METHOD OF NUCLEAR MAGNETIC VOLTAGE AND A DEVICE FOR ITS IMPLEMENTATION Russian patent published in 2019 - IPC G01V3/14 G01R33/44 

FIELD: physics.

SUBSTANCE: using for nuclear magnetic well logging. Core of the invention is that before the start of the action of the pulse sequence the difference of currents is set in the magnetizing coils while maintaining the total value, so that the study area, namely, the zone in which the conditions of nuclear magnetic resonance are fulfilled is axially displaced relative to a plane passing through the center of the gap between the magnets perpendicular to the axis of the magnets, in the direction of movement of the device by the ∆Zo value, equal to half the product of the specified logging speed V and time T of the CPMG pulse sequence, then, during the time of the pulse sequence, the value of the difference of currents in the coils changes linearly with such a rate that by the end of the pulse sequence action the research zone is axially displaced relative to the plane passing through the specified geometric center of the magnetic system, in the direction opposite to the direction of movement of the device by ∆Zo value, synchronously with the beginning of the next cycle of the pulse sequence of radio-frequency pulses, the sequence of actions the control of currents in the coils is repeated with a period equal to the specified period of the pulse sequences, while the initial and final values of the current, as well as the direction and rate of change of current in the coils in the linear dependency section, are determined based on the requirement of immutability, during the entire duration of the pulse sequence of coordinates of the investigated area relative to the well itself, taking into account the specified values of the logging speed V and the duration of the pulse sequence T, and the total value of the current in the bias coils, providing compensation for the temperature dependence of the magnetic induction of permanent magnets, during the data acquisition process, they are kept constant or changed asynchronously with respect to the pulse sequence, based on data such as telemetry.

EFFECT: providing the ability to compensate for the effect of the speed of movement of a nuclear magnetic logging device along the wellbore on the recorded relaxation time spectra and to ensure the possibility of expanding the range of logging speeds while maintaining the ability of regulation in the logging process, the values of the focused magnetic field in the study area, as well as to ensure the possibility of compensating for the temperature dependence of the residual induction of permanent magnets without degrading the characteristics of the depth of the study.

2 cl, 3 dwg