Computer-controlled, portable pulsed NMR instrument and method of use wherein depolarization is ultrashortened using pseudo randomly spaced and oriented RF depolarization pulses

A method for swiftly determining fluid-flow properties of a rock sample based on nuclear magnetic resonance (NMR) response of hydrogen nuclei of interstitial fluids within said sample in which pseudo random depolarizing pulses must be introduced in order to increase data-throughput efficiency (DTE) comprising:

• (a) storing digital control codes associated with (i) a first and second series of RF magnetic pulses of selected frequency, duration and magnitude, and (ii) a plurality of time windows for detection of a plurality of NMR response signals;
• (b) placing the rock sample in a steady DC magnetic field having a strength of at least 1 kilogauss and an inhomogeneity of at least D gauss to aid in providing a series of nuclear magnetization build-ups associated with said interstitial fluids;
• (c) under control of said control codes, subjecting said sample to said first series of RF magnetic field pulses for interrogating said samples to cause reorientation of each of said series of built-up magnetizations and, after each magnetization build-up has occurred, subjecting said sample to said second series of pulses for depolarizing said sample, the magnitude of each of said series of pulses being greater than the variation D in strength in said DC field over said sample, said second series of pulses being both pseudo random in time and pseudo randomly oriented in space about said sample;
• and
• (d) automatically detecting after interrogation, but before depolarization, in accordance with said control codes, said plurality of nuclear magnetic resonance (NMR) signals indicative of nuclear magnetization relaxation, each of said NMR signals occurring between said secessive pulses of said first series of RF field pulses intermixed with a single depolarizing period.

A method for swiftly determining fluid-flow properties based on NMR response of hydrogen nuclei of interstitial fluid within rock samples, which properties may include porosity, permeability, recoverable fluid content, large-pore specific surface, argillaceous specific surface, or any combination or subcombination of these properties, in which pseudo random depolarizing pulses must be used in order to increase data-throughput efficiency (DTE), of a measuring system comprising:

• (a) storing at least an interrogating, a depolarizing and a detection control code associated with (i) a first and second series of RF magnetic pulses, respectively, of selected frequency duration and magnitude, and (ii) a plurality of time windows for detection of a plurality of NMR response signals;
• (b) placing the rock sample in a steady DC magnetic field having a strength of at least 1 kilogauss and an inhomogeneity of about D gauss to aid in providing a series of nuclear magnetizations build-ups associated with said interstitial fluid within said rock sample, said each nuclear magnetization having a preferential alignment parallel to said DC magnetic field;
• (c) subjecting said sample on a sequential basis to said first series of RF magnetic pulses for interrogating said sample to cause reorientation of said magnetization to preferred alignments offset from said DC field, and after magnetization build-up has occurred, subjecting said sample to said second series of pulses for depolarizing said sample, said amplitude of said series of pulses being greater than the variation D in strength of said DC field over the sample, said second series of pulses being pseudo randomly spaced in time and pseudo randomly oriented in space about said sample;
• (d) automatically detecting after interrogation, but before depolarization, in accordance with said detection code, NMR responses associated with precession of said magnetization build-ups about axes substantially parallel of said DC field magnetic field within said plurality of time windows, each of said windows occurring within an interval between two of said interrogation pulses and a single depolarizing period and within subintervals beginning at a fixed delayed time after cessation of each of said interrogation pulses;
• and
• (e) automatically repeating steps (c) through (d) whereby a different predetermined average repetition rate for said interrogation pulses is associated with a constant depolarizing period to obtain at least a second statistically-improved signal representing nuclear magnetization relaxation in said DC magnetic field within at least a different average time interval between said interrogation pulses, whereby flow properties of said sample can be quickly indicated.