Study And Implementation Of Pulse Sequences For NMR Well Logging

In NMR well logging, magnetic field and stimulus pulse are principal conditions for the generation of this phenomenon and excitation of the echoes by formation fluids. The type of the parameters to be measured and their dimension are decided by the type of pulse sequences directly. and it demarcates the observation mode and velocity of logging to a certain extent. The strictness in timing and phase concerns the quality of echo signals and inversion. Along with the development of NMR logging technology, a number of logging tools based on NMR technology appeared so far. However, in consequence of lacking uniform standards and versatility, the repeating design work of pulse programmer brings about additional time and technic consumption for the research and design of new instruments. To meet different requirements, a standardized and well configurable pulse programmer with well versatility need to be designed.The function of stimulus of pulses in NMR technology is analyzed in this dissertation. The principle of a number of traditional pulse sequences as well as some special types of pulse sequences which are proper for NMR logging using are illustrated. Based on the summary of commonness and the features of a variety of pulse sequences, the division method that is based on “three-window” is advanced for generation of pulse sequences. An overall logic design scheme of the universal pulse programmer is proposed. The pivotal modules and their operation mode are described in detail. The description of constraints for synthesis and simulation results for the sequences are illuminated. It is verified and implemented on a programmable logic device. Lastly, under laboratory conditions, the performance of the pulse programmer which is used in the one-dimensional NMR logging tool and two-dimensional NMR logging tool are appraised.The capability of the pulse programmer primarily for which to be easily configured to generates different pulse sequences can be verified from the simulation results. The well performance of the pulse programmer in different NMR logging tools can be verified from the results of the experiments, and the same with the actual capability of the pulse programmer to generate different pulse sequences. The well versatility and configurable capability of the pulse programmer are proved by all those test results.