A nuclear magnetic resonance apparatus for estimating properties of an earth formation includes a carrier configured to be deployed in a borehole in the earth formation and at least one transmitting assembly disposed in the carrier and configured to generate an oscillating magnetic field in a volume of interest within the earth formation. The apparatus also includes at least one receiving assembly disposed in the carrier and configured to detect a nuclear magnetic resonance (NMR) signal originating in the volume of interest. In this apparatus, the receiving assembly includes at least a first longitudinal region with a loop coil and a butterfly coil, the loop coil central axis being located over a region of the magnet assembly where a static magnetic field is predominantly along an azimuthal direction to the carrier and the butterfly coil being at least partially overlapped with the loop coil to reduce mutual coupling.

Downhole fluid volumes of a geological formation may be estimated using nuclear magnetic resonance (NMR) measurements, even in organic shale reservoirs. Multi-dimensional NMR measurements, such as two-dimensional NMR measurements and/or, in some cases, one or more well-logging measurements relating to total organic carbon may be used to estimate downhole fluid volumes of hydrocarbons such as bitumen, light hydrocarbon, kerogen, and/or water. Having identified the fluid volumes in this manner or any other suitable manner from the NMR measurements, a reservoir producibility index (RPI) may be generated. The downhole fluid volumes and/or the RPI may be output on a well log to enable an operator to make operational and strategic decisions for well production.

Downhole fluid volumes of a geological formation may be estimated using nuclear magnetic resonance (NMR) measurements, even in organic shale reservoirs. Multi-dimensional NMR measurements, such as two-dimensional NMR measurements and/or, in some cases, one or more well-logging measurements relating to total organic carbon may be used to estimate downhole fluid volumes of hydrocarbons such as bitumen, light hydrocarbon, kerogen, and/or water. Having identified the fluid volumes in this manner or any other suitable manner from the NMR measurements, a reservoir producibility index (RPI) may be generated. The downhole fluid volumes and/or the RPI may be output on a well log to enable an operator to make operational and strategic decisions for well production.

An NMR well logging tool is provided that includes a sensor and associated electronic circuitry. The sensor includes an array of RF antenna elements. The electronic circuitry includes at least one low-power integrated circuit and a plurality of high-power modules corresponding the RF antenna elements of the array. Each high-power module is coupled to a corresponding RF antenna element of the array and includes an RF amplifier that is configured to amplify RF pulses generated by the at least one low-power integrated circuit and supplied thereto for transmission by the corresponding antenna element. In embodiments, the RF amplifier of each high-power module can include an H-bridge circuit or other suitable RF amplifier.

An NMR well logging tool is provided that includes a sensor and associated electronic circuitry. The sensor includes an array of RF antenna elements. The electronic circuitry includes at least one low-power integrated circuit and a plurality of high-power modules corresponding the RF antenna elements of the array. Each high-power module is coupled to a corresponding RF antenna element of the array and includes an RF amplifier that is configured to amplify RF pulses generated by the at least one low-power integrated circuit and supplied thereto for transmission by the corresponding antenna element. In embodiments, the RF amplifier of each high-power module can include an H-bridge circuit or other suitable RF amplifier.

A method is provided for automatically classifying grains, pores, or both of a formation sample. The method includes receiving a digital image representation of the formation sample, and identifying a plurality of pores, grains, or both in the digital image representation. The method also includes computing a plurality of geometric features associated with the pores, grains, or both in the digital image representation, and inputting the geometric features into an unsupervised machine learning model. The unsupervised machine learning model determines a label for each identified pore and grain, the label being a pore-type or a grain-type, and the plurality of geometric features and the labels determined for each pore, grain, or both, are input into a supervised machine learning model. The supervised machine learning model determines a final classification of a pore-type for each pore and a grain-type for each grain in the digital image representation of the formation sample.

A method and device for detection of solid organic matter and fluids in a shale rock by means of low field Nuclear Magnetic Resonance (NMR) in a single measurement, by submitting a rock sample to a 2D NMR assay comprising applying a 2D pulse sequence with a saturation-recovery, or inversion-recovery, in an indirect dimension and an FID-CPMG in a direct dimension. The method can be used as an analytical technique for rock samples from unconventional hydrocarbon reservoirs.

A method and device for detection of solid organic matter and fluids in a shale rock by means of low field Nuclear Magnetic Resonance (NMR) in a single measurement, by submitting a rock sample to a 2D NMR assay comprising applying a 2D pulse sequence with a saturation-recovery, or inversion-recovery, in an indirect dimension and an FID-CPMG in a direct dimension. The method can be used as an analytical technique for rock samples from unconventional hydrocarbon reservoirs.

Provided in some embodiments are systems and methods for determining characteristics of a hydrocarbon reservoir. Embodiments include conducting a nuclear magnetic resonance (NMR) logging operation of a targeted reservoir section of a wellbore extending into a hydrocarbon reservoir to generate a NMR log of the targeted reservoir section, conducting a resistivity logging of the targeted reservoir section to generate an uninvaded water saturation (S.sub.w) log of the targeted reservoir section, determining for each of a plurality of depths in the section, a T.sub.2 cutoff point based on values of the NMR and S.sub.w logs, identifying a subset of the T.sub.2 cutoff points that exhibit a hyperbolic trend, determining a theoretical cutoff curve corresponding to the subset of the T.sub.2 cutoff points, determining a free water level (FWL) of the reservoir based on the theoretical cutoff curve, and determining a rock type of the reservoir based on the theoretical cutoff curve.

Provided in some embodiments are systems and methods for determining characteristics of a hydrocarbon reservoir. Embodiments include conducting a nuclear magnetic resonance (NMR) logging operation of a targeted reservoir section of a wellbore extending into a hydrocarbon reservoir to generate a NMR log of the targeted reservoir section, conducting a resistivity logging of the targeted reservoir section to generate an uninvaded water saturation (S.sub.w) log of the targeted reservoir section, determining for each of a plurality of depths in the section, a T.sub.2 cutoff point based on values of the NMR and S.sub.w logs, identifying a subset of the T.sub.2 cutoff points that exhibit a hyperbolic trend, determining a theoretical cutoff curve corresponding to the subset of the T.sub.2 cutoff points, determining a free water level (FWL) of the reservoir based on the theoretical cutoff curve, and determining a rock type of the reservoir based on the theoretical cutoff curve.