Methods and logging systems for performing nuclear magnetic resonance (NMR) logging in downhole operations are described. The methods include performing a scout logging acquisition operation using an NMR logging tool to determine NMR logging parameters of a formation interval, setting an NMR logging acquisition mode based on the NMR logging parameters from the scout logging acquisition operation, and performing an NMR data logging operation to determine properties of the formation interval based on the set NMR logging acquisition mode.

A system having an NMR measurement device make measurements on a region of investigation in which an NMR-active fluid has been injected. A source of the NMR-active fluid (e.g., methane) is provided, and the pressure of the region of investigation may be monitored. A sealing apparatus serves to isolate the region of investigation. A parameter is estimating using the obtained measurement. The parameter estimated may include the inter-granular porosity, intra-kerogen porosity, kerogen maturity, free gas volume, and/or adsorbed gas volume. A baseline measurement may be made prior to injecting the NMR-active fluid, and the region of investigation may be evacuated before injecting the NMR-active fluid. The obtained T2 distribution can be resolved and each peak attributed to different constituent sources of the signal. The system can be conveyed into a wellbore using a drillstring, a wireline, a slickline, or a coil tubing.

A distributed device and method for detecting groundwater based on nuclear magnetic resonance are provided. The device includes an excitation apparatus, multiple polarization apparatuses, an aerial reception apparatus, and a control apparatus. The aerial reception apparatus includes an array cooled coil sensor. For each of the multiple polarization apparatuses, a position analysis module determines, together with a second position analysis module of the polarization apparatus, a position of the array cooled coil sensor relative to a polarization coil in the polarization apparatus. A polarization transmitter in the polarization apparatus switches to a mode of waiting for output in a case that the array cooled coil sensor is in coverage of the polarization coil. The polarization transmitter in the polarization apparatus remains in a standby mode in a case that the array cooled coil sensor is beyond coverage of the polarization coil.

A pyrolysis system for evaluating a source rock sample from a subterranean reservoir and methods are described. The pyrolysis system includes a reactor vessel including a body with an open end, a cover attachable to the body, a heating system, a collector assembly. The body and the cover define a sealable chamber; a source rock sample holder sized to be received inside the sealable chamber; and a sensor system. The sensor system includes a direct sensor assembly associated with the source rock sample holder, sized to be received inside the sealable chamber, and operable to measure properties of the source rock sample in the source rock sample holder; and a pyrolysis products sensor assembly in fluid communication with the collector assembly of the reactor vessel.

Measurements of a core sample at scales of measurement that differ by multiple orders of magnitude can be used to calculate a value that fairly represents surface roughness of the core sample. This surface roughness value can be used to determine petrophysical properties of the subsurface formation from which the core sample was obtained. The measurements can be nuclear magnetic resonance (NMR) diffusion-relaxation and gas-adsorption measurements. Surface relaxivities at the different scales are determined from the measurements and a ratio those surface relaxivities can be used to calculate the surface roughness value.

Pressure coring where the core apparatus drills the core sample and seals the core sample at its native downhole pressure (e.g., several thousand psi) may be expanded to include nuclear magnetic resonance (NMR) imaging components to produce a pressurized NMR core holder that allows for NMR imaging of the core samples having been maintained in a downhole fluid saturation state. NMR imaging performed may include 1H and also 19F imaging depending on the chamber fluid used in the pressurized NMR core holder.

A method for determining pore size distribution of rocks is provided. Capillary pressure measurements on rock cores are analyzed to determine a pore size distribution, with smaller pores requiring greater capillary pressure to relinquish contained fluid. Large pores with rough surfaces introduce inaccuracies in determining the pore size distribution. Embodiments of the invention correct the rough surface induced inaccuracies by measuring the shift in NMR T2 distribution from full saturation to the current state of desaturation and subtracting the T2 contributions in the desaturated state that have smaller T2 values (i.e., smaller transverse relaxation time) than the smallest T2 values (i.e., shortest transverse relaxation time) in the saturated distribution.

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.

To separate porosity from surface roughness, length scales for pore size and surface roughness are identified. These length scales are determined from surface roughness measurements and confirmed via NMR pore body calculations and pore size capillary pressure measurements. A filter removes pore contribution to surface roughness measurements and delivers intrinsic surface roughness. Additional filters and methods determine the minimum magnification on which to base surface roughness calculation, based on size of the field of view and where measured surface roughness approaches intrinsic surface roughness as magnification increases but larger magnification increase sampling time and difficulty. Sample irregularities, such as saw marks, are also filtered out or determined to be too large to remove via filter and another area of measurement is located. With the pore corrected quantification of surface roughness, surface relaxivity and pore distribution can be calculated with greater accuracy.

Methods and systems are provided that employ a combination of dielectric dispersion measurement(s) and Nuclear Magnetic Resonance (NMR) measurement(s) to determine data that characterizes tortuosity of rock and data that characterizes tortuosity of fluid phases in the rock independently from one another. t,?