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 wireless communications system for a downhole drilling operation comprises surface communications equipment and a downhole telemetry tool. The surface communications equipment comprises a surface EM communications module with an EM downlink transmitter configured to transmit an EM downlink transmission at a frequency between 0.01 Hz and 0.1 Hz. The downhole telemetry tool is mountable to a drill string and has a downhole electromagnetic (EM) communications unit with an EM downlink receiver configured to receive the EM downlink transmission. The downhole EM communications unit can further comprise an EM uplink transmitter configured to transmit an EM uplink transmission at a frequency greater than 0.5 Hz, in which case the surface EM communications module further comprises an EM uplink receiver configured to receive the EM uplink transmission. More particularly, the downhole EM uplink transmitter can be configured to transmit the EM uplink transmission at a frequency that is at least ten times higher than the EM downlink transmission frequency.

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 electromagnetic (EM) telemetry method comprises encoding downhole data into a single data stream; separating the single data stream into a plurality of separate data streams; converting each separate data stream into a corresponding separate waveform using a selected digital modulation technique wherein at least one of the frequency and phase of each waveform is assigned a unique value or unique non-overlapping range of values; combining each separate waveform into a combined waveform; and transmitting from a downhole location, an electromagnetic (EM) telemetry carrier wave comprising the combined waveform.

In one aspect, a resistivity logging tool for a fluid-producing formation if provided. The resistivity logging tool includes at least one transmitter device connected to at least one excitation electrode, multiple receiver devices respectively connected to monitoring electrodes, and a controller. The transmitter can inject an excitation current into the formation via the excitation electrode. Each receiver device can determine a respective voltage level induced by the excitation current. The controller can determine whether a voltage level measured by at least one receiver device is within a specified range. Based on the measured voltage level, the controller can select a global amplitude adjustment algorithm for modifying excitation currents or a localized amplitude adjustment algorithm for modifying one or more gains of one or more receiver devices. The controller can modify the excitation current or gains by executing the selected algorithm.

Apparatus and associated methods may relate to a sensor controller configured to apply predetermined criteria to determine when a parameter value sampled by a sensor module meets the predetermined criteria, and in response to making such a determination, adjust a commanded data rate including an update time period. In an illustrative example, the predetermined criteria may be independently defined for each sensor in a network. In examples with a network of sensors, the sensor controller may dictate sensor module operation at differentiated data rates. In an illustrative example, a sensor controller may communicate with a series of pressure level sensor modules connected to a drilling apparatus in a mud logging application. Upon detection of a pressure level change that exceeds a critical condition as determined through comparison with the predetermined criteria, the sensor controller may increase or decrease a data rate of the respective sensor module, for example.

A method for homogenizing the static magnetic field with a distribution B0(r) in the active volume of a magnetic resonance apparatus having a number N of shim coils defines a target field distribution B0T(r) using a filter method in which a norm of the shim currents is influenced by means of filter factors. An optimization procedure works in a parameter space having M control parameters, wherein 2≤M<N. One of the control parameters is used as a weighting parameter for modification of a spatial weighting function and another control parameter is used to control the filter factors. Using this method the hardware limitations can be taken into account when determining the target field distribution, without a significant increase in the computational effort to determine the target field distribution during optimization.

A scaling unit (1) for reception antennae (A1, A2, A3, A4) of a plurality of local coils (LS) of a magnetic resonance imaging scanner (MRT) includes a plurality of signal inputs (in1, in2, in3, in4) configured for the reception of signals from the reception antennae (A1, A2, A3, A4), and a plurality of signal outputs (out1, out2, out3, out4) configured for the output of unaltered and/or altered signals from the reception antennae (A1, A2, A3, A4).

A cassette mounting detection apparatus may include a cassette mounting unit configured to include a plurality of slots on which a plurality of cassettes is mounted and the mounting detection circuits of the respective slots and a main control unit configured to include a plurality of signal output terminals and a plurality of voltage detection terminals and to detect that at least one of the plurality of cassettes is mounted on any of the plurality of slots based on an output signal output through at least one of the plurality of signal output terminals and cassette voltages detected through at least one of the plurality of voltage detection terminals.

A cassette mounting detection apparatus may include a cassette mounting unit configured to include a plurality of slots on which a plurality of cassettes is mounted and the mounting detection circuits of the respective slots and a main control unit configured to include a plurality of signal output terminals and a plurality of voltage detection terminals and to detect that at least one of the plurality of cassettes is mounted on any of the plurality of slots based on an output signal output through at least one of the plurality of signal output terminals and cassette voltages detected through at least one of the plurality of voltage detection terminals.