based estimate of the formation water-filled porosity is determined using the dielectric permittivity data. A gas volume is determined using the determined NMR-based estimate of the formation porosity and the determined dielectric permittivity-based estimate of the formation water-filled porosity. The gas volume may be determined by subtracting the determined dielectric permittivity-based estimate of the formation water-filled porosity from the determined NMR-based estimate of the formation porosity. The gas volume per unit volume of the formation may be determined using an equation of state.

Abstract: Methods and related systems are described for estimating fluid or rock properties from NMR measurements. A modified pulse sequence is provided that can directly provide moments of relaxation-time or diffusion distributions. This pulse sequence can be adapted to the desired moment of relaxation-time or diffusion coefficient. The data from this pulse sequence provides direct estimates of fluid properties such as average chain length and viscosity of a hydrocarbon. In comparison to the uniformly-spaced pulse sequence, these pulse sequences are faster and have a lower error bar in computing the fluid properties.

Abstract: Methods and apparatuses are provided for analyzing a composition of a hydrocarbon-containing fluid. The methods include using a nuclear magnetic resonance (NMR) tool to conduct NMR measurements on the hydrocarbon-containing fluid to obtain NMR data. A non-NMR tool, such as an optical tool, is used to conduct additional measurements and to obtain non-NMR data on the fluid. The methods further include determining an indication of the composition of the fluid by using the NMR data and normalizing the indication of the composition of the fluid using the non-NMR data.

Abstract: Methods and apparatuses are provided for analyzing a composition of a hydrocarbon-containing fluid. The methods include using a nuclear magnetic resonance (NMR) tool to conduct an NMR measurement on the hydrocarbon-containing fluid to obtain NMR data. A non-NMR tool, such as an optical tool, is used to conduct additional measurements on the hydrocarbon-containing fluid and to obtain non-NMR data on the fluid. An indication of the composition of the fluid can be determined by using the NMR data and the non-NMR data in an inversion process.

Abstract: Apparatus and methods of analyzing a composition of a hydrocarbon-containing fluid including using a nuclear magnetic resonance (NMR) tool to conduct a NMR relaxation measurement, a diffusion measurement, or both on the hydrocarbon-containing fluid to obtain NMR data, using a non-NMR tool to conduct an additional measurement of a reference fluid to obtain non-NMR data wherein the additional measurement comprises gas chromatography, optical observation, or both, and using the NMR data and the non-NMR data in an inversion process to determine an indication of the composition of the hydrocarbon-containing fluid. In some embodiments, the indication is determined over 4 chain length nodes.

Abstract: Systems and methods are provided for investigating a downhole formation using a nuclear magnetic resonance (NMR) tool having two or more radio frequency receiving coils. While the tool is moving through the borehole, the formation is magnetized and resulting signals are obtained. In accordance with the present approach, the acquired signals can be resolved azimuthally and can be reconstructed to obtain an indication of a parameter of the formation at multiple locations along the length of the borehole.

Abstract: Systems and methods are provided for investigating a downhole formation using a nuclear magnetic resonance (NMR) tool. While the tool is moving through the borehole, the formation is magnetized and resulting signals are obtained. In accordance with the present approach, the acquired signals can be resolved azimuthally and/or laterally and can be reconstructed to obtain an indication of a parameter of the formation at multiple locations along the length of the borehole.

Abstract: Systems and methods are described herein for investigating a downhole formation using a nuclear magnetic resonance (NMR) tool. The tool includes multiple detectors spaced along an axis parallel to a length of the wellbore. While the tool is moving through the wellbore, NMR pulse sequences are applied to the formation and resulting NMR signals are detected by the detectors. The data obtained over a period of time by the multiple detectors are inverted together to obtain an indication of a parameter of the formation at multiple locations along the length of the wellbore.

Abstract: Methods and related systems are described for estimating fluid or rock properties from NMR measurements. A modified pulse sequence is provided that can directly provide moments of relaxation-time or diffusion distributions. This pulse sequence can be adapted to the desired moment of relaxation-time or diffusion coefficient. The data from this pulse sequence provides direct estimates of fluid properties such as average chain length and viscosity of a hydrocarbon. In comparison to the uniformly-spaced pulse sequence, these pulse sequences are faster and have a lower error bar in computing the fluid properties.

Abstract: Methods and systems for characterizing a subterranean formation using nuclear magnetic resonance (NMR) measurements are described herein. One method includes locating a downhole logging tool in a wellbore that traverses the subterranean formation, and performing NMR measurements to obtain NMR data for a region of the subterranean formation. The NMR data is processed by employing sparse Bayesian learning (SBL) to determine a multi-dimensional property distribution of the NMR data (e.g., T1-T2, D-T2, and D-T1-T2 distributions). The sparse Bayesian learning can utilize Bayesian inference that involves a prior over a vector of basis coefficients governed by a set of hyperparameters, one associated with each basis coefficient, whose most probable values are iteratively estimated from the NMR data. The sparse Bayesian learning can achieve sparsity because posterior distributions of many of such basis coefficients are sharply peaked around zero.

Abstract: Methods are provided for determining values of a pore cementation exponent m and/or a saturation exponent n for locations in a formation having similar petrophysical properties. Formation porosity, formation water saturation, and an apparent cementation exponent mn are obtained for the locations and their values are utilized to find the exponents. In one embodiment, the apparent cementation exponent and the formation water saturation are obtained from a dielectric logging tool.

Abstract: A method of obtaining nuclear magnetic resonance (NMR) data from a subterranean formation may include operating a tool in a subterranean formation for generating both NMR data and NMR scaled data based upon NMR measurements of the subterranean formation. The method also includes operating the tool for encoding and transmitting both the NMR data and NMR scaled data, and receiving and decoding, above the subterranean formation, both the NMR data and NMR scaled data from the tool. The method also includes performing error-correction of the received and decoded NMR data based upon the received and decoded NMR scaled data.

Abstract: Methods are provided for identifying one or more transition characteristics in a hydrocarbon fluid such as asphaltene onset pressure (AOP), bubble point or dew point. A transition characteristic is determined by subjecting the fluid to different pressures or temperatures, conducting NMR tests at the different pressures or temperatures to obtain signals, processing the signals to obtain values of a function of an NMR parameter as a function of pressure or temperature, and analyzing the values to find a discontinuity that identifies the transition characteristic. In embodiments, the NMR parameters may include at least one of a relaxation parameter such as T2 or a T1-T2 ratio, a diffusion parameter and an initial magnetization parameter. In embodiments, dual linear fitting, Bayesian change point detection algorithms, and instantaneous slope analysis may be utilized to analyze the values in order to find a discontinuity.

Abstract: A nuclear magnetic resonance (NMR) related distribution is estimated that is consistent with NMR measurements and uses linear functionals directly estimated from the measurement indications by integral transforms as constraints in a cost function. The cost function includes indications of the measurement data, Laplace transform elements and the constraints, and a distribution estimation is made by minimizing the cost function. The distribution estimation may be used to find parameters of the sample. Where the sample is a rock or a formation, the parameters may include parameters such as rock permeability and/or hydrocarbon viscosity, bound and free fluid volumes, among others. The parameters may be used in models, equations, or otherwise to act on the sample, such as in recovering hydrocarbons from the formation.