A nuclear magnetic resonance (NMR) sensor and methods and systems for use are provided. The method comprises disposing a nuclear magnetic resonance (NMR) sensor into a borehole, the NMR sensor comprising a magnet assembly to create a static magnetic field and a first transversal-dipole antenna having an azimuthally selective response function. The method further comprises, while rotating the NMR sensor, initiating azimuthally selective NMR excitation in at least one sensitivity region at a first frequency using the first transversal-dipole antenna and the magnet assembly, wherein the at least one sensitivity region is determined by the static magnetic field and the RF magnetic field. The method then comprises acquiring one or more azimuthally selective NMR signals at the first frequency using the first transversal-dipole antenna.

A method of incorporating the influence of diffusion into the CPMG-based T2 measurement for one or more of the following: water cut measurement; performing inline measurements of flow rate; density; and rheology of a flowing fluid. The method includes conducting a “standard T1/T2 experiment” at least twice by providing one scan without a field gradient during the CMPG echo train. Then, providing a second scan with the application of a gradient, where in the second experiment the measured T2 (T2.sub.app) is affected solely by water diffusion, thus shifting cross peaks which represent water on the first T1/T2 spectrum to lower T2 values on the second spectrum.

A fracture geometry mapping method includes determining a value of a diffusive tortuosity in a first direction in a first rock sample from a subterranean formation with one or more hardware processors; determining a value of a diffusive tortuosity in a second direction in the first rock sample from the subterranean formation with the one or more hardware processors, the second direction orthogonal to the first direction in the first rock sample; determining a value of a diffusive tortuosity in third direction in the first rock sample from the subterranean formation with the one or more hardware processors, the third direction orthogonal to both the first direction and the second direction in the first rock sample; comparing the values of the diffusive tortuosities in the in the first direction, the second direction, and the third direction; and based on the comparison, generating a first fracture network map of the subterranean formation, the first fracture network map including a first plurality of anisotropic fracture pathways.

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.

A method for predicting formation permeability by measuring diffusional tortuosity in several directions by pulse gradient NMR. The method comprises evaluating an anisotropic diffusion coefficient by pulsed gradient NMR, determining diffusional tortuosity from the restricted diffusion data, supplementing the NMR results with resistivity and sonic logging data, measuring anisotropic tortuosity and porosity by resistivity and sonic data and combining all components in a single fitting model. The 11-coefficient model is trained to recognize the true values of permeability by comparing the real oil permeabilities measured in a library of oil-carrying rock cores with the NMR, resistivity and sonic correlates. The fitting coefficients are extracted by minimizing the discrepancy between the laboratory measured permeabilities and the predicted values combining all rapid logging information components with the agreement-maximizing weights.

A method of measuring petrophysical information from a crushed porous media including performing one or more NMR measurements on the porous media fully submerged in an NMR visible fluid, performing one or more NMR measurements on the porous media alone following centrifugation, performing one or more NMR measurements on the porous media after rinsing with a NMR invisible fluid, and analyzing the NMR measurements to extract a petrophysical property.

An electromagnet model or models are created to generate the static and radio frequency magnetic fields of an NMR downhole logging tool. The magnetic field distributions are then used in spin dynamics (SD) simulations to model the impacts of various effects on NMR logging data, effects that cannot be accurately describe by theoretical formulation alone. The accuracy of the electromagnetic model and the SD simulation may be verified against experimental observations or trial logging runs. Simulation of electronic circuit, molecular diffusion, tool motion can all be incorporated in the SD simulation. The NMR data inversion process can be modified according to echoes obtained from SD simulation to obtain more accurate petrophysical parameters.

An apparatus for performing a downhole nuclear magnetic resonance (NMR) experiment on a subsurface material in a volume of interest includes: a carrier configured to be conveyed through a borehole penetrating the subsurface material; an NMR sensor assembly disposed on the carrier and comprising a static magnetic field source configured to polarize nuclei of the subsurface material in the volume of interest and an antenna configured to receive NMR signals; and a receiver circuit disposed on the NMR sensor assembly and configured to process received NMR signals to perform the downhole NMR experiment; wherein (i) the receiver circuit is disposed in a pressure-excluding enclosure and (ii) the antenna, the static magnetic field source, and the pressure-excluding enclosure are disposed in a pressure-balancing fluid that is at least partially enclosed by an enclosure of non-metallic material.

A method for predicting formation permeability by measuring diffusional tortuosity in several directions by pulse gradient NMR. The method comprises evaluating an anisotropic diffusion coefficient by pulsed gradient NMR, determining diffusional tortuosity from the restricted diffusion data, supplementing the NMR results with resistivity and sonic logging data, measuring anisotropic tortuosity and porosity by resistivity and sonic data and combining all components in a single fitting model. The 11-coefficient model is trained to recognize the true values of permeability by comparing the real oil permeabilities measured in a library of oil-carrying rock cores with the NMR, resistivity and sonic correlates. The fitting coefficients are extracted by minimizing the discrepancy between the laboratory measured permeabilities and the predicted values combining all rapid logging information components with the agreement-maximizing weights.

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.