5291137 Processing method and apparatus for processing spin echo in-phase and quadrature amplitudes from a pulsed nuclear magnetism tool and producing new output data to be recorded on an output record

Abstract

A nuclear magnetic resonance (NMR) logging system includes a NMR logging tool adapted to be disposed in a borehole and a processing system adapted to be disposed on the surface of the borehole, the logging tool including a microcomputer, the processing system including a computer; and a signal processing system in accordance with the present invention having a first part stored in the downhole microcomputer of the logging tool and a second part stored in the surface oriented computer of the processing system. In the downhole microcomputer, using the first part of the signal processing system, a plurality of signal plus noise amplitudes are produced from a set of measured spin echo data, and a plurality N w of the window sums I m ,m+1 are produced from the signal plus noise ampltudes, the window sums being transmitted uphole to the processing system. By producing the window sums, the first part of the signal processing system compresses and eliminates redundant information from the measured spin echo data. In the surface oriented processing system, using the second part of the signal processing system, the plurality N w of the window sums I m ,m+1 are used to generate new data which is ultimately recorded on a new output record medium. Spectral amplitudes {a l }, determined from the window sums, are used by the processing system to compute three log outputs and signal distributions presented as color maps. Three standard deviations are also computed. Log quality curves including signal phase and RMS noise are also computed.