Systems, methods, and apparatuses for determining pore volume and pore volume compressibility of secondary porosity in rock samples is disclosed. In some implementations, determining a pore volume of a secondary porosity in a rock core sample may include saturating the rock sample with deuterium oxide (D2O) by applying a vacuum to the core sample covered by D2O; centrifuging the saturated rock sample at a selected rotational speed in the presence of a second fluid to displace a portion of the D2O from the rock sample with the second fluid; measuring the rock sample with low-field .sup.1H nuclear magnetic resonance (NMR) to determine a volume of the second fluid within the rock sample; and determining a pore volume associated with a secondary porosity based on the volume of the second fluid within the rock sample.

A method for k-space registration is provided. The method of k-space registration includes receiving a first partial k-space dataset for an object and a second partial k-space dataset for the object, selecting the first partial k-space dataset as a reference, selecting feature for estimating a transformation matrix for transforming k-space data, estimating a transformation matrix based on the feature of entire or part of the first partial k-space dataset and the feature of the second partial k-space dataset corresponding to the entire or part of the first partial k-space dataset, correcting the second partial k-space dataset based on the transformation matrix, and obtaining the corrected second partial k-space dataset. The present method is further used for partial Fourier reconstruction.

A method includes the steps of: introducing a medium with a first temperature into a measuring volume; carrying out nuclear magnetic measurements on the medium with the first temperature; determining a property of the medium at the first temperature; determining a viscosity of the medium at the first temperature using the property; and determining a derived property of the medium at a second temperature using the property of the medium at the first temperature, the viscosity of the medium at the first temperature, the first temperature, and the second temperature. The property is at least one of a first spin-lattice relaxation time constant, a first spin-spin relaxation time constant, and a first diffusion time constant. The derived property is at least one of a second spin-lattice relaxation time constant, a second spin-spin relaxation time constant, and a second diffusion time constant.

Certain aspects of the present disclosure provide methods and apparatus for performing electron paramagnetic resonance (EPR) spectroscopy on a fluid from a flowing well, such as fluid from hydrocarbon recovery operations flowing in a downhole tubular, wellhead, or pipeline. One example method generally includes, for a first EPR iteration, performing a first frequency sweep of discrete electromagnetic frequencies on a cavity containing the fluid; determining first parameter values of reflected signals from the first frequency sweep; selecting a first discrete frequency corresponding to one of the first parameter values that is less than a threshold value; activating a first electromagnetic field in the fluid at the first discrete frequency; and while the first electromagnetic field is activated, performing a first DC magnetic field sweep to generate a first EPR spectrum.

Certain aspects of the present disclosure provide methods and apparatus for performing electron paramagnetic resonance (EPR) spectroscopy on a fluid from a flowing well, such as fluid from hydrocarbon recovery operations flowing in a downhole tubular, wellhead, or pipeline. One example method generally includes, for a first EPR iteration, performing a first frequency sweep of discrete electromagnetic frequencies on a cavity containing the fluid; determining first parameter values of reflected signals from the first frequency sweep; selecting a first discrete frequency corresponding to one of the first parameter values that is less than a threshold value; activating a first electromagnetic field in the fluid at the first discrete frequency; and while the first electromagnetic field is activated, performing a first DC magnetic field sweep to generate a first EPR spectrum.

A computerized method and system include (a) estimating parameters that quantify rock fabric features (e.g., tortuosity, effective pore size, throat-size distribution) by joint interpretation of electrical resistivity, dielectric permittivity, and NMR measurements, (b) developing a new workflow for permeability assessment that incorporates the quantified rock fabric parameters, and (c) validating the reliability of the new permeability model in core-scale domain using electrical resistivity, dielectric permittivity, NMR, Mercury Injection Capillary Pressure (MICP), and permeability measurements.

A computerized method and system include (a) estimating parameters that quantify rock fabric features (e.g., tortuosity, effective pore size, throat-size distribution) by joint interpretation of electrical resistivity, dielectric permittivity, and NMR measurements, (b) developing a new workflow for permeability assessment that incorporates the quantified rock fabric parameters, and (c) validating the reliability of the new permeability model in core-scale domain using electrical resistivity, dielectric permittivity, NMR, Mercury Injection Capillary Pressure (MICP), and permeability measurements.

A method for improving a metal detector, including: processing at least one receive signal due to a receive magnetic field using at least two functions to produce two processed signals, the at least two functions are selected such that the first processed signal is more sensitive to deeply buried targets than the second processed signal; and the second processed signal is more sensitive to shallow-buried conductive objects with characteristic frequency greater than 100 kHz than the first processed signal but not sensitive to saline soil, and that the two processed signals substantially complement each other in terms of sensitivity to targets in terms of target frequency and detection depth; and processing the two processed signals to produce at least one output signal which is sensitive to deeply buried low-frequency targets, shallow-buried low-frequency targets and shallow-buried high-frequency targets while signals due to saline soil are substantially rejected from the output signal.

A method for improving a metal detector, including: processing at least one receive signal due to a receive magnetic field using at least two functions to produce two processed signals, the at least two functions are selected such that the first processed signal is more sensitive to deeply buried targets than the second processed signal; and the second processed signal is more sensitive to shallow-buried conductive objects with characteristic frequency greater than 100 kHz than the first processed signal but not sensitive to saline soil, and that the two processed signals substantially complement each other in terms of sensitivity to targets in terms of target frequency and detection depth; and processing the two processed signals to produce at least one output signal which is sensitive to deeply buried low-frequency targets, shallow-buried low-frequency targets and shallow-buried high-frequency targets while signals due to saline soil are substantially rejected from the output signal.

A shale oil analysis method and apparatus for continuously characterizing saturation of adsorbed oil and free oil, comprising: obtain NMR T2 spectrum, NMR porosity, oil saturation and wettability indexes of a core samples, determine a lower limit value for the saturation calculation of the absorbed oil based on the NMR T2 spectrum, the NMR porosity, the oil saturation and wettability indices; determining a lower limit value for the saturation calculation of the free oil according to the bulk relaxation T.sub.2 spectrum of the crude oil of the well interval or an adjacent well interval and the NMR T.sub.2 spectrum of the core samples; calculating the saturation of the absorbed oil and the free oil, and analyzing the shale oil in the well interval to be analyzed. The solution realizes the quantitative and continuous characterization of the adsorbed oil and the free oil of the shale oil via well logs.