Technologies applicable to NMR spin-echo amplitude estimation are disclosed. Example methods may calibrate for distortion of a shape and estimated amplitude of measured NMR spin or gradient echoes. NMR spin or gradient echo measurements may be performed on a sample. The measured NMR spin or gradient echoes may be used to calculate an echo-shape calibration factor. The echo-shape calibration factor may estimate an effect of echo shape on estimated spin or gradient echo amplitude(s) of the NMR spin or gradient echoes. The echo-shape calibration factor may be used to correct for underestimation or overestimation of the spin or gradient echo amplitude(s).

Methods and systems for determining whether a base oil for use in drilling muds will be compatible with cement during subsequent cementing operations include: providing a drilling fluid that includes a base oil; using the drilling fluid to drill at least a portion of a wellbore penetrating at least a portion of a subterranean formation; measuring a compositional characteristic of the base oil using one or more analytical tests; determining whether the base oil is a compatible base oil or an incompatible base oil based at least in part on the compositional characteristic of the base oil; injecting an amount of spacer fluid into the wellbore, wherein the amount of spacer fluid is selected based on the determination of whether the base oil is a compatible base oil or an incompatible base oil; and injecting the one or more cementing or completion fluids into the wellbore.

Apparatus and methods for characterizing hydrocarbons in a subterranean formation include obtaining a sample of the subterranean formation; measuring, uphole, the porosity of the sample; using a nuclear magnetic resonance (NMR) tool downhole in the borehole, sending NMR pulse sequences configured for formation pore size and measuring NMR signals that characterize the formation at a location in the formation; analyzing the signals to find a gas porosity of the formation at the location; and determining a hydrogen index (HI.sub.g) of the subterranean formation from the gas porosity and from the porosity of the sample. The obtained HI.sub.g may then be used in conjunction with downhole NMR measurements to find corrected gas porosities at locations of the formation.

An NMR method and apparatus for analyzing a sample of interest applies a static magnetic field together with RF pulses of oscillating magnetic field across a sample volume that encompasses the sample of interest. The RF pulses are defined by a pulse sequence that includes a plurality of measurement segments configured to characterize a plurality of relaxation parameters related to relaxation of nuclear magnetization of the sample of interest. Signals induced by the RF pulses are detected in order to derive the relaxation parameters. The measurement segments of the pulse sequence include at least one first-type measurement segment configured to characterize relaxation of spin-lattice interaction between nuclei of the sample of interest in a rotating frame (T.sub.1ρ) at a predefined frequency. The T.sub.1ρ parameter can be measured in conjunction with the measurement of other relaxation and/or diffusion parameters as part of multidimensional NMR experiments.

A nuclear magnetic resonance (NMR) measurement, at two or more depths of investigation, of a subsurface formation containing formation water and a mud filtrate from a water-base mud is obtained, and the mud filtrate is distinguished from the formation water. A NMR logging tool is disposed in a wellbore penetrating the formation containing the mud filtrate and the formation water and NMR measurements at different radial depths of investigation into the formation are made. The mud filtrate is distinguished from the formation water by determining the relative salinities of the mud filtrate and the formation water. The relative salinities are determined by comparing distribution relaxation times across different depths of investigation or by comparing logarithmic mean values across different depths of investigation.

An apparatus for extracting a fluid from a formation includes an inflow control device (ICD) coupled to a production tubular disposed in a borehole penetrating the formation and configured to control flow into the production tubular and a nuclear magnetic resonance (NMR) front-end component assembly disposed in the borehole, the NMR front-end component assembly having a sensitive volume in a flow path leading to and/or coming through the ICD. The apparatus also includes a controller receiving input from an NMR electronics module coupled to the NMR front-end component assembly and providing output to the ICD based on the input from the NMR electronics module.

A mobile measuring apparatus for nondestructively determining a material measurement value that relates to a material property of a workpiece comprises a housing in which at least a first sensor device and a second sensor device are located, a control device, an evaluating device, and a device for the supply of energy to the measuring apparatus. The first sensor device has a nuclear magnetic resonance sensor and the second sensor device has a sensor based on dielectric and/or resistive methods. Information about the material property of the workpiece, in particular moisture present in the workpiece, is obtained by evaluating a measurement signal provided by the first sensor device, which information is intended for the optimized control of the second sensor device and/or optimized evaluation of measurement signals provided by the second sensor device.

A formation fluid sample is analyzed using NMR spectroscopy to obtain a NMR spectrum. The NMR spectrum is then analyzed to find evidence of the amount of olefins present in the sample. The amount of olefins present in the sample can then be correlated to the level of contamination of the sample. In one embodiment, a .sup.1H chemical shift of between substantially 4.5 and 6 ppm is used to identify olefins present in the sample. In another embodiment, a .sup.1H chemical shift of substantially 1.9 to 2.1 ppm is used to identify olefins present in the sample. The NMR spectral equipment can be located uphole or downhole.

An apparatus for NMR properties of subsurface formations includes a magnet, a transmitter antenna and at least one of a receiver section of the transmit antenna or a separate receiver antenna having a length along the longitudinal dimension of the apparatus which is shorter than a length of the transmitter antenna along the longitudinal dimension. The apparatus includes circuitry for applying radio frequency current pulses to the entire transmitter antenna and for receiving signals by the at least one of the receiver section of the transmitter antenna and the separate receiver antenna.

The present disclosure relates to a method that includes generating a first pulse at a first position along a geological formation with a plurality of antennae, wherein the first pulse comprises a Can-Purcell-Meiboom-Gill (CPMG) sequence, and wherein each antenna of the plurality of antennae is configured to generate NMR data via transmitting and receiving pulses into the geological formation.