초록 ▼

In accordance with the present invention, fluid-flow properties of a rock sample based on NMR response of the hydrogen nuclei of interstitial fluids within the pore space of such sample, can be swiftly and accurately achieved using a computer-controlled, portable NMR instrument. Inherent instrument

In accordance with the present invention, fluid-flow properties of a rock sample based on NMR response of the hydrogen nuclei of interstitial fluids within the pore space of such sample, can be swiftly and accurately achieved using a computer-controlled, portable NMR instrument. Inherent instrument inadequacy of a DC field inhomogeneity is controllably augmented by a depolarizing code (provided via a computer-controller controlling a transmitter-pulser) to ensure complete magnetic memory erasing prior to a new measuring cycle. Result: Even though the instrument is placed at field sites away from the usual processing center, quick analysis of rock samples as during the drilling of a well, results.

대표청구항 ▼

1. Automatic apparatus for swiftly determining fluid-flow properties of a rock sample based on NMR response of hydrogen nuclei of interstitial fluids within pore spaces of said sample in which pseudo random depolarizing pulses must be introduced to increase data-throughput efficiency (DTE) comprisin

1. Automatic apparatus for swiftly determining fluid-flow properties of a rock sample based on NMR response of hydrogen nuclei of interstitial fluids within pore spaces of said sample in which pseudo random depolarizing pulses must be introduced to increase data-throughput efficiency (DTE) comprising: (a) magnet means for producing a DC magnetic field acting on said rock sample, said magnetic field having an intensity 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 within said sample as a function of time; (b) RF coil means acting at right angles to said DC magnetic field; (c) transmitter means including digital control means for generating a first and a second control code associated with a series of RF magnetic pulses of selected frequency, amplitude and duration, connected to said RF coil means, said first control code controlling the production of said RF magnetic pulses for interrogating said sample, said second control code controlling the depolarizing of the said sample via a series of pseudo randomly spaced and oriented RF depolarizing pulses, said amplitude of each interrogating and depolarizing pulse being controlled to be at least greater than the variation D in said DC field over of said sample; (d) receiver means connected to said digital control means and to said RF coil means for generating via a third control code associated with a plurality of time windows, output signals proportional to said nuclear magnetic resonance response of said interstitial fluids; (e) said transmitter means including said digital control means providing via said depolarizing code an extremely short depolarizing period, so that said sample can be repetitively interrogated to serially indicate nuclear magnetization relaxation. 2. The apparatus of claim 1 in which the control means of said transmitter means includes storage means, said second depolarizing control code being stored at said storage means on a sequential basis as control words each having informational fields previously generated via pseudo random numbers for determining both (i) next-in-time quiescent interval values, and (ii) orientation of the next-in-time depolarizing pulse whereby the magnetic moments of said nuclei of said sample are depolarized within a surprisingly short depolarizing period. 3. Apparatus of claim 2 in which the depolarizing period is in a range of 15-25 milliseconds. 4. The apparatus of claim 1 wherein said receiver means is connected in series with an integrator circuit and wherein said third control code, normalize said NMR responses over a plurality of said time windows to attain first and second statistically-improved signals representing magnetization relaxations for different sets of time intervals between interrogation pulses. 5. The apparatus of claim 4 wherein said integrator circuit integrates said NMR responses in accordance with said third control code over each of said plurality of time windows to obtain at least an improved signal representing the normalized nuclear magnetization relaxation in said DC magnetic field between application of said RF magnetic interrogation pulses. 6. The apparatus of claim 1 wherein the inhomogeneity of the DC magnetic means aids in preventing refocusing of prior generated NMR signals during subsequent magnetization build-ups, especially at long polarizing periods. 7. 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. 8. 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. 9. Method of claim 8 in which step (e) involving repeating steps (c)-(d) is followed by the step of analyzing relative rates of magnetization relaxation as a function of time to thereby indicate fluid-flow properties of said sample. 10. The method of claim 8 in which said depolarizing code is stored on a sequential basis as control words each having informational fields previously generated via pseudo random numbers for determining both (i) next-in-time quiescent interval values, and (ii) orientation of the next-in-time depolarizing pulse of said depolarizing code whereby the magnetic moments of said nuclei of said sample are depolarized within a surprisingly short depolarizing period. 11. The method of claim 10 in which the polarizing period generated by said depolarizing code is in a range of 15-25 milliseconds.