The Principle And Application Of Down-hole NMR Fluid Analysis

Since the static pressure of the borehole mud column is greater than the formationpressure while drilling, the slurry is pressed into the permeation layer and the mudinvasion zone is formed. The invasion zone rinsed by mud filtrate is easily cause porositymeasurement error during the Cable and LWD measurement process. In order to reducepollution impact, the invasion zone sampling method to identify the formation fluid, thecollected sample need to be transport to the surface for analysis, there also existuncertainty in the transport process and a significant time lag. Down-hole NMR fluidanalysis, making real-time evaluation of strata penetrated pollution, samplinguncontaminated samples for NMR analysis, provides a new way to solve the aboveproblems. Research work of this paper is as follows:(1)Combined with the down-hole fluid analysis technology and the basic principle ofthe NMR logging, the measurement method of the down-hole NMR fluid analyzer isdesigned, and for different measurement parameters, different measurement pulses aredesigned.(2)Combined with the structural features of the NMR logging tool, this paperanalyzes the probe structure and instrumentation circuit structure of the down-hole NMRfluid analyzer, and designs the acquisition circuit part of the instrument.(3)The EMD filtering algorithm dealing with non-stationary signals is used in theNMR fluid analysis, and filtering processing on the echo data, the standard T2inversion ismade based on the filtering.The real-time down-hole fluid analysis techniques, are important for the productioncost and accuracy of the down-hole fluid analysis, the down-hole NMR fluid analyzer canobtain the various parameters of the formation fluid, the EMD filtering is introduced intothe fluid analysis, which is well on the echo data de-noising, the resulting T2inversion can make comprehensive explanation of the NMR parameters.